Temperature Sensitivity Of Soil Respiration And Soil Organic Carbon Decomposition Rate

Chinese fir plantation and paddy soils were choosed to study the temperature sensitivity of soil respiration and soil organic carbon decomposition rate in this paper.Main resesrch contents:Temperature sensitivities of soil respiration for two land use types as affected by soil temperature and incubation time were investigated by LI-8100 at laboratory.The soil samples were incubated at room temperature for 180 days.The results showed that the relationship between soil respiration and soil temperature at 5 cm depth could be described as exponential equations,and there was better fit at low soil temperature than at high soil temperature;the Q₁₀ value of soil respiration declined with increasing of soil temperature and the Q₁₀ value decreased from 3.18 to 1.40 for Chinese fir soil and 2.97 to 1.51 for paddy soil,respectively,but the differences in Q₁₀ between the two land use types were not significant,indicating that land use types had no effects on the Q₁₀ value of soil respiration in this research.It was also demonstrated by regression analysis that there was a significant negative linear relationship between Q₁₀ value and the incubation time,suggesting that incubation time was,in addition to temperature,an important related factors of Q₁₀ values.The decomposition of SOC from Chinese fir plantation and paddy field as affected by soil temperature and land use types and the changes of SOC with addition of carbon(glucose) were investigated by alkali absorb method at laboratory. The soil samples were incubated at constant temperature unit for 120 days,and the temperature choosed was 15℃and 25℃.The results showed that Change tendency of CO₂ emission rate from Chinese fir plantation and paddy field as affected by different temperatures were more fast in the earlier phase,and more slow in the later phase.Decreasing tendency of CO₂ emission rate from Chinese fir plantation and paddy field on 15℃and 25℃was descend with increasing of incubation time in this research.And the relative CO₂ emission rate increased with increasing of soil temperature;The relative initial values of CO₂ emission rate from Chinese fir plantation was biger than that from paddy field at the same temperature.The CO₂ emission rate from Chinese fir plantation was more than that from paddy field in the earlier phase(3～7 d) in 15℃,and was no significant difference in the later phase (7～112 d).The CO₂ emission rate from Chinese fir plantation was more than that from paddy field in the earlier phase(0～7 d) in 25℃,and less in the later phase (14～112 d).The loss rate of SOC from Chinese fir plantation and paddy field with glucose addition was higher than that without glucose addition at the same temperature in this research;In the earlier phase(0～28 d),the loss rate of SOC from Chinese fir plantation and paddy field with glucose addition in 25℃was higher than that in 15℃.With the increasing of incubation time,the loss rate of SOC for two land use types as affected by two temperatures was gradually consistant;The land uses had no effects on the constants of SOC decomposition rate,and temperature had a positive correlation with the constants of SOC decomposition rate, that is the constants of SOC decomposition rate increased with the temperature increasing.The decomposition of additional carbon(glucose) in Chinese fir plantation and paddy field as affected by different temperatures and land use types were investigated by alkali absorb method at laboratory.The results showed thatThe turnover rate and half-life of glucose in soils was described as first-order kinetics equation.The turnover rote of glucose can be divided into two phases,and the turnover rote of glucose as affected by temperature and land use types had different features in every phase.But the differences in decomposition amount of glucose-C in soils between Chinese fir plantation and paddy field were not significant.