Microbial Biomass Is More Important than Runoff Export in Predicting Soil Inorganic Nitrogen Concentrations Following Forest Conversion in Subtropical China

Chao Xu, Teng-Chiu Lin, Jr-Chuan Huang, Zhijie Yang, Xiaofei Liu, Decheng Xiong, Shidong Chen, Minhuang Wang, Liuming Yang and Yusheng Yang
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Chao Xu: Fujian Provincial Key Laboratory for Plant Eco-Physiology, Fujian Normal University, Fuzhou 350007, China
Teng-Chiu Lin: Department of Life Science, National Taiwan Normal University, Taipei 11677, Taiwan
Jr-Chuan Huang: Department of Geography, National Taiwan University, Taipei 10617, Taiwan
Zhijie Yang: Fujian Provincial Key Laboratory for Plant Eco-Physiology, Fujian Normal University, Fuzhou 350007, China
Xiaofei Liu: Fujian Provincial Key Laboratory for Plant Eco-Physiology, Fujian Normal University, Fuzhou 350007, China
Decheng Xiong: Fujian Provincial Key Laboratory for Plant Eco-Physiology, Fujian Normal University, Fuzhou 350007, China
Shidong Chen: Fujian Provincial Key Laboratory for Plant Eco-Physiology, Fujian Normal University, Fuzhou 350007, China
Minhuang Wang: Department of Ecology, School of Life Sciences, State Key Laboratory of Biocontrol, Sun Yat-Sen University, Guangzhou 510275, China
Liuming Yang: Fujian Provincial Key Laboratory for Plant Eco-Physiology, Fujian Normal University, Fuzhou 350007, China
Yusheng Yang: Fujian Provincial Key Laboratory for Plant Eco-Physiology, Fujian Normal University, Fuzhou 350007, China

Land, 2022, vol. 11, issue 2, 1-15

Abstract: Elevated runoff export and declines in soil microbial biomass and enzyme activity following forest conversion are known to reduce soil inorganic nitrogen (N) but their relative importance remains poorly understood. To explore their relative importance, we examined soil inorganic N (NH 4 + and NO 3 − ) concentrations in relation to microbial biomass, enzyme activity, and runoff export of inorganic N in a mature secondary forest, young (five years old) Castanopsis carlessi and Cunninghamia lanceolate (Chinese fir) plantations, and forests developing through assisted natural regeneration (ANR). The surface runoff export of inorganic N was greater, but fine root biomass, soil microbial biomass, enzyme activity, and inorganic N concentrations were smaller in the young plantations than the secondary forest and the young ANR forests. Microbial biomass, enzyme activity, and runoff inorganic N export explained 84% and 82% of the variation of soil NH 4 + and NO 3 − concentrations, respectively. Soil microbial biomass contributed 61% and 94% of the explaining power for the variation of soil NH 4 + and NO 3 − concentrations, respectively, among the forests. Positive relationships between microbial enzyme activity and soil inorganic N concentrations were likely mediated via microbial biomass as it was highly correlated with microbial enzyme activity. Although surface runoff export can reduce soil inorganic N, the effect attenuated a few years after forest conversion. By contrast, the differences in microbial biomass persisted for a long time, leading to its dominance in regulating soil inorganic N concentrations. Our results highlight that most of the variation in soil inorganic N concentration following forest conversion was related to soil microbial biomass and that assisted natural regeneration can effectively conserve soil N.

Keywords: assisted natural regeneration; fine root biomass; forest conversion; microbial biomass; soil inorganic nitrogen; surface runoff (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2022
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