We generated a snapshot of the microbial communities in the Negev Desert, giving us an insight in its natural state. This desert, like many arid environments, is vulnerable to exploitation for other purposes, including solar energy production and dry land farming.

Astragalus (Fabaceae), the largest genus of plants in the world with an estimated 3270 species, is known for large numbers of rare endemic species. An inventory of patterns of climatic, topographic, and edaphic diversity of Astragalus taxa in California (98 native species and 144 named taxa) provides a means to understand the occurrence of rarity in relation to climatic equitability and regional species richness of congeneric taxa. Most taxa in the genus have relatively small ranges of distribution, with 50% restricted geographically to a single Jepson Bioregion. The California Native Plant Society lists 51 Astragalus taxa (35% of the native Astragalus taxa) as rare, threatened, or endangered (RTE). Climate characteristics of geographic regions such as rainfall and temperature extremes show no obvious relationship to species richness or the proportion of listed taxa. Species richness is highest in the arid Great Basin (35 species and 53 taxa) combining both its components, followed by 29 species and 39 taxa in the Sierra Nevada East region that includes the White and Inyo Mountains. The Mojave Desert is also high in diversity with 32 species and 39 taxa, but in contrast the Sonoran Desert region is low with only 12 species and 14 taxa. Despite ranking highest in the number of Astragalus taxa present, the Great Basin regions are low in their proportion of RTE taxa (17%) compared to the South Coast Region (39.5%) and Mojave Desert (32%). Strong edaphic specialization is associated with the majority but not all RTE taxa. While no single ecophysiological adaptation can explain this pattern, it is significant that Astragalus taxa have the potential ability to develop symbiotic nitrogen fixation, and this trait is key to success in soils not conducive to growth of many potential competitors. Land use changes, alien grass invasion and grazing, among other threats, are increasing fragmentation of habitats for many rare taxa with consequent impacts on gene flow. The continued survival of rare and locally endemic taxa will require improved knowledge of their individual demographic traits and long-term population dynamics.

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Astragalus jaegerianus Munz (the Lane Mountain milkvetch) is a federally endangered species that exists in only four fragmented populations within and adjacent to the U.S. Army's National Training Center, Fort Irwin, CA. Since 1999, our monitored A. jaegerianus populations have consistently declined, and are now 12% of their previous size. A number of subpopulations are in danger of local extinction. The decline of A. jaegerianus has occurred simultaneously with severe drought in the Mojave Desert. These drought conditions began in 1999 and are predicted to continue for decades, or may continue indefinitely under warmer temperature conditions projected by global climate changetype drought. Our results suggest that drought has direct and indirect affects on A. jaegerianus by killing or degrading its host shrubs. Astragalus jaegerianus host shrubs have decreased in shrub volume and cover by roughly 10 percent since the onset of drought, and shrub mortality has been high. Our results show that canopy condition has a profound affect on the microclimate within host shrubs. Furthermore, our results show a significant increase in survival of A. jaegerianus among host plants with more intact canopies. These results support our study hypothesis that drought-related changes to host plant canopies affect A. jaegerianus survival, and represent an indirect negative effect of long-term drought on A. jaegerianus populations.