Post-settlement changes in the northwest Wisconsin sand plain: Vegetation, soil and the landscape mosaic.

摘要

The underlying theme of this dissertation is disturbance ecology. I address a variety of questions relating to how disturbances shape plant communities, soil and landscapes within the northwest Wisconsin sand plain. This work addresses this region because of its active disturbance history and its conservation value. The sandy soils and fire history generated pine barrens vegetation, a globally rare habitat type that is now threatened by fire suppression.; The first chapter includes a literature review discussing disturbance ecology with respect to vegetation, landscape pattern, history and scale. The second chapter reports findings from a field study of how patterns in vegetation disturbance legacies in the sand plain. It focuses primarily on vegetation and illustrates a very strong agricultural legacy, but only a weak effect from the wildfire that I studied. The third chapter discusses patterns in soil properties. Again, I observed a strong agricultural legacy and a weak fire effect. The fourth chapter describes research focused at a broader scale. I use historic airphotos to describe how recent history interacts with and shapes the landscape shifting mosaic. I show that the landscape has grown simpler through time and has lost savanna and woodland habitat. I also discuss the likelihood of future habitat losses given the patch dynamics that I measured. The fifth chapter concludes the dissertation with a discussion of how the three research components relate to one-another. I discuss plant-soil feedbacks as a mechanism for maintaining land use legacies and explore how they may influence landscape-scale patterns. I then discuss how cross-scale interactions between landscape structure and local vegetation may shape regional plant diversity. Finally, I address the management implications of these findings.