53 research outputs found
Assessing the Potential Impacts to Riparian Ecosystems Resulting from Hemlock Mortality in Great Smoky Mountains National Park
Hemlock Woolly Adelgid (Adelges tsugae) is spreading across forests in eastern North America, causing mortality of eastern hemlock (Tsuga canadensis [L.] Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.). The loss of hemlock from riparian forests in Great Smoky Mountains National Park (GSMNP) may result in significant physical, chemical, and biological alterations to stream environments. To assess the influence of riparian hemlock stands on stream conditions and estimate possible impacts from hemlock loss in GSMNP, we paired hardwood- and hemlock-dominated streams to examine differences in water temperature, nitrate concentrations, pH, discharge, and available photosynthetic light. We used a Geographic Information System (GIS) to identify stream pairs that were similar in topography, geology, land use, and disturbance history in order to isolate forest type as a variable. Differences between hemlock- and hardwood-dominated streams could not be explained by dominant forest type alone as forest type yields no consistent signal on measured conditions of headwater streams in GSMNP. The variability in the results indicate that other landscape variables, such as the influence of understory Rhododendron species, may exert more control on stream conditions than canopy composition. The results of this study suggest that the replacement of hemlock overstory with hardwood species will have minimal impact on long-term stream conditions, however disturbance during the transition is likely to have significant impacts. Management of riparian forests undergoing hemlock decline should, therefore, focus on facilitating a faster transition to hardwood-dominated stands to minimize long-term effects on water quality
Toward an integration of landscape and food web ecology: The dynamics of spatially subsidized food webs
We focus on the implications of movement, landscape variables, and spatial heterogeneity for food web dynamics. Movements of nutrients, detritus, prey, and consumers among habitats are ubiquitous in diverse biomes and can strongly influence population, consumer-resource, food web, and community dynamics. Nutrient and detrital subsidies usually increase primary and secondary productivity, both directly and indirectly. Prey subsidies, by movement of either prey or predators, usually enhance predator abundance beyond what local resources can support. Top-down effects occur when spatially subsidized consumers affect local resources by suppressing key resources and occasionally by initiating trophic cascades. Effects on community dynamics vary with the relative amount of input, the trophic roles of the mobile and recipient entities, and the local food web structure. Landscape variables such as the perimeter/area ratio of the focal habitat, permeability of habitat boundaries, and relative productivity of trophically connected habitats affect the degree and importance of spatial subsidization
Spatial patterns of water quality in Xingu River Basin (Amazonia) prior to the Belo Monte dam impoundment
The importance of sedimenting organic matter, relative to oxygen and temperature, in structuring lake profundal macroinvertebrate assemblages
We quantified the role of a main food
resource, sedimenting organic matter (SOM), relative
to oxygen (DO) and temperature (TEMP) in structuring
profundal macroinvertebrate assemblages in
boreal lakes. SOM from 26 basins of 11 Finnish lakes
was analysed for quantity (sedimentation rates),
quality (C:N:P stoichiometry) and origin (carbon
stable isotopes, d13C). Hypolimnetic oxygen and
temperature were measured from each site during
summer stratification. Partial canonical correspondence
analysis (CCA) and partial regression analyses
were used to quantify contributions of SOM, DO and
TEMP to community composition and three macroinvertebrate
metrics. The results suggested a major
contribution of SOM in regulating the community
composition and total biomass. Oxygen best explained
the Shannon diversity, whereas TEMP had largest
contribution to the variation of Benthic Quality Index.
Community composition was most strongly related to d13C of SOM. Based on additional d13C and stoichiometric
analyses of chironomid taxa, marked differences
were apparent in their utilization of SOM and
body stoichiometry; taxa characteristic of oligotrophic
conditions exhibited higher C:N ratios and lower C:P
and N:P ratios compared to the species typical of
eutrophic lakes. The results highlight the role of SOM
in regulating benthic communities and the distributions
of individual species, particularly in oligotrophic
systems
Limitations to Intellectual Progress in Ecosystem Science
Are ecosystem scientists poised to make great leaps forward in developing understanding, and in applying it to real-world problems? The challenge is to deal simultaneously with the multidimensional complexity of time and space. An intellectual limitation is the false assumption that there will be simple, all-inclusive answers to complex, ecological questions, whereas the elegance of creative, innovative thought and approach is to discover ways to simplify questions or systems being studied to obtain fundamental, inclusive answers. Ecology must be an integrative science and will flourish from creative integration and synthesis. How are vision and creativity enhanced? Is the rate of breakthroughs in ecosystem science appropriate for a healthy, robust scientific field? Teams and team-building are critical components of successful ecosystem science, but efforts should be made to promote inter-disciplinary teams. There is a continuing need to attract the brightest and best into ecosystem science by utilizing the popularity of the ecosystem concept, the challenge of solving complex problems, and the awareness of how such solutions are of value to humanity. More undergraduate courses, textbooks, and scientific journals focused on ecosystem science are needed, however time limitations have become serious problems for scientists. Being busy is good, but if being busy leads to fragmentation of effort, loss of focus, superficial scholarship, and inability to meet commitments, then being busy represents a major intellectual limitation. The weak connection between ecosystem science and policy in the United States is frustrating, primarily because of fragmentation of approach and implementation. However, many opportunities exist for intellectual progress in ecosystem science
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