宁夏天然草地土壤有机碳分布格局及驱动因素

Distribution pattern and driving factors of soil organic carbon of natural grassland in Ningxia

摘要:

【目的】 草地作为重要的土壤碳库，探究其有机碳的分布格局及影响因素对缓解温室效应、草地生态系统评价以及退化草地生态恢复具有重要意义。【方法】 以宁夏3 种类型天然草地（草甸草原、典型草原、荒漠草原）为研究对象，在195 个样地测定0~20 cm 和20~40 cm 土层土壤有机碳（Soil OrganicCarbon，SOC）含量，利用分段结构方程模型（Segmented structural equation model）揭示土壤SOC含量与地理、气候、植被、和土壤因子的关系。【结果】 在水平方向上0~20 cm 和20~40 cm 土层SOC 平均含量分别为 9. 46 和 8. 25 g/kg，草甸草原＞典型草原＞荒漠草原；在垂直剖面上SOC 平均含量随土层深度增加而减少；由南到北呈递减的变化趋势。分段结构方程表明：在0~20 和20~40 cm 土层中SOC 含量与TN、TP 和丰富度指数呈极显著正相关（P＜0. 01），与pH 值和年均温（MAT）呈极显著负相关（P＜0. 01），与年降水量（MAP）没有显著关系。0~20 cm 土层中，总效应由大到小依次为：气候因子（0. 38）＞土壤因子（0. 21）＞丰富度指数（0. 12）。20-40 cm 土层中，总效应由大到小依次为土壤因子（0. 39）＞气候因子（0. 23）＞丰富度指数（0. 13）。【结论】 分段结构方程结果显示雨热条件是影响表层土壤SOC 含量的主要因子，TN 和TP 是影响深层土壤SOC 含量的主要因子。

Abstract:

【Objective】 Grassland is an important soil carbon pool. It is important to investigate the distributionpattern and influencing factors of organic carbon in grasslands in order to mitigate the greenhouse effect. The investigationis also of great significance in grassland ecosystem evaluation and ecological restoration of degraded grasslands.【Method】 In this paper，three natural grassland types （meadow steppe，typical steppe and desert steppe） in Ningxiawere taken as the research object. Soil organic carbon（ SOC） in 0~20 cm and 20~40 cm soil layers was measured in195 sample plots. The Composite structural equation model was used to reveal the relationship between soil organiccarbon content and geography，climate，vegetation and soil factors.【Result】 The results showed that in the horizontaldirection，the average SOC content of natural grassland in 0~20 cm and 20~40 cm soil layers was 9. 46 g/kg and8. 25 g/kg，respectively，with the order of meadow grassland ＞ typical grassland ＞ desert grassland. In the verticalsection，SOC decreased with the increased of soil depth. There was a decreased trend from south to north. The segmentalstructural equation showed that in 0~20 cm and 20~40 cm soil layers，SOC content was positively correlatedwith TN，TP，and Margalef richness indices （P＜0. 01），and negatively correlated with pH and MAT （P＜0. 01），but had no significant relationship with MAP. In 0~20 cm soil layer，the total effect was in the order of climate factor（0. 38）＞soil factor （0. 21）＞Margale index （0. 12）. In the 20~40 cm soil layer，the total effect was in the order ofsoil factor （0. 39）＞climate factor （0. 23） ＞Margale index （0. 13）.【Conclusion】 The results of the fractional structuralequation showed that rain and heat conditions were the main factors affecting the SOC content of the surfacesoil. TN and TP were the main factors affecting the SOC content of the deep soil.