Response of the Soil Microbial Community to Changes in Precipitation in a Semiarid Ecosystem

Abstract

dMicrobial communities regulate many belowground carbon cycling processes; thus, the impact of climate change on the structure and function of soil microbial communities could, in turn, impact the release or storage of carbon in soils. Here we used a large-scale precipitation manipulation (؉18%, ؊50%, or ambient) in a piñon-juniper woodland (Pinus edulis-Juniperus monosperma) to investigate how changes in precipitation amounts altered soil microbial communities as well as what role seasonal variation in rainfall and plant composition played in the microbial community response. Seasonal variability in precipitation had a larger role in determining the composition of soil microbial communities in 2008 than the direct effect of the experimental precipitation treatments. Bacterial and fungal communities in the dry, relatively moisture-limited premonsoon season were compositionally distinct from communities in the monsoon season, when soil moisture levels and periodicity varied more widely across treatments. Fungal abundance in the drought plots during the dry premonsoon season was particularly low and was 4.7 times greater upon soil wet-up in the monsoon season, suggesting that soil fungi were water limited in the driest plots, which may result in a decrease in fungal degradation of carbon substrates. Additionally, we found that both bacterial and fungal communities beneath piñon pine and juniper were distinct, suggesting that microbial functions beneath these trees are different. We conclude that predicting the response of microbial communities to climate change is highly dependent on seasonal dynamics, background climatic variability, and the composition of the associated aboveground community.

Temporal variation overshadows the response of leaf litter microbial communities to simulated global change

“…In summary, the responses of leaf litter microbes to the global change manipulations might have been easily overlooked without consideration of background seasonal variability. This pattern is consistent with other recent experiments (Cruz-Martinez et al, 2009;Yuste et al, 2011;Cregger et al, 2012) and suggests that future changes in seasonality may be even more important than changes in annual averages. We predict in this system, for instance, that additional summer rain will have a greater impact on litter decomposition than a slight increase in mean annual precipitation.…”

“…Although previous studies have examined the response of microbial composition to environmental change over multiple years (for example, Sheik et al, 2011;Gutknecht et al, 2012), only a handful have considered the effect of seasonal variation on these responses (for example, Lage et al, 2010;Bell et al, 2014). However, the fast generation times of microbes mean that composition can turnover quickly, even across seasons (Bardgett et al, 1999;Kennedy et al, 2006;Habekost et al, 2008;Cregger et al, 2012;Gutknecht et al, 2012). We hypothesize that this high background variability will have several, important consequences for global change responses.…”

“…Second, the response of microbial communities to environmental change will depend on the time of year. Seasonal variation in the traits of the microbial community could alter its response to environmental change (Bardgett et al, 1999;Niklaus et al, 2003;Cregger et al, 2012). Third, season-dependent responses will be particularly strong when the environmental parameter also varies seasonally.…”

Dispersal-Based Microbial Community Assembly Decreases Biogeochemical Function

“…In natural systems, microbial community compositional differences can be due to competitive dynamics that select for organisms based on their niche optima [48,49] and to immigration of new taxa from the regional species pool [7,32,50]. Strong local selective pressures can lead to more fit species and enhanced biogeochemistry [7].…”

Tallgrass prairie soil fungal communities are resilient to climate change

“…For example, Rygiewicz et al (2000) showed that soil fungal community responses to elevated temperature differed between [CO 2 ] treatments. Heterotrophic fungal communities and their responses to shifts in environmental conditions are particularly important, because they are essential in carbon and nutrient cycling (Dighton 2003), comprise a large recalcitrant belowground carbon sink (Treseder & Allen 2000), and may be affected directly by the shifts in the environmental drivers or indirectly through the responses in plant communities (Cregger et al 2012). Anderson et al (2013) observed that both elevated CO 2 and elevated temperature influenced the fungal community composition.…”