Author & Address

题目：

Responses of soil C pools to combined warming and altered precipitation regimes: A meta-analysis

(资料图)

通讯作者：

Fuzhong Wu

地址：

Key Laboratory for Humid Subtropical Eco-Geographical Processes of the Ministry of Education, School of Geographical Sciences, Fujian Normal University, Fuzhou, China

Abstract

Aim

全球变暖和降水变化极大地影响土壤碳库，并反过来反馈到气候变化中。然而，土壤碳库如何对变暖和降水改变的综合影响作出反应仍不清楚。

Location

Global.

Time period

1996–2021.

Major taxa studied

Soil organic C pools.

Method

本研究利用34篇文献中的657个观测数据，定量分析了气候变暖和降水变化对土壤有机碳(SOC)、可溶性有机碳(DOC)和微生物生物量碳(MBC)的单独和联合影响。

Results

在所有增温增雨试验中，SOC和MBC分别平均增加了%和%。相反，增温和降水减少导致SOC和MBC的平均降幅分别为%和%。DOC对复合增温和降水变化的响应较为边缘。对联合处理的响应方向和幅度更接近于单独增温处理。此外，这些综合效应在很大程度上受到改变的降水幅度的影响。增温和降水变化联合处理对土壤碳库的影响大于单独处理，但与单独处理的影响之和无显著差异，总体表现为相加效应。土壤碳库对气候变暖和降水变化的响应在草地上比在森林中更明显。

Main conclusion

研究结果表明，在增温和降水变化的联合作用下，降水变化对土壤碳库的调节作用往往优于气候变暖，从而提高了我们对气候变化情景下土壤碳循环的理解。

Result

FIGURE 1

Schematic of dissolved organic carbon (DOC) inputs and microbial biomass carbon (MBC) in the soil system. The blue arrows and text represent the sources of DOC, and the microbes in red represent MBC. The brown blob of matter is soil organic matter (SOM), and the green matter is dissolved organic matter (DOM).

FIGURE 2

Characteristics of the study sites selected for the meta-analysis. (a) Distribution of study sites at the global scale, (b) mean annual temperature and precipitation of study sites, and (c) density observed by soil depth.

FIGURE 3

Conceptual diagram of interaction types. Treatments are hypothetical control, individual warming (W) and individual increased precipitation (IP). The effect of treatment W is the change in response due to W above the baseline effect of the control (W − control), shown in blue. Similarly, the effect of treatment IP is the change in response due to IP above the baseline effect of the control (IP − control), shown in purple. An interaction of combined treatment (W + IP) is additive if the response to the application of both W and IP is the sum of the effects of both treatments above baseline (response = (W + IP) − control). The dashed black line shows this additive prediction. The interaction is synergistic if the response is greater than the sum of the effects of both treatments (response > (W + IP) − control), which is depicted in green. The interaction is antagonistic if the response is less than the sum of the effects of both treatments (response < (W + IP) − control), depicted in yellow.

FIGURE 4

Individual and combined effects of warming and altered precipitation regimes on soil C pools. Effects of warming (W), increased precipitation (IP), combined warming and increased precipitation (W + IP) (top), decreased precipitation (DP), and combined warming and decreased precipitation (W + DP) (bottom) on (a, d) soil organic carbon (SOC), (b, e) dissolved organic carbon (DOC), and (c, f) microbial biomass carbon (MBC) are shown. Results are expressed as the percentage change relative to the control (%). Solid yellow dots indicate the significant positive effects, solid green dots indicate the significant negative effects and solid purple dots indicate the non-significant effects. Values indicate the means with 95% confidence intervals (CIs), and n indicates the number of observations. The vertical dashed lines are zero lines.

FIGURE 5

Interactive effects of warming and altered precipitation regimes on soil C pools. Effects of combined warming and increased precipitation (W + IP) and combined warming and decreased precipitation (W + DP) on (a) soil organic carbon (SOC), (b) dissolved organic carbon (DOC) and (c) microbial biomass carbon (MBC) are revealed using the weighted mean Hedges' d and the corresponding frequency distribution of interaction types among individual observations. Values represent means with 95% confidence intervals (CIs), and the number of observations is given along the y-axis.

FIGURE 6

Individual and interactive effects of warming and altered precipitation among different ecosystem types. Effects of warming (W), increased precipitation (IP), decreased precipitation (DP), combined warming and increased precipitation (W + IP), and combined warming and decreased precipitation (W + DP) on (a, d) soil organic carbon (SOC), (b, e) dissolved organic carbon (DOC) and (c, f) microbial biomass carbon (MBC) are shown. Interactive effects of warming and altered precipitation on (g) soil organic carbon (SOC), (h) dissolved organic carbon (DOC) and (i) microbial biomass carbon (MBC) have been revealed using the weighted mean Hedges' d in different ecosystems. Significant (α < ) Qb (between-group heterogeneity) indicates that the response ratios differ among ecosystems. Values represent means with 95% confidence intervals (CIs), and the number of observations is given along the y-axis. The vertical dashed lines are zero lines.

Conclusion

本研究对了解自然生态系统土壤碳库对气候变化的响应具有重要意义。土壤SOC、DOC和MBC在增温和降水增加的联合作用下呈增加趋势，在增温和降水减少的联合作用下呈降低趋势。结果中观察到的变化可以归因于降水变化，这表明与变暖相比，土壤C库对降水变化的敏感性更大。增温和降水改变对土壤碳库的相加效应以协同或拮抗作用为主，而复合效应可能受气候、土壤因子和试验设置的影响。此外，相对于增温幅度，降水变化幅度对土壤碳库的响应影响较大。在生态系统类型上，草地土壤C库对复合增温和降水变化的敏感性高于森林。本研究揭示了全球气候变化下降水变化对土壤碳循环的重要调控作用。

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