内蒙古温带草地土壤有机碳组分含量和分解速率的空间格局及其影响因素

doi:10.17521/cjpe.2023.0028

摘要/Abstract

摘要：

草地是陆地生态系统的重要组成部分, 在陆地碳循环中发挥着重要作用。然而, 目前地球系统模型对草地土壤碳动态的预测仍存在较大不确定性, 其主要原因是对土壤有机碳组分含量和分解速率的空间格局及其影响因素的认识尚不充分。该研究基于在内蒙古温带草地开展的样带调查, 按土壤颗粒的粒径大小进行土壤分级, 并通过室内培养方法测定土壤碳分解速率, 在此基础上进一步利用方差分解探究气候、土壤、植物和矿物4类因素对内蒙古温带草地表层土壤有机碳组分含量和分解速率影响的相对重要性。结果显示: 1)土壤有机碳及其组分含量呈现自西南向东北增加的空间格局, 草甸草原中整土及不同组分碳含量最大, 典型草原次之, 荒漠草原最小; 而有机碳标准化的碳分解速率呈现相反的趋势。2)气候和矿物是驱动土壤有机碳组分含量空间变异的主要因素, 且两者在不同组分中的相对重要性存在差异, 即随土壤粒径减小, 矿物的相对重要性逐渐增加。3)碳分解速率受矿物、土壤和气候因素共同影响。上述结果表明不同土壤碳组分含量和碳分解速率空间变异的影响因素存在差异, 矿物因素对细颗粒组分的影响尤为重要, 意味着地球系统模型中应考虑矿物因素在不同碳组分中的作用, 从而更准确地预测全球变化背景下的草地土壤碳动态。

关键词: 土壤有机碳, 碳组分, 碳分解, 矿物, 温带草地

Abstract:

Aims Grassland is an important component of terrestrial ecosystems around the world and plays an important role in terrestrial carbon cycling. However, large uncertainties still exist in predictions of soil organic carbon (SOC) dynamics in grassland ecosystems using earth system models, partly due to an inadequate understanding of the spatial patterns and drivers of soil carbon components and the rate of decomposition. In this study, we explored the determinants of the contents of total SOC and its components as well as the rate of soil carbon decomposition in the topsoil of temperate grasslands of Nei Mongol.
Methods Soil samples at depths of 0-10 cm were collected during July to August 2015 from field sites on the Nei Mongol Plateau. We measured the contents of total SOC and its partitioning in three soil aggregate size-classes, and the decomposition rate based on laboratory incubation. In addition, we acquired a suite of explanatory factors including climatic, edaphic, vegetation, and mineral variables. Variance partitioning analyses were then used to investigate the relative importance of the four factors in affecting the contents of total SOC, aggregate-classified carbon fractions and soil carbon decomposition rate.
Important findings The contents of total SOC and three carbon fractions displayed an increasing trend from southwest to northeast of the study area, while soil carbon decomposition rate (standardized by SOC) showed a reverse trend. The carbon contents in bulk soil and different aggregate fractions are highest in the meadow steppe, followed by the typical steppe and the desert steppe; whereas soil carbon decomposition rate (standardized by SOC) was highest in the desert steppe, followed by the typical steppe and the meadow steppe. The spatial variations of carbon contents in the three soil aggregate fractions were mainly driven by climatic and mineral factors, with finer soil particles attaching greater relative importance in the effect by the mineral factor. The soil carbon decomposition rate (standardized by SOC) was affected by mineral, edaphic, and climatic factors. These findings highlight the importance of considering the differential influences by minerals in different soil aggregate carbon fractions, particularly the silt- and clay-associated carbon in the Earth system models, so as to improve the accuracy in the prediction of SOC dynamics in grassland ecosystems under changing environment.

Key words: soil organic carbon, carbon fractions, carbon decomposition, mineral, temperate grasslands

陈颖洁, 房凯, 秦书琪, 郭彦军, 杨元合. 内蒙古温带草地土壤有机碳组分含量和分解速率的空间格局及其影响因素. 植物生态学报, 2023, 47(9): 1245-1255. DOI: 10.17521/cjpe.2023.0028

CHEN Ying-Jie, FANG Kai, QIN Shu-Qi, GUO Yan-Jun, YANG Yuan-He. Spatial patterns and determinants of soil organic carbon component contents and decomposition rate in temperate grasslands of Nei Mongol, China. Chinese Journal of Plant Ecology, 2023, 47(9): 1245-1255. DOI: 10.17521/cjpe.2023.0028

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2023.0028

https://www.plant-ecology.com/CN/Y2023/V47/I9/1245

图/表 5

图1 内蒙古温带草地土壤有机碳含量(A)及碳组分含量(B-D)的空间格局。植被类型图基于1:1 000 000中国植被图(中国科学院中国植被图编辑委员会, 2001)绘制。箱线图中的线、底边和顶边以及误差棒分别表示一组数据的中位值、25百分位数和75百分位数以及标准差。不同小写字母表示不同草地类型存在显著差异(p < 0.05)。

Fig. 1 Spatial distributions of total soil organic carbon (C) content (A) and in three fractions content (B-D) in temperate grasslands of Nei Mongol. The vegetation map was obtained from China’s vegetation atlas with a scale of 1:1 000 000 (The Editorial Committee of Vegetation Map of China, Chinese Academy of Sciences, 2001). The lines, lower and upper boundaries, and bars in the boxes show median values, 25th and 75th percentiles, and standard deviations of all data, respectively. Different lowercase letters denote significant differences among different grassland types (p < 0.05). DS, desert steppe; MS, meadow steppe; TS, typical steppe.

图2 内蒙古温带草地有机碳(OC)标准化碳分解速率的空间格局(A)及不同草地类型间土壤碳分解速率的差异(B)。植被类型图基于1:1 000 000中国植被图(中国科学院中国植被图编辑委员会, 2001)绘制。箱线图中的线、底边和顶边以及误差棒分别表示一组数据的中位值、25百分位数和75百分位数以及标准差。不同小写字母表示不同草地类型存在显著差异(p < 0.05)。

Fig. 2 Spatial distribution of soil carbon (C) decomposition rate standardized by soil organic C (OC) in temperate grasslands of Nei Mongol (A), and comparison of soil C decomposition rate among different grassland types (B). The vegetation map was obtained from China’s vegetation atlas with a scale of 1:1 000 000 (The Editorial Committee of Vegetation Map of China, Chinese Academy of Sciences, 2001). The lines, lower and upper boundaries, and bars in the boxes show median values, 25th and 75th percentiles, and standard deviations of all data, respectively. Different lowercase letters denote significant differences among different grassland types (p < 0.05). DS, desert steppe; MS, meadow steppe; TS, typical steppe.

图3 内蒙古温带草地不同碳组分有机碳含量的差异。箱线图中的线、底边和顶边以及误差棒分别表示一组数据的中位值、25百分位数和75百分位数以及标准差。不同小写字母表示不同草地类型碳组分存在显著差异(p < 0.05)。

Fig. 3 Comparison of organic carbon (C) contents among different soil aggregate fractions in temperate grasslands of Nei Mongol. The lines, lower and upper boundaries, and bars in the boxes show median values, 25th and 75th percentiles, and standard deviations of all data, respectively. Different lowercase letters denote significant differences of C fractions among different grassland types (p < 0.05).

图4 内蒙古温带草地土壤有机碳含量、碳组分含量、碳分解速率与气候、土壤、植物和矿物变量的相关性。土壤有机碳、大团聚体碳、微团聚体碳、粉粒黏粒碳含量和有机碳标准化的碳分解速率数据经过了lg转化。括号中的“+”和“-”分别代表正相关关系和负相关关系。AGB, 地上生物量; AI, 干旱指数; CaExch, 交换性钙; Clay + silt, 黏粒和粉粒含量; Feo + Alo, 弱结晶态铁铝氧化物; Fep + Alp, 有机络合态铁铝氧化物; MAP, 年降水量; MAT, 年平均气温。*, p < 0.05; **, p < 0.01; ***, p < 0.001。

Fig. 4 Correlations of total soil organic carbon (C) content, C content in different aggregate fractions and C decomposition rate with climatic, edaphic, plant and mineral variables in temperate grasslands of Nei Mongol. Soil organic C, macroaggregate C, microaggregate C, silt and clay C, and C decomposition rate standardized by SOC are lg transformed. The “+” and “-” in parentheses represent positive and negative correlations, respectively. AGB, aboveground biomass; AI, aridity index; CaExch, exchangeable Ca2+; Clay + silt, clay and silt content; Feo + Alo, poorly crystalline Fe/Al oxide; Fep + Alp, organically complexed Fe/Al oxide; MAP, mean annual precipitation; MAT, mean annual air temperature. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

图5 气候、土壤、植物和矿物变量对内蒙古温带草地土壤有机碳含量(A)、碳组分含量(B-D)和碳分解速率(E)影响的相对重要性。土壤有机碳、大团聚体碳、微团聚体碳、粉粒黏粒碳含量和有机碳标准化的碳分解速率数据经过了lg转化。AGB, 地上生物量; AI, 干旱指数; CaExch, 交换性钙含量; Clay + silt, 黏粒和粉粒含量; Feo + Alo, 弱结晶态铁铝氧化物含量; MAP, 年降水量; MAT, 年平均气温。

Fig. 5 Relative effects of climatic, edaphic, plant and mineral variables on soil organic carbon (C) content (A), aggregate C fractions content (B-D), and C decomposition rate (E) in temperate grasslands of Nei Mongol. Soil organic C, macroaggregate C, microaggregate C, silt and clay C contents, and C decomposition rate standardized by SOC are lg transformed. AGB, aboveground biomass; AI, aridity index; CaExch, exchangeable Ca2+ content; Clay + silt, clay and silt content; Feo + Alo, poorly crystalline Fe/Al oxide content; MAP, mean annual precipitation; MAT, mean annual air temperature.

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