Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Plant dispersal through a stream network in a hyper-arid environment

Auteur : Arnon, Ofer

Université de soutenance : Ben-Gurion University of the Negev

Grade : Master of Science (2012)

Résumé
This research measures the dispersal of ecological information from a source through a vector. In this research the ecological information is invasive and generalist plant species, the potential source are homesteads in Ramat HaNegev regional council, and the vector is the stream network. Ramat HaNegev region is a hyper-arid area, which is part of the Sahara– Arabian desert belt (Avni et al., 2006). Dispersal through water (hydrochasty) is one of the most common strategies for plant species in this region (Metz et al., 2010). Generalist plant species are defined as native plants with low specialization to a specific habitat (Coltrane and Barboza 2010). Invasive plant species are defined as alien plants, which are introduced to a new range of habitats, where their descendants proliferate, spread and persist. These species have the dispersal potential through the stream networks, and to cause a substantial impact on the ecosystem (Chun et al., 2010). Homesteads are a unique and new type of settlements in the Ramat HaNegev region (Tal 2007). No scientific research has been conducted so far about the homesteads’ ecological impact. An 8D model is used in order to calculate the stream network in the region, the homesteads’ area, and the plant dispersal. 8D model is a digital spatial model, which calculates topographic variables of nine cells, where the eight neighboring cells have an effect on the central one (Longley et al., 1999). The statistical analysis is applied by ordination test, using Canoco program (version 4.5). This research was designed to find whether homesteads serve as a source of generalist and invasive plant dispersal ; what the plant dispersal distance is ; what is the maximal plant dispersal distance is and ; whether there is a difference in the plant dispersal from touristic and agricultural homesteads. The research was conducted during two consecutive years, in order to measure the abundance of invasive and generalist plants inside and outside homesteads. Plant survey was conducted in five homesteads in 2010 and two homesteads in 2011. The plant survey’s results show that while the homesteads do not serve as a source for invasive plants in the region, some may serve as a source for several generalist plants. Further, the generalist plant dispersal distance was < 1000 m from the homesteads. No significant difference was found in the dispersal of generalist and invasive plants from agricultural and touristic homesteads. Therefore, this research cannot offer conclusive answers about the performance of homestead in this region as a source for invasive and generalist plant dispersal. In addition to the plant data generated, this research also introduces a method to measure dispersal of any ecological information from any source through any vector. This method can be used for future research regarding ecological dispersal anywhere around the world. The research can also help decision makers in this region to reach the most sustainable plan possible regarding homesteads’ development. More research is required in order to better characterize the full ecological impact caused by homestead settlements in Ramat HaNegev. The impact might be specific, by dispersal of invasive and generalist plant species, or general, by other anthropogenic (human related) factors.

Mots Clés : Family farms — Israel — Negev — Environmental aspects Invasive plants — Ecology — Plant spores — Dispersal — Plants — Stream ecology

Présentation (BGU)

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