土壤水分和林下植被对白榆蒸腾作用的影响OA

This study explored the effects of soil moisture and understory vegetation on the transpiration of Ulmus pumila in Bashang area of northern Hebei province,and provide a theoretical basis for the sustain-able management of plantation and the effective management of water resources in forest land.A two-fac-tor and two-level completely randomized watering and understory vegetation removal experiment was con-ducted on a monoculture Ulmus pumila plantation in Kangbao County,Zhangjiakou City,Hebei Province.Four treatments were set up:non-removal of understory vegetation-no watering(CK),non-removal of un-derstory vegetation-watering(WJ),removal of understory vegetation-no watering(CW),and removal of understory vegetation-watering(CJ).The Granier thermal diffusion technique was applied to continuously monitor sap flow rate(Js),during which photosynthetically active radiation(PAR),air temperature(Ta),air relative humidity(RH),wind speed(WS),and soil volumetric water content(SWC)were moni-tored to clarify the variation in Js.Relationships with the various environmental factors and Js were ana-lyzed.The research showed that:1)SWC in the study area is under a natural deficit state.Js increased gradually after watering,reaching and maintaining a stable state after 5 days(P＜0.05)under a no wate-ring treatment.Two-factor analysis of variance showed that removal of understory vegetation as well as combined watering and vegetation removal have no significant effect on Js(P＞0.05).2)The diurnal vari-ation of Ulmus pumila Js under different treatments showed a single peak curve of'high in day and low in night',and there was a weak sap flow at night.CJ treatment and CK treatment achieved the largest and smallest Js respectively,ranging between 0.022-0.054 g/(cm2·s)and 0.004-0.020 g/(cm2·s),respec-tively.3)PAR was the dominant environmental factor under watering and non-watering treatments.The rank of the environmental factors in terms of their total effects on Js were:PAR＞Ta＞SWC＞RH＞WS.Watering heightened the effect of meteorological factors on Js.Soil drought may be the main factor limit-ing transpiration of Ulmus pumila in Bashang,northern Hebei province.In the production practice,we can choose to retain the understory vegetation,and ensure the normal water physiological activities of Ulmus pumila plantation by watering measures at the appropriate time.