COS 23-8: Landscape versus patch effects on prairie insect communities

摘要: Tall-grass and mixed-grass prairie biomes have experienced extensive anthropogenic land cover change inducing habitat loss/fragmentation, changes to landscape structure and degraded patch quality. Such changes could impact prairie insect communities via a number of mechanisms. 1) Patch area: via species-area relationships. 2) Patch quality: vegetation changes can reduce habitat suitability. 3) Landscape composition: novel land cover elements could supplement habitat or act as population sinks. 4) Landscape edges: edges between land cover elements may impact movement. 5) Landscape diversity: more land cover types could increase species richness via complementation. 6) Landscape configuration: the shape of patches in the landscape influences edge effects. The relative importance and, for the landscape mechanisms, the scale at which these mechanisms function is unclear. To investigate the relative roles of these mechanisms on insect communities we trapped insects on 20 native prairie patches in western Minnesota and eastern North Dakota. Vegetation composition and density were measured at each patch. Land cover in the surrounding landscape was determined from digitized aerial photographs. Various measures of landscape composition, edges, diversity and configuration were calculated in GIS at multiple 100 m buffers out to a total distance of 1000 m.