鼎湖山季风常绿阔叶林枯落物层自然含水量的长期动态变化

Long-term Dynamics of Humus Layer Moisture in Monsoon Evergreen Broad-leaved Forest in Dinghushan

[目的]枯落物层自然含水量是林地环境特征的重要方面,探究枯落物层自然含水量长期动态及其影响机制对认知森林生态系统的水源涵养功能及森林立地环境变化具有重要意义。[方法]本文以鼎湖山国家级保护区内严格保护下的季风常绿阔叶林为研究对象,按照中国生态系统研究网络台站标准化的观测规范,对森林枯落物层自然含水量长期观测(2005—2018年),探究该地带性顶极森林枯落物层自然含水量的长期动态及其环境影响机制。[结果]鼎湖山地区多年平均降雨量1 975.6 mm,年均蒸发量1 117.3 mm,降雨丰富,热量输入稳定,雨热同期特征显著。地带性顶极森林群落季风常绿阔叶林的枯落物层现存量的多年均值为126.0g·m^(-2),干季期间现存量(130.3 g·m^(-2))略高于湿季(121.6 g·m^(-2));枯落物层自然含水量的多年均值为89.5%,湿季(103.2%)显著高于干季(75.8%),且湿季期间枯落物层含水量的变异系数(19.6%)显著低于干季(35.9%)。此外,相较于同期表层土壤(0~15 cm)的变化,枯落物层自然含水量的变异系数(30.1%)显著高于土壤水分的相应变异(11.6%),表明枯落物层对外界环境变化更具敏感性。进一步分析表明,降雨量、空气相对湿度、蒸发量、饱和水汽压差和土壤水分条件均显著影响着枯落物层自然含水量的变化,尤其是湿季期间空气相对湿度以及干季期间空气相对湿度和降雨量对枯落物层自然含水量变化表现出主导作用。[结论]鼎湖山季风常绿阔叶林的枯落物层自然含水量整体处于较高水平,枯落物层具有重要的稳定森林生态系统内部环境以及指示森林立地环境变化等的水文生态功能。

[Objective]The humus layer moisture is one of the environmental characteristics of a forest. It is significant to explore the long-term dynamics of the humus layer moisture and the underlying regulatory mechanisms for understanding the water conservation function of a forest ecosystem and the changes of the forest environment. [Method]In this study, we focused on the zonal climax forest in lower subtropical China, i.e., the monsoon evergreen broad-leaved forest which was strictly protected in Dinghushan National Nature Reserve. Based on the unified standards for the construction and monitoring of forest plots by Chinese Ecosystem Research Network, long-term observation of humus layer moisture in the monsoon evergreen broad-leaved forest was conducted from 2005 to 2018. This study aims at exploring the longterm dynamic of humus layers moisture and its regulatory mechanisms. [Result]During 2005 to 2018, the average annual precipitation of Dinghushan was 1 975.6 mm, the average annual temperature was 22.3℃, the rainfall was abundant and the heat input was stable throughout the year, presenting warm wet summers and cool dry winters. The average standing mass of humus layer was 126.0 g·m^(-2), which was slightly higher in the dry seasons(130.3 g·m^(-2)) than in the wet seasons(121.6 g·m^(-2)). The average annual humus layer moisture was 89.5%. The mean humus layer moisture in wet seasons(103.2%) was obviously higher than that in dry seasons(75.8%), and the variation coefficient in the wet seasons(19.6%) was significantly lower than that in the dry seasons(35.9%). Compared with the change of soil water storage(0-15cm) in the same period, the variation coefficient of humus layer moisture(30.1%) was significantly higher than that of the soil water storage(11.6%), indicating that humus layer was more sensitive to the change of external environment. Further analysis showed that the precipitation, air relative humidity, evaporation, vapor pressure deficit and soil water storage had profound effects on the dynamic of humus layer moisture,especially the air relative humidity in the wet seasons and the air relative humidity and precipitation in the dry seasons had the dominant effects, respectively. [Conclusion]The humus layer moisture in monsoon evergreen broad-leaved forest in Dinghushan is relatively high. It plays an important role in stabilizing the internal environment of forest ecosystem and indicating the change of regional environment.