对干季的西双版纳热带季节雨林而言，频繁出现的持久浓雾被认为是一种重要的水分输入，这在热带季节雨林生态系统水分、养分循环中扮演着重要的角色，这不仅表现为：部分植物叶片在干季可直接吸收雾水或通过地表浅根吸收林冠滴落的雾水和养分，更重要的是浓雾极大地抑制了林冠在干季的蒸发蒸腾和消弱了低温强度，从而地缓解了干季水分不足或低温伤害。然而，有关热带季节雨林内植物对雾水的具体利用状况却是未知。
中科院西双版纳热带植物园恢复生态组的刘文杰博士等在国家自然科学基金的资助下，对西双版纳热带季节雨林2种优势林冠树种（绒毛番龙眼Pometia tomentosa、大叶白顔Gironniera subaequalis）在干季的水分获取方式进行了的观测研究。研究结果表明：干季期间，大叶白顔树倾向于优先利用上层50 厘米的土壤水（53–72%）；而绒毛番龙眼树的水分获取则主要来自60厘米以下的深层土壤水（54–72%），其对上层土壤水的利用仅为28–46%，说明绒毛番龙眼主要靠其深层主根获取水分。在干季的代表浓雾天气里，林下绒毛番龙眼幼苗的生长极大地依赖于林冠滴落的雾水（23–59%），表明雾水对于干季的幼苗正常生长具有重要的生态意义。
此研究结果初步阐明了干季热带季节雨林部分植物对水分不足的生态适应对策，即植物为了避免对有限水分的直接竞争，采用了区分利用的有效方式，从而减弱它们之间的直接竞争，增加了物种的多样性。
相关论文发表在Agricultural and Forest Meteorology上。（生物谷Bioon.com）
生物谷推荐原文出处：
Agricultural and Forest Meteorology, doi:10.1016/j.agrformet.2009.12.006
Dry season water uptake by two dominant canopy tree species in a tropical seasonal rainforest of Xishuangbanna, SW China
Wenjie Liu, Wenyao Liu, Pengju Li, Wenping Duan, Hongmei Li
Radiation fog has been suggested as an important source of moisture in tropical seasonal rainforest of Xishuangbanna during 6 months of annual drought, yet its importance for the plants which inhabit this ecosystem is virtually unknown. We assessed patterns of water uptake by two major seasonal rainforest canopy tree species in Xishuangbanna, SW China, during two consecutive dry seasons (2005 and 2006). Stable oxygen isotope compositions of water in xylem, soil, fog, rain, and groundwater were analyzed, and soil water content and leaf water potential were measured concurrently in order to determine the proportion of water deriving from shallow soil by mature trees and from fog water by seedlings during the pronounced dry season. Our results indicated that evergreen Gironniera subaequalis tree appeared to be acquiring water preferentially from the upper 50 cm of the soil profile, with around 53–72% of its water from shallow soil. In contrast, brevi-deciduous Pometia tomentosa tree seemed to be tapping water mostly from depths greater than 60 cm or from groundwater, with about 28–46% of its water from shallow soil, suggesting that it relies predominantly on its deep taproot for water uptake. During the dry season, when fog was most frequent, 23–59% of the water used by P. tomentosa seedling came from fog water after it had dripped from tree foliage into the soil, indicating that fog water was an important source for seedling growth, especially at the peak of the dry season. Since both seedlings and shallow-rooted understory species require moisture and cool conditions to regenerate, it might be expected that some other tree seedlings and understory species also partially rely on fog moisture during the pronounced dry season, but further research is needed.
