黄土区人工林的土壤持水力与有效水状况

SOIL WATER HOLDING CAPACITY AND SOIL AVAILABLE WATER IN PLANTATIONS IN THE LOESS REGION

以晋西北黄土区河北杨林、小叶杨林和柠条灌木林为对象，就各人工林地的土壤持水力和在４个不同降水年的土壤有效水动态特点进行了研究。结果表明，林地间土壤持水力和比水容量为：河北杨林＞小叶杨林＞柠条灌木林。各林地的土壤持水力和供水力普遍偏低。林地土壤有效水动态同降水量及其季节分配密切相关，同时受连年干旱递减效应的制约。因此各林地土壤有效水含量为：特涝年（１９９５）＞偏涝年（１９９２）＞特旱年（１９９３）＞偏旱年（１９９４）。在特涝年和偏涝年，生长季前期林地土壤有效水含量很少。在特旱年和偏旱年，几乎整个年生长季中的林地土壤有效水含量都很少。本区人工林生产力普遍偏低，不利的土壤持水和供水条件是其重要限制因素之一。

Based on the fixed field monitoring data of soil water content during the growing season in three different plantations ( Populus hopeiensis,Populus simonii, and Caragana korshinskii) ,by means of soil water characteristic curves the authors studied the soil water holding ability, the specific water capacity as well as soil available water of three plantations at different period of growing season in different precipitation year.The results were as follows: \ \ Of the P.hopeiensis,P.simonii, and C.korshinskii plantations the soil water holding capacity was relatively lower.Among them the soil water holding capacity and the specific water capacity had the following order: P.hopeiensis plantation.> P.simonii plantation> C.korshinskii plantation.Although the dynamics of SAW(soil available water)in a certain year was determined mainly by the amount and seasonal distribution of rainfall it was also influenced by the successive years of drought.Therefore when the precipitation during the growing season was 494 3mm(1992),234 8mm(1993),338 5mm(1994) and 651 6mm(1995),respectively,the SAW content had following order:1995>1992>1993>1994.There was little of SAW content during the early period of the growing season in 1992 and 1995, and it was even quite low during the whole growing season in 1993 and 1994.