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The roots of Sitka Spruce growing in peaty soils subject to waterlogging suffer seasonal die-back which leads to the development of a surface-rooting habit, which in turn renders the trees unstable and susceptible to windthrow. This study was primarily initiated to elucidate which soil factors are instrumental in causing die-back. Possible phytotoxins viz: iron(II), ethylene and hydrogen sulphide were monitored for one year in peaty gley and deep peat soils under a Sitka Spruce stand. 1,4aximum levels were recorded in the period January - March. Unfortunately, 'volatile organic acids (VOA's) which are also potential phytotoxins of waterlogged soil could not be monitored successfully because the problems of separation and analysis, recognized by many workers, were not overcome. One estimate was made of their total concentration, using a titration method. The concentration of manganese(II) was determined on one occasion in the first winter but it proved to be well below the level previously recognized as phytotoxic. The oxygen status of the site hed been assessed in an earlier study but redox potentials were measured during the second winter and proved to be highly correlated with the plant-available iron level. The effects of iron(II), ethylene and acetic and butyric acids on the roots of Lodgepole Pine (Pinus contorta Dougl. ) and Sitka Spruce (Picea sitchensis (Bong. ) Carr. ) growing in regularly aerated nutrient solution at 13°C were examined using the "aeration tank" system devised for this investigation. Plants were allowed to acclimatise for (xiii) one week before root growth was monitored. Toxin treatment began after a further 3 weeks, lasted for 3 weeks and was followd by a3 week recovery period. Measurements of root growth were converted to Relative Growth Rate so that growth during toxin and recovery periods could be easily compared with the original growth rate. The effects of anoxic conditions (once with the addition of sulphide) were studied using the same method. Iron and the organic acids all caused some death of root tips at concentrations of < 100 ppm and severe reduction in root growth at 20 ppm; butyric acid was the most effective toxin. Ethylene (5 - 20 ng/ml) reduced and sometimes halted root growth but did not cause root death. Pronounced swelling of the root, especially in the case of Lodgepole Pine treated with 20 ng/ml ethylene suggested that an induction of root dormancy might be taking place. Sitka Spruce was the more severely affected by anoxic conditions and experiments confirmed that it was the more sensitive to waterlogging. It was also the most sensitive to the volatile organic acids and in some ways, to iron. The modes of recovery of Lodgepole Pine and Sitka Spruce from treatment with zero oxygen or toxins were consistently different. Sitka Spruce tended to produce new roots at the base of the stem or new lateral roots in the upper part of the root system, whereas Lodgepole Pine often recommenced growth at the original root tips or, if these had been damaged by the treatment, laterals in the lower part of the root system. This suggested that Lodgepole Pine root tips were (xiv) receiving a superior supply of oxygen. Using a polarographic technique, the sub-apical oxygen flux from Lodgepole Pine roots was found to be greater than that from Sitka Spruce roots of the same length. A rigorous treatment of the data confirmed that Lodgepole Pine was the better ventilated species. Where roots survive in anaerobic conditions it is thought that the superior internal aeration system of Lodgepole Pine supplies the oxygen necessary to (i) detoxify VOA's (ii) oxidise and therefore immobilize iron(II) ions and (iii) maintain the viability of those distant parts of the roots experiencing an anoxic environment. Thus it is this property which seems to render Lodgepole Pine more able than Sitka Spruce to produce a normal root system in waterlogged soil. The link between internal aeration and tolerance to waterlogging, anoxia and VOA's was extended to embrace wetland and nonwetland species in general. An experiment where 100 ppm acetic acid was applied to the roots of two species known to be capable of extensive aerenchyma formation and to pea, a mesophytic species, provided sound evidence for this hypothesis. The investigation was successful in elucidating the factors causing the observed winter die-back of Sitka Spruce roots. Ethylene, hydrogen sulphide and manganese(II) ions were eliminated as causative agents. Plant-available iron levels in the deep peat trough were high enough to inhibit root growth throughout most of the year and would cause death in winter. Thus, they may account for the stunted tree growth observed in that area but the levels in the peaty gley were insufficient (xv) to account for the root die-back which occurs there. Although low levels of VOA's could play a major role, until extensive field measurements can be made, it must be assumed that anoxia, because its development is likely to precede VOA accumulation, will be the primary factor causing root die-back. The solution to the problem of die-back and subsequent windthrow in Sitka Spruce would seem to lie either in breeding for improved root ventilation or employing soil cultivation techniques which will improve soil aeration.

4 pp. / DeGomez, T. 2006. Preventing Bark Beetle Attacks on Conifers with Insecticides. University of Arizona, College of Agriculture and Life Sciences Bulletin, AZ1380. Tucson, Arizona. / A common method of protecting individual trees from bark beetle attack in the western U.S. is to saturate the tree bole with carbaryl using a hydraulic sprayer at high pressure. With this type of application method spray deposition will occur off-target and may contact open waters where sensitive species are subject to the toxic effects of the pesticide. We report on a recent study in which the authors reported carbaryl drift resulting from single tree protection treatments poses little threat to adjacent aquatic environments, a primary concern when treating trees in campgrounds in the Western United States. Using reasonable no-spray buffers will ensure that adjacent aquatic environments are protected from any negative impacts.

Site preparation effects on growing season soil water regimes were investigated on three clearcut, grass-dominated sites in the Interior Douglas-fir (IDFdk), Montane Spruce (MSxk) and Engelmann spruce-Subalpine fir (ESSFxc) Biogeoclimatic Subzones, near Kamloops, British Columbia. The response of newly planted Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and lodgepole pine (Pinus contorta Dougl.) to these treatments was determined at the IDFdk site. Soil water regimes were measured in scalped, ripped and herbicide site preparation treatments and in an untreated control using a neutron moisture meter, a two-probe gamma-density gauge, tensiometers and thermocouple psychrometers. At the IDFdk, seedlings were spring planted in each of the treatments and control to determine whether microclimate modification by site preparation would improve seedling water relations, growth and survival during the first growing season. Root zone soil water content was most limited at the low-elevation site (IDFdk) and least limited at the high-elevation site (ESSFxc). The different site preparation treatments provided similar increases in root zone soil water content, profile water storage and drainage at each site. This resulted in substantial increases in soil water supply at the lowest two sites. Site preparation resulted in increased Douglas-fir and lodgepole pine stomatal conductance (gs), transpiration (E), leaf area, root egress, root collar basal area and dry matter production. Survival of both species was high in the control and in all site preparation treatments. Both species had similar seasonal patterns of gs and E in the control. In the site preparation treatments, lodgepole pine had greater gs, and by late summer, greater E than Douglas-fir. Although lodgepole pine had substantially higher twig xylem pressure potentials and lower soil-plant liquid flow resistances than Douglas-fir, both species appeared well adapted to survive drought. First growing season stomatal responses of both species to environmental conditions, including normalized vapor pressure deficit at seedling height (Ds/P), solar irradiance (Rs) and root zone extractable water (Φe), were similar when normalized against annual maximum conductance (gsmax ). A multiplicative model with non-linear least squares optimization (NLLS) of response functions to Rs, Ds/P and Φe provided a simple, reasonably accurate description of gs/gsmax for both species, and accounted for differences in gs between the control and ripped treatment. In most cases, the NLLS models developed for a given species and year resulted in relatively precise (R²>0.60) and unbiased estimates of gs /gsmax, and yielded estimates of mean daily stomatal conductance (Gs ) and total daily transpiration (T) within 20% of measured values, for the same species in other years. / Land and Food Systems, Faculty of / Graduate

2 pp. / Pine Bark Beetles, Cypress Bark Beetles / Life cycle of the bark beetles and how to detect in firewood. Source of firewood is important. Dry wood is a poor host for bark beetles. Most bark beetles are host specific. Insecticides should not be applied to firewood to prevent bark beetle infestation.

Revised / 2 pp.

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With climate change, forest soils of British Columbia (B.C.) will likely undergo significant increases in temperature. Changes in temperature may differentially alter steps of N cycling, altering the amount of N in various pools of the cycle. Furthermore, plant species may show a preference for certain N forms available in soils, such as ammonium, nitrate or organic N. Changes in soil N forms and plant N preferences can shift competitive interactions among conifer species in B.C. forests. Using a greenhouse incubation of forest soils from two elevations, I aimed to determine how temperature affects N cycling in soils that differ in temperature adaptations. With a conifer growth experiment where ammonium, nitrate and a mix of amino acids were applied to trees, I studied N form preferences and uptake rates of three conifer species from contrasting environments (Pseudotsuga menziesii, Picea sitchensis, and Picea engelmannii), and how N uptake in these species reacted to increases in soil temperature. Results show that the abundance of all N forms increased with temperature, but the response to warming was stronger in soils from a low elevation. Furthermore, ammonium and soluble organic N in soils increased faster with warming than nitrate. Nitrification potential was higher in the low elevation soil. This indicates that rates of soil processes, producing plant available N may increase with warming and the balance of different N forms may change. Differences in the abundance, composition, or activity of soil biota at these two locations likely caused dissimilar reactions to warming in two chemically and physically similar soils. Conifers exhibited preferences towards N forms, and these preferences are likely due to adaptation to the N form most available in native soils. On average, Douglas-fir showed preference for nitrate (a N form commonly found in warmer areas), Sitka spruce preferred ammonium (a N form high in cooler areas), and Engelmann spruce showed equal preference for organic N and ammonium (organic N is usually abundant in very cold areas). Preference as indicated by plant growth changed when species were grown at different temperatures, showing ability for acclimation in these conifers. Understanding that a soil’s history greatly affects its response to perturbation is important if we are to make predictions on how N cycling in soils may change with changing climate. Knowing how conifers utilize available soil nutrients at different temperatures will help to predict species’ future performance, composition and abundance in B.C. forests as soils warm and tree lines move north or to higher elevations. / Graduate / 0481 / 0817 / boczulst@uvic.ca

The site frequency spectrum of mutations (SFS) and linkage disequilibrium (LD) are the two major sources of information in population genetics studies. In this study we focus on the levels of LD and the SFS and on the effect of sample size on summary statistics in 10 Scandinavian populations of Norway spruce. We found that previous estimates of a low level of LD were highly influenced by both sampling strategy and the fact that data from multiple loci were analyzed jointly. Estimates of LD were in fact heterogeneous across loci and increased within individual populations compared with the estimate from the total data. The variation in levels of LD among populations most likely reflects different demographic histories, although we were unable to detect population structure by using standard approaches. As in previous studies, we also found that the SFS-based test Tajima's D was highly sensitive to sample size, revealing that care should be taken to draw strong conclusions from this test when sample size is small. In conclusion, the results from this study are in line with recent studies in other conifers that have revealed a more complex and variable pattern of LD than earlier studies suggested and with studies in trees and humans that suggest that Tajima's D is sensitive to sample size. This has large consequences for the design of future association and population genetic studies in Norway spruce.

Meadows are crucial components to larger river watersheds because of their unique hydrologic and ecological functions. Due to climate change, over grazing, and fire suppression, conifer encroachment into meadows has accelerated. In some western regions, nearly half of all meadow habitat has been loss due to conifer encroachment. Restoration of these hydrologic systems requires tree removal. Many studies exist that address the issue of conifer encroachment in montane meadows, however, few studies focus on the role that conifer removal plays on the encroaching meadow. Furthermore, few studies exist that document the hydrologic change from conifer removal and further restoration steps, if any, to take after the removal. The overall research goal is to understand the efficacy of removal of encroached conifers from an encroached meadow (Marian Meadow) for successful meadow restoration. The objectives of this study are to determine (i) quantify the meadow hydrology following removal of encroached conifers, (ii) determine if forest tree removal adjacent to the meadow influences the meadow’s hydrology, and (iii) test three common revegetation techniques for a formerly encroached montane meadow.. Marian Meadow is in Plumas County, CA at an elevation of 4,900 feet. This 45-acre meadow enhancement project is part of a 2,046-acre timber harvest plan implemented by the Collins Pine Company. Soil moisture sensors at one foot below the ground and water table depth sensors at four feet below ground were installed in Marian Meadow and a control meadow in September 2013, with additional soil moisture sensors at three-foot depth installed August 2015. The removal of encroaching conifers from Marian Meadow occurred in June 2015. Electrical Resistivity Tomography (ERT) was used to determine maximum water table depths and climatic variables were measured from a weather station as inputs for the water budget. A groundwater recession curve equation was used to model water table depths between water table depth sensor measurements and ERT measurements. A general linear model was used to determine any statistical significant difference in soil moisture and water table depths prior to and after conifer removal. Revegetation plots were installed at the start of the 2017 growing season to determine the establishment rate for three different techniques (BARE, WOOD, and EXISTING) and three different species of meadow plant. Technique BARE, which removes approximately 10 cm of top soil and disperses seed was statistically significant, yielding the highest population count. Another growing season data collection and control plot is required to draw further conclusions and recommendations. The water balance indicated that the majority of Marian Meadow and the Control Meadow’s water storage can be attributed to precipitation and not upland sources. This hydrologic characteristic is common in dry meadows. The statistical analysis indicated that measured water table depths increased on average by 0.62 feet following conifer removal. The first year following restoration and the second year following restoration yielded statistically significantly different water levels than pre-restoration water levels. The third year following restoration is inconclusive until the end of the 2018 WY data set is available. On average, soil moisture increased by 6.43% following conifer removal and was statistically significantly different in all three post restoration years when compared to pre-restoration volumetric soil moisture content. Additionally, growing season (April through September) water table depths indicated that meadow vegetation communities could be supported in Marian Meadow following conifer removal. The removal of conifers from an encroached meadow appears to promote soil moisture and water table depth conditions indicative of a meadow and meadow plant community types.