Projects

Species loss/gain and ecosystem structure and function Our work in this area seeks to understand the effects of species losses, due to disease, or species gains, due to invasions, on ecosystem processes across the landscape. Recent and on-going projects focus on the interactive effects of atmopheric nitrogen deposition and hemlock loss due to the exotic hemlock woolly adelgid on nitrogen and phophorus cycling; impacts of an exotic invasive grass on ecosystem processes across environmental and land-use gradients; and invader response to environmental gradients and fire.

 

Terrestrial-aquatic interactions The distribution and configuration of land use and land cover can have important implications for chemical and biological water quality. We have multiple projects underway to evaluate the relative contributions of watershed characteristics to aspects of water quality. Previously, we investigated how the effects of land use on lake chemistry vary in light of differences in the capacity of watersheds to transport materials and water. More recently, we are involved in an effort to evaluate the relative importance of alder trees and salmon for lake and stream chemistry and productivity in southwest Alaska, and to understand the regional controls of DOC flux to aquatic systems.

 

Modeling plant population persistence on stochastic landscapes Using a simple cellular model on binary landscapes, we are investigating the joint effects of habitat fragmentation and temporal stochasiticty on population dynamics. Results to date suggest that the relative influence of habitat configuration on population size far outweighs that of stochasticity in either survival or reproductive output. However, these factors can enhance the negative impacts of fragmentation and further reduce population size. Overall, this study suggests that landscape connectivity is key for sustaining populations under fluctuating environments.

 

Legacies of past land use in forest ecosystems There remain few places on Earth that have not experienced some form of land use change. These changes have had profound impacts on biological diversity via habitat loss, modification, and fragmentation. During the past century, many areas across North America and Europe used for agriculture or timber harvest have been abandoned and returned to forest. The extent to which these areas will ever resemble their pre-disturbance condition is a topic of particular interest, both for its theoretical implications for system resilience and community assembly, and for its practical bearing on habitat restoration. Our on-going research addresses the long-term consequences of human practices in forests with histories of agriculture or timber harvest, focusing on nutrient distribution and cycling and habitat suitability for native plant species.