Effect Of Litter Addition And Exclusion 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 May2011to August2012with two treatments including litter removal and litter addition. We analysed the dynamic characteristics between soil respiration and environmental factors with different litter treatments. The objective of this study is to provide data for revealing the carbon flux and its driving mechanism in subtropical forest ecosystems.(1) The total quantity of litter of four forest types was order by mixed forest(4478.14kg·hm-2·a-1)>liquidambar forest(4297.58kg·hm-2·a-1)>pinus forest(3405.12kg·hm-2·a-1)> camphor forest(3264.94kg·hm-2·a-1).(2) The annual variation of soil respiration in four forest types showed similar a single peak, with the minimum value appearing from February to March. The annual average soil respiration values are camphor forest(2.49μmol CO2m-2·s-1)> mixed forest(2.3μmol CO2m-2·s-1)> liquidambar forest(1.68μmol CO2m-2·s-1)> pinus forest(1.66μmol CO2m-2·s-1).(3) Significant relationships were found between litter-fall and soil respiration in four forest types. The soil respiration rates in four forest types presented downward trend with litter removal, and the annual average soil respiration rates in camphor forest, pinus forest, liquidambar forest and mixed forest are1.94,1.39,1.52and1.77μmol CO2m-2·s-1relatively. Soil respiration was significantly decreased about59.12%,26.12%,16.12%and53.45%relatively to controls. The soil respiration rates in four forest types presented increasing trend with litter addition, and the annual average soil respiration rates in camphor forest, pinus forest, liquidambar forest and mixed forest are2.85,1.94,2.34and2.6μmol CO2m-2·s-1relatively. Soil respiration was significantly increased about36.16%,28.18%,66.18%and30.12%relatively to controls. There were significant differences (p<0.001) between litter removal, litter addition and controls.(4) The annual average soil respiration rates and annual cumulative emission presented:camphor forest(2.49μmol CO2m-2·s-1,34.54t·hm-2·a-1)>mixed forest(2.3μmol CO2m-2·s-1,31.92t·hm-2·a-1)> liquidambar forest(1.68μmol CO2m-2·s-1,23.3t·hm-2·a-1) >pinus forest(1.66μmol CO2m-2·s-1,23.03t·hm-2·a-1); the annual average soil respiration rates and annual cumulative emission in all kinds of forests presented:litter addition> controls> litter removal.(5) The relationship between soil respiration rate and soil temperature at5cm with different litter treatment was significant (P<0.001) and the regression residues equation is R=aebt with the range of fitting coefficient R2is0.595-0.847; soil moistures at5cm can use linear equation:R=a1W+b1and the range of these two equation fitting coefficient R2is0.595-0.847.The double-factor module analysis of the effects of soil temperature and soil moistures on soil respiration in four forest types can use linear equation:R=aebTWc. Soil temperature and soil moistures in four forest types explain the change of soil respiration rate is60.5%-85%and the double-factor module analysis relative coefficient is higher than the single-factor module analysis. The result shows that soil temperature and soil moistures together can have effect on soil respiration.(6)The Q10value of soil respiration in camphor forest, pinus forest, liquidambar forest and mixed forest with camphor and pinus are1.87,1.59,1.64and1.97relatively; the Q10value of soil respiration with litter removal are2.02,1.53,1.85and2.01relatively; the Q10value of soil respiration with litter removal are2.04,2.08,1.87and1.98relatively; The Q10value of soil respiration in all forests except pinus forest presented an increase of2%-30.8%. But all the Q10values are existed in1.5-2.1.