Characterizing the spatial pattern of Abutilon theophrasti seedling patches

Spatial biology of weed populations is the study of weed patches and their relevant patch-level processes. In this context, a patch was defined as an area in which individuals are aggregated into discrete subdivided populatio ns. Four Abutilon theophrasti seedling patches in two continuous maize prod uction fields were surveyed using a contiguous grid of quadrats between 199 5 and 1997, Surveyed area was dependent on patch size and ranged from 96 m( 2) to 1134 m(2). Within each area, all seedlings were counted in each 1 m x 0.75 m quadrat in June, just before post-emergence weed control, and in mi d-July after all weed control practices were completed. The spatial pattern observed in the seedling distribution maps was single or multiple focal po ints of high seedling density that decreased with distance from the focal p oint. Two-directional correlograms corroborated this visual observation, su ch that A. theophrasti seedling density in neighbouring quadrats was spatia lly autocorrelated, and correlation strength decreased with distance separa ting quadrats. Autocorrelation coefficients decreased at a greater rate acr oss crop rows than parallel to crop rows. Visually, patch shape was ellipti cal and oriented in the direction of field traffic. Factors affecting patch -level processes of spatial aggregation, stability and edge dynamics were c onsidered.