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HYDROLOGY AND LANDSCAPE CONNECTIVITY OF VERNAL POOLS
Citation:
LEIBOWITZ, S. G. AND R. T. BROOKS. HYDROLOGY AND LANDSCAPE CONNECTIVITY OF VERNAL POOLS. Chapter 3, A.J.K. Calhoun and P.G. deMaynadier (ed.), Science and Conservation of Vernal Pools in Northeastern North America. CRC Press - Lewis Publishers, Boca Raton, FL, , 31-53, (2008).
Impact/Purpose:
Discussion of hydrology and landscape connectivity of vernal pools.
Description:
Vernal pools are shaped by hydrologic processes which influence many aspects of pool function. The hydrologic budget of a pool can be summarized by a water balance equation that relates changes in the amount of water in the pool to precipitation, ground- and surface-water flows, and evapotranspiration. For many vernal pools, precipitation and evapotranspiration are the major determinants of the water cycle. However, ground water can also be significant in specific settings and at particular times. Surface-water flows can be important for certain vernal pools, e.g., those in riverine settings. Basin and catchment characteristics influence the relative role of surface and ground water. A limited number of vernal pools may have permanent surface-water connections to other waters. Intermittent surface-water connections may also occur during episodic events, either annually or less frequently. It is suggested that these intermittent surface-water connections result in a spatial and temporal hierarchy of hydrologic interactions. Thus vernal pools occur within an isolation-connectivity continuum over time and space. Theory suggests that the persistence of a species across vernal pools represents a balance between factors that cause local extinctions and those that allow for unoccupied areas to be recolonized. Landscape connectivity makes it possible for species to disperse between vernal pools and recolonize pools that are unoccupied due to local extinctions. Connectivity is greater for species with larger dispersal distances and in landscape settings with greater pool densities. In addition to connections between pools, migratory species also require landscape connectivity between pools and other core habitat areas, such as forests. While flooding and drawdown exhibit significant temporal variability from year-to-year, any impacts that have a long-term effect on the frequency, duration, magnitude, or variability of flooding will inevitably alter community composition. These impacts, which range in scale from impacts to individual pools to large-scale effects throughout the entire glaciated northeast, include timber harvesting, land development, and climate change.