| Because the reservoir of soil organic carbon pool is 2-3 times higher than that of the atmospheric carbon pool. In order to understand the decomposition mechanisms of soil organic carbon and adopting the relative measures, it is essential to study the sensitivity different organic carbon pools to temperature.We collected six different soil samples, abbreviated as BF (boreal forest soil), BA (boreal farmland soil), WF (mid-warm forest soils), WA (mid-warm farmland soil), SF (sub-tropic forest soil), SA (sub-tropic farmland soil), to do the study, which includes three forest soils and three farmland soils across three different climate zones such as subtropical (Jiangxi), mid-warm (Shanxi), boreal (Hei Longjiang). We conducted an comparative decomposition incubation experiment for 290d under 20 ℃ and27℃. The decomposition dynamics of different pools(Total organic carbon, Labile organic carbon, slow organic carbon, resistant organic carbon) of organic carbon was monitored and the decomposition rate and relative Q10-q were analyzed and calculated to elucidate the carbon sequestration and response of different carbon pools under climate warming. The following conclusions were drew:(1)The original size of different pools of organic carbon content showed the order of BF(88.7 g/kg)>BA(58.1 g/kg)> WF(42.0 g/kg)> WA(32.5 g/kg)> SF(23.5 g/kg)>SA(15.9g/kg). Different pools of organic carbon from forest soils were all greater than that from farmland soil which were located in the same climate zones. The difference of total soil organic carbon content between the forest soil and farmland soil were showed biggest in the soils from sub-tropic zone perhaps due to the vegetation type (ie. broad-leaved forest).(2) Proportion of the different pools of organic carbon in the total organic carbon (TOC) showed at the order:resistant organic carbon(48%-54%)> slow organic carbon(24%-31%)> labile organic carbon(19%-28%). The proportion of labile organic carbon in forest soil were higher than that in farmland soils, while proportion of slow organic carbon and resistant organic carbon pools in the total organic carbon did not show obvious difference were not between forest soils and farmland soils.(3)The decomposition rate of different components of organic carbon are expressed as:whether it is total organic carbon or the different components of organic carbon, are as follows:the decomposition rate under 20 ℃<the decomposition rate under 27 ℃. Labile organic carbon of warm forest soil, warm and subtropical farmland soil in 290 days were completely decomposed at two temperatures, but under 27 ℃ labile organic carbon is completely decomposed ahead of time. The oxidative decomposition of organic carbon under 27 ℃ in 290 days to boreal forest soil, boreal and subtropical farmland soil were higher than under 20 ℃ about 7%,18% and 17%. In 290 days,slow organic carbon decomposition ratio of 6 tested soil samples (BF;BA;WF;WA;SF;SA) under 27 ℃ were higher than under 20℃ respectively about 2.9%, 4.2%,5.6%,5%,0.7% and 2.4%. The resistant organic carbon decomposition than under 20℃respectively 0.2%,2.2%,3.3%,1.1%,2.2% and1.3%. TOC decomposition rate is significantly higher than the decomposition rate of other components. Different organic carbon fractions are within the first month of the decomposition rate of different organic carbon fractions faster in the first month, slowed in mid-term and stabilized at different time periods of late-term.(4)The Q10-q values of organic carbon showed the following characteristics:the obvious gap of the decomposition rate of organic carbon decomposition rate for the original 1%and the later 1%under 27 ℃ and 20 ℃ were showed in BA and SF soils, with the difference of 1.3 times at two periods.The difference of Q10-q of labile organic carbon other from four soil samples at earlier period and latter period for were not obvious (most of them had the value of 1). The difference of Q10-q values of labile organic carbon at the earlier (ie.1.0-2.0) and later period (ie.2.8-4.8) showed higher in the soil samples which were not completely decomposed during incubation such as BF, BA and SF. The difference of Q10-q of labile organic carbon at earlier and later period did not show significant gap from the soils which had lower labile organic carbon and those labile carbon had been completely decomposed during incubation.Overall, the difference of Q10-q of slow organic carbon at the earlier and later period did not show big difference and their ratio were about 1.0 (ranged between 0.95and 1.30). While the difference of Q10-q at the earlier period (at the value of 1.12) and later period (1.8-2.3) of slow organic carbon were slightly higher in the two soils-WA and SA, perhaps due to that the slow organic carbon in these two farmland soils are relatively older with longer turn-over time just alike resistant organic carbon in the farmland soil caused by lack of input of fresh organic materials.The ratio of Q10-q at the earlier and later periods were all about 1 without big difference for all six soils. The specific value of Q10-q at either earlier or later periods were had the value of 2, perhaps due to that these two farmland soils had more slightly resistant carbon and were more stable with longer turn-over time. |
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