| The soil drying phenomenon of artificial forest land in Loess Plateau is serious.Once the dry layer of soil is formed,it is difficult to recover in a short time.This will adversely affect the growth of plants and the selection of subsequent reforestation forest species.Therefore,it is very important to study the soil moisture restoration and the planting and growth of the vegetation on the dry soil.In order to explore the soil moisture recovery characteristics of the deep dry soil in the loess hilly region under different ground cover and the growth of plants planted on the dry soil,a large simulated dry soil column was constructed in the Mizhi hills and hills of northern Shaanxi Province.The surface was covered with film,stone,branch,bare land,date tree,locust,alfalfa,lime and Kentucky bluegrass respectively.The effects of different mulching measures on soil moisture,water storage,water infiltration depth,rainfall storage efficiency and other indexes were analyzed by using location monitoring to obtain soil moisture in 10 meters soil layer of soil column in the experimental area.In order to provide theoretical basis for the construction of subsequent vegetation in dry soil and to provide reference for soil water management in dry environment,the growth status of plants was measured regularly,and the water consumption status of plants was analyzed in order to provide the theoretical basis for the construction of subsequent vegetation in dry soil.The analysis results of soil moisture location monitoring data from 2014 to 2017 are as follows.(1)Under the influence of rainfall,the evaporation of bare soil was equal to that of the same period in January-May,the soil moisture content remained unchanged,and the depth of water infiltration did not change.The evaporation in June-November was less than that in the same period.The accumulation of soil water resulted in the increase of soil water content and the increase of soil water infiltration depth.The soil moisture of sloping farmland with loose surface fluctuated in the range of 0 ~ 200 cm,and the soil moisture below 200 cm did not change.The average moisture content of sloping farmland was 15.26%,the water storage was 1526 mm,the soil water deficit was slight in the depth of 0 ~ 100 cm,900-1000 cm,and there was no soil water deficit in the range of 100 ~ 900 cm.(2)At the end of the experiment period,the soil moisture content of bare soil was 19.6%,16.0%,14.1% and 12.5%,respectively,with film mulching,stone mulching and branch mulching.The restoration depths are: 1000 cm,1000 cm,700 cm,480 cm,film mulching,stone mulching and branch mulching,respectively.The soil water storage increases by 1211.4 mm,853.4 mm,662.5 mm,523.2 mm.In the depth range of 0-1 000 cm in bare soil.The annual rainfall storage efficiency of 4 mm,662.5 mm,523.2 mm,was 63.4%,42.4%,29.4%,23.0%,respectively.(3)By the end of 2017,soil moisture of POA pratensis,alfalfa,Caragana,jujube and Robinia pseudoacacia were 9.1%,6.3%,6.9%,7.8%,5.3%,respectively.The jujube trees increased by 1.3% and 0.2%,respectively.The soil water consumption of Alfalfa,Caragana and Robinia pseudoacacia decreased by 1.3%,0.8%,2.4% respectively.The order of soil water consumption was POA pratensis,jujube tree,Caragana,Alfalfa and Robinia pseudoacacia.(4)By the end of 2017,the height of POA pratensis was 42.3 cm,Alfalfa height was 63.7 cm,ground diameter was 3.3 mm,Caragana height was 114.3 cm,ground diameter was 10.2 mm,height was 146 cm,ground diameter was 73.8 cm × 88.2 cm,Robinia pseudoacacia height was 480 cm,Ground diameter was 189.3 cm × 197.4 cm.The average annual evapotranspiration of water storage was 135.9 mm,-131.8 mm,-61.8 mm,17.8 mm,-235.6 mm;and the annual evapotranspiration was 523.1 mm,611.1 mm,588.0mm,586.4 mm,666.5 mm.(5)The soil water consumption period of the five species is from May to July of each year,from July to September,and from September to November,the period of surface soil moisture recovery is from May to July,and from July to September.Therefore,a great deal of soil moisture conservation should be carried out from May to July of the year.At the end of 2017,the increase of soil water content in 0-280 cm range of jujube tree was greater than that of initial water content,and the soil water content of premature gramine 0-420 cm increased.The depth of water consumption of Caragana is 540 cm,and the average depth of water consumption is 180 cm.After 3 years of development,the depth of water consumption of Caragana will reach 1000 cm.The depth of water consumption of alfalfa reaches 1000 cm.The soil moisture content of Robinia pseudoacacia in 2017 was almost the same as that in 2016,and the average water content of 0-1000 cm was 5.3%,indicating that soil storage water was no longer available.Only the current year's rainfall was consumed within the depth of 0-1000 cm;the water consumption depth of jujube trees was 0-300 cm.(6)The soil water deficit of POA pratensis,Alfalfa,Caragana,jujube and Robinia pseudoacacia was 41.0%,42.5%,41.4%,42.1%,41.7% based on the water content of plant growth arrest(13.2%)respectively.The deficit was 30.7 %,52.5 %,47.6 %,40.8 % and 59.5% by the end of 2017,and it would take 12 years for Kentucky bluegrass to recover to 13.2%.Taking the soil moisture content of sloping land(15.26%)as the benchmark,the initial deficiency degrees were 49.0%,50.2%,49.3%,49.9% and 49.6% respectively,and by the end of 2017 they were 40.1%,58.9% and 54.7%,respectively.48.8%,65.0%,and it will take 18 years for POA pratensis to recover to 15.26% soil moisture. |
PDF Full Text Request