Study On Soil Organic Carbon And Its Fractions In Forest Soil Under Climatic Zones

In this study,forest soils in different climatic zones were taken as research objects,and the distribution,content and variation of organic carbon and its components were studied by large-scale and multi-level analysis methods,in order to provide scientific basis for soil improvement and promoting soil carbon cycle,and to provide theoretical basis for carbon sink management.This study focused on three perspectives of different climatic zones,primary,secondary forests and vertical climatic zones,to study their effects on total organic carbon,active and inactive organic carbon and aggregate carbon.The research results are as follows.First,under different climatic zones,the total organic carbon content 162.8 g/kg was the highest in the bottom layer of Ailao Mountain in the south subtropical zone,and the lowest was 9.68 g/kg in the middle layer of Xishuangbanna in the tropical zone.Among the active organic carbon,water-soluble organic carbon and easily oxidized organic carbon were the highest in the bottom of Ailao Mountain at 5.44 g/kg and 47.44 mg/kg,the lowest in the middle of Xishuangbanna and Tiantong Mountain at 0.21 g/kg and 0.52 mg/kg.The particle organic carbon were the highest in the middle of Huanglian Mountain at 65.70 g/kg,and the lowest in the high of Xishuangbanna at 6.57 g/kg.Among the inactive organic carbon,humic acid carbon and humin carbon were the highest in the bottom layer of Ailao Mountains at 35.92 g/kg and 98.37 g/kg,while fulvic acid carbon and humin carbon were the lowest in the middle layer of Xishuangbanna at 2.31 g/kg and 5.16 g/kg,and the highest fulvic acid carbon and lowest humic acid carbon in the middle layer of Huanglian Mountains at 34.12 g/kg and the middle layer of Dujiangyan at 1.99 g/kg,respectively.The extremum carbon content of aggregates is 35.86-5.76 g/kg,25.50-3.94 g/kg,72.07-16.43 g/kg according to their size(0.25-2 mm,0.053-0.25 mm and < 0.053 mm),which corresponds to the middle layer of Longwan and Dujiangyan,the high layer of Huping Mountain and the middle layer of Dujiangyan,the high layer of Longwan and the middle layer of Dujiangyan,respectively.Second,compared with primary and secondary forests,the extremum organic carbon content of primary forests was 142.35-27.63 g/kg,which was higher than that of secondary forests at 69.80-14.72 g/kg,corresponding to Huzhong Jianfengling,Changbai and Taiyue mountains,respectively.Among the active organic carbon,the extreme contents of water-soluble organic carbon in primary and secondary forests were 6.37-0.48 g/kg and 1.99-0.54 g/kg,respectively,corresponding to Huzhong and Shennongjia,Liangshui and Jianfengling.The extreme contents of oxidizable organic carbon were 46.52-4.40 mg/kg and 48.59-0.30 mg/kg,respectively,corresponding to Dinghu,Liangshui,Changbai and Jiulian Mountain;and the extreme contents of particulate organic carbon were 40.31-13.96 g/kg and 34.85-6.65 g/kg,respectively,corresponding to Changbai and Dongling Mountain,Shennongjia and Taiyue Mountain,respectively.Among the inactive organic carbon,the humic acid carbon content of primary and secondary forests was 38.77-3.29 g/kg and 12.66-3.01 g/kg,respectively,corresponding to Huzhong and Jianfengling,Liangshui and Jianfengling.The extreme carbon content of fulvic acid is 11.05-1.55 g/kg and 9.60-2.11 g/kg,respectively,corresponding to Changbai and Dongling Mountain,Changbai and Taiyue Mountain.The extreme carbon content of Humin was 89.85-18.21 g/kg and 46.27-3.18 g/kg,respectively,corresponding to Huzhong and Jianfengling,Changbai Mountain and Huzhong.The aggregate carbon of primary and secondary forests ranged in size from large to small(0.25-2 mm,0.053-0.25 mm and <0.053 mm)according to particle size were(1)39.34-12.66 g/kg and 33.43-12.66 g/kg and 33.43-4.37 g/kg,respectively,corresponding to Changbai and Dongling Mountain,Shennongjia and Taiyue Mountain;(2)39.73-9.41 g/kg and 34.19-3.85 g/kg,respectively,corresponding to Liangshui and Dongling Mountain,Shennongjia and Taiyue Mountain;(3)82.54-31.76 g/kg and 39.69-11.45 g/kg,respectively,corresponding to Huzhong and Dongling Mountain,Shennongjia and Huzhong.Third,different vertical climatic zones in Changbai Mountain have resulted in different stands.The total organic carbon extreme contents were 81.7-43.6 g/kg,which are broad-leaved forest and alpine tundra,respectively.In active organic carbon,the extreme contents of water-soluble organic carbon content were 0.82-0.55 g/kg,corresponding to Yuehu-tundra and spruce-fir,respectively;the extreme contents of easily oxidizable organic carbon were 11.3-2.68 g/kg,corresponding to spruce-fir and alpine tundra respectively;the extreme contents of particulate organic carbon were 50.7-12.8 g/kg,corresponding to broad-leaved forest and spruce-fir,respectively.Among the inactive organic carbon,the extreme contents of humic acid and fulvic acid carbon were 8.70-2.09 g/kg and 8.09-4.25 g/kg,respectively,corresponding to birch forest and spruce fir,while the extreme contents of Humin carbon were 65.7-30.2 g/kg,corresponding to broad-leaved forest and alpine tundra,respectively.The extremum carbon content of aggregates ranged from 0.25-2mm,0.053-0.25 mm and <0.053 mm in size.The extreimum carbon content of aggregates were 9.46-73.3,6.28-59.3 and 26.3-55.2 g/kg,respectively.Broad-leaved forest was the highest,alpine tundra was the lowest of the first two,and birch forest was the highest and coniferous forest was the lowest of the latter.The activation degree of the ratio of free ferric aluminium oxide to amorphous ferric aluminium oxide increased with the increase of altitude.Fourth,the correlation analysis showed that the correlation between total organic carbon and inactive organic carbon was decreased with latitude and the south of climate zone,showed a trend of first decreasing and then increasing,while active organic carbon was the opposite.Except in the cold and middle temperate zones,the aggregate carbon of the three particle sizes was significantly correlated with each other.The organic carbon of Changbai Mountain was significantly correlated with humin carbon and amorphous alumina,particulate organic carbon was significantly correlated with humic acid carbon and silt,and fulvic acid carbon was significantly correlated with humic acid carbon and free alumina.Large and micro aggregates carbon were significantly correlated with organic carbon and particulate organic carbon,and macro aggregates carbon was also significantly correlated with micro aggregates carbon and silt.Micro aggregate carbon was significantly correlated with fulvic acid carbon,free and amorphous alumina.