Research Of Soil Respiration Under Different Vegetation Types In The Loess Hilly And Gully Region

The global land soil has a huge carbon storage, its stability is related to whether the global ecosystem carbon cycle is normal.Soil respiration is an important component of carbon cycle, so it is important to study the change rule of soil respiration,which plays an important role to measure the fluctuation of soil carbon pool.Soil respiration is mainly characterized by the respiration rate.In this paper,through the research on the soil respiration rate of the runoff plot(simulated natural slope) and the plat ground,to explore.The variation characteristics and influencing factors of soil respiration rate under different vegetation cover in the loess hilly gully region.To provide a reference for future estimation of carbon budget in this area.This paper is to study the run off plot and flat ground of different vegetation coverage, which is located in the Science and technology demonstration area of Soil and Water Conservation Science Research Institute in Gansu Province. And from December 2014 to January 2015,using the li-cor 8100 open type instrument of soil respiration,to measure soil respiration rate of different vegetation(Onobrychis viciaefolia, wasteland, CK, alfalfa, alfalfa(flat), Astragalus adsurgens(flat) and its affecting factors of diurnal and seasonal dynamics of the determination.The main results are as follows:(1) Diurnal variation of the respiration rate shows a peak and valley value, All shows a single peak curve trend, daytime respiration rate is higher than the night;the daily variance law was significantly related to solar activities.The daily variation of the four seasons is:Spring, Onobrychis viciaefolia(HDC), wasteland(HD), control group(CK), alfalfa(MX),alfalfa(MXP,flat), Astragalus adsurgens(SDW,flat),whose respiration rate were respectively ranged from 0.16 ~ 0.64, 0.05 to 0.56, 0.05 to 0.55, 0.28 ~ 0.71, 0.14 ~ 0.6, 0.4 ~ 0.98μmol·m-2·s-1, with an average of 0.4, 0.3, 0.29, 0.49, 0.37 and 0.69 μ mol m-2 s-1.Summer, HDC, HD, CK, MX, MXP, SDW, five respiratory rate respectively was 3.65~6.23, 1.44 ~2.93, 0.71~2.38, 3.07~ 6.33, 3.22~5.26, 418~649μmol·m-2·s-1.The rate of respiration was generally higher than that in spring, Mean values were 4.94,2.18,1.54,4.55,4.24,5.34μmol·m-2·s-1.Autumn,HDC,HD,CK,MX,MXP,SDW, five respiratory rate respectively was 1.66 ~5.62,0.24 ~ 2.21,0.05 ~ 0.64,1.38 ~ 5.68,0.65 ~ 2.65,1.51 ~ 6.5μmol·m-2·s-1. Daily average respiratory rate were 3.29,1.11,0.21,2.92,1.68,3.08μmol·m-2·s-1.Winter,HDC,HD,CK,MX,MXP,SDW,five respiratory rate respectively was 0.58 ~ 1.11,0.13 ~0.78,0.02~0.65,0.47~1.32,0.86~2.08μmol·m-2·s-1.In autumn, Diurnal variation of respiration rate was the largest, and the changes in winter and spring in winter and in spring was relatively stable,and the daily changes in winter and spring was relatively stable,Change range is not big. The respiration rate of CK is less than the wasteland.(2) The seasonal variation of soil respiration rate was significant. The respiratory rate showed that summer > autumn > spring > winter, summer respiratory rate is higher, the fluctuation of autumn respiratory rate is the biggest, the fluctuation of spring and winter respiratory rate is small, relatively stable.(3) The change of soil respiration and temperature(air temperature, surface temperature and soil temperature in 5cm) fluctuation, fitting by exponential model to simulate high degree(0.9), soil temperature in 5cm was the highest in the fitting degree.The contribution rate of soil respiration rate was 91.67%. And changes of soil respiration rate with temperature fluctuation shows significant correlation(P < 0.01).(4) Onobrychis viciaefolia, wasteland, CK, alfalfa, alfalfa(flat), Astragalus adsurgens(flat): atmospheric temperature of Q10(1.4667, 2.2167, 2.9212, 1.668, 1.5683, 1.5952); surface temperature of Q10(1.4049, 2.0751, 2.8123, 1.7229, 1.5220, 1.5543); soil temperature of Q10(1.6770, 2.1022, 2.6671, 2.1404, 2.0097, 2.2012).So the difference in Q10 is visible. Due to the soil and vegetation coverage, the sensitivity of respiration rate to temperature fluctuations is different. The sensitivity: Run off plots > flat area; vegetation cover > wasteland.So the sensitivity is higher of the respiration rate to soil temperature.(5) The variation of soil respiration rate and the fluctuation of soil which content water are linear correlation(P < 0.05), the contribution rate of the fluctuation of soil which content water to the variation of soil respiration rate respectively are 72.65%(HDC), 58.02%(HD), 62.65%(CK), 65.05%(MX) and 60.07(MXP), 72.93(SDW). The average contribution rate reached about 65.23% and the variation of respiration rate is explained higher by the single factor of moisture, especially in the low water content.(6) The p H of(HDC, HD, CK, MX, MXP, SDW) range from 8.5 to 9.0,which belongs to alkaline soil, The total N, P and K had little difference, the maximum of the Astragalus adsurgens which content organic matter is 11.9g/kg. The content of available nitrogen of alfalfa was the highest, the value is 21.97/22.98(g / kg), the available P and K: the flat ground is higher than run off plots.