A new method for measuring stand sapwood area in forests

Abstract

We introduce a novel methodology for measuring stand sapwood area (SA), which provides a useful indicator of evapotranspiration from forest stands. The method is demonstrated in a 73‐year‐old Eucalyptus regnans forest comprising 784 stems over a 5 ha area. We used photos of stump cross‐sections to differentiate sapwood from heartwood and found 90% of stump segments to have a visible transition boundary. The digital images were corrected for lens distortion and scaled to an actual cross‐sectional area, with resulting stump perimeters corresponding well with field‐measured perimeters traced using string (root‐mean‐square error = 4 cm, R2 = 0.99). Calculated SA and basal area (BA) at stump height were coupled with tree and sapwood taper data to predict the SA:BA ratio at 1.3 m height (italicRtrue^1.3). Tree taper data were coupled with stump dimensions data in a mixed‐effects model to predict each stump's BA at 1.3 m, and sapwood taper data from buttress logs were used to improve each stems italicRtrue^1.3. Using this procedure, we found our study site to have an italicRtrue^1.3 of 0.21 and total stand SA at 1.3 m height of 9.3 m2 ha−1. We quantified the bias in traditional italicRtrue^1.3 estimates that use cores to measure sapwood thickness and diameter tape to calculate SA. We show traditional methods underestimate italicRtrue^1.3 that increases with tree diameter and decreases with stem circularity, whereas our methodology gave more accurate measures of SA in large buttressing trees. Our methodology also provides a more efficient way of generating maps of SA variation across large forested catchments. Copyright © 2014 John Wiley & Sons, Ltd.

Novel 3D geometry and models of the lower regions of large trees for use in carbon accounting of primary forests

“…The study by Sillett et al (2015) focussed on tall trees, which may be subject to greater wind stress. Jaskierniak et al (2014) showed a slightly larger area deficit of 27 % for Victorian E. regnans up to DBH of ~1.4 m, compared with the 21 % in the present work, and they concluded that the measured diameter is more erroneous as tree size increases. Similarly, the formulas in Sillett et al (2015) imply that the percentage deficit increases with DBH.…”

Tree Water Dynamics in a Semi-Arid, Pinus brutia Forest

“…The accuracy of sap flow measurements and the upscaling of these to the whole-plant water use relies on the knowledge of species-specific physiological characteristics, as well as on information of radial and circumferential patterns of sap velocity [6][7][8]. Most sap flow studies assume that the tree stem and sapwood are perfectly circular in cross-section, but in reality trees are rarely entirely circular [9]. The spatial configuration of the sapwood affects tree hydraulic properties and environmental adaptation [10].…”

Upscaling Stem to Community-Level Transpiration for Two Sand-Fixing Plants: Salix gordejevii and Caragana microphylla

“…Previous studies on upscaling of transpiration mainly focused on tall trees or vegetation types with a high canopy density, with independent variables (i.e., upscaling factors) of woodland area [18,19], canopy overlap [20], sapwood area [21], and/or diameter at breast height [22]. The accuracy of the upscaling results largely depended on the scalar multipliers of these independent variables between the shrub community and its individual members.…”