A Comparative Study On Diurnal Course Of Soil Respiration Rate And Affecting Factors Of Alpine Meadow At Eastern Qinghai-Tibetan Plateau

The diurnal course of soil respiration rate of alpine meadow at Eastern Qinghai-Tibetan Plateau was measured by the soil respiration detector of Li-6400-09.In order to discuss the effects of temperature and soil physical and chemical properties on soil respiration rate,we measured air temperature, 0cm,5cm,10cm,15cm, 20cm soil temperature and the contents of soil organic carbon, total nitrogen, C/N, total P , bulk density, volume water and pH.The results indicated that all the diurnal courses were single-peak curves from three typical alpine Upland Shrub Meadow(US), Upland Meadow(UM) and Terrace Meadow(TM) we chose. There were very significant differences(P<0.01) in daily average among the various meadow types and the highest was in UM(5.34±0.339μmol/m²Â·s),followed by US(5.14±0.225μmol/m²Â·s),and the lowest was in TM(4.49±0.282μmol/m²Â·s);The maximum and minmum soil respiration rate were6.26±0.497μmol/m²Â·s,7.00±0.283μmol/m²Â·s,6.24±0.391μmol/m²Â·sand4. 05±0.508μmol/m²Â·s,3.88±0.205μmol/m²Â·s,3.13±0.245μmol/m²Â·s respectively;The local time when reached the peak and valley value were 13:00-15:00, 11:00-13:00,13:00-15:00 and05:00-07:00,05:00-07:00,05:00-07:00 separately;The rate of CO2 emission in the daytime was 1.22,1.32,1.28 times than that in the night,was very significant difference (P<0.01). There was a highly significant(P<0.01) correlation between air temperature, 0cm,5 cm soil temperature and respiration rates,especially at 5 cm depth. 10cm soil temperature was correlated with respiration rates(P<0.05), contrary to 15cm and 20cm soil temperature.Exponential model could simulate the relationship between temperature and soil respiration rate.Based on the Q10 calculated, soil respiration rate was most senstive to the soil temperature at 5cm depth and the response to temperature were: UM> US>TM. Our Q₁₀ was a little small,soil respiration rate was not so sensitive as expected to temperature change.Among all soil physical and chemical properties, the impacts of soil organic carbon, total nitrogen, C/N, total P and bulk density on US's soil respirtian rate were important, correlation coefficient(r) is 0.5-0.8,P<0.01;The correlation coefficient(r) between UM's soil respirtian rate and soil organic carbon, total nitrogen, C/N, total P , bulk density, volume water content , pH were very small,showed that these factors had no influence on UM's CO₂ emission;The efflux of CO₂ in TM was correlated with the content of soil organic carbon, total nitrogen, C/N, bulk density, volume water , pH,r=0.5-0.8,P<0.01. In a whole,the impact which vertical soil physical and chemical properties on soil respiration rate in US showed continuity and more much influence of deep properties;But the impact in TM showed discontinuity and more much influence of surface properties. Furthermore,the effect of soil physical and chemical properties on soil respiration rate was US>TM.