Chen Tian, Cheng Rui-Mei, Shen Ya-Fei, Xiao Wen-Fa, Wang Li-Jun, Sun Peng-Fei, Zhang Meng, Li Jing
Key Laboratory of Forest Ecology and Environment, National Forestry and Grassland Administration, Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing 100091, China.
Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China.
Ying Yong Sheng Tai Xue Bao. 2023 Oct;34(10):2601-2609. doi: 10.13287/j.1001-9332.202310.004.
We sieved soils from a plantation in the Three Gorges Reservoir area into four aggregate sizes, including aggregates of 2000-8000 μm (large macroaggregates), 1000-2000 μm (coarse aggregates), 250-1000 μm (small macroaggregates), and <250 μm (microaggregates). We analyzed the differences in the acidolyzable organic N components and net N mineralization of the aggregates under different N addition levels (30, 60, and 90 kg N·hm·a, representing by N, N and N, respectively). The results showed that net nitrification rate of the aggregates ranged from 0.30-3.42 mg N·kg and accounted for more than 80% of net nitrogen mineralization. Compared with the control, addition of 30, 60, and 90 kg N·hm·a increased total N by 24.1%-45.5%, 6.4%-34.3%, and 7.9%-42.4% in the large aggregates, coarse aggregate, small macroaggregates, and microaggregates, increased net N mineralization rate by 1.3-7.2, 1.4-6.6, and 1.8-12.9 times, but decreased the contents of available phosphorus by 9.3%-36.9%, 12.2%-56.7%, and 19.2%-61.9%, respectively. The contents of total acidolyzable N, soil organic matter, and rates of net ammonification, net nitrification, and net N mineralization increased as the aggregate size decreased, while available phosphorus contents showed an opposite trend. The levels of acid-hydrolyzable N components were ranked as acidolyzable amino acid N > acidolyzable ammonia N > acidolyzable unknown N> acidolyzable amino sugar N. Total N was the dominant contributor to the increases in acid-hydrolyzable N components. Results of stepwise multiple regression analyses showed that acidoly-zable amino acid N and acidolyzable amino sugar N were predictors of net ammonification rate. Acidolyzable amino sugar N, acidolyzable amino acid N, and acidolyzable ammonia N were predictors of net nitrification, net nitrogen mineralization rate, and net nitrogen mineralization accumulation. The physical structure of aggregates was associa-ted with soil net N mineralization. Addition of N increased the contents and bioavailability of acidolyzable organic N, a large amount of which contributed to soil organic matter levels and the decrease in available phosphorus.
