Interpreting the dependence of soil respiration on soil temperature and water content in a boreal aspen stand
Interpreting the dependence of soil respiration on soil temperature and water content in a boreal aspen stand
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DOI：
10.1016/j.agrformet.2006.08.003
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发表时间：
2006-11-30
影响因子：
6.2
通讯作者：
Nesic, Zoran
中科院分区：
文献类型：
--
作者：
Gaumont-Guay, David;Black, T. Andrew;Nesic, Zoran
2001年1月至12月在一个成熟的颤抖的白杨站位于加拿大北部森林的南部边缘的土壤CO2排放的连续半小时测量被用来调查土壤呼吸（RS）的季节和昼夜依赖于土壤温度（TS）和水分含量（θ）。日平均R-s从2月的最小值0.1 μ mol m（-2）s（-1）到7月中旬的最大值9.2 μ mol m（-2）s（-1）不等。2cm深度的日平均T-s是解释R-s时间变化的主要变量，Arrhenius和Q（10）响应函数之间没有发现差异来描述季节关系。10 ℃时的R-s（R-s10）和季节时间尺度下计算的R-s的温度敏感性（Q（10 Rs））分别为3.8 μ mol m（-2）s（-1）和3.8。日平均R-s（RsN）的温度归一化表明，θ在0-15 cm的土壤层是次要变量，占R-s的时间变化在生长季节。在0-15 cm土层，日降雨量与土壤水场容量呈明显的两个阶段（θ（fc），类似于0.30 m（3）m（-3））：（1）当θ降低到θ（fc）以下时，RsN强烈降低，这反映了微生物分解的减少，以及（2）当θ增加到θ（fc）以上时，R-sN略微降低，在2cm深度，半小时R-s与T-s的日变化通常是反相的，这导致了两个变量之间存在较强的日滞后。在生长季节期间，根据每半小时一次的夜间2 cm深度（当土壤稳定冷却时）的R-s和T-s测量值计算的每日夜间R-s 10和Q（10 Rs）参数变化很大，范围分别为6.8 - 1.6 μ mol m（-2）s（-1）和5.5 - 1.3。平均而言，每日夜间R-s10（4.5 μ mol m（-2）s（-1））和Q（10 Rs）（2.8）分别高于和低于从季节关系获得的值。这些参数的日变化与0-15 cm土层的θ变化高度相关，在低θ时R-s10和Q（10 Rs）值有降低的趋势。总体而言，使用季节性R-s10和Q（10 Rs）参数导致高估了干旱条件下半小时R-s（Delta R-s）的日范围，这支持了R-s的短期温度敏感性在低θ期间较低的发现。使用每日夜间R-s10和Q（10 Rs）参数对模拟这些期间的Delta R-s有很大帮助，但并没有改善全年半小时R-s的估计，因为它不能解释昼夜滞后效应。(c)2006 Elsevier B. V.保留所有权利。
Continuous half-hourly measurements of soil CO2 efflux made between January and December 2001 in a mature trembling aspen stand located at the southern edge of the boreal forest in Canada were used to investigate the seasonal and diurnal dependence of soil respiration (R-s) on soil temperature (T-s) and water content (theta). Daily mean R-s varied from a minimum of 0.1 mu mol m(-2) s(-1) in February to a maximum of 9.2 mu mol m(-2) s(-1) in mid-July. Daily mean T-s at the 2-cm depth was the primary variable accounting for the temporal variation of R-s and no differences between Arrhenius and Q(10) response functions were found to describe the seasonal relationship. R-s at 10 degrees C (R-s10) and the temperature sensitivity of R-s (Q(10Rs)) calculated at the seasonal time scale were 3.8 mu mol m(-2) s(-1) and 3.8, respectively. Temperature normalization of daily mean R-s (RsN) revealed that theta in the 0-15 cm soil layer was the secondary variable accounting for the temporal variation of R-s during the growing season. Daily RsN showed two distinctive phases with respect to soil water field capacity in the 0-15 cm layer (theta(fc), similar to 0.30 m(3) m(-3)): (1) RsN was strongly reduced when theta decreased below theta(fc), which reflected a reduction in microbial decomposition, and (2) R-sN slightly decreased when theta increased above theta(fc), which reflected a restriction of CO2 or O-2 transport in the soil profile.Diurnal variations of half-hourly R-s were usually out of phase with T-s at the 2-cm depth, which resulted in strong diurnal hysteresis between the two variables. Daily nighttime R-s10 and Q(10Rs) parameters calculated from half-hourly nighttime measurements of R-s and T-s at the 2-cm depth (when there was steady cooling of the soil) varied greatly during the growing season and ranged from 6.8 to 1.6 mu mol m(-2) s(-1) and 5.5 to 1.3, respectively. On average, daily nighttime R-s10 (4.5 mu mol m(-2) s(-1)) and Q(10Rs) (2.8) were higher and lower, respectively, than the values obtained from the seasonal relationship. Seasonal variations of these daily parameters were highly correlated with variations of theta in the 0-15 cm soil layer, with a tendency of low R-s10 and Q(10Rs) values at low theta. Overall, the use of seasonal R-s10 and Q(10Rs) parameters led to an overestimation of daily ranges of half-hourly R-s (Delta R-s) during drought conditions, which supported findings that the short-term temperature sensitivity of R-s was lower during periods of low theta. The use of daily nighttime R-s10 and Q(10Rs) parameters greatly helped at simulating Delta R-s during these periods but did not improve the estimation of half-hourly R-s throughout the year as it could not account for the diurnal hysteresis effect. (c) 2006 Elsevier B.V. All rights reserved.