OOS 23-1
Do environmental changes impact soil microbial composition and function differently in different grassland habitat types?
Does environmental change affect ecosystem function consistently across landscapes, or do impacts vary with site properties? We addressed this question for functions mediated by soil microbes at a site where three very different soil types (coarse serpentine, serpentine clay and non-serpentine loam) occur in close proximity. The grasslands on these soils (hereafter, “habitats”) differ considerably in composition and productivity. Since 2010, replicate plots in each habitat have received late spring precipitation addition and NPK fertilization in a 2 x 2 factorial design. To understand whether these treatments affect potential microbial decomposition of organic matter differently across habitats, we assayed potential activities of five soil enzymes in spring 2013. Fluorometric assays measured β-glucosidase (BG), β-N-acetylglucosaminidase (NAG), and acid phosphatase (AP), and colorimetric assays measured polyphenol oxidase (PPO) and peroxidase (PER). To understand impacts on soil bacterial and archaeal community composition, we sequenced the V4 region of the 16S rRNA gene.
Results/Conclusions
Watering affected potential enzyme activity differently across habitats; it increased potential activity of NAG, PPO, and PER on non-serpentine loam and of NAG and PPO on serpentine clay, but had no effects on coarse serpentine, which has lower water holding capacity. In contrast, fertilization affected potential enzyme activity consistently across habitats; it modestly increased activity of the hydrolytic enzymes involved in C and C+N acquisition (BG, NAG), whereas activities of the oxidative enzymes (PPO, PER) and of AP were unaffected. Bacterial and archaeal composition was significantly affected by both treatments. Fertilization affected composition in a strongly habitat-dependent manner, while the effects of watering on composition were more weakly dependent on habitat. In sum, habitat-dependence varied with the type of environmental change and the metric considered, but the frequency of habitat-dependence in our results suggests that soil and associated plant community types - not just climatic factors - should be included when predicting how ecosystem functions will change across landscapes.