LTREB Renewal: Trajectory for the Recovery of Stream Ecosystem Structure and Function during Reforestation

Stroud Water Research Center, Avondale PA

Investigators

Abstract

Reforestation of riparian areas is widely considered a best management practice for restoring and improving water and habitat quality of streams and rivers throughout the United States. Millions of dollars are invested in riparian forest restoration each year by state, federal, and private agencies and institutions. However, little is known about how long it takes for the physical, chemical, and biological aspects of a stream ecosystem to be restored so that the ecosystem can once again provide the services that humans need (i.e. it is swimmable, fishable, drinkable). Nor is there much known about the stages that the stream ecosystem passes through during that restoration process and the stream?s relative functionality at each stage. This project will document the time frames of various stages of stream ecosystem restoration, characterize the sequence of those changes through time, and reveal whether the trajectory of recovery of stream ecosystem structure (physical, chemical, biological) parallels that of ecosystem function (delivery of service to humans). This information, in turn, will help provide the technical basis for better managing riparian corridors so that both the quantity and quality of fresh water for both humans and wildlife can be sustained at a high level for future generations. The negative effects of eliminating riparian forest along stream ecosystems are well documented. Yet, the science of stream ecosystem recovery to riparian forest restoration is weak at best. This project quantifies the trajectory of stream ecosystem recovery in terms of its physical structure, flow of energy, cycling of nutrients, and the composition of biological communities following reforestation of meadows or pastures with native deciduous trees. As the planted forest grows and matures, research will focus on the time frames over which stream ecosystem variables change compared to reference- endpoints of a mature forested- and meadow stream reach. The project is interdisciplinary, and brings together research in fluvial geomorphology, hydrology, biogeochemistry, organic and isotope geochemistry, nutrient cycling, and community ecology of heterotrophic and autotrophic microorganisms, macroinvertebrates, and fishes to describe the trajectory of stream change as a forested riparian matures. Key research questions include: the change over time and order of change of different biophysical variables, such as light, temperature, channel geomorphology, bed complexity and hyporheic zone exchange, to documenting the efficiency and magnitude of food-web processing of organic Carbon as organic inputs change during reforestation and the relationship between the level of ecosystem services such as Carbon and Nitrogen processing scale and the degree of stream ecosystem restoration. The project includes several innovative approaches including large wood debris inventories and fate-tracking, hyporheic exchange studies, LIDAR earth/vegetation surveys, molecular fingerprint analysis of microbial communities, species level analysis of macroinvertebrate community structure, fish biomass and productivity measures, and stable isotope analysis of food and functional feeding animal groups. Ongoing and active outreach citizen based scientists, municipal employees and farmers by Stroud researchers will allow public participation using low cost, open source sensors deployed in the WCC LTREB for water quality parameters.