Large-scale forest girdling shows that current photosynthesis drives soil respiration
Large-scale forest girdling shows that current photosynthesis drives soil respiration
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DOI：
10.1038/35081058
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发表时间：
2001-06-14
期刊：
影响因子：
64.8
通讯作者：
Read, DJ
中科院分区：
文献类型：
--
作者：
Högberg, P;Nordgren, A;Read, DJ
植物根系、其菌根真菌以及土壤中自由生活的微生物异养生物（分解者）的呼吸活动是全球碳平衡的重要组成部分，但它们的相对贡献仍不确定（1,2）。为了在北方松林中区分菌根根系呼吸和异养呼吸，我们进行了一项大规模的环剥树木实验，包括9个样地，每个样地约有120棵树。环剥树木是指在齐胸高处将树干的树皮剥至当前木质部的深度，从而在不物理干扰脆弱的根系 - 微生物 - 土壤系统的情况下，终止当前光合产物向根系及其菌根真菌的供应。在此我们报告，与未环剥的对照样地的呼吸相比，环剥在1 - 2个月内使土壤呼吸降低了约54%，并且在5天内检测到降幅高达37%。这些数值清楚地表明，当前同化物向根系的流动是土壤呼吸的关键驱动因素；然而，它们是对根系呼吸的保守估计，因为环剥增加了根系中淀粉储备的使用。我们的研究结果表明，土壤呼吸模型应纳入光合作用的测量以及光合产物向根系分配的季节性模式。
The respiratory activities of plant roots, of their mycorrhizal fungi and of the free-living microbial heterotrophs (decomposers) in soils are significant components of the global carbon balance, but their relative contributions remain uncertain(1,2). To separate mycorrhizal root respiration from heterotrophic respiration in a boreal pine forest, we conducted a large-scale tree-girdling experiment, comprising 9 plots each containing about 120 trees. Tree-girdling involves stripping the stem bark to the depth of the current xylem at breast height terminating the supply of current photosynthates to roots and their mycorrhizal fungi without physically disturbing the delicate root-microbe-soil system. Here we report that girdling reduced soil respiration within 1-2 months by about 54% relative to respiration on ungirdled control plots, and that decreases of up to 37% were detected within 5 days. These values clearly show that the flux of current assimilates to roots is a key driver of soil respiration; they are conservative estimates of root respiration, however, because girdling increased the use of starch reserves in the roots. Our results indicate that models of soil respiration should incorporate measures of photosynthesis and of seasonal patterns of photosynthate allocation to roots.