| Soil is one of the most important parts of forest ecosystem, soil organic carbon pool is more than twice of atmosphere carbon pool, every year the carbon dioxide release of forest underground system is more than 10 times of fossil fuel’s combustion. Therefore, to balance forest soil organic carbon is the most urgent problem to figure out in current situation. By quantifying soil organic carbon pool, total nitrogen pool and relationships with environmental factors is essential for exploring the forest ecosystem carbon balance. We selected two kinds of forest type (Betula costata secondary forest, original mixed broadleaved Korea pine forest) by using space replacing time series method, then measured soil organic carbon (SOC), soil total nitrogen pool (TN), microbial biomass carbon and other physicochemical properties. Based on above statistical data, three carbon pools dynamics model was established in order to calculate three soil organic carbon pools (active, slow, resistant). Our results as follows:(1) SOC and TN content gradually decreased with depth between the two types of communities, the SOC contents of 10-20 cm soil layer have significantly differences between the two types of communities (P<0.05), but not significantly in other three layers (P>0.05). TN is remarkable significantly in relationship with depth. MBC content of original forest type is 14.96-19.97% higher than that of secondary forest type. Through the result of correlation analysis, SOC content has positively correlation with TN, Ws, MBC, but has a negative correlation with soil bulk density (BD). The soil organic carbon density (SOCD) contents of the two forest types have no significant differences (P>0.05), but more specifically, the SOCD contents of 10-20 cm soil layer between the two forest types have significant differences.(2) Dynamic model analysis combined the data of SOC, soil decomposition rate, MRT and other soil physical and chemical properties between the two forest types. The result of original forest type showed that soil active organic carbon pool (Ca) size is between 0.15 to 1.82g·kg-1, and the proportion is between 1.11 to 2.63%, MRT is between 7 to 12 d; Soil slow organic carbon pool (Cs) size is between 7.67 to 35.35 g·kg-1, and the proportion is between 51.10 to 72.08%, MRT is between 4 to 14 a; Soil resistant organic carbon pool (Cr) size is between 2.82 to 32.00 g·kg-1, and the proportion is between 26.50-46.26%, MRT is 191 a.The secondary forest type showed that soil active organic carbon pool (Ca) size is between 0.11 to 0.14 g·kg-1, and the proportion is between 0.64 to 1.83%, MRT is between 7 to 20 d; Soil slow organic carbon pool (Cs) size is between 8.80 to 39.18 g·kg-1. and the proportion is between 61.98 to 80.69%, MRT is between 7 to 18 a; Soil resistant organic carbon pool (Cr) size is between 1.95 to 21.97 g·kg-1, and the proportion is between 17.89-36.32%, MRT is 191 a.The decomposition rate is high during the early incubation period (1-4 d), as high as 106.17-195.56 mg·kg-1·d-1, then the decomposition rate dropped down until stable during the latter period (44-91 d),1.01-29.44 mg·kg-1·d-1.In conclusion, our results showed that the Ca of original forest is higher than that of secondary forest. Original forest’s decomposition rate is higher than secondary forest in the early incubation stage. Original forest type’s slow and resistant organic carbon pools are larger than secondary forest type, it means the original forest soil organic carbon is more stable. |
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