重庆缙云山环境因子对毛竹林土壤呼吸特征的作用

The role of environmental factors on Phyllostachys forest soil respiration characteristics in Jinyun Mountain of Chongqing

土壤呼吸是陆地生态系统碳循环的重要组成部分,对土壤呼吸特征及其与环境因子的关系的研究,有助于探索土壤呼吸的驱动因子。竹林是我国南方重要的森林类型之一,我国现有竹林520万hm2。研究竹林土壤呼吸特征有助于了解竹林土壤呼吸在陆地生态系统碳循环的特点。目前对于竹林土壤呼吸的研究上主要集中在探究土壤温度和土壤含水量等土壤因素对土壤呼吸速率的影响,但较少关注其受包括大气温度、大气相对湿度等在内的环境因子的影响。分析方法多采用单一的回归分析,不能很好地解释各因子间与土壤呼吸的相互作用。文章以重庆缙云山区毛竹(Phyllostachys pubescens)林为研究对象,采用LI-8100开路式土壤碳通量测量系统,对重庆缙云山区毛竹林土壤呼吸速率及土壤温度进行测定。采用时域反射仪(TDR)对土壤含水量进行测定。试验期间大气温度、大气相对湿度、太阳辐射、平均风速等大气因子数据来自长江三峡库区(重庆)森林生态站(缙云山自然保护区)内的自动气象站。该文研究了土壤呼吸日变化、季节变化和年变化特征以及土壤呼吸与环境因子的之间的关系。研究结果表明,(1)土壤呼吸日变化较为平缓,最大值出现在16:00—18:00,最小值出现在6:00。季节变化明显,为单峰曲线,生长季明显高于非生长季,最大值出现在7—8月。(2)单因子分析表明土壤呼吸与土壤温度和大气温度显著相关。(3)通径分析显示土壤温度、大气温度和土壤含水量都是影响土壤呼吸的主要因子,三者共同作用可以解释74.1%的土壤呼吸速率。土壤温度通过大气温度对土壤呼吸的间接影响最大。大气相对湿度对土壤呼吸直接作用较大,但其通过土壤温度和大气温度对土壤呼吸的间接作用均为负作用且数值较大,从而大气相对湿度对土壤呼吸影响不明显。

Soil respiration is an important component of carbon cycle in terrestrial ecosystem, and studies on soil respiration characteristics and effects from environmental factors help to explore the driving factors of soil respiration. As one of the major forest types in China, Bamboo forest covers 5.2 million hm2. Research on soil respiration characteristics in Bamboo forest contributes to the understanding of the characteristics soil respiration of the carbon cycle in terrestrial ecosystem. Recently, researches on soil respiration in Bamboo forest primarily emphasize the influences of soil temperature and soil moisture on soil respiration rate, but infrequently focus on effects of environmental factors, e.g. atmospheric temperature and relative humidity. The single regression analysis is the common used method, but it defectively interprets the interactions between the above factors and soil respiration. In this study, soil respiration rate and soil temperature in Phyllostachys forest in Jinyun Mountain were monitored by LI - 8100 open-path measurement system. Meanwhile, soil moisture content was obtained by Time domain reflectometry （TDR）. Other atmospheric data, like air temperature, air relative humidity, solar radiation and average wind speed were provided by the automatic weather station settled in the forest ecological station （Chongqing） within the Three Gorges Reservoir Area （the natural reserve inJinyun Mountain）. Characteristics of daily, seasonal and annual variations of soil respiration and interactions between soil respiration and environmental factors were further studied. Results show that： （I） Soil respiration in daily scale slightly varies that the peak value occurred at 16：00 or 18：00 and the nadir at 6：00. Seasonal variation is notable and features as a single-peak curve. Soil respiration rate during growth season overtop that of the non-growth season, and the maximum appears in July and August. （2） The single factor analysis showed that the soil respiration is linearly correlated to soil temperature and atmospheric temperature. （3） Path analysis indicated that soil temperature, atmospheric temperature and atmospheric humidity are the three main factors affecting soil respiration, which account for 74.1% of the total soil respiration rate. The indirect effect of soil temperature by atmospheric temperature on soil respiration was the most significant. The direct effect of atmospheric relative humidity on soil respiration is relatively great, while the indirect effects through the soil temperature and atmospheric temperature are negative and significant. Therefore, atmospheric relative humidity rarely influences soil respiration.