Does facilitation from adult conspecifics increase sapling resilience to repeated droughts in water-limited pine forest?

Recruitment is a bottleneck for forest regeneration especially in semi-arid Mediterranean environments.Ensuring natural forest regeneration is vital for preserving ecosystem function under climatewarming and increased frequency and intensity of extreme droughts. Interspecific positive interactions areof paramount importance in these ecosystems. The net outcome of conspecific plant interactions in semiaridforests, however, has been less explored, particularly the range of environmental conditions for whichjuveniles benefit from nursing effects. We evaluated the direction and magnitude of intraspecific relationshipsbetween adults and juveniles of Pinus pinaster in a dry continental Mediterranean forest in the IberianPeninsula. We measured the longitudinal shoot elongation of the last 15 yr and foliar functional traits inpine saplings growing under the canopy of adult pines and in open habitats. We examined the growthresponse to precipitation and the resilience and resistance of growth to two extreme drought events in2005 and 2012. Our results show likely facilitation of saplings by adult conspecifics. Nursed saplings had agreater size relative to age, longer needles, and faster shoot elongation than saplings in open habitats. Inaddition, saplings under the canopy were more resistant and resilient to the first severe drought event.
Ministerio de Economía y Empresa
Comunidad de Madrid