Patterns of natural 15N abundance in the leaf-to-soil continuum of tropical rain forests differing in N availability on Mount Kinabalu, Borneo
Patterns of natural 15N abundance in the leaf-to-soil continuum of tropical rain forests differing in N availability on Mount Kinabalu, Borneo
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DOI：
10.1023/a:1004853915544
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发表时间：
2001-02-01
期刊：
影响因子：
4.9
通讯作者：
Iwamoto, K
中科院分区：
文献类型：
--
作者：
Kitayama, K;Iwamoto, K
我们调查了自然丰度的N-15的太阳叶和其他组成部分的热带雨林海拔序列的8个网站，形成一个梯度的土壤N的可用性与不同的外生菌根丰度山。婆罗洲，京那巴鲁。我们调查了土壤氮的有效性和外生菌根丰度相关的N-15丰富的生态系统组件。δ N-15值（N-15相对于N-14的丰度）在每个地点以下列顺序一致地增加：阳生叶、落叶、细根和从较浅的有机到较深的矿质土壤层。所有地点的枯枝落叶层-表土界面都发生了N-15的富集（每千份三角洲N-15中3-6份），并且富集的幅度与树叶中N-15的消耗呈负相关，无论外生菌根丰度如何。叶片δ N-15值与其N浓度呈显著正相关。叶片（凋落物和根）三角洲N-15值与NO3的有效性呈正相关，与NH 4的有效性呈负相关。叶片三角洲N-15与叶片N和NO3有效性的两个正相关性与假设不一致，即更强的硝化作用（因此更大的硝酸盐有效性）产生更多的N-15耗尽活性无机N库。通过外生菌根的植物N的通道过程中的同位素分馏可能解释的正相关性的叶面三角洲N-15和N浓度，但是，这种机制不能完全解释在我们的情况下，因为强大的叶面N-15耗尽发生在缺乏外生菌根的网站。另外，正相关的网站之间反映了紧密的N循环。强烈的硝化作用和相关的同位素分馏可能发生在N-丰富的网站和随后从系统中去除NO3可以减少同位素“轻”N在这些网站。
We investigated the natural abundance of N-15 in sun leaves and other components of tropical rain forests on altitudinal sequences of eight sites that form a gradient of soil N availability with varying ectomycorrhizal abundances on Mt. Kinabalu, Borneo. We investigated how soil N availability and ectomycorrhizal abundance related to the N-15 abundance of ecosystem components. delta N-15 values (N-15 abundance relative to N-14) increased consistently in the following order at each site: sun leaves, leaf litter, fine roots and from shallower organic to deeper mineral soil horizons. Enrichment (3-6 parts per thousand delta N-15) of N-15 occurred at the litter-topsoil interface at all sites, and the magnitude of the enrichment correlated negatively with N-15 depletion in the foliage, irrespective of ectomycorrhizal abundance. Foliar delta N-15 values significantly positively correlated with their N concentrations. Foliar (and litter and root) delta N-15 values correlated positively with NO3 availability, and negatively with NH4 availability. The two positive correlations of foliar delta N-15 with foliar N and NO3 availability were inconsistent with the assumption that stronger nitrification (hence a greater nitrate availability) produced a more N-15-depleted active inorganic N pool. The isotopic fractionation during the passage of N through ectomycorrhizas to plants might explain the positive correlation of foliar delta N-15 and N concentration; however, this mechanism could not fully explain the correlation in our case because strong foliar N-15 depletions occurred at the sites that lacked ectomycorrhizas. Alternatively, the positive correlation across sites reflected the tightness of N cycling. Strong nitrification and associated isotopic fractionation might have occurred at N-richer sites and the subsequent removal of NO3 from the system could decrease isotopically 'lighter' N at these sites.