Periodic Reporting for period 5 - ECOHERB (Drivers and impacts of invertebrate herbivores across forest ecosystems globally.)
Période du rapport: 2021-12-01 au 2023-02-28
Forests currently slow global climate change by absorbing large amounts of atmospheric carbon dioxide. However, the future of this carbon sink is critically limited by the availability of nutrients important for plant growth. Therefore, to understand the pattern of future climate change, it is first necessary to understand the factors regulating forest nutrient cycling. Herbivores potentially alter forest nutrient cycling in a range of ways, but these have mostly only been recorded for various species of large mammals. By comparison, the impacts of the abundant invertebrates in forests have largely been ignored.
The project applied a pioneering new approach with the overall objective of providing the most complete picture yet available of the rates, underlying drivers and ultimate impacts of nitrogen and phosphorus inputs from invertebrate herbivores across forest ecosystems worldwide. Specifically, we established a network of ~70 field sites across all major forest types to provide the first coordinated global assessment of the rates and regulators of herbivore nutrient transfers globally. The specific questions addressed were:
1) How large are herbivore inputs of nitrogen and phosphorus to the soil in different forest types and compared to other major ecosystem sources?
2) How does climate and habitat disturbance affect herbivore nutrient fluxes?
3) How do herbivore nutrient fluxes change soil processes and how does this vary with climate?
4) How do herbivores shape forest responses to climate and what will this mean for future patterns of forest carbon sequestration?
From this work we have reached the following broad conclusions. First, release of relatively small quantities of nutrients from herbivory by insects at low densities could affect long-term ecosystem biogeochemistry as much or more than episodic outbreak events. Secondly, climate change in broadleaf forests can have important but variable impacts on both forest productivity and and insect herbivory rates, with major consequences for ecosystem processes, but the magnitude and direction of these impacts will depend on the climate variable, foliar element and spatio-temporal scale under consideration. Finally, ecosystem models should include a more detailed representation of herbivory to accurately project current and likely future patterns of biogeochemical cycling.
The project applied a pioneering new approach with the overall objective of providing the most complete picture yet available of the rates, underlying drivers and ultimate impacts of nitrogen and phosphorus inputs from invertebrate herbivores across forest ecosystems worldwide. Specifically, we established a network of ~70 field sites across all major forest types to provide the first coordinated global assessment of the rates and regulators of herbivore nutrient transfers globally. The specific questions addressed were:
1) How large are herbivore inputs of nitrogen and phosphorus to the soil in different forest types and compared to other major ecosystem sources?
2) How does climate and habitat disturbance affect herbivore nutrient fluxes?
3) How do herbivore nutrient fluxes change soil processes and how does this vary with climate?
4) How do herbivores shape forest responses to climate and what will this mean for future patterns of forest carbon sequestration?
From this work we have reached the following broad conclusions. First, release of relatively small quantities of nutrients from herbivory by insects at low densities could affect long-term ecosystem biogeochemistry as much or more than episodic outbreak events. Secondly, climate change in broadleaf forests can have important but variable impacts on both forest productivity and and insect herbivory rates, with major consequences for ecosystem processes, but the magnitude and direction of these impacts will depend on the climate variable, foliar element and spatio-temporal scale under consideration. Finally, ecosystem models should include a more detailed representation of herbivory to accurately project current and likely future patterns of biogeochemical cycling.
The project work involved establishing and coordinating field monitoring across ~70 field sites on all continents except Antarctica, across most major natural environmental gradients and several globally renowned existing experiments. The technology involved in the work has been relatively simple and well established, this has been critical to the logistical and technical achievement of the network by ensuring that the methods could be applied consistently and repeatably in many different situations across all of the field sites. At each site, data on leaf level herbivory, site climate, soil properties, plant productivity and chemistry were collected. These data were collated and analyzed to estimate rates of, and controls over, herbivore mediated nutrients fluxes in broadleaf forests at a global scale.
Broadly the data show that (1) Release of relatively small quantities of nutrients from herbivory by insects at low densities could affect long-term ecosystem biogeochemistry as much or more than episodic outbreak events; (2) Secondly, climate change in broadleaf forests can have important but variable impacts on both forest productivity and and insect herbivory rates, with major consequences for ecosystem processes, but the magnitude and direction of these impacts will depend on the climate variable, foliar element and spatio-temporal scale under consideration and; (3) Ecosystem models should include a more detailed representation of herbivory to accurately project current and likely future patterns of biogeochemical cycling.
These results have been disseminated widely via a wide range of outlets including multiple articles in international peer reviewed scientific journals, presentations at scientific conferences, and various publications and interviews in national and international media targeting the general public
Broadly the data show that (1) Release of relatively small quantities of nutrients from herbivory by insects at low densities could affect long-term ecosystem biogeochemistry as much or more than episodic outbreak events; (2) Secondly, climate change in broadleaf forests can have important but variable impacts on both forest productivity and and insect herbivory rates, with major consequences for ecosystem processes, but the magnitude and direction of these impacts will depend on the climate variable, foliar element and spatio-temporal scale under consideration and; (3) Ecosystem models should include a more detailed representation of herbivory to accurately project current and likely future patterns of biogeochemical cycling.
These results have been disseminated widely via a wide range of outlets including multiple articles in international peer reviewed scientific journals, presentations at scientific conferences, and various publications and interviews in national and international media targeting the general public
The large existing body of research about herbivores reflects (1) a focus on large bodied animal herbivores, (2) where invertebrate herbivores are studied, a focus on (i) outbreaks, (ii) impacts in temperate ecosystems and/or (iii) links between leaf-level damage and traits.
The present project made a wide range of breakthroughs, most of them linked to the basic novelty of looking at nutrient and carbon fluxes arising from background rates of invertebrate herbivory across all major forest types and under various major forest disturbances. The work has bridged several major fields within ecology – linking plant ecology, soil science and zoology – to illustrate how all of these distinct disciplines need to be included and combined to develop an accurate predictive understanding of real ecosystems. Further, we have made majors steps towards integrating this new ecological knowledge with modelling efforts that are based within physical, mathematical and computer sciences.
The present project made a wide range of breakthroughs, most of them linked to the basic novelty of looking at nutrient and carbon fluxes arising from background rates of invertebrate herbivory across all major forest types and under various major forest disturbances. The work has bridged several major fields within ecology – linking plant ecology, soil science and zoology – to illustrate how all of these distinct disciplines need to be included and combined to develop an accurate predictive understanding of real ecosystems. Further, we have made majors steps towards integrating this new ecological knowledge with modelling efforts that are based within physical, mathematical and computer sciences.