Direct and indirect effects of shifting rainfall on soil microbial respiration and enzyme activity in a semi-arid system

Abstract

Background and aims Higher interannual precipitation variability is predicted for Southern California's shrubdominated systems, promoting soil moisture variation and changing community composition. We asked if soil microbial responses to rainfall regime will depend on litter inputs; showing direct effects of altered precipitation through soil moisture and indirect effects resulting from shifting litter inputs. Methods Soils were collected from a 2-year field rainfall manipulation experiment. Under lab conditions soils were subjected to high or low moisture pulses with litter amendments from native and exotic species in all combinations. Results Soil respiration was higher with larger water pulses, but rose over time in low pulse treatments (direct response). Litter additions from exotic species promoted greater respiration, and results were stronger under higher soil moisture (indirect response). Extracellular enzyme activities generally were higher with exotic litter and under high moisture pulses. Those involved in N-cycling had much larger increases activity for the exotic litter addition-high moisture pulse scenarios compared to other treatments. Conclusions Our results indicate the potential for microbial acclimation to drought conditions over short timescales and that below-ground processes are sensitive to direct and indirect effects of shifting rainfall regimes, especially where invasion is promoted by future climate change.

Soil microbial activity in a Mediterranean garrigue responds more to changing shrub community than to reduced rainfall

“…More generally, the apparent absence of any direct impact of lower precipitation is in line with previous studies on drought effects in Mediterranean soils, which reported no or only small effects of increased drought on the soil microbial community in forested and shrubland systems (Sardans et al 2008;De Dato et al 2010;Pailler et al 2014), even in the long term (Curiel-Yuste et al 2014). In the studied semi-arid ecosystem, the repetitive and regular summer drought may have already selected for drought-tolerant organisms, as suggested in previous studies (Evans and Wallenstein 2012;Esch et al 2017). Consequently, ecosystems with regular drought occurrence may be less impacted by drier conditions under predicted precipitation change than ecosystems in more humid climates (Hawkes and Keitt 2015).…”

Understory Plants Regulate Soil Respiration through Changes in Soil Enzyme Activity and Microbial C, N, and P Stoichiometry Following Afforestation

“…Consequently, even slight changes in understory plant community composition and traits could affect SR through shifts in productivity [4], changing litter inputs and altering the soil microclimate [5,6]. Many studies have reported that plants can control the balance between plant C inputs and losses [7][8][9][10]. However, the means by which changes in plant community traits affect this ecosystem process, especially in afforested ecosystems, is poorly understood.…”

In situ phytoremediation of copper and cadmium in a co-contaminated soil and its biological and physical effects

“…Soil enzyme activity is a direct indicator of soil microbial activity in response to metabolic requirements and available nutrients; it is especially useful for evaluating the impact of heavy metal pollution in soil. 51 The untreated soil showed very low BG and NAG activities, indicating a poor functional ability to catalyze the decomposition and transformation of soil carbon and nitrogen. The activities of BG, NAG and AP increased signicantly by 205%, 114% and 17.4% in E. splendens soil, respectively, as compared with the control (Fig.…”