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The leaf area to sapwood area ratio (A :A) of trees has been hypothesized to decrease as trees become older and taller. Theory suggests that A :A must decrease to maintain leaf-specific hydraulic sufficiency as path length, gravity, and tortuosity constrain whole-plant hydraulic conductance. We tested the hypothesis that A :A declines with tree height. Whole-tree A :A was measured on 15 individuals of Douglas-fir (Pseudotsuga menziesii var. menziesii) ranging in height from 13 to 62 m (aged 20-450 years). A :A declined substantially as height increased (P=0.02). Our test of the hypothesis that A :A declines with tree height was extended using a combination of original and published data on nine species across a range of maximum heights and climates. Meta-analysis of 13 whole-tree studies revealed a consistent and significant reduction in A :A with increasing height (P<0.05). However, two species (Picea abies and Abies balsamea) exhibited an increase in A :A with height, although the reason for this is not clear. The slope of the relationship between A :A and tree height (ΔA :A/Δh) was unrelated to mean annual precipitation. Maximum potential height was positively correlated with ΔA :A/Δh. The decrease in A :A with increasing tree size that we observed in the majority of species may be a homeostatic mechanism that partially compensates for decreased hydraulic conductance as trees grow in height.

Nutrient elements in grassland : soil-plant-animal relationships. Nutrient Elements in Grassland: Soil-Plant-Animal Relationships Image. Zoom Click to Enlarge. Out of Stock. Nutrient Elements in Grassland: Soil-Plant-Animal Nutrient elements in grassland: soil-plant-animal relationships.-DOI Nutrient Elements in Grassland: Soil-Plant-Animal Relationships. Nutrient Elements in Grassland: Soil Plant Animal Relationships. This book is an essential reference source covering the chemical elements that are Nutrient Elements in Grassland: Soil-plant-animal .-Google Books 2000. Nutrient elements in grassland. Soil-plant-animal relationships. 369 pp. Wallingford: CABI Publishing. £60 (hardback). John Scullion. in Annals of Botany. Whitehead DC. 2000. Nutrient elements in grassland. Soil-plant Nutrient Elements in Grassland: Soil-Plant-Animal Relationships. 2000. Nutrient elements in grassland. Soil-plant-animal relationships. 369 pp. Wallingford: CABI Publishing. £60 (hardback) on ResearchGate, the professional Nutrient elements in grassland : soil-plant-animal relationships in .

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The relationships between foliage area and sapwood area between trees and within the crowns of 20 Piceasitchensis (Bong.) Carr., provenance Queen Charlotte Island, British Columbia (10 in a control plot and 10 in a plot fertilized with potassium and phosphorus 8 years before harvest) and 10 Pinuscontorta Dougl., provenance Ladysmith trees were examined using a physiological analysis based on Darcy's law. Foliage area index on the fertilized P. sitchensis plot was higher than on the control. The variation of foliage area density with depth in the canopies followed a normal distribution. Relationships between foliage area and sapwood basal area were linear but the slopes were different for the two species. There was no significant difference between the control and fertilized P. sitchensis trees. The relationship between foliage area and the product of sapwood area and permeability was linear and data from the three plots fell on the same line. Sapwood area, permeability, and their product decreased with depth through the crowns of the trees. Within the crowns, relationships between cumulative foliage area and sapwood area, and between cumulative foliage area and the product of sapwood area × permeability were different with species and treatment. A single linear relationship resulted when the product of cumulative foliage area above an internode × the internode length was plotted against sapwood area × permeability for the internode. This suggests that it is the drop in potential across a node and internode rather than the gradient of potential across the internode that is related to the flux of water through tree crowns. The data support the hypothesis that the relationship between foliage area and sapwood area depends on permeability of the sapwood and the local climate through its influence on transpiration rate, particularly via average water vapour pressure deficit of the air and stomatal conductance.