Hydrological influences on ecological zonation in a salt marsh tidal creek basin: Crab Haul Creek, South Carolina, USA.

摘要

Ecological zones in a salt marsh are controlled by many factors, including hydroperiod, elevation, soil salinity, groundwater flow, competition, and nutrient/oxygen availability. The primary driving factor(s) are still debated, but most models of zonation consider elevation or hydroperiod as the key factor. This project is designed to gather high-resolution aerial images from a helium balloon kite (Helikite) to improve our understanding of the influence of hydroperiod on zonation. The Helikite was used to capture aerial photographs of Crab Haul Creek Basin, the most landward salt marsh basin in North Inlet, South Carolina. Near-IR photographs were taken from 75-100m altitude to resolve the waterline during rising tide from the headwaters to a tide gauge located 150m north. We used Helikite visual light images and automated classification to identify ecological zones. Photographs taken during peak primary production have distinct pixel RGB values for the main ground cover types. After creating a signature file based on each ground covers distinct pixel signature, maximum likelihood pixel-based computerized classification was applied. By quantifying the hydroperiod and comparing it to ecological zones we found that elevation and hydroperiod do not solely explain zonation. Other factors must be considered important, particularly groundwater flow and evapotranspiration.