Biocrusts increase the resistance to warming‐induced increases in topsoil P pools

Abstract

1. Ongoing global warming and alterations in rainfall patterns driven by climate change are known to have large impacts on biogeochemical cycles, particularly on drylands. In addition, the global increase in atmospheric nitrogen (N) deposition can destabilize primary productivity in terrestrial ecosystems, and phosphorus (P) may become the most limiting nutrient in many terrestrial ecosystems. However, the impacts of climate change on soil P pools in drylands remain poorly understood. Furthermore, it is unknown whether biocrusts, a major biotic component of drylands worldwide, modulate such impacts.2. Here we used two long-term (8-10 years) experiments conducted in Central (Aranjuez) and SE (Sorbas) Spain to test how a ~2.5°C warming, a ~30% rainfall reduction and biocrust cover affected topsoil (0-1 cm) P pools (non-occluded P, organic P, calcium bound P, occluded P and total P).3. Warming significantly increased most P pools-except occluded P-in Aranjuez, whereas only augmented non-occluded P in Sorbas. The rainfall reduction treatment had no effect on the soil P pools at any experimental site. Biocrusts increased most soil P pools and conferred resistance to simulated warming for major P pools at both sites, and to rainfall reduction for non-occluded and occluded P in Aranjuez. 4. Synthesis. Our findings provide novel insights on the responses of soil P pools to warming and rainfall reduction, and highlight the importance of biocrusts as modulators of these responses in dryland ecosystems. Our results suggest that the observed negative impacts of warming on dryland biocrust communities will decrease their capacity to buffer changes in topsoil P driven by climate change.

A false paradigm? Do biocrust types necessarily reflect ‘successional stages’?

“…Yet, since germination takes place only on a wet/moist ground, it will take place only during a restricted period of time during which surface moistness is sufficiently high. As shown for the Negev, and in contrast to assumptions made by numerous scholars (Baldauf et al, 2020;Brock, 1975;Garcia-Velásquez et al, 2022;Hao et al, 2012;Hoellrich et al, 2023;Jia et al, 2014;Liu et al, 2006;Mager & Thomas, 2011;Qiu & Gao, 1999;Wang et al, 2014;Zhang et al, 2009), non-rainfall water (NRW) may not provide the necessary threshold, which may activate cyanobacteria, and as such, germination is restricted to the rainy season. Even at the dewy Negev Desert (Evenari et al, 1971), the notion that NRW may wet the surface was not substantiated.…”

A research agenda for nonvascular photoautotrophs under climate change

“…Cover reduction, but also a shift in species composition, may lead to increased susceptibility of the soil surface to erosion by wind and water (Eldridge et al ., 2020) and also enforce a feedback between surface albedo and climate (Rutherford et al ., 2017). In addition, substantial alteration of ecosystem nitrogen fixation and carbon sequestration may occur (current contributions by NVP of 25% and 10% on average, respectively; Elbert et al ., 2012; Rousk & Michelsen, 2017), and also phosphorus cycling may be affected (Concostrina‐Zubiri et al ., 2022; García‐Velázquez et al ., 2022). Furthermore, climate change impacts on NVP‐mediated soil nutrient cycling will likely be species‐specific (Concostrina‐Zubiri et al ., 2021).…”