不同林龄段桤柏混交林生态系统的水源涵养功能

Water conversation function of the mixed Alnus cremastogyne and Cupressus funebris stand ecosystem at different stand age

2005年对川中丘陵区的10、15、20和25a的桤（Alnus cremastogyne）柏（Cupressus funebris）混交林和30a纯柏林的水源涵养功能及其变化趋势进行研究。结果表明：1）凋落物的蓄积量、饱和持水量与最大持水量均以20a的最大，30a纯柏林的最低，凋落物的持水量与蓄积量、含水率有显著正相关关系；2）表层土壤密度在10～20a间显著下降，20a的最低（1．20g／crn3），在20～30a间显著增加；非毛管孔隙度和总孔隙度在10～20a间显著增加，25和30a时显著下降；毛管孔隙度在各林龄段间呈波动性变化；土壤最小持水量和毛管持水量在10～15a间显著增加，20～30a间相对稳定，最大持水量在10～20a间显著增加，25和30a的显著降低；3）桤柏混交林的综合水源涵养功能，15a时达到最大值1446．06t／hm^2，30a时显著下降到1331．60t／hm^2，各林龄段桤柏混交林根系土壤层的水源涵养能力占98％以上。认为应对25a后的桤柏混交林及纯柏林进行结构调整，以提高桤柏混交林的水源涵养功能。

The water conservation is one of the important functions of forest ecosystem. The mixed Alnus cremastogyne and Cupressusfunebris stands at 10 a, 15 a, 20 a and 25 a and the 30 a cypress stand in the hilly area of central Sichuan Basin were investigated to study the change tendencies of water conservation function. The results showed that： 1 ） The accumulation mass, saturated water holding capacity and maximum water holding capacity of the litter layer reached the maximum at 20 a, and decreased to the minimum at 30 a. The water holding capacity correlated with the accumulation mass and the water holding rates significantly; 2） The bulk density of the topsoil declined significantly from 10 a to 20 a and reached the minimum 1.20 g/cm^3, but increased significantly from 20 a to 30 a. The non-capillary porosity and total porosity increased from 10 a to 20 a but declined significantly after 20 a. The capillary porosity fluctuated from 10 a to 30 a. The minimum waterholding capacity and capillary water-holding capacity increased significantly from 10 a to 15 a and relatively stabilized from 20 a to 30 a, and the maximum water-holding capacity increased from 10 a to 20 a and decreased at 25 a or 30 a, significantly; 3）The total water-holding capacity of the mixed stands reached the maximum, 1 446.06 t/hm^2 at 15a and then declined to 1 331.60 t/hm^2 at 30 a. The soil water-holding capacity accounted for more than 98 % of the stands total water-holding capacity at different stand age. The results indicated that the structures of the mixed stands older than 25 a and the cypress stand should be adjusted to enhance the water conservation function.