Spatial-temporal variation in soil respiration in an oak-grass savanna ecosystem in California and its partitioning into autotrophic and heterotrophic components
Spatial-temporal variation in soil respiration in an oak-grass savanna ecosystem in California and its partitioning into autotrophic and heterotrophic components
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DOI：
10.1007/s10533-004-5889-6
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发表时间：
2005-03-01
期刊：
影响因子：
4
通讯作者：
Baldocchi, DD
中科院分区：
文献类型：
--
作者：
Tang, JW;Baldocchi, DD
如果不研究土壤呼吸的空间变异，将田间测量的土壤呼吸在空间上扩展到生态系统水平会存在偏差。我们利用加利福尼亚一个橡树 - 草本稀树草原生态系统独特的空间梯度（橡树间隔较宽，下方有草本层）来研究土壤呼吸的空间变异，并利用这些自然梯度根据其自养和异养成分对土壤呼吸进行划分。2001年和2002年，我们沿着两棵橡树之间42.5米的样带测量土壤呼吸，发现树冠下的土壤呼吸随着距树干基部距离的增加而降低。在开阔区域，树根对土壤呼吸没有影响。从季节上看，春季土壤呼吸增加，直至4月下旬，尽管土壤温度进一步升高，但随着土壤含水量的降低，夏季土壤呼吸下降。秋季降雨后土壤呼吸显著增加。在11月至5月中旬的草本生长季节，树下二氧化碳排放通量平均值为2.29微摩尔每平方米每秒，而开阔区域的二氧化碳排放通量为1.40微摩尔每平方米每秒。我们推断橡树根系呼吸平均为0.89微摩尔每平方米每秒，占土壤总呼吸（橡树根 + 草根 + 微生物）的39%。在5月中旬至10月的旱季，树下二氧化碳排放通量平均值为0.87微摩尔每平方米每秒，而开阔区域的二氧化碳排放通量为0.51微摩尔每平方米每秒。橡树根系呼吸为0.36微摩尔每平方米每秒，占土壤总呼吸（橡树根 + 微生物）的41%。树下和开阔区域土壤二氧化碳排放通量的季节变化模式由土壤温度和湿度驱动的双变量模型模拟。日变化模式也受树木生理的影响。基于土壤呼吸的空间梯度、郁闭度的空间分析以及模拟模型，我们将箱式测量在空间和时间上扩展到生态系统尺度。我们估计2002年开阔区域的累积土壤呼吸为394克碳每平方米每年，树下为616克碳每平方米每年，场地平均值为488克碳每平方米每年。
The spatial upscaling of soil respiration from field measurements to ecosystem levels will be biased without studying its spatial variation. We took advantage of the unique spatial gradients of an oak - grass savanna ecosystem in California, with widely spaced oak trees overlying a grass layer, to study the spatial variation in soil respiration and to use these natural gradients to partition soil respiration according to its autotrophic and heterotrophic components. We measured soil respiration along a 42.5 m transect between two oak trees in 2001 and 2002, and found that soil respiration under tree canopies decreased with distance from its base. In the open area, tree roots have no influence on soil respiration. Seasonally, soil respiration increased in spring until late April, and decreased in summer following the decrease in soil moisture content, despite the further increase in soil temperature. Soil respiration significantly increased following the rain events in autumn. During the grass growing season between November and mid-May, the average of CO2 efflux under trees was 2.29 mu mol m(-2) s(-1), while CO2 efflux from the open area was 1.40 mu mol m(-2) s(-1). We deduced that oak root respiration averaged as 0.89 mu mol m(-2) s(-1), accounting for 39% of total soil respiration ( oak root + grass root + microbes). During the dry season between mid-May and October, the average of CO2 efflux under trees was 0.87 mu mol m(-2) s(-1), while CO2 efflux from the open areas was 0.51 mu mol m(-2) s(-1). Oak root respiration was 0.36 mu mol m(-2) s(-1), accounting for 41% of total soil respiration ( oak root + microbes). The seasonal pattern of soil CO2 efflux under trees and in open areas was simulated by a bivariable model driven by soil temperature and moisture. The diurnal pattern was influenced by tree physiology as well. Based on the spatial gradient of soil respiration, spatial analysis of crown closure and the simulation model, we spatially and temporally upscaled chamber measurements to the ecosystem scale. We estimated that the cumulative soil respiration in 2002 was 394 gC m(-2) year(-1) in the open area and 616 gC m(-2) year(-1) under trees with a site-average of 488 gC m(-2) year(-1).