Biocrust‐forming mosses mitigate the impact of aridity on soil microbial communities in drylands: observational evidence from three continents

Abstract

Recent research indicates that increased aridity linked to climate change will reduce the diversity of soil microbial communities and shift their community composition in drylands, Earth's largest biome. However, we lack both a theoretical framework and solid empirical evidence of how important biotic components from drylands, such as biocrust-forming mosses, will regulate the responses of microbial communities to expected increases in aridity with climate change. Here we report results from a cross-continental (North America, Europe and Australia) survey of 39 locations from arid to humid ecosystems, where we evaluated how biocrust-forming mosses regulate the relationship between aridity and the community composition and diversity of soil bacteria and fungi in dryland ecosystems. Increasing aridity was negatively related to the richness of fungi, and either positively or negatively related to the relative abundance of selected microbial phyla, when biocrust-forming mosses were absent. Conversely, we found an overall lack of relationship between aridity and the relative abundance and richness of microbial communities under biocrust-forming mosses. Our results suggest that biocrust-forming mosses mitigate the impact of aridity on the community composition of globally distributed microbial taxa, and the diversity of fungi. They emphasize the importance of maintaining biocrusts as a sanctuary for soil microbes in drylands.

Effects of nitrogen deposition on the spatial pattern of biocrusts and soil microbial activity in a semi‐arid Mediterranean shrubland

“…Moreover, the addition of 50 kg N ha −1 year −1 frequently resulted in the loss of the characteristic spatial pattern of several biocrust components and soil microbial enzymatic activity. Finally, N addition altered the relationship between biocrust and shrub cover and microbial enzymatic activity, suggesting that changes in cryptogamic and vascular plant vegetation cover can have relevant cascading consequences for the functioning of Mediterranean ecosystems under increasing N deposition scenarios (Delgado‐Baquerizo et al, , ).…”

“…Therefore, biocrusts should be considered as a modulating element in semi‐arid ecosystems that may buffer against the possible pervasive effects of global change drivers such increasing aridity (e.g. Delgado‐Baquerizo et al, , ) and N deposition rates (this study).…”

“…For example, in a study under controlled conditions, the interaction between species richness, evenness and the spatial pattern of biocrust communities was a main driver of the functioning of microbial communities (Castillo‐Monroy, Bowker, García‐Palacios, & Maestre, ). In addition to the key role of mosses and lichens, communities of bacteria and fungi associated with biocrusts also play an important role in the functioning of dryland ecosystems (Delgado‐Baquerizo et al, , ), including those from the Mediterranean Basin (Steven, Gallegos‐Graves, Belnap, & Kuske, ). However, few studies have examined how the composition and spatial pattern of the biocrust communities affect the activity of the soil microbial communities associated with them under real‐world, field conditions (Castillo‐Monroy et al, ), and even less the role that an increase in N deposition and availability may play in this relationship.…”

Biocrust science and global change

“…For example, in this Virtual Issue, Delgado‐Baquerizo et al . (), used a cross‐continental (North America, Europe, and Australia) survey to evaluate how biocrust mosses regulate the relationship between aridity and the community composition and diversity of soil bacteria and fungi. These results suggest that increasing aridity is a strong control over microbial composition in the absence of moss; however, when moss is present, the relationship between aridity and the microbial communities was nonexistent.…”

Synthetic soil crusts against green-desert transitions: a spatial model

“…More recently, ecosystem Terraformation has been suggested as a novel approach against green-desert shifts [24, 42, 43]. In a nutshell, some existing microorganisms, such as cyanobacteria from the soil crust, could be minimally modified by means of synthetic biology techniques to help improving soil moisture and create a cooperative feedback between vegetation or moss cover (see [13]) and the soil microbiome [27]. This engineering scenario aims at building synthetic soil e.g., soil crust, where the un-derlying community structure incorporates the synthetic strain.…”