Doctoral Dissertations
Date of Award
8-1990
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Major
Ecology and Evolutionary Biology
Major Professor
Dewey Bunting
Committee Members
William Emanuel, Lou Gross, Sandy Echtemacht, James Schidhammer, Donald DeAngelis
Abstract
A simulation modeling approach was used to investigate key interactions between landscape heterogeneity, mammalian herbivore behavior, and plant survival. The models used in this investigation follow the fates of individual animals, and sometimes of individual plants, on spatial grids. Ongoing research investigating tree seedling herbivory on utility rights-of-way in New York provided the context for model development, but the framework developed is useful for investigation of herbivore-plant systems in general. Predicting how habitat heterogeneity may affect the habitat preferences of animals is very useful for predicting the level of herbivory. If the use of a particular habitat type leads to significantly lower fitness than a strategy where the type is avoided, then avoidance may be observed in the field. Model simulations suggest that the fitness differential between strategies depends on the spatial distribution of habitat types, but that for wintering ungulates there is little fitness benefit for avoiding inferior habitat types over a wide range of realistic conditions. I also attempted to identify the habitat selection strategy of small mammals in rights-of-way by statistically analyzing data on the consumption of tree seedlings in different habitats. The analysis considered the vegetation patterns on the study site measured at different spatial scales. The data were not consistent with hypothesized scenarios of herbivore behavior, possibly due in part to sampling deficiencies. Also important for predicting herbivory is identifying the implications of herbivore behavioral strategies on the use of space. Model experiments implicated the interactions between spatial pattern, movement strategies, and refuging behavior as primary determinants of herbivore space use. Assessing the effects of these factors for a particular system will be made difficult by the relative lack of data on movement strategies of foragers. Understanding some systems requires consideration of multiple feedbacks between landscape pattern, herbivore behavior, and plant survival. The dynamics of vegetation pattern in forests provides an example of such a case. I used a simple model of pattern generation to explore the published hypothesis that forest gap dynamics can create clumped distributions of shade-tolerant trees. Model results suggest that this is unlikely, and that the observed preference for gap habitats by small mammal herbivores may contribute to the maintenance of random patterns of trees.
Recommended Citation
Hyman, Jeffrey B., "A landscape approach to the study of herbivory. " PhD diss., University of Tennessee, 1990.
https://trace.tennessee.edu/utk_graddiss/11424
