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Response of C:N:P stoichiometry to altered precipitation in terrestrial ecosystems

Update time:2023-10-09

Recently, a team led by Prof. Zhouping Shangguan from the College of Soil and Water Conservation Science and Engineering （Institute of Soil and Water Conservation），Northwest A&F University has made significant progress in understanding the response of C:N:P stoichiometry to altered precipitation in terrestrial ecosystems. Their findings, titled "C:N:P stoichiometry of plants, soils, and microorganisms: Response to altered precipitation" have been published in Global Change Biology (IF2022=11.6). Dr. Jiwei Li, a postdoctoral researcher at the College of Water Resources, is the first author of the paper, and Prof. Lei Deng is the corresponding author.

Climate warming has had a significant impact on global and regional precipitation patterns, leading to changes in the distribution of precipitation seasons and the frequency of extreme precipitation events, thereby affecting the stability of terrestrial ecosystems. Precipitation changes can also alter the cycling of carbon (C), nitrogen (N), and phosphorus (P) in ecosystems, thereby influencing the stability and composition of plant and microbial communities. Plant and microbial communities are highly sensitive to altered precipitation, but the response and sensitivity of the plant-soil-microbe element cycle under altered precipitation are still not clear. Therefore, it is crucial to further study the processes and mechanisms of how different ecosystem C:N:P stoichiometry responds to altered precipitation. This is important for revealing the role of precipitation in the global carbon cycle and understanding the roles of plants and microbes in soil carbon cycling. Based on this, the study has made the following progress using global data points (Figure 1):

Figure 1: Distribution of sampling points in three major vegetation ecosystems (forest, shrubland, grassland).

(1) Elucidated the response of ecosystem C:N:P stoichiometry to altered precipitation. Increased precipitation had a relatively minor impact on the plant-soil-microbe C:N:P in comparison to decreased precipitation, which elevated litter N, root N, leaf, and root N:P ratios (Figure 2). Increased precipitation elevated soil C, N, and C:P, as well as microbial C, N, and P content, whereas decreased precipitation reduced microbial N and N:P. In arid regions (aridity index AI < 0.65), increased precipitation raised microbial C and N content, while in humid regions (AI > 0.65), decreased precipitation increased leaf N and N:P but decreased leaf C:N. Increased precipitation increased the C:P ratio in grassland ecosystems, while decreased precipitation increased leaf N content in forest-grassland ecosystems but decreased leaf C:N ratio.

Figure 2: Response patterns of ecosystem C:N:P to altered precipitation.

(2) Clarified the differential sensitivity of plant and microbial community C:N:P stoichiometry to altered precipitation. Plant communities were more sensitive to decreased precipitation compared to increased precipitation, with a notable sensitivity of plant leaf C:N in response to decreased precipitation, especially under moderate precipitation reduction conditions (-33.3% ~ -66.7%) (Figure 3). Soil microbial communities were more sensitive to increased precipitation than decreased precipitation, exhibiting sensitivity in C, N, P, and C:N to increased precipitation. This sensitivity was further confirmed under slight precipitation increase conditions (< +33.3%), and under extreme precipitation intensities (±67%), soil microbes were more sensitive to decreased precipitation than increased precipitation, showing a "double asymmetrical model" change.

Figure 3：Sensitivity of ecosystem C:N:P to altered precipitation.

(3) Revealed the mechanistic impacts of precipitation changes on the ecosystem C:N:P stoichiometry. Precipitation changes primarily affected N-related stoichiometry (N, C:N, and N:P) of plants, soil, and microbes, indicating that plant and microbial communities involved in N cycling have a significant impact on ecosystem carbon accumulation. Under precipitation changes, soil microbial communities exhibited strong homeostasis, while plant communities tended to change in response to changes in resource efficiency. Additionally, plant C:N:P stoichiometry was primarily influenced by the annual mean precipitation, while microbial C:N:P stoichiometry was mainly influenced by the intensity of precipitation changes (Figure 4). Different N allocation strategies of plant and microbial communities under precipitation changes drove the ecosystem carbon accumulation mediated by C:N:P stoichiometry, providing theoretical references for ecosystem carbon cycling under future climate change scenarios.

Figure 4: Conceptual model of the response of ecosystem C:N:P to changes in precipitation.

This study received funding from various projects, including the National Natural Science Foundation of China (U2243225, 42277471, 42307578).

The link to the paper is as follows: https://onlinelibrary.wiley.com/doi/10.1111/gcb.16959