西双版纳典型林型凋落物及其水文特征

Litter and its hydrological characteristics of typical forest types in Xishuangbanna

凋落物是森林生态系统发挥水文功能的重要作用层。本研究以西双版纳地区热带季节雨林、单层橡胶林、橡胶/可可和橡胶/大叶千斤拔农林复合系统4种典型林型为对象,收集它们的地表凋落物并用室内浸泡法探究其水文特征,旨在为热带地区土地利用变化下的水资源管理提供参考。结果表明:热带季节雨林总凋落物储量显著大于其余林型(P<0.05),而单层橡胶林和农林复合系统间差异不显著(P>0.05);各个林型凋落物中,储量最大的组分为叶,占比均大于60%;除热带季节雨林外,其他林型凋落物组分最大、最小蓄水率均表现为叶>混合体>枝条+树皮>繁殖体;热带季节雨林各个组分的最大、最小蓄水率显著高于单层橡胶林(P<0.05);各林型不同凋落物组分持水量随时间的变化特点相似,在开始阶段持水量迅速增大,之后持水量增加缓慢,浸泡20 h左右基本达到饱和;在各个时刻,热带季节雨林和橡胶/大叶千斤拔的凋落物持水量比橡胶/可可和单层橡胶林大;单层橡胶林有效拦蓄量最低,为4.69 t·hm^(-2),热带季节雨林为其1.7倍,橡胶/大叶千斤拔为其2.1倍;说明从热带季节雨林转变为单层橡胶林,凋落物的水文功能退化明显;构建诸如橡胶/大叶千斤拔、橡胶/可可等凋落物持水、拦蓄能力较好的农林复合系统能带来生态环境效益。

Litter layer plays a vital role in the hydrological function of forest ecosystems.We conducted a litter soaking experiment in the laboratory to examine litter hydrological characteristics.Litter was collected from four typical forests in Xishuangbanna,including tropical seasonal rainforest,rubber(Hevea brasiliensis)monoculture,and two rubber agroforestry systems(rubberFlemingia macrophylla and rubber-Theobroma cacao).The aim of this study was to provide scientific reference for water resources management under different land use types in tropical area.Our results showed that the total standing litter in the tropical seasonal rainforest was significantly higher than that in other forests(P<0.05),with no difference between rubber monoculture and rubber agroforestry systems(P>0.05).Leaf litter was the largest litter component(accounting for more than 60%of the total)in all forest types.Except for tropical seasonal rainforest,the maximum and minimum water storage rates of litter components in different forest types were leaf>mixed litter>branch+bark>reproductive part.The maximum and minimum water storage rates of each component in tropical seasonal rainforest were significantly higher than that of rubber monoculture(P<0.05).The time-dependent changes in water-holding capacity of litter components were consistent across all the forest types.The water-holding capacity increased rapidly at the beginning stage,then increased slowly,and reached saturation after soaking for about 20 h.At each measurement incidence,water-holding capacity of litters from tropical seasonal rainforest and rubber-F.macrophylla agroforestry system was higher than that from rubber-T.cacao agroforestry system and rubber monoculture.The rubber monoculture had the lowest water interception through litter(4.69 t·hm^(-2)),of which 1.7 times in the tropical rainforest and 2.1 times in rubber-F.macrophylla agroforestry system.These results indicated that the transformation of a tropical seasonal rainforest to rubber monoculture reduced litter hydrological function.The construction of an agroforestry system with a better litter water interception and holding capacity such as rubber-F.macrophylla and rubber-T.cacao would have ecological and environmental benefits.