广西不同石漠化等级下SPAC水势梯度及其环境效应

以野外观测为基础,对广西不同石漠化等级(无石漠化、轻度石漠化、中度石漠化和重度石漠化)下土壤-植被-大气连续体(Soil-Plant-Atmosphere Continuum,简称SPAC)系统中的水势日变化、气象因子日变化过程进行了研究。结果表明:随着石漠化程度的增加,大气水势降低,大气水势对不同石漠化程度的反应敏感。岩溶区石漠化等级下植物和土壤水势较低,不同石漠化条件下的植物叶水势在-7.79±0.43~-2.68±0.11 Mpa之间,土壤水势在-4.00±0~-0.08±0.04 Mpa之间,重度石漠化等级下植物处于萎蔫状态。植物在正午受到的水分亏缺程度为:重度石漠化中度石漠化无石漠化轻度石漠化。无石漠化下植物叶片水势与大气温度呈正相关关系,与大气相对湿度呈负相关关系,轻度石漠化、中度石漠化和重度石漠化下植物叶片水势与大气温度呈负相关关系,与大气相对湿度呈正相关关系。水分在SPAC系统中运移,其能量消耗主要集中在叶片-大气的过程。叶-气水势差差值大小为:中度石漠化重度石漠化轻度石漠化无石漠化。随着石漠化程度的增加,SPAC水势梯度提高,各介质层水势差的增大,提高了水分循环和能量交换的强度。

SPAC Water Potential Gradient and Its Environmental Effect in Different Rocky Desertification Grades in Guangxi

Based on field abservations, the diurnal changes of water potential and weather in Soil-Plant-Atmosphere Continuum(SPAC) in different grades of rocky desertification(RD) (Non RD, light RD, moderate RD, intense RD), Guangxi Autonomous Region, have been studied. Some conclusions have been drawn:atmosphere water potential was sensitive to rocky desertification, and the more serious the rocky desertification, the lower the atmosphere water potential. Plant and soil water potentials in the areas of karst rocky desertification were very low, with the plant water potential varying between -7.79 Mpa and -2.68 Mpa, and the soil water potential between -4.00 Mpa and -0.08 Mpa. The degrees at which the plant was under water stress in the noon are given as follows:intense RD > moderate RD > non RD > light RD. In the case of non rocky desertification, the plant water potential was positively correlated with atmospheric temperature, and it was negatively correlated with relative atmospheric humidity. In light, moderate and intense rocky desertification, the plant water potential was negatively correlated with atmospheric temperature, and it was positively correlated with relative atmospheric humidity. The energy for water circulation in the SPAC system was consumed mostly in the process from plant leaf to atmosphere. The variation order of water potential between leaf and atmosphere was:moderate RD > intense RD > light RD > non RD. The SPAC water potential gradient was increasing along with serious rocky desertification, and at the same time, water cycle and energy change were improved.