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Aim: Wetland loss and degradation threaten biodiversity to an extent greater than most ecosystems. Science‐supported responses require understanding of interacting effects of land use and climate change on wetland biodiversity. Location: Alberta, Canada. Methods: We evaluated how current climate, climate change (as a ghost of the past), land use and wetland water quality relate to aquatic macroinvertebrates and birds. Results: Climatic relationships and climate–land use interactions were observed on chironomid abundance, but not macroinvertebrate taxa richness (MTR) or odonate abundance, which responded to land use and water chemistry. Chironomid abundance was positively associated with cropland and negatively associated with total precipitation. Higher cropland cover and dissolved organic carbon synergistically interacted with total precipitation to affect chironomids. MTR was negatively related to salinity, yet greater area of non‐woody riparian vegetation attenuated salinity effects on MTR. Odonate abundance was negatively related to total phosphorus. Higher grassland cover also increased the negative relationship of total phosphorous to odonate abundance. Climatic relationships and climate–land use interactions were observed on bird species richness (BSR) and abundance of several bird functional groups. Higher BSR and abundances of several bird groups were positively related to average rainfall and greater warming temperatures over time. Area of non‐crop cover and wetlands was positively associated with most bird groups and BSR. Warming temperatures over time ameliorated the negative relationship of higher cropland or less shrubland on aerial insectivores and other bird groups. Main conclusions: Climate patterns and climate change are as important as land use pressures with stronger impacts on birds. Climate change was more influential than current climate and provided novel empirical evidence that progressively warmer, wetter conditions is benefiting some bird groups, including aerial insectivores, a group of conservation concern. Riparian vegetation ameliorated the negative impacts of climate and water quality gradients on MTR and could mitigate global change impacts in agricultural systems. [ABSTRACT FROM AUTHOR]

In the Greater Cape Floristic Region (GCFR) of South Africa, afrotemperate forest islands persist within a broader landscape of Mediterranean-type fynbos shrubland. The co-existence of these contrasting vegetation types in the same climate space suggests interactions between broad-scale climatic parameters and localised variables (notably local disturbance regimes and catchment hydrology). In this study, palaeoecological data from a fynbos-forest boundary were used to assess the effects of interactions between changes in climate, fire and land use on vegetation dynamics and biome resilience at millennial timescales. Fossil pollen, spores and charcoal were extracted from radiocarbon-dated sediment cores to provide proxies for vegetation, hydrology, large herbivore abundance and fire. Constrained hierarchical clustering (CONISS) was applied to the fossil data to identify distinct vegetation assemblages in the palaeoecological record, and to further elucidate ecosystem trajectories through time. Regional palaeoenvironmental data are also referred to in inferring local and regional environmental changes. We expected to find shifts between fynbos and forest alternate stable states associated with changes in fire and rainfall. More specifically, we anticipated fynbos expansion during drier periods and/or those with more fire, and forest expansion during wetter and/or less fire prone periods. However, the fossil pollen data reveal remarkable stability of the fynbos-forest ecotone over the past 3000 years, despite significant changes in climate, fire and land-use. We found resilience of fynbos was enhanced through internal dynamics, namely, a shift from grassy, fire-prone fynbos in warmer, less seasonal time periods with less summer drought stress, to proteoid fynbos with less frequent fire during times of greater summer drought stress. The emergent properties of the respective fynbos types offset physiological advantages to forest species afforded by changes in the fire-free interval and abundant abiotic resource supply, inhibiting invasion of the former biome by the latter. We suggest these mechanisms require further investigation. [ABSTRACT FROM AUTHOR]

Net primary production (NPP) supplies matter, energy, and services to facilitate the sustainable development of human society and ecosystem. The response mechanism of NPP to land use and climate changes is essential for food security and biodiversity conservation but lacks a comprehensive understanding, especially in arid and semi‐arid regions. To this end, taking the middle‐reaches of the Heihe River Basin (MHRB) as an example, we uncovered the NPP responses to land use and climate changes by integrating multisource data (e.g., MOD17A3 NPP, land use, temperature, and precipitation) and multiple methods. The results showed that (a) land use intensity (LUI) increased, and climate warming and wetting promoted NPP. From 2000 to 2014, the LUI, temperature, and precipitation of MHRB increased by 1.46, 0.58°C, and 15.76 mm, respectively, resulting in an increase of 14.62 gC/m2 in annual average NPP. (b) The conversion of low‐yield cropland to forest and grassland increased NPP. Although the widespread conversion of unused land and grassland to cropland boosted both LUI and NPP, it was not conducive to ecosystem sustainability and stability due to huge water consumption and human‐appropriated NPP. Urban sprawl occupied cropland, forest, and grassland and reduced NPP. (c) Increase in temperature and precipitation generally improved NPP. The temperature decreasing <1.2°C also promoted the NPP of hardy vegetation due to the simultaneous precipitation increase. However, warming‐induced water stress compromised the NPP in arid sparse grassland and deserts. Cropland had greater NPP and NPP increase than natural vegetation due to the irrigation, fertilizers, and other artificial inputs it received. The decrease in both temperature and precipitation generally reduced NPP, but the NPP in the well‐protection or less‐disturbance areas still increased slightly. [ABSTRACT FROM AUTHOR]

Climate change, alteration of atmospheric composition, land abandonment in some areas and land use intensification in others, wildfires and biological invasions threaten forests, shrublands and pastures all over the world. However, the impacts of the combinations between global change factors are not well understood despite its pressing importance. Here we posit that reviewing global change factors combination in an exemplary region can highlight the necessary aspects in order to better understand the challenges we face, warning about the consequences, and showing the challenges ahead of us. The forests, shrublands and pastures of the Mediterranean Basin are an ideal scenario for the study of these combinations due to its spatial and temporal heterogeneity, increasing and diverse human population and the historical legacy of land use transformations. The combination of multiple global change factors in the Basin shows different ecological effects. Some interactions alter the effects of a single factor, as drought enhances or decreases the effects of atmospheric components on plant ecophysiology. Several interactions generate new impacts: drought and land use changes, among others, alter water resources and lead to land degradation, vegetation regeneration decline, and expansion of forest diseases. Finally, different factors can occur alone or simultaneously leading to further increases in the risk of fires and biological invasions. The transitional nature of the Basin between temperate and arid climates involves a risk of irreversible ecosystem change towards more arid states. However, combinations between factors lead to unpredictable ecosystem alteration that goes beyond the particular consequences of drought. Complex global change scenarios should be studied in the Mediterranean and other regions of the world, including interregional studies. Here we show the inherent uncertainty of this complexity, which should be included in any management strategy. [ABSTRACT FROM AUTHOR]

Abstract: Worldwide, changing climates and land use practices are escalating woody-plants encroachment into grasslands, reducing biodiversity and altering ecosystem functions. The loss of alpine grasslands is a major conservation concern as they harbor many rare and endemic species. Alpine meadows in Northwest Yunnan, China, represent a global biodiversity hotspot with high species richness, beta diversity, and endemism. Shrubs have expanded greatly in the region and threaten alpine meadow biodiversity. To measure rates of meadow loss due to shrub encroachment and identify its mechanisms, we reconstructed alpine land cover, climate, and land use change from 1950 to 2009 across Northwest Yunnan using satellite data, ground surveys, and interviews. Between 1990 and 2009, at least 39% of the alpine meadows converted to woody shrubs. The patterns of change suggest that a regime shift is occurring. Despite multiple perturbations to the climate and land use systems starting in the 1950s, alpine meadows remained resilient to shrub expansion until the late 1980s. Shrublands rapidly expanded then due to feedback mechanisms involving climate, woody cover, and grazing. Fire may no longer be an effective tool for controlling shrub expansion. This regime shift threatens both endemic meadow biodiversity and local livelihoods. More generally, these trends serve as a warning sign for the greater Himalayan region where similar vegetation changes could greatly affect livelihoods, hydrology, and climate. [Copyright &y& Elsevier]

We investigated the effects of warming and drought on C and N concentrations, nitrogen use efficiency (NUE), and C and N accumulation in different ecosystem compartments. We conducted a 6-year (1999–2005) field experiment to simulate the climate conditions projected by IPCC models for the coming decades in a Mediterranean shrubland. We studied the two dominant species, Globularia alypum and Erica multiflora, and an N-fixing species, Dorycnium pentaphyllum, also abundant in this shrubland. Warming (1 °C) decreased N leaf concentrations by 25% and increased N stem concentrations by 40% in G. alypum. Although warming changed the available ammonium in soil in some seasons, it did not increase total soil N contents. Drought (19% average reduction in soil moisture) decreased leaf N concentrations in the two dominant shrub species, E. multiflora and G. alypum by 16% and 19%, respectively, and increased stem N concentrations by 56% and 40%, respectively. Neither warming nor drought changed the leaf N concentrations in the N-fixing species D. pentaphyllum, although warming increased stem N concentration by 9%. In G. alypum, the increase of stem N concentrations contributed to the observed increase of N accumulation in stem biomass in drought treatments with respect to control plots (8 kg N ha−1). Neither warming nor drought changed NUE in the period 1999–2005. Warming increased soil organic C relative to drought. The effects of warming and drought on C and N concentrations, on N accumulation and on leaf/stem N distribution were not the result of dilution or concentration effects produced by changes in biomass accumulation. Other factors such as the changes in soil N availability, photosynthetic capacity, and plant internal C and N remobilization must be involved. These changes which differed depending on the species and the plant tissue show that the climate change projected for the coming decades will have significant effects on the C and N cycle and stoichiometry, with probable implications for ecosystem structure and function, such as changes in plant–herbivore relationships, decomposition rates or community species composition. [ABSTRACT FROM AUTHOR]

We aimed to test the effect of soil drought conditions projected by general circulation models and eco-physiological models for the next few decades on emission rates of isoprenoids by Mediterranean shrublands. We conducted a field experiment in which we generated soil drought (ca. 12%-20% decreased soil moisture) using automatically sliding curtains, and we measured foliar isoprenoid emissions in the three dominant species of the studied shrubland (Erica multiflora L., Globularia alypum L., and Pinus halepensis L.) in two different annual periods. Monoterpene emissions were detected in the three studied species, but isoprene emissions were significantly detected only in E. multiflora. Main volatile terpenes emitted by the three species were α-pinene, β-myrcene, limonene, and Δ³-carene. In general, maximum isoprenoid emission rates were found in the hottest periods, and minimum emission rates were found in winter. Isoprene emissions in E. multiflora ranged between practically 0 μg g-1 (dry matter) h-1 in winter 2005 and 57 μg g-1 (dry matter) h-1 in summer 2003. Isoprene emissions were 75% lower during the dry second annual period, 2004-2005, than during the first year, 2003-2004. In E. multiflora, there was an overall decrease of 19% in isoprene emissions in response to soil drought. Conversely, monoterpene emissions increased by 26.4% in drought treatment. In G. alypum, there was an overall increase of 75% in terpene emissions in response to soil drought. In P. halepensis, drought treatment increased terpene emission rates by 156%. Drought treatment affected the emissions mainly in the hottest seasons, spring and summer. There were strong compound-specific, species-specific, interannual, and seasonal changes in the emission rates and in their response to the treatments. These data might help to improve prediction algorithms, inventories, and modeling of isoprenoid emissions and of their response to climate change (decreased isoprene emissions and increased monoterpene emissions under moderate or short-term drought and decreased emissions under severe or long-term drought), but the great variability highlights the difficulty of the task. [ABSTRACT FROM AUTHOR]

In this study we propose a model-building approach based on the hierarchical integration of the main environmental factors (climate, topography/lithology, and land uses) determining the distribution of the spur-thighed tortoise in south-east Spain. Data on the presence/absence of the species were primarily based on information derived from interviews to shepherds. The hierarchical modelling exercise consisted of three steps. First, we constructed a model for the entire region using climate variables, thus obtaining a potential climatical model. Second, we introduced variables referring to topography and lithology that fall within the climatic distribution range ( potential model). Third, by using this second model as a starting point, we included land use variables to obtain the actual distribution model. We analysed the changes in the values of probability of the presence of this species for a given cell between the potential and the actual model, assessing areas where habitat quality has decreased, been maintained or increased. The spatial representation of these changes was highly coherent. A discriminant analysis linked areas where habitat quality has dropped with agriculture landscapes, whereas those areas where habitat quality has been maintained or increased were located mainly in shrublands. Twenty-five per cent (479 km2) of the potential distribution of the species became suboptimal when land use was included, which emphasizes the importance of land use changes in both the range dynamics and the conservation of the spur-thighed tortoise in south-east Spain. [ABSTRACT FROM AUTHOR]

Understanding the terrestrial carbon budget, in particular the strength of the terrestrial carbon sink, is important in the context of global climate change. Considerable attention has been given to woody encroachment in the western US and the role it might play as a carbon sink; however, in many parts of the western US the reverse process is also occurring. The conversion of woody shrublands to annual grasslands involves the invasion of non-native cheatgrass ( Bromus tectorum) which in turn leads to increased frequency and extent of fires. We compared carbon storage in adjacent plots of invasive grassland and native shrubland. We scaled-up the impact of this ecosystem shift using regional maps of the current invasion and of the risk of future invasion. The expansion of cheatgrass within the Great Basin has released an estimated 8±3 Tg C to the atmosphere, and will likely release another 50±20 Tg C in the coming decades. This ecosystem conversion has changed portions of the western US from a carbon sink to a source, making previous estimates of a western carbon sink almost certainly spurious. The growing importance of invasive species in driving land cover changes may substantially change future estimates of US terrestrial carbon storage. [ABSTRACT FROM AUTHOR]

In the northern Mediterranean Basin, agricultural land abandonment over the last century has resulted in increasing frequencies of very large, intense fires. In Catalonia (NE Spain) some fires have been locally associated with the expansion of the large, evergreen, resprouting tussock grass Ampelodesmos mauritanica. We tested the hypothesis of a positive feedback between the abundance of A. mauritanica and changing fire regimes. We used permanent plots distributed across a natural gradient of density of A. mauritanica in the Garraf Natural Park near Barcelona. Total aboveground biomass nearly doubled from plots with low to high density through a combination of A. mauritanica replacing the biomass of other components of the community (predominantly native shrubs), and its absolute standing biomass increasing. The quantity of litter also increased. This increase in fuel load and changes in community functional composition resulted from the simultaneous decrease in shrub productivity and an increase in litter accumulation. Litter accumulation was the consequence of A. mauritanica litter decomposing 30% more slowly than that of shrubs. Under standardized conditions, A. mauritanica and its litter were considerably more flammable than any of the shrub species. This resulted in a more than 40-fold increase in calculated plot flammability from low-to-high-density plots. Feedbacks, at the landscape scale, were then analysed using the landscape simulation platform LAMOS. Invasion success and contribution to community biomass of A. mauritanica increased with decreasing fire return intervals. Total area burnt in the landscape during each fire year was positively and exponentially related to the total biomass of A. mauritanica. Simulations showed that landscapes can abruptly switch from regimes of small localized to extensive fires as a result of the spread of A. mauritanica. Therefore, increases in fires under climate change represent threats not only through their direct impacts on ecosystems, but also by promoting invaders such as A. mauritanica, which have the potential to induce powerful feedforward processes and, thereby, fundamental changes to ecosystems. [ABSTRACT FROM AUTHOR]

Predicted changes in climate may affect key soil processes such as respiration and net nitrogen (N) mineralization and thus key ecosystem functions such as carbon (C) storage and nutrient availability. To identify the sensitivity of shrubland soils to predicted climate changes, we have carried out experimental manipulations involving ecosystem warming and prolonged summer drought in ericaceous shrublands across a European climate gradient. We used retractable covers to create artificial nighttime warming and prolonged summer drought to 20-m2 experimental plots. Combining the data from across the environmental gradient with the results from the manipulation experiments provides evidence for strong climate controls on soil respiration, net N mineralization and nitrification, and litter decomposition. Trends of 0%-19% increases of soil respiration in response to warming and decreases of 3%-29% in response to drought were observed. Across the environmental gradient and below soil temperatures of 20°C at a depth of 5-10 cm, a meanQ10 of 4.1 in respiration rates was observed although this varied from 2.4 to 7.0 between sites. HighestQ10 values were observed in Spain and the UK and were therefore not correlated with soil temperature. A trend of increased accumulated surface litter mass loss was observed with experimental warming (2%- 22%) but there was no consistent response to experimental drought. In contrast to soil respiration and decomposition, variability in net N mineralization was best explained by soil moisture rather than temperature. When water was neither limiting or in excess, aQ10 of 1.5 was observed for net N mineralization rates. These data suggest that key soil processes will be differentially affected by predicted changes in rainfall pattern and temperature and the net effect on ecosystem functioning will be difficult to predict without a greater understanding of the controls underlying the sensitivity... [ABSTRACT FROM AUTHOR]

Climate change may affect ecosystem functioning through increased temperatures or changes in precipitation patterns. Temperature and water availability are important drivers for ecosystem processes such as photosynthesis, carbon translocation, and organic matter decomposition. These climate changes may affect the supply of carbon and energy to the soil microbial population and subsequently alter decomposition and mineralization, important ecosystem processes in carbon and nutrient cycling. In this study, carried out within the cross-European research project CLIMOOR, the effect of climate change, resulting from imposed manipulations, on carbon dynamics in shrubland ecosystems was examined. We performed a14C-labeling experiment to probe changes in net carbon uptake and allocation to the roots and soil compartments as affected by a higher temperature during the year and a drought period in the growing season. Differences in climate, soil, and plant characteristics resulted in a gradient in the severity of the drought effects on net carbon uptake by plants with the impact being most severe in Spain, followed by Denmark, with the UK showing few negative effects at significance levels ofp= 0.10. Drought clearly reduced carbon flow from the roots to the soil compartments. The fraction of the14C fixed by the plants and allocated into the soluble carbon fraction in the soil and to soil microbial biomass in Denmark and the UK decreased by more than 60%. The effects of warming were not significant, but, as with the drought treatment, a negative effect on carbon allocation to soil microbial biomass was found. The changes in carbon allocation to soil microbial biomass at the northern sites in this study indicate that soil microbial biomass is a sensitive, early indicator of drought- or temperature-initiated changes in these shrubland ecosystems. The reduced supply of substrate to the soil and the response of the soil microbial biomass may help to... [ABSTRACT FROM AUTHOR]

• Afforestation with Pinus radiata will intensify the decrease in water yield. • Conservative scenarios with native forest could partially mitigate the effect of climate change. • Pine areas under drier climate conditions revealed a larger vulnerability than shrublands. Climate change (CC) along with Land Use and Land Cover Change (LULCC) have a strong influence in water availability in already fragile Mediterranean ecosystems. In this work the Soil and Water Assessment Tool (SWAT) was implemented for the 2006–2018 period in a rainfed catchment of central Chile (36°) to test the hypothesis that adaptive plantation strategies could mitigate the impacts of climate change and increase streamflow. We also hypothesize that afforestation with exotic tree plantations will reduce water availability in Mediterranean catchments, acting in synergy with climate change. Five LULCC scenarios are analyzed: i) current long-term national Forest Policy (FP), ii) extreme scenario (EX) with large afforestation surfaces, both including the replacement of native shrublands with Pinus radiata ; iii) adaptive plantation management scenario (FM), with lower planting density, iv) forced land displacement scenario (FLD), where plantations at the headwaters are moved to lowland areas and replaced with native shrublands, and v) pristine scenario (PR), with only native vegetation. Each LULCC scenario was run with present climate and with projections of different CMIP5 climate models under the RCP 8.5 scenario for the period 2037–2050, and then compared against simulations based on the present land cover and climate. Simulations with the five LULCC scenarios (FP, EX, FM, FLD and PR) with present climate resulted in variations of −2.5, −17.3, 0, 2.3 and 10.9% on mean annual streamflow (Q), while simulations with the current land cover and CC projections produced a 32.1% decrease in mean annual Q. The joint impact of CC and LULCC leads to changes in mean annual Q ranging from −46.2% (EX) to –23.3% (PR). Afforestation with exotic pines will intensify the reduction in water yield, while conservative scenarios focused on native forests protection and restoration could partially mitigate the effect of CC. We make a strong call to rethink current and future land management strategies to cope with lower water availability in a drier future. [ABSTRACT FROM AUTHOR]

Understanding long‐term changes in ecological communities during global change is a priority for 21st‐century ecology. Deserts, already at climatic extremes, are of unique interest because they are projected to be ecosystems most responsive to global change. Within a 500‐km2 landscape in the Mojave Desert, USA, we measured perennial plant communities at 100 sites three times (1979, 2008, and 2016) during 37 yr to evaluate six hypotheses of community change. These hypotheses encompassed shifts in community measures (e.g., diversity, cover) and species elevational distributions, biotic homogenization, disproportionately large change at the highest elevations, relationships between turnover and species' responses to disturbance and drought, and that environmental refugia (e.g., moist topographic positions) would receive species during climatic warming and drying. Most community measures changed temporally, such as species density (species/600 m2) increasing 23% and plant cover doubling between 1979 and 2016. There was no increase in nonnative species and minimal evidence for biotic homogenization. High‐elevation communities did not display greater change than low‐elevation communities. Moreover, environmental refugia factored little in species shifts. While species distributional changes were unrelated to affinity for disturbance, the six most persistent species (persisting on >80% of sites) were long‐lived shrubs not associated with disturbance. Overall, seemingly paradoxically, climatic warming and drying was associated with increasing plant abundance. Comparing the 1970s to 2007–2016, precipitation in the study area declined 16% from 17 to 14 cm/yr and average daily minimum temperature rose 13% (1.2°C). The current climate with fewer freezes, together with reduced grazing, could be among the most optimal for desert perennials in the past century, although potential response lags to continuing warming and drying are uncertain. This study of long‐term elevational shifts in communities during global change is among few in deserts, and the average upward elevational shift of 6 m/decade for species in our study is within the range reported for temperate biomes. However, the 41% of species moving downslope is unusually high. We propose that dynamics within desert perennial communities follow a core‐transient species model where a site's species are either highly persistent or transient in approximately equal proportions. [ABSTRACT FROM AUTHOR]