PARENT SESSION
Oral Session #105: Conservation Ecology: Biodiversity.
Presiding: L. Alonso
Friday, August 9. 9:00 AM to 12:00 PM. Grand Ballroom Central, Radisson.
Effects of shrub mounds on species richness: the role of spatial scale and environmental variability.
Wright, Justin*,1,2, Jones, Clive2, Boeken, Bert3, Shachak, Moshe2,3, 1 Dept of Ecology and Evolutionary Biology, Ithaca, NY2 Institute of Ecosystem Studies, Millbrook, NY3 Jacob Blaustein Institute for Desert Research, Sede Boker, Israel
ABSTRACT- It is generally accepted that landscapes with a higher diversity of habitats support a higher diversity of species. However, the importance of ecosystem engineers, species that create, modify, or maintain habitats, in maintaining species richness is poorly understood. The effects of engineers on species richness may depend on both the temporal and spatial scale of observation. In the Negev Desert, Israel, shrubs create mounds of nutrient-rich, loose soils in contrast to the crusted, hydrophobic soils that occur between shrubs. These mounds are sites of high water infiltration and storage, and, as a result, individual shrub mounds have been shown to have higher annual plant diversity than equivalent areas of the crusted soil that occurs between shrubs. To examine the effects of shrub mound on species richness at larger scales, we sampled the annual plant community beneath 150 individual shrubs and adjacent patches of crusted soil. Using species accumulation curves, we determined that shrub patches contained more species than crust patches even at large spatial scales. Crust patches supported only a subset of the plant species found on shrub patches, suggesting that if all shrubs were removed from the system, species richness of the landscape would decrease, even if the area of crust increased. By comparing shrub and crust species richness across several years, we determined that the effect of shrub mounds on total species richness of the system was highly dependent on annual precipitation. Shrub mounds had the largest effect in years of intermediate precipitation (approx. 200 mm). Ecosystem engineering by shrubs is an important control on species richness in the Negev, both at the patch scale and at the landscape scale. However, the magnitude of the engineering effect varies, depending on precipitation.
KEY WORDS: ecosystem engineer, Negev Desert