黄土高原子午岭林区两种天然次生林植物叶片-凋落叶-土壤生态化学计量特征
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国家自然科学基金面上项目(41671280);水利部公益性行业科研专项经费项目(201501045)


C:N:P stoichiometry characteristics of plants-litter-soils in two kind types of natural secondary forest on the Ziwuling region of the Loess Plateau
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    摘要:

    了解我国黄土高原子午岭林区两种天然林下植物叶片-凋落叶-土壤生态化学计量特征,有助于人们更深入地认识黄土高原子午岭天然次生林生态系统养分循环规律和系统稳定机制。结果表明:(1)辽东栎和白桦两种植物叶片碳、氮、磷平均含量为468.6、17.1、2.1 g/kg;凋落叶碳、氮、磷平均含量为457.3、12.5、1.6 g/kg;土壤碳、氮、磷平均含量分别为17.6、1.4、0.5 g/kg。(2)白桦叶片N、P含量之间Ⅱ类线性回归斜率大于1(P=0.07),表明白桦叶片建成过程中存在N、P元素按比例投入的依赖。白桦凋落叶N、P含量之间的Ⅱ类线性回归斜率显著小于1(P < 0.05),两种天然次生林凋落叶整体N、P含量之间的Ⅱ类线性回归斜率也显著小于1(P < 0.05),反映了凋落叶中单位P含量与单位N含量间不存在等速损耗关系。(3)黄土高原子午岭两种天然次生林凋落叶氮含量与土壤氮含量具有显著相关性(P < 0.01),表明凋落叶分解对土壤氮库有增加作用。相比于凋落叶,植物叶片磷含量与土壤磷含量具有较紧密的关系,表现为高的土壤P含量则植物叶片也具有较高的P含量。黄土高原子午岭林区两种天然次生林下土壤有机质具有较快的矿化作用。(4)辽东栎作为植被演替到顶极群落的优势物种,其凋落叶C:N值为26.7远低于白桦凋落叶C:N值44.9(P < 0.05),有利于微生物对凋落叶的分解。两种天然次生林的植物叶片N:P均值为7.97<14,低于全国和全球尺度的其他研究结果,表明这两种天然次生林主要受N限制。

    Abstract:

    The objectives of this study were to characterize the C:N:P stoichiometry of the "plant-litter-soil" continuum and the nutrient resorption efficiency of plants, which contributes to a better understanding of nutrient cycling and stability in the Ziwuling forest-ecosystems on the Loess Plateau of China. Two types of natural secondary forest sites were selected in the Ziwuling region of the Loess Plateau and the contents of carbon (C), nitrogen (N), and phosphorus (P) concentrations in plants, litter and soils were detected. In the present study, the ecological stoichiometry of the plants-litter-soil continuum, for two types of natural secondary forest——Quercus wutaishanica and Betula platyphylla, shows leaf C, N and P concentrations averaged 468.6, 17.1, and 2.1g/kg, respectively; The C, N and P concentrations were 457.3, 12.5, 1.6 g/kg in the litter-fall; the soil C, N and P content averaged 17.6, 1.4, and 0.5 g/kg. The type Ⅱ (standardised major axis, SMA) regression slope for N vs. P in leaves of B. platyphylla was higher than 1 (P=0.07), indicating an N investment accomplished by P enrichment in fresh leaves. In contrast, the slope for N vs. P in litterfall of B. platyphylla was statistically < 1 (P < 0.05), and the type Ⅱ regression slope for N vs. P in litterfall of the two species was statistically < 1 (P < 0.05) demonstrating an uneven loss velocity in the litterfall unit N and P content. This means that the process of litterfall decomposition accompanying the loss of P was not lead to the N loss. A positive correlation was observed between litterfall N and soil N (P < 0.01) among two forest types, indicated an increases in the soil N pool as affected by litterfall decomposition. Leaf and soil P was more closely related to each other than either one was to litterfall P. And a rapid mineralization of soil organic matter occurred in both natural secondary forests in the Ziwuling region of the Loess Plateau. The C:N ratio in Q. wutaishanica was 26.7 in litter, which was much lower than the ratio of 44.9 observed for B. platyphylla (P < 0.05). The mean leaf N:P ratio for the two types of natural secondary forest was 7.9, which was below national and global scales found in other research, indicating that the two types of natural secondary forest were N limited. Q. wutaishanica was restricted also by N, but it did not have a high N resorption efficiency, which could be attributed to an inherent characteristic of the species.

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王宝荣,曾全超,安韶山,张海鑫,白雪娟.黄土高原子午岭林区两种天然次生林植物叶片-凋落叶-土壤生态化学计量特征.生态学报,2017,37(16):5461~5473

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