Abstract

The effect of shelter tubes on plant performance has been widely studied. Although, the role of shelter tubes in alleviating the effects of drought and high-irradiance stresses during seedling establishment has been less studied than its effect on survival. The present study compares the effects of shelter tubes with different light transmissivities (Lt) on survival and morpho-physiological responses of two coexisting tree species (drought-tolerant Quillaja saponaria and relatively more drought-sensitive Maytenus boaria) of the Chilean matorral during an exceptionally dry and warm growing season (2014-2015). Two-year-old seedlings were randomly assigned to shelter tubes differing in Lt (20, 40, 60, 80%) or to a control (no shelter, Lt 100%) at field conditions. Survival was measured monthly, while shoot and root biomass, root length, pre-dawn xylem water potential, and non-structural carbohydrate concentration (NSC) were measured 8 months after transplanting. Shelter tubes increased the seedling survival of Q. saponaria by 80-100% relative to the control conditions, where full mortality was observed by the end of the experiment. By contrast, M. boaria exhibited high mortality regardless of the presence of shelters, suggesting that tubes were ineffective to alleviate the summer-related stresses in this species. Xylem water potential of Q. saponaria seedlings was significantly lower at 80% Lt than at 40% Lt, where maximum values were observed. Also, at 40% Lt, plant height and root length were highest and shoot/root ratio the lowest. By contrast, no differences in NSC, stomatal conductance, and photochemical efficiency were observed among Lt treatments. We conclude that shelter tubes may alleviate summer stresses in drought-tolerant species such as Q. saponaria; hence, they appear to be effective reforestation ecotechnology under severe water limitations and high-irradiance stress imposed by the current drought and heatwaves conditions in central Chile.