| Soil respiration is an key component of global carbon cycle, which has great significance for the understanding of carbon cycle in forest ecosystems and global climate change. The southeast Sandy Eucalyptus grandis×E.urophylla plantation and Pinus elliottii plantations were selected to conduct a study to assess the impacts of differrent carbon input ways (changing treatments of removing root, removing litter, adding litter, exchange litter) on soil respiration. Thus, the soil dynamic respiration, temperature and humidity had been observed from January 2015 to February 2016, as well as the relationship between soil respiration rate and environmental variables, and the main results were as follows:(1) Soil respiration diurnal dynamics of blank tests in differernt plantations. Eucalyptus grandis×E.urophylla plantations and Pinus elliottii plantations soil respiration diurnal variation was approximate single peak in different seasons, the trend is broadly consistent and summer soil respiration was significantly larger than other three seasons. The maximum soil respiration rate of two stands in different seasons occurred at night 23:00-5:00, and the minimum appeared at 11: 00-15:00 of a day. The soil respiration rate of Eucalyptus grandis×E.urophylla plantations followed the order:Summer 4.24μmolCO2m-2·s-1> Autumn 2.μmolCO2m-2·s-1> Spring 2.μmolCO2m-2·s-1> Winter 1.82μmolCO2m-2·s-1>. Pinus elliottii plantations soil respiration rate followed the order:Summer 3.μmolCO2m-2·s-1> Autumn 1.μmolCO2m-2·s-1> Spring 1.76μmolCO2m-2·s-1> Winter 1.μmolCO2m-2·s-1.(2) Monthly soil respiration pattern. Soil respiration rate had significantly monthly dynamics in different treatments. Eucalyptus grandis×E.urophylla plantations monthly soil respiration rate were in the followed order; adding litter 3.μmolCO2m-2·s-1> control 2.μmolCO2m-2·s-1> exchange litter 2.μmolCO2m-2·s-1> removing litter 2.μmolCO2m-2·s-1 > removing root 2.μmolCO2m-2·s-1. Pinus elliottii plantations monthly soil respiration rate were in the followed order:adding litter 2.μmolCO2m-2·s-1> exchange litter 2.39μmolCO2m-2·s-1> > control 2.μmolCO2m-2·s-1> removing litter 2.μmolCO2m-2·s-1> removing root 2.μmolCO2m-2·s-1.(3) The soil respiration rate had a extremly significant correlation with the soil temperature in different treatments of two forest stand (P< 0.01). The Q10 value of different treatments appeared various degrees difference. The Q10 values of five treaments(removing roots, removing litter, adding litter, exchange litter, control) in Eucalyptus grandis×E.urophylla plantations were 2.48,2.0,2.46,2.43,2.12, and removal litter process reduces the temperature sensitivity of soil respiration Q10.Pinus elliottii plantations of Qio values were 3.16,1.89,2.25,1.66,2.20, removal litter process and change litter process reduces the temperature sensitivity of soil respiration Qio.(4) The soil respiration of removing roots in Eucalyptus grandis×E.urophylla plantations, were related to the soil humidity (P< 0.05), The soil respiration of removing roots and adding litter in Pinus elliottii plantations were relate to the soil humidity (P<0.05). The correlation coefficient of the other treatments in two forest stand were 0.002-0.069, and P value within the range of 0.122-0.784, there was no significant relationship between soil respiration and soil humidity.(5) Two-factor relationship model indicated that soil temperature and humidity accounted for 52.9%-72.4% of soil respiration variations in Eucalyptus grandis×E.urophylla plantations, 48.4%-80.1% of soil respiration variations in Pinus elliottii plantations. The two-factor relationship model showed that soil temperature and humidity accounted for 48.4%-80.1% of soil respiration variations in two kinds forest, than the single factor soil temperature explain variation of soil respiration 46.56%-80.03%.Two-factor model can better explain the changes in soil respiration.(6) The soil respiration in flux of removing litter, adding litter in Eucalyptus grandis^E.urophylla plantations were 782 gC·m-2a-1、1291 gC·m-2a-1、1086 gC·m-2a-1、, significantly higher than Pinus elliottii plantations of 771 gC·m-2a-1、880 gC·m-2a-1、820 gC·m-2a-1、. The soil respiration in flux of removing roots, exchange litter in Eucalyptus grandis ×E.urophylla plantations were 746 gC·m-2a-1、799 gC·m-2a-1,smaller than Pine plantations of 753 gC·m-2a-1、872 gC·m-2a-1.Eucalyptus grandis×E.urophylla plantations soil respiration in flux declined by 31.3%,27.1% and 26.5% after removing roots, removing litter and exchange litter, and increase by 18.9% after adding litter. Pinus elliottii plantations soil respiration in flux declined by 8.2%,6.0% after removing roots, removing litter, and increase by 6.5%,7.3% after adding litter and exchange litter. Studies show that eucalyptus roots and litter have greater contribution to soil respiration than that of Pinus elliottii plantations. |
PDF Full Text Request