嘉陵江上游低山暴雨区3种林分凋落物量及其N、P归还

通过对广元低山暴雨区湿地松（Pinus eliottii Engelm）纯林、刺槐（Robinia pseudoacacia）纯林、湿地松与刺槐混交林（mixed stands of Pinus eliottii and Robinia pseudoacacia）3种人工林凋落物量与养分归还的研究表明，3种林分的年凋落量范围在3609．6kg·hm^-2·a^-1到4917．6kg·hm^-2·a^-1，除刺槐林外，湿地松林和混交林均以叶的凋落量占优势，分刺占各自总凋落量的87．45％、55％。湿地松纯林凋落量1a中出现3次峰值（5月、7月、11月或12月）。刺槐纯林出现两次峰值（7月、11月或12月），混交林与刺槐纯林相似。3种林分N、P的年归还量均以刺槐林最大，湿地松纯林最小，这与凋落物总量的大小排序相反。通过凋落物各组分的养分归还中，落叶的归还量占主体。3种林分相比，湿地松林和混交林的凋落总量明显高于刺槐林，但养分归还量却有所不同，刺槐林和混交林明显高于湿地松林，这说明阔叶林有良好维持地力的能力，针阔混交比针叶纯林更能改善土壤肥力。

Litter Production and Nutrient Return in Three Kinds of Plantations in the Upper Reaches of the Jialing River

Litter production and nutrient return studies in three plantations of Pinus eliottii Engelm, Robinia pseudoacacia, mixed stand of Pinus eliottii and Robinia pseudoacacia in the low hills rainstorm disrict of Guangyuan City have shown that the annual amount of litter of the three plantations ranges from 3 609.6 kg ·hm^-2·a^-1to 4 917.6 kg·hm^-2·a^-1 ,and in addition to Robinia pseudoacacia stand,the leaf litter production of the Robinia pseudoacacia stand and Pinus eliottii and Robinia pseudoacacia stand is the most, with respective 87. 45% and 55% shares of their total volume. The litter production of the Pinus eliottii stand displays three peak values, and the Robinia pseudoacacia stand and the mixed stand of Pinus eliottii and Robinia pseudoacacia have two peak values in a year. Annual return production of N and P of the Robinia pseudoacacia stand is the largest, and that of the Pinus eliottii stand is the least . The nutrient return of leaves is the most in each component. Comparison is made among three kinds of forest, which exhibits that the total amount of litter in Pinus eliottii stand and mixed stand of pinus eliottii and Robinia pseudoacacia is obviously larger than that in Robinia pseudoacacia stand, but their nutrient return amounts are different. Robinia pseudoacacia plantation and mixed stand of Pinus eliottii and Robinia pseudoacacia are significantly higher than that of Pinus eliottii stand, thus indicating that broad-leaved forest has a good the ability of maintaining soil fertility, and needle-leaved and bread-leaved mixed forests have a bigger ability to improve soil fertility.