Effects of precipitation changes on the soil organic carbon distribution and stability of organic carbon pool in desert steppe

doi:10.11686/cyxb2025230

Abstract

Abstract:

The aims of this work were to investigate the regulatory mechanisms of soil organic carbon （SOC） dynamics in a desert steppe ecosystem， and to determine how they are affected by changes in precipitation. This is critical for advancing our understanding of carbon （C） cycling processes and stabilization mechanisms in vulnerable arid environments. A field experiment was conducted in the desert steppe in Yanchi County， Ningxia. A gradient of five precipitation levels was simulated by rain shelter technology； namely 33%， 66%， 100%， 133%， and 166% of normal rainfall （designated as P₃₃， P₆₆， P_CK， P₁₃₃， and P₁₆₆， respectively）. The distribution pattern of SOC and the stability of the C pool under different precipitation changes in the desert steppe were analyzed， and the mechanisms by which changes in precipitation affected the stability of the soil C pool were explored. The results showed that： 1） Under all precipitation treatments， the contents of SOC， soil dissolved organic C （DOC）， and soil microbial biomass C （MBC） decreased with increasing soil depth， and all these parameters had the highest values in the surface layer （0-10 cm）. In the same soil layer， water addition significantly increased SOC， the easily oxidized soil organic C （EOC） content， and MBC content， while the DOC content increased significantly under reduced precipitation treatments. 2） The stability index of the soil C pool showed that increased precipitation treatments significantly increased the carbon pool activity （CA） and carbon pool management index （CPMI）. The CPMI of the P₁₃₃ treatment reached 192.49%， indicating that a moderate increase in precipitation could enhance the stability of the C pool. 3） Pearson’s correlation analysis and structural equation modeling （SEM） showed that precipitation affected the active SOC components through soil moisture and soil enzyme activity， which in turn affected CPMI； the effect of DOC on CPMI was the main pathway. Therefore， increased precipitation can effectively enhance the active SOC components and CPMI of soil in the desert steppe. Notably， active SOC was highly sensitive to variations in precipitation， so it can serve as an indicator of the effect of changes in precipitation on the stability of the soil C pool in the desert steppe.

Key words: desert steppe, precipitation change, soil organic carbon components, carbon pool stability

Jia-li LIAN, Jing CHEN, Xue-qing YANG, Ying ZHAO, Xu LUO, Cui HAN, Jian-ping LI. Effects of precipitation changes on the soil organic carbon distribution and stability of organic carbon pool in desert steppe[J]. Acta Prataculturae Sinica, 2026, 35(5): 85-98.

Figures/Tables 8

Fig.1 Profile of the study area

Fig.2 Temporal variations of soil temperature and soil moisture under the change of precipitation

Table 1 Soil physical and chemical properties after 6 years of precipitation treatment （2018-2023） in the study area （g·kg-1）

处理 Treatment	土壤有机碳 Soil organic carbon	土壤全氮 Soil total nitrogen	土壤全磷 Soil total phosphorus
P₃₃	1.64±0.47b	0.16±0.05b	0.21±0.04a
P₆₆	1.87±0.61b	0.20±0.06b	0.22±0.03a
P_CK	2.51±1.02ab	0.26±0.13ab	0.24±0.04a
P₁₃₃	2.14±0.63b	0.20±0.07b	0.23±0.02a
P₁₆₆	3.08±1.36a	0.33±0.18a	0.25±0.05a

Fig.3 The content of organic carbon and its components in each soil layer under the change of precipitation

Table 2 Soil carbon pool management index under the change of precipitation

处理 Treatment	土壤碳库活度 Carbon pool activity （CA）	碳库活度指数 Carbon pool activity index （CAI）	碳库指数 Carbon pool index （CPI）	碳库管理指数 Carbon pool management index （CPMI， %）
P₃₃	0.30±0.06b	0.66±0.32c	0.72±0.25b	49.90±35.37b
P₆₆	0.32±0.14b	0.62±0.21c	0.83±0.31ab	53.84±34.55b
P_CK	0.54±0.24b	1.00±0.00bc	1.00±0.00ab	100.00±0.00b
P₁₃₃	2.19±2.05a	2.88±2.32a	0.88±0.33ab	192.49±96.53a
P₁₆₆	0.93±0.58b	2.05±1.99ab	1.36±0.74a	190.07±157.09a

Fig.4 Changes in soil enzyme activity with each soil layer under the change of precipitation change

Fig.5 Correlation analysis between soil physical and chemical properties， soil enzymes， soil organic carbon components and soil carbon pool stability

Fig.6 The structural equation model analysis （SEM） and standardized total effect for the effects of precipitation change on the carbon pool management index

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