Date of Award

January 2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Earth System Science & Policy

First Advisor

Jeffery A. VanLooy

Abstract

Terrestrial orchids are at the forefront of the discussion about anthropogenically-driven extinction with more species threatened globally than any other plant family, mostly because of loss of habitat. The Western Prairie Fringed Orchid (Platanthera praeclara) is a threatened species found on the Sheyenne National Grassland in southeast North Dakota, USA. This conservation area that is a vital refuge for this species is subject to management for multiple uses including livestock grazing and recreation. Orchids are subject to continuous monitoring, but knowledge of the relationship between landscape indicators and orchid locations is limited. Research is needed to provide a greater understanding of the landscape relative to orchid habitat to develop conservation management strategies suited to dealing with threats arising from future interactions between land management and use, and climate change.

The spatial distribution of orchid habitat was defined using a suite of indicators that characterize topography, moisture, and vegetation cover and compared with orchid point-based field observations. High resolution infrared imagery, a LiDAR-derived DEM, and well observations were used to characterize landscape properties. The NDVI (a measure of vegetation cover), the Topographic Wetness Index (TWI: a measure of moisture on the landscape), the Topographic Position Index (TPI: a measure of position on the landscape), and the depth to groundwater (a measure of the depth from the land surface to the groundwater surface) provided the best set of indicators of orchid habitat. Comparison between orchid locations and landscape indicators identified orchid metrics (±2 σ) used to classify landscape indicators which were combined to create orchid habitat maps.

This study supports that distribution of orchid habitat are influenced by the selected landscape indicators, each providing important information to the analysis. Comparison of orchid metrics with groundwater elevations showed that orchids generally occurred on average 1.01 ±0.43 (2σ) meters above the water table. TWI and TPI demonstrated that orchids occur near margins of flow paths and near foot and toe slopes of slight elevations changes. NDVI classified vegetation cover and excluded agricultural land use. Landscape-scale analysis of orchid habitat identifies areas most in need of protection or restoration, and monitoring.

Download

Share

COinS