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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]

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]

Transplant studies have long been a cornerstone of experimental ecology. Lichens and bryophytes have several useful characteristics for transplantation: they are small, easily transported, and highly responsive to environmental gradients. Here we conduct a systematic review to synthesise lichen and bryophyte transplant studies up until March 2020 (N=454). A great majority of studies (67%) used lichen and bryophyte transplants as biosensors of airborne pollutants. Other research themes such as forest management and biotic interactions were associated with comparably modest bodies of work. A total of 247 lichen and bryophyte species had been used in transplant studies, but four species predominated: Hypogymnia physodes, Pseudevernia furfuracea, Evernia prunastri and Lobaria pulmonaria. Liverworts were only transplanted in 4% of studies, and most studies focused on epiphytic (69%) or terricolous species (31%). A small group of studies (N=15) used whole-community transplants with areas ranging from 25–250,000 cm2. Apart from pollution research, studies centered on assisted colonization and simulated climate change appear to be increasing most rapidly in time. There were several recurrent lines of investigation within the included literature (e.g., edge effects, colonization of young forests, climate change effects and local adaptation) and we synthesise the key results. We recommend that future research address underrepresented taxa (e.g., liverworts, biological soil crusts) and geographic gaps, namely Australia and Africa. [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]

Background and aims: Livestock grazing and climate change are two of the most important global change drivers affecting ecosystem functioning in drylands. Grazing and climate are known to influence the cover and composition of biocrusts, which are substantial components of dryland soils globally. Much less is known, however, about how these global change drivers affect the functional diversity of biocrust communities in these ecosystems.Methods: Here, we evaluate the role of increasing aridity and grazing intensity in driving the functional diversity of biocrusts. We collected data on multiple biocrust functional traits and community composition, recent and historic grazing intensity, and vascular plants at 151 sites from drylands in eastern Australia. We then used structural equation modelling and a fourth corner analysis to examine the combined effects of aridity and grazing on biocrust functional diversity and individual functional traits.Results: Aridity had a significant direct suppressive effect on biocrust functional diversity. Effects of grazing by livestock, kangaroos and rabbits on functional diversity were predominantly indirect and suppressive, mediated by a reduction in biocrust cover. Grazing did, however, promote functional diversity via an increase in vascular plant richness, with a concomitant increase in biocrust richness. The overall effect of grazing on biocrust functional diversity however was negative. Fourth corner analyses revealed that livestock grazing had a significant negative effect on the ability of biocrusts to stabilise the soil. Aridity had strong negative effects on biocrust height and their ability to absorb water and capture sediment. Few significant relationships were detected between enzyme-related traits and environmental variables.Conclusions: Our findings provide novel evidence that the combination of increasing aridity and intensified livestock grazing will reduce the functional diversity and capabilities of biocrust communities, with resultant declines in ecosystem functioning. [ABSTRACT FROM AUTHOR]

• Biocrust species composition differed among the three geomorphic zones. • Biocrust taxa in the runoff zones had a greater capacity to trap water and sediment. • Grazing had no effect on biocrust communities among the three geomorphic zones. • Resource acquisition by biocrusts may maintain patterned dryland environments. Spatial patchiness in resources is a pervasive feature of drylands worldwide. This patchiness manifests itself as two distinct geomorphic zones that are characterised by the loss (runoff) or gain (runon) of resources such as water, seed and organic matter. Most studies have examined how vascular plants vary across these two distinct zones, but there are few studies of the non-vascular components of these patterned landscapes. We examined the distribution of soil crust lichens and bryophytes (moss, liverworts) in relation to three geomorphic positions within a patterned Acacia aneura woodland grazed by sheep and kangaroos. We found that the distribution of biocrust taxa was strongly related to geomorphic position, with lichens dominating the runoff zones and liverworts restricted to the runon areas (groves). The runon zones were characterised by a greater cover of litter, and greater species richness, cover, and functional richness of biocrusts, while biocrusts in the runoff zones had greater functional diversity and dispersion. Importantly, biocrusts growing in the runon areas were taller, had shorter rhizines, and a greater capacity to trap sediment and absorb water. There were no effects of grazing intensity nor herbivore type (sheep cf. kangaroo) on any diversity or functional measures of biocrusts. Overall, our study indicates that the functional attributes of biocrusts align with those reported for vascular plants (e.g., perennial grasses), by affecting hydrological processes and sediment capture, albeit at smaller spatial scales. Biocrusts may be important, therefore, for sequestering small falls of water emanating from resource-shedding zones, thereby reinforcing landscape patchiness, particularly as hotter and drier climates reduce the cover of vascular plants in drylands. [ABSTRACT FROM AUTHOR]