Measuring and modeling surface area of ponderosa pine needles

Abstract

Two methods for needle area estimation were compared for Pinus ponderosa Dougl. ex P. Laws. & C. Laws., and models were developed to predict total, projected, and abaxial areas. Areas of needles were determined by using video capture – image analysis procedures (VCIA) and by direct measurement of needle sections. VCIA area estimates were 40–60% less than abaxial areas determined from direct measurements. Allometric models fit to VCIA area and mean needle width (Wv) explained 96% of the variation in measured sample areas; models omitting Wv explained 91% of the variation. Predictions for independently collected validation data were somewhat poorer and slightly biased but had similar residual patterns. Allometric models fit to midneedle width and total needle length explained 99% of the variation in directly measured needle areas, with root mean square error equal to 2% of the mean measured areas. Results were similar for the validation data. For both models, final parameters were estimated from the combined data. It is shown that fascicle areas estimated from predictions for the middle-sized needles are nearly as accurate as estimates based on measurements for entire fascicles. Direct measurement of needles is more portable than VCIA and provides more accurate needle area estimates with less measurement effort.

Sources of within- and between-stand variability in specific leaf area of three ecologically distinct conifer species

“…This confounding of species and measurement technique has the potential for introducing only minor measurement error for Douglas-fir and hybrid spruce due to their small and relatively flat needles. The use of image analysis to measure ponderosa pine needle surface area has been shown to be biased when compared to direct measurements [48]. However, pine surface area determined by image analysis can explain nearly 91% of the variation in measured surface area [48].…”

“…The use of image analysis to measure ponderosa pine needle surface area has been shown to be biased when compared to direct measurements [48]. However, pine surface area determined by image analysis can explain nearly 91% of the variation in measured surface area [48]. Although the ponderosa pine SLA values reported in this study may be biased for estimating alternative expressions of total surface area, our definition of SLA on the basis of projected leaf area was expedient to measure and served well as an indicator of needle condition and light gradients within crowns, between trees, and among stands.…”

Photosynthetic performance of invasivePinus ponderosaandJuniperus virginianaseedlings under gradual soil water depletion

“…Gas exchange expressed on a leaf area basis [for J. virginiana based on linear regressions, Cregg (1991), and for P. ponderosa based on needle dimensions, Wykoff (2002)] was followed on five individuals per species with a portable photosynthetic system mounted with a fluorescence chamber (LI‐6400‐40; Li‐Cor Inc, Lincoln, NE, USA). Measurements started at around 10:00 (∼3 h after the beginning of the light period) and were completed at latest by 13:00.…”

Seedling establishment and physiological responses to temporal and spatial soil moisture changes

“…Total leaf biomass was converted to total leaf area using the specific leaf area (SLA) value of b Fig. 1 Volumetric soil moisture h (a) and water potential W soil at five depths (15, 30, 50, 70 and 90 cm) with precipitation measurements ( 51.6 cm 2 g -1 from a nearby population of P. ponderosa (Zhang and Marshall 1995); because this SLA represents a one-sided projected leaf area, the value was multiplied by 2.5, based on trigonometric analysis, to match the three-dimensional value of leaf area measured in this study (adapted from Hultine andWykoff 2002).…”