Abstract
Wetlands provide ecosystem goods and services vitally important to humans. Land managers and policymakers working to conserve wetlands require regularly updated information on the statuses of wetlands across the landscape. However, wetlands are challenging to map remotely with high accuracy and consistency. We investigated the use of multitemporal polarimetric synthetic aperture radar (SAR) data acquired with Canada’s Radarsat-2 system to track within-season changes in wetland vegetation and surface water. We speculated, a priori, how temporal and morphological traits of different types of wetland vegetation should respond over a growing season with respect to four energy-scattering mechanisms. We used ground-based monitoring data and other ancillary information to assess the limits and consistency of the SAR data for tracking seasonal changes in wetlands. We found the traits of different types of vertical emergent wetland vegetation were detected well with the SAR data and corresponded with our anticipated backscatter responses. We also found using data from Landsat’s optical/infrared sensors in conjunction with SAR data helped remove confusion of wetland features with upland grasslands. These results suggest SAR data can provide useful monitoring information on the statuses of wetlands over time.
Highlights
Wetlands provide ecosystem goods and services vitally important to humans, including food, fiber, filtering of contaminants, sediment storage, flood control, wildlife habitat, recreation, aesthetic value, and others [1]
We focused our analysis on a set of wetland vegetation types for which we anticipated specific characteristics of synthetic aperture radar (SAR) energy scattering over the growing season, based on the interplay between surface water and types of vertical emergent vegetation found in the Tamarac National Wildlife Refuge (NWR) (Table 1)
We addressed errors associated with confusing wetlands with upland grasslands by applying the near-infrared band filters we developed from best-match dates of Landsat data (Figure 5)
Summary
Wetlands provide ecosystem goods and services vitally important to humans, including food, fiber, filtering of contaminants, sediment storage, flood control, wildlife habitat, recreation, aesthetic value, and others [1]. Many of these goods and services are realized at the local scale, but wetlands provide important services at broader scales. U.S and Canadian collaborators in the Terrestrial Wetland Global Change Research Network (TWGCRN [5]) are studying how key ecological conditions in wetland-upland landscapes change in relation to climate and land cover One goal of this effort is to understand how intra- and interannual variations in precipitation and temperature relate to changes in landscape moisture availability, primary productivity, wetland habitat, and animal calling phenology and site occupancy over different temporal and spatial scales, and to assess how these conditions likely will change in the future. Resource managers and policymakers need such information to try to maintain the ecosystem services these landscapes provide in the face of global change (e.g., [6])
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