Grazing and aridity reduce perennial grass abundance in semi-arid rangelands – Insights from a trait-based dynamic vegetation model

Pfeiffer, Mirjam; Langan, Liam; Linstädter, Anja; Martens, Carola; Gaillard, Camille; Ruppert, Jan C.; Higgins, Steven I.; Mudongo, Edwin I.; Scheiter, Simon

doi:10.1016/j.ecolmodel.2018.12.013

Cited by 47 publications

(57 citation statements)

References 65 publications

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“…Lags between transient and equilibrium coverage of different vegetation types or biome types imply debt or surplus in tree cover (Jones et al, 2009), carbon storage, biogeochemical fluxes and community composition (Bertrand et al, 2016). These lags commit ecosystems to further changes even if the rate of climate change is reduced and the climate system converges towards an equilibrium state (Jones et al, 2009;Port et al, 2012;Pugh et al, 2018). This finding has important implications for the development of adaptation and mitigation strategies for climate change.…”

Section: Implications For Adaptation Mitigation and Policymentioning

confidence: 99%

“…Jones et al (2009) used such a fully coupled model to investigate lags in Amazon forest dieback, but feedbacks to the climate system were not explicitly considered. Port et al (2012) used the fully coupled MPI ESM to show that lagged responses of vegetation may, in a scenario where CO 2 emissions are zero after 2120, reduce atmospheric CO 2 by approximately 40 ppm until 2300. Another well-studied example is the Sahel greening phenomenon where smooth changes in rainfall regimes trigger abrupt and delayed responses in vegetation cover due to vegetation-atmosphere feedbacks (Brovkin et al, 1998;Claussen et al, 1999;Foley et al, 2003).…”

Section: Further Lags In the Climate-vegetation Systemmentioning

confidence: 99%

“…Rather, forcing lags emerge where the transient vegetation state lags behind rates of change of environmental drivers (Bertrand et al, 2016). Quantifying these lags is crucial for our understanding of ecosystem dynamics because they imply that the observed vegetation state does not fully reflect prevailing environmental conditions and that ecosystems are committed to further changes even if environmental conditions stabilize (Jones et al, 2009;Port et al, 2012). We expect that the size of the lag between equilibrium and transient vegetation states will be influenced by actual values of environmental conditions, the rate at which they change, and the plant community composition and community-specific ecological processes.…”

Section: Introductionmentioning

confidence: 99%

“…It has been argued that lag effects need to be taken into account when we aim at forecasting future changes in the biosphere and at developing management or mitigation strategies (Svenning and Sandel, 2013;Bertrand et al, 2016). Lag effects imply that vegetation features such as carbon stocks or tree cover are committed to changes that will be ongoing even if anthropogenic emissions of greenhouse gasses level off and the climate system stabilizes (Jones et al, 2009;Port et al, 2012;Huntingford et al, 2013;Pugh et al, 2018). Yet, previous studies often focused on CO 2 levels predicted for 2100, assuming that both CO 2 and the climate system will have stabilized by then.…”

Section: Introductionmentioning

confidence: 99%

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African biomes are most sensitive to changes in CO2 under recent and near-future CO2 conditions

et al. 2020

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Abstract. Current rates of climate and atmospheric change are likely higher than during the last millions of years. Even higher rates of change are projected in CMIP5 climate model ensemble runs for some Representative Concentration Pathway (RCP) scenarios. The speed of ecological processes such as leaf physiology, demography or migration can differ from the speed of changes in environmental conditions. Such mismatches imply lags between the actual vegetation state and the vegetation state expected under prevailing environmental conditions. Here, we used a dynamic vegetation model, the adaptive Dynamic Global Vegetation Model (aDGVM), to study lags between actual and expected vegetation in Africa under a changing atmospheric CO2 mixing ratio. We hypothesized that lag size increases with a more rapidly changing CO2 mixing ratio as opposed to slower changes in CO2 and that disturbance by fire further increases lag size. Our model results confirm these hypotheses, revealing lags between vegetation state and environmental conditions and enhanced lags in fire-driven systems. Biome states, carbon stored in vegetation and tree cover in Africa are most sensitive to changes in CO2 under recent and near-future levels. When averaged across all biomes and simulations with and without fire, times to reach an equilibrium vegetation state increase from approximately 242 years for 200 ppm to 898 years for 1000 ppm. These results have important implications for vegetation modellers and for policy making. Lag effects imply that vegetation will undergo substantial changes in distribution patterns, structure and carbon sequestration even if emissions of fossils fuels and other greenhouse gasses are reduced and the climate system stabilizes. We conclude that modelers need to account for lag effects in models and in data used for model testing. Policy makers need to consider lagged responses and committed changes in the biosphere when developing adaptation and mitigation strategies.

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Section: Implications For Adaptation Mitigation and Policymentioning

confidence: 99%

Section: Further Lags In the Climate-vegetation Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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African biomes are most sensitive to changes in CO2 under recent and near-future CO2 conditions

et al. 2020

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“…Suitable management intervention can oppose CO 2 fertilization effects and delay undesired vegetation changes (Scheiter and Savadogo, 2016). For instance, the introduction of fire can increase lags between transient and equilibrium vegetation states, whereas fire suppression for example by grazing (Pfeiffer et al, 2019) or fire management (Scheiter et al, 2015) can reduce disturbance-related lags. Other disturbances or land use activities such as herbivory or fuelwood harvesting have similar effects (Scheiter and Savadogo, 2016 (Veldman et al, 2015;Bond et al, 2019).…”

Section: Implications For Adaptation Mitigation and Policymentioning

confidence: 99%

African biomes are most sensitive to changes in CO2 under recent and near-future CO2 conditions

Scheiter¹,

Moncrieff²,

Pfeiffer³

et al. 2019

Preprint

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Abstract. Current rates of climate and atmospheric change are likely higher than during the last millions of years. Even higher rates of change are projected in CMIP5 climate model ensemble runs for some RCP scenarios. Mismatches between the speed of ecological processes such as physiological adaptation, demographic shifts or migration, and the speed of changes in en- vironmental conditions imply lags between the transient vegetation state and the vegetation state expected under prevailing environmental conditions. Here, we used a dynamic vegetation model, the aDGVM, to study lags between transient and committed vegetation in Africa under changing atmospheric CO2 mixing ratio. We hypothesized that lag size increases with more rapidly changing CO2 mixing ratio as opposed to slower changes in CO2, and that disturbance by fire further increases these lags. Our model results confirm these hypotheses, revealing lags between vegetation state and environmental conditions and enhanced lags in fire-driven systems. Biome states, carbon stored in vegetation and tree cover in Africa are most sensitive to changes in the CO2 mixing ratio under recent and near-future levels, between approximately 300 and 500&#8201;ppm. These results have important implications for vegetation modellers as well as for management and policy making. Lag effects implicate that vegetation will undergo substantial changes in distribution patterns, structure and carbon sequestration even if emissions of fossils fuels and other greenhouse gasses are reduced and the climate system stabilizes. We conclude that modelers need to account for lags in models and data used for model testing and that policy makers need to consider lagged responses and committed changes in the biosphere when developing adaptation and mitigation strategies.

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Browsing herbivores improve the state and functioning of savannas: A model assessment of alternative land‐use strategies

Irob

Blaum

Baldauf

et al. 2022

Ecology and Evolution

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Changing climatic conditions and unsustainable land use are major threats to savannas worldwide. Historically, many African savannas were used intensively for livestock grazing, which contributed to widespread patterns of bush encroachment across savanna systems. To reverse bush encroachment, it has been proposed to change the cattle‐dominated land use to one dominated by comparatively specialized browsers and usually native herbivores. However, the consequences for ecosystem properties and processes remain largely unclear. We used the ecohydrological, spatially explicit model EcoHyD to assess the impacts of two contrasting, herbivore land‐use strategies on a Namibian savanna: grazer‐ versus browser‐dominated herbivore communities. We varied the densities of grazers and browsers and determined the resulting composition and diversity of the plant community, total vegetation cover, soil moisture, and water use by plants. Our results showed that plant types that are less palatable to herbivores were best adapted to grazing or browsing animals in all simulated densities. Also, plant types that had a competitive advantage under limited water availability were among the dominant ones irrespective of land‐use scenario. Overall, the results were in line with our expectations: under high grazer densities, we found heavy bush encroachment and the loss of the perennial grass matrix. Importantly, regardless of the density of browsers, grass cover and plant functional diversity were significantly higher in browsing scenarios. Browsing herbivores increased grass cover, and the higher total cover in turn improved water uptake by plants overall. We concluded that, in contrast to grazing‐dominated land‐use strategies, land‐use strategies dominated by browsing herbivores, even at high herbivore densities, sustain diverse vegetation communities with high cover of perennial grasses, resulting in lower erosion risk and bolstering ecosystem services.

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Grazing and aridity reduce perennial grass abundance in semi-arid rangelands – Insights from a trait-based dynamic vegetation model

Cited by 47 publications

References 65 publications

African biomes are most sensitive to changes in CO<sub>2</sub> under recent and near-future CO<sub>2</sub> conditions

African biomes are most sensitive to changes in CO<sub>2</sub> under recent and near-future CO<sub>2</sub> conditions

African biomes are most sensitive to changes in CO<sub>2</sub> under recent and near-future CO<sub>2</sub> conditions

Browsing herbivores improve the state and functioning of savannas: A model assessment of alternative land‐use strategies

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Grazing and aridity reduce perennial grass abundance in semi-arid rangelands – Insights from a trait-based dynamic vegetation model

Cited by 47 publications

References 65 publications

African biomes are most sensitive to changes in CO&lt;sub&gt;2&lt;/sub&gt; under recent and near-future CO&lt;sub&gt;2&lt;/sub&gt; conditions

African biomes are most sensitive to changes in CO&lt;sub&gt;2&lt;/sub&gt; under recent and near-future CO&lt;sub&gt;2&lt;/sub&gt; conditions

African biomes are most sensitive to changes in CO&lt;sub&gt;2&lt;/sub&gt; under recent and near-future CO&lt;sub&gt;2&lt;/sub&gt; conditions

Browsing herbivores improve the state and functioning of savannas: A model assessment of alternative land‐use strategies

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Product

Resources

About

African biomes are most sensitive to changes in CO<sub>2</sub> under recent and near-future CO<sub>2</sub> conditions

African biomes are most sensitive to changes in CO<sub>2</sub> under recent and near-future CO<sub>2</sub> conditions

African biomes are most sensitive to changes in CO<sub>2</sub> under recent and near-future CO<sub>2</sub> conditions