Litterfall 15N abundance indicates declining soil nitrogen availability in a free-air CO2 enrichment experiment.

Forest productivity increases in response to carbon dioxide (CO2) enrichment of the atmosphere. However, in nitrogen-limited ecosystems, increased productivity may cause a decline in soil nitrogen (N) availability and induce a negative feedback on further enhancement of forest production. In a free-air CO2 enrichment (FACE) experiment, the response of sweetgum (Liquidambar styraciflua L.

Characterization of biochars produced from cornstovers for soil amendment.

Through cation exchange capacity assay, nitrogen adsorption-desorption surface area measurements, scanning electron microscopic imaging, infrared spectra and elemental analyses, we characterized biochar materials produced from cornstover under two different pyrolysis conditions, fast pyrolysis at 450 °C and gasification at 700 °C. Our experimental results showed that the cation exchange capacity (CEC) of the fast-pyrolytic char is about twice as high as that of the gasification char as well as that of a standard soil sample. The CEC values correlate well with the increase in the ratios of the oxygen atoms to the carbon atoms (O:C ratios) in the biochar materials.

Belowground fate of (15)N injected into sweetgum trees (Liquidambar styraciflua) at the ORNL FACE Experiment.

Nitrogen (N) cycling can be an important constraint on forest ecosystem response to elevated atmospheric CO(2). Our objective was to trace the movement of (15)N, injected into tree sap, to labile and stable forms of soil organic matter derived partly from the turnover of tree roots under elevated (545 ppm) and ambient (394 ppm) atmospheric CO(2) concentrations at the Oak Ridge National Laboratory (ORNL) FACE (Free-Air Carbon Dioxide Enrichment) Experiment. Twenty-four sweetgum trees, divided equally between CO(2) treatments, were injected with 3.

Spatial scaling of functional gene diversity across various microbial taxa.

Understanding the spatial patterns of organisms and the underlying mechanisms shaping biotic communities is a central goal in community ecology. One of the most well documented spatial patterns in plant and animal communities is the positive-power law relationship between species (or taxa) richness and area. Such taxa-area relationships (TARs) are one of the principal generalizations in ecology, and are fundamental to our understanding of the distribution of global biodiversity.

Predicted effects of prescribed burning and harvesting on forest recovery and sustainability in southwest Georgia, USA.

A model-based analysis of the effect of prescribed burning and forest thinning or clear-cutting on stand recovery and sustainability was conducted at Fort Benning, GA, in the southeastern USA. Two experiments were performed with the model. In the first experiment, forest recovery from degraded soils was predicted for 100 years with or without prescribed burning.

Laser-induced breakdown spectroscopy for the environmental determination of total carbon and nitrogen in soils.

Soils from various sites have been analysed with the laser-induced breakdown spectroscopy (LIBS) technique for total elemental determination of carbon and nitrogen. Results from LIBS have been correlated to a standard laboratory-based technique (sample combustion), and strong linear correlations were obtained for determination of carbon concentrations. The LIBES technique was used on soils before and after acid washing, and the technique appears to be useful for the determination of both organic and inorganic soil carbon.

Deposition of H NO vapour to white oak, red maple and loblolly pine foliage: experimental observations and a generalized model.

Nitric acid vapour enriched with N (H NO ) was volatilized into the cuvette of an open-flow gas exchange system containing red maple (Acer rubrum L.), white oak (Quercus alba L.), or loblolly pine (Pinus taeda L.