栓皮栎林分枯落物对土壤-植物系统水分运动的影响

目的]分析枯落物层对森林生态系统水分循环的作用。方法]利用稳定同位素技术,测定了在旱季和雨季栓皮栎木质部水分以及枯落物层和不同土壤层水分的同位素特征。通过对比不同环境条件下(干旱期和降雨前后)枯落物层和土壤水分同位素组成的变化,并根据其与植物茎水分同位素特征的差异判断栓皮栎不同季节的水分利用来源。结果]在旱季,随着干旱期的进行,对于平均枯落物层厚度,表层0—30cm土壤水分同位素特征由于蒸发分馏的影响逐渐变得富集,而对于因为特殊地形而造成的未分解枯落物层较厚的地方,则土壤水分同位素特征随着干旱期的进行几乎不发生变化;栓皮栎的水分来源主要集中在表层,随着干旱期的延长没有发生变化;在雨季,极端降雨后,土壤同位素特征表明枯落物截留降雨的效应明显,被枯落物截留的雨水以活塞流的形式继续向土壤入渗,栓皮栎的水分来源主要来自于表层0—10cm枯落物层(分解层)的土壤;土壤剖面水分同位素特征呈现的梯度变化与土壤层的结构有关。结论]枯落物层的厚度,特别是未分解层,对土壤水分的同位素特征影响有差异;枯落物层的水文效应也间接改变了植物的水分利用。

Effects of Litters in Cork Oak Stands on Water Movement of Soil-Plant System

Objective] To analyze the effects of litter layer on forest ecosystem moisture cycle. Methods] Using stable isotope techniques to measure the moisture in Quercus xylem in dry and wet seasons, and the isotopic characteristics of the litter layer and different soil moisture layers. By contrasting the changes of the composition of litter layer and soil moisture isotopes under different environmental conditions which including before and after periods of drought and rainfall, and based on the differences between the changes and the isotopic characteristics of plant stem moisture, the differences in different seasons of cork oak were estimated. Results] Firstly, as the drought continues, due to evaporation fractionation gradually, the isotopic characteristics of moisture in surface soil of 0-30 cm become enriched for the average thickness of the litter layer, and the isotopic characteristics of soil moisture almost did not change for the thick undecomposed litter layer caused by special topography. The moisture source of cork oak concentrated mainly in the surface water, and did not change with the drought. Secondly, after extreme rainfall during the rainy season, soil isotopic characteristics indicated litter interception rainfall effect was obvious, the rainwater which was trapped by litter infiltrated to soil in the form of plug flow continuously, the main source of moisture of Quercus come from the surface 0-10 cm layer of soil litter decomposition layer. Thirdly, moisture gradient isotopic characteristics of the soil profile was related to the structure of the soil layer. Conclusion] There are differences in the effects of litter layers' thickness on soil moisture isotopic characteristics, especially which of undecomposed layer. The hydrological effects of litter in cork oak stands change the plant water use indirectly.