Post-dispersal predation of Pinus pinaster Aiton seeds: key factors and effects on below-ground seed bank.

Abstract

Seed bank dynamics constitute a pool of natural regeneration, a complex and key process for stand persistence. The present work analyses post-dispersal predation on a Pinus pinaster Ait. (Maritime Pine) below-ground seed bank. The study was carried out at the experimental site of Mata de Cuellar (Segovia-Central Spain), where an integrated analysis of Maritime Pine regeneration has been underway since 2004. Seed predation was monitored every month from 2010 to 2013. A generalized linear model was fitted using ‘next spring seed density’ as the response variable and seed rain, micro-site conditions and annual climate variability as explanatory variables. Seed rain, distance to the nearest stump, basal area and Walter’s drought index, along with percentage cover of herbaceous species, pine needle litter and shrub species had significant positive effects. The number of neighbouring trees had a significant negative effect on seed density. These results demonstrate how seed rain, summer drought and micro-site conditions are crucial to understanding the effects of predation on the below-ground seed bank. Though greater than null, the final seed bank might be insufficient for successful natural regeneration due to high mortality caused by difficult germination and establishment conditions.