Zhu Qilin, Liu Lijun, Wang Chengzhi, Wan Yunxing, Yang Ruoyan, Mou Jinxia, Liu Juan, Wu Yanzheng, Tang Shuirong, Zhu Tongbin, Meng Lei, Zhang Jinbo, Elrys Ahmed S
College of Tropical Crops, Hainan University, Haikou, 570228, China.
College of Resource and Environment Science, Yunnan Agricultural University, Kunming, 650201, China.
Environ Pollut. 2023 Oct 15;335:122370. doi: 10.1016/j.envpol.2023.122370. Epub 2023 Aug 14.
Converting natural forests to managed ecosystems generally increases soil nitrous oxide (NO) emission. However, the pattern and underlying mechanisms of NO emissions after converting tropical forests to managed plantations remain elusive. Hence, a laboratory incubation study was investigated to determine soil NO emissions of four land uses including forest, eucalyptus, rubber, and paddy field plantations in a tropical region of China. The effect of soil carbon (C) and nitrogen (N) fractions on soil NO emissions and related functional genes was also estimated. We found that the conversion of natural forests to managed forests significantly decreased soil NO emissions, but the conversion to paddy field had no effect. Soil NO emissions were controlled by both nitrifying and denitrifying genes in tropical natural forest, but only by nitrifying genes in managed forests and by denitrifying genes in paddy field. Soil total N, extractable nitrate, particulate organic C (POC), and hydrolyzable ammonium N showed positive relationship with soil NO emission. The easily oxidizable organic C (EOC), POC, and light fraction organic C (LFOC) had positive linear correlation with the abundance of AOA-amoA, AOB-amoA, nirK, and nirS genes. The ratios of dissolved organic C, EOC, POC, and LFOC to total N rather than soil C/N ratio control soil NO emissions with a quadratic function relationship, and the local maximum values were 0.16, 0.22, 1.5, and 0.55, respectively. Our results provided a new evidence of the role of soil C and N fractions and their ratios in controlling soil NO emissions and nitrifying and denitrifying genes in tropical soils.
将天然林转变为人工管理的生态系统通常会增加土壤一氧化二氮（N₂O）的排放。然而，热带森林转变为人工种植园后N₂O排放的模式及潜在机制仍不清楚。因此，开展了一项实验室培养研究，以测定中国热带地区森林、桉树、橡胶和稻田种植园这四种土地利用方式下的土壤N₂O排放。还评估了土壤碳（C）和氮（N）组分对土壤N₂O排放及相关功能基因的影响。我们发现，天然林转变为人工林显著降低了土壤N₂O排放，但转变为稻田则没有影响。热带天然林中土壤N₂O排放受硝化和反硝化基因共同控制，而人工林中仅受硝化基因控制，稻田中仅受反硝化基因控制。土壤全氮、可提取硝酸盐、颗粒有机碳（POC）和水解性铵态氮与土壤N₂O排放呈正相关。易氧化有机碳（EOC）、POC和轻组有机碳（LFOC）与氨氧化古菌amoA（AOA - amoA）、氨氧化细菌amoA（AOB - amoA）、亚硝酸盐还原酶基因nirK和nirS的丰度呈正线性相关。溶解有机碳、EOC、POC和LFOC与全氮的比值而非土壤碳氮比通过二次函数关系控制土壤N₂O排放，其局部最大值分别为0.16、0.22、1.5和0.55。我们的结果为土壤C和N组分及其比值在控制热带土壤N₂O排放以及硝化和反硝化基因方面的作用提供了新的证据。
