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氮沉降增加和降水格局改变是全球变化的两项重要内容,但是同时考虑上述两因素对温室气体CH4和CO2通量影响的原位双因子模拟研究还相当有限。本研究以长白山温带阔叶红松林土壤为研究对象,采用静态箱法研究了外施氮源(50kgN·hm-2·a-1)和增减30%降水对土壤CH4和CO2通量的影响。结果表明:施氮能抑制土壤CH4吸收,有时甚至能将土壤对CH4的吸收转为释放,但这种抑制效应只能维持5d左右,且能在一定程度上改变CH4通量和环境因子(温度、土壤pH、粘粒含量)的相关关系。降水改变未能显著影响土壤CH4通量。对CO2通量而言,施氮能降低土壤CO2排放,长白山阔叶红松林连续施氮第4年的平均抑制效应为27.4%。长期连续施氮的平均抑制效应随施氮时间延长而逐渐增大,一定年限后达到最大值。单次施氮的抑制效应随时间延长逐渐减弱,并在1个月的施氮周期末期基本消失。施氮的抑制效应和土壤充水孔隙度(WFPS)呈显著负相关关系,且升温能增强施氮对CO2释放的抑制效应并延长抑制时间。施氮、降水有可能改变土壤呼吸的温度敏感性。本研究表明,长白山森林土壤氮素尚未达到一定阈值,未来氮沉降增加将抑制CO2的释放和CH4的吸收,因此总体来看施氮抑制土壤碳排放。
The increase of nitrogen deposition and the change of precipitation pattern are two important aspects of global change. However, the in-situ two-factor simulations that take into account the above two factors’ influence on CH4 and CO2 fluxes of greenhouse gases are quite limited. In this paper, the study was conducted on the soil of broad-leaved Korean pine forest in Changbai Mountains. The effects of external nitrogen source (50kgN · hm-2 · a-1) and 30% precipitation on soil CH4 and CO2 fluxes were studied by static box method . The results showed that application of nitrogen could inhibit the uptake of CH4 in the soil and sometimes even release the uptake of CH4 by the soil, but this inhibition could only be maintained for about 5 days and could change CH4 flux and environmental factors (temperature , Soil pH, clay content). Precipitation change did not significantly affect soil CH4 flux. For CO2 flux, nitrogen application can reduce soil CO2 emissions. The average inhibitory effect of continuous N application in the fourth year of Changbai Mountain was 27.4%. The average inhibitory effect of long-term continuous nitrogen application increased with the extension of nitrogen application time, reaching the maximum after a certain number of years. The inhibitory effect of single nitrogen application gradually weakened with time, and disappeared basically at the end of one month of nitrogen application. The inhibitory effect of nitrogen application and soil water filled porosity (WFPS) showed a significant negative correlation, and warming can enhance the inhibitory effect of nitrogen on CO2 release and prolong the inhibition time. Nitrogen and precipitation may change the temperature sensitivity of soil respiration. This study shows that the Changbai Mountain forest soil nitrogen has not yet reached a certain threshold, the future increases in nitrogen deposition will inhibit the release of CO2 and CH4 absorption, so overall nitrogen inhibition of soil carbon emissions.