毛竹扩张的生态后效:凋落物水文功能评价

Changes in the hydrological functions of litter layer following Phyllostachys edulis expansion into evergreen broadleaved forest

为评价毛竹扩张对次生常绿阔叶林凋落物水文功能的影响,在江西大岗山收集毛竹林和邻近的次生常绿阔叶林凋落物,采用模拟降雨法和浸泡法,测定了凋落物阻滞径流时间、截留降雨量和持水量(率)等水文功能指标。结果表明:当降雨强度为0.5、1.0、1.5mm·min-1,坡度为10°、25°、40°时,2种森林凋落物阻滞径流的时间均随雨强和坡度增加而提前,但在同等条件下毛竹林产流的时间比常绿阔叶林要迟;2种森林凋落物截留量与降雨历时的关系都可用一级动力学模型Nt=N0(1-e-kt)进行较好的拟合,最大截留量N0随降雨强度增大而增大,随坡度增大而减小,但同一条件下毛竹林凋落物最大截留量N0较常绿阔叶林大;毛竹林凋落物的最大持水率和最大持水量分别为267.51%和7.41 t·hm-2,常绿阔叶林对应的值为244.33%和5.27 t·hm-2,前者比后者分别高出9.49%和40.60%。研究表明,毛竹扩张导致常绿阔叶林转变成毛竹林后,凋落物的水文生态功能增强。

The expansion of Phyllostachys edulis into neighbor secondary evergreen broadleaved forest may affect the hydrological functions of litter layers. Using laboratory simulated rainfall ex- periments and immersion test, we monitored the time of retarding runoff, rainfall interception and water holding capacity of litter between Ph. edulis forest （PEF） and adjacent evergreen broad- leaved forest （EBF）. When the rainfall intensities were 0.5, 1.0, 1.5 mm · min-1 and the slopes were 10°, 25°, 40°, the time of litter retarding runoff decreased with the rainfall intensity and the slope, with the time of retarding runoff for PEF being higher than that for EBF. The relation- ship between interception capacity and rainfall time could be described by N1 =N0（ 1-e-kt） for both stands, and the maximum interception capacity （No） of litter layers increased with the rain- fall intensity but decreased with the slope. Under the same condition, PEF had higher No than EBF. The maximum water holding capacity rate was 267.51% for PEF, being 9.49% higher than that for EBF （244.33%） ; the maximum water holding capacity for PEF （7.41 t· hm-2） was 40.60% higher than that for EBF （5.27 t · hm-2）. These results indicated that the hydrological functions of fitter layer may increase with the expansion of Ph. edulis.