Laboratory Simulation Of Soil Respiration Sensitivity To Temperature In Subtropical Forest In China

Soil respiration is an important component in carbon cycle of the terrestrial ecosystem.With global warming,the response of soil respiration to it has been an important study field in global change issue.The object of this paper is to understand the soil respiration sensitivity to temperature in subtropical forest in China leaving other factors out of consideration.Soil samples were collected from two sites:one is Xiashu experimental site in Jiangsu province,southeastern China, where we chose a typical secondary Quercus variabilis forest and a Pinus taeda plantation and sampled soil in 0-10 cm layer with four replications each;the other is four different plant communities—evergreen broadleaf forest,coniferous forest, dwarf forest,and alpine meadow along elevation gradients in Wuyi Mountain,and we sampled soil in 0-10 cm and 10-25 cm layer with three replications each plant community.The soil samples were incubated in closed-jars in laboratory under 5℃, 15℃,25℃and 35℃,respectively.The alkali absorption(AA)method was applied to measure soil respiration,and soil properties were also measured.The paper analyzed the variation of the cumulative CO_2-releasing dynamics and the Q₁₀value differences between secondary Quercus variabilis forest and a Pinus taeda plantation in the studied region,and also in Wuyi Mountain.My results indicated:(1)With the temperature ranging from 5℃to 35℃,the cumulation of soil respiration constantly increased.(2)There was no significant difference between typical secondary Quercus variabilis forest and Pinus taeda plantation under 5℃,15℃and 25℃,and the dynamic changes of soil CO₂ release conformed to each other.But in 35℃,the former was larger than the latter.The cumulation of soil respiration did not increase in 25℃than that in 5℃and 15℃.(3)Q₁₀value in a typical secondary Quercus variabilis forest and a Pinus taeda plantation varied from 1.06 to 2.46,and soil respiration was sensitive to temperature. Q₁₀value in a typical secondary Quercus variabilis forest was larger than that in a Pinus taeda plantation.Typical secondary Quercus variabilis forest would release more CO₂ than Pinus taeda plantation with increasingly serious global warming.(4)In evergreen broadleaf forest,coniferous forest and dwarf forest,soil respiration cumulation in 0～10cm layer was larger than that in 10～25cm.With the rising temperature,significant difference between different layers tended to disappear. (5)Q₁₀value in Wuyi Mountain varied from 1.35 to 2.73,and soil respiration was sensitive to temperature.Under 1800m,Q₁₀value increased with the rising elevation,but decreased above that.(6)Cumulation of soil respiration did not vary accordingly to the rise of elevation under the controlled temperatures except those factors such as roots,water, and light.(7)Q₁₀value would go down with the extension of time,and soil respiration showed the adaptability to temperature.