Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla Yunnan, 666303, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
New Phytol. 2015 Jan;205(1):128-36. doi: 10.1111/nph.13036. Epub 2014 Sep 29.
Lianas exhibit peak abundance in tropical forests with strong seasonal droughts, the eco-physiological mechanisms associated with lianas coping with water deficits are poorly understood. We examined soil water partitioning, sap flow, and canopy eco-physiological properties for 99 individuals of 15 liana and 34 co-occurring tree species in three tropical forests that differed in soil water availability. In the dry season, lianas used a higher proportion of deep soil water in the karst forest (KF; an area with severe seasonal soil water deficit (SSWD)) and in the tropical seasonal forest (TSF, moderate SSWD), permitting them to maintain a comparable leaf water status than trees in the TSF or a better status than trees in the KF. Lianas exhibited strong stomatal control to maximize carbon fixation while minimizing dry season water loss. During the dry period, lianas significantly decreased water consumption in the TSF and the KF. Additionally, lianas had a much higher maximum photosynthetic rates and sap flux density in the wet season and a lower proportional decline in photosynthesis in the dry season compared with those of trees. Our results indicated that access to deep soil water and strong physiological adjustments in the dry season together with active wet-season photosynthesis may explain the high abundance of lianas in seasonally dry forests.
藤本植物在季节性干旱强烈的热带森林中达到丰度峰值，但与藤本植物应对水分亏缺相关的生理生态机制仍知之甚少。我们研究了 3 个热带森林中 15 种藤本植物和 34 种伴生树种的 99 个个体的土壤水分分配、液流和冠层生态生理特性，这些森林在土壤水分可用性方面存在差异。在旱季，藤本植物在喀斯特森林（KF；季节性土壤水分严重亏缺（SSWD）地区）和热带季节性森林（TSF，中度 SSWD）中利用了更高比例的深层土壤水，从而使它们能够维持与 TSF 中树木相当的叶片水分状况，或者比 KF 中的树木状况更好。藤本植物具有强烈的气孔控制，以最大限度地固定碳，同时最大限度地减少旱季水分流失。在旱季，藤本植物在 TSF 和 KF 中显著减少了水分消耗。此外，与树木相比，藤本植物在雨季具有更高的最大光合速率和液流密度，以及在旱季光合作用的比例下降幅度更小。我们的研究结果表明，在旱季获得深层土壤水和生理上的强烈调整，加上活跃的雨季光合作用，可能解释了藤本植物在季节性干旱森林中高度丰富的原因。
