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  • Climate change  (11)
  • Climate warming  (3)
  • Temperature  (3)
  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Blackwell for personal use, not for redistribution. The definitive version was published in Ecology Letters 12 (2009): E15-E18, doi:10.1111/j.1461-0248.2009.01332.x.
    Description: Hartley et al. question whether reduction in Rmass, under experimental warming, arises because of the biomass method. We show the method they treat as independent yields the same result. We describe why the substrate-depletion hypothesis cannot alone explain observed responses, and urge caution in the interpretation of the seasonal data.
    Description: This research was supported by the Office of Science (BER), U.S. Department of Energy, the Andrew W. Mellon Foundation and U.S. National Science Foundation grants to the Coweeta LTER program.
    Keywords: Acclimation ; Adaptation ; Soil respiration ; Thermal biology ; Temperature ; Carbon cycling ; Climate change ; Climate warming ; Microbial community ; CO2
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © American Institute of Biological Sciences, 2012. This article is posted here by permission of American Institute of Biological Sciences for personal use, not for redistribution. The definitive version was published in BioScience 62 (2012): 377-389, doi:10.1525/bio.2012.62.4.9.
    Description: The US National Science Foundation—funded Long Term Ecological Research (LTER) Network supports a large (around 240) and diverse portfolio of long-term ecological experiments. Collectively, these long-term experiments have (a) provided unique insights into ecological patterns and processes, although such insight often became apparent only after many years of study; (b) influenced management and policy decisions; and (c) evolved into research platforms supporting studies and involving investigators who were not part of the original design. Furthermore, this suite of long-term experiments addresses, at the site level, all of the US National Research Council's Grand Challenges in Environmental Sciences. Despite these contributions, we argue that the scale and scope of global environmental change requires a more-coordinated multisite approach to long-term experiments. Ideally, such an approach would include a network of spatially extensive multifactor experiments, designed in collaboration with ecological modelers that would build on and extend the unique context provided by the LTER Network.
    Description: 2012-10-01
    Keywords: Climate change ; Global change ; Long-term research ; LTER Network ; Multifactor experiments
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2022-05-25
    Description: © The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Plant and Soil 356 (2012): 405-417, doi:10.1007/s11104-012-1130-x.
    Description: Soil warming from global climate change could increase decomposition of fine woody debris (FWD), but debris size and quality may mitigate this effect. The goal of this study was to investigate the effect of soil warming on decomposition of fine woody debris of differing size and quality. We placed FWD of two size classes (2 × 20 cm and 4 × 40 cm) and four species (Acer saccharum, Betula lenta, Quercus rubra and Tsuga canadensis) in a soil warming and ambient area at Harvard Forest in central Massachusetts. We collected the debris from each area over two years and measured mass loss and lignin concentration. Warming increased mass loss for all species and size classes (by as much as 30%), but larger debris and debris with higher initial lignin content decomposed slower than smaller debris and debris with lower initial lignin content. Lignin degradation did not follow the same trends as mass loss. Lignin loss from the most lignin-rich species, T. canadensis, was the highest despite the fact that it lost mass the slowest. Our results suggest that soil warming will increase decomposition of FWD in temperate forests. It is imperative that future models and policy efforts account for this potential shift in the carbon storage pool.
    Keywords: Woody debris ; Lignin ; Decomposition ; Soil warming ; Climate change
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Blackwell for personal use, not for redistribution. The definitive version was published in Ecology Letters 11 (2008): 1316-1327, doi:10.1111/j.1461-0248.2008.01251.x.
    Description: In the short-term heterotrophic soil respiration is strongly and positively related to temperature. In the long-term its response to temperature is uncertain. One reason for this is because in field experiments increases in respiration due to warming are relatively short-lived. The explanations proposed for this ephemeral response include depletion of fast-cycling, soil carbon pools and thermal adaptation of microbial respiration. Using a 〉15 year soil warming experiment in a mid-latitude forest, we show that the apparent ‘acclimation’ of soil respiration at the ecosystem scale results from combined effects of reductions in soil carbon pools and microbial biomass, and thermal adaptation of microbial respiration. Mass specific respiration rates were lower when seasonal temperatures were higher, suggesting that rate reductions under experimental warming likely occurred through temperature-induced changes in the microbial community. Our results imply that stimulatory effects of global temperature rise on soil respiration rates may be lower than currently predicted.
    Description: This research was supported by the Office of Science (BER), U.S. Department of Energy and the Andrew W. Mellon Foundation.
    Keywords: Acclimation ; Adaptation ; Soil respiration ; Thermal biology ; Temperature ; Carbon cycling ; Climate change ; Climate warming ; Microbial community ; CO2
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 5
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 21 (2008): 3776–3796, doi:10.1175/2008JCLI2038.1.
    Description: The impact of carbon–nitrogen dynamics in terrestrial ecosystems on the interaction between the carbon cycle and climate is studied using an earth system model of intermediate complexity, the MIT Integrated Global Systems Model (IGSM). Numerical simulations were carried out with two versions of the IGSM’s Terrestrial Ecosystems Model, one with and one without carbon–nitrogen dynamics. Simulations show that consideration of carbon–nitrogen interactions not only limits the effect of CO2 fertilization but also changes the sign of the feedback between the climate and terrestrial carbon cycle. In the absence of carbon–nitrogen interactions, surface warming significantly reduces carbon sequestration in both vegetation and soil by increasing respiration and decomposition (a positive feedback). If plant carbon uptake, however, is assumed to be nitrogen limited, an increase in decomposition leads to an increase in nitrogen availability stimulating plant growth. The resulting increase in carbon uptake by vegetation exceeds carbon loss from the soil, leading to enhanced carbon sequestration (a negative feedback). Under very strong surface warming, however, terrestrial ecosystems become a carbon source whether or not carbon–nitrogen interactions are considered. Overall, for small or moderate increases in surface temperatures, consideration of carbon–nitrogen interactions result in a larger increase in atmospheric CO2 concentration in the simulations with prescribed carbon emissions. This suggests that models that ignore terrestrial carbon–nitrogen dynamics will underestimate reductions in carbon emissions required to achieve atmospheric CO2 stabilization at a given level. At the same time, compensation between climate-related changes in the terrestrial and oceanic carbon uptakes significantly reduces uncertainty in projected CO2 concentration.
    Keywords: Carbon dioxide ; Chemistry, atmospheric ; Greenhouse gases ; Ecosystem effects ; Temperature
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 6 (2015): 104, doi:10.3389/fmicb.2015.00104.
    Description: Soil microbes are major drivers of soil carbon cycling, yet we lack an understanding of how climate warming will affect microbial communities. Three ongoing field studies at the Harvard Forest Long-term Ecological Research (LTER) site (Petersham, MA) have warmed soils 5°C above ambient temperatures for 5, 8, and 20 years. We used this chronosequence to test the hypothesis that soil microbial communities have changed in response to chronic warming. Bacterial community composition was studied using Illumina sequencing of the 16S ribosomal RNA gene, and bacterial and fungal abundance were assessed using quantitative PCR. Only the 20-year warmed site exhibited significant change in bacterial community structure in the organic soil horizon, with no significant changes in the mineral soil. The dominant taxa, abundant at 0.1% or greater, represented 0.3% of the richness but nearly 50% of the observations (sequences). Individual members of the Actinobacteria, Alphaproteobacteria and Acidobacteria showed strong warming responses, with one Actinomycete decreasing from 4.5 to 1% relative abundance with warming. Ribosomal RNA copy number can obfuscate community profiles, but is also correlated with maximum growth rate or trophic strategy among bacteria. Ribosomal RNA copy number correction did not affect community profiles, but rRNA copy number was significantly decreased in warming plots compared to controls. Increased bacterial evenness, shifting beta diversity, decreased fungal abundance and increased abundance of bacteria with low rRNA operon copy number, including Alphaproteobacteria and Acidobacteria, together suggest that more or alternative niche space is being created over the course of long-term warming.
    Description: This work was supported by funding from the University of Massachusetts Amherst to DeAngelis and the National Science Foundation Long-term Ecological Research (LTER) Program.
    Keywords: Climate change ; Microbial ecology ; Ribosomal RNA ; rrn operon copy number ; Trophic strategy
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Energy Policy 35 (2007): 5370-5383, doi:10.1016/j.enpol.2006.01.040.
    Description: Multiple environmental changes will have consequences for global vegetation. To the extent that crop yields and pasture and forest productivity are affected there can be important economic consequences. We examine the combined effects of changes in climate, increases in carbon dioxide, and changes in tropospheric ozone on crop, pasture, and forest lands and the consequences for the global and regional economies. We examine scenarios where there is limited or little effort to control these substances, and policy scenarios that limit emissions of CO2 and ozone precursors. We find the effects of climate and CO2 to be generally positive, and the effects of ozone to be very detrimental. Unless ozone is strongly controlled damage could offset CO2 and climate benefits. We find that resource allocation among sectors in the economy, and trade among countries, can strongly affect the estimate of economic effect in a country.
    Description: This research was supported by the US Department of Energy, US Environmental Protection Agency, US National Science Foundation, US National Aeronautics and Space Administration, US National Oceanographic and Atmospheric Administration; and the Industry and Foundation Sponsors of the MIT Joint Program on the Science and Policy of Global Change
    Keywords: Climate change ; Ozone damage ; Vegetation ; Agriculture ; Economics
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 8
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Soil Biology and Biochemistry 42 (2010): 611-617, doi:10.1016/j.soilbio.2009.12.011.
    Description: Arctic climate change is expected to lead to a greater frequency of extreme winter warming events. During these events, temperatures rapidly increase to well above 0ºC for a number of days, which can lead to snow melt at the landscape scale, loss of insulating snow cover and warming of soils. However, upon return of cold ambient temperatures, soils can freeze deeper and may experience more freeze-thaw cycles due to the absence of a buffering snow layer. Such loss of snow cover and changes in soil temperatures may be critical for litter decomposition since a stable soil microclimate during winter (facilitated by snow cover) allows activity of soil organisms. Indeed, a substantial part of fresh litter decomposition may occur in winter. However, the impacts of extreme winter warming events on soil processes such as decomposition have never before been investigated. With this study we quantify the impacts of winter warming events on fresh litter decomposition using field simulations and lab studies. Winter warming events were simulated in sub-Arctic heathland using infrared heating lamps and soil warming cables during March (typically the period of maximum snow depth) in three consecutive years of 2007, 2008, and 2009. During the winters of 2008 and 2009, simulations were also run in January (typically a period of shallow snow cover) on separate plots. The lab study included soil cores with and without fresh litter subjected to winter warming simulations in climate chambers. Litter decomposition of common plant species was unaffected by winter warming events simulated either in the lab (litter of Betula pubescens ssp. czerepanovii), or field (litter of Vaccinium vitis-idaea, and B. pubescens ssp. czerepanovii) with the exception of Vaccinium myrtillus (a common deciduous dwarf shrub) that showed less mass loss in response to winter warming events. Soil CO2 efflux measured in the lab study was (as expected) highly responsive to winter warming events but surprisingly fresh litter decomposition was not. Most fresh litter mass loss in the lab occurred during the first 3-4 weeks (simulating the period after litter fall). In contrast to past understanding, this suggests that winter decomposition of fresh litter is almost non-existent and observations of substantial mass loss across the cold season seen here and in other studies may result from leaching in autumn, prior to the onset of “true” winter. Further, our findings surprisingly suggest that extreme winter warming events do not affect fresh litter decomposition.
    Description: This research was supported by a Leverhulme Trust (UK) grant to GKP and TVC, by a grant from the Norwegian Research Council awarded to JWB, and by ATANS grants (EU Transnational Access Programme) to JWB, GKP and SB.
    Keywords: Arctic ; Betula pubescens ssp. czerepanovii ; Climate change ; Decomposition ; Extreme weather ; Freeze-thaw ; Snow ; Vaccinium vitis-idaea ; V. myrtillus ; Winter warming event
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 9
    Publication Date: 2022-10-27
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gewirtzman, J., Tang, J., Melillo, J. M., Werner, W. J., Kurtz, A. C., Fulweiler, R. W., & Carey, J. C. Soil warming accelerates biogeochemical silica cycling in a temperate forest. Frontiers in Plant Science, 10, (2019): 1097, doi:10.3389/fpls.2019.01097.
    Description: Biological cycling of silica plays an important role in terrestrial primary production. Soil warming stemming from climate change can alter the cycling of elements, such as carbon and nitrogen, in forested ecosystems. However, the effects of soil warming on the biogeochemical cycle of silica in forested ecosystems remain unexplored. Here we examine long-term forest silica cycling under ambient and warmed conditions over a 15-year period of experimental soil warming at Harvard Forest (Petersham, MA). Specifically, we measured silica concentrations in organic and mineral soils, and in the foliage and litter of two dominant species (Acer rubrum and Quercus rubra), in a large (30 × 30 m) heated plot and an adjacent control plot (30 × 30 m). In 2016, we also examined effects of heating on dissolved silica in the soil solution, and conducted a litter decomposition experiment using four tree species (Acer rubrum, Quercus rubra, Betula lenta, Tsuga canadensis) to examine effects of warming on the release of biogenic silica (BSi) from plants to soils. We find that tree foliage maintained constant silica concentrations in the control and warmed plots, which, coupled with productivity enhancements under warming, led to an increase in total plant silica uptake. We also find that warming drove an acceleration in the release of silica from decaying litter in three of the four species we examined, and a substantial increase in the silica dissolved in soil solution. However, we observe no changes in soil BSi stocks with warming. Together, our data indicate that warming increases the magnitude of silica uptake by vegetation and accelerates the internal cycling of silica in in temperate forests, with possible, and yet unresolved, effects on the delivery of silica from terrestrial to marine systems.
    Description: This research was supported by the National Science Foundation (NSF PLR-1417763 to JT), the Geological Society of America (Stephen G. Pollock Undergraduate Research Grant to JG), the Institute at Brown for Environment and Society, and the Marine Biological Laboratory. Sample analysis and Fulweiler’s involvement were supported by Boston University and a Bullard Fellowship from Harvard University. The soil warming experiment was supported by the National Science Foundation (DEB-0620443) and Department of Energy (DE-FC02-06-ER641577 and DE-SC0005421).
    Keywords: Silica ; Climate change ; Soil ; Warming ; Phytoliths ; Plants ; Biogeochemistry
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Global and Planetary Change 142 (2016): 28-40, doi:10.1016/j.gloplacha.2016.04.011.
    Description: In the circumpolar north (45-90°N), permafrost plays an important role in vegetation and carbon (C) dynamics. Permafrost thawing has been accelerated by the warming climate and exerts a positive feedback to climate through increasing soil C release to the atmosphere. To evaluate the influence of permafrost on C dynamics, changes in soil temperature profiles should be considered in global C models. This study incorporates a sophisticated soil thermal model (STM) into a dynamic global vegetation model (LPJ-DGVM) to improve simulations of changes in soil temperature profiles from the ground surface to 3 m depth, and its impacts on C pools and fluxes during the 20th and 21st centuries.With cooler simulated soil temperatures during the summer, LPJ-STM estimates ~0.4 Pg C yr-1 lower present-day heterotrophic respiration but ~0.5 Pg C yr-1 higher net primary production than the original LPJ model resulting in an additional 0.8 to 1.0 Pg C yr-1 being sequestered in circumpolar ecosystems. Under a suite of projected warming scenarios, we show that the increasing active layer thickness results in the mobilization of permafrost C, which contributes to a more rapid increase in heterotrophic respiration in LPJ-STM compared to the stand-alone LPJ model. Except under the extreme warming conditions, increases in plant production due to warming and rising CO2, overwhelm the enhanced ecosystem respiration so that both boreal forest and arctic tundra ecosystems remain a net C sink over the 21st century. This study highlights the importance of considering changes in the soil thermal regime when quantifying the C budget in the circumpolar north.
    Description: This research is supported by funded projects to Q. Z. National Science Foundation (NSF- 1028291 and NSF- 0919331), the NSF Carbon and Water in the Earth Program (NSF-0630319), the NASA Land Use and Land Cover Change program (NASA- NNX09AI26G), and Department of Energy (DE-FG02-08ER64599).
    Description: 2017-05-03
    Keywords: Soil thermal regime ; Permafrost degradation ; Active layer ; Climate warming ; Carbon budget
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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