Influence of forest structure and soil composition on watershed performance and management

Background/Question/Methods:

Development continues to reduce and fragment forest cover throughout New Jersey.  Many models indicate that forest cover provides benefits to aquatic systems in watersheds, the land area into which surface water drains and collects. We are investigating whether fragmented forests are less effective in reducing runoff and erosion because this could jeopardizes drinking water, stream habitats, and pressure local economies. The purpose of this study is to establish how urban fragmentation of forests is threatening the Raritan watershed in New Jersey in order to update the information that scientists and policymakers use to manage water quality and quantity of the region. The research team identified differences in soil composition and function, infiltration, percent cover, point quarter, and species of vegetation. All of these are related to stormwater runoff rates. The data collection follows a two-way analysis of a variation model by using statistical analysis to evaluate the results for differences between forest centers and edges, and for differences between site locations.

Results/Conclusions:

Soil analysis demonstrates statistically significant longer infiltration rates, lower percentages of organic matter, higher structural stability, and a closer to neutral pH of the soil in the edge transects compared to that of the center transects, suggesting that forest edges have less capacity for water-absorption. Vegetation analysis demonstrates statistically significant variations between edge and center vegetation transects regarding percent cover and species abundance. Both soil and vegetation data confirm that fragmentation changing forest structure by reducing high soil and vegetation absorption capacity of interior forests and expanding inferior absorption capacity characteristic of forest edge conditions. Future studies can reveal how (or if) increasing forest fragmentation and reduction is related to increasing water runoff and threatening watershed stability.  This issue becomes especially important in areas like the Raritan Basin where much of the drinking water is produced by the surface water network.