An Integrated Tool for Calculating and Reducing Institution Carbon and Nitrogen Footprints.

The development of nitrogen footprint tools has allowed a range of entities to calculate and reduce their contribution to nitrogen pollution, but these tools represent just one aspect of environmental pollution. For example, institutions have been calculating their carbon footprints to track and manage their greenhouse gas emissions for over a decade. This article introduces an integrated tool that institutions can use to calculate, track, and manage their nitrogen and carbon footprints together.

Spruce-fir forest changes during a 30-year nitrogen saturation experiment.

A field experiment was established in a high elevation red spruce (Picea rubens Sarg.) - balsam fir (Abies balsamea) forest on Mount Ascutney Vermont, USA in 1988 to test the nitrogen (N) saturation hypothesis, and to better understand the mechanisms causing forest decline at the time. The study established replicate control, low and high dose nitrogen addition plots (i.

A N tracer technique for assessing fine root production and mortality.

We tested a N tracer technique to assess fine root production and mortality based on temporal measurements of the N mass in fine root structural tissues and the N concentration of the plant-available soil N pool. The results of a pilot study indicated that this technique is based on sound methods and reasonable assumptions. The N tracer technique avoids most of the major limitations which hinder existing methods and may provide valuable insight into the rates and controls of fine root production and mortality in terrestrial ecosystems.

Extrapolating leaf CO exchange to the canopy: a generalized model of forest photosynthesis compared with measurements by eddy correlation.

Over the last 4 years, two data sets have emerged which allow increased accuracy and resolution in the definition and validation of a photosynthesis model for whole forest canopies. The first is a greatly expanded set of data on the nitrogen-photosynthesis relationship for temperate and tropical woody species. The second is a unique set of long-term (4 year) daily carbon balance measurements at the Harvard Forest, Petersham, Massachusetts, collected by the eddy-correlation technique.

Immobilization of a N-labeled nitrate addition by decomposing forest litter.

Effects of chronic HNO and HSO additions on decomposition of senesced birch leaf, beech leaf, spruce needle, and wood chip litters were examined. Litters were incubated for up to 4 years in fiberglass mesh (1 mm) bags on experimental plots in a mixed-species forest near the Bear Brooks Watershed Manipulation (BBWM) site in eastern Maine, United States. Plot treatments included HNO additions at 28 and 56 kg N·ha·year, HSO additions at 128 kg S·ha·year, and a combined HNO and HSO treatment at 28 kg N and 64 kg S ·ha·year.

The fate of N-labelled nitrate additions to a northern hardwood forest in eastern Maine, USA.

We followed the movements of N-labelled nitrate additions into biomass and soil pools of experimental plots (15×15 m each) in a mid-successional beech-maple-birch-spruce forest in order to identify sinks for nitrate inputs to a forest ecosystem. Replicate plots (n=3) were spray-irrigated with either 28 or 56 kg N ha year using N-labelled nitric acid solutions (δN = 344‰ ) during four successive growing seasons (April-October). The N contents of foliage, bolewood, forests floor and mineral soil (0-5 cm) increased during the course of treatments.

A Spatial Model of Atmospheric Deposition for the Northeastern U.S.

Spatial patterns of atmospheric deposition across the northeastern United States were evaluated and summarized in a simple model as a function of elevation and geographic position within the region. For wet deposition, 3-11 yr of annual concentration data for the major ions in precipitation were obtained from the National Atmospheric Deposition Program/National Trend Network (NADP/NTN) for 26 sites within the region. Concentration trends were evaluated by regression of annual mean concentrations against latitude and longitude.

Plant and Soil Responses to Chronic Nitrogen Additions at the Harvard Forest, Massachusetts.

Data are presented on changes in plant and soil processes in two forest types (red pine plantation and oak-maple forest) at the Harvard Forest, Petersham, Massachusetts, in response to 3 yr of chronic N fertilization. The hardwood stand exhibited greater N limitation on biological function than the pine stand prior to fertilization as evidenced by a lower net N mineralization rate, nearly undetectable rates of net nitrification, and very low foliar N content. N additions were made in six equal applications throughout the growing season, and consisted of 5 and 15 g°m °yr of N as ammonium nitrate.

A generalized, lumped-parameter model of photosynthesis, evapotranspiration and net primary production in temperate and boreal forest ecosystems.

PnET is a simple, lumped-parameter, monthlytime-step model of carbon and water balances of forests built on two principal relationships: 1) maximum photosynthetic rate is a function of foliar nitrogen concentration, and 2) stomatal conductance is a function of realized photosynthetic rate. Monthyly leaf area display and carbon and water balances are predicted by combining these with standard equations describing light attenuation in canopies and photosynthetic response to diminishing radiation intensity, along with effects of soil water stress and vapor pressure deficit (VPD). PnET has been validated against field data from 10 well-studied temperate and boreal forest ecosystems, supporting our central hypothesis that aggregation of climatic data to the monthly scale and biological data such as foliar characteristics to the ecosystem level does not cause a significant loss of information relative to long-term, mean ecosystem responses.

Factors Controlling Nitrogen Cycling and Nitrogen Saturation in Northern Temperate Forest Ecosystems.

An analysis of the factors controlling rates of nitrogen cycling in northern temperate forest ecosystems is presented based on a quantitative analysis of an extensive data set for forests in Wisconsin and Massachusetts as those data are synthesized in a computer model (VEGIE) of organic matter and nutrient dynamics. The model is of the "lumped-parameter," nutrient-flux-density type, dealing with major components of forest ecosystems rather than stems or species. It deals explicitly with the interactions among light, water, and nutrient availability in determining transient and equilibrium rates of primary production and nutrient cycling.

A general biogeochemical model describing the responses of the C and N cycles in terrestrial ecosystems to changes in CO(2), climate, and N deposition.

A model that simulates carbon (C) and nitrogen (N) cycles in terrestrial ecosystems is developed. The model is based on the principle that the responses of terrestrial ecosystems to changes in CO(2), climate, and N deposition will encompass enzymatic responses, shifts in tissue stoichiometry, changes in biomass allocation among plant tissues, altered rates of soil organic matter turnover and N mineralization, and ultimately a redistribution of C and N between vegetation and soils. The model is a highly aggregated, process-based, biogeochemical model designed to examine changes in the fluxes and allocation of C and N among foliage, fine roots, stems, and soils in response to changes in atmospheric CO(2) concentration, temperature, soil water, irradiance, and inorganic nitrogen inputs.

Fine root turnover in forest ecosystems in relation to quantity and form of nitrogen availability: a comparison of two methods.

Two methods of estimating fine root production and turnover are compared for 13 forest ecosystems exhibiting a wide range in form (NH vs. NO) and quantity of available nitrogen. The two methods are by comparison of seasonal maxima and minima in biomess and by nitrogen budgeting.

The influence of substrate quality and stream size on wood decomposition dynamics.

Woody materials decayed more rapidly in a first order stream than in larger streams in eastern Quebec, Canada. The rate of annual mass loss (k) was highest (k=1.20) for alder wood chips in a first order stream and lowest (k=0.