Spatial patterns of microbial nitrogen genes along precipitation gradient in different temperate grasslands of Inner Mongolia, China

Abstract Background: Despite the importance of microorganisms in soil nitrogen (N) cycling, studies on spatial patterns of microbial N genes in the temperate grassland are still lacking, whose productivity is limited by N. Here, we investigated microbial N genes from 60 temperate grassland sites across 1 161 km in Inner Mongolia, China. Results: All N gene abundances tended to decrease from northeast to southwest, consistent with precipitation change but contrary to temperature trend. Most N gene abundances increased with rising precipitation when < 321 or 403 mm, but remained stable after breaking points, indicating non-linear saturation curves dominated response patterns. Moreover, decay relationships were discovered for N gene community over geographic distance, whose effect was direct in temperate desert steppe but indirect via environmental heterogeneity in temperate meadow and typical steppe. Representativeness of geographic distance on historical-contingency was dominant only in temperate meadow (81.2%). N gene community similarity decay was mainly attributed to plant community (76.98%), with wider range, in typical steppe; while contemporary-disturbance was the attributor more important in temperate meadow (29.41%). Conclusions: Overall, we discovered non-linear patterns of N genes along precipitation gradient, and quantified attributions of geographic distance, plant community, historical-contingency and contemporary-disturbance to N gene community similarity decay, clearly ecosystem-dependent.