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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]

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]

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]