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Northwest A&F University (2018)

Water Sources and Its Response to Rainfall of Pinus Tabulaeformis and Hippophae Rhamnoides in Loess Hilly Region

卢森堡;

Titre : Water Sources and Its Response to Rainfall of Pinus Tabulaeformis and Hippophae Rhamnoides in Loess Hilly Region

Auteur : 卢森堡;

Grade : Master’s Theses 2018

Université : Northwest A&F University

Résumé partiel
Loess hilly region has low rainfall and large evaporation.Rainfall is the main limiting factor for vegetation restoration in this area.The survival and growth of plants are closely related to the availability of rainfall.Since the relationship between water supply and plant water consumption was not fully considered in the previous afforestation process,with the increase of water consumption in a plantation,the survival rate,the preservation rate and the growth rate of which were generally low,and a large area of small old trees were formed.In order to evaluate the stability of plantation for water use in this area,it is necessary to study the impact of rainfall on soil volumetric water content(SWC),water source of plantation and the response of plantation’s water consumption to environmental factors(especially rainfall)for vegetation restoration.Due to the highly soil and water conservation values,mixed plantation were widely used during grain for green.However,there were less report about whether or not a mixed plantation have changed the plants water strategy.This study was based on Pinus tabulaeformis and Hippophae rhamnoides in a pure and mixed plantation,from June to October 2015&2016,using automatic weather station and thermal dissipation probe(TDP)and soil water system(EMH2O-EM50)to continuously measure the meteorological factors(rainfall,photosynthetically active radiation(PAR)and water vapor pressure deficit(VPD))of sample area,the sap flux density(Fd)of sample tree and the SWC data of woodland,respectively.In addition,ultra-vacuum extraction and isotope mass spectrometry device were used to analyze the ratios of hydrogen and oxygen isotope(δD/δ18O)in rainfall,xylem and soil water.Using the methods of variance analysis,Threshold-Delay(T-D)model,stepwise multiple regression analyses,Isosource model and partial correlation analyses,first we studied the SWC in response to rainfall in different woodland,then we have detected the water resource from two trees usingδD andδ18O,and analyzed the process of Fd of two species response to the rainfall pulses and we also determinedthe effects of environmental factors on Fd.The results were as follows :(1)The SWC in 0-20 cm(SWC0-20)was increased after continuous small rainfall(<5mm),but did not change after individual rainfall,indicated the accumulation of the process.When the rainfall beyond 5 mm,the SWC was attached to pick value and then decreased in all layers.However,another rainfall happened after which usually not increased the SWC,illustrated the relationship between SWC and rainfall amount.Rainfall above 5 mm could caused SWC0-20 in all plantation and SWC20-50 in a pure plantation(Hippophae rhamnoides),rainfall above 10 mm could caused SWC20-50 in a mixed plantation and SWC50-100 in a pure plantation(Hippophae rhamnoides),and rainfall above 15 mm could caused SWC between 20and 150 cm from Pinus tabulaeformis in pure plantation and SWC50-100 and SWC100-150000-1500 in a mixed plantation increased significantly.There was significant correlation between rainfall and SWC in 0-50 cm for Pinus tabulaeformis in a pure plantation,and 20-100 cm for Hippophae rhamnoides in a pure and mixed plantation,but SWC in 0-20 cm was loss to vaporation largely,so that rainfall has good infiltration in 20-50 cm,20-100 cm and 20-100cm in three woodland.The relationship between SWC and rainfall were as follows,mixed plantation with Pinus tabulaeformis and Hippophae rhamnoides>Hippophae rhamnoides in a pure plantation>Pinus tabulaeformis in a pure plantation.

Mots clés : Pinus tabulaeformis; Hippophae rhamnoides; Rainfall; Soil volumetric water content; Sap flux density;

Présentation (CNKI)

Page publiée le 6 octobre 2018