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. Company workers as needed, generally once or twice a week. Source of water was a <br />sedimentation pond lower in the reclaimed watershed. Drippers delivered water at 1 <br />gallon/minute, and were programmed to deliver water daily at 1.3, 0.6, and 0.3 gal/day/tree for <br />the high, medium, and low irrigation levels; equivalent to 14.4, 7.2, and 3.6 inches of <br />precipitation per month. <br />The non-irrigated control received no supplemental water. Irrigation treatments were applied <br />daily during the early morning. Drippers required 4 lbs pressure for activation; the valve box and <br />distribution lines were configured so that head pressure down stream of the valves did not exceed <br />this value to avoid leakage between irrigation treatments. Soil moisture and temperature sensors <br />were located in each plot and data were recorded hourly. Standard meteorological conditions <br />were monitored at an automated weather station located at the center of the plot, and data <br />recorded hourly included wind speed, wind direction, relative humidity, and precipitation. <br />Hourly soil temperature, moisture content, and matrix potential were also monitored at one tree <br />in each watering treatment. All data were recorded on a Campbell 23x data logger, which also <br />was programmed to activate the irrigation solenoids. Power was supplied from 12 V batteries <br />charged by a solar panel. <br />In addition to the watering study, growth and survival data were obtained from three other types <br />of young aspen trees: <br />1) Natural sprouts that had grown from roots buried in un-irrigated areas of the roto-cleared and <br />dozer-cleared soil adjacent to the irrigated blocks; <br />• 2) commercially-grown potted aspen seedlings that were planted in an non-irrigated fenced area <br />approx 1 km from the irrigation study site, and; <br />3) Natural aspen sprouts growing in an un-mined area of the Yoast mine that had been cleared of <br />mature aspen. None of these study sites were replicated, so the survival, growth, and water status <br />findings are applicable only for that site; and comparability of different un-replicated treatments <br />within the same site must be made with caution. Although the commercially-grown potted aspen <br />trees were planted on dozer-cleared soil, it was not determined if the roots grew out of the <br />potting mix into the dozer-cleared soil during this first year of study. <br />Natural sprouts were growing at random spacing, about 1 ft to 8 ft apart. Natural sprouts <br />selected for measurement were thinned to no closer than 5 ft spacing. The potted and natural <br />trees in all locations were from unknown genotypes, likely different from the irrigated study <br />transplants. The natural sprouts on the roto-tilled soil were all likely from the same genotype <br />since the soil came from the same area; but they were likely different from those on the dozer- <br />tilled soil. Similarly, the natural sprouts on the dozer-cleared soil were possibly from the same <br />genotype. <br />Data Collected <br />Prior to bud break, height of each tree, number of branches, disease and insect infestation, and <br />length of terminal leader dieback was recorded for each tree. Water status and tree growth were <br />measured periodically throughout the experiment. Physical measures of growth were height