Vegetation Based Assessment of Wetland Condition in the Prairie Pothole Region

Abstract

The northern prairie pothole region (NPPR) in central and southern Alberta contains numerous shallow, open-water pothole wetlands that provide important ecosystem services to the region, such as flood mitigation. To address the ongoing destruction of these systems, the Alberta government has put forth a new wetland policy to mitigate wetland loss and mandate wetland restoration to offset wetland loss. However, to evaluate the success of wetland restoration a tool is needed to assess wetland condition. An ideal tool for this management objective is a multimetric index (MMI). Multimetric ecological assessments such as the Index of Biotic Integrity use the responses of a specific biotic group as an indicator of disturbance, alleviating the need for complex direct measures of anthropogenic disturbance. Multimetric indices are used throughout the world to assess the condition of several ecosystems, and are applicable to wetlands. Wetlands in the NPPR have unique vegetation that is responsive to anthropogenic disturbance. I hypothesize that both the floristic attributes of wetland vegetation in this region and the distinct patterns of vegetation zonation could be used to produce a multimetric index that reliably indicates the condition of wetlands in agricultural areas. Seventy-two wetlands were sampled in central and southern Alberta in the summer of 2014 and 2015. Each wetland had its vegetation communities delineated and mapped using an SX Blue II GPS/GLONASS receiver to create spatial metrics. Vegetation quadrats were used to obtain floristic metrics related to percent cover, species richness and species traits. Using these metrics, I tested both the traditional method and random selection method of building an MMI. I successfully developed and validated MMIs for wetlands in central and southern Alberta using both floristic and spatial attributes of wetland vegetation. In addition, I was able to demonstrate that a random metric selection method, which allows metrics with weak relationships to disturbance to be incorporated generated a more sensitive MMI than the traditional method, which includes only the metrics most strongly related to disturbance. Both of these multimetric indices can be used to monitor wetland conditions and evaluate the success of wetland restoration projects in Alberta, directly addressing the needs of the government of Alberta to meet the conditions of their wetland policy. The spatial index is the first step in scaling towards a remote sensing approach in performing wetland assessments with an MMI. My work will assist wetland monitoring in Alberta and can be used to guide restoration practitioners in their efforts to create natural wetlands.