Transpiration Water Consumption And Its Influencing Factors Of Main Afforestation Tree Species In The Loess Plateau Based On Literature Integration

After the Loess Plateau returned farmland to forest(grass),vegetation restoration and reconstruction have significantly reduced regional soil erosion,but it has also inevitably increased the transpiration water consumption of vegetation.The carrying capacity of soil moisture and vegetation is facing serious challenges,which has triggered regional water resources problems.shortages etc.In order to rationally adjust the vegetation pattern of forest and grass,control soil erosion and soil water vegetation carrying capacity,and reveal the water balance mechanism of forest and grass vegetation after returning farmland to forest(grass),this study analyzed the trunk sap of the main afforestation tree species in the Loess Plateau based on the method of literature integration.Flux change and transpiration water consumption of the flow,Using structural equation modeling to analyze the impact of stand structure and environmental factors on transpiration water consumption,the maximum entropy model determined the probability of vegetation transpiration water consumption under different environmental factors,and provided a basis for vegetation restoration.Under this background,the Loess Plateau provides theoretical and technical support for the high-quality development of soil moisture and vegetation carrying capacity and soil and water conservation.The main conclusions are as follows:(1)The annual average water consumption of Robinia pseudoacacia forest was the highest at 70.14 mm,that of Quercus mongolica var.liaotungensis forest was 54.05 mm,that of pinus tabuliformis carr.forest was 44.38 mm,and that of Platycladus orientalis and Populus Davidian they were 40.10 mm and 44.47 mm,respectively;the annual average monthly transpiration water consumption of Robinia pseudoacacia,Quercus mongolica var.liaotungensis,Pinus tabuliformis carr.,Platycladus orientali and Populus Davidian were 11.95 mm,10.87 mm,10.54 mm,9.76 mm and 10.46 mm respectively.(2)The trunk sap flow curve in the peak period of the growing season shows the characteristics of "broad-peak" or "single-peak";sunny days show "single-peak curves",cloudy days show irregular "multi-peak curves",cloudy days show "Narrow peak curve" or "multi-peak curve",the peak size is sunny > cloudy > cloudy;The difference in trunk sap flux density of different afforestation tree species has nothing to do with trunk diameter class,but is the result of the combined effect of multiple factors.(3)The daily liquid flow density was significantly positively correlated with solar radiation,water vapor pressure deficit and air temperature(p<0.01),and significantly negatively correlated with relative humidity(p<0.01);Climatic factors(solar radiation,atmospheric temperature)and stand factors(stand density)play a decisive role in stand transpiration water consumption,and altitude and soil water content play an important role in stand transpiration water consumption.(4)The average multi-year transpiration water consumption in the Loess Plateau from 2000 to 2020 was 52 mm,which has obvious regional characteristics of gradually decreasing from southeast to northwest.The area of extremely significant increase in transpiration water consumption accounted for 67.6 %,and the trend slope growth rate K>4 The area of mm/a is mainly distributed in the south of Yan’an,Longdong,South Jinzhong and Guanzhong;the annual water consumption change rate is 2.45 mm/a,and the annual change shows a single-peak curve.The order of the actual seasonal transpiration water consumption is summer>spring>autumn>winter.(5)On the Loess Plateau,where the rainfall is 450-550 mm,the temperature is≥8.5°C,the slope is 15-23°,the altitude is 900-1200 m,and the slope is distributed on sunny and semi-sunny slopes,the probability of water consumption by vegetation transpiration is relatively high.