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The productivity of grasslands depends in part on their diversity of species and functional composition. Our objective was to examine the effects of three landscape positions (summit, backslope, and toeslope) and three stocking systems (continuous, rotational, and non-grazed) on species diversity and percentage of cover of grass, legume, and weed species functional types in southeastern Iowa pastures. Data were collected in 0.2-m² plots randomly distributed throughout each of four replicate pastures in spring and summer 2000 and 2001. Backslope landscape positions within pastures managed with either continuous or rotational stocking contained the greatest overall diversity of species. Across years, overall species richness under grazing averaged 4.8 on backslopes, 3.5 on summits, and 2.9 on toeslopes. Legume cover was greatest within the rotational stocking system, averaging 21% on back- slopes, 10% on summits, and 3% on toeslopes across years. Cool-season grasses dominated summits and toeslopes, consisting of 88 to 94% of the cover. Weed species diversity and cover were greatest on backslopes within the continuous stocking system. Our results showed that rotational stocking had more desirable effects through greater legume cover and less weed cover on backslopes than continuous stocking. This research suggested that spatial components of pastures should be considered to optimize the production and quality of forage for grazing livestock. [ABSTRACT FROM AUTHOR]

The objective of this research was to describe how landscape position, grazing management, and scale affected overall plant species richness and species richness per functional group in temperate pastures located in the central United States. The effects and interactions of summit, backslope, and toeslope positions and continuous, rotational, and nongrazed stocking systems on species richness were examined at sample scales of 0.18m2and 4.5m2. Landscape position explained 40–63% of species richness variation at 0.18m2 compared to 3–26% at 4.5m2 for overall, perennial, perennial grass, vegetative-spreading grass, perennial herb, and perennial N2-fixing herb (legume) functional groups. Grazing management, in contrast, explained 22–35% of species richness variation for overall, perennial, annual–biennial, perennial grass, and perennial bunchgrass functional groups at 0.18m2 compared to 30–43% of their variation at 4.5m2. Landscape position and stocking system mostly did not interact. Overall species richness averaged 11.7, 14.3, and 10.3 on summits, backslopes, and toeslopes, respectively, and 14.8, 12.9, and 8.7 within the continuous, rotational, and nongrazed systems, respectively, at the 4.5m2-scale. Backslope positions supported more species than summits and toeslopes regardless of scale, with differences that appeared related to total vegetation production and aboveground competition. Continuously and rotationally stocked pastures also supported more species than nongrazed pastures, effects that were consistent across functional types and scales. Increased scale enabled detection of a greater number of species per unit area but reduced the percentage of species richness variation explained by pasture position and management. [Copyright &y& Elsevier]