Leaf physiological responses to extreme droughts in Mediterranean Quercus ilex forest
Leaf physiological responses to extreme droughts in Mediterranean Quercus ilex forest
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DOI：
10.1111/j.1365-3040.2010.02193.x
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发表时间：
2010-11-01
影响因子：
7.3
通讯作者：
Letts, Matthew G.
中科院分区：
文献类型：
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作者：
Misson, Laurent;Limousin, Jean-Marc;Letts, Matthew G.
全球气候变化预计将导致地中海地区更加频繁和严重的干旱。为了了解森林对严重干旱的响应，我们利用移动雨棚研究了春季和秋季降雨排除对栎类生态系统光合作用的气孔限制(S-L)和非气孔限制(NSL)的影响。在大气需求增加和叶片发育期间进行的春季排除降雨对光合作用的影响比秋季排除降雨对光合作用的影响更大，因为秋季排除降雨是在叶片成熟和水汽压亏减少的时候进行的。NSL的相对重要性随着干旱强度的增加而增加。当总限制(T-L)达到60%时，S-L和NSL相当，但在严重干旱期间，NSL大大超过S-L，当T-L达到100%时，76%的NSL平分在叶肉导度(MCL)和生化(B-L)限制之间。降雨限制改变了叶片水势与光合作用的关系。对于严重的仲夏干旱胁迫，在相同的黎明前叶水势下，春季排除区的A(N)和V-cmax分别比对照区低75%和72%。我们的结果揭示了光合作用参数和水分胁迫之间的关系的变化，这些变化目前没有包括在用于模拟应用的干旱参数中。
Global climate change is expected to result in more frequent and intense droughts in the Mediterranean region. To understand forest response to severe drought, we used a mobile rainfall shelter to examine the impact of spring and autumn rainfall exclusion on stomatal (S-L) and non-stomatal (NSL) limitations of photosynthesis in a Quercus ilex ecosystem. Spring rainfall exclusion, carried out during increasing atmospheric demand and leaf development, had a larger impact on photosynthesis than autumn exclusion, conducted at a time of mature foliage and decreasing vapour pressure deficit. The relative importance of NSL increased with drought intensity. S-L and NSL were equal once total limitation (T-L) reached 60%, but NSL greatly exceeded S-L during severe drought, with 76% NSL partitioned equally between mesophyll conductance (MCL) and biochemical (B-L) limitations when T-L reached 100%. Rainfall exclusion altered the relationship between leaf water potential and photosynthesis. In response to severe mid-summer drought stress, A(n) and V-cmax were 75% and 72% lower in the spring exclusion plot than in the control plot at the same pre-dawn leaf water potential. Our results revealed changes in the relationship between photosynthetic parameters and water stress that are not currently included in drought parameterizations for modelling applications.