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植物群落对水分利用和养分利用的优化策略,土壤碳周转和氮循环过程对演替变化如何响应,森林土壤有机碳积累机制等都是森林生态学需要解决的关键问题。然而,这些生态学过程的变化在短时间内通过传统的研究手段难以被精确观测,碳氮同位素(~(13)C、~(15)N)技术的应用或许能提供更多有价值的信息。该文通过对鼎湖山森林演替序列代表性群落——马尾松(Pinus massoniana)针叶林(PF)、针阔叶混交林(MF)和季风常绿阔叶林(BF)植物-土壤碳氮同位素自然丰度的测定,分析了叶片稳定碳同位素比率(δ~(13)C)和稳定氮同位素比率(δ~(15)N)与其叶片元素含量的关系,以及叶片-凋落物-土壤δ~(13)C、δ~(15)N在演替水平和垂直方向上的变化特征。结果显示:1)主要优势树种叶片δ~(13)C与其C:N极显著正相关(p<0.01),凋落物和各层土壤δ~(13)C均表现为PF>MF>BF,沿演替方向逐渐降低;2)叶片δ~(15)N与叶片N含量正相关(p=0.05),凋落物和表层土壤(0–10 cm)δ~(15)N沿演替方向逐渐增大;3)不同演替阶段土壤δ~(13)C、δ~(15)N均沿垂直剖面呈现增大的趋势。结果表明:南亚热带地区植物群落的发展并不一定受水分利用和氮素利用的补偿制约;δ~(13)C自然丰度法的应用有助于森林土壤有机碳积累机制,尤其有助于成熟森林土壤“碳汇”机制的阐释;植物-土壤δ~(15)N值可作为评估土壤氮素有效性和生态系统“氮饱和”状态的潜在指标。
Plant community strategies for optimizing water use and nutrient use, how soil carbon turnover and nitrogen cycling respond to succession changes, and mechanisms for forest soil organic carbon accumulation are all key issues that need to be addressed in forest ecology. However, the changes of these ecological processes can hardly be accurately observed by traditional research methods in a short period of time. The application of carbon and nitrogen isotopes (~ (13) C, ~ (15) N) may provide more valuable information . In this paper, the representative forest communities of Pinus massoniana coniferous forest (PF), coniferous and broad-leaved mixed forest (MF) and monsoon evergreen broad-leaved forest (BF) The relationships between the stable carbon isotope ratio (δ ~ (13) C) and the stable nitrogen isotope ratio (δ ~ (15) N) and their leaf element contents were analyzed. Leaf-litter-soil Variation of δ ~ (13) C, δ ~ (15) N in Successional Horizontal and Vertical Direction. The results showed that: 1) δ ~ (13) C of dominant tree species had a significant positive correlation with C: N (p <0.01), and δ ~ (13) C of litter and soil layers showed PF> While the δ ~ (15) N in litter and topsoil (0-10 cm) gradually decreased along succession direction; 2) Leaf δ ~ (15) N was positively correlated with leaf N content (p = (3) The δ ~ (13) C, δ ~ (15) N of soils in different successional stages all showed an increasing trend along the vertical section. The results showed that the development of plant community in South Asia subtropics was not restricted by the compensation of water use and nitrogen use. The application of δ 13 C natural abundance method was helpful to the accumulation of organic carbon in forest soils, The interpretation of the mechanism of “carbon sink” in mature forest soil; δ ~ (15) N value of plant-soil can be used as a potential indicator to evaluate the status of soil nitrogen availability and ecosystem “nitrogen saturation”.