Non-destructive estimation of Leaf Area Index in vase-shape sweet cherry trees
2014
Hochmaier, V. | San Martino, L. | Cittadini, E.D.
Knowledge of the Leaf Area Index (LAI) of sweet cherry orchards is important for diagnosis of their production potential. However, measuring LA/tree (for further calculation of LAI) is tedious and therefore seldom performed in commercial orchards. The objective of this research was to develop simple, precise and non-destructive methods for estimating LAI in vase-shape trees. Fifteen ‘Bing’ and 15 ‘Lapins’ trees grafted on Mahaleb were selected as experimental units. At full canopy, all leaves of each tree were counted and 2%, 5% or 10% of the leaves (for small, medium and big trees, respectively) were randomly taken as a sample, from which Mean Leaf Area (MLA; cm2) was estimated. Leaf Area (LA) per tree was calculated multiplying the number of leaves by MLA. At the same time, several parameters were recorded: Trunk Cross-Sectional Area (TCSA; cm2) (5 cm above the graft), a Tree Canopy Volume Estimate (TCVE; m3) (mean height x mean width), Free Between-Row Distance (FBRD; m), the LA of the Main Branch with the closest circumference to the mean (LAMB; m2), the Vertical Optical Porosity (VOP; %) and the Intercepted Photosynthetically Active Radiation (I-PAR; %) at noon. Simple and multiple linear regression models were evaluated using, in all cases, the measured LA/tree (varying between 2.55 and 35.76 m2) as dependent variable. The best models were: Ln LA/tree = -3.42 + 0.50 ln TCVE + 0.57 ln TCSA + 0.66 ln MLA (R2 = 0.98); Ln LA/tree = -0.76 + 0.68 ln TCVE + 0.38 ln TCSA (R2 = 0.95); Ln LA/tree = -0.86 + 0.41 ln MLA + 0.89 ln TCVE (R2 = 0.95) and Ln LA/tree = -6.35 + 1.02 ln MLA + 1.17 ln TCSA (R2 = 0.93). The LAI was calculated by dividing the estimated LA/tree by the tree-allocated area.
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