Digital photographs were taken of four 1 m × 1 m portions of canopy of Cabernet Sauvignon grapevines, as they were being progressively de‐fruited close to harvest. The program EasyAccess version 6.3 was used to select ‘fruit’ pixels by visually setting red, green and blue threshold values and tolerances for the first image and applying these to all other images. The program was then used to automatically count ‘fruit’ pixels and the total number of pixels for each image. Even though two hours separated the first and last photographs, the ratio of ‘fruit’ pixels to total image pixels explained 85% of the variation in yield (kg per linear m of fruiting wire) for all 16 vine × de‐fruiting combinations. This improved to between 94 and 99% for individual portions of canopy. Implications from our present digital image analysis for future development of both automated and spatially aware methods to predict vineyard yield are discussed.

Diurnal measurements of sap velocity were made in 50-, 90-, 150- and 230-year-old mountain ash (Eucalyptus regnans F. Muell.) forests in the North Maroondah catchment (southeast Australia) over the periods January 8, 1990 to April 4, 1990 and October 29, 1990 to April 16, 1991. Over the two periods, daily mean sap velocities for the four forests, in order of increasing age, were 11.5, 11.4, 9.9 and 11.8 cm h(-1) respectively. Daily mean sap velocity did not differ significantly among the 50-, 90- and 230-year-old plots. However, in the 150-year-old trees it was significantly smaller by an average of 14%. Sap velocity varied diurnally and also between positions within individual trees and among trees both within and between stands. Despite this variability, the sampling intensity and duration were sufficient to establish that behavior was highly correlated among individuals within plots. There was a significant decline with age in the overstory sapwood conducting area of these forests. In order of increasing age, the values were 6.7, 6.1, 4.2 and 4.0 m(-2) ha(-1), respectively. When combined with daily mean sap velocity, these data allowed the calculation of overstory water use. Over the experimental period, water use of the overstory decreased with age ranging, on average, from 1.86 mm day(-1) for the 50-year-old plot to 0.81 mm day(-1) for the 230-year-old plot. Mean daily water use for the two intermediate-aged forests was 1.67 and 1.00 mm day(-1), respectively. Annual water use decreased with forest age from 679 mm for the 50-year-old stand to 296 mm for the 230-year-old stand. This difference corresponds to 3.8 x 10(3) m(3) ha(-1). The annual water use of the intermediate-aged stands was 610 and 365 mm for the 90- and 150-year-old stands, respectively.

No abstract

No abstract

The number of primary branches (those branches that arise directly from the rachis) and the total number of flowers were counted for inflorescences of Vitis vinifera L. cultivar Cabernet Sauvignon over a range of climates and a number of seasons as part of a yield prediction study. Regression analysis indicated that the number of primary branches per inflorescence exerted a strong control over the total number of flowers per inflorescence, with highly significant (P < 0.01) relationships explaining between 51 and 80% of the variation in flowers per inflorescence. Because the extent of primary branching is largely determined prior to grapevine buds entering dormancy, this strong functional association between branching and flower numbers, suggests that season‐to‐season differences in potential inflorescence size will be greatly affected by conditions during that phase of primordial differentiation in the previous growing season. A general tendency for the number of flowers per inflorescence to be positively related to other measures of vine fertility, supports this view. Lower orders of branching (secondary and tertiary) down to formation of individual flowers at budburst, also have the potential to influence eventual inflorescence size. As to the timing of such influences, we noted that increased severity of winter pruning significantly increased both flowers per inflorescence (by 9%) and the number of primary branches per inflorescence (by 21%). Such responses provide strong support for our contention that although the extent of primary branching is largely determined prior to grapevine buds entering dormancy, differentiation of new primary branches in Cabernet Sauvignon inflorescences continues to occur after the onset of dormancy.