<em>Araucaria araucana</em> (Molina) K. Koch seed production during 15 years at different populations in Lanín National Park (Neuquén-Argentina)

Abstract

Ecología Austral, 24:265-275 (2014)

Seed production studies on tree species are important for science and for forest management. The objective of this work was to study the long term seed production of araucaria (Araucaria araucana), which are a valuable food for humans, at populations located at different aspect, altitude and with variations on forest structure and composition. Cones were counted at seven populations in Lanín National Park, Neuquén Province, Argentina for 15 years (2000 to 2014), estimating seeds and cones per tree, per hectare and per population. Peaks in seed production occurred in 2000, 2007 and 2013, while seed crops were low during 2005, 2008, 2012 and 2014. Mean cones per tree was 19 (range: 1-62) with 56 fold variation among years. Mean seeds per tree was 2372 (range: 61-9287) with 152 fold variation among years. The greater temporal variation in seed production in relation to cones was due to a significant increase in seeds per cone during mast years. Mean cones, individual seeds and kilograms of seeds per hectare were 685, 89394 and 273, respectively. Dense and pure Araucaria forests and those mixed with lenga (Nothofagus pumilio) were at least 2.5 and 1.5 fold more productive than the rest of forest types. Cones per tree differed significantly among sites and were related mainly with sun exposure. However, this effect varied according to the class productive year and the observed pattern may be related with the floral bud formation associated with drought. Araucaria showed a synchronous reproduction between trees and populations at regional scale, with a greater temporal variability than spatial variation between populations. These results could be important for conservation planning of these forests in Argentina and Chile against the threats posed by increased seed gathering pressure and by the presence of exotic invasive granivores.