摘要
北方土石山区因年内降水不均,常出现季节性干旱.探究降水对侧柏(Platycladus orientalis)液流特征与水分来源的影响,对构建稳定生态系统具有重要意义.该研究以北京山区侧柏人工林为研究对象,利用热扩散式边材液流探针技术(TDP)和氢氧同位素示踪技术对不同控水处理的侧柏进行观测,同步监测气象、土壤水分含量等环境因子.结果表明:(1)侧柏液流量呈现二倍降水与自然降水＞一半降水＞无降水.(2)降水增加土壤相对有效含水率(REW),进而提高侧柏液流对环境因子的响应程度,侧柏液流主要受饱和水汽压差(VPD)的影响,太阳辐射(Rs)与风速(WS)影响程度较低.(3)侧柏水分来源特征随降水梯度呈规律性变化,随土壤含水量升高,其水分来源逐步向浅层土壤转变.对比降水前后,除无降水区内侧柏水分来源无明显变化外,其他处理区侧柏均在降水后增加了对0-40 cm土壤水的利用比例,当降水后自然降水区与二倍降水区的土壤处于相对含水量较高时期,这种变化更为明显.综上所述,侧柏根据降水和土壤水分的变化调整液流运动和吸水深度,这种自适应特性有利于其度过极端干旱胁迫和生存.
Abstract
Aims Seasonal drought often occurs in the northern rocky mountainous area due to annual variation in precipitation.Exploring the effects of changes in precipitation on the sap flow characteristics and water sources of Platycladus orientalis is of great significance for structuring a stable ecosystem.Methods In this study,the plantation of P.orientalis in the rocky mountainous area of Beijing was taken as the research target.The thermal dissipation probe(TDP)and hydrogen/oxygen isotope tracer technology were used to observe the P.orientalis under different watering treatments.Meteorological,soil moisture,and other environmental factors were simultaneously monitored.Important findings The results showed that natural precipitation and double precipitation＞half precipitation＞no precipitation were the main characteristics of P.orientalis sap flow.Precipitation increased the relative effective water content(REW)of soil,thereby stimulated the response of P.orientalis sap flow to environmental factors.Platycladus orientalis sap flow is mainly affected by the atmospheric vapor pressure deficit(VPD),and the impact of solar radiation(Rs)and wind speed(WS)is relatively low.The water source of P.orientalis changed with precipitation amounts.When the soil water content increased,its water source gradually changed to shallow soil.Compared with precipitation before,P.orientalis have increased the utilization ratio of 0-40 cm soil water after precipitation,except that P.orientalis in no precipitation treatment that exhibited no noticeable change.This change is more pronounced in natural precipitation and double precipitation treatments where a period of high relative water content after precipitation was more evident.To sum up,P.orientalis can adjust sap flow and the depth of water absorption from soil in responses to the changes in precipitation and soil moisture.This self-adaptive characteristic is conducive for trees to survive the extreme drought.
维普
万方数据