Multiple risk factors in root survivorship: a 4-year study in Concord grape

Minirhizotron techniques were used to examine root lifespan in Vitis labruscana (Concord grape) for roots born in four different years that varied in rainfall. Experimental vines were given irrigation (irrigated or not) and canopy pruning treatments (minimal or balanced). Root survival was assessed from 1997 through 2000 and analysed using Cox proportional hazards regression. Model covariates included pruning, irrigation, vine yield, soil depth, root diameter, time of root birth, and numbers of neighboring roots. Soil depth, root diameter and time of birth consistently influenced root lifespan in all years (P<0.05). Deeper and coarser roots had longer lifespans. Roots born near bloom were shorter-lived than roots born later in the season. Pruning and irrigation influenced root lifespan in some years but their effects seemed to vary with growing-season environmental conditions. These data underscore the value of long-term studies in distinguishing factors that consistently affect root lifespan from those that change annually with environmental conditions, and emphasize the diversity in life histories of fine roots within a species.