15 research outputs found
The fate of carbon in a mature forest under carbon dioxide enrichment
Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth1 5, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration6. Although evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth3 5, it is unclear whether mature forests respond to eCO2 in a similar way. In mature trees and forest stands7 10, photosynthetic uptake has been found to increase under eCO2 without any apparent accompanying growth response, leaving the fate of additional carbon fixed under eCO2 unclear4,5,7 11. Here using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responded to four years of eCO2 exposure. We show that, although the eCO2 treatment of +150 parts per million (+38 per cent) above ambient levels induced a 12 per cent (+247 grams of carbon per square metre per year) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone accounting for half of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO2, and challenge the efficacy of climate mitigation strategies that rely on ubiquitous CO2 fertilization as a driver of increased carbon sinks in global forests. © 2020, The Author(s), under exclusive licence to Springer Nature Limited
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Responses of nematode abundances to increased and reduced rainfall under field conditions: A meta-analysis
Ecosystems are projected to experience altered precipitation patterns associated with climate change, with some areas becoming wetter and others drier. Both above- and belowground communities will be impacted by such rainfall changes, yet research has predominantly focused on the flora and fauna aboveground. Still, there is a growing body of literature for the effects of altered precipitation on soil fauna. Nematodes are diverse and abundant in most soils, represent multiple trophic levels, and influence essential soil processes, making this group a good proxy for broader impacts on soil food webs. Hence, we assessed the effects of increased and reduced rainfall amount on total and trophic-level abundances of nematodes using a meta-analytical approach based on 46 independent observations from 37 field studies and tested whether effects differed among ecosystem types and with treatment duration (1 year, long term). Overall, total and trophic group's abundances, except fungal feeders, were negatively impacted by reduced rainfall irrespectively of treatment duration. Increased rainfall had a positive effect on total abundances and plant parasitic nematodes, but only in longer term studies (>1 year). The impacts of altered rainfall were consistent across the ecosystems studied; however, most studies focus on grasslands and deserts, making it difficult to draw broad generalizations. Reductions in rainfall are therefore likely to decrease soil nematode abundance, with less pronounced effects on fungal feeders. Increased rainfall, on the other hand, may favor plant parasites, likely due to increased plant productivity. Hence, projections of reduced rainfall will have significant negative impacts on nematode abundances, at least in grasslands and deserts, with cascading effects on soil processes. © 2023 The Authors. Ecosphere published by Wiley Periodicals LLC on behalf of The Ecological Society of America.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Habitat severity characteristics structure soil communities at regional and local spatial scales along the Antarctica Peninsula
Antarctic soils provide an excellent setting to test biogeographical patterns across spatial and environmental scales given their relatively simple communities and the dominance of physical factors that create strong environmental gradients. Additional urgency is given by the fact that their unique terrestrial communities are the subject of conservation efforts in a rapidly changing environment. We investigated relationships of soil community assembly and alpha and beta diversity with climatic and environmental parameters across regional and local scales in Maritime Antarctica. We sampled from a regional gradient of sites that differ in habitat severity, ranging from relatively favourable to harsher physicochemical conditions. At the regional scale, bacterial community characteristics and microarthropod abundance varied along this severity gradient, but most measures of fungal communities did not. Microarthropod and microbial communities differed in which soil and climate parameters were most influential, and the specific parameters that influenced each taxon differed across broad and fine spatial scales. This suggests that conservation efforts will need to focus on a large variety of habitat characteristics to successfully encompass diversity across taxa. Because beta diversity was the result of species turnover, conservation efforts also cannot focus on only the most biodiverse sites to effectively preserve all aspects of biodiversity
Polar lessons learned: long-term management based on shared threats in Arctic and Antarctic environments
The Arctic and Antarctic polar regions are subject to multiple environmental threats, arising from both local and ex-situ human activities. We review the major threats to polar ecosystems including the principal stressor, climate change, which interacts with and exacerbates other threats such as pollution, fisheries overexploitation, and the establishment and spread of invasive species. Given the lack of progress in reducing global atmospheric greenhouse-gas emissions, we suggest that managing the threats that interact synergistically with climate change, and that are potentially more tractable, is all the more important in the short to medium term for polar conservation. We show how evidence-based lessons learned from scientific research can be shared between the poles on topics such as contaminant mitigation, biosecurity protocols to reduce species invasions, and the regulation of fisheries and marine environments. Applying these trans-polar lessons in tandem with expansion of international cooperation could substantially improve environmental management in both the Arctic and Antarctic
Biotic interactions are an unexpected yet critical control on the complexity of an abiotically driven polar ecosystem
10.1038/s42003-018-0274-5Communications Biology216
Ensuring planetary survival: the centrality of organic carbon in balancing the multifunctional nature of soils
Not only do soils provide 98.7% of the calories consumed by humans, they also provide numerous other functions upon which planetary survivability closely depends. However, our continuously increasing focus on soils for biomass provision (food, fiber, and energy) through intensive agriculture is rapidly degrading soils and diminishing their capacity to deliver other vital functions. These tradeoffs in soil functionality – the increased provision of one function at the expense of other critical planetary functions – are the focus of this review. We examine how land-use change for biomass provision has decreased the ability of soils to regulate the carbon pool and thereby contribute profoundly to climate change, to cycle the nutrients that sustain plant growth and ecosystem health, to protect the soil biodiversity upon which many other functions depend, and to cycle the Earth’s freshwater supplies. We also examine how this decreasing ability of soil to provide these other functions can be halted and reversed. Despite the complexity and the interconnectedness of soil functions, we show that soil organic carbon plays a central role and is a master indicator for soil functioning and that we require a better understanding of the factors controlling the behavior and persistence of C in soils. Given the threats facing humanity and their economies, it is imperative that we recognize that Soil Security is itself an existential challenge and that we need to increase our focus on the multiple functions of soils for long-term human welfare and survivability of the planet