Steve Wilson, Wind Stability of Naturally Regenerated and Planted Douglas-fir Stands in Coastal Washington, Oregon, and British Colombia. Ph.D. Thesis, University of Washington, College of Forest Resources 1998
Risk of wind damage is an important factor influencing forest management throughout the world. Managed forest landscapes of the coastal Pacific Northwest are undergoing a transition from dominance by naturally regenerated second-growth stands to Douglas-fir plantations. This analysis evaluates the impacts of the managed forest transition on risk of wind damage. Experimental plot data are used to compare tree size variability and stand stability between naturally regenerated and planted stands. In addition, a landscape-scale wind risk rating system is developed to evaluate the impact of stand and management transitions at both stand and larger spatial scales. Naturally regenerated stands tend to develop greater variation of tree sizes compared to plantations. Limited size variation in plantations makes them more susceptible to developing high height to diameter ratios (H/D same units) in the dominant trees. The H/D of a tree is a relative measure of stability under wind and snow loads. H/D can be lowered in plantations through reduced planting densities or early thinning. The higher the initial density the shorter the period during which thinning can effectively lower future H/D values. Thinning requirements in dense plantations make their management inflexible. The flexibility with which a stand can be managed describes the rigidity of intervention requirements and/or potential range of stand development pathways. Shorter rotations in plantations compared to naturally regenerated stands offset much of the increased risk of wind damage caused by higher H/D values. The transition from naturally regenerated to planted stands typically increases the diversity of stand ages within a landscape. Even-aged landscapes have distinct periods of high and low risk, as all stands in the landscape move through susceptibility stages together. Uneven-aged landscapes never reach the same levels of landscape risk; however, some portion of the landscape is typically at high risk. As the transition from naturally regenerated to planted stands continues wind damage may be more common but have a reduced potential for devastating a landscape.
Louise De Montigny, An Investigation
into the Factors Contributing to the Growth-Check of Conifer Regeneration on
Northern Vancouver Island. Ph.D. Thesis, University of British Columbia, 1992
Conifer plantations established on cutovers in the CWHb1 zone on Northern Vancouver Island grow well initially, but coincident with the reinvasion of salal on sites formerly dominated by western red cedar and western hemlock (CH phase) the trees become chlorotic and growth stagnates. These symptoms are not seen on sites dominated by western hemlock and amabalis fir (HA phase). This study examined some site and soil chemical factors which could be responsible for differences in forest productivity by: (1) documenting physical differences between the CH and HA phases; (2) documenting morphological and chemical differences between the organic horizons found in forest floors of CH and HA phases; (3) determining seasonal trends in free phenolic acid concentrations of soils under salal on CH cutovers; and (4) determining if solutions of phenolic acids at field concentrations or of salal leachates have a negative effect on conifer seed germination, growth and short term phosphorus uptake. The HA phase was found to occur on higher topographic positions making them drier and more susceptible to windthrow events than the CH phase. This windthrow process appears to generally improve site conditions. Six distinct humus horizons were identified on the basis of origin and on degree of decomposition. The proportion of humus horizon types on the CH reflected ecosystem maturity and lack of disturbance; that of the HA indicated repetitive windthrow events. The CH humus horizons tended to have higher concentrations of K, Ca, and Mn; and the Ha humus horizons were found to be higher in available N and P. Tannin signals from C NMR spectroscopy were found in the Fm horizons of both CH and Ha, but the intensity was greater for the CH. The source of tannins appears to be salal. Concentrations of phenolic acids originating from angiosperms (presumably salal) were significantly higher in summer months, coincident with greater physiological activity of salal. Phenolic acids are known to cause root membrane dysfunctioning in some situations. The germination values of seeds and the biomass of seedlings of Sitka spruce, western hemlock and western red cedar tended to be lower given treatments of either a phenolic acid solution at field concentrations or a salal leachate solution compared to a control of distilled water.
Kelly Kirkland, Using Adaptive
Management Strategies to Evaluate Silvicultural Prescriptions for Achieving
Late Successional Characteristics. MS Thesis, University of Washington,
College of Forest Resources, 1998
With late successional characteristics as a desired goal for management, silvicultural prescriptions are used with adaptive management strategies and comparisons made between the different prescriptions. Changes in forest management that require a shift in management strategies are examined and, after looking at definitions as well as how adaptive management is currently applied, an attempt is made to show how these strategies would be applied to silvicultural prescriptions, especially through the calibration of a growth model (FVS) within the Landscape Management System (LMS). After statistically determining whether model calibration is necessary, growth projections are compared to find which prescription reaches late successional characteristics the soonest.