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  • 1
    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): 342-253, doi:10.1525/bio.2012.62.4.6.
    Description: The US Long Term Ecological Research (LTER) Network enters its fourth decade with a distinguished record of achievement in ecological science. The value of long-term observations and experiments has never been more important for testing ecological theory and for addressing today's most difficult environmental challenges. The network's potential for tackling emergent continent-scale questions such as cryosphere loss and landscape change is becoming increasingly apparent on the basis of a capacity to combine long-term observations and experimental results with new observatory-based measurements, to study socioecological systems, to advance the use of environmental cyberinfrastructure, to promote environmental science literacy, and to engage with decisionmakers in framing major directions for research. The long-term context of network science, from understanding the past to forecasting the future, provides a valuable perspective for helping to solve many of the crucial environmental problems facing society today.
    Description: 2012-10-01
    Keywords: Coupled natural—human systems ; Cyberinfrastructure ; Environmental observatories ; Environmental education ; Socioecological systems
    Repository Name: Woods Hole Open Access Server
    Type: Article
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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): 405-415, doi:10.1525/bio.2012.62.4.11.
    Description: The cryosphere—the portion of the Earth's surface where water is in solid form for at least one month of the year—has been shrinking in response to climate warming. The extents of sea ice, snow, and glaciers, for example, have been decreasing. In response, the ecosystems within the cryosphere and those that depend on the cryosphere have been changing. We identify two principal aspects of ecosystem-level responses to cryosphere loss: (1) trophodynamic alterations resulting from the loss of habitat and species loss or replacement and (2) changes in the rates and mechanisms of biogeochemical storage and cycling of carbon and nutrients, caused by changes in physical forcings or ecological community functioning. These changes affect biota in positive or negative ways, depending on how they interact with the cryosphere. The important outcome, however, is the change and the response the human social system (infrastructure, food, water, recreation) will have to that change.
    Description: The authors wish to thank the funding provided by the National Science Foundation’s (NSF) Long Term Ecological Research (LTER) Network for supporting our long-term studies, in which we track the ecosystem response to the disappearing cryosphere. NSF LTER Site Grants OPP 0823101, OPP 1115245, DEB 1114804, DEB-1026415, DEB-0620579, and DEB-1027341 supported the authors during the preparation of this article.
    Description: 2012-10-01
    Keywords: Cryosphere ; Ecosystem response ; Environmental observatories
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Most terrestrial carbon sequestration at mid-latitudes in the Northern Hemisphere occurs in seasonal, montane forest ecosystems. Winter respiratory carbon dioxide losses from these ecosystems are high, and over half of the carbon assimilated by photosynthesis in the summer can be lost the ...
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1939
    Keywords: Key words Trace gas flux  ;  Carbon dioxide  ;  Nitrous oxide  ;  Snow cover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fluxes of CO2 and N2O were measured from both natural and experimentally augmented snowpacks during the winters of 1993 and 1994 on Niwot Ridge in the Colorado Front Range. Consistent snow cover insulated the soil surface from extreme air temperatures and allowed heterotrophic activity to continue through much of the winter. In contrast, soil remained frozen at sites with inconsistent snow cover and production did not begin until snowmelt. Fluxes were measured when soil temperatures under the snow ranged from –5°C to 0°C, but there was no significant relationship between flux for either gas and temperature within this range. While early developing snowpacks resulted in warmer minimum soil temperatures allowing production to continue for most of the winter, the highest CO2 fluxes were recorded at sites which experienced a hard freeze before a consistent snowpack developed. Consequently, the seasonal flux of CO2 –C from snow covered soils was related both to the severity of freeze and the duration of snow cover. Over-winter CO2 –C loss ranged from 0.3 g C m−2 season−1 at sites characterized by inconsistent snow cover to 25.7 g C m−2 season−1 at sites that experienced a hard freeze followed by an extended period of snow cover. In contrast to the pattern observed with C loss, a hard freeze early in the winter did not result in greater N2O–N loss. Both mean daily N2O fluxes and the total over-winter N2O–N loss were related to the length of time soils were covered by a consistent snowpack. Over-winter N2O–N loss ranged from less 0.23 mg N m−2 from the latest developing, short duration snowpacks to 16.90 mg N m−2 from sites with early snow cover. These data suggest that over-winter heterotrophic activity in snow-covered soil has the potential to mineralize from less than 1% to greater than 25% of the carbon fixed in ANPP, while over-winter N2O fluxes range from less than half to an order of magnitude higher than growing season fluxes. The variability in these fluxes suggests that small changes in climate which affect the timing of seasonal snow cover may have a large effect on C and N cycling in these environments.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biogeochemistry 32 (1996), S. 93-113 
    ISSN: 1573-515X
    Keywords: alpine ; biogeochemistry ; nitrogen ; nitrogen saturation ; snowmelt ; soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Experiments were conducted during 1993 at Niwot Ridge in the Colorado Front Range to determine if the insulating effect of winter snow cover allows soil microbial activity to significantly affect nitrogen inputs and outputs in alpine systems. Soil surface temperatures under seasonal snowpacks warmed from −14 °C in January to 0 °C by May 4th. Snowmelt began in mid-May and the sites were snow free by mid June. Heterotrophic microbial activity in snow-covered soils, measured as C02 production, was first identified on March 4, 1993. Net C02 flux increased from 55 mg CO2-C m−2 day−1 in early March to greater than 824 mg CO2-C m-2 day−1 by the middle of May. Carbon dioxide production decreased in late May as soils became saturated during snowmelt. Soil inorganic N concentrations increased before snowmelt, peaking between 101 and 276 mg kg−1 soil in May, and then decreasing as soils became saturated with melt water. Net N mineralization for the period of March 3 to May 4 ranged from 2.23 to 6.63 g N m−2, and were approximately two orders of magnitude greater than snowmelt inputs of 50.4 mg N m−2 for NH4 + and 97.2 mg N m−2 for NO3 −. Both NO3 − and NH4 + concentrations remained at or below detection limits in surface water during snowmelt, indicating the only export of inorganic N from the system was through gaseous losses. Nitrous oxide production under snow was first observed in early April. Production increased as soils warned, peaking at 75 μg N2O-N m−2 day−1 in soils saturated with melt water one week before the sites were snow free. These data suggest that microbial activity in snow-covered soils may play a key role in alpine N cycling before plants become active.
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  • 6
    ISSN: 1573-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The fluxes and transformations of nitrogen (N) were investigated from 1985 through 1987 at the Emerald Lake watershed (ELW), a 120 ha high-elevation catchment located in the southern Sierra Nevada, California, USA. Up to 90% of annual wet deposition of N was stored in the seasonal snowpack; NO 3 − and NH 4 + were released from storage in the form of an ionic pulse, where the first fraction of meltwater draining from the snowpack had concentrations of NO 3 − and NH 4 + as high as 28 μeq L−1 compared to bulk concentrations of 〈5 μeq L−1 in the snowpack. The soil reservoir of organic N (81 keq ha−1) was about ten times the N storage in litter and biomass (12 keq ha−1). Assimilation of N by vegetation was balanced by the release of N from soil mineralization, nitrification, and litter decay. Mineralization and nitrification processes produced 1.1 keq ha−1 yr−1 of inorganic N, about 3 1/2 times the loading of N from wet and dry deposition. Less than 1% of the NH 4 + in wet and dry deposition was exported from the basin as NH 4 + . Biological assimilation was primarily responsible for retention of NH 4 + in the basin, releasing one mode of H+ for every mole of NH 4 + retained and neutralizing about 25% of the annual acid neutralizing capacity produced by mineral weathering in the basin. Nitrate concentrations in stream waters reached an annual peak during the first part of snowmelt runoff, with maximum concentrations in stream water of 20 μeq L−1, more than 4 times the volume-weighted mean annual concentrations of NO 3 − in wet deposition. This annual peak in stream water NO 3 − was consistent with the release of NO 3 − from the snowpack in the form of an ionic pulse; however soil processes occurring underneath the winter snowpack were another potential source of this NO 3 − . Concentrations of stream water NO 3 − during the summer growing season were always near or below detection limits (0.5 μeq L−1).
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biogeochemistry 43 (1998), S. 1-15 
    ISSN: 1573-515X
    Keywords: alpine ; nitrogen cycling ; nitrogen saturation ; snowmelt ; tundra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Recent work in seasonally snow covered ecosystems has identifiedthawed soil and high levels of heterotrophic activity throughout the winterunder consistent snow cover. We performed measurements during the winter of1994 to determine how the depth and timing of seasonal snow cover affectsoil microbial populations, surface water NO $${\text{NO}}_{\text{3}}^{\text{ - }} $$ loss during snowmelt, and plant Navailability early in the growing season. Soil under early accumulating,consistent snow cover remained thawed during most of the winter and bothmicrobial biomass and soil inorganic N pools gradually increased under thesnowpack. At the initiation of snowmelt, microbial biomass N pools increasedfrom 3.0 to 5.9 g n m-2,concurrent with a decrease in soil inorganic N pools. During the latterstages of snowmelt, microbial biomass N pools decreased sharply without aconcurrent increase in inorganic N pools or significant leaching losses. Incontrast, soil under inconsistent snow cover remained frozen during most ofthe winter. During snowmelt, microbial biomass initially increased from 1.7to 3.1 g N m-2 and thendecreased as sites became snow-free. In contrast to smaller pool sizes,NO $${\text{NO}}_{\text{3}}^{\text{ - }} $$ export during snowmeltfrom the inconsistent snow cover sites of 1.14 (±0.511) g N m-2 was significantly greater (p〈 0.001) than the 0.27 (±0.16) g N m-2 exported from sites with consistent snowcover. These data suggest that microbial biomass in consistentlysnow-covered soil provides a significant buffer limiting the export ofinorganic N to surface water during snowmelt. However, this buffer is verysensitive to changes in snowpack regime. Therefore, interannual variabilityin the timing and depth of snowpack accumulation may explain the year toyear variability in inorganic N concentrations in surface water theseecosystems.
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  • 8
    Publication Date: 2008-09-01
    Print ISSN: 0013-936X
    Electronic ISSN: 1520-5851
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
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  • 9
    Publication Date: 2011-08-01
    Description: Small changes in the flux of energy, chemicals, and water to mountain catchments may invoke large changes in the local climate, ecosystem dynamics, and water quantity and quality. The Landscape Continuum Model (LCM) was developed in part to improve our understanding of how high-elevation ecosystems might respond to future perturbations. We sampled water chemistry along the main stem of Boulder Creek in the Colorado Front Range from the foothills to the Continental Divide, along with four headwater catchments, to address two questions: (i) Is there value in extending the LCM concept to lower-elevation headwater catchments? (ii) Is a "space-for-time" substitution along an elevational gradient appropriate when there are changes in ecosystem type? Our results show that the hydrochemistry of headwater catchments along the elevational gradient of Boulder Creek was different when compared to the main stem. Headwater catchments amplified the fluxes of inorganic and organic solutes when compared with sites at similar elevations along the main stem of Boulder Creek, consistent with the LCM. Our results also suggest a space-for-time substitution along an elevational gradient is warranted for at least some biogeochemical processes when there is a switch from the snow to rain transition in annual precipitation. For example, the high concentrations of base cations and dissolved organic carbon in the foothills catchment when compared with higher elevation catchments is consistent with increased rates of biogeochemical cycling with increasing air temperature at lower elevations. However, the low-elevation catchment had a lower specific discharge than other catchments with similar annual precipitation, but higher percentages as snowfall, resulting in decreased fluxes of these products.
    Electronic ISSN: 1539-1663
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 10
    Publication Date: 2010-03-03
    Print ISSN: 1015-1621
    Electronic ISSN: 1420-9055
    Topics: Biology
    Published by Springer
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