庐山针阔混交林优势种水分利用来源季节变化及对降水的响应

Seasonal variation of water utilization sources and responses to precipitation in the dominant species of broad-leaved and needle-leaved mixed forests in Mount Lushan,China

阐明亚热带湿润山地林区针阔混交林优势种水分来源的季节规律,解析共生植物水文生态位分配与竞争机制,探究植物水分利用对降水的响应,可为指导植被经营管理提供理论参考。本研究以庐山山区马尾松与栓皮栎混交林为对象,基于氢氧稳定同位素技术,分析降水、马尾松和栓皮栎木质部水及0~100 cm土壤水的δ^(2)H和δ^(18)O特征,采用MixSIAR模型、Levins指数和PS指数分别计算各水源的相对贡献率、马尾松与栓皮栎的水文生态位宽度和生态位重叠度。结果表明:丰水期(3—7月)马尾松主要利用0~20和20~40 cm土壤水,栓皮栎主要利用20~40和40~60 cm土壤水,但在枯水期(8—9月)马尾松和栓皮栎分别转而利用40~60和60~80 cm土壤水,根系吸水深度增加。生长季早期(3—4月)和末期(9月)马尾松与栓皮栎水文生态位重叠度高,水分竞争激烈,生长季中期(5—8月)合理分配水源,水文生态位分离以满足高蒸腾需求。栓皮栎在降水事件前主要利用60~80和80~100 cm土壤水,降水后利用0~20和20~40 cm土壤水,但马尾松在降水事件前后均主要利用0~20和20~40 cm土壤水。综上,马尾松与栓皮栎的水分利用来源呈现“雨季浅,旱季深”的季节规律,能在生长旺季合理分配水源,根系吸水积极响应土壤水分动态,对极端降水的适应性强,具有较强的水源涵养能力。

Elucidating the seasonal patterns of water sources for dominant species in the sub-tropical humid mountainous forest,analyzing the eco-hydrological complementarity and competition mechanisms among coexisting species,investigating the responses of plant water utilization to precipitation,could provide a theoretical basis for vegetation restoration and management.Based on the stable hydrogen and oxygen isotope technique,we analyzed the δ^(2)H and δ^(18)O characteristics of precipitation,xylem water from Pinus massoniana and Quercus variabilis,and soil water from O-100 cm depth in Mount Lushan,China.The MixSIAR model,Levins index,and PS index were used to calculate the relative contribution rate of each water source,the hydrological niche breadth,and niche overlap of P.massoniana and Q.variabilis.The results showed that,in the wet season(March to July),P.massoniana primarily utilized soil water from the 0-20 cm and 20-40 cm depths,while Q.variabilis primarily utilized that from the 20-40 cm and 40-60 cm depths.During the dry season(August to September),P.massoniana and Q.variabilis utilized 40-60 cm and 60-80 cm of soil water,respectively,resulting in an increase in the depth of water absorption.In the early growing season(March to April)and the late growing season(September),there was a high hydrological niche overlap between P.massoniana and Q.variabilis,resulting in intensitive water competition.In the middle of the growing season(May to August),the water source was adequately allocated,and the hydrological niche was segregated to meet the high transpiration demand.Q.variabilis primarily utilized soil water from a depth of 60-80 cm and 60-80 cm before a precipitation event,and from a depth of 0-20 cm and 20-40 cm after the event.In contrast,P.massoniana primarily utilized soil water from a depth of 0-20 cm and 20-40 cm both before and after a precipitation event.In conclusion,water utilization patterns of P.massoniana and Q.variabilis exhibited a seasonal trend,with shallow water uptake during the rainy season and deep water uptake during the dry season.These species are capable of efficiently allocating water resources during the peak growth season,and their root systems actively respond to change in soil moisture level.They have strong adaptability to extreme precipitation events and exhibit remarkable water conservation capabilities.