Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

Browse

Filters

2011 - 20122

Settings

Subject: search.filters.subject.Disturbance

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    TOWARDS A BETTTER UNDERSTANDING OF FOREST CHANGE PROCESSES IN THE CONTIGUOUS U.S.
    (2012) Schleeweis, Karen; Goward, Samuel N.; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Estimates of forest canopy areal extent, configuration and change have been developed from satellite based imagery and ground based inventories to improve understanding of forest dynamics and how they interact with other earth systems across many scales. The number of these types of studies has grown in recent years. Yet, few have assessed the multiple change processes underlying observed forest canopy dynamics across large spatio-temporal extents. To support these types of assessments, a more detailed and integrated understanding of the geographic patterns of the multiple forest change processes across the contiguous US (CONUS) is needed. This study examined a novel data set from the North American Forest dynamics (NAFD) project that provides a dense temporal record (1984-2005) of forest canopy history across the U.S., United States Forest Service (USFS) ground inventory data, and ancillary geospatial data sets on forest change processes (wind, insect, fire, harvest and conversion to suburban/urban land uses) across the CONUS to develop a more robust understanding of the implications of the shifting dynamics of forest change processes and our ability to measure their effect on forest canopy dynamics. A geodatabase of forest change processes was created to support synoptic and specific quantitative analysis of change processes support through space and time. Using the geodatabase, patterns of forest canopy losses from NAFD and USFS data and the underlying causal process were analyzed across multiple scales. This research has shown that the overlap of multiple disturbance processes leads to complex patterns across the nation's forested landscape that can only be fully understood in relation to forest canopy losses at fine scales. Regional statistics confounded the direction and magnitude of forest canopy loss from multiple change processes operating on the landscape. Data gaps and uncertainty associated with process data prevent a full quantitative analysis of the proportion of forest area affected by each forest change process considered here. Fine scale data were critical for interpreting the highly variable NAFD canopy change observations and their ability to capture the continuously changing spatial and temporal characteristics of forest change processes across the CONUS.
  • Thumbnail Image
    Item
    PLANT PRODUCTIVITY AND COMPETITIVE RESPONSE TO PRESCRIBED FIRE IN MID-ATLANTIC BRACKISH MARSHES
    (2011) Bickford, Wesley Alan; Needelman, Brian A; Weil, Raymond R; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Prescribed fire may increase productivity of some brackish marsh species. An understanding of the mechanisms behind this stimulatory effect is important for land managers to maximize the benefits to the ecosystem. I found that canopy removal is the dominant mechanism through which fire stimulates biomass production in the marshes at the Blackwater National Wildlife Refuge in Dorchester County, Maryland. The stimulatory effect of canopy removal was stronger in sedge-dominated systems than grass-dominated systems. Faster sprouting sedge species may be able to take fuller advantage of light and soil temperature increases following canopy removal than later-sprouting grass species. Results of a greenhouse study indicated that canopy removal gives sedges a competitive advantage over grasses. These studies have numerous implications for land managers using anthropogenic disturbances as a management technique. Canopy-level disturbances, such as fire may increase productivity in sedge-dominated marshes and may suppress grass species in mixed compositions.