Factors affecting variability in fleshy cone production of Juniperus macrocarpa

Abstract

Juniperus macrocarpa woodlands represent the mature ecosystem on outer sandy dunes and cliffs of the Mediterranean coasts, and typically show little or no recruitment in degraded coastal habitats. Production of fleshy cones may have strong effects on its recruitment as well as on the populations of animal species that eat the cones and disperse the seeds. In this study, I explore the inter-annual variability in cone production, its relationship with rainfall and twig growth, and the effects of silvicultural works carried out to increase the production of fleshy cones and natural regeneration of the species in Enebrales de Punta Umbría Natural Site. Silvicultural treatments had not a significant effect on the cone production, but microhabitat did. J. macrocarpa showed a variable fleshy cone production between years and synchronized fleshy cone production within years among individuals. Precipitation during the period of pollination negatively affected the production of fleshy cones which allow us to classify J. macrocarpa as a putative masting species. In clearing plants, twigs that produce many cones grew less than twigs without or with few cones, while cone production in understory plants was lower but increased with twig growth. All results seem to reinforce the fact that pollen is essential for seed cone development in J. macrocarpa, and that this is highly dependent on variation in climate (precipitation during the pollination period) and landscape features (pine plantation).