The influence of biological soil crusts on¹⁵N translocation in soil and vascular plant in a temperate desert of northwestern China

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

“…Some of the main growth constraints for dryland plants are shallow and poorly developed soils, scarce precipitation and high potential evapotranspiration rates (Noy-Meir, 1973). Biocrusts reduce water and wind erosion (Belnap et al, 2014;Chamizo et al, 2017), while acting as a sustainable source of runoff water and nutrients to downstream vegetation (Barger et al, 2006;Li et al, 2008;Cantón et al, 2014;Rodríguez-Caballero et al, 2015, 2018bZhuang et al, 2015;Chamizo et al, 2017). Spatial distribution of the landscape components depends on local water-biomass feedback (Bonachela et al, 2015) and on how abiotic factors, such as geological, geomorphological and pedological properties, modify resource availability and microclimate (Greig-Smith, 1979;Yair and Shachak, 1982;Monger and Bestelmeyer, 2006;Peters and Havstad, 2006).…”

“…These cryptogamic communities dominated by poikilohydric organisms, such as algae, cyanobacteria, lichens and mosses, in intimate association with soil particles and heterotrophic micro-organisms, are specifically adapted for coping with drought and are the dominant life form in open soil surfaces in many dryland regions around the world (Rodríguez-Caballero et al, 2018a). Biocrusts reduce water and wind erosion (Belnap et al, 2014;Chamizo et al, 2017), while acting as a sustainable source of runoff water and nutrients to downstream vegetation (Barger et al, 2006;Li et al, 2008;Cantón et al, 2014;Rodríguez-Caballero et al, 2015, 2018bZhuang et al, 2015;Chamizo et al, 2017). Therefore, it is widely accepted that consideration of the cover, composition and spatial distribution of biocrusts is essential to understanding dryland structure and functioning.…”

Soil microbial responses to nitrogen addition in arid ecosystems

“…As rainfall increases, so does the importance of biocrusts in soil stability, the contribution of newly fixed C and N to soils, and the interception of nutrient-rich dust that includes anthropogenically created atmospheric N ( Pointing and Belnap, 2012 ). The fungal networks that integrate biocrusts are able to translocate this N to plants ( Green et al, 2008 ; Zhuang et al, 2014 ).…”

Evidence for a fungal loop in shrublands

“…Evidence for the existence and functional role of fungal loops in dryland systems derives primarily from studies conducted in grasslands in North America and Asia (Aanderud et al., 2018; Dettweiler‐Robinson et al., 2018, 2019; Green et al., 2008; Hawkes, 2003; Lingfei et al, 2005; Lutgen et al, 2003; Rudgers et al., 2018; Zhuang et al., 2015). These studies have documented the biologically mediated (Collins et al., 2014) movement of the stable isotope 15 N from cyanobacterial biocrusts to nearby grasses and forbs (with one study showing the reciprocal movement of 13 C from grasses to biocrusts; Green et al., 2008), and have found that dark septate fungal endophytes in orders such as Pleosporales and Pezizales routinely dominate the microbial communities in both biocrust and plant tissues (Allen, 2007; Apple, 2010; Barrow, 2003; Bates et al., 2012; Maier et al, 2016; Massimo et al., 2015), as well as the rhizosphere soils and soil interspaces in these experiments (Aanderud et al., 2018; de Mesquita et al, 2018; Green et al., 2008; Porras‐Alfaro & Bayman, 2011; She et al., 2018).…”

“…Dark septate endophyte (DSE) taxa in the soil can increase in community dominance and abundance in response to the moving concentration gradient of 15 N through soil interspaces (Dean et al., 2014; She et al., 2018), and their presence in the soil correlates with improved plant and biocrust fitness (reviewed by Newsham, 2011). Considering current literature relating N translocation through dark septate fungal bodies (Collins et al, 2014; de Mesquita et al, 2018; Green et al., 2008; Rudgers et al., 2018; She et al., 2018; Zhuang et al., 2015), the direct role of DSEs in the exchange of nutrients across drylands is likely. In grasslands, the direct or indirect severing of fungal connections has resulted in decreased primary production in vascular plant communities (Dettweiler‐Robinson et al., 2018, 2020), and even changes in plant community composition (reviewed by Zhang et al, 2016), indicating that the presence of fungal networks directly impacted these two phenomena.…”