Abstract
Non-rainfall moisture (fog, dew, and water vapor; NRM) is an important driver of plant litter decomposition in grasslands, where it can contribute significantly to terrestrial carbon cycling. However, we still do not know whether microbial decomposers respond differently to NRM and rain, nor whether this response affects litter decomposition rates. To determine how local moisture regimes influence decomposer communities and their function, we examined fungal communities on standing grass litter at an NRM-dominated site and a rain-dominated site 75 km apart in the hyper-arid Namib Desert using a reciprocal transplant design. Dominant taxa at both sites consisted of both extremophilic and cosmopolitan species. Fungal communities differed between the two moisture regimes with environment having a considerably stronger effect on community composition than did stage of decomposition. Community composition was influenced by the availability of air-derived spores at each site and by specialization of fungi to their home environment; specifically, fungi from the cooler, moister NRM Site performed worse (measured as fungal biomass and litter mass loss) when moved to the warmer, drier rain-dominated site while Rain Site fungi performed equally well in both environments. Our results contribute to growing literature demonstrating that as climate change alters the frequency, magnitude and type of moisture events in arid ecosystems, litter decomposition rates may be altered and constrained by the composition of existing decomposer communities.
Highlights
Decomposition of organic matter is a major source of greenhouse gas emissions in terrestrial systems and plays an essential role in ecosystem carbon and nutrient cycling (Kravchenko et al, 2017; Cavicchioli et al, 2019)
As climate change alters temperature and moisture regimes, litter decomposition rates and subsequent CO2 efflux may be controlled by the size and composition of existing decomposer communities as well as how they respond to changing abiotic conditions
Since standing litter can make up the majority of total plant litter in grasslands (Zhou et al, 2009), NRM is an important driver of carbon cycling across these systems
Summary
Decomposition of organic matter is a major source of greenhouse gas emissions in terrestrial systems and plays an essential role in ecosystem carbon and nutrient cycling (Kravchenko et al, 2017; Cavicchioli et al, 2019). As climate change alters temperature and moisture regimes, litter decomposition rates and subsequent CO2 efflux may be controlled by the size and composition of existing decomposer communities as well as how they respond to changing abiotic conditions. Since standing litter can make up the majority of total plant litter in grasslands (Zhou et al, 2009), NRM is an important driver of carbon cycling across these systems. Since the frequency and intensity of rainfall and NRM are changing (Johnstone and Dawson, 2010; Niu et al, 2010; Haensler et al, 2011; Dai, 2013; Akimoto and Kusaka, 2015; Kutty et al, 2019; Hunová et al, 2020), understanding how microbial communities respond to these different moisture sources will help us predict how arid- and semi-arid systems respond to changing climate regimes
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