對干季的西雙版納熱帶季節(jié)雨林而言，頻繁出現(xiàn)的持久濃霧被認為是一種重要的水分輸入,，這在熱帶季節(jié)雨林生態(tài)系統(tǒng)水分,、養(yǎng)分循環(huán)中扮演著重要的角色，這不僅表現(xiàn)為：部分植物葉片在干季可直接吸收霧水或通過地表淺根吸收林冠滴落的霧水和養(yǎng)分,，更重要的是濃霧極大地抑制了林冠在干季的蒸發(fā)蒸騰和消弱了低溫強度,，從而地緩解了干季水分不足或低溫傷害。然而,，有關熱帶季節(jié)雨林內植物對霧水的具體利用狀況卻是未知,。
中科院西雙版納熱帶植物園恢復生態(tài)組的劉文杰博士等在國家自然科學基金的資助下，對西雙版納熱帶季節(jié)雨林2種優(yōu)勢林冠樹種（絨毛番龍眼Pometia tomentosa,、大葉白顔Gironniera subaequalis）在干季的水分獲取方式進行了的觀測研究。研究結果表明：干季期間,，大葉白顔樹傾向于優(yōu)先利用上層50 厘米的土壤水（53–72%）,；而絨毛番龍眼樹的水分獲取則主要來自60厘米以下的深層土壤水（54–72%），其對上層土壤水的利用僅為28–46%,，說明絨毛番龍眼主要靠其深層主根獲取水分,。在干季的代表濃霧天氣里，林下絨毛番龍眼幼苗的生長極大地依賴于林冠滴落的霧水（23–59%）,，表明霧水對于干季的幼苗正常生長具有重要的生態(tài)意義,。
此研究結果初步闡明了干季熱帶季節(jié)雨林部分植物對水分不足的生態(tài)適應對策，即植物為了避免對有限水分的直接競爭，采用了區(qū)分利用的有效方式,，從而減弱它們之間的直接競爭,，增加了物種的多樣性。
相關論文發(fā)表在Agricultural and Forest Meteorology上,。（生物谷Bioon.com）
生物谷推薦原文出處：
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.
