Insolation and disturbance history drive biocrust biodiversity in Western Montana rangelands

Abstract

Background and Aims Biological soil crust (biocrust) communities, though common and important in the intermountain west, have received little research attention. There are gaps in understanding what influences biocrust species' abundance and distributions in this ecoregion. Climatic, edaphic, topographic, and biotic forces, in addition to anthropogenic disturbance can all influence the biocrust. Methods We determined the relative influence of several possible environmental filters in biocrust communities of western Montana (USA) grasslands at two spatial scales. The larger scale exploited strong topographically-dictated climatic variation across >60km 2 , while the smaller scale focused on differences among distinct microsites withiñ 700m 2 plots. Results We detected a total of 96 biocrust taxa, mostly lichens. Biocrust richness at each site ranged from 0 to 39 species, averaging 14 species. Insolation, aspect, and disturbance history were the strongest predictors of biocrust richness, abundance, and species turnover across the landscape; soil texture was influential for some biocrust community properties. Steep, northfacing slopes that receive longer periods of shade harbored higher diversity and cover of biocrust than southfacing sites. At a small scale, interspaces among native herbaceous communities supported the greatest diversity of biocrust species, but microsites under shrub canopies supported the greatest cover. Conclusions We found that, among the variables investigated, tillage, insolation, soil texture and the associated vegetation community were the most important drivers of biocrust abundance and species richness. This study can inform the practice of restoration and conservation, and also guide future work to improve predictions of biocrust properties.

Biocrust landscape‐scale spatial distribution is strongly controlled by terrain attributes: Topographic thresholds for colonization in a semiarid badland system

“…Though this is not a universal model for dryland soil succession and surface component distribution generalizable to all areas, similar patterns have been observed in other regions with different climate conditions and soil properties (Kidron et al, 2010;Fischer et al, 2014;Durham et al, 2018). For example, Kidron et al (2010) found that in undisturbed areas in the Negev, cyanobacteria-dominated biocrusts predominated on the sunniest hillslopes, whereas lichen and mosses were more frequent in shaded areas with longer wet periods.…”

“…Vegetation, in contrast, was found only in interdune areas, which received run-on from upslope biocrusts. Within such frameworks, maintenance of natural landscape features that promote microclimatic heterogeneity, as well as runoff, sediment and nutrient feedback mechanisms, is likely to be an important contribution to successful conservation and restoration plans promoting microhabitat formation where different species and life forms coexist (Durham et al, 2018). We suggest that traditional restoration approaches mainly focusing on the recovery of functional plant communities (Young et al, 2005;Kulmatiski et al, 2006;Munson et al, 2011;Pocock et al, 2012) should be revised, and a different framework, implicitly considering natural succession and the constraints that characterize these regions around the world, as well as how local biotic life copes with these limitations, is critical to return drylands to their historic trajectory (Yu et al, 2008;Merino-Martin et al, 2012).…”

“…Global biocrust and vegetation composition, abundance and distribution are mainly controlled by climatic forces (Bowker et al, 2016). However, ecosystem-scale soil and topography generate deviations from larger-scale climate patterns and have demonstrated an important effect modifying environmental filters for vegetation and biocrust components (Williams et al, 2013;Bowker et al, 2016;Durham et al, 2018). These effects are particularly important in topographically complex areas such as El Cautivo, where by controlling water redistribution, microclimate and soil stability and development, topography explains about 90% of the total variation in soil surface composition (Figure 3).…”

“…We suggest that traditional restoration approaches mainly focusing on the recovery of functional plant communities (Young et al, 2005;Kulmatiski et al, 2006;Munson et al, 2011;Pocock et al, 2012) should be revised, and a different framework, implicitly considering natural succession and the constraints that characterize these regions around the world, as well as how local biotic life copes with these limitations, is critical to return drylands to their historic trajectory (Yu et al, 2008;Merino-Martin et al, 2012). Within such frameworks, maintenance of natural landscape features that promote microclimatic heterogeneity, as well as runoff, sediment and nutrient feedback mechanisms, is likely to be an important contribution to successful conservation and restoration plans promoting microhabitat formation where different species and life forms coexist (Durham et al, 2018).…”

“…where LSF is the length slope factor, A the contribution area, β the slope gradient and n and m are constant parameters fitted to 0.4 and 1.3, respectively (Renard et al, 1997). Finally, the potential incoming solar radiation considering topographical shadows, which is a key parameter controlling the potential evapotranspiration (Monteith and Szeicz, 1962) and has been traditionally used as a proxy of thermal microclimate (Durham et al, 2018;Suggitt et al, 2018), was calculated using the DEM and a geometric solar radiation model implemented in ArcGIS Solar Analyst by assuming a constant transmissivity of 0.5 (Fu and Rich, 2003).…”