Large-extent ice storms have received relatively little attention from researchers. This research investigates the effects of abiotic and biotic factors on the spatial patterns of ice storm disturbance on a forested landscape. This investigation provides a landscape-level perspective on the impacts of ice storm disturbance, clarifies the effects on ecosystem dynamics, and will aid future forest management plans. The study was conducted in Ouachita National Forest (ONF) in west-central Arkansas and southeastern Oklahoma and examined approximately 6000 km2 of forest between 150 and 800 m elevation. Normalized Difference Vegeation Index (NDVI) difference values were calculated using two Landsat 7 ETM+ scenes to identify NDVI changes that potentially were associated with ice storm damage to the forests. Forty-six geolocated field sites were used to determine the relationship of NDVI difference to actual forest damage caused by the ice storm by counting the number of downed tree boles intersecting a 100 m transect. These field sites encompassed a broad range of each of the physical variables (i.e. elevation, slope, and aspect), forest type, and degree of damage. The linear regression model determined the relationship between NDVI difference and ice storm damage. Elevation, slope, and aspect were calculated based on individual pixels from the DEM. Categories of forest damage were based on NDVI difference values. A chi-square test of correspondence and Cramer’s V test were then used to analyze relationships of damage to abiotic and biotic variables. The strong, negative relationship observed in the linear regression model suggested that NDVI was representative of ice storm damage in the study area. The chi-square test of correspondence indicated the abiotic and biotic variables all had associations with NDVI difference results (p<0.001). The Cramer’s V test established that elevation had the strongest influence on the degree of ice storm damage followed closely by slope and aspect. Moderate elevations, moderate slopes, and windward aspects received the highest percentage of major storm damage. Forest type displayed a weak relationship with the extent of damage. The topographic patterns of ice storm damage are similar to patterns found in previous research. Topography influenced spatial patterns of ice storm damage. Elevation, slope, and aspect were all found to be important variables influencing the degree of ice storm damage. Knowledge concerning these spatial patterns is critical for future studies of ecosystem dynamics and forest management practices.

Large-extent ice storms have received relatively little attention from researchers. This research investigates the effects of abiotic and biotic factors on the spatial patterns of ice storm disturbance on a forested landscape. This investigation provides a landscape-level perspective on the impacts of ice storm disturbance, clarifies the effects on ecosystem dynamics, and will aid future forest management plans. The study was conducted in Ouachita National Forest (ONF) in west-central Arkansas and southeastern Oklahoma and examined approximately 6000 km2 of forest between 150 and 800 m elevation. Normalized Difference Vegeation Index (NDVI) difference values were calculated using two Landsat 7 ETM+ scenes to identify NDVI changes that potentially were associated with ice storm damage to the forests. Forty-six geolocated field sites were used to determine the relationship of NDVI difference to actual forest damage caused by the ice storm by counting the number of downed tree boles intersecting a 100 m transect. These field sites encompassed a broad range of each of the physical variables (i.e. elevation, slope, and aspect), forest type, and degree of damage. The linear regression model determined the relationship between NDVI difference and ice storm damage. Elevation, slope, and aspect were calculated based on individual pixels from the DEM. Categories of forest damage were based on NDVI difference values. A chi-square test of correspondence and Cramer’s V test were then used to analyze relationships of damage to abiotic and biotic variables. The strong, negative relationship observed in the linear regression model suggested that NDVI was representative of ice storm damage in the study area. The chi-square test of correspondence indicated the abiotic and biotic variables all had associations with NDVI difference results (p<0.001). The Cramer’s V test established that elevation had the strongest influence on the degree of ice storm damage followed closely by slope and aspect. Moderate elevations, moderate slopes, and windward aspects received the highest percentage of major storm damage. Forest type displayed a weak relationship with the extent of damage. The topographic patterns of ice storm damage are similar to patterns found in previous research. Topography influenced spatial patterns of ice storm damage. Elevation, slope, and aspect were all found to be important variables influencing the degree of ice storm damage. Knowledge concerning these spatial patterns is critical for future studies of ecosystem dynamics and forest management practices.

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Thesis (M.P.A.)--Missouri State University, 2008. / "May 2008." Includes bibliographical references (leaves 159-163). Also available online.

Climate change can alter ecosystem processes and organismal phenology through both long-term, gradual changes and alteration of disturbance regimes. Because microbes mediate decomposition, and therefore the initial stages of nutrient cycling, soil biogeochemical responses to climate change will be driven by microbial responses to changes in temperature, precipitation, and pulsed climatic events. Improving projections of soil ecological and biogeochemical responses to climate change effects therefore requires greater knowledge of microbial contributions to decomposition. This dissertation examines soil microbial and biogeochemical responses to the long-term and punctuated effects of climate change, as well as improvement to decomposition models following addition of microbial parameters. First, through a climate change mesocosm experiment on two soils, I determined that biogeochemical losses due to warming and snow reduction vary across soil types. Additionally, the length of time with soil microbial activity during plant dormancy increased under warming, and in some cases decreased following snow reduction. Asynchrony length was positively related to carbon and nitrogen loss. Next, I examined soil enzyme activity, carbon and nitrogen biodegradability, and fungal abundance in response to ice storms, an extreme event projected to occur more frequently under climate change in the northeastern United States. Enzyme activity response to ice storm treatments varied by both target nutrient and, for nitrogen, soil horizon. Soil horizons often experienced opposite response of enzyme activity to ice storm treatments, and increasing ice storm frequency also altered the direction of the microbial response. Mid-levels of ice storm treatment additionally increased fungal hyphal abundance. Finally, I added explicit microbial parameters to a global decomposition model that previously incorporated climate and litter quality. The best mass loss model simply added microbial flows between litter quality pools, and addition of a microbial biomass and products pool also improved model performance compared to the traditional implicit microbial model. Collectively, these results illustrate the importance of soil characteristics to the biogeochemical and microbial response to both gradual climate change effects and extreme events. Furthermore, they show that large-scale decomposition models can be improved by adding microbial parameters. This information is relevant to the effects of climate change and microbial activity on biogeochemical cycles.

Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2003. / Bibliogr.: f. 182-187. Document électronique également accessible en format PDF. CaQCU

I investigated the impacts of a catastrophic ice storm on the old-growth, hardwood forests of Mont St. Hilaire, Quebec. The mass of litter resulting from the ice storm of January 1998 was estimated using equations relating the basal diameter of fallen branches with branch mass for each of the ten major species. The ice storm of January 1998 produced 19.9 metric tonnes or 33.6 m3 of woody-litter per hectare. These losses of woody biomass are approximately 20 times greater than what is expected in a normal year and correspond to between 7--10% of the total above-ground biomass of the prestorm forest. This level of litter production positions the ice storm of 1998 as the most severe ice storm on record and amongst the most powerful forms of climatic disturbance experienced in forested ecosystems. / I also investigated differences in the magnitude and nature of the biomass losses sustained by each study species. While the magnitude of biomass lost by the study species was not related to either wood strength or stiffness, the nature of the biomass lost was. All species primarily lost branches less than 5 cm in diameter, but it was the relatively few branches greater than this diameter that accounted for the majority of downed biomass. Smaller branches were lost in relation to differences in species-specific mechanical properties, while larger branches appear to be lost in response to weakening by decay and other age-dependent factors. The ecological and evolutionary implications of these results emphasise the need for an analysis of the interplay between mechanical properties and canopy architecture in determining overall susceptibility to ice damage.

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