Treesearch

The earth's climate has undergone dramatic and long-term changes through natural processes many millennia before humans influenced global climate. Considerable evidence indicates that increasing concentrations of carbon dioxide and other greenhouse gases in the earth's atmosphere will lead to near-term warming, perhaps as much as 2 to 4°C in northeastern North America. Given that the distribution of vegetation on earth has varied with past climate change, it is reasonable to expect that future climate change will affect forest composition and distribution.

Net primary production (NPP) is defined as the rate at which carbon (C) is accumulated by autotrophs and is expressed as the difference between gross photosynthesis and autotrophic respiration. NPP is the resource providing for the growth and reproduction of all heterotrophs on Earth; as a result, it determines the planet's carrying capacity (Vitousek et al., 1986). For humans, terrestrial NPP is important because it is one determinant of the available food and wood supplies, and because it drives the rates of most other processes identified as "ecosystem services" provided by terrestrial...

General circulation models (GCMs) predict dramatic future changes in climate for the northeastern and north central United States under doubled carbon dioxide (CO2) levels (Hansen et al., 1984; Manabe and Wetherald, 1987; Wilson and Mitchell, 1987; Cubasch and Cess, 1990; Mitchell et al., 1990). January temperatures are projected to rise as much as 12°C and July temperatures as much as 9°C over temperatures simulated at ambient C02 (Kittel et al., 1997). Projections of precipitation are quite variable over the region, ranging from 71 to 177% of ambient levels in January and 29 to 153% of...

Global climate chagnge is a complex and controversial subject, both technically and politically. Recently, the Intergovernmental Panel on Climate Change (IPCC) of the United Nations concluded that "the balance of evidence suggests a discernible human influence on global climate" and that "further accumulation of greenhouse gases will commit the earth irreversibly to global climate change with its consequent ecological, economic, and social disruption" (Houghton et al., 1996: Brown et al., 1997; Kerr, 1997). One of the concerns is that changing climate will have major effects on future...

One of the most important factors impacting terrestrial and aquatic ecosystems is the atmospheric environment. Climatic and weather events play a significant role in governing the natural processes that occur in these ecosystems. The current characteristics of the vast number of ecosystems that cover the northeast and north central United States are, in part, the result of climate, weather, disturbance, and atmospheric pollution patterns that exist in the northeast and north central United States.

The forests of the northern United States support a rich mix of floral and faunal communities that provide inestimable benefits to society. Today's forests face a range of biotic and abiotic stressors, not the least of which may be environmental change. This chapter reviews the compositional traits of presettlement forests and traces the major land use patterns that led to the development of contemporary forested ecosystems.

There is great diversity in the structure and function of the northern forest across the 20-state portion of the United States considered in this book. The interplay of many factors accounts for the mosaic of ecological regimes across the region. In particular, climate, physiography, geology, and soils influence dominance and distribution of vegetation communities across the region. This chapter provides a review of the ecology of the northern forest, emphasizing the role of geology and soils.

Daniel Rutherford is credited with the discovery of nitrogen (N) in 1772. A.L. Lavoisier, the 18th century French chemist, called this element "azote" which translates to "without life" because free N is incapable of supporting life: a fitting name for this element given the paradoxes it presents to society and its role in global ecology.

Decline diseases are intimately linked to stress and environmental change. There is strong evidence that, as a category, decline diseases have increased significantly in response to the climate, air chemistry, and other changes documented in the northeastern United States over the past century, and particularly the last two decades. No other forest response to environmental change and stress is expected to be as dramatic.

Concerns over declining songbird populations have led to investigations of effects of various timber management practices on breeding songbirds. We assessed the influence of 2 types of practices, two-age and clearcutting, on invertebrate biomass and avian daily nest survival in the Monongahela National Forest of West Virginia during summers of 1995 and 1996. We also examined relationships between invertebrate biomass, avian daily nest survival, and wood thrush (Hylocichla mustelina) nestling growth rates.