Residual weed populations in Saskatchewan – 1976 to 2003
The comparison of the relative abundance of weeds in Saskatchewan in 2003 with results from previous provincial surveys enables the identification of recent shifts in species ranks, life form density and relative abundance. In 2003, 2046 fields of spring wheat, barley, durum, oat, canary seed, canola, flax, mustard, lentil and pea were surveyed. These fields were selected using a stratified random sampling procedure based on ecodistricts. In each field, weeds were counted in 20 quadrats (50 by 50 cm) in late summer. Weed data are summarized using a relative abundance index based on frequency, field uniformity and density. Green foxtail was the most abundant weed, wild oats ranked second, wild buckwheat third and Canada thistle fourth. The results from the 2003 survey are compared to results from surveys of 1178 fields in 1995, 1149 fields in 1986 and 4423 fields in 1976-1979. Twelve species have been ranked amongst the top 20 most abundant species in each survey. Seven species, ranked in the top 20 species in the 1970’s and/or 1986, have since declined: rose, prostrate pigweed, night-flowering catchfly, cow cockle, bluebur, pale smartweed, flixweed. Six species have appeared in the top 20 list for the first time in 1995 and/or 2003: cleavers, barnyard grass, wheat, dandelion, quack grass, canola. Relative abundance of annual grass and perennials has increased, while relative abundance of annual broad-leaved species and facultative winter annuals has decreased. Densities of all life forms have decreased since the 1970’s.
weed life form
weed relative abundance
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