Dynamics of carbon exchange in a Eucalyptus forest in response to interacting disturbance factors
Dynamics of carbon exchange in a Eucalyptus forest in response to interacting disturbance factors
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DOI：
10.1016/j.agrformet.2011.07.019
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发表时间：
2012-02-15
影响因子：
6.2
通讯作者：
Cleugh, H. A.
中科院分区：
文献类型：
--
作者：
Keith, H.;van Gorsel, E.;Cleugh, H. A.
森林产生的碳（C）汇取决于光合作用吸收C和呼吸损失C之间的平衡。这种平衡因环境驱动因素对这些进程的相对影响而异。在澳大利亚东南部的Tumbarumba的一个本地的桉树delegatensis森林在平均降雨量（1998-2001年）和干旱（2002-2003年和2006-2007年）的条件下，C循环的组件和动态进行了测量。在2002-03年，干旱和虫害的干扰因素相互作用，减少了光合有效叶面积的冠层。干旱期间的条件包括土壤含水量减少、温度升高和蒸汽压力不足增加。同样的低土壤水分含量发生在两个干旱时期，但在2002- 2003年持续时间更长。干旱胁迫和虫害的综合影响导致树木的生长显著下降（45-80%）和死亡率升高（5-60%）。50 000公顷森林的影响各不相同，通常生长率最高的林分死亡率最高，土壤湿度下降最多的地方死亡率最高。2002- 2003年期间增长率下降，2003- 2004年最严重，2004- 2005年恢复。2004- 2005年的死亡率仍然很高，表明压力条件的长期影响。森林中的总碳库为483 tC ha（-1），在虫害发生前的生长季节（2001-02），净碳吸收量为6.7 tC ha（-1）yr（-1）。在2003年干旱和昆虫干扰的条件下，森林在8个月内总共释放了1.7 tC ha（-1），而在2006-07年生长季节年仅干旱条件下的碳吸收量为-6.5 tC ha（-1）yr（-1），2007日历年为-5.6 tC ha（-1）yr（-1）。干旱和虫害的相互作用的压力因素导致了一个很大的不平衡，在C预算的总初级生产力减少了26%，减少了9%，在生态系统呼吸，而干旱单独有一个小得多的影响。干旱条件导致（1）天气条件打破昆虫与寄生虫和捕食者的同步，导致昆虫爆发，（2）水分胁迫使树木易受昆虫攻击，以及（3）水分胁迫限制受损后的叶片再生。气候变化和气候引起的干扰机制的变化可能会对光合作用和呼吸作用产生不同的影响，从而改变生态系统净碳交换的平衡。森林碳汇强度的降低将导致正的碳循环-气候反馈，从而增强温室效应和气候变化。皇冠版权所有（C）2011由Elsevier B. V.出版。保留所有权利。
Carbon (C) sinks created by forests depend on the balance between C uptake through photosynthesis and loss through respiration. This balance varies depending on the relative effect of environmental drivers on these processes. Components and dynamics of the C cycle were measured in a native Eucalyptus delegatensis forest at Tumbarumba in south-eastern Australia during conditions of average rainfall (1998-2001) and droughts (2002-2003 and 2006-2007). In 2002-03 there were interacting disturbance factors of dry conditions and insect damage that reduced the photosynthetically active leaf area in the canopy. Conditions during the droughts included reduced soil moisture content, higher temperatures and increased vapour pressure deficit. Similarly low soil moisture contents occurred during both drought periods, but lasted for longer in 2002-03. The combined impact of drought stress and insect damage resulted in markedly reduced growth (45-80%) and higher mortality of trees (5-60%). Impacts were variable across the 50,000 ha of forest, with mortality greatest in stands with normally highest growth rates, and in locations with greatest reductions in soil moisture. Growth rates were reduced during 2002-03, most severely in 2003-04, and recovering in 2004-05. Mortality remained high in 2004-05 indicating the prolonged effect of the stress conditions. The total C pool in the forest is 483 tC ha(-1) with net C uptake of 6.7 tC ha(-1) yr(-1) in the growing season prior to the insect attack (2001-02). Under conditions of drought and insect disturbance in 2003 the forest released a total of 1.7 tC ha(-1) over 8 months, while under conditions of drought alone carbon uptake was -6.5 tC ha(-1) yr(-1) in the growing season year of 2006-07 and -5.6 tC ha(-1) yr(-1) in the calendar year of 2007. Interacting stress factors of drought and insect damage resulted in a large imbalance in the C budget with a 26% reduction in gross primary productivity and a 9% reduction in ecosystem respiration, whereas drought alone had a much lesser effect. Drought conditions result in (1) weather conditions that break the synchronisation of insects with parasites and predators resulting in insect outbreaks, (2) moisture stress that predisposes trees to attack by insects, and (3) moisture stress that restricts leaf regeneration after damage. Climate change and climatically induced changes in disturbance regimes may affect the processes of photosynthesis and respiration differently and hence change the balance of net ecosystem C exchange. Reduced sink strength of forests will lead to positive C cycle-climate feedbacks, which enhance the greenhouse effect and climate change. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.