The effects of resource availability on sprouting: a key trait influencing the population dynamics of a tree species.

Key message: Sprouting is a key component of the population dynamics of woody species. Regeneration via sprouting contributes substantially to population growth when resource availability varies. Abstract: Basal sprouting is an important trait that facilitates the persistence of woody species under different environmental conditions. Environmental heterogeneity can have variable effects on allocation to sexual reproduction and vegetative growth over an individual's ontogeny; consequently, environmental heterogeneity can influence the dynamics of woody plant populations. However, the effects of environmental factors on the ramet and genet dynamics of woody species have yet to be fully explored. This study investigated the population dynamics of Curatella americana L. (Dilleniaceae), an abundant tree species with a wide geographic distribution. The following hypotheses were tested: (1) density, vital rates and population growth rate are constrained by low rainfall and low soil fertility and (2) ramet production contributes more than seedling production to population growth at low rainfall levels and low soil fertility. Population dynamics were evaluated at two soil types (low and high fertility) over 3 years (2010, 2011 and 2012) with varying rainfall levels (average, average and low rainfall levels, respectively). Both hypotheses were supported. Vegetative growth and the population growth rate were limited by low rainfall and low soil fertility. The survival rates of adults and immature ramets had the largest effect on population growth. Although sprouting was limited by resource availability, this regeneration mode contributed more than seedlings to population growth. Basal sprouting not only ensures species persistence but also, as indicated by these results, permits a species to tolerate a lack of seedling recruitment. Basal sprouting was, therefore, determined to play an important role in the population growth of woody species in heterogeneous environments. [ABSTRACT FROM AUTHOR]