Showing papers by "John D. Aber published in 1990"

Restoration Ecology: A Synthetic Approach to Ecological Research

Abstract: List of contributors Acknowledgements Part I Introduction: Part II Assembling Whole Systems in the Field: Part III Synthetic Ecology: Part IV Partial or Piecewise Restoration in the Field: Part V Restored Systems as Opportunities for Basic Research: Part VI Doing Restoration Ecology: Index

Predicting long-term patterns of mass loss, nitrogen dynamics, and soil organic matter formation from initial fine litter chemistry in temperate forest ecosystems

Abstract: Long-term decomposition data are presented for several types of foliar and fine root litter in different stands in Wisconsin and Massachusetts, USA Changes in mass remaining as well as nitrogen

Annual nitrous oxide fluxes from temperate forest soils in the northeastern United States

Abstract: Nitrous oxide (N{sub 2}O) fluxes were measured from soils in a red pine plantation and a mixed hardwood stand in the northeastern US. On an annual basis, the pine stand had an efflux of 0.010 {plus minus} 0.015 kg N/ha/yr and the hardwood stand had an efflux of 0.017 {plus minus} 0.017 kg N/ha/yr. Low net nitrification rates in both stands are suggested as the reason for the low rates of N{sub 2}O emissions. Slight seasonal trends were noted in both stands, with highest efflux rates in early summer and late fall. Both stands showed small but extended periods of uptake during summer and early fall. Diel patterns were not observed in either stand. This study suggests that on a global basis, a lower limit for N{sub 2}O emissions from temperate forests is 0.012 Tg N/yr, contributing less than 1% of the estimated total emissions from terrestrial sources.

Remote Sensing of Litter and Soil Organic Matter Decomposition in Forest Ecosystems

Abstract: Remote sensing is increasingly recognized as an important tool for landscape or regional estimation of ecosystem function, and for determination of biosphere-atmosphere interactions. Existing remote sensing systems have been used to monitor the seasonal phenology of standing green biomass and its production on a continental scale (Tucker et al., 1985); to measure changes in forest canopy leaf area index over large environmental gradients (Spanner et al., 1984, Running et al., 1986, Peterson et al., 1987); to track deforestation in tropical regions (Woodwell et al., 1986), and for the detection of ecosystem stress and forest decline (Rock et al., 1986). These approaches have relied on the detection of large structural changes in canopy properties that relate directly to processes controlling net primary productivity.

Effects of moisture content and chemical composition on the near infrared spectra of forest foliage

Abstract: Near infrared reflectance spectra were used to estimate nitrogen lignin and cellulose concentrations in fresh foliage samples. The spectra of sixty samples from 8 species (4 deciduous 4 conifer) were measured from llOO-2500nxn when the samples were both fresh and dried. Existing regression equations relating near infrared reflectance to sample composition were used to measure concentrations in the dry ground samples. Multiple linear regressions were then used to derive equations relating spectral measurements of the fresh samples to constituent concentration. Results suggest that these constituents can be measured in fresh foliage samples using high resolution near infrared reflectance spectroscopy. 1.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.