Soil Moisture Depletion And Infiltration Depth And Soil Respiration Of Different Vegetation In The Water-wind Erosion Crisscross Region

In order to assessing the impact of depth of soil moisture depleted by plants andinfiltrated after precipitation and different land-use types with different soil moisture andtemperature on seasonal soil respiration, we chose typical land-use plots in the water-winderosion crisscross region of the Loess Plateau at Liudaogou Watershed during growthseasons of the year2009²012. Results showed that the soil moisture of bare land, farmland, abandoned land, artificial grass （shrubs） lands （alfalfa land, C. Korshinkii land and A.adsurgens land） and local typical grassland （Wild grass land and S. bungeana land） allreduced during the normal flow （2010） and dry （2011） years; soil moisture of some plotswere added in the high flow year （2012）. In the normal and dry years, depths of soilmoisture depleted by plants followed the rule: C. Korshinkii land （160²60cm）＞abandoned land （140²60cm）＞A. adsurgens land （120²60cm）＞alfalfa land（120¹60cm）≈S. bungeana land （120¹60cm）≈Wild grass land （160cm）＞farm land（140cm）＞bare land （120cm）, while infiltration ones were farm land （140cm）＞bare land（120cm）＞abandoned land （100cm）＞Wild grass land （90cm）＞S. bungeana land（70¹40cm）＞A. adsurgens land （70¹20cm）＞alfalfa land （70⁹0cm）＞C. Korshinkiiland （70cm）. The depth of soil moisture depletion was deeper than infiltration in common.In the high flow year （2012）, there was no negative balance of water storage in the plots ofbare land, alfalfa land, Wild grass land and A. adsurgens land, but soil moisture in C.Korshinkii land was depleted form soil surface till260cm layer, the others were in order ofabandoned land＞farm land＞S. bungeana land; depths of soil moisture infiltrated afterprecipitation were as follow: farm land （260cm）＞bare land （220cm）＞abandoned land （180cm）＝C. Korshinkii land （180cm）＞Wild grass land （160cm）＝alfalfa land （160cm）＞S. bungeana land （120cm）＞A. adsurgens land （60cm）. The above-ground dry biomassof typical plants were C. Korshinkii land (464g·m^-2)＞abandoned land (377g·m^-2)＞alfalfa land (357g·m^-2)＞A. adsurgens land (314g·m^-2)＞Wild grass land (214g·m^-2)≈S.bungeana land (213g·m^-2)＞farm land (41g·m^-2). Artificial grass （shrubs） lands whichhad high biomass also showed an appearance of high infiltrated mass and depths. As aresult, we should fully consider the annual exchange depth of soil moisture during themanagement of land conversion from farm-land back to grass-land or shrub-land, then takecertain measures to reduce the depths depletion of soil moisture and increase theinfiltration.Soil respiration was measured by the Closed-Dynamic-Chamber Infrared gas analyzer（IRGA）, and the relationships between soil respiration and soil temperature&soil moisture&soil nutrient were analyzed. Results showed that the management of land conversionfrom farm-land back to grass-land or shrub-land would bring a significant change to soilrespiration in the water-wind erosion crisscross region, the soil respiration of farmland was1.06¹.39μmol m^-2 s-1, and soil respiration decreased to42⁶3%in the management ofland conversion from farm-land back to bare land, there was more decrement especially inJuly, August and September; The annual soil respiration rate was developed by109²00%following the conversion of abandoned plough-land to artificial grass （shrubs） lands,79¹79%to abandoned land, but a little higher to wild grass land or S. bungeana land. Thesoil respiration was dominantly controlled by the soil temperature, and10cm soiltemperature had the best dependency of soil respiration; But there was a poor correlationbetween soil respiration and soil moisture; The index models of double-factor （soilrespiration fitting with soil temperature and soil moisture, Rs=a ebT θc） was better than anysingle factor ones. We got a sort by the Q10value at10cm soil layer in a descendingmanner: plot with no plants （bare land,2.09）> farm lands （crop land and crop land on slope,2.07¹.69）> abandoned lands （abandoned land on slope, abandoned land and abandonedland on terrace,1.71¹.53）> grass （shrubs） lands （C. Korshinkii land, alfalfa land, S.bungeana land, alfalfa land on slope and wild grass land,1.51¹.42）. In case of thetemperature increasing, the management of land conversion from farm-land back tograss-land or shrub-land could reduce the sensitivity of soil respiration to temperature under the background of increasing soil respiration in the ecological system, and the Q10would decrease with soil moisture. Soil respiration could be extremely significantly relatedwith soil organic matter and total nitrogen. Therefore, soil respiration in the water-winderosion crisscross region was significantly affected by soil temperature, soil moisture, soilnutrient and land use patterns.