| Since the implementation of returning farmland to forest(grassland)projects,soil and water loss in loess plateau phenomenon is improved obviously,and the regional economy realize the sustainable development.Precipitation is the main source of water required for plant growth on the loess plateau,and the region's unreasonable artificial vegetation configuration mode of vegetation on soil water consumption is beyond the compensation ability of natural rainfall,leading to all levels of soil moisture in different degrees of deficiency phenomenon.Therefore,needs to be clear of all kinds of plantation soil water deficit condition,and is suitable for plantation configuration mode from here.This study in a typical loess hilly-gully region-yan'an baota district of Tianhe basin of seven different artificial vegetation(including the arbor forest of Robinia pseudoacacia,Platycladus orientali,Caragana intermedia,Sea buckthorn,Platycladus orientali/Sea buckthorn,Robinia pseudoacacia/Sea buckthorn,Robinia pseudoacacia/Platycladus orientali),through the soil drilling and sampling from May to November 2016 were measured every 10 m depth in soil moisture and the plant root in August,systematic analysis of the different artificial forest lands soil moisture in time and space distribution rule and plantation plant profile distribution of fine root,soil water storage of different artificial forest lands,water consumption and soil water deficit condition.This experiment main results as follows:(1)In arid and semi-arid loess plateau areas,different plantation on soil water use are significantly different,the soil moisture under different land use types distribution difference is obvious.Soil moisture of 20 cm soil layer are biggest influenced from rainfall,rainfall infiltration depth can be up to 2 m soil layer.Artificial forest lands of Robinia pseudoacacia in 0~20 cm soil layer are high water content could be because the surface has a thickness of 3~5 cm of humus,it can effective mitigation surface soil moisture evaporation after rainfall.Average soil water content in 10 m soil layer for the whole year are Platycladus orientali forest land > Caragana intermedia forest land > Platycladus orientali/Sea buckthorn mixed forest land > Sea buckthorn forest land > Robinia pseudoacacia/Sea buckthorn mixed forest land > Robinia pseudoacacia/Platycladus orientali mixed forest land > Robinia pseudoacacia forest land.Robinia pseudoacacia forest land,Robinia pseudoacacia/Sea buckthorn mixed forest land,Robinia pseudoacacia/Platycladus orientali mixed forest land soil water content lower than other woodlands significantly.Farmland and abandoned land soil moisture vertical distribution rule are consistent,and the farmland soil moisture content is lower than the abandoned land.(2)The artificial forest of fine root dry weight density in 0~10 m soil layer,whole presents the tendency are decrease with the increase of soil depth,and root system are main distributed in 1 m soil layer.Each plantation root in addition to the surface(0~2 m)distribution is more dense,another distribution at a lower concentration area,Robinia pseudoacacia,Platycladus orientali,Caragana intermedia,Sea buckthorn is reached the second peak in 6 m soil layer.Causing of this kind of root system distribution may be randomly selected from test the roots of the trees,trees itself has distribution characteristics and the limitations of soil drilling and sampling methods.Caragana intermedia root dry weight density is the largest and the garden plot is minimal in 0 ~ 10 m soil layer.average specific root length of Robinia pseudoacacia and it mixed forests higher than other trees in 0 ~ 10 m soil layer.Robinia pseudoacacia and it mixed forests the water absorption capacity is greater than other pure forests under 5 m soil layer.(3)The soil water content of artificial forest and precipitation basically the same on the change rule.The average soil water content of Platycladus orientali forest land is the highest,but Robinia pseudoacacia/Platycladus orientali are lowest in 10 m soil layer.Platycladus orientali forest land,Robinia pseudoacacia/Sea buckthorn and Robinia pseudoacacia/Platycladus orientali mixed forest land soil water content significantly lower than the others.Soil moisture determination of the end(November)compared with the initial(may),soil water content of Platycladus orientali forest land and Robinia pseudoacacia/Platycladus orientali mixed forest land respectively increased 115.28 mm,52.95 mm.may be the trees' crown density is higher,the surface soil moisture evaporation is lesser,strip pit can collected rainwater,not only for rainfall runoff erosion energy has a lot to reduce and eliminate the effect,also reduce the slope soil erosion intensity,it can effectively increase the moisture infiltration,while other woodland soil water content are falling.Different artificial forest land soil water deficit degree is different,but the overall from the surface is small,then increases sharply,and then decreases.Robinia pseudoacacia forest land,Robinia pseudoacacia/Sea buckthorn mixed forest land and Robinia pseudoacacia/Platycladus orientali mixed forest land soil water deficit degree change law is consistent,and significantly higher than others woodlands,The soil water deficit degree of Robinia pseudoacacia forest land is the highest(29.26%?33.57%).The soil water deficit degree of Caragana intermedia forest land,Platycladus orientali forest land,Platycladus orientali /Sea buckthorn mixed forest land is obviously lower than other woodlands,among them,Caragana intermedia forest land in 5 to 7 months of soil water deficit is negative,in the meantime korshinskii woodland soil water content has not been in a deficit state as a whole.Rainfall also has certain compensation effect for soil moisture,between May to November,only the soil water compensation degree of Platycladus orientali and Robinia pseudoacacia/Platycladus orientali mixed forest land is positive,the rest of the soil water increment and soil water compensation degree are negative. |
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