| Since the Industrial Revolution, the impact of human activities on the Earth system has been extended from the regional to global. Elevated concentrations of greenhouse gases that cause global warming has become a hot issue of common concern of humankind, CO2is the most important greenhouse gas, its contribution to global warming rate of60%or more. Soil is the largest carbon pool in terrestrial ecosystems and about2/3of the carbon stored in organic forms in the soil, the forest is a major component of terrestrial ecosystems, accounting for73%of the global soil carbon, forest soil respiration has great significance for the discussion of global CO2change and its impacts. We selected a typical subtropical forest ecosystems-camphor plantation to conduct a set carbon input changing treatments of adding litter, removing litter, adding litter X removing root, removing root and removing root X removing litter. Basing on analyzing variation of soil respiration rate and its environment factors, we build the regression models between soil respiration rate and temperature, moisture, and estimated the contribution of roots and litter to soil respiration. These results are very important to reveal the carbon flux and its driving mechanism in subtropical forest ecosystems.(1) Diurnal soil respiration pattern. Diurnal soil respiration in Adding litter and adding litter X removing root treatments all have more obvious fluctuations and were higher than that in control. Diurnal soil respiration fluctuations in the other three treatments are relatively flat, and lower than that in control. The highest soil respiration rate appeared at2:00in removing Litter treatments, at6:00in adding litter X removing root treatments and at22:00in the other treatments. Soil respiration rate in different treatments followed the order: adding litter3.85±0.44μmol·m-2s-1> adding litter X removing root2.86±0.41μmol·m-2s-1> control2.04±0.17μmol·m-2s-1> removing root1.91±0.18μmol·m-2s-1removing litter1.62±0.17μmol·m-2s-1> removing root X removing litter1.29±0.11μmol·m-2s-1(2) Seasonal soil respiration pattern. Seasonal soil respiration pattern in all treatments followed a similar single peak curve with higher rate in the summer. Quarterly soil respiration rate are in the followed order summer (3.56μmol·m-2s-1)> spring (3.29μmol·m-2s-1)> autumn (1.95μmol·m-2s-1)> winter (0.96μmol·m-2s-1), the differences between each quarter are significant. Soil respiration rate in different treatments followed the order: adding litter X removing root (2.86μmol·m-2s-1)> adding litter (2.83μmol·m-2s-1)> control (2.61μmol·m-2s-1)> removing root X removing litter (2.43μmol·m-2s-1)> removing root (2.09μmol·m-2s-1)> removing litter (1.81μmol·m-2s-1). There were no significant differences between different treatments in annual scale, but have significant differences in growing season.(3) The sensitivity of soil respiration to soil temperature (Q10): Q10values among different treatments are different. The Q10values in the plots received dual-processing are higher than in which received single processing, and the control plot have the lowest Q10values.(4) The effect of humidity on soil respiration rate. There existed a very significant positive correlation between soil respiration rate and soil moisture in all treatments (except in control treatment).(5) The coupling effect of soil temperature and moisture on soil respiration rates. The two-factor model indicated that soil temperature and moisture accounted for80.60-94.90%of seasonal soil respiration variations. Using single factor model, soil temperature and soil moisture can only explained28.91-66.75%and42.16-61.03%of soil respiration variations. These results suggested that soil respiration in camphor forest was controlled by the koinonia of soil temperature and soil moisture.(6) The contribution of roots and litter on soil respiration rate. Largest contributions of root and litter to total soil respiration rate were60.99%and58.73%, respectively, and appeared in December. Smallest contributions of root and litter to total soil respiration rate were1.53%and6.94%, and appeared in September an August, respectively. Anural contribution of root and litter to total soil respiration rate were23.09%and33.63%, respectively. |
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