Biophysical controls on rhizospheric and heterotrophic components of soil respiration in a boreal black spruce stand
Biophysical controls on rhizospheric and heterotrophic components of soil respiration in a boreal black spruce stand
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DOI：
10.1093/treephys/28.2.161
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发表时间：
2008-02-01
期刊：
影响因子：
4
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
2004年，我们在一片125年生的北方黑云杉（Picea mariana (Mill.) BSP）林分中进行了一项根系排除实验，以量化土壤呼吸（Rs）的根际（R - r）和异养（R - h）组分的时间动态的物理和生物控制因素。年R - r、R - h和估算的苔藓呼吸分别为285、269和57克碳/平方米·年，分别占Rs（611克碳/平方米·年）的47%、44%和9%。在一年中观察到从以R - h为主（冬季、春季和秋季）到以R - r为主（夏季）的呼吸逐渐转变。春季土壤解冻以及随后土壤含水量（θ）的增加导致R - h小幅且持续上升，但对R - r没有影响。在生长季的其余时间，未观察到θ对Rs的任何一个组分有影响。在生长季，两个组分都随土壤温度（Ts）呈指数增长，但R - r比R - h对温度更敏感（Q10分别为4.0和3.0）。R - r的温度标准化变化与生态系统总光合作用的涡度协方差估算值高度相关，当R - r滞后24天时相关性最大。在昼夜循环内，Ts的变化与R - h的变化高度耦合，但与R - r显著解耦。在这两个时间尺度上观察到的模式强烈表明，光合产物向根际的流动是地下呼吸过程的关键驱动因素，但光合产物供应可能以多种方式控制这些过程。
We conducted a root-exclusion experiment in a 125-year-old boreal black spruce (Picea mariana (Mill.) BSP) stand in 2004 to quantify the physical and biological controls on temporal dynamics of the rhizospheric (R-r) and heterotrophic (R-h) components of soil respiration (R-s). Annual R-r, R-h and estimated moss respiration were 285, 269 and 57 g C m(-2) year(-1), respectively, which accounted for 47, 44 and 9% of Rs (6119 C m(-2) year(-1)), respectively. A gradual transition from Rh-dominated (winter, spring and fall) to R-r-dominated (summer) respiration was observed during the year. Soil thawing in spring and the subsequent increase in soil water content (theta) induced a small and sustained increase in R-h but had no effect on R-r. During the remainder of the growing season, no effect of theta was observed on either component of R-s. Both components increased exponentially with soil temperature (T-s) during the growing season, but Rr showed greater temperature sensitivity than R-h (Q(10) of 4.0 and 3.0, respectively). Temperature-normalized variations in R-r were highly correlated with eddy covariance estimates of gross ecosystem photosynthesis, and the correlation was greatest when R-r was lagged by 24 days. Within diurnal cycles, variations in T-s were highly coupled to variations in R-h but were-significantly decoupled from R-r. The patterns observed at both time scales strongly suggest that the flow of photosynthates to the rhizosphere is a key driver of below-ground respiration processes but that photosynthate supply may control these processes in several ways.