Afforestation is the formation of a novel forest in an environment where forests do not occur naturally. In drylands, afforestation is usually aimed at land reclamation along with increasing human wellbeing by the enhancement of ecosystem services e.g. the prevention of soil erosion or the formation of a cooler environment. The establishment of a sustainable novel forest ecosystem in drought prone environments requires the selection of species with a set of traits that allow persistence under the harsh conditions. Moreover, in traditional silviculture forest sustainability requires the spontaneous regeneration of forest trees.
We hypothesize that tree traits which enable tree establishment and persistence in dryland afforestations, may overlap with the traits that are considered to promote the species invasiveness. In this study we investigate:1- this hypothesis and 2-the extent of the overlap between traits that may contribute to species invasiveness and the traits that contribute to a successful afforestation establishment.
In a cross table approach we define traits that may promote invasiveness according to the life-history, phenotypic plasticity and propagule pressure hypotheses. On a second layer we define traits that promote successful establishment and sustainability. We review common dryland afforestation species and rank their correspondence with the selected traits.
Results/Conclusions
Preliminary results from the cross table demonstrate that the combination of the traits is crucial in determining the equipoise between sustainability and invasiveness risk. For example, re-sprouting is a highly distributed trait among species used for dryland afforestation. It is a trait that promotes invasiveness as well, but only if combined with spontaneous germination. In some species, even if the seed production is high and enables high propagule pressure -the high-stress environment inhibits spontaneous germination and reduces the risk of invasiveness. A summary of the results is represented by a tree life cycle scheme - signifies the factors that affect each transition from one developmental stage to the other and points on the transitions that are crucial for a species to be well established or to potentially become invasive. Understanding the equipoise between sustainability and invasiveness risk empower our decisions on species selection for dryland afforestation.