亚热带常绿阔叶林的水文生态特征

对日本冲绳岛亚热带天然次生常绿阔叶林的水文生态特性进行了为期3年的定位观测.结果表明,观测期间年平均降雨量高达3325mm,台风降雨(包括直接和间接影响)占年降雨量的42.3%;穿透雨量和树干流量分别为年降雨量的53.9%和30.9%,较高的树干流量可能与高风速、强度降雨以及优势树种的树冠构造紧密相关.林冠截留损失占年降雨量的15.2%,低于世界范围内其它多数常绿阔叶林(15%～30%).年平均地表径流和壤中流量分别是1092mm和613mm,分别占年降雨量的32.8%和18.4%;较高的径流量可能是由不良的土壤物理性质引起的.试验林土壤尤其是下层土壤非毛管孔隙度低(8%～12%)、粘粒含量极高(51.9%～60.5%),水分渗透缓慢(12ml·min^-1).0～70 cm土层的有效蓄水量和最大蓄水量分别为85 mm和324mm,林地凋落物层的最大持水量为2.8 mm,接近或低于中国亚热带和热带山地雨林.

Eco-hydrological characteristics of a subtropical evergreen broadleaved forest in Japan

A three years (1998-2000) observation on the eco-hydrological characteristics of Castanopsis sieboldii and Schima wallichii dominated subtropical evergreen broadleaved forest on the Okinawa Island of Japan showed that during the observation period, the mean annual precipitation was 3325 mm, and 42.3% of it was directly or indirectly contributed by typhoon rainfall, implying that typhoon played a very important role in the hydrology of the forest. Through-fall and stem-flow contributed to 53.9% and 30.9% of the annual rainfall, respectively. The higher stem-flow could be due to the high wind velocity, intense rainfall, and the crown morphology of dominant species C. sieboldii with inclined branches and concave-shaped leaves. Interception loss occupied 15.2% of the total rainfall, being the lowest in the range of 15%-30% widely reported for many broadleaved evergreen forests. The annual surface runoff and lateral flow were 1092 mm and 613 mm, respectively, and the high proportion of surface runoff (32.8%) was probably due to the poor physical properties of soil, particularly the low noncapillary porosity (8%-12%), high clay content (51.9%-60.5%), and low infiltration rate (12 ml x min(-1)) in deeper soil layers. The effective and maximum water storage capacity of 0-70 cm soil layer were 85 mm and 324 mm, respectively, and the maximum water-holding capacity of forest floor was 2. 8 mm, which were close to or lower than those of the subtropical and tropical rain forests in China.