Survival and growth of seedlings from five Pinus pinaster Ait. provenances grown under different water regimes

Abstract

Survival and growth parameters were measured in five Pinus pinaster Ait. provenances (Oria, Arenas de San Pedro, Oña, San Leonardo and Landas). Plantas were grown in nursery under cover in two different growing media, during one growing season and they were submitted to three water supply regimes, R1, R2, R3, set to field capacity every 1, 2 and 3 weeks respectively. General results show significative differences for water supply regimes, as well as for provenances and growing medium. With low water supply (R3) the growing medium with higher water storage capacity allows higher survival (80 p. 100) than the other (20 p. 100). The lowest survival is correlated to water potential less than -2.6 MPa. Landes and Arenas provenances show the highest height growth, Oria the lowest one. A common pattern to stop growth at the end of summer may be atributed to photoperiod reduction since temperature still allows growth. Significant differences throughout the growing season are found for seedling dry weight, mainly shoot weight, for provenances and for water supply regimes, as well as for their interaction; but water disponibility changes the ranking of provenances. Relative growth rate (RGR) is higher for R1. The water stress (R2, R3) has on RGR different effect among provenances and the ranking for them is not the same as for total dry weight at the end of growing period. Net assimilation rate (NAR) and RGR are positively correlated except for the end of summer. Low values for specific leaf area (SLA) and for leaf area ratio (LAR) point out a strategy to avoid lost of water. Their decrease in autumn is higher for R1 than for R2 and R3; it is expressed in higher dry weight and subsequent higher dry weight and subsequent higher reserves storage, since the growth height does not progress any more. It is concluded that under favourable water disponibility growth parameters in the first growing season, may be used as estimative criteria to predict future performance of provenances in the field.