Variation Of Temperature Sensitivity Of Soil Respiration Of Apple Orchard In The Weibei Dryland

Soil respiration is a key component of the carbon cycle of the terrestrial ecosystems, the temperature sensitivity of soil respiration(Q10) was the key process in the understanding of terrestrial ecosystem carbon cycle, and its response to the climate change has dramatic effects on the feedback between terrestrial carbon cycle and global warming. To evaluate orchard variability of soil respiration and Q10 and the response of them to its influencing factors is helpful for a deep understanding about the carbon stock changes of regional terrestrial ecosystem.The Loess Plateau is particularly susceptible to soil erosion due to the fractured and steep terrain and the continental monsoon climate. To address this problem, an integrated management of small watershed has been practiced since 1980 s in an attempt to convert cropland to woodland, grassland or apple orchard in the Loess Plateau. There were a lot of studies on soil respiration and Q10 of cropland, grass land and woodland, whereas little about apple orchard in this region. To evaluate orchard variability of soil respiration and temperature sensitively of soil respiration is helpful to accurately estimate the soil respiration and carbon cycle of terrestrial ecosystem in the Loess Plateau.A field experiment was conducted in the Wang Donggou watershed, Shaanxi, China. Soil respiration, soil temperature, soil moisture and roots biomasses were periodically measured in a mature apple orchard established in 2000 from 2011 to 2013. The variation of spatial of soil respiration and Q10 in tree-scale was analyzed and the sampling method was carried on the deep discussion. In order to analyze the changed in soil respiration and Q10 in different ecosystems, the adjacent farmland, grass land and bare land of the station were also selected as the object to be measured. In addition, the influence from topography was also analyzed in this study.Main results were as follows:(1) Significantly seasonal and spatial variation of soil respiration in Orchard. For the seasonal, more sample number should be set to achieve the accuracy of 10% in the periods of orchard leaf growing and precipitation, For spatial, there was no significant in the sample number to achieve the accuracy of 10%.(2) The mean soil respiration rate at D0.5 was 21%, 35% and 42% higher, respectively; and the temperature sensitivity of soil respiration(Q10) at D0.5 was 15%, 30% and 12% higher than that at D2 in 2011, 2012, and 2013, respectively. There was no significant difference in soil temperature and moisture between D0.5 and D2, whereas fine root biomass at D0.5 were 64%, 108%, and 114% higher than that at D2 in 2011-2013, respectively. Fine root biomass had a positive linear relationship with accumulative soil respiration and Q10.(3) Soil respiration and Q10 were different in four ecosystems. Mean soil respiration was grass land [3.67 μmol(m2 s)-1] > crop land [2.33 μmol(m2 s)-1] > apple orchard [1.99 μmol(m2 s)-1] > bare land [0.86 μmol(m2 s)-1]. Whereas Q10 was: crop land(2.80) > grass land(1.82) > apple orchard(1.60) > bare land(1.53).(4) Soil respiration and Q10 were influenced by topography. Soil respiration of apple orchard was 25% higher in table land than that in slope land, whereas Q10 was 6.5% higher in slope land than that in table land. In addition, soil respiration of crop land and grass land were higher 33% and 96% than that in slope land, respectively. Similar to apple orchard, Q10 of grass land in slope land was higher than that in the table land(2.10 vs. 1.82), whereas it was higher in slope land than that in table land of crop land(2.80 vs. 2.31). A significant linear correlation was found between Q10 and soil organic carbon, and Q10 was higher in slope land than that in table land with same soil organic carbon content.