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  • 1
    Electronic Resource
    Electronic Resource
    Ecosystem carbon storage in arctic tundra reduced by long-term nutrient fertilization (2004)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 431 (2004), S. 440-443 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Global warming is predicted to be most pronounced at high latitudes, and observational evidence over the past 25 years suggests that this warming is already under way. One-third of the global soil carbon pool is stored in northern latitudes, so there is considerable interest in understanding ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature02887
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  • 2
    Electronic Resource
    Electronic Resource
    Resource-based niches provide a basis for plant species diversity and dominance in arctic tundra (2002)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 415 (2002), S. 68-71 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Ecologists have long been intrigued by the ways co-occurring species divide limiting resources. Such resource partitioning, or niche differentiation, may promote species diversity by reducing competition. Although resource partitioning is an important determinant of species diversity and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/415068a
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  • 3
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    Species compositional differences on different-aged glacial landscapes drive contrasting responses of tundra to nutrient addition (2005)
    Details
    Publication Date: 2017-01-05
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Blackwell Publishing for personal use, not for redistribution. The definitive version was published in Journal of Ecology 93 (2005): 770-782, doi:10.1111/j.1365-2745.2005.01006.x.
    Description: In the northern foothills of the Brooks Range, Alaska, moist non-acidic tundra dominates more recently deglaciated upland landscapes, whereas moist acidic tundra dominates older upland landscapes. In previous studies, experimental fertilization of moist acidic tussock tundra greatly increased the abundance and productivity of the deciduous dwarf shrub Betula nana. However, this species is largely absent from moist non-acidic tundra. These two common upland tundra community types exhibited markedly different responses to fertilization with nitrogen and phosphorus. In moist acidic tundra, cover of deciduous shrubs (primarily B. nana) increased after only 2 years, and by 4 years vascular biomass and above-ground net primary productivity (ANPP) had increased significantly, almost entirely because of Betula. In moist non-acidic tundra, both biomass and ANPP were again significantly greater, but no single species dominated the response to fertilization. Instead, the effect was due to a combination of several small, sometimes statistically non-significant responses by forbs, graminoids and prostrate deciduous shrubs. The different growth form and species' responses suggest that fertilization will cause carbon cycling through plant biomass to diverge in these two tundra ecosystems. Already, production of new stems by apical growth has increased relative to leaf production in acidic tundra, whereas the opposite has occurred in non-acidic tundra. Secondary stem growth has also increased as a component of primary production in acidic tundra, but is unchanged in non-acidic tundra. Thus, fertilization will probably increase carbon sequestration in woody biomass of B. nana in acidic tundra, while increasing carbon turnover (but not storage) of non-woody species in non-acidic tundra. These results indicate that nutrient enrichment can have very different consequences for plant communities that occur on different geological substrates, because of differences in composition, even though they share the same regional species pool. Although the specific edaphic factors that maintain compositional differences in this case are unknown, variation in soil pH and related variability in soil nutrient availability may well play a role.
    Description: This research was supported by a collaborative grant from the National Science Foundation (OPP-9902695 to S.E.H. and OPP-9902721 to L.G.) and by the Arctic LTER (DEB-9810222).
    Keywords: Alaska ; Arctic ; Betula nana ; Fertilization ; Moist acidic tundra ; Moist non-acidic tundra ; Net primary production ; Nitrogen ; pH ; Phosphorus
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 4
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    Terrestrial C sequestration at elevated CO2 and temperature : the role of dissolved organic N loss (2005)
    Details
    Publication Date: 2022-05-25
    Description: Author's draft titled: Carbon sequestration in terrestrial ecosystems under elevated CO2 and temperature : role of dissolved organic versus inorganic nitrogen loss
    Description: Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 15 (2005): 71–86, doi:10.1890/03-5303
    Description: We used a simple model of carbon–nitrogen (C–N) interactions in terrestrial ecosystems to examine the responses to elevated CO2 and to elevated CO2 plus warming in ecosystems that had the same total nitrogen loss but that differed in the ratio of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN) loss. We postulate that DIN losses can be curtailed by higher N demand in response to elevated CO2, but that DON losses cannot. We also examined simulations in which DON losses were held constant, were proportional to the amount of soil organic matter, were proportional to the soil C:N ratio, or were proportional to the rate of decomposition. We found that the mode of N loss made little difference to the short-term (〈60 years) rate of carbon sequestration by the ecosystem, but high DON losses resulted in much lower carbon sequestration in the long term than did low DON losses. In the short term, C sequestration was fueled by an internal redistribution of N from soils to vegetation and by increases in the C:N ratio of soils and vegetation. This sequestration was about three times larger with elevated CO2 and warming than with elevated CO2 alone. After year 60, C sequestration was fueled by a net accumulation of N in the ecosystem, and the rate of sequestration was about the same with elevated CO2 and warming as with elevated CO2 alone. With high DON losses, the ecosystem either sequestered C slowly after year 60 (when DON losses were constant or proportional to soil organic matter) or lost C (when DON losses were proportional to the soil C:N ratio or to decomposition). We conclude that changes in long-term C sequestration depend not only on the magnitude of N losses, but also on the form of those losses.
    Description: This work was funded, in part, by the National Science Foundation (DEB 0108960 and DEB 0089585) and in part by the USGS Global Change Research Program.
    Keywords: Carbon–nitrogen interactions ; Carbon sequestration ; Dissolved inorganic nitrogen ; Dissolved organic nitrogen ; Ecosystem models ; Global climate change ; Carbon–nitrogen interactions ; Terrestrial ecosystems
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 5
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    Climate and species affect fine root production with long-term fertilization in acidic tussock tundra near Toolik Lake, Alaska (2007)
    Details
    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 Springer for personal use, not for redistribution. The definitive version was published in Oecologia 153 (2007): 643-652, doi:10.1007/s00442-007-0753-8.
    Description: Long-term fertilization of acidic tussock tundra has led to changes in plant species composition, increases in aboveground production and biomass and substantial losses of soil organic carbon (SOC). Root litter is an important input to SOC pools, though little is known about fine root demography in tussock tundra. In this study, we examined the response of fine root production and live standing fine root biomass to short- and long-term fertilization, as changes in fine root demography may contribute to observed declines in SOC. Live standing fine root biomass increased with long-term fertilization, while fine root production declined, reflecting replacement of the annual fine root system of Eriophorum vaginatum, with the long-lived fine roots of Betula nana. Fine root production increased in fertilized plots during an unusually warm growing season, but remained unchanged in control plots, consistent with observations that B. nana shows a positive response to climate warming. Calculations based on a few simple assumptions suggest changes in fine root demography with long-term fertilization and species replacement could account for between 20 and 39% of observed declines in SOC stocks.
    Description: This project was supported by National Science Foundation research grants 9810222, 9911681, 0221606 and 0528748.
    Keywords: Betula nana ; Eriophorum vaginatum ; Fertilization ; Fine roots ; Ingrowth cores ; Minirhizotrons ; Soil organic carbon ; Tussock tundra
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 6
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    Plant community responses to experimental warming across the tundra biome (2006)
    National Academy of Sciences of the USA
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © National Academy of Sciences, 2006. This article is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 103 (2006): 1342-1346, doi:10.1073/pnas.0503198103.
    Description: Recent observations of changes in some tundra ecosystems appear to be responses to a warming climate. Several experimental studies have shown that tundra plants and ecosystems can respond strongly to environmental change, including warming; however, most studies were limited to a single location and were of short duration and based on a variety of experimental designs. In addition, comparisons among studies are difficult because a variety of techniques have been used to achieve experimental warming and different measurements have been used to assess responses. We used metaanalysis on plant community measurements from standardized warming experiments at 11 locations across the tundra biome involved in the International Tundra Experiment. The passive warming treatment increased plant-level air temperature by 1-3°C, which is in the range of predicted and observed warming for tundra regions. Responses were rapid and detected in whole plant communities after only two growing seasons. Overall, warming increased height and cover of deciduous shrubs and graminoids, decreased cover of mosses and lichens, and decreased species diversity and evenness. These results predict that warming will cause a decline in biodiversity across a wide variety of tundra, at least in the short term. They also provide rigorous experimental evidence that recently observed increases in shrub cover in many tundra regions are in response to climate warming. These changes have important implications for processes and interactions within tundra ecosystems and between tundra and the atmosphere.
    Description: The projects represented here were supported by many sources, including the National Science Foundation, Swedish Natural Science Research Council, United Kingdom Natural Environment Research Council, Natural Sciences and Engineering Research Council of Canada, Research Council of Norway, Icelandic Centre for Research, and the Academy of Finland. Coordination of activities was made possible with support from the Bonanza Creek Long-Term Ecological Research site.
    Keywords: Arctic and alpine ecosystems ; Biodiversity ; Climate change ; Vegetation change
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    Tight coupling between leaf area index and foliage N content in arctic plant communities (2006)
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    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Oecologia 142 (2005): 421-427, doi:10.1007/s00442-004-1733-x.
    Description: The large spatial heterogeneity of arctic landscapes complicates efforts to quantify key processes of these ecosystems, for example productivity, at the landscape level. Robust relationships that help to simplify and explain observed patterns, are thus powerful tools for understanding and predicting vegetation distribution and dynamics. Here we present the same linear relationship between leaf area index and total foliar nitrogen, the two factors determining the photosynthetic capacity of vegetation, across a wide range of tundra vegetation types in both Northern-Sweden and Alaska between leaf area indices of 0 and 1 m2 m-2, which is essentially the entire range of leaf area index values for the Arctic as a whole. Surprisingly, this simple relationship arises as an emergent property at the plant community level, whereas at the species level a large variability in leaf traits exists. As the relationship between LAI and foliar N exists among such varied ecosystems, the arctic environment must impose tight constraints on vegetation canopy development. This relationship simplifies the quantification of vegetation productivity of arctic vegetation types as the two most important drivers of productivity can now be estimated reliably from remotely sensed NDVI images.
    Description: This work was funded by the US National Science Foundation.
    Keywords: Arctic ecosystems ; Productivity ; Vascular plants
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 8
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    Plant functional types do not predict biomass responses to removal and fertilization in Alaskan tussock tundra (2008)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: © 2008 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License 2.5. The definitive version was published in Journal of Ecology 96 (2008): 713-726, doi:10.1111/j.1365-2745.2008.01378.x.
    Description: Plant communities in natural ecosystems are changing and species are being lost due to anthropogenic impacts including global warming and increasing nitrogen (N) deposition. We removed dominant species, combinations of species and entire functional types from Alaskan tussock tundra, in the presence and absence of fertilization, to examine the effects of non-random species loss on plant interactions and ecosystem functioning. After 6 years, growth of remaining species had compensated for biomass loss due to removal in all treatments except the combined removal of moss, Betula nana and Ledum palustre (MBL), which removed the most biomass. Total vascular plant production returned to control levels in all removal treatments, including MBL. Inorganic soil nutrient availability, as indexed by resins, returned to control levels in all unfertilized removal treatments, except MBL. Although biomass compensation occurred, the species that provided most of the compensating biomass in any given treatment were not from the same functional type (growth form) as the removed species. This provides empirical evidence that functional types based on effect traits are not the same as functional types based on response to perturbation. Calculations based on redistributing N from the removed species to the remaining species suggested that dominant species from other functional types contributed most of the compensatory biomass. Fertilization did not increase total plant community biomass, because increases in graminoid and deciduous shrub biomass were offset by decreases in evergreen shrub, moss and lichen biomass. Fertilization greatly increased inorganic soil nutrient availability. In fertilized removal treatments, deciduous shrubs and graminoids grew more than expected based on their performance in the fertilized intact community, while evergreen shrubs, mosses and lichens all grew less than expected. Deciduous shrubs performed better than graminoids when B. nana was present, but not when it had been removed. Synthesis. Terrestrial ecosystem response to warmer temperatures and greater nutrient availability in the Arctic may result in vegetative stable-states dominated by either deciduous shrubs or graminoids. The current relative abundance of these dominant growth forms may serve as a predictor for future vegetation composition.
    Description: This work was supported by NSF grants DEB-0213130, DEB-0516509, OPP-0623364, DEB-981022 and DEB-0423385, and by the Inter-American Institute for Global Change Research (IAI) CRN 2015 which is supported by the US National Science Foundation (GEO-0452325). Open access to this publication was partially supported by the Berkeley Research Impact Initiative Program.
    Keywords: Arctic tundra ; Biodiversity ; Biomass compensation ; Nitrogen ; Plant functional types ; Productivity ; Species interactions ; Species removal ; Soil nutrient availability
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
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    Ecosystem feedbacks and cascade processes : understanding their role in the responses of Arctic and alpine ecosystems to environmental change (2009)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2009. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Global Change Biology 15 (2009): 1153-1172, doi:10.1111/j.1365-2486.2008.01801.x.
    Description: Global environmental change, related to climate change and the deposition of airborne N-containing contaminants, has already resulted in shifts in plant community composition among plant functional types in arctic and temperate alpine regions. In this paper, we review how key ecosystem processes will be altered by these transformations, the complex biological cascades and feedbacks that may result, and some of the potential broader consequences for the earth system. Firstly, we consider how patterns of growth and allocation, and nutrient uptake, will be altered by the shifts in plant dominance. The ways in which these changes may disproportionately affect the consumer communities, and rates of decomposition, are then discussed. We show that the occurrence of a broad spectrum of plant growth forms in these regions (from cryptogams to deciduous and evergreen dwarf shrubs, graminoids and forbs), together with hypothesized low functional redundancy, will mean that shifts in plant dominance result in a complex series of biotic cascades, couplings and feedbacks which are supplemental to the direct responses of ecosystem components to the primary global change drivers. The nature of these complex interactions is highlighted using the example of the climate-driven increase in shrub cover in low arctic tundra, and the contrasting transformations in plant functional composition in mid-latitude alpine systems. Finally, the potential effects of the transformations on ecosystem properties and processes which link with the earth system are reviewed. We conclude that the effects of global change on these ecosystems, and potential climate-change feedbacks, can not be predicted from simple empirical relationships between processes and driving variables. Rather, the effects of changes in species distributions and dominances on key ecosystem processes and properties must also be considered, based upon best estimates of the trajectories of key transformations, their magnitude and rates of change.
    Description: We thank the International Arctic Science Committee (IASC) for their support for this Mini- Review as part of the IASC Circum-Arctic Terrestrial Biodiversity initiative (CAT-B) and as part of International Polar Year 2007/2008.
    Keywords: Arctic ; Alpine ; Carbon ; Ecosystem ; Energy ; Global change ; Feedback ; Nitrogen ; Herbivory ; Plant functional type
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 10
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    The contribution of mosses to the carbon and water exchange of arctic ecosystems : quantification and relationships with system properties (2008)
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © The Authors, 2007. 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 Plant, Cell & Environment 30 (2008): 1205-1215, doi:10.1111/j.1365-3040.2007.01697.x.
    Description: Water vapour and CO2 exchange were measured in moss dominated vegetation using a gas analyzer and a 1 m by 1 m chamber at 17 sites near Abisko, Northern Sweden and 21 sites near Longyearbyen, Svalbard, to quantify the contribution of mosses to ecosystem level fluxes. With the help of a simple light-response model we showed that the moss contribution to ecosystem carbon uptake varied between 14 and 96%, with an average contribution of around 60%. This moss contribution could be related to the NDVI (normalized difference vegetation index) of the vegetation and the leaf area index (LAI) of the vascular plants. NDVI was a good predictor of gross primary production (GPP) of mosses and of the whole ecosystem, across different moss species, vegetation types and two different latitudes. NDVI was also correlated with thickness of the active green moss layer. Mosses played an important role in water exchange. They are expected to be most important to gas exchange during spring when leaves are not fully developed.
    Description: We acknowledge funding from the US National Science Foundation to the Marine Biological Laboratory (NSF Grant # OPP-0352897).
    Keywords: Carbon flux ; Water flux ; Mosses ; Arctic ecosystems
    Repository Name: Woods Hole Open Access Server
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