Water loss regulation in mature Hevea brasiliensis: effects of intermittent drought in the rainy season and hydraulic regulation
Water loss regulation in mature Hevea brasiliensis: effects of intermittent drought in the rainy season and hydraulic regulation
复制标题
DOI：
10.1093/treephys/tpr058
复制
发表时间：
2011-07-01
期刊：
影响因子：
4
通讯作者：
Cochard, Herve
中科院分区：
文献类型：
--
作者：
Ayutthaya, Supat Isarangkool Na;Do, Frederic C.;Cochard, Herve
在泰国东北部干旱易发区，研究了土壤和大气干旱对成熟橡胶树（Hevea brasiliensis，克隆RRIM 600）在雨季全冠期全树蒸腾（E-T）、叶水势（psi（L））和全树导水率（K-T）的影响。在水分充足的土壤条件下，蒸腾作用受到严格的调节，以响应高蒸发需求，即，高于参考蒸散量（ETo），类似于2.2 mm日（-1）或最大蒸汽压亏损，类似于1.8 kPa。在间歇性土壤干旱条件下，表层土壤相对可提取水小于0.4时，E-T急剧下降。晴天的中午叶水势（psi（md））不随土壤干旱而变化，并保持稳定在约-1.95 MPa，即，显示等氢行为。E-T的减少主要是由于K-T的变化。K-T在很大范围的环境条件下保持恒定，在土壤水分有效性低时急剧下降。一个简单的水力模型，将临界最小水势和全树水力传导率的响应，相对可提取的水正确模拟模式的蒸腾超过6个月。我们的结论是，一个明确的和简化的框架水力限制假设是足够的描述水分有限条件下的成熟橡胶林的水分利用规律。鉴于土壤-植物-大气途径中约束的复杂性，我们的结果证实了这种方法与综合干旱下树木整体行为的相关性。
Effects of soil and atmospheric drought on whole-tree transpiration (E-T), leaf water potential (psi(L)) and whole-tree hydraulic conductance (K-T) were investigated in mature rubber trees (Hevea brasiliensis, clone RRIM 600) during the full canopy stage in the rainy season in a drought-prone area of northeast Thailand. Under well-watered soil conditions, transpiration was tightly regulated in response to high evaporative demand, i.e., above reference evapotranspiration (ETo) similar to 2.2 mm day(-1) or maximum vapor pressure deficit similar to 1.8 kPa. When the trees experienced intermittent soil drought E-T decreased sharply when relative extractable water in the top soil was < 0.4. The midday leaf water potential (psi(md)) on sunny days did not change as a function of soil drought and remained stable at approximately -1.95 MPa, i.e., displaying isohydric behavior. The decrease in E-T was mainly due to the change in K-T. K-T remained constant over a wide range of environmental conditions and decreased sharply at low soil water availability. A simple hydraulic model incorporating critical minimum water potential and the response of whole-tree hydraulic conductance to relative extractable water correctly simulated patterns of transpiration over 6 months. We conclude that an explicit and simplified framework of hydraulic limitation hypothesis was sufficient to describe water use regulation of a mature rubber tree stand in water-limited conditions. Given the complexity of constraints in the soil-plant-atmosphere pathway, our results confirm the relevance of this approach to synthesize the overall behavior of trees under drought.