Diminishing virgin timber on the Coast of British Columbia leads to consideration as to how management of the second-growth forests will supply the timber industry with a sufficient quantity of good quality raw material in the future. One of the possibilities would be intensive forest management supported by thinnings. The stands of western hemlock (Tsuga heterophylla (Rafn.) Sarg.), which comprise the largest area on the Coast, may be suited to this treatment because of their advantageous silvicultural characteristics. Little information exists on proper methods of thinning these hemlock stands. In addition, experience in logging methods and means of economically handling small logs are lacking. Among the few experiments which have been established to study thinning of hemlock, one is located on East Thurlow Island where nearly pure stands of hemlock occur. The Research Forest on the Island was scheduled to become an experimental and demonstration area for the study of thinning techniques. Studies under way on that area have shown that the methods used, had limited economic success. Commercial thinning operations turned out to be unprofitable partly because there was no adequate road system available for logging. Thinning problems in general, as well as the particular aspect of thinning western hemlock and the methods of handling small logs are discussed in this thesis to illustrate the basic problems involved in a development plan for the Research Forest. Finally, this thesis presents a general road development plan for the Research Forest area and proposes a preliminary management and logging plan. Through cost analysis it is shown that the basic access road system can be constructed economically during a preparatory period by clearcutting scattered overmature stands. Subsequent thinning experiments can be based on that road network. The approach to these problems is general rather than specific because there are few detailed data available from past experiments. / Forestry, Faculty of / Graduate

Estimation of soundwood volume and value is particularly important in British Columbia because nearly half of the forests are overmature or decadent. The objective of this thesis was to develop analytical techniques to define distribution of gross and net volumes within individual standing trees in order that appropriate reductions for decay could be made for estimates of volumes of logs of specified sizes and grades. Relationships of heartrot to stand and tree characteristics and to external abnormalities were analysed for 369 western hemlock (Tsuga heterophylla (Rafn.) Sarg.) trees from the Yale Public Sustained Yield Unit in British Columbia. Comprehensive sorting, correlation and regression analyses were carried out on an I. B. M. 7044 electronic computer. One multiple regression equation provided estimates of total decay volume within individual trees from DBH, total height and external indicators of decay. It had a standard error of estimated decay volume of 18.7 cubic feet (19.5 per cent). A second equation estimated decay volume within individual logs in standing trees from the above variables and from section height. It had standard errors of estimate ranging from 13.7 cubic feet (31.6 per cent) in butt logs to 0.1 cubic feet (2.9 per cent) in top logs. The best taper function which could be derived to estimate upper stem diameters inside bark had a standard error of estimate of 1.29 inches using measures of DBH and total height. Combination of the log and tree decay estimating functions and the taper function facilitated complete description of the soundwood volumes in the sample of 369 trees. A graphical analysis was developed whereby percentages of trees in a stand with more or less than specified decay volumes could be estimated. Preliminary chemical studies of western hemlock wood infected with Echinodontium tinetorium E. and E. indicated that cellulose yields were slightly less than those from soundwood. Such partly decayed wood might be used for the manufacture of pulp without serious reductions in yield on a volume or weight basis. Further research is needed to substantiate the possible cyclic nature of decay losses and to determine the influence of bark thickness and natural pruning on the distribution of decay within individual trees. Application of the analytical techniques developed for western hemlock to other species should result in more precise estimates of soundwood volumes and values, thereby contributing to improved management planning and utilization. / Forestry, Faculty of / Graduate

Two dormancy induction trials were conducted in a private container nursery in Saanichton, British Columbia. The first study examined the effects of photoperiod induced dormancy on morphology, root growth and field performance of fall planted western hemlock (Tsuga heterophyl_1ji (Raf.)Sarg.) and Douglas-fir (Pseudotsuga menzi_esv[ (Mirb.) Franco) seedlings. Various periods of eight hour days, ranging from two to eight weeks, were applied throughout July and August 1983. Outplanting was done in late September. Survival and growth were assessed one year later. The second project investigated the effectiveness of short days, varying levels of moisture stress and a combination of both as dormancy induction techniques for Douglas-fir seedlings. The short day treatment was four weeks of eight hour days. Four levels of predawn moisture stress were: -5, -10, -15 and -25 bars. These classes respectively corresponded to control, light, medium and severe moisture stress levels. Short days and moisture stress were also combined whereby the four week period of short days followed the moisture stress treatments. These induction treatments were applied in July and August 1984. All seedlings were lifted in January 1985 and placed into cold storage for five weeks until March 1985. Morphology, root growth capacity, frost hardiness and dormancy intensity were assessed in January. Root growth capacity and dormancy intensity were again measured in March. In Study I, short days quickly initiated homogeneous budset in both species in approximately three weeks. The average height increment after treatment initiation was 3.7 cm in Douglas-fir and 4.2 cm in western hemlock. Short days reduced shoot dry weight and height. Caliper and root dry weight were unaffected. In September a surge in root growth occurred in hemlock seedlings treated with six or eight weeks of short days. The importance of early budset to allow increased root growth prior to a fall lift was demonstrated. Root growth capacity was similar among all treatments for both species. The planting survival of western hemlock seedlings increased with increasing weeks of short days. Control plants had 76% survival while the eight week regime had 91%. Survival was similar for all treated Douglas-fir seedlings. It ranged from 89% in the two week interval to 98% in the four week regime. One year height increment was significantly greater in the six and eight week short day treatments for both species. For hemlock, it ranged from 6.1 cm in the control plants to 10.4 cm in the six week trees. Douglas-fir height increment ranged from 6.4 cm for the control interval to 8.6 cm in the eight week regime. The six and eight week photoregimes produced the best quality hemlock seedlings for this study. Four weeks of short days appeared adequate for Douglas-fir. In Study II short days effectively initiated and maintained budset in Douglas-fir seedlings in four weeks. After six weeks from treatment initiation, a light to severe moisture stress was as effective in controlling height growth. A natural photoperiod with no moisture stress was least effective. In a comparison of all treatment combinations, only the control plants under a natural photoperiod were significantly larger in all morphological properties. Short days, moisture stress or a combination of both had similar effects on reducing height, caliper, shoot dry weight and root dry weight. Unstressed seedlings in a natural daylength had the highest value of root growth capacity. All other treatment combinations had significantly lower root growth capacity. Only the severe stress under a natural photoperiod significantly reduced root growth capacity compared to any other treatment. Short days accelerated bud burst in the January and March dormancy intensity tests. Frost hardiness was similar among all treatments. Selection of a regime which controlled height growth while maintaining seedling quality was not clearcut. A short photoperiod with no moisture stress was most effective in initiating budset. However, few morphological and physiological differences were evident between short day plants and light and medium stressed seedlings. / Forestry, Faculty of / Graduate

The goal of this investigation was to determine the potential of birds as vectors for the movement of dwarf mistletoe seeds and the means by which such movement could occur. Birds would greatly speed the rate at which these parasites move horizontally or vertically through the forest. Five areas in Oregon, heavily infected by six species of Arceuthobium were studied. Observations of avian behavior point to 13 species whose general behavior make them potential vectors in the distribution of these parasites. More specifically, the roosting and subsequent bathing behavior of most forest birds proves a very important means of potential seed transport. Additionally, an examination of nesting materials revealed that birds bring viable dwarf mistletoe seeds to infectible portions of host trees during the construction of their nests. Nesting, however, seems the least important of the vector mechanisms discussed. I observed no evidence of birds feeding on the seeds of dwarf mistletoe or of seeds being present in their droppings. The more probably means of seed transport is one of epizoochory.

The hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Sternorrhyncha: Adelgidae) is a small invasive insect that frequently causes hemlock (Tsugae spp.) mortality in the eastern United States. Studies have shown that once healthy hemlocks become infested by the adelgid, nutrients are depleted from the tree, leading to both tree decline and a reduction of the adelgid population. Since A. tsugae is dependent on hemlock for nutrients, feeding on trees in poor health may affect the insect's ability to obtain necessary nutrients and consequently affect their population and physiological health. A cluster analysis, based on quantitative and qualitative tree health measurements, grouped sample trees into categories of lightly and moderately impacted trees. The A. tsugae population health on each tree was determined by measuring insect density, survival from aestivation, and peak fecundity. A. tsugae physiological health was determined similarly by measuring insect biomass, total carbon, carbohydrate, total nitrogen, and amino nitrogen. A. tsugae from moderately impacted trees exhibited significantly greater fecundity; however, A. tsugae from lightly impacted hemlocks contained significantly greater levels of carbohydrates, total nitrogen, and amino nitrogen. All A. tsugae physiological parameters increased significantly over time as the insects matured and reproduced regardless of tree health classification. While the results of the physiological analysis generally support our hypothesis that A. tsugae on lightly impacted trees are healthier than those on moderately impacted trees, this was not reflected in the population fitness measurements of the insects. Further examination of A. tsugae egg health may elucidate this apparent contradiction. / Master of Science in Life Sciences

Approximately 5,000 years ago, eastern hemlock (Tsuga canadensis) experienced a sudden, rapid, range-wide decline most probably due to pest, disease, or climate change. An aphid-like defoliating insect, the hemlock woolly adelgid (Adelges tsugae), recently (1950’s) introduced to eastern North America has been spreading across the eastern United States. The adelgid attacks all size and age classes of hemlocks causing up to 95% mortality in affected stands. The potential for another range-wide hemlock decline has raised a number of concerns including the increased threat of wildfire. Altered fuel loadings in modern adelgid-affected stands and the effects of presumably similar changes in fuels and subsequently altered fire regimes following the prehistoric decline are examined. Fuels data from an adelgid-infested stand in Connecticut and an uninfested stand in Massachusetts were used to generate custom fuel models and predict fire behavior in each stand. Sediment cores were extracted from three sites in western Massachusetts and analyzed for fossil pollen and charcoal around the period of the prehistoric decline. Fossil data from two previously studied sediment cores from coastal Maine are included in the analysis. Results demonstrate a clear and highly significant increase in both fuel loadings and predicted fire behavior in the modern, adelgid-affected stand. Three of the coring sites reflect distinct, significant, short-lived increases in charcoal associated with the prehistoric decline; two do not. Results from the first three sites suggesting increased fire activity also were associated with changes in vegetation which indicate disturbance. Increased fire activity after the decline seems most pronounced in areas where fire was common before the decline. Results indicate that fire was not universally a significant factor driving post-decline succession. Research across a broader geographic area is needed to clarify the relationship between fire and hemlock following the mid-Holocene decline, but the results presented here suggest that managers of modern stands affected by the adelgid should include the possibility of intense fires as a threat to landscapes heavily affected by hemlock decline.

Stated preference and revealed preference are two commonly conducted non-market value evaluation methods which can also be applied to make evaluation of forest ecosystem. In the application of these evaluation methodologies, there always exists limitation from the data collection and empirical analysis. In the dissertation here, I extend the traditional evaluation methods with novel design or statistical analysis approaches to solve the practical problem we met in evaluation of forest ecosystem. The first and second chapters are based on stated preference methods. The first chapter employ both the mail survey and on-site survey to investigate the preference for attributes of low-impact timber harvesting programs. In the second chapter, we recruit three interest groups for on-site survey and compare their preference for the low-impact timber harvesting programs. In these first two chapters, choice modeling method is employed to elicit the respondents' preferences, and I also use bootstrap method to get robust estimation results for small sample size data. The last chapter employed revealed preference method to evaluate the economic losses from hemlock damages caused by forest pest. Three different interpolation methods are employed to scale-up the analysis from sites to states. Based on the findings of all three chapters, we can see that these survey design and statistical methods help to overcome the limitations in empirical analysis of forest ecosystem and make more robust inferences for design forest protection policies. / Ph. D.

Eastern hemlock (Tsuga canadensis) is a prominent tree in the forests of eastern North America, where it commonly grows along headwater streams. It is experiencing widespread mortality due to infestations of an introduced insect, the hemlock woolly adelgid (Adelges tsugae). Eliminations of tree species are known to have ecosystem-level effects, and one consequence of hemlock death is a change in allochthonous inputs to headwater streams. I predicted that hemlock twigs' dendritic structure, abundance, and resistance to decay currently make them highly effective retainers of leaves in headwater streams, with consequences for nutrient uptake. To understand the role of hemlock twigs in streams and to compare their functions to those of a potential replacement species, I (1) quantified the decomposition and microbial colonization of twigs and (2) manipulated twig standing crops to quantify effects on leaf retention and nutrient uptake. Hemlock twigs provide a poor-quality substrate for microbial colonization and growth relative to birch (Betula lenta) twigs and are more resistant to breakdown than birch. Although hemlock twigs appear to be effective in retaining leaves, they do not substantially affect reach-scale uptake of ammonium, which is much more strongly influenced by the timing of leaf inputs. Although hemlock death may subtly change patterns of organic matter accumulation and breakdown, the potentially important effects of hemlock death include changes in large wood inputs, changes in hydrologic regime, and increases in rhododendron cover. / Master of Science

The hemlock woolly adelgid (HWA, Adelges tsugae Annand) is an invasive insect that threatens to eradicate native eastern hemlock (Tsuga canadensis (L.) Carr.) across the eastern United States. In southern New England and southern Appalachian forests, HWA-induced hemlock mortality has impacted carbon (C) flux by altering stand age, litter composition, species composition, and coarse woody debris levels. However, no one has examined how total C storage and sequestration may be impacted by these changes. Further, while projections are that HWA will ultimately infest hemlock across its entire geographic range, the majority of studies have been limited to southern New England and Appalachian forests where HWA infestation has been ongoing. To address these gaps, we examined how HWA might alter C dynamics in northern New England forests using the Forest Vegetation Simulator (FVS) and Forest Inventory Analysis (FIA) data to model C storage and successional pathways under three different scenarios: preemptive harvesting of hemlock, HWA-induced hemlock mortality, and a control mimicking natural stand development absent of disturbance. Our 150 year simulation showed that, while all treatments differed significantly in C storage in the short term, there was no significant difference in total C stocks between HWA infestation and presalvage treatments by the 75th year. Compared to the control, both simulated treatments resulted in a significant decrease in total C storage, with greater impacts on stands with higher hemlock densities. However, net C losses over the 150 year simulation were significantly higher for the presalvage scenario, indicating that allowing HWA infestation to progress naturally through a stand may result in the least impact to long-term C sequestration for the region's forests.

Response to fertilization is a function of the degree to which nutrients are limiting growth, the capacity of individual trees to respond to nutrient inputs, the degree to which other factors limit growth, and the possible extrinsic effects of treatment (e.g., root mortality due to fertilizer-induced soil pH effects). Recognition and examination of these factors is essential if response to fertilization is to be predictable. Over the past 25 years numerous western hemlock fertilizer trials have shown responses ranging from negative to positive with no clear trends. Theories for this erratic response include: (a) different nutritional requirements during different stages of stand development; (b) high native N availability or low supplies of other nutrients (P and S, in particular); (c) differential adverse effects of N fertilizers on surface roots, mycorrhizal populations and P nutrition; (d) a requirement for slow release N; and (e) induced water stress. The objective of this study was to develop site-specific guidelines for western hemlock fertilization decision-making for industrial use. This study reports on the first and third growing-season response to two different fertilizer treatments, and identification of possible relationships between fertilizer response and site and stand conditions.