西双版纳热带季节雨林土壤呼吸季节动态及驱动因素

Seasonal Variation of Soil Respiration and Its Impact Factors in Tropical Seasonal Rainforest in Xishuangbanna, Yunnan

季节雨林是西双版纳热带森林生态系统中原始林,本研究采用挖壕沟法与红外气体分析法研究了西双版纳热带季节雨林土壤呼吸,包括根系呼吸、异养呼吸的干湿季动态变化,旨在为准确估算中国热带碳收支提供基础数据。结果表明,(1)西双版纳热带季节雨林所在的土壤温度和土壤湿度存在显著的季节变化规律,均呈倒"V"型变化趋势。不同季节0-5 cm土壤温度和湿度均显著高于5-10cm;土壤温度和湿度随着季节的变化呈先增加后降低趋势,在夏季达到最大,在冬季最小。(2)西双版纳热带季节雨林土壤总呼吸(R_s)、自养呼吸(R_a)及异养呼吸(R_h)具有明显的分层现象和季节性规律,从分层来看,不同季节0-5cm土壤总呼吸(R_s)、自养呼吸(R_a)及异养呼吸(R_h)均高于5-10cm土层;从季节性规律来看,土壤总呼吸(R_s)、自养呼吸(R_a)及异养呼吸(R_h)随着季节的变化呈先增加后降低趋势,在夏季达到最大,在冬季最小。(3)西双版纳热带季节雨林土壤总呼吸与土壤温度呈显著的指数关系,与土壤湿度呈显著的二次曲线关系,其决定系数R^2分别为0.32-0.46和0.29-0.40(P<0.05),明显低于土壤呼吸速率与土壤温度关系方程的R2值,这表明土壤呼吸速率与土壤含水量之间的相关性较弱。(4)主成分分析表明,第一主成分对原始变量的解释贡献了总方差的64.18%,负荷值最高的几个指标分别为有机碳、全氮和转化酶,第二主成分为全氮、全钾和转化酶,说明土壤温度、有机碳、全氮和蔗糖酶是西双版纳热带季节雨林土壤呼吸的主要影响因子。

This study was conducted in tropical seasonal rainforest in Xishuangbanna,Yunnan aiming at measuring soil respiration and its impact factors.The results showed that(1)Soil temperature and soil moisture had the obvious seasonal dynamics and there was a lower soil temperature and soil moisture in winter and higher in summer,and the soil temperature and soil moisture in 0.5 cm was higher than 5.10 cm.(2)Total soil respiration(Rs),soil autotrophic respiration(Ra)and soil heterotrophic respiration(Rh)had the obvious seasonal dynamics which showed increased and then decreased with seasonal variation,and Rs,Ra,Rh in 0.5 cm was higher than 5.10 cm.(3)There was a significantly exponential relationship between total soil respiration and soil temperature,and a significantly quadratic curve between total soil respiration and soil water content in 0.5 and 5.10 cm with R^2 of 0.317.0.456,0.289.0.401,which was higher than the correlation coefficient between total soil respiration and soil temperature,indicating that the effect of soil water content on soil respiration was weak than soil temperature.And(4)principal component analysis showed that the interpretation of the first principal components of original variables accounted for 64.184% of the total variance,respectively.Soil organic carbon,total nitrogen and invertase had the highest load value,and the second principal components were soil total nitrogen,total potassium and invertase,which illustrated that soil organic carbon,total nitrogen and sucrase were the main influencing factors to soil respiration in tropical seasonal rain forest in Xishuangbanna.