The white spruce-aspen mixedwood associations of the prairie Les peuplements mClangCs composCs d'Cpinette blanche et de provinces have a variety of possible compositions ranging from tremble que l'on retrouve dans les provinces des Prairies peuvent pure aspen to pure white spruce to mixtures of the two. Regulations se prksenter sous diverses compositions allant de la tremblaie pure and silvicultural treatments have been largely aimed at promoth la pessibre blanche pure tout en passant par un melange des deux. ing the more commercially valuable white spruce, largely through Les normes et les traitements sylvicoles visaient essentiellement plantation establishment and management. We feel that it is 2 promouvoir la plus grande valeur commerciale de l'kpinette blanche, time to re-evaluate our current management of these mixedprincipalement par voie de crCation de plantation et d'amCnagewoods for the following reasons: 1) Because of competition ment. Nous croyons qu'il est temps de rCCvaluer I'amCnagement from hardwoods and grass, white spruce regeneration has been actuel de ces peuplements mClangCs pour les raisons suivantes: 1) very expensive and only partly successful. 2) Hardwoods are now Parce que la lutte contre la compCtition exercCe par les feuillus et acceptable crop trees; the traditional conifer bias is now inappropriate les graminCes au niveau de la rCg6nCration de 1'Cpinette blanche and there are increasing possibilities for conflict between hards'est avCrCe dispendieuse et partiellement rCussie. 2) Les feuillus wood and softwood users of the same land base.3) The increased sont maintenant des espbces acceptables au niveau de la rCcolte; understanding of forest ecosystems and a strong environmental le biais traditiomel envers les conifres est actuellement inapproprik movement have resulted in demands for management systems that et les possibilitCs de conflits entre les utilisateurs de feuillus et de are ecologically based.rCsineux sur un meme territoire sont de plus en plus fortes. 3) La In future, management systems will likely move away h m expencomprkhension sans cesse plus pousste des 6cosystbmes forestiers sive single species plantation systems and promote more mixed ainsi que les mouvements Ccologiques plus que prCsents ont forests. To retain the white spruce component of these forests, sysentrain6 des demandes pour des systkmes d'amhagement qui reposent tems must be developed that enhance natural regeneration of lower plus sur 1'Ccologie. Dans l'avenir, les systbmes d'amknagement densities of white spruce over a wider area. These must be coudevront vraisemblablement s'kloigner des systkmes o n k u x de planpled with refined harvesting techniques that protect spruce regentation contenant une seule es* et faire une plus grande promotion eration during the harvest of the aspen. Growth and yield moddes peuplements mtlangb. M n de conserver la portion d'kpinette els must accurately reflect the ecology of mixedwoods. Tenure blanche prCsente dans ces peuplements, des systbmes doivent Ctre systems should ...

Raptor electrocution mortality on power lines has been well documented over the past several decades, yet knowledge gaps, particularly regarding electrocution rates and estimates of losses, are still prevalent in the literature. Mortality estimates that do exist are often derived solely from utility outage records and exclude those not associated with a sustained outage. To address these shortcomings, we directly assessed raptor electrocution mortality beneath distribution power lines in east-central Alberta, Canada between June and August 2003. We also experimentally tested the effect of scavenger removal of carcasses. We observed the greatest rate of raptor mortality on transformer poles; 3-phase corner deadend poles were implicated in more incidents than expected based on proportional frequency, whereas tangent structures showed the opposite result. An estimated 94% of electrocution mortality was not associated with a power outage, indicating that utility outage data alone is insufficient to estimate incidence of electrocution. Scavenger removal rates were high, with >50% of the experimental carcasses removed within 7 days. Study results will assist utility companies and wildlife managers to better delineate structure retrofitting and new construction standards for structures that cause a disproportionately high number of raptor electrocutions, maximizing limited mitigation funds. Ó

There is currently considerable expansion of aspen utilization in the Prairie Provinces, and particularly in Alberta. This expansion includes the establishment of both oriented strand board mill capacity and pulp mill capacity. The pulp mill expansion is geared predominantly to aspen utilization. These developments arise out of the adoption of new technology and are demand driven. In this paper, the derived demand for aspen roundwood is examined. It includes a review of panel product and pulp consumption patterns. On the supply side, factors such as stumpage availability are examined. There is some uncertainty about the economic viability of aspen utilization as a result of demand and trade patterns as well as domestic and trade policies. The paper concludes with an examination of some current policy issues and the manner in which they may affect the future of aspen utilization.

The effects of boundary designations of timber management units on the allowable cuts were examined, and a new approach to derive marginal-cost curves for timber supply was developed. The maximum even-flow allowable cut from the whole forest as a unit was 1.33–2.13% larger than the sum of the five maximum even-flow allowable cuts from the five working circles. Maximum even-flow allowable cuts found with linear programming using stand aggregation were 1.31–2.10% larger than allowable cuts using area aggregation. Maximum per period cost constraints were found, on average, to increase predicted differences from unconstrained stand-based versus area-based analysis. Use of the maximum cost constraints led to the ability to develop curves for the marginal cost of allowable cut for both stand-based and area-based analyses. By incrementally examining increases in the allowable cuts generated on the independent management units at different cost constraints, a curve for the average marginal cost of allowable cut was derived. Careful use of this curve will allow woodland managers to select the least costly method of analysis for any particular desired allowable cut. As well, the selected curve can aid managers in determining the marginal cost of timber supply at any production level and to set upper limits on external wood purchase prices. While biological data were easier to derive for stand-based aggregation, area-based aggregation led to smaller linear programming models, which were thus cheaper to solve, and it was much easier to develop location-dependent economic data for these type models than for stand-based models.

When inflexible rotation ages for regenerated timber are coupled with a strictly interpreted policy of nondeclining or even flow of timber volume, a mathematically feasible harvest schedule often does not exist. This problem of infeasibility can be avoided by relaxing the definition of even or nondeclining flow used in the postconversion period of the Timber Resources Allocation Method (RAM). Relaxed flow policies can lead to scheduled harvest volumes which fluctuate greatly from decade to decade in the postconversion period. Explicitly planning for these fluctuations seems to violate the principle of sustained yield and some believe it may lead to a poorly regulated forest. However, when frequent review and reassessment of harvest schedules for two Alberta forest management units were simulated, undesirable fluctuations in future harvest volumes did not occur and the resulting forest structures were reasonably regular.