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The use of aerial photographs and sub sampling in the identification and assessment of moose ranges in southern British Columbia Baynes, Raymond Arthur

Abstract

A random sample of forty high altitude block vertical aerial photographs was drawn from two extensive districts of the south Cariboo region of British Columbia. The five hundred square miles of sample area so obtained was cover-typed through interpretation of the aerial photographs. Both mature and seral forest stages constituting moose habitat were identified primarily through the use of criteria which permitted the recognition of individual tree species and secondarily through the recognition of characteristics peculiar to the aspect of each forest type when viewed as a unit. Stereoscoptic examination permitted delimination of the types on the aerial photographs. Planimetric measurement of these areas followed. Sub—sampling of these areas resulted in the establishment of sixty—four permanent plots. Twelve thousand feet of line-interception transect data were obtained from the plots. Browse species were classified both for amount of available food and for degree of utilization by moose. Availability was largely determined by standards derived from shrub height and D.B.H., while utilization was categorized into four degrees on the basis of the amounts or the previous years twigs that had been removed from the shrub by the browsing of moose. Analysis of the ground shrub and tree layers resulted in distinctive floral compositions being obtained for seven forest types which constitute moose habitat. Characteristic intensities of browse utilization were also evident in each forest type—the more dense, mature forests receiving heavier usage than the open forest stands. Index ratings were established both for the density of available browse and for the degree or utilization of browse in each of the seven forest types, Application of these indices to the areas of each forest type indicated relative food productivity and usage of browse in the two sample districts. With the establishment of the indices, moose ranges in the remainder of the sample district may be assessed solely from aerial photographs thereby eliminating extensive ground survey, Extension of this method to other forest areas will permit similar assessment of moose habitat in these regions, once any new forest types are identified and valuated through limited ground subsampling. Severe browsing of unpalatable species, not generally consumed, indicated overuse of many moose winter ranges. Controlled burning of certain severely overbrowsed ranges and further reductions in the moose population through either-sex seasons are suggested.

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