Abstract
This paper analyzes sapwood variability and allometry within individuals of Populus tremuloides, Pinus contorta, Pinus banksiana, Picea mariana, and Picea glauca. Outside bark diameter at breast height (DBH) and sapwood depth (sd) in four cardinal directions were measured in individuals in stands in Alberta and Saskatchewan, Canada. The microscopical analysis of wood anatomy was used to measure sd, and the error associated with the measures was observed. Sapwood allometry analyses examined the influence of DBH on sd and on sapwood area (SA). All species were observed to have varying sapwood depths around the trunk with statistical analyses showing that Pinus banksiana has a well defined preference to grow thicker in the North-East side. The largest sd values were observed for the Populus tremuloides set. Unlike Populus tremuloides and Picea glauca, for the species Pinus contorta, Pinus banksiana, and Picea mariana, incremental growth in DBH does not directly drive sapwood growth in any direction. For these three species, SA increases only because of increases in DBH as sd remains nearly constant. These results show that sapwood depth and sapwood area seem to behave differently in each studied species and are not always proportional to the tree size as is normally assumed.
Highlights
Cross-sectional sapwood area (SA) is commonly used as a scaling parameter to obtain tree sap flow rates and is considered a strong predictor of tree- and plot-level leaf area, leaf biomass, and leaf area index [1,2,3,4,5,6,7,8,9,10]
It is well known that sapwood depth is heterogeneous around the tree trunk, and measuring sapwood depth from a single side of the tree may be non-representative of the total amount of sapwood, and will not be reflected in the allometric model
Pinus banksiana diameter at breast height (DBH) ranged from 11.5 cm to 23.9 cm
Summary
Cross-sectional sapwood area (SA) is commonly used as a scaling parameter to obtain tree sap flow rates and is considered a strong predictor of tree- and plot-level leaf area, leaf biomass, and leaf area index [1,2,3,4,5,6,7,8,9,10]. Studies have reported that sapwood depth has a high correlation with diameter at breast height and sapwood area [11,12,13,14,15,16,17]. Together with diameter at breast height, is considered a strong predictor of sapwood area. Sapwood morphological and physiological characteristics vary among species (e.g., color, water content, transition zones, wood tissues structure) and may constrain the accuracy of most methods used to measure sapwood depth [20], which can later lead to inaccurate conclusions regarding tree-water relationships [21,22,23]. Other studies have listed several issues related to the allometric models
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