A5053844834- Soil Carbon and Nitrogen Dynamics
- Peatlands and Wetlands Ecology
- Soil and Water Nutrient Dynamics
- Climate change and permafrost
- Plant Water Relations and Carbon Dynamics
- Forest ecology and management
- Ecology and Vegetation Dynamics Studies
- Fire effects on ecosystems
- Geology and Paleoclimatology Research
- Forest Ecology and Biodiversity Studies
- Forest Management and Policy
- Cryospheric studies and observations
- Isotope Analysis in Ecology
- Atmospheric and Environmental Gas Dynamics
- Groundwater and Isotope Geochemistry
- Rangeland and Wildlife Management
- Plant nutrient uptake and metabolism
- Botany and Plant Ecology Studies
- Seedling growth and survival studies
- Soil and Unsaturated Flow
- Remote Sensing in Agriculture
- Remote Sensing and LiDAR Applications
- Hydrology and Watershed Management Studies
- Plant responses to elevated CO2
- Mycorrhizal Fungi and Plant Interactions
University of Michigan
2015-2025
University of Michigan Biological Station
2005-2025
Marine Biological Laboratory
1995-2004
Ecosystem (Spain)
2002
Louisiana Department of Natural Resources
1998
University of New Hampshire
1998
University of New Hampshire at Manchester
1991-1998
Southern Research Station
1998
University of Mary
1998
University of Maine
1993-1998
Journal Article Nitrogen Saturation in Northern Forest Ecosystems: Excess nitrogen from fossil fuel combustion may stress the biosphere Get access John D. Aber, Aber Search for other works by this author on: Oxford Academic Google Scholar Knute J. Nadelhoffer, Nadelhoffer Paul Steudler, Steudler Jerry M. Melillo BioScience, Volume 39, Issue 6, June 1989, Pages 378–386, https://doi.org/10.2307/1311067 Published: 01 1989
itrogen emissions to the atmosphere due human activity remain elevated in industrialized regions of world and are accelerating many developing (Galloway 1995).Although deposition sulfur has been reduced aver much Uni ted Stares Europe by aggressive environmental protection policies, CUfrent nitrogen reduction targets US modest.Nitrogen rernains relatively canstant northeastern United is increasing Southeast West (Fenn er a1. press).Thc acid effects
We manipulated light, temperature, and nutrients in moist tussock tundra near Toolik Lake, Alaska to determine how global changes these parameters might affect community ecosystem processes. Some of manipulations altered nutrient availability, growth—form composition, net primary production, species richness less than a decade, indicating that arctic vegetation at this site is sensitive climatic change. In general, short—term (3—yr) responses were poor predictors longer term (9—yr)...
Abstract Traditional approaches to the study of food webs emphasize transfer local primary productivity in form living plant organic matter across trophic levels. However, dead matter, or detritus, a common feature most ecosystems plays frequently overlooked role as dynamic heterogeneous resource and habitat for many species. We develop an integrative framework understanding impact detritus that emphasizes ontogeny heterogeneity various ways explicit inclusion detrital dynamics alters...
Carbon allocation to roots in forest ecosystems is estimated from published data on soil respiration and litterfall. On a global scale, rates of situ aboveground litter production are highly positively correlated, suggesting that above— belowground controlled by the same factors. This relationship also allows us predict total carbon litterfall measurements. Over gradient ranging 70 500 g°m — 2 °yr 1 , increases 260 1100 . The ratio decreases 3.8 2.5 as 200 but changes little (2.5 2.2) Use...
We compared the effects of temperature on rates microbial respiration, N mineralization, nitrification, and P mineralization in soils from six arctic ecosystems located along a toposequence Alaska's North Slope. Soils these were incubated aerobically laboratory for 13 wk at temperatures representative field values during typical growing season. Rates C insensitive to between 3° 9°C but increased by factors 2 or more 9° 15°. For both N, differences among greater than due incubation within...
The relationships between above— and belowground net primary production soil nitrogen availability were studied at nine temperate forest sites. Annual allocations of (N) to leaf litter, perennial tissues (wood + bark), aboveground biomass all increases significantly (P < .01) in relation apparent N uptake by vegetation (N " u) as calculated using field measurers mineralization m ) other major fluxes from available pools. Mean annual content fine roots @<3.0 mm diameter) both negatively...
ABSTRACT Our objective is to describe a multi‐layer model of C 3 ‐canopy processes that effectively simulates hourly CO 2 and latent energy ( LE ) fluxes in mixed deciduous Quercus‐Acer (oak–maple) stand central Massachusetts, USA. The key hypothesis governing the biological component stomatal conductance g s varied so daily carbon uptake per unit foliar nitrogen maximized within limitations canopy water availability. hydraulic system modelled as an analogue simple electrical circuits...
Journal Article Global Change and the Carbon Balance of Arctic Ecosystems: Carbon/nutrient interactions should act as major constraints on changes in global terrestrial carbon cycling Get access Gaius R. Shaver, Shaver Search for other works by this author on: Oxford Academic Google Scholar W. D. Billings, Billings F. Stuart Chapin, III, III Anne E. Giblin, Giblin Knute J. Nadelhoffer, Nadelhoffer C. Oechel, Oechel B. Rastetter BioScience, Volume 42, Issue 6, June 1992, Pages 433–441,...
We compared published estimates of the net fine root production (FRP) in forest sites to litterfall and aboveground primary (ANPP) test whether annual rates vary together at global scales. also FRP theoretical upper limits as defined by our previously relationship between total allocation (TRA, carbon allocated plus live—root respiration) litterfall. Estimates content data set ranged from 25 820 g°m — 2 °yr 1 were not correlated with ANPP. Different methods used for estimating production,...
Estimating contributions by root respiration and litter to total soil is difficult owing problems in measuring each component separately. In a mixed hardwood forest Massachusetts, we added or removed aboveground terminated live activity through construction of trenches barriers determine the contribution litter, belowground respiration. Annual at control plots, measured soda-lime technique, was 371 g C•m −2 -year −1 . We used inputs (138 year ) differences carbon dioxide effluxes among...
Human activity in the last century has led to a significant increase nitrogen (N) emissions and atmospheric deposition. This N deposition reached level that caused or is likely cause alterations structure function of many ecosystems across United States. One approach for quantifying pollution would be harmful determination critical loads. A load defined as input pollutant below which no detrimental ecological effects occur over long-term according present knowledge. The objectives this...
Temperate forests are recipients of anthropogenic nitrogen (N) deposition. Because growth in these ecosystems is often limited by N availability, elevated inputs from the atmosphere can influence above‐ and belowground production forests. Although fine‐root largest component forests, it unclear whether or how increases Navailability to forest trees accompanying increased deposition might growth. Uncertainties as dynamics (i.e. turnover) vary relation soil availability contribute this...
Nitrogen and phosphorus pool sizes, distribution, cycling rates were described compared for six different ecosystem types occurring along a single toposequence in northern Alaska. The was located on series of old floodplains the Sagavanirktok River, foothills Brooks Range. From tussock tundra uplands, passed through relatively dry hilltop heath zone, hillslope shrub/lupine/Cassiope footslope Equisetum wet sedge tundra, riparian shrub zone. A late—melting snowbank covered site early June each...