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The development of indices of ecosystem quality makes it possible to obtain robust information with less human and material effort. These indices are especially useful for assessing the quality of ecosystems disturbed by anthropogenic impact since they can inform management decisions designed to recover their functionality. The abandonment of agricultural activity is a major environmental challenge, and it is important to understand its consequences on ecosystem functioning. The main objective of this work was to develop a robust quality index of abandoned agrosystems based on detailed information on soil properties and structure and the composition of the vegetation. A chronosequence was built of abandoned vineyards over the last 60 years. Seventeen soil physical-chemical properties and ten enzymatic activities related to the cycles of C, N, P and S were determined in 21 plots along the chronosequence. Total vegetation cover, cover of cryptograms and phanerogams and cover of plant functional groups was also recorded. The main factors involved in the quality of the ecosystem were detected by means of network analyses based on these variables. Models were then developed to calculate ecosystem quality indices. Our results showed how the evolution of soil properties occurred simultaneously with variations in the composition and structure of the vegetation. The major factors that determined the functionality of abandoned agrosystems were the quantity and quality of soil organic matter (high TOC and WHN) and the lesser abundance of sulphur accumulator plants. The ecosystem quality index model found to be the most robust was the index with integration by weights and non-linear scores, which followed a sigmoid pattern throughout the chronosequence. Our results highlight the importance of developing robust quality indices based on an interdisciplinary approach.

Associated with the introduction of alien species in a new area, interactions with other native species within the recipient community occur, reshaping the original community and resulting in a unique assemblage. Yet, the differences in community assemblage between native and invaded ranges remain unclear. Mediterranean grasslands provide an excellent scenario to study community assembly following transcontinental naturalisation of plant species. Here, we compared the community resemblance of plant communities in Mediterranean grasslands from both the native (Spain) and invaded (Chile) ranges. We used a novel approach, based on network analysis applied to co-occurrence analysis in plant communities, allowing us to study the co-existence of native and alien species in central Chile. This useful methodology is presented as a step forward in invasion ecology studies and conservation strategies. We found that community structure differed between the native and the invaded range, with alien species displaying a higher number of connections and, therefore, acting as keystones to sustain the structure within the invaded community. Alien species acting like keystones within the Chilean grassland communities might exacerbate the threat posed by biological invasions for the native biodiversity assets. Controlling the spread of the alien species identified here as keystones should help managing potential invasion in surrounding areas. Network analyses is a free, easy-to-implement and straightforward visual tool that can be widely used to reveal shifts in native communities and elucidate the role of multiple invaders into communities. [ABSTRACT FROM AUTHOR]

European abandoned lands have been increasing in recent decades, and this is occurring in a climate change scenario in which the consequences of their interactions are still little known. We tested the hypothesis that the functionality of abandoned lands responds differently to year‐to‐year climate variations depending on the time since the cessation of agricultural activity. We constructed a chronosequence in Mediterranean abandoned vineyards at six different years of abandonment in 2016 (1, 3, 7, 11, 25, 40), in a current vineyard and in land not dedicated to vineyards. Soil total organic carbon (TOC), total nitrogen (TN) and available nutrients, enzyme activities relating to the main macronutrient cycles and plant‐community attributes were studied at 24 sites over three consecutive years. A total of 144 samplings were performed. TOC, TN, most enzyme activities and plant species density increased throughout the chronosequence, although interannual climate variability also had a significant influence. The extreme drought event increased the activity of enzymes related to the carbon (C) and nitrogen (N) cycle, as well as the stock of TOC after a subsequent decrease in TOC when environmental conditions became favourable. In contrast, plant species density and the cover of certain plant functional traits such as mycorrhizal symbiotic plants (Cistaceae) and N‐fixers (Fabaceae) decreased significantly. Our results also demonstrated that extreme drought events had a higher negative impact on lands that had been abandoned for longer. We therefore conclude that extreme drought events damage the functionality of Mediterranean abandoned agrosystems, thus affecting all its compartments and jeopardising its functionality. [ABSTRACT FROM AUTHOR]

This work compares the net revenues of maintaining grasslands versus shrublands as part of the habitat of the Cervus elaphus big game species in Mediterranean agroforestry ecosystems. For this purpose, data published by the Regional Government of Andalusia (SW Spain) were used to analyze revenues and expenditures under two scenarios: an optimistic one and a pessimistic one. Revenue is generated from both the value of game trophies and the sale of meat. In the grasslands option, expenditure is associated with the need to supply supplemental food since, unlike shrublands, Mediterranean grasslands do not produce forage crops during the summer months. To analyze the expenditure of supplemental feeding, monthly market prices for corn grain in the province of Cordoba (this province covers an area of almost 1.4 million hectares) were obtained for the period 2015–2019. Our results show that, in net revenues terms, substituting shrublands for grasslands is not always the best option under the conditions analyzed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil and vegetation properties evolve simultaneously in abandoned lands. • An ecosystem quality index (EQI) based on soil and vegetation is successfully assayed. • Soil organic matter and sulphur-accumulator plants had most weight in EQI calculation. • EQI followed a sigmoid pattern throughout the ecosystem functionality recovering. The development of indices of ecosystem quality makes it possible to obtain robust information with less human and material effort. These indices are especially useful for assessing the quality of ecosystems disturbed by anthropogenic impact since they can inform management decisions designed to recover their functionality. The abandonment of agricultural activity is a major environmental challenge, and it is important to understand its consequences on ecosystem functioning. The main objective of this work was to develop a robust quality index of abandoned agrosystems based on detailed information on soil properties and structure and the composition of the vegetation. A chronosequence was built of abandoned vineyards over the last 60 years. Seventeen soil physical-chemical properties and ten enzymatic activities related to the cycles of C, N, P and S were determined in 21 plots along the chronosequence. Total vegetation cover, cover of cryptograms and phanerogams and cover of plant functional groups was also recorded. The main factors involved in the quality of the ecosystem were detected by means of network analyses based on these variables. Models were then developed to calculate ecosystem quality indices. Our results showed how the evolution of soil properties occurred simultaneously with variations in the composition and structure of the vegetation. The major factors that determined the functionality of abandoned agrosystems were the quantity and quality of soil organic matter (high TOC and WHN) and the lesser abundance of sulphur accumulator plants. The ecosystem quality index model found to be the most robust was the index with integration by weights and non-linear scores, which followed a sigmoid pattern throughout the chronosequence. Our results highlight the importance of developing robust quality indices based on an interdisciplinary approach. [ABSTRACT FROM AUTHOR]

Climate change-induced alterations to precipitation may affect the regeneration dynamics of plant species, with the occurrence of drought influencing germination and seedling establishment. In Mediterranean grasslands, typically dominated by C3 annual species, germination occurs rapidly once sufficient rain falls in autumn. However, a single large precipitation event may be followed by a dry spell, with possible consequences for vegetation composition and productivity. We investigated the effects of autumn-time drought on germination and seedling establishment, and the subsequent recovery potential, in semi-natural and sown pastures. Although the majority of grasslands in Portugal are semi-natural, sowing legume-rich seed mixtures is an increasingly common agricultural practice in Portugal. Our results show an overwhelming effect of autumn-time drought on seedling establishment, with the semi-natural pasture being more compromised than the sown pasture. However, after the recovery period, the semi-natural pasture exhibited tendentially higher aboveground biomass recovery than the sown pasture. The differential species sensitivity to autumn-time drought and subsequent implications for recovery potential may be important for the agricultural practice of sown pastures, justifying additional research for drought-tolerant cultivar improvement to maintain productivity with climate change. [ABSTRACT FROM AUTHOR]

The introduction of exotic species to new regions offers opportunities to test fundamental questions in ecology, such as the context-dependency of community structure and assembly. Annual grasslands provide a model system of a major unidirectional introduction of plant species from Europe to North America. We compared the community structure of grasslands in two Mediterranean regions by surveying plots in Spain and in California with similar environmental and management conditions. All species found in Spanish grasslands were native to Spain, and over half of them (74 of 139 species) are known to have colonized California. In contrast, in California, over half of the species (52 of 95 species) were exotic species, all of them native to Spain. Nineteen species were found in multiple plots in both regions (i.e., shared species). The abundance of shared species in California was either similar to (13 species) or greater than (6 species) in Spain. In California, plants considered pests were more likely than non-pest species to have higher abundance. Co-occurring shared species tended to maintain their relative abundance in native and introduced communities, which indicates that pools of exotic species might assemble similarly at home and away. These findings provide interesting insights into community assembly in novel ecosystems. They also highlight an example of startling global and local floristic homogenization.

A characteristic butterfly of Asian steppes, Proterebia afra (Fabricius 1787), was studied in its two relic areas of occurrence within the Balkans-the Askion Mts (a single mountain massif in NW Greece) and Dalmatia (karstic inland S Croatia)-together with co-occurring butterfly communities during its early spring adult flight period. P. afra adults tolerate harsh continental conditions prevailing at its localities during its flight. Local densities were higher in the Askion Mts (up to 100 individuals per 50 m walk) than in Dalmatia (up to 30 individuals per 50 m). Within both areas of occurrence, it inhabits dry grasslands subject to intermediate grazing pressure that retains enough dry grass litter but still suppresses shrubs and trees. Hotter slopes are preferred in more northerly Dalmatia than in the more southerly Askion Mts. More co-occurring butterfly species and more Mediterranean species were recorded in the Askion Mts (69 vs 63; 23 vs 12), but more butterfly individuals and higher species' richness per transect were observed in Dalmatia. In ordination analyses, the main gradients organising the grassland butterfly communities distinguished between grassy plains and rocky slopes containing more woody plants. Given the distribution extents, local densities and present land use conditions, the Balkan P. afra is not currently endangered, but this may swiftly change with grazing abandonment, especially in Dalmatia, and some conservation actions should be considered in the near future. [ABSTRACT FROM AUTHOR]

• Drought reduced soil macroaggregates causing the loss of soil structural stability. • Following drought, macroaggregate disruption leaded to unprotect soil organic matter which increased C mineralization. • Abandoned time increased macroaggregates and soil structural stability. • Drought caused more loss on soil carbon stock in longer time abandoned lands. Climate change is causing an increase in the frequency and severity of drought, and this has a significant influence on the global C cycle as soils are the main sink for C in terrestrial ecosystems. Drought can have serious consequences for the structural stability of the soil, which influences the protection of the organic matter stored in the soils and hence its mineralization. In this work we study the effects of an extreme drought event on the structural stability of the soil in Mediterranean annual grasslands developed after the abandonment of agricultural activity. This was done by building a chronosequence of abandoned vineyards and determining the changes in the stability of the soil aggregates and organic matter by monitoring these parameters for three consecutive years in permanent plots with different ages of abandonment. This period of time included an extreme drought event in the second year with a strong positive thermal anomaly, which caused a serious structural destabilization of the soil and had a major impact on the soil C and N cycles. The breakdown of the soil aggregates left unprotected a large amount of organic substrates that were rapidly mineralized when the environmental conditions were favourable for soil biological activity. This had significant repercussions on the functioning of these abandoned ecosystems, which became sources of atmospheric CO 2 , when under normal conditions they act as C sinks. Furthermore, the effects of this extreme event were more severe in the plots with longer periods of abandonment, which have the highest amount of C accumulated in the soil. [ABSTRACT FROM AUTHOR]

Secondary grasslands are one of the most common vegetation types worldwide. In Europe, and in the Mediterranean basin, human activities have transformed many woodlands into secondary grasslands. Despite their recognized role in the global carbon cycle, very few data are available for estimating the biomass of Mediterranean grasslands. We developed linear regression models in order to predict the biomass of two native Mediterranean grasses (Ampelodesmos mauritanicus and Hyparrhenia hirta) and an invasive alien grass (Pennisetum setaceum). Ampelodesmos mauritanicus is very common throughout the Mediterranean basin, mostly on north-facing slopes, H. hirta characterizes thermo-xeric grasslands, while P. setaceum is an alien species that is rapidly spreading along coastal areas. The measured morphometric attributes of individual plants as potential predictors were considered. The validation results corroborate the ability of the established models to predict above ground and total biomass of A. mauritanicus and P. setaceum. We also evaluated the total biomass per hectare for each species. The highest biomass per hectare was found for A. mauritanicus, whereas biomass was higher for H. hirta than for P. setaceum. The replacement of H. hirta by P. setaceum may reduce the total carbon storage in the ecosystem; however, P. setaceum allocates more resources to the roots, thus increasing the more stable and durable pool of carbon in grasslands.

Scarce information is available on the biological reasons why a small subset of introduced species can effectively establish within novel ecosystems. A comparison of early growth traits can help to explain the better performance of alien invasive species versus native co-occurring species. In one year-long experiment, we compared the early life stages of Ampelodesmos mauritanicus (Poir.) Dur. & Schinz ( Amp ), a native perennial Mediterranean grass, and Pennisetum setaceum (Forssk.) Chiov ( Penn ), an emerging invader grass in sub-arid and Mediterranean-climate areas. The Penn seedlings grew significantly faster and were approximately 2.5 times taller than the Amp seedlings, reaching a final average height of 90 cm. The shoot and root dry masses of the Penn seedlings were, respectively, more than 14 times and 4 times higher than those of the Amp seedlings. As a consequence, the shoot:root ratio was significantly higher in Penn , which resulted in a greater allocation of resources to the photosynthetic organs. Penn showed a more rapid life cycle compared with Amp . Penn produced seeds 9 months after sowing while no spikelet was produced by Amp until the end of the experiment. As a consequence, Penn may gain a reproductive advantage due to rapid seed dissemination. Ultimately, a suite of peculiar early growth traits makes Penn an aggressive competitor against Amp , which is an important floristic element of native Mediterranean grasslands. Penn seems better suited than Amp in colonizing frequently disturbed sites with fluctuating resource availability or irregular rainfall distribution and Penn is gradually replacing Amp . [ABSTRACT FROM AUTHOR]

Despite their ecological, economic and social importance, grasslands in areas with Mediterranean climates continue to receive limited scientific, political and media attention. The main objectives of this review are to compare and contrast dryland grasslands in the 'Old World' regions of the Mediterranean basin (southern Europe, western Asia and North Africa) with those of 'New World' regions with Mediterranean climates (Australia and Chile) and to identify common research priorities. The common characteristics and differences in climate, soils, native vegetation, importance of the livestock sector and the socio-economic background for the different Mediterranean environments are examined. Past trends and the current status of temporary and permanent Mediterranean grasslands are also described. Some common issues between these regions are as follows: (i) adaptation to climate change; (ii) increasing persistence and drought survival of both annual and perennial species; (iii) the important role of forage legumes; (iv) maintaining grassland plant diversity; and (v) improved ecosystem services, such as carbon sequestration, control of soil erosion and wildfires, and preservation of both wild and domestic biodiversity. The favourable climate in these regions, which allows year-round grazing and the growth of legumes, should be exploited to improve the sustainability of grassland-based, extensive farming systems and the quality of their animal products, while at the same time improving ecosystem services. The decreasing support for grassland research and development programmes requires increased international scientific and technical cooperation among the few institutions operating in the different Mediterranean-climate areas of the World to provide innovative and sustainable solutions to farmers. [ABSTRACT FROM AUTHOR]

Projected changes in climate are expected to have widespread effects on plant community composition and diversity in coming decades. However, multisite, multifactor climate manipulation studies that have examined whether observed responses are regionally consistent and whether multiple climate perturbations are interdependent are rare. Using such an experiment, we quantified how warming and increased precipitation intensity affect the relative dominance of plant functional groups and diversity across a broad climate gradient of Mediterranean prairies. We implemented a fully factorial climate manipulation of warming (+2.5-3.0 °C) and increased wet-season precipitation (+20%) at three sites across a 520-km latitudinal gradient in the Pacific Northwest, USA. After seeding with a nearly identical mix of native species at all sites, we measured plant community composition (i.e., cover, richness, and diversity), temperature, and soil moisture for 3 years. Warming and the resultant drying of soils altered plant community composition, decreased native diversity, and increased total cover, with warmed northern communities becoming more similar to communities further south. In particular, after two full years of warming, annual cover increased and forb cover decreased at all sites mirroring the natural biogeographic pattern. This suggests that the extant climate gradient of increasing heat and drought severity is responsible for a large part of the observed biogeographic pattern of increasing annual invasion in US West Coast prairies as one moves further south. Additional precipitation during the rainy season did little to relieve drought stress and had minimal effects on plant community composition. Our results suggest that the projected increase in drought severity (i.e., hotter, drier summers) in Pacific Northwest prairies may lead to increased invasion by annuals and a loss of forbs, similar to what has been observed in central and southern California, resulting in novel species assemblages and shifts in functional composition, which in turn may alter ecosystem functions. [ABSTRACT FROM AUTHOR]

The construction of solar parks leads to soil degradation and the destruction of vegetation. Solar panels change the microclimate affecting plant survival and vegetation development. The increasing solar energy production requires solutions for ecological restoration from the beginning of electricity production. We compared three methods to restore Mediterranean dry grasslands as a target community not affecting solar energy production: seed material transfer, sowing of the target species Brachypodium retusum and an increase in soil organic matter by compost addition. The experiment was set up in a solar park located in South-Eastern France, both outside and below solar panels (SP). After four years, seed material transfer was the best method to initiate plant succession towards the reference community. SP hampered restoration success and strongly reduced plant species richness, in particular of species from the reference community. B. retusum survival decreased by 50% and phytometabolic indices revealed a light stress under SP. However, the species still maintained growth similar to plants outside SP suggesting shade tolerance. Long-term monitoring is required to evaluate whether communities better adapted to light reduction under panels need to be taken into account for successful restoration. • Seed material transfer material was the most effective restoration technique. • Solar panels hampered plant succession towards the reference state. • Solar panels reduced plant species richness in all treatments. • Stress and mortality of the target species B. retusum increased under solar panels. [ABSTRACT FROM AUTHOR]

Changes in species richness along the ecological succession gradient may be strongly determined by coexisting extinction debts of species from the original habitats and colonization credits of those from the replacing habitats. The magnitude of these processes and their causes remain largely unknown. We explored the extinction debt and colonization credit for grassland and forest specialist plants, respectively, and the local and landscape factors associated to the richness of these species groups in a 50-year process of forest encroachment into semi-natural Mediterranean grasslands. A set of sampling plots of persistent grasslands and forests and their transitional habitat (wooded grasslands) was selected within fixed-area sites distributed across the landscape. Our results confirm the extinction debt and suggest colonization credit (according to observed trends and model predictions) in wooded grasslands when compared to persistent forests, despite wooded grasslands and persistent forests having similar tree cover. Grassland connectivity and solar radiation had opposing effects on the richness of both grassland and forest specialists, and it is possible that the availability of seed sources from old forests may have accelerate the payment of colonization credit in the wooded grasslands. These results suggest that extinction debt and colonization credit have driven species turnover during the 50 years of forest encroachment, but at different rates, and that local and landscape factors have opposing effects on these two phenomena. They also highlight the importance of documenting biodiversity time lags following habitat change when they are still in progress in order to timely and adequately manage habitats of high conservation value such as the grasslands studied here. [ABSTRACT FROM AUTHOR]

The soils of many abandoned mine sites in the central region of Spain are heavily polluted with a number of different metals. Having frequently found Agrostis castellana growing at these old mine sites, this study was designed to assess its remediation capacity for this type of setting. In an initial field study, plant specimens were collected from 4 abandoned mine sites to determine pollutant concentrations in their roots and shoots. This was followed by a 4-year bioassay in a controlled environment in which soils collected from the mines were used to set up microcosms. Maximum root concentrations of the most polluting elements present in the bioassay were 3625 mg kg-1 Zn, 2793 mg kg-1 Cu, 13042 mg kg-1 Pb, 49 mg kg-1 Cd and 957 mg kg-1 As. These concentrations represent root bioaccumulation indices of over 1 and usually >2. In contrast, indices of transfer to above-ground phytomass were always < 1, indicating this species is a good candidate for use as a phytostabilizer. However, the high metal concentrations that could reach the above-ground mass of this plant determines a need for close monitoring and avoiding the use of areas under restoration for hunting or grazing. [ABSTRACT FROM AUTHOR]

In central Chile, many exotic species associated with cereal culture and livestock activities were introduced during Spanish colonization. Nowadays, Chilean semi-natural grasslands are a mixture of native species and exotics that mainly originated in the Mediterranean Basin. The establishment and persistence of exotics (i.e. naturalization) can be due to abiotic (climate and soil properties) and biotic (interaction between plants) factors. We assess the importance of these environmental factors as filters that have promoted/limited the successful naturalization of Spanish species in Chile. Fifteen sites distributed throughout a wide range of Mediterranean climatic conditions, with similar geomorphology and land-use, were selected in both Chile and Spain. At each site we recorded a broad set of soil and climate variables as well as plant species richness during two consecutive years. In Chile, species were classified as natives or exotics whereas in Spain species were classified as colonizers (species that have been naturalized in Chile) or exclusives (only present in Spain). Species richness was higher in Spain (229 species) than in Chile (152), the latter with a high proportion (almost 50 %) of exotics. Different environmental factors affected species richness in each Mediterranean region. In Spain, species classified as colonizers were weakly related to a combination of soil and climate properties, while in Chile the number of exotic species was highly related with climate conditions (especially water availability). Lack of association between native and exotic species richness indicated that biotic filters (i.e. species competition) are less important than abiotic ones in transcontinental naturalization in Chile. [ABSTRACT FROM AUTHOR]

Ecologists use approaches based on plant functional traits to tackle several fundamental and applied questions. Although a perfect characterization of functional trait structure requires the measurement of all the individuals in communities, this is prohibitively resource-consuming. Consequently, the general practice is to average the trait values of a reduced number of individuals per species. However, there are different alternatives regarding the number, identity and spatial location of the individuals chosen to calculate species-averaged trait values., In this study, we compared different strategies for sampling functional traits, using community-weighted mean trait values (CWM) and the Rao index of functional diversity (FD). We intensively sampled the functional trait structure along a topographical gradient in a Mediterranean grassland, obtaining accurate estimations of the 'real' values of these indices (CWMI and FDI) for three traits (height, leaf area and specific leaf area)., We simulated three different sampling strategies differing in the spatial location of the individuals used to estimate species-mean trait: (i) average of the whole gradient (GLO), (ii) average of the sampling unit in which the abundances of species maximize (MAX) and (iii) average of a reduced number of individuals per species and sampling unit (LOC). For each strategy, we simulated different sampling intensities (number of individuals sampled)., For each trait, we examined the ability of each strategy and sampling intensity to accurately estimate CWMI and FDI, as well as their ability to detect changes in functional trait structure along the topographical gradient., LOC outperformed the other strategies in terms of accuracy and bias, and was much more efficient to describe changes along the gradient, regardless of the traits and indicators considered. Furthermore, LOC was the only strategy that improved consistently as sampling intensity increased, especially at low levels of intensity., Our results indicate that the impact of considering intraspecific variability in trait values can be greater than commonly assumed. Strategies that neglect this source of variability can result in inaccurate or biased estimations of the functional trait structure of plant communities. Most importantly, we show that intraspecific variability can be taken into consideration without any increases in the total number of individuals measured. [ABSTRACT FROM AUTHOR]

A study was conducted on the effect of tropospheric ozone ( O3) on soft brome ( Bromus hordeaceus) and the modulation of its response by nitrogen ( N). Two assays were conducted using open-top chambers ( OTCs). Three O3 treatments were considered: filtered air, with concentrations below background levels (charcoal-filtered air), non-filtered air ( NFA) that simulates ambient O3 concentrations, and unfiltered air to which 40 nL L−1 O3 above-ambient concentrations was added ( NFA+), simulating elevated values recorded in natural areas of annual pastures in the Iberian Peninsula. Three N rates were used, simulating the increase in soil N through atmospheric deposition and excreta from livestock grazing. Ozone caused an augmentation in foliar senescence, whereas green biomass was not altered; consequently, an increased senescent/green biomass ratio was produced. A stronger O3 effect was detected in the second assay compared with the first. This was related to the estimated absorbed O3 fluxes, which were double the value calculated in the former. Increasing N input enhanced biomass production, but its effectiveness was greater in the first assay, under less-favourable weather conditions and lower plant growth. In the first assay, the O3 response was modulated by N availability, which mitigated the effects of O3 to medium concentration values. In the first assay, O3 reduced the aerial/subterranean biomass ratio, caused by a positive-trend effect on roots. Foliar concentration of lignin was increased by O3, and in vitro digestibility of aerial biomass and the plant cell wall fraction tended to decrease with increasing O3. [ABSTRACT FROM AUTHOR]

Species diversity has two components - number of species and spatial turnover in species composition (beta-diversity). Using a field experiment focusing on a system of Mediterranean grasslands, we show that interspecific competition may influence the two components in the same direction or in opposite directions, depending on whether competitive exclusions are deterministic or stochastic. Deterministic exclusions reduce both patch-scale richness and beta-diversity, thereby homogenising the community. Stochastic extinctions reduce richness at the patch scale, but increase the differences in species composition among patches. These results indicate that studies of competitive effects on beta diversity may help to distinguish between deterministic and stochastic components of competitive exclusion. Such distinction is crucial for understanding the causal relationship between competition and species diversity, one of the oldest and most fundamental questions in ecology. [ABSTRACT FROM AUTHOR]

Quantifying species relative abundances in plant communities remains a key issue for the assessment of community functional structure. This is particularly challenging when non-destructive estimates are required over time. We tested whether the point intercept method (PIM), originally developed for low-diverse communities, is relevant for assessing the aboveground biomass and functional structure of highly diverse, low-productive Mediterranean grasslands. We sampled 18 communities with the PIM along a gradient of soil depth and texture, twice over the growing season. After each sampling period, we harvested the aboveground biomass in order to measure species biomass and to assess species richness and community functional structure with plant height, leaf area and leaf dry matter content (LDMC). We investigated the relationship between point intercept measurements and aboveground biomass at three hierarchical levels (species, growth-form and community) to find generalizable calibration equations for estimating community biomass and tested for sensitivity of estimates to community structure. We then compared the community weighted mean (CWM) and variance (CWV) of LDMC, calculated with and without calibration. Differences in species growth strategy and phenology strongly impacted biomass estimates at both the species and the community level. These differences were, however, successfully accounted for by growth-form specific calibrations, which provided accurate estimates without any influence of community structure. Lack of calibration may have dramatic consequences on functional structure assessment by inducing errors in estimates of CWV up to 80 %, depending on growth-form proportions. This work contributes to a better understanding of the possible methodological biases induced during sampling with the PIM, when quantifying species relative abundances for functional structure assessment in complex communities. [ABSTRACT FROM AUTHOR]

Aim Many species exhibit a time-lag between habitat loss and its extinction, resulting in extinction debt. Although extinction debt is considered a widespread phenomenon, differences in methodological approaches can affect its detection. We aim to contribute to this methodological debate by exploring whether extinction debt is either a phenomenon common to all patches or idiosyncratic to the patch and landscape attributes of a given patch. We also aim to determine whether the scale dependency of species richness might help to explain extinction debt. Location Southern Catalonia ( NE Iberian Peninsula). Methods We studied the effects of habitat loss on plant species richness (total, specialists and generalists) in stable (habitat loss < 40% since 1956) and regressive (habitat loss more than 40% since 1956) patches of Mediterranean grasslands at both quadrat and patch scales using general linear models. Results We detected extinction debt at patch scale but only in regressive patches. The magnitude of extinction debt was not constant but was related to the percentage of patch area reduction. Contrastingly, regressive patches presented fewer species than stable patches at quadrat scale. Main conclusion Quadrat scale extinctions in regressive patches lead to rarefaction, but not immediate extinction, of some species at patch scale and created an extinction debt. Species loss at quadrat scale constitutes an early warning indicator of the effects of habitat loss on biodiversity, while delayed extinctions offer an opportunity for conservation initiatives. [ABSTRACT FROM AUTHOR]

. 1. Abandonment of traditional activities in the rural areas is widespread in the developed world, and in the case of grazing, it is known to have negative consequences on the diversity of plant communities. Few studies have examined the impact of grazing abandonment on fauna, which in the case of ants is of considerable interest, given their usefulness as an indicator for monitoring environmental change. 2. Here, we present the results of a study conducted in Mediterranean grasslands of central Spain. Using pitfall traps, ants were sampled from 10 40 m× 20 m plots; five of them located in grazed systems and five in abandoned grazing systems. Descriptors used for the ant assemblage were ant species composition, ant species richness, ant functional groups, and subguilds of granivores. We used a seed bait test to discriminate between granivorous and non-granivorous ant species. 3. Our results show that abandoned grazing systems have more ant species and more heterogeneous ant assemblages. Changes in ant species composition and ant functional groups are more pronounced in habitats where woody encroachment progresses more rapidly (i.e. dry sectors and tree islands). Specialised granivores have reduced importance in the same habitat types. Conversely, facultative granivores increase their presence in abandoned grazing systems. 4. The increased functional and species ant diversity observed with grazing abandonment can be explained by the generation of a more heterogeneous environment at the smaller scales, in spite of being more homogenous at the larger scales, because the latter are less significant for the organisms studied. [ABSTRACT FROM AUTHOR]

Field boundaries are expected to support the maintenance of biodiversity in agroecosystems, since they provide the habitat for a range of plant species. However, plant diversity in field boundaries has decreased substantially in recent decades. This pattern is generally linked with the intensification of agricultural land use at field and landscape level. Therefore, we aimed to test the effect of farming management (field and boundary management), boundary structure (width and habitat assemblage considering the Mediterranean grassland element), and landscape heterogeneity on plant species richness of field boundaries. Plants were recorded along 30 field boundaries next to organic fields and 30 next to conventional fields located in 15 agrarian localities of NE Iberian Peninsula along a gradient of landscape complexity. A total of 517 plant species were identified in the 60 field boundaries. We recorded 162 species (31%) catalogued as rare, very rare or extremely rare in the flora of the Catalan Countries. Our results showed the importance of landscape heterogeneity, field management and habitat assemblage, since they were found to be the most influential variables for plant species richness; whereas boundary width and boundary management were seen to contribute less to explaining plant diversity. Accordingly, agri-environmental schemes should be designed to promote organic farming and maintain the structure of the landscape mosaic in order to benefit plant diversity in field boundaries in the Mediterranean region. [ABSTRACT FROM AUTHOR]

Abstract: Climate change scenarios predict increases in temperature, changes in precipitation patterns, and longer drought periods in most semi-arid regions of the world. Ecosystems in these regions are prone to land degradation, which may be aggravated by climate change. Soil respiration is one of the main processes responsible for organic carbon losses from arid and semi-arid ecosystems. We measured soil respiration over one year in two steppe ecosystems having different degrees of land degradation under three ground-covers: with vegetation, bare soil, and an intermediate situation between plants and bare soil. The largest differences in soil respiration rates between the sites were observed in spring, coinciding with the highest level of plant activity. The degraded site had drier and hotter soils with less soil water availability and a longer drought period. As a result, vegetation on the degraded site did not respond to spring rainfall events. Soil respiration showed a strong seasonal variability, with average annual rates of 1.1 and 0.8 μmol CO2 m−2 s−1 in the natural and degraded sites, respectively. We did not observe significant differences in soil respiration rates associated with ground-cover i.e., the temporal variation was much larger than the spatial variation. At both sites, soil moisture was the controlling driver of soil respiration for most of the year, when temperatures were above 20 °C and constrained the response to temperature for the few months when the temperature was below 20 °C. An empirical model based on soil temperature and soil moisture explained 90% and 72% of the seasonal variability of soil respiration on the natural and degraded sites, respectively. For the first time, this study suggests that land degradation may alter the carbon balance of these ecosystems through changes in the temporal dynamics of soil respiration and plant productivity, which have important negative consequences for ecosystem functioning and sustainability. [Copyright &y& Elsevier]

There is limited information on the effects of the increase in the density of shrubs on herbage production and nutritive value of natural grasslands in the Mediterranean region, currently facing major land use changes. Herbage production of drymatter (herbaceous fractions, of plant functional groups and by species), crude protein (CP), neutral-detergent fibre (NDF), acid-detergent fibre (ADF), acid-detergent lignin (ADL) and hemicellulose concentrations and in vitro organic matter digestibility were determined at the time of peak of annual growth across four types of grassland vegetation each characterized by different shrub cover regimes. A sharp reduction in herbage production and a reduction in nutritive value were found as a result of the increase in shrub cover. These changes appeared to be closely related to the shift in plant functional groups detected as shrub density increased. Herbage production from grasses and legumes was found to be more sensitive to shrub cover changes than herbage production from forbs, whereas, as grassland types became denser, annual species were gradually replaced by perennials and C4 grasses by C3 ones. The impact of shrub encroachment on Mediterranean grasslands is discussed in relation to their use by livestock. [ABSTRACT FROM AUTHOR]

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Ozone (O3) phytototoxicity has been reported on a wide range of crops and wild Central European plant species, however no information has been provided regarding the sensitivity of plant species from dehesa Mediterranean therophytic grasslands in spite of their great plant species richness and the high O3 levels that are recorded in this area. A study was carried out in open-top chambers (OTCs) to assess the effects of O3 and competition on the reproductive ability of three clover species: Trifolium cherleri, Trifolium subterraneum and Trifolium striatum. A phytometer approach was followed, therefore plants of these species were grown in mesoscosms composed of monocultures of four plants of each species, of three plants of each species competing against a Briza maxima individual or of a single plant of each clover species competing with three B. maxima plants. Three O3 treatments were adopted: charcoal filtered air (CFA), non-filtered air (NFA) and non-filtered air supplemented with 40 nl l−1 of O3 (NFA+). The different mesocosms were exposed to the different O3 treatments for 45 days and then they remained in the open. Ozone exposure caused reductions in the flower biomass of the three clover species assessed. In the case of T. cherleri and T. subterraneum this effect was found following their exposure to the different O3 treatments during their vegetative period. An attenuation of these effects was found when the plants remained in the open. Ozone-induced detrimental effects on the seed output of T. striatum were also observed. The flower biomass of the clover plants grown in monocultures was greater than when competing with one or three B. maxima individuals. An increased flower biomass was found in the CFA monoculture mesocosms of T. cherleri when compared with the remaining mesocosms, once the plants were exposed in the open for 60 days. The implications of these effects on the performance of dehesa acid grasslands and for the definition of O3 critical levels is discussed. [Copyright &y& Elsevier]

Abstract Endozoochory has proven to be a highly effective mechanism in the dispersal of viable seeds in Mediterranean grasslands. We studied the effect of cattle dung application on species richness, particularly on the reintroduction of species lost after abandonment. Sown and control plots were monitored for 3 years after dung sowing. We found a significant increase in small-scale richness, which may be attributed to the treatment, with the inclusion of species detected in the dung and in the grazed pasture. The differences in richness and floristic composition diminished over time. This experiment proves the potential utility of this treatment for the restoration of species richness in abandoned pastures, although supplementary steps are necessary, including further sowing and/or shrub cutting in subsequent years. [ABSTRACT FROM AUTHOR]

SummaryAnnual carbon budgets of ecosystems are central to our understanding of the biotic control of atmospheric composition, but they are not available under elevated CO2 for most vegetation types. Using gas exchange techniques, we assessed carbon fluxes of four early successional Mediterranean model communities, consisting of grasses, legumes and composites. The assemblages were grown on the same monoliths for three consecutive years in greenhouses tracking field conditions except for CO2 maintained at ambient (370 μmol mol-1) or elevated (700 μmol mol-1) concentration. During the third year of study, CO2 enrichment consistently shifted the annual carbon balance towards lower efflux, with displacements between 4.3 and 26.2 mol m-2 y-1 (one assemblage became a net CO2 sink, another just reached equilibrium, and the remaining two remained as a CO2 source). At least 50% of the shift under elevated CO2 originated from a decrease in belowground respiration. This indicates that, during this year, CO2 enrichment did not predominantly enhance C-cycling, but on the contrary inhibited root respiration or microbial C-utilization. Although elevated-CO2-grown systems acted as a net CO2 sink during a longer period of the year (4–7 months) compared with ambient-CO2-grown systems (3–3.5 months), gross canopy photosynthesis was modified only to a limited extent (between -5.9 and + 14.8%). Interaction between the carbon and the water cycle was apparently responsible for this weak stimulation. In particular, reduced evapotranspiration under elevated CO2 coincided with inhibited canopy photosynthesis in early spring, most likely resulting from water saturation of the soil. In addition, only the earliest-planted assemblages had an increased gross canopy photosynthesis during late autumn... [ABSTRACT FROM AUTHOR]

Endozoochrous seed dispersal by herbivorous mammals has been verified repeatedly and its possible influence on the structure and function of herbaceous communities has been suggested. Quantitative studies, however, are lacking in the field of seed dispersal via the dung of herbivore guilds in little-altered environments. The present paper analyses seed dispersal via rabbit, fallow deer, red deer and cow dung in a Mediterranean dehesa (open woodland used for hunting and ranching) during the seeding season. Dung seed content was determined by the glasshouse cultivation of eight dung samples from each herbivore, collected fortnightly between February and August. The four herbivores disperse many seeds (spring averages are 6-15 seeds per gram of dry dung and maxima of 25-70) from a large number of species (totals between 52 and 78). Dispersal seems to be mainly determined by seed production of the plant comminity. This is reflected in (i) the dissemination of a high percentage of the species present in the dehesa, (ii) great seasonal variability, related to seed production, in the amount of seeds and number of species dispersed, and (iii) a high semi-quantitative similarity of seed content in the four types of herbivore dung throughout the year. There is also important quantitative variation that depends on animal traits and feeding habits. These results and the characteristics of species found in dung suggest the adaptation of plant species to the dispersal of their seeds via herbivore gut. This process may well have profound implications for vegetation dynamics and the evolution of plant traits. [ABSTRACT FROM AUTHOR]