Influence of Date of Flushing on Flowering in Pinus banksiana
NUMEROUS attempts have been made to relate the year-to-year variability in flowering of forest trees to seasonal fluctuations in weather conditions which, in turn, are believed to influence the internal physiological processes regulating flower initiation1. The pronounced effect of photoperiod on flowering, noted in many herbaceous species, appears to be lacking in forest trees, and observations indicate that most trees are photoperiodically day-neutral2,3. However, until more definitive experiments have been undertaken, photoperiod cannot be ruled out as a factor influencing flower formation.
Manipulation of Flowering in Conifers Through the Use of Plant Hormones
The rationale for attempting to induce flowering in juvenile-phase seedlings (i.e., “that phase in ontogeny during which seedlings cannot be induced to form flowers by any means” (Doorenbos, 1965)) needs no explanation to those engaged in forest tree breeding. However, not only is termination “at will” of juvenility a goal of importance, but regularization of cone crops on sexually mature seed orchard trees is imperative in any program of reforestation where genetically superior stock are used. In the past these two goals have been treated as separate problems and Doorenbos (1965), Robinson and Wareing (1969) have urged that a clear distinction be drawn between treatments which induce the seedling to reach the “ripeness-to-flower” state (Klebs cited in Lang, 1965) and treatments which promote flowering in an already adult plant. However, I am not certain that such a clear distinction should be made since many of the cultural treatments which promote flowering in adult, but otherwise non-flowering trees, will also promote, on occasion, precocious flowering in juvenile-phase seedlings.
DEM generation from new VIR sensors: IKONOS, ASTER and Landsat-7
DEM generation is a living R&D topic since new-launched satellite images can be used to generate stereoscopic images. Using a coplanarity equation model developed at CCRS and an automatic matching method developed at PCI, DEMs are generated with new VIR stereo data. Accuracy of 4.9 m with high-resolution IKONOS images, and 33 m and 101 m with medium-resolution ASTER and Landsat-7 ETM/sup +/ images respectively are obtained. The same matching accuracy of one-pixel is translated into worse results with Landsat due to a small B/H ratio of 0.15.