title: Sapling leaf trait responses to light, tree height and soil nutrients for three conifer species of contrasting shade tolerance.
abstract: We developed models to describe the responses of four commonly examined leaf traits (mass per area, weight, area and nitrogen (N) concentration) to gradients of light, soil nutrients and tree height in three conifer species of contrasting shade tolerance. Our observational dataset from the sub-boreal spruce forests of British Columbia included subalpine fir (Abies lasioscarpa [Hook.] Nutt; high shade tolerance), interior spruce (Picea glauca × Picea engelmannii [Moench] Voss; intermediate shade tolerance) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia; low shade tolerance) saplings from 0.18 to 4.87 m tall, in 8-98% of total incident light, from field sites with <17.6 kg ha(-1) to >46.8 kg ha(-1) total dissolved N. Leaf weights and areas showed strong positive responses to light and height, but little or no response to soil nutrients. Parameter estimates indicated that the shape of leaf weight and area responses to light corresponded with shade tolerance ranking for the three species; pine had the most linear response whereas spruce and fir had asymptotic responses. Leaf N concentration responded positively to soil nutrients, negatively to light and idiosyncratically to height. The negative effect of light was only apparent on sites of high soil nutrient availability, and parameter estimates for the shape of the negative response also corresponded to shade tolerance ranking (apine = -0.79, aspruce = -0.15, afir = -0.07). Of the traits we measured, leaf mass per area showed the least response to light, soil nutrient and height gradients. Although it is a common practice in comparisons across many species, characterizing these conifers by mean values of their leaf traits would miss important intraspecific variation across environmental and size gradients. In these forests, parameter estimates representing the intraspecific variability of leaf trait responses can be used to understand relative shade tolerances.
authors.affiliation: Bulkley Valley Centre for Natural Resources Research and Management, Box 4274, Smithers, BC V0J 2N0, Canada erica.lilles@bvcentre.ca.
authors.forename: Erica B
authors.initials: EB
authors.lastname: Lilles
authors.affiliation: Bulkley Valley Centre for Natural Resources Research and Management, Box 4274, Smithers, BC V0J 2N0, Canada Norwegian Forest and Landscape Institute, Høgskoleveien 8, Postboks 115, 1431 Ås, Norway.
authors.forename: Rasmus
authors.initials: R
authors.lastname: Astrup
authors.affiliation: Bulkley Valley Centre for Natural Resources Research and Management, Box 4274, Smithers, BC V0J 2N0, Canada.
authors.forename: Marie-Lou
authors.initials: ML
authors.lastname: Lefrançois
authors.affiliation: Bulkley Valley Centre for Natural Resources Research and Management, Box 4274, Smithers, BC V0J 2N0, Canada Ministry of Forests, Lands and Natural Resource Operations, Bag 6000, Smithers, BC V0J2N0, Canada.
authors.forename: K
authors.initials: K
authors.lastname: David Coates
mesh_terms: D028202:Abies / Q000254:growth & development / Q000502:physiology; D000222:Adaptation, Physiological; D001955:British Columbia; D003624:Darkness; D008027:Light; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism; D010788:Photosynthesis; D028222:Picea / Q000254:growth & development / Q000502:physiology; D028201:Pinaceae / Q000254:growth & development / Q000502:physiology*; D028223:Pinus / Q000254:growth & development / Q000502:physiology; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology*; D036226:Seedlings; D012987:Soil / Q000737:chemistry*; D013312:Stress, Physiological; D014197:Trees / Q000502:physiology
chemical_list: D012987:Soil; D009584:Nitrogen
keywords: interior spruce; intraspecific variation; leaf area; leaf mass per area; leaf nitrogen concentration; leaf weight; lodgepole pine; sub-boreal forest; subalpine fir