Influencing factors of soil respiration and their response to different land use types in the water-wind erosion crisscross region

In order to assess the impact of different land-use types with different soil moisture and temperature on seasonal soil respiration, we chose 6 kinds of typical land-use plots in the water-wind erosion crisscross region of the Loess Plateau at Liudaogou Watershed during growth seasons of the year 2009-2012 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. The results showed that the management of land conversion from farm-lands to grass-lands or shrub-lands would cause significant changes to soil respiration in the water-wind erosion crisscross region. The soil respiration of farmlands is 1.06-1.39 mol/（m2s）, and soil respiration is decreased to 42%-63% in the management of land conversion from farm-lands to bare lands, especially in July, August and September. The annual soil respiration rate is increased by 109%-200% following the conversion of abandoned plough-lands to artificial grass (shrubs) lands, and is about 79%-179% of farm land to abandoned lands. The annual soil respiration rate of farm-lands is a little higher than those of grass lands or S. bungeana lands. The soil respiration is dominantly controlled by the soil temperature, and 10 cm soil temperature has the best correaltion with soil respiration, while there is a poor correlation between soil respiration and soil moisture. The index model of the double-factors (soil respiration fitting with soil temperature and soil moisture, Rs=aebTc) is better than those of the single factor ones. The Q10 values in 10 cm soil layers are in the order of: plot with no plants (bare land, 2.09) farm lands (crop lands and crop lands on slope, 2.07-1.69) abandoned lands (abandoned lands on slope, abandoned lands and abandoned lands on terrace, 1.71-1.53) grass (shrubs) lands (C. Korshinkii land, alfalfa land, S. bungeana land, alfalfa land on slope and wild grass land, 1.51-1.42). In case of the temperature increasing, the management of land conversion from farm-lands back to grass-lands or shrub-lands could reduce the sensitivity of soil respiration to temperature under the background of increasing soil respiration in the ecological system, and the Q10 would decrease with the decrease of soil moisture. Soil respiration could be significantly related with soil organic matter and total nitrogen. Therefore, soil respiration in water-wind erosion crisscross regions is significantly affected by soil temperature, soil moisture, soil nutrients and land use patterns.