| Xiaoxing an'mountains area locates in high latitude, and is one of the key national forest and the core of the natural forest ecosystems in China, also is conifer-leaved-boad forests with Pinus koraiensis dominated in north temperate zone, and is famous as its unique constructive species and species diversity of in north temperate forest types. The potential of fixing carbon function of vegetation and soil is great, occupies an important position in the carbon sinks in China, and could provide important protection in carbon emission reduction. To study soil organic carbon pool of forest ecosystem in Xiaoxing an'mountains in-depth and carefully, and obtain scientific and dependable bill about soil carbon storage has important significant in society, politics, ecology and economy.The soil organic carbon (SOC) under 12 main forest community types in Xiaoxing an' mountains were studied in the paper. Method of community type was chosed to analyze the fraction and distribution of SOC, and the control factoers under main forest community types in Xiaoxing an' mountains. The distribution of SOC and the relationships with the control factors under main forest community types in the area were studied, the total SOC storage of Xiaoxing an' mountains were estimated too. Major conclusions were summarized as follows:(1) The method of ring was chosed to study the soil bulk density, water holding capacity and the porosity. In Xiaoxing an' mountains, the soil bulk density of A layer was 0.30-0.82g/cm3, and the value was the largest under larch forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under Picea sp.—Abies nephlolepis forest; The soil bulk density of B layer was 0.67-1.33g/cm3, and the value was the largest under larch forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under birch forest. The soil bulk density of A and B layers were all larger with the soil were deeper.(2) In Xiaoxing an' mountains, the soil capillary water holding capacity of A layer was 64.89%-211.03%, and the value was the largest under Picea sp.—Abies nephlolepis forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under larch forest; The soil capillary water holding capacity of B layer was 33.34-134.34%, and also the value was the largest under Picea sp.—Abies nephlolepis forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under larch forest. The saturated water holding capacity of A layer was 78.35%-276%, and the value was the largest under Picea sp.—Abies nephlolepis forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under larch forest; The saturated water holding capacity of B layer was 36.35%-147.95%, and also the value was the largest under Picea sp.—Abies nephlolepis forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under larch forest. (3) In Xiaoxing an' mountains, the soil capillary porosity of A layer was 47.37%-59.53%, and the value was the largest under Picea sp.—Abies nephlolepis forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under secondary Betula costata forest; The soil capillary porosity of B layer was 40.52%-71.40%, and also the value was the largest under Picea sp.—Abies nephlolepis forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under secondary Betula costata forest. The soil uncapillary porosity of A layer was 8.86-21.96%, and the value was the largest under secondary Betula costata forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under secondary coniferous forest; The soil uncapillary porosity of B layer was 3.73-15.00%, and the value was the largest under secondary Betula costata forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under larch forest. The soil total porosity of A layer was 60.48%-79.27%, and the value was the largest under Picea sp.—Abies nephlolepis forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under secondary coniferous forest; the soil total porosity of B layer was 47.08%-79.20%, and the value was the largest under Picea sp.—Abies nephlolepis forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under larch forest.(4) In Xiaoxing an' mountains, the SOC content under main forest community type in A layer was 69.60-164.28g/kg, and the value was the largest under birch forest (164.28g/kg) and the lowest under secondary Betula costata forest (69.60g/kg), and was 124.04g/kg under broad-leaved Pinus koraiensis forest; The SOC content of B layer was 26.18-134.83g/kg, and the value was the largest under birch forest (134.83g/kg) and the lowest under secondary Populus forest (26.18g/kg), and was 84.00g/kg under broad-leaved Pinus koraiensis forest. The SOC density of A layer was 4.82-20.86kg/m2, and the value was the largest under larch forest (20.86kg/m2) and the lowest under Picea sp.—Abies nephlolepis forest (4.82kg/m2), and was 14.34kg/m2 under broad-leaved Pinus koraiensis forest; the SOC density in B layer was 1.60-24.71kg/m2, and the value was the largest under larch forest (24.71kg/m2) and the lowest under secondary Populus forest (1.60kg/m2), and was 8.81kg/m2 under broad-leaved Pinus koraiensis forest; the soil organic carbon/total nitrogen (SOC/TN) of A layer was 18.54-25.84, and the largest under Picea sp.—Abies nephlolepis forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under secondary Betula costata forest; SOC/TN of B layer was 17.05-26.43, and the largest under birch forest, the second under broad-leaved Pinus koraiensis forest, and the lowest under secondary Betula costata forest.(5) The contents of active SOC (Ca), slow SOC (Cs) and resistant SOC (Cr) of A layer were 0.65-1.84g/kg,27.78-62.44g/kg and 37.14-111.82g/kg, and respectively accounts to 0.93-2.01%,22.51-47.26% and 50.72-76.24%, and the mean residue time is 9-24 days,4-41 years and 90 years. The contents of Ca, Cs and Cr of B layer were 0.51-1.89g/kg,13.30-39.86g/kg and 11.96-85.13g/kg, and respecitively accounts to 0.86-3.51%,30.55-50.82% and 45.67-67.83%, and the mean residue time is 10-37 days,10-28 years and 90 years. (6) The control factor that influence SOC of main forest community type in Xiaoxing an'mountains was soil bulk density, the soil bulk density under broad-leaved Pinus koraiensis forest, birch forest and five other community types were all related with SOC contents, and the relationship was the largest under broad-leaved Pinus koraiensis forest (R2= 0.2706), that was the second under birch forest (R2= 0.4381), and that was the lowest under five other community types (R2= 0.3059). Litter had more influencing on the birch forest (R2= 0.3059), but had less direct influencing on other community types. The attitude had less influencing on SOC content.(7) The total area of the forest soil was 285.84×104hm2 in Xiaoxing an'mountains, the total SOC stotage was 898.14×109t. The secondary coniferous forest accounts to the largest proportion of of the total SOC storage in Xiaoxing an'mountains area with 36.69%, and secondary Populus forest accounts to the lowest with 0.21%. The order of SOC storage was the same to the distribution area, was secondary coniferous forest> secondary birch forest> larch forest> Picea sp.—Abies nephlolepis forest> secondary Betula costata forest> broad-leaved Pinus koraiensis forest> secondary Populus forest.
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