Search

Earth harbours an extraordinary plant phenotypic diversity1 that is at risk from ongoing global changes2,3. However, it remains unknown how increasing aridity and livestock grazing pressure—two major drivers of global change4–6—shape the trait covariation that underlies plant phenotypic diversity1,7. Here we assessed how covariation among 20 chemical and morphological traits responds to aridity and grazing pressure within global drylands. Our analysis involved 133,769 trait measurements spanning 1,347 observations of 301 perennial plant species surveyed across 326 plots from 6 continents. Crossing an aridity threshold of approximately 0.7 (close to the transition between semi-arid and arid zones) led to an unexpected 88% increase in trait diversity. This threshold appeared in the presence of grazers, and moved toward lower aridity levels with increasing grazing pressure. Moreover, 57% of observed trait diversity occurred only in the most arid and grazed drylands, highlighting the phenotypic uniqueness of these extreme environments. Our work indicates that drylands act as a global reservoir of plant phenotypic diversity and challenge the pervasive view that harsh environmental conditions reduce plant trait diversity8–10. They also highlight that many alternative strategies may enable plants to cope with increases in environmental stress induced by climate change and land-use intensification.Analysis of 20 chemical and morphological plant traits at diverse sites across 6 continents shows that the transition from semi-arid to arid zones is associated with an unexpected 88% increase in trait diversity. [ABSTRACT FROM AUTHOR]

The emergence of alternative stable states in forest systems has significant implications for the functioning and structure of the terrestrial biosphere, yet empirical evidence remains scarce. Here, we combine global forest biodiversity observations and simulations to test for alternative stable states in the presence of evergreen and deciduous forest types. We reveal a bimodal distribution of forest leaf types across temperate regions of the Northern Hemisphere that cannot be explained by the environment alone, suggesting signatures of alternative forest states. Moreover, we empirically demonstrate the existence of positive feedbacks in tree growth, recruitment and mortality, with trees having 4–43% higher growth rates, 14–17% higher survival rates and 4–7 times higher recruitment rates when they are surrounded by trees of their own leaf type. Simulations show that the observed positive feedbacks are necessary and sufficient to generate alternative forest states, which also lead to dependency on history (hysteresis) during ecosystem transition from evergreen to deciduous forests and vice versa. We identify hotspots of bistable forest types in evergreen-deciduous ecotones, which are likely driven by soil-related positive feedbacks. These findings are integral to predicting the distribution of forest biomes, and aid to our understanding of biodiversity, carbon turnover, and terrestrial climate feedbacks. Alternative stable states in forests have implications for the biosphere. Here, the authors combine forest biodiversity observations and simulations revealing that leaf types across temperate regions of the NH follow a bimodal distribution suggesting signatures of alternative forest states. [ABSTRACT FROM AUTHOR]

Context: Mediterranean landscapes are undergoing severe transformations (land-use change and homogenization) that threatens biodiversity and the services these ecosystems provide. These effects can differ amongst biodiversity facets (plants vs. birds, taxonomic vs. functional) and ecosystem functions (e.g., seed dispersal, forest regeneration, pest control), although these are still poorly understood in Mediterranean landscapes. Objectives: Our study aims at understanding how Mediterranean landscape characteristics and land use (tree croplands, shrublands and pine, oak and mixed forest) affect the diversity of birds and plants, and how these changes in biodiversity could affect ecosystem functioning. Methods: In 2020–2021, we sampled 49 (5 × 5 m) plots in South-eastern Spain and from five different land uses: tree croplands, shrublands, and pine, oak and mixed forests. We measured land use, habitat diversity and size, together with birds and plant diversity. We assessed both direct and indirect (via bird and plant diversity) effects of landscape characteristics on 6 different ecosystem functions related to forest regeneration, predation, herbivory or aboveground biomass, which imply interactions between birds, plants and their environment. Results: Plant communities responded mainly to local features (land use), whereas birds did so to habitat size and landscape diversity (within 500 m radius). Seed and caterpillar predation were more affected by bird's diversity, whereas regeneration capacity of woody species was driven by both plants and birds. Land use was amongst the most important drivers of all measured functions, with generally higher functioning levels in oak and mixed forests than in the rest of land uses. Conclusions: Our results emphasize the complementary information obtained when considering multiple biodiversity facets in studying the consequences of landscape transformation. We also show that these multiple biodiversity changes can be as important as those of land-use or landscape characteristics for ecosystem functioning. [ABSTRACT FROM AUTHOR]

Soil contamination is one of the main threats to ecosystem health and sustainability. Yet little is known about the extent to which soil contaminants differ between urban greenspaces and natural ecosystems. Here we show that urban greenspaces and adjacent natural areas (i.e., natural/semi-natural ecosystems) shared similar levels of multiple soil contaminants (metal(loid)s, pesticides, microplastics, and antibiotic resistance genes) across the globe. We reveal that human influence explained many forms of soil contamination worldwide. Socio-economic factors were integral to explaining the occurrence of soil contaminants worldwide. We further show that increased levels of multiple soil contaminants were linked with changes in microbial traits including genes associated with environmental stress resistance, nutrient cycling, and pathogenesis. Taken together, our work demonstrates that human-driven soil contamination in nearby natural areas mirrors that in urban greenspaces globally, and highlights that soil contaminants have the potential to cause dire consequences for ecosystem sustainability and human wellbeing. Liu et al. demonstrate that human-driven soil contamination in natural areas mirrors that in nearby urban greenspaces globally, and highlight the potential influence that soil contaminants have on ecosystem functions. [ABSTRACT FROM AUTHOR]

Background and aims: Biocrusts are major contributors to dryland nutrient cycling by regulating C, N and P inputs and fluxes. However, our understanding about how the decomposition of biocrust constituents contributes to soil nutrient cycling in drylands is virtually unknown. Methods: We conducted a microcosm experiment to: i) evaluate the litter decomposition dynamics of two common biocrust-forming species with contrasting tissue chemistry and growth form (the lichen Cladonia foliacea and the moss Syntrichia caninervis), and ii) their effects on several soil variables related to soil functioning. Results: Cladonia litter decomposed gradually with time (92% total mass loss after 342 days), while Syntrichia litter decomposed much faster (92% total mass loss after 62 days, with no further losses until the end of the experiment at 342 days). We observed species-specific effects of their litter on dissolved organic N (DON) and NH4+ depending on collection time, which changed the effects of litter decomposition on DON and pH regardless of the biocrust species considered. Overall, biocrust litter had a positive effect on SOC, DON, NH 4 + and acid phosphatase activity. Conclusions: Our experimental results show that decomposition of biocrust tissues plays an important role in soil nutrient cycling, indicating that this process impacts the fertility and functioning of dryland soils. [ABSTRACT FROM AUTHOR]

Soils are the foundation of all terrestrial ecosystems1. However, unlike for plants and animals, a global assessment of hotspots for soil nature conservation is still lacking2. This hampers our ability to establish nature conservation priorities for the multiple dimensions that support the soil system: from soil biodiversity to ecosystem services. Here, to identify global hotspots for soil nature conservation, we performed a global field survey that includes observations of biodiversity (archaea, bacteria, fungi, protists and invertebrates) and functions (critical for six ecosystem services) in 615 composite samples of topsoil from a standardized survey in all continents. We found that each of the different ecological dimensions of soils—that is, species richness (alpha diversity, measured as amplicon sequence variants), community dissimilarity and ecosystem services—peaked in contrasting regions of the planet, and were associated with different environmental factors. Temperate ecosystems showed the highest species richness, whereas community dissimilarity peaked in the tropics, and colder high-latitudinal ecosystems were identified as hotspots of ecosystem services. These findings highlight the complexities that are involved in simultaneously protecting multiple ecological dimensions of soil. We further show that most of these hotspots are not adequately covered by protected areas (more than 70%), and are vulnerable in the context of several scenarios of global change. Our global estimation of priorities for soil nature conservation highlights the importance of accounting for the multidimensionality of soil biodiversity and ecosystem services to conserve soils for future generations.A global field survey that analyses samples of soil from all continents identifies hotspots for soil nature conservation, and shows that different ecological dimensions of soil are associated with different priority areas for conservation. [ABSTRACT FROM AUTHOR]

Drylands cover ~41% of the terrestrial surface. In these water-limited ecosystems, soil moisture contributes to multiple hydrological processes and is a crucial determinant of the activity and performance of above- and belowground organisms and of the ecosystem processes that rely on them. Thus, an accurate characterisation of the temporal dynamics of soil moisture is critical to improve our understanding of how dryland ecosystems function and are responding to ongoing climate change. Furthermore, it may help improve climatic forecasts and drought monitoring. Here we present the MOISCRUST dataset, a long-term (2006–2020) soil moisture dataset at a sub-daily resolution from five different microsites (vascular plants and biocrusts) in a Mediterranean semiarid dryland located in Central Spain. MOISCRUST is a unique dataset for improving our understanding on how both vascular plants and biocrusts determine soil water dynamics in drylands, and thus to better assess their hydrological impacts and responses to ongoing climate change. Measurement(s) soil moisture Technology Type(s) soil moisture sensors Factor Type(s) temporal interval Sample Characteristic - Environment semi-arid grassland Sample Characteristic - Location Central Spain Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.16951723 [ABSTRACT FROM AUTHOR]

Despite the high relevance of communities dominated by lichens, mosses and cyanobacteria living on the soil surface (biocrusts) for ecosystem functioning in drylands, no study to date has investigated the decomposition of biocrust-forming lichen litter in situ. Thus, we do not know whether the drivers of its decomposition are similar to those for plant litter (for example, importance of abiotic degradation through UV radiation), the magnitude of lichen decomposition rates and whether they will be affected by ongoing climate change. Here we report the results from a litter decomposition experiment carried out with two biocrust-forming lichens (Diploschistes diacapsis and Cladonia convoluta) that differ in litter chemical quality (C:N ratio) in central Spain. We evaluated how lichen decomposition was affected by warming, rainfall exclusion and their combination. We also manipulated the incidence of UV radiation using mesh material that blocked 10% or 90% of incoming UV radiation. Our results indicate that lichens decompose as fast as some plants typical of the study area (k ~ 0.3 y−1). We observed differences among the species studied in line with what is expected according to their chemical composition. Warming increased decomposition rates of both lichen species by 28% and mediated the effects of photodegradation. Although UV exposure accelerated the decomposition of D. diacapsis, it slowed that of C. convoluta. Our results indicate that biocrust-forming lichens can decompose in the field at a rate similar to that of vascular plants and that this process will be affected by warming. The findings presented emphasize the need of considering biocrusts and the decomposition of their tissues when honing ecosystem models aiming to forecast carbon cycling responses to climate change in drylands. [ABSTRACT FROM AUTHOR]

Understanding how organisms control soil water dynamics is a major research goal in dryland ecology. Although previous studies have mostly focused on the role of vascular plants on the hydrological cycle of drylands, recent studies highlight the importance of biological soil crusts formed by lichens, mosses, and cyanobacteria (biocrusts) as a major player in this cycle. We used data from a 6.5-year study to evaluate how multiple abiotic (rainfall characteristics, temperature, and initial soil moisture) and biotic (vascular plants and biocrusts) factors interact to determine wetting and drying processes in a semi-arid grassland from Central Spain. We found that the shrub Retama sphaerocarpa and biocrusts with medium cover (25-75%) enhanced water gain and slowed drying compared with bare ground areas (BSCl). Well-developed biocrusts (>75% cover) gained more water, but lost it faster than BSCl microsites. The grass Stipa tenacissima reduced water gain due to rainfall interception, but increased soil moisture retention compared to BSCl microsites. Biotic modulation of water dynamics was the result of different mechanisms acting in tandem and often in opposite directions. For instance, biocrusts promoted an exponential behavior during the first stage of the drying curve, but reduced the importance of soil characteristics that accentuate drying rates. Biocrust-dominated microsites gained a similar amount of water than vascular plants, although they lost it faster than vascular plants during dry periods. Our results emphasize the importance of biocrusts for water dynamics in drylands, and illustrate the potential mechanisms behind their effects. They will help to further advance theoretical and modeling efforts on the hydrology of drylands and their response to ongoing climate change. [ABSTRACT FROM AUTHOR]

The importance of biological soil crusts (biocrusts) for the biogeochemistry of drylands is widely recognized. However, there are significant gaps in our knowledge about how climate change will affect these organisms and the processes depending on them. We conducted a manipulative full factorial experiment in two representative dryland ecosystems from central (Aranjuez) and southeastern (Sorbas) Spain to evaluate how precipitation, temperature and biocrust cover affected the assimilation and net C balance of biocrusts. Chlorophyll fluorescence, net photosynthesis and dark respiration were measured in situ bimonthly during a year. We also conducted daily cycle measurements of net photosynthesis in winter and at the end of spring. In Sorbas, warming reduced the fixation of atmospheric C in biocrust-dominated microsites throughout the year. In Aranjuez, there was an interaction between the three factors evaluated; during winter, net photosynthesis was significantly greater in high biocrust cover plots under natural conditions and in the rainfall exclusion treatment. During the daily surveys, rainfall exclusion and warming reduced C fixation in Sorbas and in Aranjuez respectively. The effects of the treatments evaluated varied with the rainfall and non-rainfall water inputs (NRWIs) registered before the measurements. Our results suggest that changes in NRWI regimes as consequence of warming could have a greater impact on the C balance of biocrusts than changes in rainfall amounts. They also indicate that climate change may reduce the photosynthetic ability of lichens, with a consequent reduction of their dominance in biocrust communities at the mid to long term. This could reduce the ability of dryland ecosystems to fix atmospheric C. [ABSTRACT FROM AUTHOR]

The biogeochemical cycles of carbon (C), nitrogen (N) and phosphorus (P) are interlinked by primary production, respiration and decomposition in terrestrial ecosystems. It has been suggested that the C, N and P cycles could become uncoupled under rapid climate change because of the different degrees of control exerted on the supply of these elements by biological and geochemical processes. Climatic controls on biogeochemical cycles are particularly relevant in arid, semi-arid and dry sub-humid ecosystems (drylands) because their biological activity is mainly driven by water availability. The increase in aridity predicted for the twenty-first century in many drylands worldwide may therefore threaten the balance between these cycles, differentially affecting the availability of essential nutrients. Here we evaluate how aridity affects the balance between C, N and P in soils collected from 224 dryland sites from all continents except Antarctica. We find a negative effect of aridity on the concentration of soil organic C and total N, but a positive effect on the concentration of inorganic P. Aridity is negatively related to plant cover, which may favour the dominance of physical processes such as rock weathering, a major source of P to ecosystems, over biological processes that provide more C and N, such as litter decomposition. Our findings suggest that any predicted increase in aridity with climate change will probably reduce the concentrations of N and C in global drylands, but increase that of P. These changes would uncouple the C, N and P cycles in drylands and could negatively affect the provision of key services provided by these ecosystems. [ABSTRACT FROM AUTHOR]

Aims: Plant-soil interactions regulate the response of terrestrial ecosystem to climate change. Recent work suggests that aridity thresholds control soil biodiversity and function worldwide, which abruptly decreased once crossing specific levels of aridity. However, whether and how different vegetation types regulate these aridity thresholds remains largely unknown.Here, we used a global dataset published in the literature to investigate how 24 biodiversity and functional ecosystem attributes respond to aridity in different biomes using a global field survey across grasslands, shrublands, and forests. The biodiversity metrics included the richness of soil organisms at multiple trophic levels from bacteria and fungi to protist and invertebrates, the functional metrics linked to a diverse range of ecosystem services from plant productivity and organic matter decomposition to nutrient cycling and plant–microbe interactions.Pervasive nonlinear relationship between aridity and soil biodiversity and functions were observed in all vegetation types, with vegetation fine-tuning aridity thresholds in soil biodiversity and functions worldwide. Specifically, soil biodiversity and functions in forest ecosystems higher aridity index thresholds compared to those in grassland and shrubland, and they are more likely to collapse in response to increasing aridity.Ecosystem functionality in forest may collapse under less arid conditions in response to aridification compared to grassland and shrubland. Our findings highlight the ecosystem-specific vulnerability of soil system to aridification, and suggest that future studies incorporating biome variance into risk estimation will advance our understanding of how climate change may affect the functioning of terrestrial ecosystem in large areas of our planet.Methods: Plant-soil interactions regulate the response of terrestrial ecosystem to climate change. Recent work suggests that aridity thresholds control soil biodiversity and function worldwide, which abruptly decreased once crossing specific levels of aridity. However, whether and how different vegetation types regulate these aridity thresholds remains largely unknown.Here, we used a global dataset published in the literature to investigate how 24 biodiversity and functional ecosystem attributes respond to aridity in different biomes using a global field survey across grasslands, shrublands, and forests. The biodiversity metrics included the richness of soil organisms at multiple trophic levels from bacteria and fungi to protist and invertebrates, the functional metrics linked to a diverse range of ecosystem services from plant productivity and organic matter decomposition to nutrient cycling and plant–microbe interactions.Pervasive nonlinear relationship between aridity and soil biodiversity and functions were observed in all vegetation types, with vegetation fine-tuning aridity thresholds in soil biodiversity and functions worldwide. Specifically, soil biodiversity and functions in forest ecosystems higher aridity index thresholds compared to those in grassland and shrubland, and they are more likely to collapse in response to increasing aridity.Ecosystem functionality in forest may collapse under less arid conditions in response to aridification compared to grassland and shrubland. Our findings highlight the ecosystem-specific vulnerability of soil system to aridification, and suggest that future studies incorporating biome variance into risk estimation will advance our understanding of how climate change may affect the functioning of terrestrial ecosystem in large areas of our planet.Results: Plant-soil interactions regulate the response of terrestrial ecosystem to climate change. Recent work suggests that aridity thresholds control soil biodiversity and function worldwide, which abruptly decreased once crossing specific levels of aridity. However, whether and how different vegetation types regulate these aridity thresholds remains largely unknown.Here, we used a global dataset published in the literature to investigate how 24 biodiversity and functional ecosystem attributes respond to aridity in different biomes using a global field survey across grasslands, shrublands, and forests. The biodiversity metrics included the richness of soil organisms at multiple trophic levels from bacteria and fungi to protist and invertebrates, the functional metrics linked to a diverse range of ecosystem services from plant productivity and organic matter decomposition to nutrient cycling and plant–microbe interactions.Pervasive nonlinear relationship between aridity and soil biodiversity and functions were observed in all vegetation types, with vegetation fine-tuning aridity thresholds in soil biodiversity and functions worldwide. Specifically, soil biodiversity and functions in forest ecosystems higher aridity index thresholds compared to those in grassland and shrubland, and they are more likely to collapse in response to increasing aridity.Ecosystem functionality in forest may collapse under less arid conditions in response to aridification compared to grassland and shrubland. Our findings highlight the ecosystem-specific vulnerability of soil system to aridification, and suggest that future studies incorporating biome variance into risk estimation will advance our understanding of how climate change may affect the functioning of terrestrial ecosystem in large areas of our planet.Conclusion: Plant-soil interactions regulate the response of terrestrial ecosystem to climate change. Recent work suggests that aridity thresholds control soil biodiversity and function worldwide, which abruptly decreased once crossing specific levels of aridity. However, whether and how different vegetation types regulate these aridity thresholds remains largely unknown.Here, we used a global dataset published in the literature to investigate how 24 biodiversity and functional ecosystem attributes respond to aridity in different biomes using a global field survey across grasslands, shrublands, and forests. The biodiversity metrics included the richness of soil organisms at multiple trophic levels from bacteria and fungi to protist and invertebrates, the functional metrics linked to a diverse range of ecosystem services from plant productivity and organic matter decomposition to nutrient cycling and plant–microbe interactions.Pervasive nonlinear relationship between aridity and soil biodiversity and functions were observed in all vegetation types, with vegetation fine-tuning aridity thresholds in soil biodiversity and functions worldwide. Specifically, soil biodiversity and functions in forest ecosystems higher aridity index thresholds compared to those in grassland and shrubland, and they are more likely to collapse in response to increasing aridity.Ecosystem functionality in forest may collapse under less arid conditions in response to aridification compared to grassland and shrubland. Our findings highlight the ecosystem-specific vulnerability of soil system to aridification, and suggest that future studies incorporating biome variance into risk estimation will advance our understanding of how climate change may affect the functioning of terrestrial ecosystem in large areas of our planet. [ABSTRACT FROM AUTHOR]

Understanding the relationship between biodiversity and ecosystem functioning has been a core ecological research topic over the last decades. Although a key hypothesis is that the diversity of functional traits determines ecosystem functioning, we do not know how much trait diversity is needed to maintain multiple ecosystem functions simultaneously (multifunctionality). Here, we uncovered a scaling relationship between the abundance distribution of two key plant functional traits (specific leaf area, maximum plant height) and multifunctionality in 124 dryland plant communities spread over all continents except Antarctica. For each trait, we found a strong empirical relationship between the skewness and the kurtosis of the trait distributions that cannot be explained by chance. This relationship predicted a strikingly high trait diversity within dryland plant communities, which was associated with a local maximization of multifunctionality. Skewness and kurtosis had a much stronger impact on multifunctionality than other important multifunctionality drivers such as species richness and aridity. The scaling relationship identified here quantifies how much trait diversity is required to maximize multifunctionality locally. Trait distributions can be used to predict the functional consequences of biodiversity loss in terrestrial ecosystems., Competing Interests: Competing interests The authors declare no competing financial interests.

The response of drylands to environmental gradients can be abrupt rather than gradual. These shifts largely occur unannounced and are difficult to reverse once they happen; their prompt detection is of crucial importance. The distribution of vegetation patch sizes may indicate the proximity to these shifts, but the use of this metric is hampered by a lack of large-scale studies relating these distributions to the provision of multiple ecosystem functions (multifunctionality) and comparing them to other ecosystem attributes, such as total plant cover. Here we sampled 115 dryland ecosystems across the globe and related their vegetation attributes (cover and patch size distributions) to multifunctionality. Multifunctionality followed a bimodal distribution across our sites, suggesting alternative states in the functioning of drylands. Although plant cover was the strongest predictor of multifunctionality when linear analyses were used, only patch size distributions reflected the bimodal distribution of multifunctionality observed. Differences in the coupling between nutrient cycles and in the importance of self-organizing biotic processes characterized the two multifunctionality states observed. Our findings support the use of vegetation patterns as indicators of ecosystem functioning in drylands and pave the way for developing effective strategies to monitor desertification processes.