Microsite Determines the Soil Nitrogen and Carbon Mineralization in Response to Nitrogen Addition in a Temperate Desert

Abstract

Nitrogen deposition can change the soil in N and C cycling processes. However, a general understanding of how N deposition changes C and N mineralization has not yet been reached. Soil organic C and N mineralization beneath the dominant shrubs of Haloxylon ammodendron and between the shrubs in response to two levels of N addition (2.5 gN m−2 and 5 gN m−2 per year) were investigated in the 1st, 4th, and 9th year of N addition in a temperate desert of northern China. N addition promoted soil N mineralization (RmN), and the nitrification rate (RNN) increased C mineralization in the interplant and decreased it beneath shrubs. N addition increased soil microbial biomass C (Cmic), N (Nmic), and PLFAs in the interplant, and decreased it beneath shrubs. RmN and RNN were related to Nmic, and RCM was related to Cmic and the total PLFAs. N addition increased the fungal biomass alongside the ratio of fungal to bacterial PLFAs in the interplants while decreasing them beneath shrubs. Our results support how N addition can increase soil N mineralization and nitrification, but the effects on soil C mineralization are dependent on the amount of nitrogen addition, the soil’s available carbon content, and water. Finally, the divergent responses of microbial communities to N addition between microsites suggest that the “fertile islands” effects on nutrients and microbial biomass are important when estimating feedbacks of C and N cycling to projected N deposition in the desert ecosystem.

Snow-cover loss attenuates the effects of N addition on desert nutrient cycling and microbial community

“…Winter snowfall influences the establishment and development of BSCs in temperate desert regions of China ( Zhao et al., 2016a ), which has a significant impact on the dynamics of soil nutrients and microbial biomass ( Zhao et al., 2018 ), and provides conditions for their survival in hostile situations ( Hui et al., 2016 ). Higher soil moisture under snow-cover promotes net N mineralization, which in turn increases soil N availability and alleviates N limitation of the soil microbial community ( Zhang et al., 2015 ; Chen et al., 2023 ). The increased snow-cover alters the structural composition and functional communities of BSCs by increasing the content of soluble proteins and photosynthetic pigments ( Hui et al., 2018 ).…”