Dryland afforestation frequently provides ecological and economic benefits. Nevertheless, afforestation species were and still are selected mainly for their ability to withstand aridity, while other important characteristics are not adequately considered. This approach has led to some socio-ecological crises where afforestations are drought resistant, but yet harm the natural ecosystem and do not provide adequate ecosystem services to human communities. We propose an integrative silvicultural-socio-ecological conceptual framework that would select multifunctional tree species to satisfy three main criteria: (a) be drought resistant; (b) minimally disrupt ecosystem integrity; and (c) maximize the provision of ecosystem services emphasizing the support of community livelihoods. We further propose to conduct an experimental evaluation of the candidate species, according to these criteria. We present the conceptual broad framework and preliminary results of experiments with a few Ziziphus species. The experiments are testing part of the criteria suggested for the socio-ecological species selection for dryland afforestation.
The preliminary results are of a set of experiments that are part of a priory testing of defined criteria for the selection of woody species for dryland afforestation with a minimum risk to the natural ecosystem. We investigated the spontaneous establishment from seeds in dryland conditions to evaluate the potential of planted Ziziphus species to spread invasively from afforestations. This trait is part of the proposed criteria for species selection. We hypothesize that germination is determined by: 1- The interplay between seed viability and seed-coat weathering. 2– The coincidence of high temperatures and water availability. We argue that both conditions should be met for successful germination and that they are rare in arid environments. Thus the probabilities of the species to become invasive are low. We test our hypothesis conducting a series of seed burial and growth chamber experiments. Preliminary results show higher germination rate under the combination of constant soil moisture and high temperatures. Germination under controlled conditions support these results, demonstrating that germination favors 30OC over 20OC and 5OC. Seeds are viable even after 1.5 years from ripening, and germination may occur in favorable conditions.We discuss preliminary results in the light of our suggestion for a conceptual integrative framework for dryland afforestation.