RESUMO
Anthropogenic noise is increasing worldwide because of growing human populations, transportation, and resource extraction. This excessive noise negatively impacts humans and wildlife. To mitigate noise pollution, the use of vegetation in urban planning is becoming increasingly common. However, noise attenuation can be influenced by poorly understood differences in land cover and seasonality that exist across complex urban and peri-urban environments. We compared the noise attenuation capacity of sites typifying dominant land covers in southern Ontario, Canada (forest, tallgrass prairie, and agriculture) across three seasons (summer, fall, and winter). We found that total noise attenuation was affected by a complex interaction of both site and season across low (250 Hz), mid (500 Hz), and high (1000 Hz) frequency sound. Seasonal changes in vegetation density varied between sites and seemed to play only a partial role in total noise attenuation. While forest, trees, and shrubs continue to be effective for managing noise pollution, our results suggest that other types of land cover can also be useful (e.g., tallgrass prairie). With growing interest in the potential noise attenuating capabilities of vegetation, we recommend further consideration of the seasonal variation in attenuation that can occur across the diverse land covers of urban and peri-urban environments.
RESUMO
Although insect defoliators are recognized as major agents of ecological change in North American forests, their ecology in industrially degraded landscapes with poor-quality soils, metal contamination, and marginal vegetation growth is largely unknown. We fed gypsy moth larvae (Lymantria dispar L.) paper birch leaves (Betula papyrifera Marsh) (Fagales: Betulaceae) collected from four forested catchment areas near an abandoned Cu/Ni smelter in Sudbury (Ontario, Canada) with different histories of industrial degradation and remediation (reference, remediated, natural recovery, and degraded). We measured caterpillar feeding, frass properties and decomposability, and the effects of frass on the growth of ticklegrass (Agrostis scabra Willd.) (Poales: Poaceae). Caterpillars generally ate more (+25-50%) and produced more frass (+30-40 %) on a diet of leaves from the more industrially degraded sites. Frass had an overall positive effect on plant survivorship (+4.1-10.8 effect size) and growth (+0.1-0.5 effect size), although the smallest benefits came from frass derived from vegetation from the more heavily degraded sites. Our results suggest that defoliating insects respond to differences in environmental degradation and remediation and that industrial landscapes may be particularly susceptible to more extensive defoliation and increased conversion of foliar biomass into frass, which could alter plant growth and survivorship, soil development, and nutrient and metal cycling. Some of these effects may pose additional challenges to landscape recovery (e.g., increased defoliation) while others may be beneficial (e.g., enhanced plant growth and soil development).