Woody plant production and leaf area index along urban-rural highway gradients in Louisville, KY

Linear woodland communities along highways function as barriers to the movement of pollutants across landscapes. Consequently, ecosystem processes and services in these communities can be affected by traffic density and proximity to a city. We found that woody plant communities along interstates in Louisville, KY are dominated close to the city by an exotic shrub, Amur honeysuckle (Lonicera maackii). This shrub’s dominance increases the community’s structural density near the ground. We quantified leaf-fall biomass and leaf area index (LAI) along these highways, as measures of productivity and potential air pollutant capture in plots dominated by honeysuckle and those not dominated by honeysuckle. While mean basal area of live trees was similar between these two community categories (47.2 vs. 47.7 m² ha^-1 in high vs. low honeysuckle plots), initial results suggest that primary productivity may be lower in high honeysuckle plots (169.2 vs. 218.8 g fallen leaves m^-2, respectively). Total LAI (two-sided) in honeysuckle-dominated plots was much lower than in low honeysuckle plots (2.55 versus 4.44 m² m^-2). Honeysuckle leaves comprised 42.7% of the total LAI in honeysuckle-dominated plots versus 0.4% in low honeysuckle plots. Since LAI may determine the ability of these communities to filter air pollutants, total pollutant filtration may be less in highway corridors dominated by honeysuckle. However, more pollutant capture may occur at sub-canopy levels in honeysuckle dominated plots. Pollutant capture in these woodland communities would then depend on pollutant sources, points of entry and whether particulate or gaseous pollutants are considered.