引用本文:阮超越,刘小飞,吕茂奎,李晓杰,付作琴,任寅榜,黄 俊,谢锦升.杉木人工林凋落物添加与去除对土壤碳氮及酶活性的影响[J].土壤学报,2020,57(4):954-962. DOI:10.11766/trxb201808060408
RUAN Chaoyue,LIU Xiaofei,LÜ Maokui,LI Xiaojie,FU Zuoqin,REN Yinbang,HUANG Jun,XIE Jinsheng.Effects of Litter Carbon, Nitrogen and Enzyme Activity in Soil under Chinese Fir[J].Acta Pedologica Sinica,2020,57(4):954-962. DOI:10.11766/trxb201808060408
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杉木人工林凋落物添加与去除对土壤碳氮及酶活性的影响
阮超越, 刘小飞, 吕茂奎, 李晓杰, 付作琴, 任寅榜, 黄 俊, 谢锦升
福建师范大学地理科学学院
摘要:
为了解未来气候变化过程中森林生产力增加的背景下,凋落物增加如何影响土壤碳氮过程,在杉木人工林中通过模拟实验研究凋落物添加(一倍)与去除对土壤中碳氮、碳氮同位素(δ13C、δ15N)、微生物生物量碳氮(MBC、MBN)及酶活性的影响。结果表明:凋落物添加后土壤中氮获得酶(β-N-乙酰氨基葡萄糖苷酶)活性显著上升,加速对土壤中有机质的分解获取氮素;凋落物添加与去除处理对土壤碳的影响较小,土壤有机碳(SOC)与可溶性有机碳(DOC)均未发生显著变化;土壤中δ13C丰度与凋落物处理之间未呈现出相关规律性,而δ15N丰度在凋落物添加处理后显著上升。这些结果说明,凋落物处理对杉木林土壤中氮的影响较为敏感,对土壤碳的影响较小。因此,未来气候变化导致森林生产力提高、凋落物输入增加,可能会导致土壤中氮素的损失,迫使土壤微生物分泌更多的氮获得酶同植物竞争土壤氮,最终可能会造成土壤碳氮循环的不平衡,对整个生态系统造成严重影响。
关键词:  凋落物处理  土壤碳氮同位素  酶活性
基金项目:国家重点研发计划项目(2016YFD0600204)和国家自然科学基金项目(U1405231)
Effects of Litter Carbon, Nitrogen and Enzyme Activity in Soil under Chinese Fir
RUAN Chaoyue, LIU Xiaofei, LÜ Maokui, LI Xiaojie, FU Zuoqin, REN Yinbang, HUANG Jun, XIE Jinsheng
School of Geographical Science, Fujian Normal University
Abstract:
【Objective】Climate change triggers variation of soil net primary productivity, which are likely to affect litter input to forest soil. Litter is an important source of nutrients for plants and soil microorganisms in forest ecosystems and may also alter stocks and cycling of soil carbon (C) and nitrogen (N). However, so far little has been found in the literature about responses of soil C and N to litter input in subtropical forests. This study aims to understand how soil C and N respond to increased litter input in a Chinses fir plantation in South China, caused by climate change. 【Method】In this study, a four-year field experiment, designed to have two plot, Plot A with litter kept on the soil and Plot B with litter removed, was carried out in a Chinese fir plantation in South China. Soil samples were collected from the plots at the end of the experiment and analyzed for soil C and N and their isotopes (δ13C, δ15N), enzyme activity microbial biomass C and N (MBC, MBN), as well as N-acquiring enzymes. 【Result】Results show that Plot A significantly increased activity of soil N-acquiring enzyme activity (β-N-acetylglucosaminidase) and hence accelerated decomposition of soil organic matter. Therefore it was found that litter triggered decline of soil ammonium, nitrate N and DON, but barely affected soil MBC and MBN, which is probably because litter intensified the competition of microbes with plants for soil N, so soil microbe released more N-acquiring enzyme to meet their demand for N. In Plot A phenol oxidase and peroxidase increased in activity,while in Plot B they decreased in activity, which indicates that soil microbes tend to decompose Chinese fir litter rather than soil organic matter as energy to acquire N. In Plot A soil organic C and dissolvable organic C did not vary much, which indicates that litter does not have much impact on carbon in the soil. Litter did not have much impact on soil δ13C either, but did, by significantly increasing soil δ15N. Soil δ15N is an indicator of openness of soil N system. The higher the soil δ15N, the more open the soil N system, the more likely the occurrence of N loss, which indicates that litter accelerates soil N mineralization and loss. Besides, it was also found that in Plot B β-glucosidase and cellulolytic enzyme declined in activity, which indicates that litter removal may downregulate soil C recycling rate. 【Conclusion】Based on the findings of the experiment, it could be concluded that 1) litter significantly affects soil N, but not soil C, which indicates that soil N is more sensitive to changes in litter input than soil C; 2) Litter may alter the soil microbial environment of the Chinese fir plantation and enhance root growth and N uptake of the plant, thus leading to intensified competition between soil microbes and plants for soil N and decline of soil N in content; 3) As Chinese fir litter is high in C/N, soil microbes need to excrete more soil phenol oxidase and peroxidase activity to decompose fresh litter for energy to compete for soil N. Therefore, climate changes cause variation of litter production in Chinese fir forest, which in turn produces different impacts on recycling of soil C and N, thus disturbing balance of soil C and N in subtropical coniferous forests.
Key words:  Litter treatment  Soil carbon and nitrogen isotopes  Enzyme activity