Desert vegetation needs to cope with extreme conditions such as water shortage and high temperatures. Therefore, species performance and community composition are shaped by habitat conditions, allowing only highly adapted species to co-occur. Because the vegetation is the food source for primary consumers in this highly stressful system, it is reasonable to assume that vegetation is strongly limited by both resource supply and herbivore activity. Alternatively, there are large similarities between plant adaptations to arid conditions and to the presence of large herbivores. This may imply that desert vegetation is tolerant to the presence of herbivores. The effect of the Asiatic wild ass (Equus hemionus) on vegetation composition in the Negev highlands is an appropriate model system to study these effects. This large herbivore was reintroduced to the region few decades ago, and has successfully recolonized it. Nevertheless, the population depends on artificial water supply, as most of the natural water sources are captured for human use. The dependency on water creates a gradient of herbivore intensity within the region, thus allows for a comparison between sites which are environmentally similar, except for the potential impact of herbivory. To study these effects, we sampled the local seed bank within the region. Seed bank composition is particularly suitable for this comparison because it reflects the local species pool. Therefore, by comparing species composition in relation to wild ass activity and site conditions, we were able to gain an insight into the long-term interplay of these factors on the region vegetation.
