Physiological response of Beilschmiedia miersii to winter water stress in nursery trials

Beilchmiedia miersii (Gay) Kosterm (Belloto of the North), an endemic species of central Chile, belongs to the hydrophilous forest subtype within the sclerophyllous forest ecosystem; it is azonal in character and fragmented in distribution. Preferably, its populations are found near stream areas, given its high water needs, a situation that is aggravated by the intense and prolonged drought that affects the area where it grows. B. miersii faces strong environmental stress during the summer, and it is unknown if the reduction in precipitation also causes water stress during the winter. Therefore, we hypothesized that B. miersii would present a low level of stress under the water deficit during the winter season, a period in which climatic factors such as radiation, relative humidity and precipitation are less restrictive to vegetation. The field trial was established in a nursery in the Metropolitan Region of Chile and included two treatments: control (TRC) and restriction (TRR). In both treatments, growth (root collar diameter and length), biomass variation, leaf water potential and substrate water content were evaluated on days 1, 126 and 161. Contrary to our hypothesis, the results revealed that the winter water deficit generated stress in the TRR plants, leading to physiological and metabolic changes that negatively impacted their growth, development and biomass accumulation. In the short term, this resulted in a reduced capacity to face the adverse climatic conditions that occur during the summer period.