SPATIAL VARIATION AND TEMPORAL PERSISTENCE OF GRAPEVINE RESPONSE TO ASOIL TEXTURE GRADIENT

Studying the water transport in the soil-plant system requires informa tion on the spatio-temporal variability of both subsystems and the abi lity to assess the impact of the soil heterogeneity and of the biologi cal responses on the coupling between vegetation and its substrate. Th is study was conducted for 2 years in a vineyard in the Aude Valley, F rance, by measuring the particle size distribution of the topsoil, the instantaneous isotopic ratios (O-18/O-16, H-2/H-1) of leaf water, ann ual shoot biomass production, and interannual persistence of this biom ass along a 360 m transect. The resultant spatial series were analysed for their correlations and converted to spectra. Changes in the isoto pic ratios along the transect reflect the soil texture gradient, sugge sting that the vines root deeper on the gravel layers than elsewhere. This could provide a mechanism for the partial decoupling between soil and vegetation, and thus explain (1) the strong temporal persistence of the vegetation pattern, (2) the low overall correlation between bio mass production and soil texture. The spectra show that this correlati on concentrates at specific scales which correspond to a minimum varia bility in the shoot biomass. In this case, therefore, soil texture pla ys only a minor role in determining the spatial heterogeneity of shoot biomass in grapevine.