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Structural Equation Modeling Of Dynamics Of Nitrate Contamination In Groundwater, Zhi-Jun Liu, George R. Hallberg, George P. Malanson
Structural Equation Modeling Of Dynamics Of Nitrate Contamination In Groundwater, Zhi-Jun Liu, George R. Hallberg, George P. Malanson
George P Malanson
Most research on the temporal aspect of nitrate pollution in water resources has focused on surface water. Comprehensive studies on the dynamics of nitrate in ground water are lacking, especially on a drainage basin scale and for relatively long periods of time. In this study, structural equation modeling is applied in investigating the influences of climate, hydrology, and nitrogen management in agricultural production on nitrate concentration in the Big Spring Basin, Iowa, over a 10-year period. The study shows that for given hydrogeological settings, nitrogen management practices and climate are the two most important factors that affect nitrate dynamics. The …
Post-Fire Succession In Californian Coastal Sage Scrub: The Role Of Continual Basal Sprouting., George P. Malanson, W. E. Westman
Post-Fire Succession In Californian Coastal Sage Scrub: The Role Of Continual Basal Sprouting., George P. Malanson, W. E. Westman
George P Malanson
Dominant shrub species of coastal sage scrub in coastal southern Cali- fornia are able to produce shoots from their base on a continual basis in the absence of fire or other major defoliation. As a result, each shrub becomes a population of mixed-aged branches (ramets) and extends its duration in the canopy beyond the age of any of its above-ground phytomass, reduces the incidence of senescence, and per- mits an individual (genet) to survive during long fire-free intervals. A computer sim- ulation of succession in coastal sage scrub under differing fire intervals shows that continual basal sprouting may be significant …
Improving Environmental Simulation Models To Assess Climate Change Impacts, George P. Malanson, Marc P. Armstrong
Improving Environmental Simulation Models To Assess Climate Change Impacts, George P. Malanson, Marc P. Armstrong
George P Malanson
Increased levels of atmospheric carbon dioxide and other by-products of human civilization are expected to disrupt the global energy budget and induce climatic change, which will aIter the distribution of plant species and the composition of plant communities. In spite of the importance of these projected effects, our understanding of the processes leading to such changes needs to be strengthened. This paper addresses the need to improve models that are used to assess spatial aspects of the response of vegetation to anthropogenic climate change. Several modifications are suggested, each of which relates to changes in forest community composition that occur …
Woody Debris, Sediment, And Riparian Vegetation Of A Subalpine River, Montana, Usa., George P. Malanson, D. R. Butler
Woody Debris, Sediment, And Riparian Vegetation Of A Subalpine River, Montana, Usa., George P. Malanson, D. R. Butler
George P Malanson
No abstract provided.
Farm Chemicals As Indicators Of Sediment Sources In Iowa Rivers, George P. Malanson, E. N. Nealson
Farm Chemicals As Indicators Of Sediment Sources In Iowa Rivers, George P. Malanson, E. N. Nealson
George P Malanson
Determination of the source of sediment in rivers and streams is important in order to effectively implement a program to reduce its concentration. This project uses agricultural chemicals as indicators of current sources of sediment from farm fields in the Cedar River, Iowa watershed. We hypothesized that the relations of sediment, nitrogen, and phosphorous yields to precipitation would indicate whether sediment originated from erosion of fields or from channel bank erosion of floodplains. The changes in sediment, nitrate, and phosphorus in the channel in response to rainfall events were determined. In simple regressions, all three variables have similar slopes when …
Ordination Of Woody Vegetation In A Ouachita National Forest Watershed, George Malanson, Denise Marion
Ordination Of Woody Vegetation In A Ouachita National Forest Watershed, George Malanson, Denise Marion
George P Malanson
Species response to competition and other environmental gradients has important implications for forest ecosystem managers who desire to both maintain diversity and provide a sustained flow of forest goods and services. Woody species on a 140-acre watershed in the Ouachita National Forest are ordinated with detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) to identify the important influences on species distribution at this scale. Species composition is found to respond primarily to a moisture gradient, and secondarily to competition with shortleaf pine (Pinus echinata Mill.). Centrifugal organization of species along gradients is suggested by the relative locations of species …
Reinterpretation Of Relations Between Vegetation Removal And Water Yield, George P. Malanson, D. P. Post
Reinterpretation Of Relations Between Vegetation Removal And Water Yield, George P. Malanson, D. P. Post
George P Malanson
While the relation between vegetation clearance and increasing streamflow appears to be strong for data aggregated among geographic regions, results are equivocal in local areas. Earlier data are re-analyzed to consider the role of hydroclimatology. While vegetation clearance increases absolute streamflow, the proportional change is not significant. Residuals of regressions of absolute and proportional change in streamflow on vegetation clearance are related to precipitation, with positive and negative slopes, respectively. A few outliers with high responses are important in creating a pattern, and hydroclimatology is a better predictor of change in streamflow than is vegetation clearance for aggregate data. With …
Geomorphic Determinants Of Species Composition Of Alpine Tundra, Glacier National Park, U.S.A., George P. Malanson
Geomorphic Determinants Of Species Composition Of Alpine Tundra, Glacier National Park, U.S.A., George P. Malanson
George P Malanson
Because the distribution of alpine tundra is associated with spatially limited cold climates, global warming may threaten its local extent or existence. This notion has been challenged, however, based on observations of the diversity of alpine tundra in small areas primarily due to topographic variation. The importance of diversity in temperature or moisture conditions caused by topographic variation is an open question, and we extend this to geomorphology more generally. The extent to which geomorphic variation per se, based on relatively easily assessed indicators, can account for the variation in alpine tundra community composition is analyzed versus the inclusion of …
Mountain Treelines: A Roadmap For Research Orientation, George P. Malanson
Mountain Treelines: A Roadmap For Research Orientation, George P. Malanson
George P Malanson
For over 100 years, mountain treelines have been the subject of varied research endeavors and remain a strong area of investigation. The purpose of this paper is to examine aspects of the epistemology of mountain treeline research—that is, to investigate how knowledge on treelines has been acquired and the changes in knowledge acquisition over time, through a review of fundamental questions and approaches. The questions treeline researchers have raised and continue to raise have undoubtedly directed the current state of knowledge. A continuing, fundamental emphasis has centered on seeking the general cause of mountain treelines, thus seeking an answer to …