PARENT SESSION
Contributed Oral Session 55: Agroecology: Management
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 513 A, Level 5, Palais des congrès de Montréal

Temporal Variations of the Species Area Curve in Organic and Conventional Spring Wheat Systems.

Pollnac, Fred¹, Menalled, Fabian ^*,1, Maxwell, Bruce¹, ¹ Leon Johnson Hall, Bozeman, MT, USA

ABSTRACT- The species-area curve is a widely used method in ecology, and has been successfully applied to natural ecosystems. However, it is seldom applied to agroecosytems. Our objective was to assess 1) if the species-area curve varies between organic and conventional systems, and 2) the within season and between year stability of the species-area relationship. Data were collected in 2004 and 2005 at Moore, Montana, at three organic plots (445.3m²) and 3 conventional plots (222.65m²). Weed species richness data were collected at the whole plot scale and from two randomly located nested plots (0.1m², 1m², 10m²). Studied systems were in the spring wheat phase of the rotation (organic: spring wheat, lentil, barley, and fall Austrian winter pea; conventional: spring wheat, winter wheat, barley, chemical fallow). Crop data was added to species richness for all plots to account for total system species richness. System species richness increased consistently with area for conventional and organic plots. For the early- and late- 2004 summer sample periods, organic and conventional curves differed significantly (P = 0.05), with the organic curves slopes (beta-diversity) and intercepts (alpha-diversity) being higher than those of the conventional curves. Mean system species richness was also significantly higher for the early-2004 summer (P = 0.03) and late- 2004 summer (P = 0.002) sampling periods. This study will complement other research on the management significance of weed community diversity in agricultural systems.

Key words: agroecosystems, weed diversity, species richness, weed community