Land-Use Change and Biogeochemical Controls of Methane Fluxes in Soils of Eastern Amazonia
Land-Use Change and Biogeochemical Controls of Methane Fluxes in Soils of Eastern Amazonia
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DOI：
10.1007/s100210000009
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发表时间：
2000
期刊：
影响因子：
3.7
通讯作者：
L. Verchot;E. Davidson;J. H. Cattanio;I. Ackerman
中科院分区：
文献类型：
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作者：
L. Verchot;E. Davidson;J. H. Cattanio;I. Ackerman
热带土壤每年消耗15-35 Tg的大气甲烷（CH 4），其中热带土壤占10%-20%，尽管热带森林砍伐可能正在改变土壤汇。本研究的目的是（a）量化亚马逊河流域东部原始林、次生林、活跃牧场和退化牧场土壤CH 4通量的差异;（B）研究土壤CH 4通量的控制机制，包括氮的有效性、气相传输和土壤呼吸。在一个牧场Fazenda Vitória，基于月度测量的年吸收量估计值（千克CH 4 ha − 1 y −1）为：原始森林，2.1;次生林，1.0;活跃牧场，1.3;退化牧场，3.1。与原始森林相比，活跃牧场的年吸收量较低，这是由于CH 4生产在潮湿的季节在牧场土壤中，这与其他研究的结果是一致的。与此相反，退化草地从来没有CH 4源。表示吸收为负通量和排放为正通量，CH 4通量与CO2通量呈正相关，表明根和微生物呼吸在生产性牧场，并在较小程度上在原始森林，有助于形成厌氧微站点CH 4产生，而这种生产力是不存在的退化牧场。在所有的土地利用方式中，大气CH 4的吸收速率在旱季大于在雨季，表明土壤水分含量和气体输送对CH 4通量的重要性。相对于桑迪土壤的报告速率，这些粘土的年吸收速率较低，这也与土壤内的气体运输是一个限制因素相一致。氮的有效性指数没有与CH 4通量，表明抑制CH 4氧化是不是一个重要的机制，解释土地利用之间的差异。在另一个牧场，Fazenda Agua Parada，牧场年龄没有显着的影响，观察到沿着牧场年龄的时序。我们的结论是，土地利用变化可以增加或减少CH 4的土壤汇，这取决于干湿季的持续时间，季节性降水对气相运输的影响，以及在每个土地利用植被的物候和相对生产力。
Tropical soils account for 10%–20% of the 15–35 Tg of atmospheric methane (CH4) consumed annually by soils, although tropical deforestation could be changing the soil sink. The objectives of this study were (a) to quantify differences in soil CH4fluxes among primary forest, secondary forest, active pasture, and degraded pasture in eastern Amazonia; and (b) to investigate controlling mechanisms of CH4fluxes, including N availability, gas-phase transport, and soil respiration. At one ranch, Fazenda Vitória, annual uptake estimates (kg CH4ha−1y−1) based on monthly measurements were: primary forest, 2.1; secondary forest, 1.0; active pasture, 1.3; degraded pasture, 3.1. The lower annual uptake in the active pasture compared with the primary forest was due to CH4production during the wet season in the pasture soils, which is consistent with findings from other studies. In contrast, the degraded pasture was never a CH4source. Expressing uptake as a negative flux and emission as a positive flux, CH4fluxes were positively correlated with CO2fluxes, indicating that root and microbial respiration in the productive pastures, and to a lesser extent in the primary forest, contributed to the formation of anaerobic microsites where CH4was produced, whereas this productivity was absent in the degraded pasture. In all land uses, uptake rates of atmospheric CH4were greater in the dry season than in the wet season, indicating the importance of soil water content and gas transport on CH4fluxes. These clay soils had low annual uptake rates relative to reported rates on sandy soils, which also is consistent with gas transport within the soil being a limiting factor. Nitrogen availability indices did not correlate with CH4fluxes, indicating that inhibition of CH4oxidation was not an important mechanism explaining differences among land uses. At another ranch, Fazenda Agua Parada, no significant effect of pasture age was observed along a chronosequence of pasture ages. We conclude that land-use change can either increase or decrease the soil sink of CH4, depending on the duration of wet and dry seasons, the effects of seasonal precipitation on gas-phase transport, and the phenology and relative productivity of the vegetation in each land use.