| Climate warming and coping strategies have become a major global issue of universal concern to the international community.The importance of soil organic carbon(SOC)in the carbon cycle and its sensitivity to climate change mean that small changes in its content will play an important feedback role in future climate warming.As an important part of terrestrial ecosystems,mountain ecosystems not only play an important role in the generation and maintenance of biodiversity,but also play a key role in regulating global carbon,nitrogen cycles.Altitude gradients change regional microclimates,resulting in differences in soil organic carbon content.Therefore,plateau mountains are ideal research areas for carbon cycling in terrestrial ecosystems because of their obvious elevation gradients.In this study,a global database of soil organic carbon under different altitude gradients was established based on global publications.At the same time the soil organic carbon content at different altitude gradients in Baima Snow Mountain,Diqing Prefecture,Yunnan Province,was determined.By analyzing soil organic carbon content and explanatory variables(Climate factors,soil factors and ecosystem types),the distribution law of soil organic carbon and its regulatory factors at different altitude gradients at global and regional scales were discussed.The main results are as follows:(1)At the global scale,soil organic carbon shows different variation patterns along the altitudinal gradient.The soil organic carbon content in different temperature regions showed different trends with the increase of altitude,the fluctuation range of organic carbon content in deep soil at high altitude is small.There is a significant correlation between environmental factors and soil organic carbon content,among which altitude,soil temperature and soil organic carbon content are positively correlated.(2)The content of soil organic carbon in Baima Snow Mountain increases first and then decreases with the increase of the altitude gradient.The soil organic carbon content of the four altitude gradients is 14.19 g/kg(2500 m)、67.15 g/kg(3200 m)、76.68 g/kg(3800 m)、26.33 g/kg(4500 m).There were significant differences in soil organic carbon content across altitude gradients,except for the 2500 m altitude gradient,the soil organic carbon content of the other altitude gradients is inversely proportional to the soil depth,showing obvious stratification characteristics.The volatility of the methane production potential of Baima Snow Mountain increases with altitude.The soil microbial biomass carbon has a significant driving effect on methane production potential,and the potential is greater under alkaline conditions.(3)Studies have shown that soil organic carbon content is affected by a variety of factors.The inconsistency between the Baima Snow Mountain alpine wetland case study and the global review on soil organic carbon content is that altitude is the most important influencing factor of organic carbon in regional studies,but the contribution rate of climate factors and soil factors is higher than that of altitude gradients on the global scale.The results showed that the relationship between soil organic carbon content and altitude under different altitude gradients on a global scale showed a nonlinear increase.The case study of the alpine wetland in Baima Snow Mountain shows that the soil organic carbon content is distributed in a unimodal curve with the altitude gradient,and the stability of soil organic carbon in the deep layer at high altitude is better.The results of this study are expected to provide scientific basis and technical support for the rational use of land,vegetation restoration and carbon pool protection in mountain ecosystems. |
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