Patterns of change of saturated sapwood permeability and sapwood conductance with stand development

Abstract

The saturated sapwood permeability (k) of jack pine (Pinusbanksiana Lamb.) from stands of different ages and site qualities was measured using a constant water flow apparatus. Saturated sapwood permeability at the base of the live crown (BLC) increased with age and reached a plateau just beyond 4 × 10−12 m2. The rate at which this plateau was reached, however, was dependent on site quality. Such age-related increases in k can partially explain how trees can maintain similar daytime leaf water potentials at different stages of stand development. Within age-classes 15 and 35, k at BLC was greater on the better-quality sites and was strongly correlated with both diameter and height growth. For age-class 120, k at BLC was not significantly different among sites. Saturated sapwood permeability at BLC could be predicted from age and site quality, using a negative exponential function (R2 = 0.66). The ability to predict changes in k with stand development has potential for improving leaf area estimates derived from sapwood area -leaf area correlations. Sapwood conductance from ground level to the upper third of the crown decreased with age for good-quality sites and increased with age for poor-quality sites. It corresponded to the pattern of average annual height growth over the last 5 years (R2 = 0.61). The number of annual rings contributing to the sapwood at a given age was independent of site quality. This suggests that the historical reconstruction of a tree's leaf area and growth efficiency is possible even after the formation of significant amounts of heartwood.

Resistance to water flow in xylem of Picea abies (L.) Karst. trees grown under contrasting light conditions

“…In middle-aged Pinus banksiana trees the trunk resistance was found to increase with decreasing site index. The xylem resistances on the best and poorest sites differed by 2 orders of magnitude (Pothier et al 1989b), a difference similar to that between open-and shade-grown Norway spruce trees in this study. Sapwood resistance of the trunk in spruce from ground level to the upper third of the crown coincides with the values reported for P. banksiana trees of corresponding age and vigour (Pothier et al 1989 b).…”

The effect of tree height on crown level stomatal conductance

“…The k Shoot will also be inversely proportional to the length (or height, h) of the shoot for the same length-and area-specific sapwood conductivity (defined as flow rate per pressure gradient per sapwood area). Limited information available from a study on pine shows that variations in sapwood conductivity are weakly related to age between 40 and 140 years, the range of ages for the beech in this study (Pothier, Margolis & Waring 1989b;Pothier et al 1989a), and direct measurements of hydraulic conductance are consistent with an inverse relationship to height (Mencuccini & Grace 1996). Combining these proportionalities gives:…”

Temporal and spatial variation in transpiration of Norway spruce stands within a forested catchment of the Fichtelgebirge, Germany

“…Pothier et al [52] found that sapwood permeability increases with increasing age, which is partly due to an increase in tracheid length. Pothier et al [53] [38] and tree age [75], due to differing nutrition, or due to acclimation along light gradients within the canopy [48,49] and if the distribution of tree structures within stands are considered.…”