元江稀树灌丛降雨再分配及其与气象因子的关系

中国西南干热河谷地区广泛分布有稀树灌丛植被,气候条件干热,水热矛盾异常明显,然而对其降雨再分配缺乏研究。本研究选择了元江干热河谷稀树灌丛进行了1a的监测,开展降雨再分配及其影响因素分析。结果表明,观测期间总降雨量为762.9mm,穿透雨量、树干径流量和林冠截留量分别为639.3、14.6mm和109.0mm,分别占总降雨量的83.8%、1.9%和14.3%,当降雨量>1.1mm时开始产生穿透雨;降雨量>1.4mm时,开始产生树干径流。降雨再分配各分量与降雨量、降雨强度和气温均具有显著的相关关系(P<0.01),其中降雨量是与降雨再分配关系最密切的气象因子,即随着降雨量的增加,穿透雨量、树干径流量均增大,穿透雨率、树干径流率先增加后趋于稳定,而林冠截留率先减小后趋于稳定。该地区植被分布稀疏、群落结构简单、群落层次少、郁闭度低等原因造成稀树灌丛的穿透雨率相对较高,林冠截留率较低。

Rainfall Redistribution and Its Relationship with Meteorological Factors in Yuanjiang Valley-type Savanna,Southwest China

Savanna distributes widely in the dry-hot valleys of southwest China with hot and dry climate conditions,and the seasonal drought is very obvious.However,the research about the rainfall redistribution and its influencing factors are particularly insufficient.In this study,1-year monitoring was carried out in savanna of Yuanjiang dry-hot valley to analyze the rainfall redistribution and its influencing factors.The results showed that the total annual precipitation was 762.9 mm,and the throughfall,stemflow and canopy interception were 639.3,14.6 and 109.0 mm,respectively,accounted for 83.8%,1.9% and 14.3% of total precipitation.The threshold rainfalls for forming throughfall and stemflow were 1.1 and 1.4 mm,respectively.The components of rainfall redistribution were significantly correlated with rainfall quantity,rainfall intensity and air temperature ( P <0.01).Meanwhile,rainfall was the most significant meteorological factor for the rainfall redistribution,which was in accordance with the previous results from other vegetation types.With the increase of rainfall,the amount of throughfall and stemflow increased.The ratios of throughfall and stemflow increased first and then stabilized,whereas,the ratio of canopy interception decreased first and then stabilized as the rainfall increased.The Chinese savanna has a sparse vegetation,simple community structure and low canopy density,which results higher throughfall ratio and lower canopy interception ratio.