Study On The Development Of Main Tree Species And Water Consumption In Datong Artificial Forest In Qinghai Province

The study of artificial community development and water consumption in loess hill-gully area in the east of qinghai-tibet plateau is complicated and cannot be observed directly,which hindering the further study of its characteristics and functions.The plantation in this area has the characteristics of complex site structure,poor soil and single tree species.The typical afforestation species include Picea crassifolia,Larix principis-rupprechtii,Populus cathayana,Betula platyphylla and Sabina przewalskii.Datong county,located in the loess hilly region of the eastern Qinghai-tibet plateau,is a typical area where soil and water loss occurs.After nearly20 years of implementation of ecological projects such as returning farmland to forests and closing mountains and banning grazing,the vegetation coverage and ecological environment in this area have been significantly improved,but the ecological system is still fragile.Aiming at the development of major tree species,as well as the coordination and sustainability of vegetation and soil water in loess hilly area of the eastern Qinghai-tibet plateau,this study takes the major afforestation species of Picea crassifolia,Larix principis rupprechtii,Populus cathayana and Sabina przewalskii as research objects.Using CNC503DR neutron probe and SFM1plant stem SAP flow meter and other advanced test instruments,using statistical methods and the analysis of a variety of processing software at the same time,the analysis of forest age,the slope under the condition of different forest stand and stable relations,studies the main afforestation tree species in different growth period,reasonable use of soil moisture in forest stand structure and distribution.On the one hand,it is helpful to the determination of ecological water consumption in vegetation construction.On the other hand,the results will directly guide the improvement and renewal of artificial forests in this area in the future,and help to promote the scientific and technological level of the development and construction of artificial forests in the loess hilly region of China.The main conclusions of this study are as follows:(1)84 species of higher plants,divided into 30 families and 71 genera,were found under 4 major tree species in Datong county.There were 20 species of compositae,10species of legume and 7 species of gramineae.Therefore,gramineae,compositae and leguminosae are the dominant families in this area.To vegetation diversity and community productivity evaluation local four main afforestation tree species,the forestation in the early 30 years:Larix principis-rupprechtii(21.68 kg/m~2)of maximizing the aboveground biomass and Populus cathayana(12.96 kg/m~2)of maximizing the aboveground biomass of local ecological community construction and the improvement effect is most obvious,community productivity is relatively high.(2)through the comparison of soil physical and chemical factors and vegetation diversity index,it was found that there were significant differences between soil physical and chemical factors and community vegetation diversity index.However,there was no significant difference between soil physicochemical index and diversity index,indicating that the surface vegetation was still undergoing intense succession and it would take a long time for vegetation to change soil physicochemical properties.(3)the actual daily stem flow of Larix principis-rupprechtii and Populus cathayana plantation samples was measured by the SFM1 SAP stem flowmeter,and then the following conclusions were drawn:In general,Larix principis-rupprechtii consumes more water than Populus cathayana,and the most water consumption is the Larix principis-rupprechtii medium-slope sample planted in 2002(trees consume269.991kg).(4)By measuring soil moisture with CNC503DR neutron instrument,the deficit value of soil moisture from mid-may to early September 2018 was obtained.It was found that the soil moisture of the four main tree species fluctuated with the depth and time in the growing season,but there was no serious loss of soil moisture.Although the middle slope loss of Larix principis-rupprechtii in 1998 was the most serious(loss value was 0.094mg/cm~3),the local winter and spring rainfall(total0.1292mg/cm~3)could completely make up for the loss of plant growth season and realize the healthy development of soil moisture.