Allometric relationships to estimate seasonal above-ground vegetative and reproductive biomass of Vitis vinifera L

Abstract

A procedure is described for obtaining allometric regression equations to estimate non-destructively and in a cost-effective manner the current year's above-ground vegetative and reproductive biomass of Vitis vinifera L. Merlot' throughout the growing season. Significant relationships were obtained over a 3-year period (1998-2000) between the dimensions of an individual shoot per vine (i.e. diameter and length) and dry weights of its primary stem, primary leaves and lateral growth. The dry mass of a grape was best estimated from measurements of the basal diameter of the bunch peduncle. Introducing cumulative degree-days as an additional explanatory variable in the equations allowed them to be used irrespective of year and growth stage. Multi-year regressions were used to quantify in detail the seasonal evolution of mature grapevine biomass under the climatic conditions of the Bordeaux area, France, and for differing levels of soil nitrogen.

Fig. 1.  Seasonal course of averaged primary stem density (mg f. wt cm^–3) measured in 1999 on subsamples of 15 shoots per sampling date. Cumulative degree‐days were calculated from 1 Jan. 1999 using a base temperature of 10 °C. Vertical bars represent s.e.m. n = 15.

Fig. 2.  Allometric relationships between primary stem dry mass (W_ps, in g) and a combination of squared mid‐length diameter and length of the primary stem (D_m²L, in cm³) for five sampling dates in 1999 (see Table 1).

Fig. 3.  Comparison of field measurements and predicted values from multi‐year regression equations for various above‐ground components of a vine shoot. Each point represents the average value per date; horizontal and vertical bars represent s.e.m. n = 12–18.

Fig. 4.  Validation of multi‐year regression equations for various above‐ground components of a vine shoot. Data were collected on 9 Sep. 2000 (doy = 253) within the four experimental plots. n = 60.

Fig. 5.  Predicted seasonal evolution of mean dry mass (g per vine) for primary stems (A), vegetative (B) and reproductive parts (C) of grapevine grown under four levels of soil N. G₀, G₅₀, G₁₀₀ and S represent ungrassed (circles), half‐grassed (diamonds), fully‐grassed (triangles) and gravelly soil (crosses) plots, respectively. Data were estimated for both years using the same multi‐year allometric regression equations defined in Table 2. For legibility, s.e.m. is not plotted.

Fig. 6.  Comparison of measured mean dry mass values per vine of grapes (A) or total stems (B) to predicted values estimated from multi‐year regression equations. (See Table 1 for more information concerning sampling calendar). G₀, G₅₀, G₁₀₀ and S represent ungrassed, half‐grassed, fully‐grassed and gravelly soil plots, respectively. Vertical and horizontal bars represent s.e.m. Solid and dashed lines represent the least square regression and the 1 : 1 line between measured and predicted values, respectively.