Impact of unusually wet permafrost soil on understory vegetation and CO2 exchange in a larch forest in eastern Siberia
Impact of unusually wet permafrost soil on understory vegetation and CO2 exchange in a larch forest in eastern Siberia
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DOI：
10.1016/j.agrformet.2018.11.025
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发表时间：
2019-02
影响因子：
6.2
通讯作者：
A. Kotani;A. Saito;A. Kononov;R. Petrov;T. Maximov;Y. Iijima;T. Ohta
中科院分区：
文献类型：
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作者：
A. Kotani;A. Saito;A. Kononov;R. Petrov;T. Maximov;Y. Iijima;T. Ohta
本研究调查了西伯利亚东部勒拿河流域中部落叶松优势林内部和上方10年（2005-2014年）的二氧化碳交换。在2005-2009年暖季期间，湿润土壤状况（例如在活土层（上层永久冻土层的季节性解冻土层）中发现的土壤含水量异常高，接近饱和，部分地表积水）延长了。在随后的几年中，接近地面的土层变得干燥（约10%的体积含水量），尽管较深的部分保持相对湿润（约30%）。我们定量比较了整个森林和林下co2交换，以检测土壤水分过多对林下植被和林下植被的单独影响。半小时co2通量（即白天和夜间生态系统净交换）的常规光响应函数和温度响应函数适用于林下植被观测。光响应函数在两个水平上的拟合参数比较表明，林下植被在光饱和条件下最大净生态系统交换（NEE）较小，而在弱光条件下响应较大。从湿土期到干土期，林下co2交换增加了总初级生产（GPP）的46% （1.3 g C m−2d−1）和生态系统呼吸（ER）的29% (1.2 g C m−2d−1)，而生态系统尺度通量没有变化趋势。这些增加是由于林下生物量的增加，冠层内环境中充足的光照和土壤水分的变化以及湍流混合的增强。落叶松贡献的减少可以通过林下生长和活动层剩余水分来弥补，表明落叶松与林下的相互作用支持了该森林生态系统碳循环的稳定性。
This study investigated the CO2exchange over a 10-year period (2005–2014) inside and above a larch-dominant forest in the central Lena river basin, eastern Siberia. A wet-soil condition, such as that found in the active layer (seasonally thawed soil layer of upper permafrost), containing unusually high soil water close to saturation and partial surface waterlogging, was prolonged during the warm season of 2005–2009. In later years, the soil layer closer to the ground surface became dry (∼10% volumetric water content), although the deeper part remained relatively wet (∼30%). We quantitatively compared the whole forest and the understory CO2exchanges to detect the separate effects of excessive soil waters on the overstory and understory vegetation. The conventional light and temperature response functions for half-hourly CO2fluxes, that is, the net ecosystem exchange of daytime and night-time, respectively, were applicable to the understory observations. Comparison of the fitting parameters of the light response function at two levels revealed a smaller maximum net ecosystem exchange (NEE) under light saturation with a steep response under weak light conditions for the understory. The CO2exchanges at the understory increased from the wet-soil period to the drying soil period by 46% (1.3 g C m−2d−1) of gross primary production (GPP) and 29% (1.2 g C m−2d−1) of ecosystem respiration (ER), while no trend was found in the ecosystem scale fluxes. These increases were due to an increasing understory biomass, changes in plentiful light and soil water in the inside-canopy environments, and enhanced turbulent mixing. The decline in the larch contribution could be compensated for by the understory growth and the remaining wetness of the active layer, which indicated that the interactions between the larch and the understory supported the stability of carbon cycles in this forest ecosystem.