A farm-level analysis of landscape patterns and their influence on bird communities resulting from agricultural policies promoting shelterbelt agroforestry systems in eastern Nebraska.

摘要

Evolving agricultural policies and technologies have influenced land management practices within agroecosystems, impacting available habitats providing food and cover for many species of wildlife. More recent agricultural policy dictates that landowners adopt conservation practices that achieve long-term environmental goals. Increasing available wildlife habitat and enhancing habitat quality has become an explicit objective of existing agricultural policy. Thus, there is renewed focus on utilizing shelterbelt agroforestry systems as a tool to achieve conservation goals in the northern Great Plains.; A farm-level agroforestry modeling system was developed to provide policy-makers and farmers with information on the impacts that state and federal programs have on farm income, the environment, and on wildlife habitat. Two Representative Farms---a 700-acre dryland farm and a 1260-acre irrigated farm were created in Saunders County, Nebraska. The Habitat Analysis and Modeling System (HAMS) was used to describe the composition and spatial pattern of the existing landscapes for each Representative Farm and surrounding landscape, as well as for the landscapes surrounding selected Breeding Bird Survey (BBS) routes. Simulated land use changes resulting from the implementation of two shelterbelt policy scenarios, Agricultural and Wildlife, were also incorporated on each Representative Farm and surrounding landscape so that landscape variables could be measured which influence breeding bird species richness and community composition as determined from bird species grouped by habitat response guild.; A more heterogeneous landscape results from implementing either the Agricultural or Wildlife shelterbelt scenario. The percent total woods was confirmed to be a significant determinant of bird species richness on the BBS routes and therefore was important in influencing the bird community at both the farm- and landscape-level. Other landscape metrics which influenced the bird community composition on BBS routes were woody edge percentages and edge density values. Policies promoting shelterbelts at the farm-level as well as on the agricultural landscape create edge habitats which ultimately favor birds within the Forest-edge/generalist and Grassland-edge guild, while bird species in need of conservation such as grassland-field species would potentially be negatively affected.