川西亚高山林区不同土地利用与土地覆盖的地被物及土壤持水特征

川西亚高山森林是我国西南亚高山水源涵养林的重要组成部分.随着20世纪中叶以来农业人口的增加和森林的开发利用,受干扰强度、频度和干扰时间的影响,原始暗针叶林退化为耕地、草地、灌丛、次生阔叶林或人工林.1998年后,该区相继启动天然林保护工程和退耕还林工程.为评价工程效益,确定长江上游水源涵养林的恢复与重建模式,需要进行不同土地利用类型之间生态水文效应的对比分析.通过野外调查与室内实验,对比分析了川西亚高山林区农田、草地、退耕还林地、灌丛、次生桦木林、人工云杉林和老龄针叶林的地被物(苔藓与枯落物)和土壤持水特征,结果表明:不同土地利用与覆盖类型间地被物和土壤持水性能差异显著.随着干扰程度的增加,苔藓、枯落物蓄积量及最大持水量下降,土壤容重增加,土壤持水性能下降.苔藓最大持水量排序是老龄针叶林>人工云杉林>天然次生林>灌丛.枯落物最大持水量排序是老龄针叶林>天然次生林>人工云杉林>灌丛>草地>退耕还林地.人工云杉林与天然次生林之间、草地与退耕还林地之间苔藓和枯落物最大持水量没有显著差异.土壤0～40cm最大持水量排序是天然次生林>老龄针叶林>人工云杉林>灌丛>农田>草地>退耕还林地,其中天然次生林显著高于人工云杉林,草地与退耕还林地之间没有显著差异.对于森林恢复途径和树种的选择,需要考虑未来林分的多种生态系统服务功能.

Water holding capacity of ground covers and soils in different land uses and land covers in subalpine region of Western Sichuan, China

Subalpine forests in Western Sichuan are an important part of water conservation forests in Southwestern China. Since the middle of the 20th century, old-growth coniferous forests have been transferred or degraded into croplands, grasslands, shrublands, natural secondary broad-leaved forests and plantations depending on disturbance intensity, frequency and duration for the increase of agriculture and timber supply. In 1998, Natural Forest Protection Program (NFPP) and Slope Land Conversion Program (SLCP) were initiated to restore forest ecosystems. In order to assess the effectiveness of those restoration programs, the eco-hydrological effects of those land uses must be compared. Through field investigation and laboratory experiments, water holding capacity of ground covers and soils were compared among croplands (CL), grasslands (GL), afforestation lands (AL), shrublands (SL), natural secondary forests (SN), plantations (PL) and old growth forests (OG) in subalpine region of Western Sichuan. The results showed that there were significant difference in water holding capacity of ground covers and soils among different land uses and land cover types. With the increase of disturbance intensity, the cumulative mass and the maximum water holding capacity (MWHC) of moss and litters decreased, soil bulk density increased, and soil water holding capacity decreased. The MWHC of moss in descending order was OG, PL, NS, and SL. The MWHC of litters in descending order was OG, NS, PL, SL, GL, and AL. There was no difference in MWHC of moss and litters between PL and NS, and between GL and AL. MWHC at the soil layer of 0-40 cm in descending order were NS, OG, PL, SL, FL, GL, and AL. Although MWHC at the soil layer of 0-40 cm was significantly higher in NS than that in PL, there were no difference between GL and AL. Various forest ecosystem services should be considered when selecting tree species for implementation of SLCP.