| Soil respiration is an ecologically-important process controlled by a variety of biotic and abiotic factors. At present, there are rare studies about the soil respiration characteristics and impact factors in beach land. In this paper, we took 3 typical land-use types in Dongting Lake beach land for examples, used automatic analyzer Li-8100 which was based on infrared dynamic analysis to carry out observations of soil respiration rate and impact factors in poplar lands, reed lands and farmlands. After analysis, we got results as follows:(1) There was a unified trend of single peak curve in diurnal variation of soil respiration of 3 land-use types. There was difference in soil respiration intensities. The lowest soil respiration rate occurred at about 5:00a.m..In spring, the peak value of poplar lands and reed lands occurred at 13:00p.m., and that of farmlands occurred at 11:00a.m.. The diurnal dynamic variation of poplar lands, reed lands and farmlands ranged in 2.89～5.94,4.47～14.16 and 0.68～1.34μmol·m-2·s-1 respectively. The ranking of daily mean soil respiration rate was reed lands>poplar lands> farmlands.In summer, the peak value of poplar lands and reed lands occurred at 17:00p.m., and that of farmlands occurred at 15:00p.m.. The diurnal dynamic variation of poplar lands, reed lands and farmlands ranged in 4.44～5.38,3.68～4.24 and 1.08～1.32μmol·m-2·s-1 respectively. The ranking of daily mean soil respiration rate was poplar lands> reed lands > farmlands.In autumn, the peak value of reed lands occurred at 15:00p.m., and that of poplar lands and farmlands occurred at 13:00p.m.. The diurnal dynamic variation of poplar lands, reed lands and farmlands ranged in 3.82～4.65,0.50～1.35 and 1.53～2.11μmol·m-2·s-1 respectively. The ranking of daily mean soil respiration rate was reed lands> poplar lands > farmlands.In winter, the peak value of reed lands occurred at 13:00p.m., and that of poplar lands and farmlands occurred at 11:00a.m.. The diurnal dynamic variation of poplar lands, reed lands and farmlands ranged in 0.55～0.93,0.29～0.94 and 0.11～0.97μmol·m-2·s-1 respectively. The ranking of daily mean soil respiration rate was poplar lands> reed lands > farmlands.(2) There was a unified trend of single peak curve in seasonal variation of soil respiration of 3 land-use types. The highest annual mean respiration rate in reed lands occurred in spring with a value of 8.21μmol·m-2·s-1, and the lowest annual mean respiration rate occurred in winter with a value of 0.56μmol·m-2·s-1. The highest annual mean respiration rate in poplar lands and farmlands occurred in summer with a respective value of 4.80 and 1.27μmol·m-2·s-1, and the lowest annual mean respiration rate occurred in winter with a respective value of 0.70 and 0.45μmol·m-2·s-1. The ranking of annual mean soil respiration rate was reed lands>poplar lands> farmlands.(3) From the correlation analysis between soil respiration rate and a serial of indicators of soil near-surface temperature, soil temperature in 0-5cm, soil moisture in 0-5cm and air humidity, we got that there were extremely significant correlations between them in 3 land-use types (p<0.01), there were significant correlations between soil respiration rate and T4 in reed lands and poplar lands (p<0.05), there was extremely significant correlation between soil respiration rate and T4 in farmlands (p<0.01), and there was extremely significant correlations between soil respiration rate and air humidity in poplar lands (p<0.01).(4) The variation characteristics of the number of soil microbial in 3 land-use types were various. The variation of bacteria number most obviously occurred in poplar lands in spring (173.1 X 104 per gram) and the bacteria number in poplar lands in other seasons were almost the same. The largest bacteria number of reed lands and farmlands both occurred in summer (253.3×104 per gram and 170×104 per gram), and the smallest of that occurred in autumn (87.2×104 per gram and 52.3×104 per gram). The variation of fungi number most obviously occurred in poplar lands in spring (1.9×103 per gram) and in winter (0.12 X 103 per gram) on the contrary. The largest fungi number of reed lands and farmlands both occurred in summer (0.73×103 per gram and 1.57×103 per gram), and the smallest of that occurred in winter (0.23 X 103 per gram and 0.33×103 per gram). The most obvious changes of the number of actinomycetes in poplar lands, reed lands and farmlands all occurred in spring (respective 19×104 per gram,16.34×104 per gram and 4.7×104 per gram). The number of bacteria in 3 land-use types was larger than that of actinomycetes and fungi. The rankings of total annual number of bacteria, fungi and actinomycetes respectively were reed lands> poplar lands> farmlands, poplar lands> farmlands> reed lands and reed lands> poplar lands> farmlands. The correlations between the number of soil microbial and soil respiration rate were that there was a significantly positive relationship between soil respiration rate and the variation of the number of soil bacteria in 3 land-use types (p<0.05), and there was a extremely significant positive relationship(p<0.05) and no significant relationship(p<0.01) between soil respiration rate and the variation of the number of soil actinomycetes and fungi respectively.(5) The biggest and smallest total dry weight of ground and underground vegetation in poplar lands occurred respectively in summer (195.59g/m2) and autumn (40.12g/m2). The biggest and smallest total dry weight of ground and underground vegetation in reed lands occurred respectively in autumn (295.28g/m2) and winter (39.55g/m2) and the middle of that was in summer (275.28g/m2). The biggest and smallest total dry weight of ground and underground vegetation in farmlands occurred respectively in autumn (70.04g/m2) and winter (18.9g/m2) and the middle of that was in spring (64.56g/m2). The ranking of total annual number was reed lands> poplar lands> farmlands. Soil respiration rate was extremely correlated with dry weight of vegetation. |
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