| Soil respiration is a major component of the global carbon cycle. Globally, the annual CO2 emission by soil respiration accounts for 10% of the atmospheric CO2, which is ten times greater than from fossil fuel combustion. And the little change of the CO2 emission by soil respiration may cause significant influence on atmospheric CO2 concentration. So far, substantial studies have investigated the changes of soil respiration and the relationship between soil respiration and abiotic factors(temperature, moisture, SOC, litter, etc.) and biological factors(microorganisms and roots, etc.). But the previous reports were mostly conducted on no erosion land. There is little knowledge on the characteristics of soil respiration on erosion land. In fact, nearly 1.1 billion hectares of the global land areas are Suffer from water erosion. Therefore, it is of great necessity to investigate the changes of soil respiration in erosion land, so as to better understand the characteristics of terrestrial CO2 and its feedback to climate change.Based on the artificial rainfall simulation experiment and field erosion simulation test, two major objectives were to investigate:(1) the response of soil respiration to different slope, rainfall intensity and rainfall duration and its main influence factors;(2) the response of soil respiration to erosion-deposition condition and its main influence factors. The simulated experiment of rainfall and slope was conducted in State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau. The treatments consist of three slope(5o, 15 o, 25o), three rainfall intensity(30, 60, 90 mm·h-1; I30, I60, I90) and three rainfall duration(0.5, 1, 1.5 h; H0.5, H1, H1.5). The soil respiration, soil temperature, moisture, runoff, sediment, soil organic carbon(SOC) were measured. The simulated experiment of soil erosion was conducted at Wangdonggou watershed, Changwu country, Shaanxi province. The treatments consist of erosion plot(E–20), no erosion plot(E0) and deposition plot(D20) with no crop land and crop land. The soil respiration, soil temperature, moisture, SOC, aboveground biomass, root biomass, crop yield and so on were measured.Main results were as follows:(1) For the same rainfall duration and rainfall intensity, soil respiration significantly decreased as the slope increased(5o>15o>25o; P<0.001), but there was no significant difference in soil temperature and soil moisture under different slopes. For the same slope and rainfall duration, soil respiration decreased with the increase of rainfall intensity(I30>I60>I90). With the increase of rainfall duration, soil respiration also showed a reduced tendency under the same slope and rainfall intensity(H0.5>H1>H1.5), and the rainfall duration had a significant influence on the soil respiration(P<0.1). With the increase of slope, rainfall intensity and rainfall duration, the loss content of SOC had increased significantly(P<0.001). There were negative linear correlation between respiration and SOC losses(R2 = 0.6919 ~ 0.7714, P≤0.1).(2) Soil respiration of no crop land showed a trend of D20>E0>E–20, and the differences reached significant level(P<0.05), while the differences of soil temperature and soil moisture among the E–20, E0 and D20 were very small. There was positive linear correlation between soil respiration and SOC content(R2 = 0.5866,P<0.05). During the whole observation period, the increase percent of CO2-C emission of D20 was higher than the decrease percent of carbon emission of E–20, the condition of erosion-deposition in no cropland caused a carbon source effect.(3) Soil respiration of crop land showed a trend of D20>E0>E–20, and the differences reached significant level(P<0.05), while the differences of soil temperature and soil moisture among the E–20, E0 and D20 were very small. There were positive linear correlation between soil respiration and SOC content, aboveground biomass and root biomass(R2 = 0.8667 ~ 0.9243,P<0.001). During the whole observation period, the increase percent of CO2-C emission of D20 was lower than the decrease percent of carbon emission of E–20, the condition of erosion-deposition in no crop land caused a carbon sink effect. Compared with E0, the biomass, root biomass and yield of E–20 were significantly decreased, while D20 showed an increase, and the increase was relatively small, the erosion-deposition caused the decrease of crop yield. |
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