Print PageAgricultural lands are increasingly important targets of conservation initiatives, being called upon not only to minimize their negative environmental impacts, but also to support habitat for biodiversity and sustain multiple ecosystem services. Reintroducing woody species as live fences has been promoted based on the assumption that they will locally enhance both habitat and services. Yet, widespread adoption of live fences has been limited due to managers’ concerns about associated decreases in agricultural productivity. To evaluate the role live fences play in promoting avian diversity, and potential tradeoffs in forage production, we assessed bird species composition and pasture productivity in and adjacent to three fence types: post-and-wire, structurally simple live fences (e.g., composed of pruned trees with short, light canopy) and structurally complex fences (e.g., composed of trees of full height and canopy size). We used fixed-radius point counts at 18 sites to determine how fence type impacts: 1) composition of avian communities; 2) distribution patterns for migratory species and habitat specialists; 3) distribution of different types of behaviors including foraging and reproduction; and 4) forage production, measured as grass dry weight biomass, in zones directly beneath live fence tree canopy compared with production levels mid-pasture.
Results/Conclusions
Structurally complex live fences fostered bird diversity and hosted twice the number of bird species as simple fences and surrounding pastures. Analysis of similarity and evaluation of Bray-Curtis dissimilarity matrices revealed that bird species assemblages on structurally complex live fences were significantly more diverse than those observed on all other fence types. 90% of our observations of migrants and habitat specialists (e.g., species associated with densely wooded, closed canopy areas) occurred in structurally complex live fences. Pasture productivity was reduced by up to 60% in the zone directly beneath the tree canopy of structurally complex live fences, however this reduction was limited to a narrow zone, ≤5m wide on each side of the fence. In contrast, structurally simple live fences, composed of pruned trees, did not reduce pasture productivity, nor did they foster bird diversity. Simple live fences hosted similar bird species richness as surrounding pastures and bird species composition did not differ significantly from bird species assemblages on post-and-wire fences. These findings suggest that conservation incentive programs should focus on structurally complex live fences. While structurally simple live fences did not decrease forage productivity, and they may influence other unmeasured services, they did not contribute support to avian diversity.
