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In the shadows of an old-growth forest, Eric Forsman looked into the dark eyes of a spotted owl. He placed a live mouse on a branch, offering the bird a free lunch. “Mousing” is a strategy he and other biologists have used for decades to help unravel the mysteries of the owl's behavior and ecology. A mated male will carry the mouse to his partner; if there are owlets in the nest, she will bring the food to them.
A central goal of evolutionary ecology is to understand the role of different ecological processes in producing patterns of macroevolutionary diversification. Theory and empirical evidence have shown that competition between existing species can promote evolutionary diversification through ecological character displacement and, more recently, that competition may play a role both in producing species and in driving their subsequent evolutionary divergence. However, recent theory and experiments suggest that other ecological interactions, such as facilitation, may also be important in the evolutionary diversification of some taxa. Future research in this area will be invaluable in dissecting the relative roles of different ecological processes in producing and maintaining biodiversity.
Interactions between climate and ecosystems with complex topographic gradients generate unique source and sink habitats for water and nutrients as a result of precipitation, energy, and chemical redistribution. We examined these phenomena for a high-elevation site in the Colorado Front Range. Current changes in climate and atmospheric deposition of nitrogen to these systems are causing rapid changes in some portions of this system but not in others. Using a conceptual model that links terrestrial ecosystems to each other and to aquatic ecosystems, we report how atmospheric inputs and endogenous resources can be amplified or attenuated by transport processes. High-elevation lakes and the alpine tundra–forest ecotone are expected to receive the brunt of anthropogenic inputs obtained from (a) the redistribution of exogenous materials from the regional environment and (b) endogenous sources originating in other montane areas.
We compared the historic and current geographical ranges of 43 North American carnivores and ungulates to identify large-scale patterns in range contractions and expansions. Seventeen of the species had experienced range contractions over more than 20% of their historic range. In areas of higher human influence, species were more likely to contract and less likely to persist. Species richness had also declined considerably since historic times. The temperate grasslands and temperate broadleaf–mixed forest biomes lost the highest average number of species, while the boreal forest and tundra showed fewer numbers of species lost. Species contractions were a result of Euro-American settlement and postsettlement development in North America. These effects have been widespread and indicate a rapid collapse of species distributions over the course of only 1 to 2 centuries. The results of this study can be used to improve scientists' knowledge of historical reference conditions and to provide input for wildlife reintroductions and for the creation of wildlife reserves.
The great challenge now facing forest ecosystem scientists and managers is to address the need for multiple ecosystem services over relatively large spatial and temporal scales (e.g., whole national forests over 50- to 100-year time frames). Here we present a new conceptual model for the study of forest ecosystems that aids in the analysis of factors that influence ecosystem structure, function, and services. We then go on to show how this model has been applied to the long-term Hubbard Brook Ecosystem Study. Our new model has three main components: (1) controllers, (2) ecosystem pattern and process, and (3) ecosystem functions and services. The controllers are the factors that drive ecosystem pattern and process; we split them into two groups, state factors and variable–stochastic factors. This new model will help to ensure a comprehensive approach to forest ecosystem analysis and will facilitate interactions of research with policy and management at many locations.
The legacy of Aldo Leopold includes the concept of ethical responsibilities toward the land, and the establishment of ecological restoration both for environmental learning and for land management. For more than a half-century, the land ethic has been a major paradigm for ethical and environmental thinking.
Conventional water quality standards have been successful in reducing the concentration of toxic substances in US waters. However, conventional standards are based on simple thresholds and are therefore poorly structured to address human-caused imbalances in dynamic, natural water quality parameters, such as nutrients, sediment, and temperature. A more applicable type of water quality standard—a “regime standard”—would describe desirable distributions of conditions over space and time within a stream network. By mandating the protection and restoration of the aquatic ecosystem dynamics that are required to support beneficial uses in streams, well-designed regime standards would facilitate more effective strategies for management of natural water quality parameters.