Flooding-induced landscape changes along dendritic stream networks and implications for wildlife habitat.

摘要

Severe low frequency natural disturbances along stream networks can substantially alter urban and rural landscapes and impact habitat and population dynamics of wildlife species. In 1978, severe flooding along the North Prong of the Medina River significantly altered the habitat for the Rio Grande wild turkey and may have contributed to the decreased abundance of this species observed during recent decades in the southeastern Edwards Plateau, TX, USA. The objective of our study was to examine the changes in landscape structure caused by this flooding event and their potential impact on wild turkey habitat. Aerial photography from 1972, 1984, and 1995 was used to quantify habitat changes in riparian zones and adjacent bottomlands along the Medina River. We documented substantial reductions in habitat suitability and connectivity caused by the flooding, followed by a partial recovery over 17 years. Analysis using patch-level metrics in conjunction with class-level metrics, provided insights to the pattern and possible mechanisms of the landscape changes. Habitat along higher-order streams was most affected, reducing not only the suitable habitat locally, but also the habitat connectivity throughout the riparian network. This loss of connectivity rendered numerous habitat patches along lower-order streams unavailable to Rio Grande wild turkeys as this species depends on riparian corridors for dispersal and movement among habitat patches. Our results illustrate the critical importance of multiple-scale analysis based on hierarchical dendritic structures of river networks when assessing habitat changes and their impact on populations of terrestrial wildlife species dependent on riparian habitats in semi-arid landscapes.