庐山不同海拔植物蒸腾水龄动态及用水策略

Dynamic changes of transpiration water age and water utilization strategies for trees at different altitudes in Lushan area

通过探究亚热带湿润气候区庐山不同海拔优势植物的水龄和考虑时间来源的用水策略,为该地区的生态保护和资源利用提供科学依据和支持。以庐山松属(Pinus)(低海拔的马尾松(P.massoniana)、高海拔的黄山松(P.taiwanensis))和栎属(Quercus)(低海拔的栓皮栎(Q.variabilis)、高海拔的短柄枹栎(Q.serrata))共4个树种为研究对象,于2020年7月至2021年8月,利用稳定同位素技术和平均蒸腾水龄模型,分析不同海拔优势植物的蒸腾水龄,并结合水龄结果和MixSIAR来源混合模型,分析植物用水策略和季节性变化;同步监测大气温度、湿度,土壤含水率,根系分布等数据分析蒸腾水龄与植物水分来源的季节性变化。结果显示:(1)庐山地区植物主要利用当季降水,蒸腾水龄为8.67-16.68 d。对于同属植物,高海拔树种蒸腾水龄小于低海拔树种。且在观测期内马尾松的水龄呈“单谷状”,黄山松呈“单峰状”。(2)低海拔树种用水策略在雨季前期主要利用浅层土壤水,随着雨季到来主要吸水层向下移动至深层,并在雨季后期稳定在深层土壤,而高海拔树种在雨季后期主要吸水层稳定在土壤中层。(3)相较之下,考虑时间滞后的低海拔植物用水策略对浅层(0-20 cm)土壤水的依赖减弱,对深层(60-100 cm)土壤水的吸收比例增加,高海拔相反。

Aims To explore the water age of dominant vegetation at different altitudes in Lushan area in the humid climate region and the strategy of water utilization for different aged sources,so as to provide scientific basis for ecological protection and resource utilization in this region.Methods Four species of Pinus(P.massoniana at low altitude,P.taiwanensisat high altitude)and Quercus(Q.variabilisat low altitude,Q.serrataat high altitude)from Lushan Mountain were studied,using stable hydrogen and oxygen isotopes technology and linear mixing water age model in order to analyze the transpiration water age of dominant vegetation at different altitudes from July 2020 to August 2021.After then,water age results and the MixSIAR source mixture model were combined to analyze the strategy of water utilization and seasonal changes.Simultaneously monitored included the air temperature and humidity,soil water content,root distribution and others.In the end,the seasonal changes of the transpiration water age and the water sources was analyzed with all the available data.Important findings(1)Plants in Lushan area mainly use the seasonal precipitation,and the age of transpiration water is between 8.67 and 16.68 d.For the same genus of species,the transpiration water age of high altitude tree species is smaller than that of low altitude.Moreover,during the observation period,the water age of P.massoniana was“single valley-shaped”and P.taiwanensiswas“single peak-shaped”.(2)The low-altitude tree species mainly uses shallow soil water in the early rainy season.With the going-on of rainy season,the main water-absorbing layer moves down to the deep layer,and is stabilized in the deep soil in the late rainy season.However,in the late rainy season,the high-altitude tree species mainly use the water in the middle soil level.(3)In comparison,for the low-altitude trees,their water source is less dependent on shallow(0-20 cm)soil and absorbs more of deep(60-100 cm)soil water.High altitude is on the opposite.