Microclimate of a natural pasture under planted Robinia pseudoacacia in central Appalachia, West Virginia

Abstract

The conditions under which forages yield more under tree canopies than in open fields are not well understood. This study was conducted to determine how microclimate experienced by forages in central Appalachia is modified by black locust (Robinia pseudoacacia L.) tree canopies. The effect of tree row location relative to forage growing point was evaluated for its impact on soil water, photosynthetically active radiation (PAR), red/far-red ratio, and surface soil temperature. There was no consistent spatial dependency relating tree rows to soil water levels. While daily PAR decreased as the time under shade increased, the level of PAR under tree canopies nearly doubled as cloud cover increased from 0 to 25%. The red/far-red ratio decreased from 1.16 to 0.2 over forage growing between tree rows compared to forage within tree rows. Surface soil temperature remained nearly constant (1.5–2 °C increase) during sunny days under tree canopies but increased 8–12 °C by mid afternoon at unshaded sites depending on soil water levels. Forages under black locust trees experienced less extreme variation in both daily PAR and temperature than unshaded forages, thus reducing the metabolic cost of adaptation to extreme conditions.