Mechanisms behind soil N dynamics following cover restoration in degraded land in subtropical China |
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Authors: | Zheng Xiangzhou Lin Cheng Guo Baoling Yu Juhua Ding Hong Peng Shaoyun Zhang Jinbo Ireland Eric Chen Deli Müller Christoph Zhang Yushu |
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Affiliation: | 1.Institute of Soil and Fertilizer, Fujian Academy of Agricultural Sciences, Fuzhou, 350013, People’s Republic of China ;2.Changting Monitoring Station of Soil and Water Conservation, Longyan, 366300, People’s Republic of China ;3.School of Geography Sciences, Nanjing Normal University, Nanjing, 210023, People’s Republic of China ;4.School of Agriculture and Food, The University of Melbourne, Melbourne, Victoria, 3010, Australia ;5.Institute of Plant Ecology, Justus-Liebig University Giessen, Heinrich-Buff-Ring 26, 35392, Giessen, Germany ;6.School of Biology and Environmental Science and Earth Institute, University College Dublin, Belfield, Dublin, Ireland ; |
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Abstract: | Purpose Nitrogen (N) is an important nutrient for re-vegetation during ecosystem restoration, but the effects of cover restoration on soil N transformations are not fully understood. This study was conducted to investigate N transformations in soils with different cover restoration ages in Eastern China. Materials and methodsSoil samples were collected from four degraded and subsequently restored lands with restoration ages of 7, 17, 23, and 35 years along with an adjacent control of degraded land. A 15N tracing technique was used to quantify gross N transformation rates. Results and discussionCompared with degraded land, soil organic carbon (SOC) and total N (TN) increased by 1.60–3.97 and 2.49–5.36 times in restoration land. Cover restoration increased ammonium and nitrate immobilization, and dissimilatory nitrate reduction to ammonium (DNRA) by 0.56–0.96, 0.34–2.10, and 0.79–3.45 times, respectively, indicating that restoration was beneficial for N retention. There were positive correlations between SOC content and ammonium and nitrate immobilization and DNRA, indicating that the increase in soil N retention capacity may be ascribed to increasing SOC concentrations. The stimulating effect of SOC on ammonium immobilization was greater than its effect on organic N mineralization, so while SOC and TN increased, inorganic N supply did not increase. Autotrophic and heterotrophic nitrification increased with increasing SOC and TN concentrations. Notably, heterotrophic nitrification was an important source of NO3??N production, accounting for 47–67% of NO3??N production among all restoration ages. ConclusionsThe capacity of N retention was improved by cover restoration, leading to an increase in soil organic carbon and total N over time, but inorganic N supply capacity did not change with cover restoration age. |
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