Potential impacts of climate change on the productivity and soil carbon stocks of managed grasslands

PLOS ONE · 7 authors, 5 centres

AI SUMMARY

FIDELITY 97%

POPULATIONManaged grasslands (mowed and rotationally grazed) at Lusignan, southwestern France

INTERVENTIONFuture climate scenarios (RCP 2.6, RCP 4.5, RCP 8.5) and factorial changes in temperature, precipitation, and CO₂ concentration

COMPARISONBaseline historical climate (1975–2005) and simulations without CO₂ fertilization effect

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TL;DR

This modeling study assessed how climate change may affect managed grasslands in France, finding that rising CO₂ levels could boost grass and milk production but would also deplete soil organic carbon stocks, especially under high-emission scenarios. Increased temperatures and extreme weather events (heat waves, droughts) further threaten soil carbon storage and may render some years unsuitable for grazing. The results highlight a trade-off between maintaining agricultural productivity and preserving soil carbon, requiring careful management adjustments.

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**Background:** Grassland ecosystems cover about one-quarter of Earth's land area and store large quantities of soil organic carbon (SOC). They are critical for fiber, meat, and milk production but also contribute to greenhouse gas emissions. Climate change—through rising CO₂, temperature shifts, altered precipitation, and increased extremes—poses significant uncertainty for grassland productivity and carbon storage. Previous work has shown that SOC stocks are sensitive to land use and management, but long-term projections under integrated climate scenarios remain poorly understood. This study aimed to (1) assess the impacts of changes in key meteorological variables on CO₂ fluxes, grassland and milk productivity, and SOC stocks, and (2) simulate the potential influence of long-term future climate scenarios and extreme events on these variables.

**Methods:** The study used the CenW ecosystem model (version 4.2), a process-based model simulating carbon, water, and nitrogen cycles on a daily time step. The site was located in Lusignan, southwestern France (mean temperature 11.2°C, precipitation 774 mm yr⁻¹). Two management systems were modeled: a mowed paddock (receiving >320 kg N ha⁻¹ yr⁻¹, 3–4 cuts per year) and a rotationally grazed paddock (receiving <50 kg N ha⁻¹ yr⁻¹, grazed 7.4 times per year, stocking rate 17 heads ha⁻¹). The model was previously calibrated and validated using eddy covariance data (2006–2010). Sensitivity analyses tested individual changes: temperature (−4°C to +4°C), precipitation (−25% to +25%), and CO₂ (−15% to +780 ppm). Long-term simulations used three RCP scenarios (RCP 2.6, RCP 4.5, RCP 8.5) from the CNRM2014 experiment, covering 1975–2100 divided into four periods: Historical (H: 1975–2005), Near Future (NF: 2006–2036), Intermediate Future (IF: 2037–2067), and Far Future (FF: 2068–2100). Six ETCCDI extreme climate indices were analyzed: number of hot days (NHD), TX90p, warm spell duration index (WSDI), maximum length of dry spell (MLDS), R95pTOT, and prcpTOT.

**Key Results:** Under factorial changes, increasing temperature slightly increased GPP, NPP, and milk production but strongly reduced SOC (e.g., −16% under +4°C for grazed). Reduced precipitation (−25%) decreased GPP by −14%, milk production by −28%, and NPP by −11%, but SOC increased slightly (+2%). Doubling CO₂ (to 780 ppm) increased GPP by +27%, NPP by +25%, milk production by +91%, and N fertilizer requirements by +65%, while SOC decreased marginally (−1%). Under RCP scenarios with increasing CO₂, GPP in FF increased by 11% (RCP 2.6), 14% (RCP 4.5), and 28% (RCP 8.5) relative to H. Milk production in FF increased by 104% under RCP 8.5. SOC decreased under all scenarios: −2% (RCP 2.6 and RCP 4.5) and −5% (RCP 8.5) in FF. Without CO₂ fertilization (constant 380 ppm), SOC losses were twice as large: −5% (RCP 2.6), −6% (RCP 4.5), and −13% (RCP 8.5) in FF. Extreme indices showed NHD increasing by 160% under RCP 8.5 in FF (from 36 to 93 days), and WSDI increasing from 8 days (H) to 90 days (RCP 8.5, FF). Correlations between extreme indices and modeled variables intensified under RCP 8.5, with CO₂ fertilization mitigating negative impacts of temperature extremes on productivity.

**Clinical Implications:** The study demonstrates that while climate change—particularly CO₂ fertilization—may boost grassland productivity and milk yields, it simultaneously drives SOC losses, especially under high-emission scenarios. Maintaining productivity requires substantially higher nitrogen fertilizer inputs (e.g., +53% under RCP 8.5 in FF), which carries environmental costs (leaching, N₂O emissions). Under RCP 8.5, extreme heat and drought may render some years unsuitable for milk production. The findings underscore a fundamental trade-off: targeting productivity likely accelerates soil carbon loss, and SOC stocks can only be increased through management changes that reduce carbon exports (e.g., grazing intensity, harvest frequency). For clinicians and agricultural policymakers, these results highlight the need for adaptive management strategies that balance food production with soil carbon conservation, particularly as extreme events become more frequent.

PICO

PPOPULATION

Managed grasslands (mowed and rotationally grazed) at Lusignan, southwestern France

IINTERVENTION

Future climate scenarios (RCP 2.6, RCP 4.5, RCP 8.5) and factorial changes in temperature, precipitation, and CO₂ concentration

OOUTCOME

Gross primary productivity (GPP), net primary productivity (NPP), milk production, soil organic carbon (SOC) stocks, nitrogen fertilizer requirements, ecosystem respiration (ER)

STUDY TYPE

other

SPECIALTY

endocrinology

SUMMARISED BY

AI pipeline

FIDELITY CHECK

97% · A

ORIGINAL PAPER

PMC10085015

Potential impacts of climate change on the productivity and soil carbon stocks of managed grasslands

PLOS ONE

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ABSTRACT

Abstract Rain-fed pastoral systems are tightly connected to meteorological conditions. It is, therefore, likely that climate change, including changing atmospheric CO 2 concentration, temperature, precipitation and patterns of climate extremes, will greatly affect pastoral systems. However, exact impacts on the productivity and carbon dynamics of these systems are still poorly understood, particularly over longtime scales. The present study assesses the potential effects of future climatic conditions on productivity and soil organic carbon (SOC) stocks of mowed and rotationally grazed grasslands in France. We used the CenW ecosystem model to simulate carbon, water, and nitrogen cycles in response to changes in environmental drivers and management practices. We first evaluated model responses to individual changes in each key meteorological variable to get better insights into the role and importance of each individual variable. Then, we used 3 sets of meteorological variables corresponding to 3 Representative Concentration Pathways (RCP 2.6, RCP 4.5 and RCP 8.5) for long-term model runs from 1975 to 2100. Finally, we used the same three RCPs to analyze the responses of modelled grasslands to extreme climate events. We found that increasing temperature slightly increased grasslands productivities but strongly reduced SOC stocks. A reduction in precipitation led to reductions of biomass and milk production but increased SOC. Conversely, doubling CO 2 concentration strongly increased biomass and milk production and marginally reduced SOC. These SOC trends were unexpected. They arose because both increasing precipitation and CO 2 increased photosynthetic carbon gain, but they had an even greater effect on the proportion of biomass that could be grazed. The amount of carbon remaining on site and able to contribute to SOC formation was actually reduced under both higher precipitation and CO 2 . The simulations under the three RCPs indicated that grassland productivity was increased, but that required higher N fertilizer application rates and also led to substantial SOC losses. We thus conclude that, while milk productivity may continue at current rates under climate change, or even increase slightly, there could be some soil C losses over the 21 st century. In addition, under the highest-emission scenario, the increasing importance of extreme climate conditions (heat waves and droughts) might render conditions at our site in some years as unsuitable for milk production. It highlights the importance of tailoring farming practices to achieve the dual goals of maintaining agricultural production while safeguarding soil C stocks.

CITATION EXPORT

N J B Puche, M U F Kirschbaum, N Viovy et al.. Potential impacts of climate change on the productivity and soil carbon stocks of managed grasslands. PLOS ONE. (2023). https://doi.org/10.1371/journal.pone.0283370

AUTHORS

7 · 5 CENTRES

N J B Puche, M U F Kirschbaum, N Viovy, Abad Chabbi, Jian Liu, Jian Liu, Jian Liu

1UMR ECOSYS Joint research unit INRAE, AgroParisTech, Université Paris-Saclay, Palaiseau Cedex, France
2URP3F, French National Research Institute for Agriculture, Food and Environment (INRAE), Poitou-Charentes, Lusignan, France
3Manaaki Whenua – Landcare Research, Palmerston North, New Zealand
4LSCE/IPSL, CEA-CNRS-UVSQ, Laboratoire des Sciences du Climat et de l’Environnement, Universite Paris-Saclay, Gif-sur-Yvette, Frances
5Shandong University, CHINA