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The ranges of many species globally have already shifted to maintain climatic equilibrium in the face of climate change.Biocrusts—soil surface dwelling communities of lichens, bryophytes and microbes—play important functional roles in many ecosystems, particularly in drylands. Compared to better studied animal and plant taxa, dryland biocrusts have different establishment requirements and have never been assessed for historical range shifts.Here, we revisited the sites (N = 204) of a 25‐year‐old biocrust survey across a large area (400,000 km2) of drylands in south‐eastern Australia. We used quadratic models to quantify changes in the climate niches of 15 lichen, eight moss and five liverwort taxa, as well as biocrust cover and richness.Our models showed that the observed climatic niches of most taxa have become hotter and drier in the past quarter century, yet the responses of the vast majority of taxa are consistent with remaining in the same geographic space. A similar pattern was observed at the community level, where the peak of biocrust cover and richness now occurs in a hotter, drier environment. Notable exceptions were the liverwort Riccia lamellosa and lichens in the genera Cladonia and Xanthoparmelia, which showed signs of contraction at their arid range edges.Unlike more mobile taxa, most biocrust species have yet to shift geographically and may already be lagging behind the pace of climate change. One explanation for the mortality lag is that long‐term climate variability in the system is extensive, which may have selected for the ability to withstand multi‐year warm periods as long as there is an eventual return to milder conditions. However, no forecasts of future climate include a return to milder conditions, suggesting there will be an eventual loss of ecosystem multifunctionality at the contracting front. Expansion lags are most likely due to delays in the mortality of competing vascular plants.Synthesis: Our study provides a valuable contribution to the knowledge of range shifts in understudied taxa and highlights a future need to promote the expansion of biocrusts to maintain the provision of ecosystem functions and services across their range. [ABSTRACT FROM AUTHOR]

Aim: Lichens and mosses play important functional roles in all terrestrial ecosystems, particularly in tundra and drylands. As with all taxa, to maintain their current niche in a changing climate, lichens and mosses will have to migrate. However, there are no published estimates of future habitat suitability or necessary rates of migration for members of these groups at the global scale. Taxon: Lichens and mosses. Location: Global. Methods: Using global occurrence data, we conducted ensemble distribution models in the 'biomod2' R package, parameterised with a range of climatic, land use and soil variables, to estimate current and future (2100) habitat suitability in 16 abundant species of lichen and moss. Results: Without considering dispersal limitation, suitable area was forecast to expand for eight species and decline for four species. For species with predominantly boreo‐arctic distributions, suitable area typically declined at the temperate range edge and expanded across the High Arctic. Future suitable area available to dryland‐adapted species generally declined overall, likely relating to the desiccation‐tolerant physiology of lichens and mosses. The average migration rates required for species to disperse into new suitable habitat ranged from 1.7 (Placidium squamulosum) to 9.0 km year−1 (Syntrichia ruralis), although most species will need to migrate >16 km year−1 to completely fill their potential future suitable habitat. Main Conclusions: For mosses and lichens, as with all species, migration will be an important part of the adjustment to a warmer climate, but realisation of these potential migrations will require both rare dispersal events and habitat that is suitable in non‐climatic dimensions. Current evidence on dispersal in these groups suggests that these geographical shifts may be unlikely to be realised without intervention, especially in landscapes that are highly modified by humans. [ABSTRACT FROM AUTHOR]

Questions: Biocrusts perform critical functional roles in drylands, where they are regulated predominantly by differences in climate and soils. We asked whether biocrust cover and composition differ among sites of varying vegetation cover and condition. Location: Subhumid drylands in the Namoi Region, eastern Australia. Methods: We assessed the effects of different vegetation strata (trees, shrubs, groundcover) and site vegetation condition (index of quality based on vascular plant richness, and the proportion of perennial and native vascular plants) on the cover, richness and composition of biocrust communities at 43 sites in semi‐arid eastern Australia. Results: Woody plant cover at our sites was negatively related to biocrust cover and richness, but there was only a weak relationship between groundstorey plant cover and biocrusts, suggesting that woody plants are not facilitating biocrusts in this environment. Conversely, greater site condition was strongly associated with richer and more extensive biocrust communities, likely driven by a common response to livestock grazing intensity. There was also a significant multivariate association between biocrust composition and vegetation condition. For example, sites of poorer condition were occupied by generalist taxa, typically short mosses and squamulose lichens, while sites in better condition were characterised by a richer assemblage that included foliose and fruticose lichens, and taller, disturbance‐sensitive mosses. Conclusions: Our study provides empirical evidence of the negative relationship between woody plant cover and biocrusts (amensalism), and the filtering effect of vegetation condition on different biocrust taxa. Predicted drier climates could enhance biocrust dominance by suppressing woody plant growth, while intensified land‐use disturbances are likely to filter biocrust specialists such as fruticose and foliose lichens that are associated with sites in better condition. [ABSTRACT FROM AUTHOR]

Aim: Eucalypts have a widespread global distribution owing to their popularity for agroforestry and as environmental plantings. Despite an abundance of site‐specific evidence that eucalypts modify soils and soil processes, we lack a quantitative synthesis of their overall effects at the global scale. This limits our capacity to assess the likely impacts of future introductions in any given region of the world. Location: Global. Time period: 1986–2021. Major taxa studied: Eucalyptus, Angophora and Corymbia. Methods: We used a systematic search to derive a database of empirical data from 227 studies across 33 countries (neffect size = 2,806) and tested three predictions about the effects of eucalypts on soil properties and whether these effects varied with plantation age and soil depth. Results: Compared with (non‐eucalypt) native vegetation, eucalypts significantly reduced soil moisture, microbial abundance, nitrogen, cations and anions. Relative reductions in soil microbes and ions were stronger in older eucalypt plantations. A comparison of eucalypts with (non‐eucalypt) silvicultural and agropastoral systems revealed similar effects on most soil properties, although eucalypts tended to reduce potassium and enhance carbon to a greater extent than other managed systems. We found no consistent effects of eucalypts on soil pH. Main conclusions: Our study provides the first extensive global meta‐analysis of the effects of eucalypts on soil properties and processes and demonstrates that effects are highly dependent on the community with which they are compared (i.e., natural or managed). In general, our findings reinforce the widely held belief that eucalypts deplete soil nutrients and dominate water resources. Understanding how eucalypts affect soils allows us to assess their global suitability for agroforestry, soil rehabilitation and soil carbon enhancement, while considering the potential environmental costs. [ABSTRACT FROM AUTHOR]

Ecological restoration projects often have variable and unpredictable outcomes, and these can limit the overall impact on biodiversity. Previous syntheses have investigated restoration effectiveness by comparing average restored conditions to average conditions in unrestored or reference systems. Here, we provide the first quantification of the extent to which restoration affects both the mean and variability of biodiversity outcomes, through a global meta‐analysis of 83 terrestrial restoration studies. We found that, relative to unrestored (degraded) sites, restoration actions increased biodiversity by an average of 20%, while decreasing the variability of biodiversity (quantified by the coefficient of variation) by an average of 14%. As restorations aged, mean biodiversity increased and variability decreased relative to unrestored sites. However, restoration sites remained, on average, 13% below the biodiversity of reference (target) ecosystems, and were characterised by higher (20%) variability. The lower mean and higher variability in biodiversity at restored sites relative to reference sites remained consistent over time, suggesting that sources of variation (e.g. prior land use, restoration practices) have an enduring influence on restoration outcomes. Our results point to the need for new research confronting the causes of variability in restoration outcomes, and close variability and biodiversity gaps between restored and reference conditions. [ABSTRACT FROM AUTHOR]

Trait and functional trait approaches have revolutionized ecology improving our understanding of community assembly, species coexistence, and biodiversity loss. Focusing on traits promotes comparability across spatial and organizational scales, but terms must be used consistently. While several papers have offered definitions, it remains unclear how ecologists operationalize "trait" and "functional trait" terms. Here, we evaluate how researchers and the published literatures use these terms and explore differences among subdisciplines and study systems (taxa and biome). By conducting both a survey and a literature review, we test the hypothesis that ecologists' working definition of "trait" is adapted or altered when confronting the realities of collecting, analyzing and presenting data. From 486 survey responses and 712 reviewed papers, we identified inconsistencies in the understanding and use of terminology among researchers, but also limited inclusion of definitions within the published literature. Discrepancies were not explained by subdiscipline, system of study, or respondent characteristics, suggesting there could be an inconsistent understanding even among those working in related topics. Consistencies among survey responses included the use of morphological, phonological, and physiological traits. Previous studies have called for unification of terminology; yet, our study shows that proposed definitions are not consistently used or accepted. Sources of disagreement include trait heritability, defining and interpreting function, and dealing with organisms in which individuals are not clearly recognizable. We discuss and offer guidelines for overcoming these disagreements. The diversity of life on Earth means traits can represent different features that can be measured and reported in different ways, and thus, narrow definitions that work for one system will fail in others. We recommend ecologists embrace the breadth of biodiversity using a simplified definition of "trait" more consistent with its common use. Trait‐based approaches will be most powerful if we accept that traits are at least as diverse as trait ecologists. [ABSTRACT FROM AUTHOR]

Biocrusts are an extensive autotrophic groundcover but are regularly excluded from ecosystem models. One rationale for their exclusion is that their contributions to C and N cycles are negligible in comparison to vascular plants. Here we estimated the magnitude of the biocrust contribution to nutrient cycling in functional terms, comparing tissue chemistry and stoichiometry per ground area with vascular plants per leaf area.We quantified tissue C, N, P and a range of micronutrients in 21 abundant biocrust taxa from an aridity gradient spanning 500 km of Australian drylands.The C, N and P tissue chemistry of biocrust species and vascular plant leaves occupied a similar range, both as ratios and per area. This implies that in functional terms, biocrusts could be considered as a single layer of leaf area spread out across the ground and added to Leaf Area Index (LAI) measurements accordingly.Within biocrust species, the C:N ratio significantly declined with increasing aridity, which was entirely driven by carbon. This finding demonstrates a key functional difference between vascular leaves and biocrusts: C:N ratios in vascular plants are lower in drier environments due to elevated levels of N‐rich photosynthetic machinery relating to a trade‐off in water‐use regulation, while C:N ratios in biocrusts decline with aridity most likely due to carbon shortages relating to their inability to regular water loss (poikilohydry).As global drylands become drier with climate change, our findings suggest that biocrust tissue carbon stocks will decline gradually until the point where carbon budgets become negative and standing biomass is no longer viable. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

To understand how ecological communities will respond to global change we need new tools and datasets on species across large spatial and temporal scales. Hyperspectral reflectance 'spectra' capture a promising set of traits that show potential to be scaled up in time and space via remote sensing. Thus far, spectra have been shown to distinguish the taxa and trait responses of a substantial number of species within a plethora of vascular plant communities, but not yet for biological soil crust communities (biocrusts).Here, we assess if spectra can be applied to identify biocrust species and their trait variation. We collected biocrust specimens across an aridity gradient spanning 650 km within drylands of Eastern Australia and acquired their spectra, over 12,700 spectral readings, with a high‐resolution radiospectrometer. A machine learning method (random forests) was used to assess how well the spectra of biocrust specimens could distinguish their species and broader structural and chemical traits.Spectra were able to differentiate a substantial number of biocrust species (35) with considerable accuracy (~78.5%). Furthermore, spectral features related to chemical traits were found to primarily drive species spectral differences.Synthesis. Our findings establish that biocrust species hold unique and detectable spectral responses, providing an important basis for remote sensing applications on biocrust species and their trait responses across dryland systems. [ABSTRACT FROM AUTHOR]

Biocrusts are multifunctional communities that are increasingly being used to restore degraded or damaged ecosystems. Concurrently, restoration science is shifting away from the use of purely structural metrics, such as relative abundance, to more functional approaches. Although biocrust restoration technology is advancing, there is a lack of readily available information on how to monitor biocrust functioning and set appropriate restoration goals. We therefore compiled a selection of 22 functional indicators that can be used to monitor biocrust functions, such as CO2 exchange as an indicator of productivity or soil aggregate stability as a proxy for erosion resistance. We describe the functional importance of each indicator and the available protocols with which it may be measured. The majority of indicators can be measured as a functional trait of species by using patches of biocrust or cultures that contain only one species. Practitioners wishing to track the multifunctionality of an entire biocrust community would be advised to choose one indicator from each broad functional group (erosion resistance, nutrient accumulation, productivity, energy balance, hydrology), whereas a targeted approach would be more appropriate for projects with a key function of interest. Because predisturbance data are rarely available for biocrust functions, restoration goals can be based on a closely analogous site, literature values, or an expert elicitation process. Finally, we advocate for the establishment of a global trait database for biocrusts, which would reduce the damage resulting from repeated sampling, and provide a wealth of future research opportunities. [ABSTRACT FROM AUTHOR]

Aim: Organisms that disturb the soil while foraging or creating shelter (ecosystem engineers) can have profound effects on ecosystems. Soil ejecta from these disturbances can enhance surface nutrients and the resulting depressions accrue organic matter and develop into biological hotspots. Here, we describe a global meta‐analysis of studies that assessed the impacts of vertebrate soil disturbance on both biotic and abiotic components of ecosystems. Location: Global land surface. Time period: 1941–2016. Major taxa studied: Vertebrates. Methods: After conducting a systematic literature search, we quantitatively synthesized the findings of 149 published studies that compared disturbed and undisturbed surfaces. Our meta‐analysis included 64 engineer species, primarily comprised of rodents and a subset of other mammals. Results: We found that vertebrate soil disturbance significantly enhanced soil nitrogen (by 77%) and phosphorus (35%), and the productivity (32%) and recruitment (32%) of vascular plants. Disturbances had a greater cover of bare soil (126%) than undisturbed controls, and higher abundances of secondary vertebrates (1,233%), that use pre‐constructed burrows as shelter and foraging grounds. Soil disturbance significantly reduced water run‐off (63%) and the abundance of biocrusts (82%). Soil disturbance effects generally intensified with increasing aridity, and the magnitude of soil disturbance effects was not moderated by the area of the disturbance. Disturbances older than 12 months were more distinct from the surrounding matrix than fresh disturbances. The phylogeny of engineers was unrelated to their ecosystem effects, indicating that the same functionality could readily evolve in different taxa. Main conclusions: In general, disturbances become localized patches of elevated functioning, providing strong evidence that vertebrate engineers, especially those in drylands, are an important source of environmental heterogeneity. [ABSTRACT FROM AUTHOR]