The Potential Geographic Distribution of The Invasive Weed Senna obtusifolia In Australia

Senna obtusifolia (sicklepod) is an invasive weed of northern Australia, where it significantly impacts agricultural productivity and alters natural ecosystem structure and function. Although currently restricted to northern regions, the potential for S. obtusifolia to spread south is not known. Using the eco-climatic model CLIMEX, this study simulated the potential geographic distribution of S. obtusifolia in Australia under two scenarios. Model parameters for both scenarios were derived from the distribution of S. obtusifolia throughout North and Central America. The first scenario used these base model parameters to predict the distribution of S. obtusifolia in Australia, whilst the second model predicted the distribution of a cold susceptible S. obtusifolia ecotype that is reported to occur in the USA. Both models predicted the potential for an extensive S. obtusifolia distribution, with the first model indicating suitable climatic conditions occurring predominantly in coastal regions from the Northern Territory, to far north Queensland and into northern Victoria. The cold susceptible ecotype displayed a comparatively reduced distribution in the southern parts of Australia, where inappropriate temperatures, a lack of thermal accumulation and cold stress restrict the invasion south to the coastal regions of central New South Wales. The extent of the predicted distribution of both ecotypes of S. obtusifolia reinforces the need for strategic management at a national scale

Cool-season annual pastures with clovers to supplement wintering beef cows nursing calves

<p>Abstract</p> <p>In December of 3 years, 87 beef cows with nursing calves (594 ± 9.8 kg; calving season, September to November) at side were stratified by body condition score, body weight, cow age, and calf gender and divided randomly into 6 groups assigned to 1 of 6 cool-season annual pastures (0.45 ha/cow) that had been interseeded into a dormant common bermudagrass (<it>Cynodon dactylon</it> [L.] Pers.)/bahiagrass (<it>Paspalum notatum</it> Flugge) sod. Pastures contained 1 of the following 3 seeding mixtures (2 pastures/mixture): 1) wheat (<it>Triticum aestivum</it> L.) and ryegrass (<it>Lolium multiflorum</it> Lam., <b>WRG</b>), 2) wheat and ryegrass plus red clover (<it>Trifolium pretense</it> L., <b>WRR</b>), or 3) wheat and ryegrass plus white (<it>Trifolium repens</it> L.) and crimson clovers (<it>Trifolium incarnatum</it> L., <b>WRW</b>). All groups had <it>ad libitum</it> access to grass hay (12% crude protein; 58% total digestible nutrients). The second week in December, cow estrous cycles were synchronized and artificially inseminated. In late December, a bull was placed with each group for 60-d. Data were analyzed with an analysis of variance using a mixed model containing treatment as the fixed effect and year as the random effect. Body weight and condition scores did not differ (<it>P</it> ≥ 0.27) among cows between February and June. Calf birth weights or average daily gain did not differ (<it>P</it> ≥ 0.17) among treatments; however, calves grazing pastures with clovers did tend (<it>P</it> = 0.06) to weigh more than calves grazing grass only. Weaning weight per cow exposed to a bull was greater (<it>P</it> = 0.02) for WRR and WRW than WRG. Cows grazing winter-annual pastures containing clovers tended to wean more calf body weight per cow exposed to a bull than cows grazing the grass only pastures.</p