Principles of Grapevine Canopy Microclimate Manipulation with Implications for Yield and Quality. A Review

This paper develops concepts of grapevine canopy microclimate by considering how the canopy presence can alter the climate. Solar radiation levels are particularly affected due to high absorption by leaves. The radiation environment of canopy exteriors is shown to depend on vineyard geometry and ambient radiation levels. The number of leaf layers within grapevine canopies determines the degree of shading, and an optimal canopy density of about three leaf layers is advocated. Three means of altering canopy microclimate are discussed: shoot number control, vigor control, and use of training systems. The interaction between row spacing, shoot number, vigor, and leaf angle in affecting canopy density is illustrated. Within-canopy shading is promoted by high shoot numbers per hectare, wide row spacing, high vine vigor, and vertical leaves. Examples are given of the effect of reduced vigor on improving canopy microclimate. An analysis of different training systems shows that shading is reduced with narrow rows or by canopy division. The review concludes by considering the effects of canopy microclimate on yield, fruit and wine composition, and offers points for further research.