Extreme climate conditions limit seed availability to successfully attain natural regeneration of Pinus pinaster in sandy areas of Central Spain

Natural regeneration comprises different sub-processes, each of them driven by specific climatic and stand-related factors, which determine the success of natural regeneration. The objective of this study was to investigate the seed production and seed rain interannual patternavailability of maritime pine. To meet this objective seed rain was monitored for four different levels of stand density at the experimental site of Cuéllar, Spain, during a ten-year period. A generalized linear mixed model was fitted to test the effects of climatic variables and stand density on the annual seed production and seed rain. The climatic covariates were chosen among those thought to affect the key physiological phases governing these sub-processes: minimum temperature in October two years before dispersal (cone growing), April precipitation one year before dispersal (cone growing) and October-November precipitation one year before dispersal (cone maturation). No climate variable related to flowering or seed rain process was significant. Moreover, stand density was considered through a spatially explicit index called seed-source index. Primary cone growth was limited by extreme cold events. Absence of precipitation limits secondary growth while it appears to hinder final cone ripering. It turns out that seed production and seed rain may be a bottleneck for natural regeneration of Pinus pinaster under low stand densities, especially under extreme climatic scenarios.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author