Long-term net transformation and quantitative molecular mechanisms of soil nitrogen during natural vegetation recovery of abandoned farmland on the Loess Plateau of China

Honglei Wang; Na Deng; Duoyang Wu; Shu Hu; Meng Kou

doi:10.1016/j.scitotenv.2017.07.014

Long-term net transformation and quantitative molecular mechanisms of soil nitrogen during natural vegetation recovery of abandoned farmland on the Loess Plateau of China

Sci Total Environ. 2017 Dec 31:607-608:152-159. doi: 10.1016/j.scitotenv.2017.07.014. Epub 2017 Jul 27.

Authors

Honglei Wang¹, Na Deng², Duoyang Wu², Shu Hu², Meng Kou³

Affiliations

¹ State Key Laboratory of Soil Erosion and Dry Land Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A & F University, Yangling 712100, Shaanxi, China. Electronic address: wanghonglei@nwsuaf.edu.cn.
² State Key Laboratory of Soil Erosion and Dry Land Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A & F University, Yangling 712100, Shaanxi, China.
³ College of Natural Resources & Environment and History & Culture, Xianyang Normal University, Shaanxi, Xianyang 712000, China.

PMID: 28689119
DOI: 10.1016/j.scitotenv.2017.07.014

Abstract

The availability of nitrogen (N) can alter vegetation species composition and diversity in degraded ecosystems. A comprehensive understanding of the dynamic fate of ammonium (NH₄⁺-N) and nitrate (NO₃^--N) processing and the underlying mechanisms are still lacking, particularly in arid to semi-arid degraded ecosystems. We compared and quantified the changes in the rates of net ammonification (R_a), nitrification (R_n) and total mineralization (R_m) and the abundance of bacteria, archaea, and microbial genes related to N transformation on the northern Loess Plateau of China across a 40-year chronosequence of farmland undergoing spontaneous restoration. We found that R_a, R_n, and R_m decreased in grassland soils (0-30-y sites) of different ages and exhibited significant increases at the 40-y sites. The capabilities of the soil to deliver NH₄⁺-N and NO₃^--N were not a limiting factor during the growing season after 40years of vegetation recovery. Soil mineral nitrogen may be not suitable for predicting and assessing the long-term (approximately 40years) restoration success and progress. The abundance of functional N genes showed differences in sensitivity to natural vegetation recovery of abandoned farmland, which likely reflects the fact that the multi-pathways driven by N functional microbial communities had a large influence on the dynamic fate of NH₄⁺-N and NO₃^--N. Quantitative response relationships between net N transformation rates and microbial genes related to N transformation were established, and these relationships confirmed that different N transformation processes were strongly linked with certain N functional genes, and collaboratively contributed to N transformation as vegetation recovery progressed. Specifically, R_a was controlled by AOA-amoA, AOB-amoA, and nxrA; R_n was governed by napA, narG, nirK, nirS, and nosZ; and R_m was controlled by nifH, apr, AOA-amoA, AOB-amoA, nirS, and nirK.

Keywords: Denitrification; Functional gene; Grassland; Loess Plateau; Nitrification.

MeSH terms

Archaea
Bacteria
China
Environmental Restoration and Remediation*
Farms*
Nitrification
Nitrogen / chemistry*
Nitrogen Cycle*
Oxidation-Reduction
Soil / chemistry*
Soil Microbiology

Substances

Soil
Nitrogen