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UBC Theses and Dissertations

Net primary production of lodgepole pine (Pinus Contort A var. Latifolia engelm.) in some ecosystems in Southeastern British Columbia Comeau, Philip George


Relationships between net primary production and tree canopy parameters were investigated in 30 unmanaged stands of lodgepole pine (Pinus contort a var. I atifolia Engelm.) growing on sites with two contrasting hygrotopes (soil moisture regimes) and two contrasting trophotopes (soil nutrient regimes) in southeastern British Columbia. Sampled stands were between 50 and 130 years-of-age. Estimates of aboveground production (ANPP) were obtained for all 30 stands, and estimates of total (aboveground plus belowground) production (TNPP) were obtained for four stands. ANPP ranged from 2.2 to 4.4 t ha⁻¹yr⁻¹ for the xeric hygrotopes and from 2.9 to 7.4 t ha⁻¹yr⁻¹ for the sites with mesic hygrotopes. Variation in ANPP was explained by variation in stand foliage biomass, stand density, and age. Multiple regression equations fitted to data from each hygrotope differed significantly (a=0.05). The higher rates of ANPP observed in stands from mesic sites were attributed to the larger quantities of foliage biomass and to greater ANPP per kg of foliage (Foliage Efficiency) than in stands from the xeric sites. Total net primary production ranged from 7.9 to 11.9 t ha⁻¹yr⁻¹ in four stands. Belowground net primary production averaged 60% of TNPP on the two xeric sites and 42% of TNPP on the two mesic sites. This difference in production allocation between the two hygrotopes explains some of the between-site variation in foliage efficiency which was not accounted for by variation in foliage biomass. On the xeric sites, where moisture deficiencies appear to be limiting production, a multiple regression equation using foliage biomass, stand density, and stand age provided a better prediction of ANPP than did an equation which used foliage nitrogen content, stand density and stand age. Stand foliage biomass and stand density were significant variables in describing variation in foliage nitrogen efficiency (ANPP per kg of foliage nitrogen; an extension of the concept of "nitrogen productivity"). Either foliage efficiency or foliage nitrogen efficiency, in combination with data on the allocation of TNPP offer potentially useful alternatives to carbon budgets as driving functions for simulation models of forest production.

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