| Forest soil carbon pool,the largest carbon pool in terrestrial ecosystems,plays an important role in regulating global carbon balance and mitigating global climate change.Forest soil organic carbon as a stable and long-term carbon source directly affects vegetation productivity.Soil organic carbon is affected by climate,vegetation,topography and land use.It is of great significance to study the distribution characteristics of forest soil organic carbon and its influencing factors for soil carbon sequestration,mitigation of global climate change and soil structure stability.This paper takes the Picea schrenkiana var.tianschanica forest in the practice forest farm of Xinjiang Agricultural University as the research object,this paper studies the distribution law of soil organic carbon content and storage of Picea schrenkiana forest under different topographic factors(altitude,slope,slope direction,slope position)and stand conditions(canopy density,stand age),and discusses the leading factors affecting the distribution characteristics of soil organic carbon in the study area,It provides data basis and support for correctly evaluating the carbon sequestration capacity of mountain forest ecosystem in Xinjiang and the ecological restoration and sustainable management of mountain forest ecosystem.The main research results are as follows :(1)The average soil organic carbon content in 0-60 cm soil layer at different altitudes was 1 900～2100 m(92.03 g/kg)> 2 500～2 700 m(69.45 g/kg)> 2 300～2 500 m(66.49 g/kg)> 1 700～1 900 m(65.65 g/kg)> 2 100 ～ 2 300 m(49.40 g/kg).Soil organic carbon content increased first and then decreased with the increase of soil slope.The soil organic carbon content on the slope of 15°～24° was significantly different from that on the slope of ≥ 35°.The content of soil organic carbon in different soil layers in different slope directions showed as shady slope > semi shady slope > semi sunny slope > sunny slope.The average change trend of soil organic carbon content in 0～20 cm soil layer on different slope positions was uphill(140.15 g/kg)> downhill(98.87 g/kg)> valley(98.74 g/kg)> ridge(89.11 g/kg)>middle slope(71.85 g/kg).Under different terrain conditions,soil organic carbon showed a downward trend with the deepening of soil layer,0～20cm soil layer is the main soil layer of soil carbon storage.(2)Under different stand canopy density levels,the content of soil organic carbon increased with the increase of canopy density.The highest soil organic carbon content(111.33 g/kg)appeared in 0～20 cm soil layer under high canopy density.Soil organic carbon content of different stand ages ranged from 24.66 to 164.76 g/kg.The soil organic carbon content in the whole 0 ～60 cm soil profile showed a gradual increase with the increase of forest age.Soil organic carbon content and storage of mature forest in Picea schrenkiana forest were significantly higher than those of other forests(P<0.05).(3)The variation range of soil organic carbon content in 0～60 cm soil profile was 11.18～273.02g/kg,and the coefficient of variation of soil organic carbon content was more than 50%,indicating that the distribution of soil organic carbon content in Picea schrenkiana forest was unstable.Compared with the soil classification system,the soil quality of 0～60 cm soil layer was better.Correlation analysis showed that soil organic carbon in 0～60 cm soil layer was significantly correlated with slope aspect,bulk density and water content.Combined with stepwise regression analysis and principal component analysis,soil bulk density,water content,altitude and slope direction were the main factors affecting soil organic carbon content of Picea schrenkiana forest. |
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