SPATIAL AND TEMPORAL SCALING OF PLANT BIODIVERSITY IN GRAZED SYSTEMS

Authors: Goslee, Sarah; Gonet, Jeffery; Sanderson, Matt

Submitted to: US-International Association for Landscape Ecology
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2005
Publication Date: 3/16/2005
Citation: Goslee, S.C., Gonet, J.M., Sanderson, M.A. 2005. Spatial and temporal scaling of plant biodiversity in grazed systems [abstract]. US-International Association for Landscape Ecology. p. 82.

Interpretive Summary: An interpretive summary is not required.

Technical Abstract: Much effort has been put into characterizing the species richness and plant community diversity of natural areas, but little attention has been paid to the diversity of agricultural areas. While row crops provide little plant diversity, permanent pastures can provide habitat for plant and animal species of grasslands, and add diversity to the landscape as well. We surveyed plant species diversity in grazed systems across the northeastern United States from 1998 to 2003. Modified Whittaker plot sampling was used to assess diversity at multiple spatial scales on two or more pastures per farm. In total, we have sampled 122 pastures on 42 farms in 11 states. Some farms were sampled once, and others resampled in successive years (1-7 samples), for a total of 196 modified Whittaker plots. The 1000 m2 outer plot area held anywhere from 9 to 59 plant species, and the mean richness was 29 species / 1000 m2. We identified 282 species growing in pastures during the seven-year survey. The species composition (based on presence-absence data) of herbaeceous pastures within the same farm was significantly more similar than those on different farms (Mantel r = 0.36, p < 0.0001). Repeated samples in the same pasture were significantly more similar than those on different pastures (Mantel r = 0.20, p < 0.0001). Species composition was strongly related to latitude (Mantel r = 0.35, p < 0.0001), indicating a turnover in species along a north-south gradient. Dominant forage species such as white clover and orchardgrass are common throughout this range; differences in composition are driven by less abundant species. Over 70% of the dominant species (>10% mean canopy cover in any pasture) were non-native, while over half of the minor species were native. Although the dominant species in northeastern pastures are naturalized forage species, pastures can host highly diverse plant communities, including native and regionally abundant species. The open grassland habitat created by pastures is otherwise rare in the northeastern United States.