Soil extracellular enzyme activities and the abundance of nitrogen-cycling functional genes responded more to N addition than P addition in an Inner Mongolian meadow steppe

Hong Xiao; Helong Yang; Mengli Zhao; Thomas A Monaco; Yuping Rong; Ding Huang; Qian Song; Kun Zhao; Deping Wang

doi:10.1016/j.scitotenv.2020.143541

Soil extracellular enzyme activities and the abundance of nitrogen-cycling functional genes responded more to N addition than P addition in an Inner Mongolian meadow steppe

Sci Total Environ. 2021 Mar 10:759:143541. doi: 10.1016/j.scitotenv.2020.143541. Epub 2020 Nov 6.

Authors

Hong Xiao¹, Helong Yang¹, Mengli Zhao², Thomas A Monaco³, Yuping Rong⁴, Ding Huang¹, Qian Song¹, Kun Zhao¹, Deping Wang¹

Affiliations

¹ College of Grassland Science and Technology, China Agricultural University, Beijing 100193, China.
² College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot 010011, China.
³ USDA-ARS Forage and Range Research Laboratory, Utah State University, Logan, UT 84322-6300, USA.
⁴ College of Grassland Science and Technology, China Agricultural University, Beijing 100193, China. Electronic address: rongyuping@cau.edu.cn.

PMID: 33198996
DOI: 10.1016/j.scitotenv.2020.143541

Abstract

Nitrogen (N) and phosphorus (P) availability in soils commonly limit belowground biological processes in terrestrial ecosystems. Soil extracellular enzyme activities (EEAs) and microbial functional groups play critical roles in soil biological processes and nutrient cycling, yet their response to nutrient addition are poorly understood. To address this issue, we applied six fertilization treatments composed of combinations of N (0, 1.55, 13.95 g N m^-2 yr^-1) and P (0, 5.24 g P m^-2 yr^-1) for two years in a meadow steppe of Inner Mongolia. Soils were collected from each plot in July and August and analyzed for abundances of N-cycling genes and EEAs, and their relationships with treatments. The addition of N significantly increased C-acquisition enzyme activity and enzyme C:N and C:P ratios. Enzymatic stoichiometry indicated that N addition alleviated microbial demand for N, while it increased microbial C limitation. Microbial C and N limitation were significantly correlated with NH₄⁺-N in July, yet they were correlated with soil water content (SWC) in August. The abundance of amoA significantly increased with N addition and was positively related to mineral-N accumulation. The abundance of denitrifier genes and gaseous N loss potential were accelerated by N addition in July, while a neutral effect was observed in August. Nitrate leaching potential was significantly increased by N addition, yet it declined with P addition in July. P addition also suppressed amoA abundance of ammonia oxidizing bacteria. Partial least squares path modelling indicated that N addition positively affected microbial-C limitation, soil N-loss potential and negatively affected microbial-N limitation. P addition negatively affected soil N-loss potential. Ultimately, this study highlights the importance of soil N availability in regulating microbial metabolism and soil N-loss potential, and enhances our understanding of the mechanisms responsible for variation in microbial nutrient cycling in meadow steppe soils.

Keywords: Enzymatic stoichiometry; Functional genes; N loss potential; Nitrogen; Phosphorus; Soil enzyme activity.

MeSH terms

China
Ecosystem
Grassland
Nitrogen*
Phosphorus
Soil Microbiology
Soil*

Substances

Soil
Phosphorus
Nitrogen