Current Global Change Projects

Project Title: Effect of Climate Change on Population Trajectories and Trophic Interactions in a High Elevation Riparian Ecosystem

Principal Investigator: Thomas E. Martin, USGS Montana Cooperative Wildlife Research Unit

Introduction

The International Panel of Climate Change 2001 report pointed out that our understanding of the consequences of climate change for ecosystems is weak, and improved understanding remains a critical priority.  Predictions of climate consequences span an entire gradient.  At one end, it is argued that climate change may have minimal impacts on ecosystems because communities will simply adapt and migrate intact.  At the other end, it is argued that organisms will differ in their ability to adapt to climate change, which will lead to extinctions and significant changes in ecosystem structure and function.  Moreover, since communities are not simply the sum of their individual parts, climate can have cascading effects on ecosystems: climate-induced alteration of the presence and abundance of species (i.e., ecosystem structure) that are important members of food webs may then cascade to yield changes in additional species and affect ecosystem function.  This study is unique in continuing a long-term (21 year) study of the responses of multiple trophic levels of a high priority ecosystem to changes in multiple aspects of climate (winter snowfall, winter precipitation, spring temperatures, summer precipitation).  It includes a unique and large-scale experiment to examine the interaction of climate and ungulate browsing as a major perturbation of the system.

Research under this project has addressed these issues during long-term (21 years) study of a high elevation riparian system in north-central Arizona.  This is a high priority ecosystem for studying relative to climate variation and change for several reasons.  First, high elevation sites are considered susceptible to abrupt climate changes and of high priority to study.  Second, riparian habitats are hotspots for biodiversity supporting a major portion of western U.S. species and they often serve as a focus of recreational activity.  The riparian habitat studied here is typical of western mountain riparian habitats by supporting a large diversity of organisms, but by occurring in a semi-arid location (i.e., the arid southwest), this system is particularly sensitive to changes in precipitation as outlined below.  Third, the habitats studied under this work occur in National Forest and are critical for multiple resource use, including timber production, grazing, recreation, and support of biodiversity.

This study examines on-going long-term (21 years) ecosystem responses as follows:

1) Phenological responses of bird breeding to warmer spring temperatures.  2) Population response of the riparian plant community to declining winter snowfall.  3) Predation on nests of birds in response to declining summer precipitation.  4) Population responses of birds to changes in vegetation and nest predation in response to climate.  5) Effects of declining winter snowfall on intensity of elk browsing of vegetation.  6) Effects of elk browsing on plant recruitment and population trajectories.

Contact Information

Thomas E. Martin
Montana Cooperative Wildlife Research Unit
University of Montana
Missoula, MT 59812
Phone: 406-243-5372
Fax: 406-243-6064
E-mail: tom.martin@umontana.edu