Temperature-independent diel variation in soil respiration observed from a temperate deciduous forest
Temperature-independent diel variation in soil respiration observed from a temperate deciduous forest
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DOI：
10.1111/j.1365-2486.2006.01245.x
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发表时间：
2006-11-01
影响因子：
11.6
通讯作者：
Lenhart, S.
中科院分区：
文献类型：
--
作者：
Liu, Q.;Edwards, N. T.;Lenhart, S.
土壤呼吸（R-s）对温度的响应在很大程度上取决于所关注的时间和空间尺度以及其他环境因子如何与这一响应相互作用。在许多生态系统分析中，由于难以分离共变环境响应和观测地下过程，它们通常用经验指数方程来表示。本研究的目的是通过检查2003年3月至12月在美国田纳西州橡树岭的温带落叶林中测量的R-s时间序列的日变化，量化R-s中与土壤温度无关的成分。通过将2小时连续自动室测量的土壤表面CO2流出量拟合为Q（10）函数，得到温度依赖呼吸（R-t），并绘制R-t、R-s的周期及其差值（R-i），我们发现在生长季节R-s中存在明显的温度无关成分。该组分的日循环具有明显的昼夜模式，与光合有效辐射（PAR）和气温的日变化吻合良好。冠层CO2浓度的升高导致温度无关分量的日平均速率在生长季节的不同阶段具有相似的变化规律。我们推测林分的光合作用是这种不依赖温度的呼吸成分的主要贡献者之一，尽管需要更多的实验来得出确切的结论。我们还发现，尽管与温度相关分量相比，温度无关分量的变化幅度相对较小，但温度无关分量的昼夜变化可能导致研究森林土壤呼吸温度敏感性的估计存在显著差异。因此，使用夜间测量的拟合温度依赖函数来推断白天土壤呼吸的常见做法可能低估了白天土壤呼吸。
The response of soil respiration (R-s) to temperature depends largely on the temporal and spatial scales of interest and how other environmental factors interact with this response. They are often represented by empirical exponential equations in many ecosystem analyses because of the difficulties in separating covarying environmental responses and in observing below ground processes. The objective of this study was to quantify a soil temperature-independent component in R-s by examining the diel variation of an R-s time series measured in a temperate deciduous forest located at Oak Ridge, TN, USA between March and December 2003. By fitting 2 hourly, continuous automatic chamber measurements of CO2 efflux at the soil surface to a Q(10) function to obtain the temperature-dependent respiration (R-t) and plotting the diel cycles of R-t, R-s, and their difference (R-i), we found that an obvious temperature-independent component exists in R-s during the growing season. The diel cycle of this component has a distinct day/night pattern and agrees well with diel variations in photosynthetically active radiation (PAR) and air temperature. Elevated canopy CO2 concentration resulted in similar patterns in the diel cycle of the temperature-independent component but with different daily average rates in different stages of growing season. We speculate that photosynthesis of the stand is one of the main contributors to this temperature-independent respiration component although more experiments are needed to draw a firm conclusion. We also found that despite its relatively small magnitude compared with the temperature-dependent component, the diel variation in the temperature-independent component can lead to significantly different estimates of the temperature sensitivity of soil respiration in the study forest. As a result, the common practice of using fitted temperature-dependent function from night-time measurements to extrapolate soil respiration during the daytime may underestimate daytime soil respiration.