Warming Reduces Priming Effect of Soil Organic Carbon Decomposition Along a Subtropical Elevation Gradient

• Published in: Global biogeochemical cycles Vol. 38; no. 6
• Main Authors: Li, Xiaojie, Lyu, Maokui, Zhang, Qiufang, Feng, Jiguang, Liu, Xiaofei, Zhu, Biao, Wang, Xiaohong, Yang, Yusheng, Xie, Jinsheng
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-06-2024
• Subjects: 13C‐PLFA; Annual temperatures; Bioavailability; Biomass; Carbon; Carbon 13; Climate change; Climate prediction; Components; Decomposition; Ecosystems; Global warming; Glucose; Lignin; Microorganisms; Mining; Nitrogen; Organic carbon; Organic soils; Priming; priming effects; Soil; Soil temperature; Soils; substrate quality; Substrates; temperature gradient; Temperature rise; Terrestrial ecosystems; Vegetation; warming
• ISSN: 0886-6236; 1944-9224
• DOI: 10.1029/2024GB008113

The priming effects (PEs) of soil organic carbon (SOC) decomposition is a crucial process affecting the C balance of terrestrial ecosystems. However, there is uncertainty about how PEs will respond to climate warming. In this study, we sampled soils along a subtropical elevation gradient in China and conducted a 126‐day lab‐incubation experiment with and without the addition of 13C‐labeled high‐bioavailability glucose or low‐bioavailability lignin. Based on the mean annual temperature (MAT) of each elevation (9.3–16.4°C), a temperature increase of 4°C was used to explore how PEs mediate the decomposition of SOC in response to warming. Our results showed that the magnitude of glucose‐induced PEs (PEglucose) was higher than lignin‐induced PEs (PElignin), with both PEs linearly increasing with MAT. Across the MAT (i.e., elevation) gradient, short‐term warming had a constant magnitude of negative effects on PEglucose, whereas rising MAT exacerbated the negative effects of short‐term warming on PElignin. Moreover, the temperature sensitivity of SOC decomposition decreased after adding glucose and lignin across the MAT gradient, suggesting that fresh C inputs may prime the microbial breakdown of labile SOC under warming. Taken together, warming alleviated SOC loss due to PEs through varying mechanisms depending on substrate bioavailability. Warming mediated the PEglucose by increasing available nitrogen and weakening microbial nitrogen‐mining but inhibited the PElignin by shifting from microbial nitrogen‐mining to microbial co‐metabolization. Our findings highlight the role of warming in regulating the PEs and suggest that incorporating the suppression effect of warming on PEs can contribute to the accurate prediction of soil C dynamics in a warming world.
Plain Language Summary
Tropical and subtropical ecosystems have the highest vegetation productivity and diversity on earth and play a crucial role in regulating climate change. However, it is unclear how diverse plant‐derived components stimulate microbial decomposition of soil organic carbon (SOC) via a phenomenon called priming effects (PEs) under climate warming. Here, we added two 13C‐labeled substitutions of plant components (e.g., glucose and lignin) to soils collected from a subtropical elevation gradient and carried out a 126‐day lab‐incubation experiment. Warming consistently harmed glucose‐induced PEs (PEglucose), while amplified the negative effect on lignin‐induced PEs (PElignin) across the elevation gradient, suggesting that warming has stronger negative effects on PElignin at warmer sites. Warming mediates the PEglucose by weakening microbial N‐mining but strengthening microbial preferential substrate utilization. This is achieved by reducing substrate‐built microbial biomass and making more substrate for respiration compared to unwarmed soil. In contrast, warming inhibits lignin‐induced PEs by shifting from microbial N‐mining to microbial co‐metabolization. This shift is supported by the positive association between lignin‐induced PEs and lignin‐derived microbial biomass and available nitrogen. Our measurement suggests that warming decreased the intensity of SOC decomposition by downregulating the primed SOC loss with fresh substrate inputs through varying mechanisms depending on substrate bioavailability.
Key Points
Soil C priming effect linearly decreases with elevation in subtropics
High‐ and low‐quality substrates play opposite but complementary roles in soil C feedback to climate warming
The suppression effect of warming on priming can contribute to the accurate prediction of soil C dynamics in a warmer world