Effect Of Root Cutting On Soil Respiration In Four Forests Of Central South China

The amount of litter, soil respiration, soil temperature and soil humidity have been observed in four subtropical forest types that included camphor forest, pinus forest, liquidambar forest and mixed forest with camphor and pinus in botanical garden of hunan province from January 2014 to December 2014 with two treatments including no root and control.We analysed the dynamic characteristics between soil respiration and environmental factors with different root treatments. The objective of this study is to provide data for revealing the carbon flux and its driving mechanism in subtropical forest ecosystems.In the control conditions,4 types of forest soil respiration dynamics showed a single peak trend, the maximum value appeared in June, the minimum appeared in January and December. The average value of soil respiration showed:camphor forest(2.30±0.12μmolCO2m-2·s-1)> mixed forest(2.03±0.15μmolCO2m-2·s-1)> liquidambar forest(1.79±0.23μmolCO2m-2·s-1)> pinus forest(1.62±0.17μmol CO2m-2·s-1). The annual soil respiration rate showed a cumulative emissions:camphor forest(31.92t-hm-2·a-1)> mixed forest(28.16 t·hm-2·a-1)> liquidambar forest(24.69 t·hm-2·a-1)>pinus forest(22.47 t·hm-1·a-1). The Q10 value of soil respiration in camphor forest, mixed forest, liquidambar forest and pinus forest with camphor and pinus are 1.73,1.43,1.54 and 1.58 relatively.4 types of forest soil respiration rate had a significant exponential correlation with soil temperature at 5cm (P<0.01) and the regression residues equation is R=aebt with the range of fitting coefficient R2 is 0.768-0.928; soil moistures at 5cm can use linear equation:R=aiW+bmnd the range of these two equation fitting coefficient R2 is 0.124-0.209.In root treatments conditions,4 types of forest soil respiration dynamics showed a single peak trend, the maximum value appeared in June, the minimum appeared in January and December. The average value of soil respiration showed:camphor forest(1.90±0.16 umol CO2m-2s-1)> mixed forest(1.74±0.13 μmol CO2m-2·s-1)> liquidambar forest(1.49±0.15 μmol CO2m-2·s-1)> pinus forest(1.36±0.11 μmol CO2m-2·s-1). The annual soil respiration rate showed a cumulative emissions:camphor forest(26.36 t·hm-2·a-1)> mixed forest(24.13 t·hm-2·-1)> liquidambar forest(20.81 t·hm-2·a-1)>pinus forest(18.86 t·hm-2·a-1). The Qio value of soil respiration in camphor forest, mixed forest, liquidambar forest and pinus forest with camphor and pinus are 2.05,1.65,1.77 and 1.93 relatively.4 types of forest soil respiration rate had a significant exponential correlation with soil temperature at 5cm (P<0.01) and the regression residues equation is R=aebt with the range of fitting coefficient R2 is 0.651-0.951; soil moistures at 5cm can use linear equation:R=aiW+biand the range of these two equation fitting coefficient R2 is 0.075-0.138.Root cutting treatment reduced the rate of 4 types of forest soil respiration, camphor forest (7.22%-48.53%), mixed forest (4.55%-38.62%), liquidambar forest (6.41%-40.34%), pinus forest (3.72%-54.51%), but did not change its seasonal variation trend; Compared with the control, the average value of total emissions were reduced, camphor forest, mixed forest, liquidambar forest, pinus forest 17.41%, 14.31%,15.71% and 16.06%. Root cutting treatments under 4 types of forest Q10 values showed increased, camphor forestl8.50%, mixed forest15.38%, liquidambar forest 14.94%, pinus forest 22.15%. A significant correlation of soil respiration rate and soil temperature under the condition of root and control, mixed forest 0.651, camphor forest 0.951,liquidambar forest 0.850,pinus forest 0.894.Under root cutting treatments, the correlation between soil respiration rate and soil moisture is lower than natural conditions, The correlation between soil respiration rate and soil moisture under the condition of the root and the control were not significant.