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Aboveground vegetation restoration shapes the soil microbial community structure and affects microbial resource acquisition. However, the changes in soil microbial resource limitation in subsoil during vegetation restoration are still unclear. In this study, the microbial community structure and resource limitation in an alpine meadow soil profile that had undergone natural restoration for short-term (4-year) and long-term (10-year) restoration in response to vegetation restoration were explored through high-throughput sequencing analysis and extracellular enzyme stoichiometry (EES). There was no significant difference in microbial composition and α diversity between short- and long-term restoration soils. Soil microorganisms in this alpine meadow were mainly limited by phosphorus. Carbon limitation of soil microorganisms was significantly decreased in each layer (0–15, 15–30, 30–45, 45–60, and 60–80 cm corresponding to L1, L2, L3, L4, and L5, respectively) of long-term restoration soils when compared to that of the short-term restoration soil layers, while phosphorus limitation of microorganisms in subsoil (60–80 cm) was significantly increased by 17.38%. Soil nutrients, pH, moisture content, and microbial composition are the main drivers of microbial resource limitation in restoration, and their effects on microbial resource limitation were different in short- and long-term restoration. Meanwhile, key microbial taxa have a significant impact on microbial resource limitation, especially in short-term restoration soils. This study suggested that vegetation restoration significantly affected soil microbial resource limitation, and could alleviate microbial resource limitations by adding nutrients, thus accelerating the process of vegetation restoration in alpine ecosystems. • Soil depth influenced the response of microbial resource limitation to restoration. • Key microbial taxa affected microbial resource limitation. • Long-term restoration significantly reduced carbon limitation in each soil layer. • Phosphorus limitation was significantly increased by 17.38% in subsoil (60–80 cm). [ABSTRACT FROM AUTHOR]

We investigated factors leading to variation in social complexity or 'social systems' among plateau pika family groups within a contiguous local population across 2 years. Plateau pikas are small, diurnal, nonhibernating, sexually monomorphic lagomorphs that occupy family home ranges on open alpine meadows on the Qinghai-Tibetan Plateau. Expression of the social organization, social structure, mating system and parental care system in plateau pikas did not follow expectations from traditional ecological or evolutionary explanations. Variability in plateau pika family group size and the transitions of group size between years allowed us to investigate potential advantages and disadvantages of group living. Evidence that group living served to protect pikas against predation was weak. Although social huddling could have minimized thermoregulatory costs during the extremely cold Tibetan winters, there was no correlation of overwinter survivorship among pika families of different sizes. There was no apparent group-living benefit with regard to foraging, and the occurrence of cohesive social families on the flat, continuous meadow contradicts the hypothesis that sociality is related to patchiness of critical resources. Cost of maintaining burrows appeared unrelated to group size. Most interactions between pikas occurred within family groups and were affiliative (99% of adult interactions; 97% of adult–juvenile interactions), and most interactions between adult males of different family groups were aggressive (96% of interactions). Matings were primarily within families (88% of copulations). Pikas also possess a complex vocal repertoire that enhanced interactions within social families. Demographic constraints associated with variable overwinter survivorship appeared to be the dominant precondition that produced a given family size and mating system type, coupled with selective dispersal by some pikas before the start of the breeding season. Paternal care enhanced juvenile survival, and thus led to an equalization of reproductive success among adults in families with different mating combinations. • Plateau pikas live in families occupying exclusive burrow systems and home ranges. • Pika family group size varied from one to five adults within and between years. • Pikas failed to adhere to conventional explanations for establishment of group size. • Pika families exhibited multiple social mating system types. • Pika families did not adhere to explanations for establishment of mating system types. [ABSTRACT FROM AUTHOR]

Coastal wetlands are known for their diverse ecosystems, yet their soil characteristics are often misunderstood and thought to be monotonous. These soils are frequently subjected to saline water saturation, leading to unique soil processes. However, the combination and intensity of these processes can vary considerably across different ecosystems. In this study, we hypothesize that these diverse soil processes not only govern the geochemical conditions in coastal ecosystems but also influence their ability to deliver ecosystem services. To test this hypothesis, we conducted soil analyses in mangroves, seagrass meadows, and hypersaline tidal flats along the Brazilian coast. We used key soil properties as indicators of soil processes and developed a conceptual model linking soil processes and soil-related ecosystem services in these environments. Under more anoxic conditions, the intense soil organic matter accumulation and sulfidization processes in mangroves evidence their significance in terms of climate regulation through organic carbon sequestration and contaminants immobilization. Similarly, pronounced sulfidization in seagrasses underscores their ability to immobilize contaminants. In contrast, hypersaline tidal flats soils exhibit increased intensities of salinization and calcification processes, leading to a high capacity for accumulating inorganic carbon as secondary carbonates (CaCO 3), underscoring their role in climate regulation through inorganic carbon sequestration. Our findings show that contrary to previously thought coastal wetlands are far from monotonous, exhibiting significant variations in the types and intensities of soil processes, which in turn influence their capacity to deliver ecosystem services. This understanding is pivotal for guiding effective management strategies to enhance ecosystem services in coastal wetlands. [Display omitted] • Diverse soil processes combinations and intensities differentiate coastal wetlands. • Soils processes in coastal wetlands respond for the provision of ecosystem services. • C sequestration and contaminants immobilization are directly linked to soil processes. • Different coastal wetlands show contrasting abilities to provide ecosystem services. [ABSTRACT FROM AUTHOR]

Aboveground biomass (AGB) in grasslands directly reflects the net primary productivity, making it a sensitive indicator of grassland resource quality and ecological degradation. Accurately estimating AGB over large regions to reveal long-term AGB evolution trends remains a formidable challenge. In this study, we divided Inner Mongolia Autonomous Region (IMAR) grasslands into three study regions based on their spatial distribution of grassland types. We combined remote sensing data with ground-based sample data collected over the past 19 years from 6114 field plots using the Google Earth Engine platform. We constructed random forest (RF) and traditional regression AGB inversion models for each region and selected the best-performing model through accuracy assessment to estimate IMAR grassland AGB for the period 2000–2022. We also examined the trends in AGB changes and identified the driving forces affecting IMAR grasslands through the application of Theil-Sen estimation, Mann-Kendall trend analysis, and the Geodetector model. The main findings are as follows: (1) Compared with the univariate parametric traditional regression model, the AGB monitoring accuracy of the multivariate non-parametric RF model in the three study regions increased by 5.94%, 5.08% and 19.14%, respectively. (2) The average AGB per unit area of IMAR grasslands from 2000 to 2022 was 731.41 kg/hm2, with alpine meadow having the highest average AGB (1271.70 kg/hm2) and temperate grassland desertification having the lowest (469.06 kg/hm2). IMAR grasslands exhibited an overall increasing trend in AGB over the past 23 years (6.01 kg/hm2•yr), with the increasing trend covering 83.52% of the grassland area and the decreasing trend covering 16.48%. (3) Spatially, IMAR grassland AGB showed a gradual decline from northeast to southwest and exhibited an increasing trend with increasing longitude (45.423 kg/hm2 per degree) and latitude (71.9 kg/hm2 per degree). (4) Meteorological factors were the most significant factors affecting IMAR grassland AGB, with precipitation (five-year average q value of 0.61) being the most prominent. In the western part of IMAR, where precipitation is consistently limited throughout the year, the primary drivers of influence were human activities, with particular emphasis on the number of livestock (with a five-year average q value of 0.44). It is evident that reducing human activity disturbance and pressure in fragile grassland areas or implementing near-natural restoration measures will be beneficial for the sustainable development of grassland ecosystems. The results of this research hold substantial reference importance for the protection and restoration of grasslands, the supervision and administration of grassland resources, as well as the development of policies related to grassland management. [Display omitted] • The aboveground biomass (AGB) of grasslands in IMAR increased over the past 23 years. • IMAR grassland AGB shows an upward trend with increasing longitude and latitude. • Precipitation is the main factor affecting grassland AGB in IMAR. • Human activities have a greater impact on the grassland AGB in western IMAR. [ABSTRACT FROM AUTHOR]

Alpine meadows constitute one of the major ecosystems on the Qinghai-Tibetan Plateau, with livestock grazing exerting a considerable impact on their biodiversity. However, the degree to which plant diversity influences community stability under different grazing intensities remains unclear in this region. This study conducted controlled grazing experiments across four levels of grazing intensity (no-, low-, medium-, and high-grazing) based on herbage utilization rate to assess the influence of grazing intensities on plant community structure and diversity-stability relationships. We discovered that high-grazing reduced plant diversity and attenuated the temporal stability and resistance of above-ground biomass. No- and low-grazing could alleviate plant biomass loss, with community resistance being optimal under low-grazing. The direct effects of livestock grazing on temporal stability were found to be negligible. Plant characteristics and diversity accounted for a substantial proportion of livestock grazing effects on community resistance (R 2 = 0.46), as revealed by piecewise structural equation model analysis. The presence of plant diversity enhances the resistance of alpine meadows against disturbance and accelerates the recovery after grazing. Our results suggest that low-grazing intensity may represent a judicious option for preserving species diversity and community stability on the Qinghai-Tibetan Plateau. • Lower grazing intensity can mitigate biomass loss and optimize resistance. • Warm-season grazing maintains or increases plant height, biomass, and diversity. • Grazing-induced changes in plant community structure determine resistance. • Grazing indirectly affects intra-annual temporal stability via plant diversity. [ABSTRACT FROM AUTHOR]

Wet meadows, a type of wetland, are vulnerable to climate change and human activity, impacting soil properties and microorganisms that are crucial to the ecosystem processes of wet meadows. To decipher the ecological mechanisms and processes involved in wet meadows, it is necessary to examine the bacterial communities associated with plant roots. To gain valuable insight into the microbial dynamics of alpine wet meadows, we used Illumina MiSeq sequencing to investigate how environmental factors shape the bacterial communities thriving in the rhizosphere and rhizoplane of three plant species: Cremanthodium ellisii , Caltha scaposa , and Cremanthodium lineare. The most abundant bacterial phyla in rhizosphere and rhizoplane were Proteobacteria > Firmicutes > Actinobacteria, while Macrococcus , Lactococcus , and Exiguobacterium were the most abundant bacterial genera between rhizosphere and rhizoplane. The mantel test, network, and structure equation models revealed that bacterial communities of rhizosphere were shaped by total nitrogen (TN), soil water content (SWC), soil organic carbon (SOC), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), pH, however, rhizoplane bacterial communities exhibited varying results. The bacterial communities exhibited significant heterogeneity, with stochastic process predominating in both the rhizosphere and rhizoplane. PICRUSt2 and FAPROTAX analysis revealed substantial differences in key biogeochemical cycles and metabolic functional predictions. It was concluded that root compartments significantly influenced the bacterial communities, although plant species and elevation asserted varying effects. This study portrays how physicochemical properties, plant species, and elevations can shift the overall structure and functional repertoire of bacterial communities in alpine wet meadows. [Display omitted] • Bacterial communities of rhizosphere and rhizoplane differed in plants, and sites. • Stochastic processes predominated in both rhizosphere, and rhizoplane. • SOC, TN, SWC, MBC, MBN were the primary drivers of bacterial communities. • PICRUSt2 and FAPROTAX analysis differed in biogeochemical and metabolic functions. [ABSTRACT FROM AUTHOR]

Different agri-environmental schemes (AES), such as ecological focus areas and organic farming, have been suggested to reduce the impact of intensive agriculture on the environment and to conserve or even restore farmland biodiversity. However, the effectiveness of such schemes, their ability to actually support biodiversity and associated trade-offs with agricultural production are still debated. We analysed a large dataset from the biodiversity monitoring in the Swiss agricultural landscape to assess the effects of two different grassland AES, i.e., extensively managed ecological focus areas (EFAs versus non-EFAs) and organic farming (versus conventional), on plant diversity, plant community composition and productivity indicators, i.e., weed abundance, forage value and nutrient availability. We also considered environmental factors, i.e., topography and soil conditions, which potentially modulate AES effects on biodiversity. We used in total 1170 plots in permanent grasslands, managed as meadows or pastures. Both AES had significant positive effects on plant diversity. However, EFAs increased plant richness considerably stronger (+6.6 species) than organic farming (+1.8 species). Effects of the two schemes were additive with organic EFA grasslands exhibiting highest plant diversity. Differences in topography partly explained AES effects on diversity as both AES were associated with differences in elevation and slope. Thus, future assessments of the effectiveness of AES need to consider the non-random placement of AES across heterogeneous landscapes. EFA grasslands revealed a considerably reduced agricultural productivity as shown by low forage values and low nutrient availability. Yet, the abundance of agricultural weeds, i.e., agriculturally undesired plant species, was lower in EFA compared to non-EFA grasslands. Productivity indicators were only weakly affected by organic farming and other than for plant diversity, productivity did not differ between organic and conventional EFA grasslands. The positive additive diversity effects of EFAs and organic grassland farming underline the potential of both AES to contribute to biodiversity conservation in agricultural landscapes, though to a different extent. Comparing the effects of the two AES revealed that the lower the reduction in agricultural productivity associated with an AES, the smaller the gains in plant diversity, highlighting the inevitable trade-off between productivity and plant diversity in semi-natural grasslands. [Display omitted] • Agri-environmental schemes significantly increase grassland plant diversity. • Ecological focus areas increased local plant diversity more than organic farming. • The effects of the two agri-environmental schemes are additive. • Higher grassland plant diversity is inherently linked to lower productivity. • Agri-environmental schemes increased plant diversity under both grazing and mowing. [ABSTRACT FROM AUTHOR]

Groundwater dependent systems are extremely important habitats for a wide variety of taxa in the Great Basin of North America. The impacts of grazing on these habitats cause shifts in resources and subsequent change in species composition. The Greater sage-grouse, a keystone species of Great Basin ecosystems, rear offspring in these areas during spring and summer months using forbs and arthropods. To examine the impact of grazing on arthropod abundance in these ecosystems, seven meadows, each made up of three unique vegetative communities, were grazed at three intensities across two years (2019–2020) and monitored for environmental variables and abundance of arthropods during peak sage-grouse utilization periods. Additionally, the relationship of field measurements and near-surface digital cameras (phenocams) was examined to better understand how remote sensing technologies can be used to monitor these insect abundance shifts on larger scales. Arthropod taxa abundance responded differently to grazing management and environmental variables. Coleoptera abundance during peak sage-grouse usage periods increased roughly 50% in some meadows with increased grazing intensity. For year-to-year environmental variability in precipitation, Lepidoptera abundance was 114% higher in the drier year, while Coleoptera was 39% lower. Near-surface cameras had varied success with predicting peak insect abundance levels. Lepidoptera and Coleoptera capture rates had strong correlations with phenological indices derived from phenocams, while Formicidae had much weaker relationships. • Coleoptera abundance in high-elevation meadows increased with increased grazing. • Lepidoptera abundance was greater in the drier year, while Coleoptera was smaller. • Near-surface cameras had varied success with predicting peak insect abundance levels. [ABSTRACT FROM AUTHOR]

The distribution of seasonal precipitation would profoundly affect the dynamics of carbon fluxes in terrestrial ecosystems. However, little is known about the impacts of extreme precipitation and size events on ecosystem carbon cycle when compared to the effects of average precipitation amount. The study involved an analysis of carbon fluxes and water exchange using the eddy covariance and chamber based techniques during the growing seasons of 2015–2017 in Bayan, Mongolia and 2019–2021 in Hulunbuir, Inner Mongolia, respectively. The components of carbon fluxes and water exchange at each site were normalized to evaluate of relative response among carbon fluxes and water exchange. The investigation delved into the relationship between carbon fluxes and extreme precipitation over five gradients (control, dry spring, dry summer, wet spring and wet summer) in Hulunbuir meadow steppe and distinct four precipitation sizes (0.1–2, 2–5, 5–10, and 10–25 mm d−1) in Bayan meadow steppe. The wet spring and summer showed the greatest ecosystem respiration (ER) relative response values, 76.2% and 73.5%, respectively, while the dry spring (−16.7%) and dry summer (14.2%) showed the lowest values. Gross primary production (GPP) relative response improved with wet precipitation gradients, and declined with dry precipitation gradients in Hulunbuir meadow steppe. The least value in net ecosystem CO 2 exchange (NEE) was found at 10–25 mm d−1 precipitation size in Bayan meadow steppe. Similarly, the ER and GPP increased with size of precipitation events. The structural equation models (SEM) satisfactorily fitted the data (χ2 = 43.03, d.f. = 11, p = 0.215), with interactive linkages among soil microclimate, water exchange and carbon fluxes components regulating NEE. Overall, this study highlighted the importance of extreme precipitation and event size in influencing ecosystem carbon exchange, which is decisive to further understand the carbon cycle in meadow steppes. [Display omitted] • The wet summer increased ecosystem respiration and gross primary production (GPP). • GPP increased with increasing large size precipitation events. • The large precipitation size showed the lowest net ecosystem carbon exchange (NEE). • The relative response of GPP declined with dry precipitation events. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is a limiting nutrient second only to nitrogen (N) in the drylands of the world. Most previous studies have focused on N transformation processes in grassland ecosystems, particularly under artificial fertilization with N and atmospheric N deposition. However, P cycling processes under natural conditions and when P is applied as an inorganic P fertilizer have been understudied. Therefore, it is essential to examine the fate of applied P in grassland ecosystems that have experienced long-term grazing and, under certain circumstances, continuous hay harvest. We conducted a 3-year field experiment with the addition of multiple nutrient elements in a typical meadow steppe to investigate the fate of the applied P in various fractions of P pools in the top soil. We found that the addition of multiple nutrients significantly increased P concentrations in the labile inorganic P (Lab-P i) and moderately occluded inorganic P (Mod-P i) fractions but not in the recalcitrant inorganic P (Rec-P i) fraction. An increase in the concentration of total inorganic P was found only when P and N were applied together. However, the addition of other nutrients did not change P concentrations in any fraction of the mineral soil. The addition of P and N significantly increased the total amount of P taken up by the aboveground plants but had no effect on the levels of organic and microbial P in the soil. Together, our results indicate that the P applied in this grassland ecosystem is taken up by plants, leaving most of the unutilized P as Lab-P i and Mod-P i rather than being immobilized in Rec-P i or by microbial biomass. This implies that the grassland ecosystem that we studied has a relatively low P adsorption capacity, and the application of inorganic P to replenish soil P deficiency in degraded grasslands due to long-term grazing of livestock or continuous harvest of forage in the region could be a practical management strategy to maintain soil P fertility. • P deficiency in grassland ecosystems is caused by overgrazing and hay harvest. • P cycling with additions of inorganic P in grasslands has been understudied. • Fate of inorganic P in multi-nutrient additions was studied in a meadow steppe. • Inorganic P addition increased P levels in labile and moderately occluded fractions. • Application rate of inorganic P in degraded grassland ecosystems is recommended. [ABSTRACT FROM AUTHOR]

We investigate the spatiotemporal variability of near-surface CO 2 concentrations in Mongolia from 2010 to 2019 and the factors affecting it over four climate zones of Mongolia based on the Köppen-Geiger climate classification system, including arid desert climate (BWh), arid steppe climate (BSk), dry climate (Dw), and polar frost climate (ET). Initially, we validate the near-surface CO 2 datasets obtained from the Greenhouse Gases Observing Satellite (GOSAT) using ground-based CO 2 observations obtained from the World Data Center for Greenhouse Gases (WDCGG) and found good agreement. The results showed that CO 2 concentrations over Mongolia steadily increased from 389.48 ppmv in 2010 to 409.72 ppmv in 2019, with an annual growth rate of 2.24 ppmv/year. Spatially, the southeastern Gobi desert region has the highest annual average CO 2 concentration, while the northwestern Alpine and Meadow steppe region exhibits the most significant growth rate. Additionally, significant monthly and seasonal variations were observed in each climate zone, with CO 2 levels decreasing to a minimum in summer and reaching a maximum in spring. Furthermore, our findings revealed a negative correlation between CO 2 concentrations and vegetation parameters (NDVI, GPP, and LAI) during summer when photosynthesis is at its peak, while a positive correlation was observed during spring and autumn when the capacity for carbon sequestration is lower. Understanding CO 2 concentrations in different climate zones and the uptake capacity of vegetation may help improve estimates of carbon sequestration in ecosystems such as deserts, steppes and forests. • Annual mean near-surface CO 2 concentrations in Mongolia increased at a rate of 2.24 ppmv/year during 2010–2019. • Near-surface CO 2 concentrations are higher in the southeastern of Mongolia. • CO 2 levels decrease to a minimum during the summer and reach a maximum during the spring. • Over grazing and mining industries in the Gobi desert have accelerated CO 2 emissions. [ABSTRACT FROM AUTHOR]

Livestock grazing is the primary practice in alpine meadows and can alter soil microbiomes, which is critical for ecosystem functions and services. Seasonal grazing (SG) and continuous grazing (CG) are two kinds of different grazing practices that dominate alpine meadows on the Qinghai-Tibetan Plateau (QTP), and how they affect soil microbial communities remains in-depth exploration. The present study was conducted to investigate the effects of different grazing practices (i.e. , SG and CG) on the diversity, composition, and co-occurrence networks of soil bacteria and fungi in QTP alpine meadows. Soil microbial α- and β-diversity showed no obvious difference between SG and CG grasslands. Grazing practices had little impact on soil microbial composition, except that the relative abundance of Proteobacteria and Ascomycota showed significant difference between SG and CG grasslands. Soil microbial networks were more complex and less stable in SG grasslands than that in CG grasslands, and the bacterial networks were more complex than fungal networks. Soil fungal diversity was more strongly correlated with environmental factors than bacteria, whereas both fungal and bacterial structures were mainly influenced by soil pH, total nitrogen, and ammonium nitrogen. These findings indicate that microbial associations are more sensitive to grazing practices than microbial diversity and composition, and that SG may be a better grazing practice for ecological benefits in alpine meadows. • Soil microbial networks more complex in SG than CG grasslands. • No difference in soil microbial α- and β-diversity between SG and CG grasslands. • Grazing practices have little effect on soil microbial composition. • Soil fungi more correlated with environmental factors than bacteria. • SG may be more conducive to sustainable alpine meadow ecosystem development. [ABSTRACT FROM AUTHOR]

Understanding how microbial processes develop and change in alpine meadow soils is key to global initiatives toward environmental sustainability and local land management. Yet, how microbial interactions mediate soil multifunctionality in disturbed and managed alpine meadows remains understudied. Here, we investigated multiple community metrics, particularly microbial network properties and assembly processes, of soil bacterial and fungal communities and their links to certain soil functions along a degradation-restoration sequence of alpine meadows in the Qinghai-Tibetan Plateau. Meadow degradation caused significant declines in soil hydraulic conductivity (e.g., higher bulk density, reduced soil porosity and water content) and nitrogen availability, leading to lowered soil multifunctionality. Meadow degradation only caused weak changes in microbial abundance, alpha diversity, and community composition, but remarkably reduced bacterial network complexity, to a less extent for fungal network properties. Short-term artificial restoration with productive grass monocultures did not restore soil multifunctionality, in turn even destabilized bacterial network and favored pathogenic over mutualistic fungi. Soil fungi community are more stable than bacteria in disturbed alpine meadows, and they evolved with distinct assembly strategies (stochastic-dominant versus deterministic-driven processes, respectively). Further, microbial network complexity, positively and better predicts soil multifunctionality than alpha diversity. Our work shows how microbial interaction complexity may enhance soil multifunctionality in degraded alpine meadow ecosystems, noting that meadow restoration with low plant species diversity may failed in restoring multiple ecosystem functions. These findings would help predict the outcomes of global environmental changes and inform management strategies in regional grassland conservation and restoration. [Display omitted] • Soil multifunctionality consistently reduced along the meadow developmental sequence. • Microbial diversity showed weak to no responses to meadow degradation/restoration. • Fungal network features responded less to meadow degradation/restoration than bacteria. • Revegetated grass monocultures failed to restore microbial network complexity. [ABSTRACT FROM AUTHOR]

The soil carbon (C) and nitrogen (N) availability are important in the regulation of soil C cycling under climate change. Fertilizers alter soil C and N availability, which can affect C balance. However, the impact of fertilizers on C balance in grassland restoration has been equivocal and warrants more research. We determined the direct and indirect effects of the addition of three levels of C (sucrose) (0, 60, and 120 kg C ha−1 yr−1), three levels of N (urea) (0, 50, and 100 kg N ha−1 yr−1), and a combination of C plus N at each of the levels on soil respiration (Rs) dynamics and C balance in an alpine meadow in northern Tibet (4700 m above sea level). This study was undertaken during the middle of the growing season in 2011–2012. The addition of C and/or N stimulated CO 2 emission, which was 2-fold greater in 2011 (102–144 g C m−2) than in 2012 (43–54 g C m−2). The rate of Rs increased with the addition of N, but was not affected with the addition of C plus N. Microbial biomass C, dissolved organic C and inorganic N were the main drivers of Rs. We concluded that N addition stimulated Rs to a greater extent than C addition in the short term. The application of fertilizer in the restoration of degraded grassland should be re-considered. • Soil microbial content was the main driver of soil respiration (Rs). • N availability stimulated Rs to a greater extent than C availability. • The addition of C and/or N stimulated CO 2 emission by less than 31%. • The addition of C and/or N had no effect on C sequestration. [ABSTRACT FROM AUTHOR]

Subalpine meadow soil with high moisture and humus content is a unique soil type in the Zoige Plateau. Oxytetracycline and copper are common soil contaminants which interact to form compound pollution. Oxytetracycline's adsorption on natural subalpine meadow soil and its components (humin and the soil without iron and manganese oxides) was studied in the laboratory with and without the presence of Cu2+. The effects of temperature, pH and Cu2+ concentration were documented in batch experiments, allowing deduction of the main sorption mechanisms. The adsorption process had two phases: one rapid, taking place in the first 6 h, and another slower, reaching equilibrium at around 36 h. The adsorption kinetics were pseudo-second-order, and the adsorption isotherm conformed to the Langmuir model at 25 °C. Higher concentrations oxytetracycline increased the adsorption, but higher temperature did not. The presence of Cu2+ had no effect on the equilibrium time, but the amount and rate adsorbed were much greater with Cu2+ concentration increased (except for the soil without iron and manganese oxides). The amounts adsorbed with/without Cu2+ were in the order the humin from subalpine meadow soil (7621 and 7186 μg/g) > the subalpine meadow soil (7298 and 6925 μg/g) > the soil without iron and manganese oxides (7092 and 6862 μg/g), but the difference among those adsorbents was slight. It indicates that humin is a particularly important adsorbent in the subalpine meadow soil. The amount of oxytetracycline adsorbed was greatest at pH 5–9. In addition, Surface complexation through metal bridging was the most important sorption mechanism. Cu2+ and oxytetracycline formed positively-charged complex that was adsorbed and then formed a ternary complex "adsorbent-Cu(II)-oxytetracycline", in which Cu2+ acted as a bridge. These findings provide a good scientific basis for soil remediation, and for assessing environmental health risks. [Display omitted] • Subalpine meadow soil with high humus content is unique soil type in Zoige Plateau. • Capacity and rate adsorbed of OTC increased with the present and content of Cu2+. • Humin in subalpine meadow soil has the greatest contribution to the OTC adsorption. • Surface complexation through Cu2+ bridging is the dominant adsorption mechanism. [ABSTRACT FROM AUTHOR]

• Secondary dispersal is an important process in seagrass meadows. • Microtopography could affect secondary seed dispersal distances. • A theory relating secondary dispersal with the microtopography is formulated. • The formulation is validated with computational fluid dynamics for two seagrasses. • These results can inform seed-based restoration to assess secondary dispersal. Motivated by observational and experimental evidence, a theoretical model is proposed to relate the secondary dispersal of seagrass seeds with the complexity of microtopography in natural environments. Complexity is encoded in terms of the Hurst exponent of a fractal description of the microtopographical geometry. The percentage of a seafloor transect where secondary dispersal of seagrass seeds occurs, is quantified in terms of the mainstream velocity, bottom complexity and properties of the seeds. Theoretical expressions are validated considering the cases of Zostera marina and Posidonia oceanica seeds and using computational fluid dynamics (CFD). A total of 200 CFD simulations with different bottom complexities and flow conditions, were done for each seagrass genus to validate the theoretical model. Numerical results agree with theoretical predictions. This finding provides a management tool to assess the degree of seed retention in seed-based restoration areas. [ABSTRACT FROM AUTHOR]

The quantification of changes in long-term trends in grassland net primary productivity (NPP) and its large-scale driving forces are important for understanding terrestrial ecosystem changes in arid and semi-arid regions. Based on the MODIS-NPP dataset, this study investigated patterns in the spatiotemporal variations in NPP and its possible influencing factors in Inner Mongolia during 2000–2014 using the linear trend analysis method, correlation analysis, and an F test. The results show that grassland NPP had an annual rate of increase of 4.53 g C/(m2·a) with a significant increasing trend (p < 0.01). Spatial analysis results indicate that the average grassland NPP presented a gradual increasing trend from southwest to northeast, with an area of longitudinal zonality being identified. Grassland NPP presented a significant increase (p < 0.05) in more than 31.93% of the region. Grassland NPP and growing season precipitation (GSP) had a significant negative correlation in 54.78% of the study area. Grassland NPP and the growing season average land surface temperature (GSALST) had a significant negative correlation for 65.93% of the study area; growing season average temperature (GSAT) had no significant effect on the grassland NPP. For different grassland types, GSP had the greatest impact on alpine meadows (r = 0.73), and GSALST had the greatest impact on alpine steppes and alpine meadows (r = −0.81). Related ecological restoration projects such as fenced rangeland and planted grass played a positive impact on annual NPP in the study area. Image 1 • Spatial-temporal changes of NPP were analyzed in Inner Mongolia from 2000 to 2014. • Linear trend analysis and partial correlation analyses were used to this study. • There was different correlation between NPP and GSAT/GSP/GSALST. • The correlations between NPP and GSAT/GSALST in different grassland types were similar. • Human activities played a decisive role for the yearly increases of grassland NPP. [ABSTRACT FROM AUTHOR]

The diurnal cycles of carbon chemistry parameters, i.e., dissolved inorganic carbon (DIC), total alkalinity (TA), partial pressure of CO 2 ( p CO 2 ), and pH, were investigated in two hydrodynamically contrasting seagrass meadows at Dongsha Island in the northern South China Sea in August 2015. The results show that the pH and TA were higher and that the p CO 2 was lower in the semi-enclosed inner lagoon (IL) than on the open north shore (NS). The analyses of carbon chemistry parameters vs. dissolved oxygen and TA vs . DIC relationships reveal that the CO 2 dynamics was dominated by photosynthesis/respiration (P/R) alone on the NS but by the combined effect of P/R and sedimentary anaerobic pathways in the IL. We suggest that the observed divergent behaviors in carbon chemistry between the two sites could be attributed to differences in hydrodynamic regimes. The less energetic hydrodynamics and longer residence time in the IL would be favorable for the occurrence of sedimentary anaerobic TA generation and the subsequent TA accumulation in the overlying waters. The elevated TA may lead to a pH increase and a p CO 2 decrease, thus providing a buffering effect against ocean acidification (OA) and enhancing atmospheric CO 2 sequestration at local scales. The present results demonstrate that hydrodynamic regime may play an important role in regulating biogeochemical processes in seagrass meadows, and thereby modulating their capacities in OA buffering and CO 2 uptaking. [ABSTRACT FROM AUTHOR]

In the Andes of southern South America, wet meadows are much more productive than nearby arid areas. Human activities, along with climate variations may reduce the productivity of these ecosystems. However, we do not know what the relative effect of climate and human activities on their degradation status is. Here, we first quantified the degradation extent through the temporal trend of normalized difference vegetation index (NDVI), a proxy of productivity, from 1999 to 2017. We did it in 736 wet meadow areas inserted in three nearby zones with contrasting land management. Second, we analyzed the relationship between NDVI and a large-scale mode of climate variability (El Niño Southern Oscillation, ENSO) and regional climate variables (precipitation and temperature) through a structured climate model. Finally, we evaluated human activities' effects through the temporal trends in the residuals of the climate model. Independently of land management, NDVI trends were mainly negative and affected 56% of the wet meadow areas. The climate model indicated that NDVI increased under La Niña, cool and wet years. Regarding land management, the degradation level was similar across the contrasted land management. Our results suggest that climate factors rather than human activities influenced the degradation process in these areas. • Productivity during 1999–2017 decreased in 56% of the wet meadow areas. • Productivity increased under La Niña, cool and wet years. • Productivity negative trends were mainly related to climate factors rather the human activities. [ABSTRACT FROM AUTHOR]

Corpse decomposition is of great significance to the carbon cycle of natural ecosystem. Carbon fixation is a carbon conversion process that converts carbon dioxide into organic carbon, which greatly contributes to carbon emission reduction. However, the effects of wild animal carcass decay on carbon-fixing microbes in grassland soil environment are still unknown. In this research, thirty wild mammal (Ochotona curzoniae) corpses were placed on alpine meadow soil to study the carbon storage and carbon-fixing microbiota succession for a 94-day decomposition using next-generation sequencing. Our results revealed that 1) the concentration of total carbon increased approximately 2.24–11.22% in the corpse group. 2) Several carbon-fixing bacterial species (Calothrix parietina, Ancylobacter rudongensis , Rhodopseudomonas palustris) may predict the concentration of total carbon. 3) Animal cadaver degradation caused the differentiation of carbon-fixing microbiota structures during succession and made the medium-stage networks of carbon-fixing microbes more complicated. 4) The temporal turnover rate in the experimental groups was higher than that in the control groups, indicating a quick change of gravesoil carbon-fixing microbiota. 5) The deterministic process dominates the assembly mechanism of experimental groups (ranging from 53.42% to 94.94%), which reflects that the carbon-fixing microbial community in gravesoil can be regulated. Under global climate change, this study provides a new perspective for understanding the effects of wild animal carcass decay on soil carbon storage and carbon-fixing microbes. [Display omitted] • Corpse decay changed the structure of soil carbon-fixing microbes. • Carcass decay improved the complexity of the medium-stage network. • The deterministic process dominated the assembly mechanism all the time. • The resistance of soil environment to carcass decay were shown by the results. [ABSTRACT FROM AUTHOR]

The efficacy of a Mediterranean Marine Protected Area (National Marine Park of Zakynthos – NMPZ, Ionian Sea, Greece) that implements a seasonal no-take zone as part of its management scheme was assessed using fish data collected in situ with underwater visual census. Sampling was conducted at two habitat types ( Posidonia oceanica meadows and rocky reefs) that occur at sites of different protection level with respect to fisheries (high protection: seasonal no-take zone within the MPA; intermediate: zones within the MPA where small-scale fishing is allowed; none: areas outside the MPA, where all types of fishing are allowed, including trawlers, purse seiners, and recreational fishing). The data were used to examine the effects of protection level and habitat type on community parameters, trophic structure and functional diversity of fish populations that occupy the upper sublittoral zone. Overall, habitat type had a more pronounced effect than protection level on all investigated parameters. Biomass, density and number of fish species with low commercial value were higher in sites of intermediate protection, but no substantial fisheries-related ecological benefits were detected for targeted fish in the seasonal no-take zone. Conducted 8 years after the initial implementation of the seasonal no-take management scheme, our study suggests that existing fishing regulations in the NMPZ provide some measurable effects, but fall short of maintaining sufficient protection for the recovery of apex predators or other commercially important fish species. A revision of the existing zoning system to include permanent no-take zones, alongside the regulation of professional fishing and all extractive activities in the rest of the MPA, are strongly encouraged in order to enhance the effectiveness of fisheries management. [ABSTRACT FROM AUTHOR]

Abstract: Seagrass meadows serve as marine carbon sinks, though rates of carbon burial and sediment accretion may vary within and among seagrass meadows due to spatial and temporal variability in sedimentary and biophysical conditions. However, few data are available to evaluate variation in carbon burial over decades to centuries, particularly in subtropical seagrass meadows. Here we assess historical trends in rates of vertical accretion and carbon burial in subtropical seagrass sediments in Moreton Bay, Australia. A total of 19 sediment cores varying in length from 22 to 205 cm were collected from six locations, including two locations where seagrass meadows occurred historically but were lost in recent decades. Cores were dated using 210 Pb and 14 C. Geochronologies were modelled based on the successful 210 Pb dates for two of the locations combined with 14 C at five locations. Organic and inorganic carbon content, dry bulk density and stable carbon and nitrogen isotope composition (δ 13 C org , δ 15 N) were measured throughout the cores. Sediments underlying seagrass meadows in Moreton Bay have organic carbon stored up to a depth of at least 2 m which dates to over 7000 yr BP. Across the entire time series, organic carbon burial rates averaged 19 g m −2 yr −1 and inorganic carbon burial rates averaged 27 g m −2 yr −1 . Overall mean rates of vertical accretion were estimated to be 0.2 cm yr −1 . Rates of vertical accretion accelerated 10-fold following European colonisation which commenced in 1824, from 0.06 ± 0.06 cm yr −1 to 0.66 ± 1.19 cm yr −1 . Similarly, rates of organic carbon burial averaged 7.2 ± 5.5 g m −2 yr −1 but then increased 7-fold post-colonisation to 50.5 ± 82.1 g m −2 yr −1 . Thus, in Moreton Bay, European settlement and associated land-use change has enhanced sediment accretion and carbon burial in seagrass sediments. [ABSTRACT FROM AUTHOR]

Coastal zones are productive areas of marine ecosystems which are also hotspots of anthropogenic activities causing habitat degradation. In the southwest Baltic Sea, eutrophication is thought to have caused the massive reduction in submerged macrophytes observed in recent decades. Here, we surveyed the submarine vegetation and examined locations of spawning of herring ( Clupea harengus ) in the Greifswalder Bodden, one of the most important reproductive habitats of the Western Baltic Spring Spawner herring stock (WBSS). This stock deposits eggs onto submerged vegetation and changes in macrophyte coverage are expected to influence the availability of reproductive habitat. Aerial, underwater video tows and SCUBA surveys conducted in spring 2009 revealed that only ∼7% of the lagoon was vegetated. Herring eggs were observed on 12 of 32 SCUBA transects, at depths between 0.2 and 5 m and were attached to a variety of spermatophyte and algae species but not to stones or mussels. A classification tree model indicated that spawning sites were strongly associated with the vegetation cover within a 100- and 500-m radius, implying that herring schools preferentially spawn on dense and large underwater meadows. Only ∼5% of the lagoon now falls into this vegetation category. Despite 20 years of efforts to reduce eutrophication, no increase in macroalgae and spermatophyte vegetation towards the historical level of 90% coverage in the area is apparent. [ABSTRACT FROM AUTHOR]

The Camas National Wildlife Refuge (Refuge) in eastern Idaho, established in 1937, contains wetlands, ponds, and wet meadows that are essential resting and feeding habitat for migratory birds and nesting habitat for waterfowl. Initially, natural sources of water supported these habitats. However, during the past few decades, changes in climate and surrounding land use have altered and reduced natural groundwater and surface-water inflows, resulting in a 5-meter decline in the water table and an earlier, and more frequent, occurrence of no flow in Camas Creek at the Refuge. Due to these changes in water availability, water management that includes extensive groundwater pumping is now necessary to maintain the wetlands, ponds, and wet meadows. These water management activities have proven to be inefficient and expensive, and the Refuge is seeking alternative water-management options that are more efficient and less expensive. More efficient water management at the Refuge may be possible through knowledge of the seepage rates from ditches, ponds, and lakes at the Refuge. With this knowledge, water-management efficiency may be improved by natural means through selective use of water bodies with the smallest seepage rates or through engineering efforts to minimize seepage losses from water bodies with the largest seepage rates. The U.S. Geological Survey performed field studies in 2015 and 2016 to estimate seepage rates for selected ditches, ponds, and lakes at the Refuge. Estimated seepage rates from ponds and lakes ranged over an order of magnitude, from 3.4 ± 0.2 to 103.0 ± 0.5 mm/d, with larger seepage rates calculated for Big Pond and Redhead Pond, intermediate seepage rates calculated for Two-way Pond, and smaller seepages rates calculated for the south arm of Sandhole Lake. Estimated seepage losses from two reaches of Main Diversion Ditch were 21 ± 2 and 17 ± 2 percent/km. These losses represent seepage rates of about 890 and 860 mm/d, which are one- to two-orders-of-magnitude larger than seepage rates from the ponds and lake. The depth-integrated vertical hydraulic conductivity ( K v ) for sediment underlying the ponds and lake was the primary control of seepage rates. The K v 's were 30 and 34 m/d for Big Pond, 14 and 18 m/d for Toomey Pond, 8 and 10 m/d for Two-way Pond, and 47 m/d for the north arm of Sandhole Lake. [ABSTRACT FROM AUTHOR]

The seagrass, Halophila ovalis plays an important ecological and sediment stability role in estuarine systems in Australia with the species in decline in many sites. Halophila ovalis is a facultative annual, relying mainly on recruitment from the sediment seed bank for the annual regeneration of meadows. Despite this, there is little understanding of seed dormancy releasing mechanisms and germination cues. Using H. ovalis seed from the warm temperate Swan River Estuary in Western Australia, the germination ecology of H. ovalis was investigated by simulating the natural seasonal variation in water temperatures. The proportion of germinating seeds was found to be significantly different among temperature treatments (p < 0.001). The treatment with the longest period of cold exposure at 15 °C followed by an increase in temperature to 20–25 °C (i.e. cold stratification) had the highest final mean germination of 32% and the fastest germination rate. Seeds exposed to constant mean winter temperatures of 15 °C had the slowest germination rate with less than two seeds germinating over 118 days. Thus temperature is a key germination cue for H. ovalis seeds and these data infer that cold stratification is an important dormancy releasing mechanism. This finding has implications for recruitment in facultative annual species like H. ovalis under global warming since the trend for increasing water temperatures in the region may limit seed-based recruitment in the future. [ABSTRACT FROM AUTHOR]

Parks and protected areas are integral strategies for biological diversity conservation, and their management often involves balancing visitor use with resource protection. Effectively balancing these objectives requires data about how use is distributed within areas of interest and how management strategies and environmental conditions interact to minimize negative impacts. This study examined which environmental and managerial factors most influenced the distribution of domestic pack stock animals, a common visitor use-related activity, when released to graze in high elevation meadows. Using a species distribution modelling approach, MaxEnt, managerial factors were found to be among the top contributors to models. Pack stock animals concentrated use near the locations where they were released as well as portable enclosure fencing confining the lead animal even though the remainder were allowed to roam freely. Elevation was the environmental factor contributing most, with animals remaining at similar elevations to the meadow even if moving into nearby understory. Results highlight the importance of release point and fence locations to overall pack stock animal distribution and rotational or strategic placement can be a tactic for mitigating impacts to sensitive habitats. [ABSTRACT FROM AUTHOR]

Climate change has increased interest in seagrass systems as natural carbon sinks and recent studies have estimated the carbon stocks associated with seagrass meadows. However, the factors that affect their variability remain poorly understood. This paper assesses how landscape-level attributes (patch size and matrix composition) influence carbon storage in seagrass sediments. We quantified the organic carbon (C org ) content and other geochemical properties (δ 13 C and particle size) in surface sediments of continuous Posidonia oceanica meadows, patchy meadows interspersed with rocky-algal reefs and patchy meadows on sedimentary bottoms. We also took samples of potential carbon sources for isotopic composition determination. Our results indicate that the continuous meadows accumulated larger amounts of C org than patchy meadows, whether embedded in a rock or sand matrix. The C org from continuous meadows was also more 13 C enriched, which suggests that a high proportion of the carbon was derived from plant material (autochthonous sources); in contrast in patchy meadows (especially in a sand matrix), lower δ 13 C values indicated a higher contribution from allochthonous sources (mainly suspended particulate organic matter, SPOM). These findings suggest that the sediment of continuous meadows stores more C org in than that of patchy meadows. This is probably due to the increased contribution from seagrass leaves, which are much more refractory than SPOM. In general, certain landscape configurations, and especially patchiness, appear to reduce the carbon storage capacity of seagrasses. Since the current decline of seagrass is leading to habitat fragmentation, our results increase the argument for the promotion of effective measures to preserve the integrity of these natural carbon sinks. [ABSTRACT FROM AUTHOR]

Over-compensatory growth of plants after disturbance is generally preferred by grassland users and managers because of more forage. How the grassland productivity and the plant growth condition before disturbance affect the compensatory growth are important for grazing management and the understanding of grassland degradation, yet they are not well understood. A clipping experiment was conducted on the Qinghai-Tibetan Plateau to understand the compensatory growth and conditions for the occurrence of over-compensatory at alpine meadows with different degradation status. Results showed the competition for light constrains the plant growth post-clipping at non-degraded and slightly degraded alpine meadows, while the reduction of soil nitrogen limits it at heavily degraded alpine meadow. The biomass accumulated post-clipping was positively correlated with the growing season biomass in unclipped plots and the biomass at clipping in clipped plots. When the aboveground biomass at clipping was less than 40.10 g m−2 and the growing season biomass was between 38 and 97 g m−2, the over-compensatory growth of alpine meadow could occur. Higher clipping rate is required for the alpine meadow with high productivity but the maximum clipping rate should be less than 0.71 to induce the over-compensatory growth. Equal-compensatory occurred at non-degraded and slightly degraded, while over-compensatory growth was observed at moderately degraded and a marginally significant over-compensatory growth at heavily degraded alpine meadow. The over-compensatory growth occurred at moderately degraded alpine meadow is mainly due to the performance of forbs. Our results suggest that grazing at moderately degraded alpine meadow may induce the over-compensatory growth at the community level, but the over-compensatory growth of forbs at moderately degraded alpine meadow may aggravate the alpine meadow degradation. • Over-compensatory growth only occurred in moderately degraded alpine meadow. • Competition for light limits the regrowth in non- and lightly degraded AM. • The AGB at clipping should be less than 40.01 g m−2 to induce over-compensatory. • When clipping rate is over 0.71, over-compensatory growth never happens. [ABSTRACT FROM AUTHOR]

Over time, grassland use has changed from traditional (extensive) to intensive agricultural management, a change which has caused biodiversity loss in the European grassland area. To save Europe's biodiversity, the most important measure was the establishment of the Natura 2000 network. Goričko Landscape Park in Slovenia is in Natura 2000 to preserve its traditional and extensive small-scale farming. The aims of this research were to identify potential obstacles to proper management of the extensively used meadows in this region and identify major factors that would affect such management in order to prepare more appropriate strategies for habitat conservation. The data was collected by online survey and in paper and pencil format. Based on Principal Component Analysis (PCA), Confirmatory Factor Analysis and Structural Equation Modelling, we can conclude that less than a half of 228 respondents can identify what activities are permitted in a Natura 2000 area, which indicates a lack of knowledge about Natura 2000. The majority agree with meadow management in the welfare of protected plants and animals but would accept management under stricter regulations only if accompanied by higher subsidies in for management under stricter regulations. These respondents are not prepared to participate in measures for preserving biodiversity without beneficiaries. Respondents have in average a positive opinion toward protected plants and animals, but the procedure for obtaining environmental subsidies for meadows seems to them too complicated. Although the majority of respondents do not see a Natura 2000 area as a place for quality living, it is the factor with the highest significant effect on willingness to participate in measures to preserve biodiversity. [ABSTRACT FROM AUTHOR]

Toxic plants are a natural component of alpine meadow which co-evolved with Tibetan sheep for thousands of years. One challenge for indigenous herders is to know the ecological thresholds of toxic plants and maintain their vital functions in ways that are compatible with economic income and ecological conservation. To achieve this, field trials with Tibetan sheep grazing in alpine meadow were conducted to examine the ecological thresholds of toxic plants for sheep production and ecosystem functions and their trade-offs. Our results demonstrated that the changing point values of biomass proportion of toxic plants for dry matter intake and liveweight gain of sheep were 17% and 22%, respectively. The changing point value of biomass (richness) proportion of toxic plants for soil carbon accumulation index was 31% (59%), for soil nutrient cycling index was 38% (42%), and for ecosystem multifunctionality index was 28% (50%). The trade-off between liveweight gain of sheep and ecosystem multifunctionality first decreased and then increased along the gradient of biomass proportion of toxic plants (the value of changing point was 37%), and had a significant negative correlation with richness of toxic plants. In addition, structural equation modeling indicated that toxic plants can affect the trade-off between liveweight gain of sheep and ecosystem multifunctionality though increasing acid detergent fiber of plant and decreasing plant species richness, belowground biomass and soil total phosphorus. Consequently, opinions towards toxic plants should shift from the conventional view that they are serious threat to grassland ecosystem health to an inclusive understanding that they are beneficial to livestock and ecosystem functions under certain ecological thresholds. • The thresholds of toxic plants for LWG of sheep and EMF were 22% and 28%. • The changing point of toxic plants for trade-off between sheep LWG and EMF was 37%. • Toxic plants affect the trade-offs via altering key parameters of plant and soil. • We proposed a new comprehensive classification system of toxic plants. [ABSTRACT FROM AUTHOR]

Alpine meadows, typical steppes, and deserts are among the globally important rangeland types that are generally distributed along temperature and precipitation gradients. Mineral losses caused by grazing are one of the key factors that can lead to instability or even degradation of these rangeland ecosystems. We examined the concentrations of Cu, Fe, Mn, and Zn in soil, forage, and livestock dungs from diverse rangeland types in northwest China, to determine the relationships between these trace elements (TEs) concentrations and climatic factors (i.e., temperature, precipitation, and humidity), and to evaluate the potential risks of TEs deficiencies or excesses in these rangeland ecosystems. Forage Zn concentrations in forage of all three types of rangeland, and Cu concentrations in forage of the alpine meadow did not meet the growth requirements of grazing livestock. Concentrations of Cu, Fe, and Mn in forage and Fe, Mn, and Zn in livestock dungs had quadratic parabola relationships with temperature, precipitation, and humidity, but the relationships between climate factors and Cu, Fe, and Mn concentrations in soil were not significant. In addition, the abilities of the plant to absorb Cu, Fe, and Zn from soil were stronger in the typical steppe than that in the alpine meadows and desert. Also, the abilities of livestock to return TEs to soil were stronger in the alpine meadow than that in the typical steppe and desert. We derived a conceptual mode that the ratio of TE concentrations of the plant to soil and of livestock dung to forage represents the abilities of plants to absorb TEs from the soil matrix and livestock to return TEs to soil or to absorb TEs from forage, respectively. Results indicate potentially more serious risks of TEs deficiencies, especially that of Zn than previously considered in typical steppes and desert rangelands. • 1, Forage Zn concentrations in inland rangelands could not meet the growth requirement of grazing livestock. • 2, Climate factors can explain the changes of TE concentrations in forage but in soil. • 3, There is more serious risks of TE deficiencies than previously considered in typical steppes and desert. [ABSTRACT FROM AUTHOR]

Seagrass meadows, through their large capacity to sequester and store organic carbon in their sediments, contribute to mitigate climatic change. However, these ecosystems have experienced large losses and degradation worldwide due to anthropogenic and natural impacts and they are among the most threatened ecosystems on Earth. When a meadow is impacted, the vegetation is partial- or completely lost, and the sediment is exposed to the atmosphere or water column, resulting in the erosion and remineralisation of the carbon stored. This paper addresses the effects of the construction of coastal infrastructures on sediment properties, organic carbon, and total nitrogen stocks of intertidal seagrass meadows, as well as the size of such stocks in relation to meadow establishing time (recently and old established meadows). Three intertidal seagrass meadows impacted by coastal constructions (with 0% seagrass cover at present) and three adjacent non-impacted old-established meadows (with 100% seagrass cover at present) were studied along with an area of bare sediment and two recent-established seagrass meadows. We observed that the non-impacted areas presented 3-fold higher percentage of mud and 1.5 times higher sedimentary organic carbon stock than impacted areas. Although the impacted area was relatively small (0.05–0.07 ha), coastal infrastructures caused a significant reduction of the sedimentary carbon stock, between 1.1 and 2.2 Mg OC, and a total loss of the carbon sequestration capacity of the impacted meadow. We also found that the organic carbon stock and total nitrogen stock of the recent-established meadow were 30% lower than those of the old-established ones, indicating that OC and TN accumulation within the meadows is a continuous process, which has important consequences for conservation and restoration actions. These results contribute to understanding the spatial variability of blue carbon and nitrogen stocks in coastal systems highly impacted by urban development. • Seagrass organic carbon (OC) stock was impacted by coastal infrastructures. • OC stocks at impacted areas were 1.5 times lower than at non-impacted areas. • Non-impacted areas presented 3-fold higher percentage of mud than impacted areas. • Recently established meadow presented 30% lower OC than the old-established ones. [ABSTRACT FROM AUTHOR]

Grasslands are now facing a continuously increasing supply of nitrogen (N) fertilizers, resulting in alterations in ecosystem functioning, including changes in carbon (C) and water cycling. Mowing, one of the most widely used grassland management techniques, has been shown to mitigate the negative impacts of increased N availability on species richness. However, knowledge of how N addition and mowing, alone and/or in combination, affect ecosystem-level C fluxes and water use efficiency (W N) is still limited. We experimentally manipulated N fertilization (0 and 10 g N m−2 yr−1) and mowing (once per year at the end of the growing season) following a randomized block design in a meadow steppe characterized by salinization and alkalinization in northeastern China. We found that, compared to the control plots, N addition, mowing, and their interaction increased net ecosystem CO 2 exchange by 65.1%, 14.7%, and 133%, and W N by 40.7%, 18.5%, and 96.1%, respectively. Nitrogen enrichment also decreased soil pH, which resulted in greater aboveground biomass (AGB). Moreover, N addition indirectly increased AGB by inducing changes in species richness. Our results indicate that mowing enhances the positive effects of N addition on ecosystem C fluxes and W N. Therefore, appropriate grassland management practices are essential to improve ecosystem C sequestration, W N , and mitigate future species diversity declines due to ecosystem eutrophication. • Nitrogen addition increases ecosystem carbon fluxes and water use efficiency. • Mowing enhances the impacts of nitrogen on carbon flux and water use efficiency. • Soil acidification alleviates the adverse effects of the alkaline environment. • Grasslands restoration should consider both nutrient augmentation and mowing. [ABSTRACT FROM AUTHOR]

Ecological analyses are aimed at characterizing the complexity of the structure of natural objects, yet their heterogeneity is hardly described by the Euclidean concepts. For such purpose, the fractal geometry can be best suited due to its ability in describing, with mathematical rigor, the inherent irregularity of nature. Fractal dimension provides indeed a measurement of the complexity of the analyzed object in terms of space occupation. In this study, we applied the fractal geometry to Posidonia oceanica in order to characterize the structural complexity of its meadows, which are widely recognized as one of the most important coastal ecosystems in the Mediterranean basin. For achieving our aim, we developed an ad hoc implementation of the Box-Counting algorithm based on the Moore neighborhood analysis. Our approach allowed to render the structural complexity of P. oceanica meadows spatially explicit, thus expressing an intrinsic ecological property. The fractal analysis suggested that the complexity of meadows structure is intimately connected with the ecological conditions of P. oceanica. In fact, meadows in living and mixed conditions showed a higher fractal dimension, suggesting a largely uniform and smooth structure. While the fractal dimension associated to the regressed ecological condition of P. oceanica meadows exhibited lower values, highlighting a more jagged and rough structure. Therefore, the fractal theory may prove useful to both fundamental and applied ecological research focusing on P. oceanica and its interactions with Mediterranean coastal ecosystems. In fact, the fractal analysis we performed could result in an effective and straightforward approach for assessing the condition of P. oceanica at large spatial scale, enhancing an integrated maritime spatial planning over the whole Mediterranean basin. • Posidonia oceanica meadows are paramount ecosystems in the Mediterranean basin. • The complexity of meadows structure is a crucial property of Posidonia oceanica. • Fractal geometry is capable of describing the inherent complexity of nature. • Fractal dimension resulted strictly related to the ecological condition of meadows. • Fractal analysis proved to be effective for the assessment of meadows condition. [ABSTRACT FROM AUTHOR]

Background As a consequence of global change, intensity and frequency of extreme events such as heat waves (HW) have been increasing worldwide. Methods By using a combination of continuous 60-year meteorological and 6-year tower-based carbon dioxide (CO 2 ) flux measurements, we constructed a clear picture of a HWs effect on the dynamics of carbon, water, and vegetation on the Eurasian Songnen meadow steppe. Results The number of HWs in the Songnen meadow steppe began increasing since the 1980s and the rate of occurrence has advanced since the 2010s to higher than ever before. HWs can reduce the grassland carbon flux, while net ecosystem carbon exchange (NEE) will regularly fluctuate for 4–5 days during the HW before decreasing. However, ecosystem respiration (Re) and gross ecosystem production (GEP) decline from the beginning of the HW until the end, where Re and GEP will decrease 30% and 50%, respectively. When HWs last five days, water-use efficiency (WUE) will decrease by 26%, soil water content (SWC) by 30% and soil water potential (SWP) will increase by 38%. In addition, the soil temperature will still remain high after the HW although the air temperature will recover to its previous state. Conclusions HWs, as an extreme weather event, have increased during the last two decades in the Songnen meadow steppe. HWs will reduce the carbon flux of the steppe and will cause a sustained impact. Drought may be the main reason why HWs decrease carbon flux. At the later stages of or after a HW, the ecosystem usually lacks water and the soil becomes so hot and dry that it prevents roots from absorbing enough water to maintain their metabolism. This is the main reason why this grassland carbon exchange decreases during and after HWs. [ABSTRACT FROM AUTHOR]

Shallow Posidonia oceanica beds (0 to −15 m), the most common seagrass in the Mediterranean, were mapped from aerial photographs dating from the 1920's and from 2012 along 800 km of coastline in South-Eastern France (Provence-Alpes-Côte-d’Azur region). Changes in P. oceanica bed spatial distribution (limits and extent) during these 85 years were analyzed in terms of concordance (remaining areas), positive discordance (expanding areas) or negative discordance (lost areas). Lost areas were linked with direct or indirect impacts of coastal development (artificialized coastlines (namely harbours, ports of refuge, landfills, artificial beaches, groynes and pontoons, submarine pipelines and aquatic farms) visible on the photographs. The comparison showed that 73% of the shallow limits have declined. Considering spatial extent, remaining seagrass meadows areas accounted for the major part (85%), while lost areas accounted for 13% and expanding areas for 1.1%. Lost areas were mainly linked with artificial coastlines but 44% remained with undetermined causes (invisible pressures and/or mixed effects). The analysis of 96 coastal facilities creating the artificial (namely man-made) coastlines showed that the highest impact over the longest distance (5 km) was caused by harbours. Only artificial beaches had such a distant impact. Pontoons were the least surrounded by lost seagrass meadows areas. These quantitative data offer important information for marine conservation. [ABSTRACT FROM AUTHOR]

Estuaries and coasts are among the most productive ecosystems and constitute valuable habitats for biodiversity and ecosystem services. Amongst nearshore ecosystems, seagrass beds play a major role enhancing biodiversity and water quality. Consequently, the development of new approaches to create extensive and high-resolution habitat maps is required not only to implement conservation, restoration and management plans, but also to establish adaptation plans to face climate change impacts. This study particularly assesses the capability of hyperspectral airborne imagery acquired with Compact Airborne Spectrographic Imager (CASI) to discriminate and map estuarine habitats, with special focus on Zostera noltii seagrass meadows. To this end, 13 habitats were defined along the supralittoral, intertidal and subtidal zones of an estuary, including Z. noltii seagrass meadows. The CASI sensor was configured to acquire 25 bands in the visible and near infrared wavelengths with a ground sampling distance of 2 m. Spectral bands were selected for species discrimination based on the spectral signature of the different habitat classes. Six different band combinations were tested applying maximum likelihood classification algorithm. The most accurate classification was obtained with 10 band combination (a mean producer accuracy 92% and a mean user accuracy 94%). The classification of Z. noltii beds has been found to be restricted to moderate and high dense meadows, however a vegetation index has been defined which could be applied for mapping Z. noltii meadow cover. These results highlight the value of CASI data to discriminate and map estuarine habitats, providing key information to be used in supporting the implementation of environmental legislation, protection and conservation of coastal habitats. [ABSTRACT FROM AUTHOR]

Root morphology and root system architecture of young Posidonia oceanica plants established on two contrasting substrate types, sand and rock, were examined to provide insights into the strategy of adaptation of seagrasses to their environment. After germination, seedlings were planted on sandy patches and on rock within the same area, and survived plants were collected five years later for measurements of the size of the entire root complex and analysis of individual morphological and architectural root traits. Collected plants exhibited up to nine highly intermingled root systems and approx. 2.5 m of total root length. Maximum horizontal extension, total biomass and total length of roots were not significantly affected by substrate. However, on sand roots grew vertically reaching up to 13 cm, while on rock they extended more horizontally and did not penetrate deeper than 5–7 cm leading to the formation of a shallow, densely packed root complex. On rock, the number and the length of second-order laterals on an individual root system were reduced and the topological index higher than on sand (0.8 vs. 0.7) reflecting a more simple (herringbone) branching pattern. Again, root diameter was greater than on sand. The results suggest that P. oceanica can adjust root traits early during plant development according to substrate typology to maximize anchorage and substrate exploration efficiency. This plasticity enables the species to establish and persist also on rocky bottoms which generally prevent establishment of the majority of seagrasses. [ABSTRACT FROM AUTHOR]

Nature–based tourism and recreation activities have a range of environmental impacts, but most protected area agencies have limited capacity to assess them. To prioritise where and what impacts to monitor and manage, we conducted a desktop assessment using Geographical Information Systems (GIS) by combining recreation ecology research with data on visitor usage and key environmental features for a popular protected area used for mountaineering and trekking, Aconcagua Provincial Park (2400–6962 m a.s.l.) in the Andes of Argentina. First, we integrated visitor data from permits with environmental data using GIS. We then identified key impact indicators for different activities based on the recreation ecology literature. Finally, we integrated this data to identify likely ecological impacts based on the types of activities, amount of use and altitudinal zones. Visitors only used 2% of the Park, but use was concentrated in areas of high conservation value including in alpine meadows and glacier lakes. Impacts on water resources were likely to be concentrated in campsites from the intermediate to the nival/glacial zones of the Park while impacts on terrestrial biodiversity were likely to be more severe in the low and intermediate alpine zones (2400–3800 m a.s.l.). These results highlight how visitor data can be used to identify priority areas for on-ground assessment of impacts in key locations. Improvements to the management of visitors in this Park involves more effective ways of dealing with water extraction and human waste in high altitude campsites and the impacts of hikers and pack animals in the low and intermediate alpine zones. [ABSTRACT FROM AUTHOR]

Wet meadows are seasonally saturated wetlands that can develop in arid and semi-arid areas. In the semi-arid region of North Patagonia, Argentina wet meadows are islands of high net primary productivity surrounded by low productivity steppe vegetation. Because of this, Patagonian wet meadows have been heavily grazed by livestock for more than a century. It has been shown that overgrazed wet meadows have lower soil carbon, however, little is known about how overgrazing impacts N dynamics. To this end, we measured ammonium (NH4+), nitrate (NO3-), and total nitrogen (Nt) in paired wet meadows that varied in long-term grazing intensity (heavy vs. light). Results indicate that heavily grazed sites had on average 43% less Nt and 57% less NH4+ than lightly grazed sites. Soil NH4+ concentrations were always significantly greater than NO3- concentrations, being the later often below detection levels. In addition, NH4+ concentrations were correlated with soil moisture in lightly grazed sites, but not in heavily grazed sites. These findings indicate that implementation of better management practices are currently needed to promote more sustainable grazing in semi-arid wet meadows of North Patagonia. [ABSTRACT FROM AUTHOR]

Abstract: Nutrient inputs associated with population growth threaten the integrity of coastal ecosystems. To assess the rapid increase in tourism, we compared the δ15N from Thalassia testudinum collected at sites with different levels of tourism development to detect the N inputs of wastewater discharge (WD) along the coast of Quintana Roo. The contributions of nitrogen enriched in 15N are directly related to the increase of WD inputs in areas of tourism development (Nichupte Lagoon in Cancun) and decreased toward Bahia Akumal and Tulum. The δ15N from T. testudinum was significantly lower at Mahahual and Puerto Morelos. In areas of the lowest development and with tourist activity restricted, such as the Yum Balam Reserve and Sian Ka'an Biosphere Reserve, the δ15N values were relatively enriched compared to Mahahual and Puerto Morelos. Therefore, Puerto Morelos and Mahahual may be used for baseline isotopic monitoring where tourist activities are growing and can lead to environmental pressure on the reef lagoon ecosystem. The anthropogenic N input has the potential to impact, both environmentally and economically, the seagrass meadows and the coral reefs along the coast of Quintana Roo and the Caribbean. [Copyright &y& Elsevier]

Abstract: The European Water Framework Directive (WFD) 2000/60/EC requests the achievement of the Good Status for all surface waters, including the coastal waters, by 2015. In order to check compliance with the needs of Directive, Italian national monitoring data on Posidonia oceanica meadows have been explored and the relationships among the Posidonia Rapid and Easy Index (PREI), and human-induced pressures have been analyzed along the Italian coasts. The aim of this work is to establish functional relationships between a response variable (i.e. the PREI) and a set of potential pressure (i.e. land use, potential organic and nutrient loading, pesticides) and status (i.e. transparency, trophic level and stability of the water column) indicators in a quantitative way. The ecological responses of coastal marine environment have been evaluated using appropriate statistical tools, such as the multiple linear regression analyses and “linear programming” techniques. Results show that more than 70% of the variability of the P. oceanica meadows status, expressed as PREI value, is significantly explained only by a few pressure/status indicators (namely: potential organic load, specific nitrogen load, natural areas extent, water column transparency), among all those initially considered in the model. The application of the proposed model could allow decision makers to better address remedial actions and to achieve the environmental targets proposed by the EU Directives. [Copyright &y& Elsevier]

Abstract: Temporal trends in abundance, demographic structure of the population and secondary production of Siriella clausii were studied at three different sectors of Posidonia oceanica meadows in the SE Iberian Peninsula, with different levels of habitat complexity. Secondary production was calculated through three methods widely employed in marine invertebrates: the Hynes method (based on demographic structure data) and models by Morin-Bourassa and Brey (based on biomass data). This filter/grazer and detritus feeder is the most abundant mysid in P. oceanica seagrass meadows in the Mediterranean. The population structure was similar in the three sectors, but the temporal pattern of abundance was different, at times even opposite. This pattern may be related to the aggregated spatial distribution, metapopulation dynamics or stochastic factors, but other potential factors could be involved, such as habitat features or predation rates. The values of production oscillated between 25 and 60 mgAFDW/m2/year, depending on the calculation method that was applied, and showed differences between sites and seagrass complexity. The present values are intermediate between those characterising highly productive systems, such as estuaries, and systems of limited productivity (bathyal habitats). Compared to other peracarids, mysid production is greater than that of isopods and less than amphipod production. This is possibly related to the life cycle and reproductive strategies. Detritus feeders such as S. clausii may play an important trophic role due their capacity to use as food the biomass associated to detritus, which constitutes larges reservoirs of carbon derived from seagrass primary production. [Copyright &y& Elsevier]

Abstract: Understanding what controls the capacity of a coastal lagoon ecosystem to recover following climatic and anthropogenic perturbations and how these perturbations can alter this capacity is critical to efficient environmental management. The goal of this study was to examine the resilience and stability of Cymodocea nodosa-dominated seagrass meadows in Urbino lagoon (Corsica, Mediterranean Sea) by characterizing the spatio-temporal dynamics of seagrass meadows over a 40-year period and comparing (anthropogenic and climatic) environmental fluctuations. The spatio-temporal evolution of seagrass meadows was investigated using previous maps (1973, 1979, 1990, 1994, 1996, 1999) and a 2011 map realized by aerial photography–remote sensing combined with GIS technology. Environmental fluctuation was investigated via physical-chemical parameters (rainfall, water temperature, salinity, turbidity, dissolved oxygen) and human-impact changes (aquaculture, artificial channel). The results showed a severe decline (estimated at −49%) in seagrass meadows between 1973 and 1994 followed by a period of strong recovery (estimated to +42%) between 1994 and 2011. Increased turbidity, induced either by rainfall events, dredging or phytoplankton growth, emerged as the most important driver of the spatio-temporal evolution of Cymodocea nodosa-dominated meadows in Urbino lagoon over the last four decades. Climate events associated to increased turbidity and reduced salinity and temperature could heavily impact seagrass dynamics. This study shows that Urbino lagoon, a system relatively untouched by human impact, shelters seagrass meadows that exhibit high resilience and stability. [Copyright &y& Elsevier]

In Southeast Asia, seagrass meadows are under threat through coastal development and increased pollution, but remain understudied. The dugong is a marine herbivore that is dependent on the availability of seagrass as a primary food source. In this study, we assess the patterns of co-occurrence between dugongs and seagrass. We hypothesize that the changing spatial patterns of dugong feeding are positively correlated to the seasonal variation in distribution and abundance of mixed species in subtidal tropical seagrass meadows. We documented seagrass cover and dugong feeding trails in the Sibu Archipelago meadow in Johor, Malaysia, across the monsoon seasons of 2016–2017 using an underwater towed video method. Moran's I and Getis-Ord G i * statistics were used to quantify the degree of clustering in feeding trails, feeding patch size, and to identify feeding hotspots and coldspots. This site has the single largest subtidal meadow in Peninsular Malaysia known to date, measuring 12.88 km2. The study captured a reduction in seagrass extent and coverage during the study. Feeding trail occurrence averaged three per image throughout the seasons, with the maximum number being 14 trails per image. Dugongs fed in a spatially clustered manner leaving two distinct feeding trail patterns: (1) a dispersed pattern when seagrass cover was high or low (76–100% and 0–25%) that resulted in larger patch sizes, and (2) a concentrated pattern in moderate seagrass cover (26–75%) that resulted in smaller patch size. Feeding hotspots and coldspots had significantly different seagrass cover, suggesting that dugongs foraged strategically within the meadow. Our results demonstrate that seagrass cover played a significant role in driving dugong feeding patterns and in creating feeding hotspots and coldspots in tropical subtidal meadows. • The largest seagrass meadow in Malaysia undergoes dramatic changes in cover and extent. • Underwater towed video method captures spatial patterns of dugong feeding. • Dugong feeding patterns in the subtidal meadow changes in response to seagrass cover. • Seagrass cover influences the locations of dugong feeding hotspots and coldspots. • Dugongs in the Sibu Archipelago consumed Halophila ovalis and Halodule uninervis. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) has a variety of vegetation types that range from alpine tundra to tropic evergreen forest, which play an important role in the global carbon (C) cycle and is extremely vulnerable to climate change. The vegetation C uptake is crucial to the ecosystem C sequestration. Moreover, net reduction in vegetation C uptake (NRVCU) will strongly affect the C balance of terrestrial ecosystem. Until now, there is limited knowledge on the recovery process of vegetation net C uptake and the spatial-temporal patterns of NRVCU after the disturbance that caused by climate change and human activities. Here, we used the MODIS-derived net primary production to characterize the spatial-temporal patterns of NRVCU. We further explored the influence factors of the net reduction rate in vegetation C uptake (NRRVCU) and recovery processes of vegetation net C uptake across a unique gradient zone on the TP. Results showed that the total net reduction amount of vegetation C uptake gradually decreased from 2000 to 2015 on the TP (Slope = −0.002, P < 0.05). Specifically, an increasing gradient zone of multi-year average of net reduction rate in vegetation carbon uptake (MYANRRVCU) from east to west was observed. In addition, we found that the recovery of vegetation net C uptake after the disturbance caused by climate change and anthropogenic disturbance in the gradient zone were primarily dominated by precipitation and temperature. The findings revealed that the effects of climate change on MYANRRVCU and vegetation net C uptake recovery differed significantly across geographical space and vegetation types. Our results highlight that the biogeographic characteristics of the TP should be considered for combating future climate change. • An increasing gradient zone of net reduction rate in vegetation C uptake from east to west on TP was observed. • Vegetation C uptake recovery differs significantly across geographical space and vegetation types. • The recovery time to normal levels of vegetation C uptake was differed between alpine steppes and meadows. • Restoration of alpine steppes and alpine meadows were primarily dominated by precipitation and temperature, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The seasonal dynamics of the molluscan fauna associated with the westernmost populations of the Mediterranean seagrass Posidonia oceanica, has been studied throughout an annual cycle in the northwestern coasts of the Alboran Sea. Samples were collected seasonally (5 replicated per season) using a non-destructive sampling technique (airlift sampler) on quadrats of 50 × 50 cm at 2 sites located 7 km apart. Several environmental variables from the water column (temperature, chlorophyll a), the sediment (percentage of organic matter) and the seagrass meadows (shoot density, leaf height and width, number of leaves per shoot) were also measured in order to elucidate their relationships with the dynamics of the molluscan assemblages. In these meadows, a total of 17,416 individuals of molluscs were collected, belonging to 71 families and 171 species, being Rissoidae, Pyramidellidae and Trochidae the best-represented families, and Mytilidae, Nassaridae and Trochidae the dominant ones in terms of abundance. The assemblages were dominated by micro-algal grazers, filter feeders and ectoparasites (including those feeding on sessile preys). The species richness and the abundance displayed significant maximum values in summer, whereas evenness and diversity displayed maximum values in spring, being significant for the evenness. Both abundance and species richness values were positively correlated to seawater temperature and percentage organic matter, only for the latter, and negatively to leaf width. Significant seasonal groupings were obtained with multivariate analyses (MDS, Cluster, ANOSIM) using qualitative and quantitative data that could be mainly related to biological aspects (i.e. recruitment) of single species. The molluscan assemblages are influenced by the biogeographical location of the area (Alboran Sea), reflected in the absence or scarcity of most Mediterranean species strictly associated with P. oceanica (e.g. Tricolia speciosa, Rissoa ventricosa) and by the occurrence of subtropical fauna (e.g. Ungulina cuneata). The patchiness of the meadows, intercalated in other habitats like photophilous algae, and the strong hydrodynamism resulting from the unusually shallow setting, may promote the movement of species between these habitats and the seagrass and therefore enhance the species richness. This large faunistic list for the molluscan fauna associated with P. oceanica is therefore different than those observed in other meadows, and highlights the conservation value of these fragmented meadows located in their western distributional limit. [Copyright &y& Elsevier]

Abstract: Secondary metabolites play an important role in protecting plants from herbivores or pathogens. Despite this, few studies have investigated the presence and the concentration of those compounds over broad spatial scales in seagrasses. Here we analysed the presence and abundance of specific phenolic compounds of Zostera noltii from four different meadows located across the Atlantic and the Mediterranean coast. Three phenolic acids have been found in the samples of Z. noltii: rosmarinic, caffeic and zosteric acids. The proportion of the three compounds varied substantially with the major proportion comprising rosmarinic acid (RA, mean value 94%) followed by zosteric acid (ZA, mean value 4%) and caffeic acid (CAF, mean value 2%). Z. noltii metabolic compounds varied notably between sites. The highest concentrations in RA were found in the Cadiz Bay with values of 11,254 (55 SD) μg g−1 dry wt, while the lowest were observed in the Alfacs Bay (Ebro) with values of 823 (7 SD) μg g−1 dry wt. The highest concentrations in ZA were also observed in the Cadiz Bay with values of 727 (6 SD) μg g−1 dry wt, while the lowest were observed in the Sa Nitja Bay (Menorca Island) with values of 20 (4 SD) μg g−1 dry wt. Finally, the concentrations in CAF remain very low at each site (17–69 μg g−1 dry wt), with the lowest observed in Arcachon. Their proportions remained relatively constant, indicating that most phenolic acids responded together. Documenting the presence of those compounds in living tissues of Z. noltii and how they vary in abundance between seagrass meadows across large geographical scales is a crucial first step to understand the large-scale level response of the plant to potential pathogens, herbivore outbreaks or other ecological processes. [Copyright &y& Elsevier]

Abstract: The rhizophyte alga Caulerpa prolifera thrives in dense monospecific stands in the vicinity of meadows of the seagrass Cymodocea nodosa in Cadiz Bay Natural Park. The seasonal cycle of demographic and biometric properties, photosynthesis, and elemental composition (C:N:P) of this species were monitored bimonthly from March 2004 to March 2005. The number of primary assimilators peaked in spring as consequence of the new recruitment, reaching densities up to 104 assimilators·m−2. A second peak was recorded in late summer, with a further decrease towards autumn and winter. Despite this summer maximum, aboveground biomass followed a unimodal pattern, with a spring peak about 400 g dry weight·m−2. In conjunction to demographic properties of the population, a detailed biometric analysis showed that the percentage of assimilators bearing proliferations and the number of proliferations per assimilator were maximal in spring (100% and c.a. 17, respectively), and decreased towards summer and autumn. The size of the primary assimilators was minimal in spring (May) as a result of the new recruitments. However, the frond area per metre of stolon peaked in early spring and decreased towards the remainder of the year. The thallus area index (TAI) was computed from two different, independent approaches which both produced similar results, with a maximum TAI recorded in spring (transient values up to 18 m2·m−2). The relative contribution of primary assimilators and proliferations to TAI was also assessed. Whereas the number of proliferations accounted for most of the TAI peak in spring, its contribution decreased during the year, to a minimum in winter, where primary assimilators were the main contributors to TAI. The present study represents the first report of the seasonal dynamics of C. prolifera in south Atlantic Spanish coasts, and indicates the important contribution of this primary producer in shallow coastal ecosystems. [Copyright &y& Elsevier]

Abstract: Nutrient increases in coastal systems are becoming a world-wide concern since they promote strong structural and functional changes in shallow ecosystems. Increased nutrient availability in the water column may strongly enhance the leaf epiphytic communities of key habitat-forming species such as seagrasses through a bottom-up mechanism, competing for light and nutrients with the leaves. Epiphytes support an abundant and diverse community of resident invertebrates which fuel higher trophic levels in Posidonia oceanica food webs. We evaluated the response of seagrass, epiphytes and the invertebrate community to an experimental increase of water column nutrient availability. Nutrient increase was followed by a rise of epiphyte biomass. The increase in epiphytic biomass promoted invertebrate abundance, but appeared to have negative effects on P. oceanica shoot size. On the other hand, the increase in invertebrate abundance did not seem to control epiphytic biomass, which was not reversed to pre-nutrient enrichment levels. This work suggests that the abundance of invertebrate populations is limited by epiphyte biomass, through food or habitat provision, in P. oceanica systems and points to nutrients as the main driver of epiphyte biomass during summer. The results illustrate the control mechanisms at community level in P. oceanica meadows and the possible responses of a threatened ecosystem to human impact such as eutrophication. [Copyright &y& Elsevier]