亚热带典型植物水分利用来源变化的水稳定同位素分析

旨在揭示亚热带湿润地区不同植物水分利用来源和了解区域森林系统水文循环过程,以长沙地区典型常绿植物樟树、刺杉和野茶花为研究对象,利用稳定同位素技术及Iso-source混合模型定量分析不同植物水分利用特征及其对降水的响应。结果表明:在2018年9月至2019年2月的观测期内,0-10 cm土壤水中δD与降水中δD的变化趋势基本一致,均随时间变化逐渐偏正。随深度的增加,土壤水中δD受降水影响的程度逐渐减小并趋于稳定。在9-11月,3种植物对降水响应程度低,植物茎杆水中δD并未随降水中δD表现出明显偏正的趋势,在12月至翌年2月,3种植物对降水响应明显,植物茎杆水中δD与降水中δD变化趋势一致。观测期内3种植物水分利用深度均随时间变化由深变浅。在9月,3种植物主要利用60-100 cm土壤水,利用比例均超过65%。在10-11月,3种植物水分利用状况存在显著差异,樟树对0-10,10-20,20-60,60-100 cm 4个土层的水分利用较均匀,利用比例分别为28.2%,23.5%,22.0%,26.3%;刺杉主要利用0-10,60-100 cm土壤水,利用比例分别为56.4%和22.2%;林外野茶花主要利用0-20 cm浅层土壤水,利用比例为67.4%。在12月至翌年2月,3种植物主要利用0-10 cm土壤水,利用比例均在70%以上。

Variation in Water Uptake Sources of Typical Plants in Subtropical Area Based on Stable Isotope Measurements

To reveal the water-uptake patterns of different plant species in subtropical humid area and to understand the hydrological cycle of regional forest system, the typical evergreen plant species Cinnamomum camphora, Cunninghamia lanceolate, and Camellia pitardii in Changsha were used as research objects by using stable isotope techniques and Iso-source Mixed Model for quantitative analysis of the water-uptake patterns of different plant species and their responses to precipitation. The results showed that the variations of δD in water from 0-10 cm soil layer and the δD in precipitation are basically identical, and the two kind of δD become more positive with time gradually during the observation period from September 2018 to February 2019. With the increase in depth, the influence of precipitation on δD in soil water gradually reduced and tended to be stable. During September to November, the reflection to precipitation of the three plant species became smaller. The δD in the plant stem water did not show more positive in line with the δD in precipitation. From December to the next February, the three plant species responded sensitively to precipitation. The variation of δD in plant stem water was consistent with the change of δD in precipitation. During the observation period, the water use depth of these plants changed from deep to shallow with time. In September, these plants mostly used 60-100 cm soil water, and the proportion exceeded 65%. During October to November, there were obvious differences in the water-uptake patterns of these plants. The water use of C. camphora from the four soil layers for 0-10, 10-20, 20-60 and 60-100 cm was relatively uniform, and the proportion was 28.2%, 23.5%, 22.0%, and 26.3% respectively;C. lanceolate primarily used 0-10 and 60-100 cm soil water, and the proportion was 56.4% and 22.2% respectively;C. pitardii principally absorbed 0-20 cm shallow soil water, the proportion was 67.4%. From December to February of the next year, these plants generally used 0-10 cm soil water, and the proportion was above 70%.