Glyphosate-resistant canola has been widely adopted in western Canada. This has prompted producer interest in the timing of glyphosate application, particularly under zero tillage, where glyphosate is often applied preseeding. Field experiments were conducted at Lacombe, Edmonton, and Beaverlodge in Alberta in 1997, 1998, and 1999 to determine the importance of preseeding glyphosate and the most effective growth stage to apply glyphosate to canola to optimize yield and weed management. Treatments consisted of zero-tillage systems, with and without preseeding glyphosate, and a conventional-tillage system involving preseeding tillage operations. Glyphosate was applied at the one- to two-, three- to four-, or five- to six-leaf stages of canola in each tillage system. Canola yield and weed dry weight were largely unaffected by the tillage system. In most instances, the highest canola yields occurred when glyphosate was applied early to the crop. The opposite occurred at Lacombe and Edmonton in 1999, however, where canola yield increased as glyphosate was applied at later crop growth stages. This yield benefit likely resulted from the control of late-emerging weeds that exerted competitive pressure on canola. Early glyphosate timing in glyphosate-resistant canola may eliminate the need for preseeding glyphosate in zero-tillage systems, and optimize yield and weed control.

The importance of high winter winds and plant temperatures as causes of winter desiccation damage at the alpine treeline were studied in the Austrian Alps. Samples of 1- and 2-year twigs of Picea abies and Pinus cembra were collected from the valley bottom (1,000 m a.s.l.), forestline (1,940 m a.s.l.), kampfzone (2.090 m a.s.l.), wind-protected treeline (2,140 m a.s.l.), and wind-exposed treeline (2,140 m a.s.l.). Cuticular transpiration was measured at three different levels of wind speed (4, 10, and 15 ms) and temperature (15°, 20°, and 25° C). At elevated wind speeds slight increases in water loss were observed, whereas at higher temperatures much greater increases occurred. Studies on winter water relations show a significant decline in the actual moisture content and osmotic potentials of twigs, especially in the kampfzone and at treeline. The roles of high winds and temperatures in depleting the winter water economy and causing desiccation damage in the alpine treeline environment are discussed.

The importance of the anatomy of the needles of coniferous trees in determining alpine timberline was studied in the Austrian Alps. Samples of 1- and 2-year-old needles of Picea abies (L.) Karst. and Pinus cembra L. were made from wind-exposed and wind-protected timberline (2140 m above sea level (a.s.l.)), and from the kampfzone (2040 m a.s.l.), forestline (1940 m a.s.l.), and valley bottom (1000 m a.s.l.). The samples were measured for number of needles per centimetre twig, twig length, needle length, cuticle thickness, thickness of epidermis and hypodermis, and depth of stomatal crater. There is a decrease in cuticle thickness with increasing altitude and with increasing wind exposure at timberline, and this is correlated with increased transpiration. The role of inadequate cuticle formation in desiccation damage and mortality of the needles is a significant factor in the control of upper timberline.

In response to farmer complaints of poor triallate performance, wild oat seed was collected from 34 fields in Alberta in the fall of 1990. Screening trials in the greenhouse indicated that 15 of the populations were highly resistant to triallate applied at the equivalent of the recommended field rate (1.7 kg ha-1), whereas the other 19 populations were adequately controlled. All triallate-resistant populations were also highly resistant to difenzoquat applied at 1.7 kg ha-1(equivalent to twice the recommended field rate). The effect of increasing rates of both herbicides on dry weight of five of the resistant and two of the susceptible populations was determined in greenhouse experiments. Triallate applied up to 3.4 kg ha-1had little or no effect on the resistant populations, whereas the susceptible populations were controlled at 1.7 kg ha-1. At rates of 6.8 kg ha-1or higher, there were differences among the resistant populations and among individuals within the populations in the response to triallate. Response of the resistant populations to increasing difenzoquat rates was variable between experiments, but in all cases the effect of difenzoquat on wild oat dry weight was considerably less in triallate-resistant than triallate-susceptible populations. Effects of increasing rates of triallate and difenzoquat on resistant and susceptible wild oat populations growing with barley in field experiments were generally similar to the responses in the greenhouse.

High-altitude coal waste areas are usually difficult to revegetate. However, naturally occurring plant species may be adapted to the extremely harsh substrate of these waste areas. Ten coal waste areas (spoils) of varying ages in the Rocky Mountains in Alberta were analyzed for physical and chemical properties and vegetation composition. Older spoils have a reduced fraction of coarse material, a higher clay content, a greater moisture retention capacity at-1.5 MPa, and higher levels of available N, P, K, and S, as compared to younger spoils, indicating physical and chemical weathering of the spoil rock minerals at the older sites. Natural revegetation of the coal spoils is sparse and patchy with low plant cover and this fact may be attributed to poor moisture and nutrient availability. Colonization by certain species is effective because of their low growth-form, efficient vegetative reproduction mechanism, low nutrient requirements, and/or N-fixing ability. A total of 59 frequently occurring native plant species on coal waste areas were evaluated for their potential in revegetation. A majority of these species seem to have excellent potential for revegetation of high-altitude coal mine disturbed areas in the Rocky Mountains of Alberta. RESUME Rogingration naturelle de la vigitation sur les d blais de mines de charbon dans les Montagnes Rocheuses de l'Alberta et son importance pour la selection des espices a utiliser pour la restauration des terres. La r6g6neration de la v6g6tation sur les d6blais de mines de charbon a haute altitude est en g6neral difficile. N6anmoins, certaines especes veg6tales naturelles peuvent etre adaptees au sous-sol extremement aride de ces zones de d6blais. Dix zones de d6blais de mines de charbon plus ou moins anciennes dans les Montagnes Rocheuses de l'Alberta ont ete 6tudiees en termes de propriet6s physiques et chimiques, ainsi que de la composition de la v6getation. Les d6blais plus anciens contiennent moins de mat6riaux grossiers, plus d'argile et pr6sentent une plus grande capacit6 de retention d'eau '-1,5 MPa et de plus hautes teneurs en N, P, K et S disponibles que les deiblais plus r6cents, indiquant une alteration physique et chimique des mineraux contenus dans les deblais plus anciens. La r6generation naturelle de la v6getation sur les d6blais de mines de charbons est treis clairsemee et inegale, avec une faible couverture vegetale; cette situation peut &tre attribu6e a un manque d'humidite et de substances nutritives. La colonisation par certaines especes est efficace du fait de leur forme de croissance basse, un mecanisme de reproduction v6g6tative efficace, des besoins moderes en substances nutritives et/ou leur capacite ~ fixer l'azote. Au total, 59 especes v6g6tales fr6quemment trouv6es sur les d6blais de mines de charbon ont ete' valuees en termes de potentiel de r6gen6ration de la v6g6tation. La majorite de ces especes semblent poss6der un excellent potentiel pour la r6g6neration de la v6g6tation des zones perturb6es par les mines de charbon ia haute altitude, dans le...