米槠天然更新次生林皆伐火烧后初期土壤呼吸日变化

Diurnal Variation of Soil Respiration after Clear-cutting and Slash Burning of Natural Regeneration Secondary Forest of Castanopsis carlesis in Subtropical China

采用IRGA法(所用仪器为LI-8100)对福建三明米槠天然更新次生林皆伐火烧后初期土壤呼吸日动态进行研究.结果表明:皆伐火烧后土壤呼吸速率日变化趋势呈单峰型,呼吸速率在11:00～13:00之间达到最大值,而在3:00～7:00达到最小值.火烧地土壤日平均呼吸速率(5.59μmol.m-2.s-1)显著高于对照地(2.27μmol.m-2.s-1)和皆伐后保留采伐剩余物地(2.30μmol.m-2.s-1).皆伐和火烧后土壤呼吸速率日变化幅度增大,尤以火烧地的最为明显(达134.6%),分别比皆伐样地(88.0%)及对照地(53.3%)高54.6%和81.3%.不同处理方式土壤呼吸与温度(5 cm土壤温度、气温)、土壤含水量的关系采用双因素模型(R=aebTWc)拟合结果优于仅考虑温度或土壤含水量的单因素模型.火烧地Q10值明显高于对照地和皆伐地.

In order to estimate clear-cutting and slash burning effects on soil carbon sequestration in subtropical China, diurnal variation of soil respiration （Rs） in residue retention （RR） and residue burnt （RB） treatments in natural regeneration secondary stand of Castanopsis carlesis were measured using the IRGA method by a LI-8100 automated soil CO2 flux system in Sanming , Fujian, China. The result showed that daily Rs showed a mono-peak trend, with its maximum rates from 11 am to 13 pm and minimum value from 3 pm to 7 pm. Mean daily Rs in RB （5.59 umol · m-2· S-1） plot was significantly higher than in the control （2.27 umol · m-2 · s-1） and RR （2. 30 umol · m-2 · s-1） plots. Also, the diurnal range of Rs was the largest in RB plot （134. 6% ）, followed by RR （88.0%） and control （53.3%） plots. Relationships between Rs and environmental variables were examined via a regression analysis. A combination of temperature （ including soil temperature at 5 cm depth and air temperature） and soil moisture content proved to be a reliable predictor of CO2 evolution in all plots. The Q10 values in RB plots were significantly higher than those in control and RR plots.