1. Climate Change in Arid Lands: Effects on Soil Biota and Ecosystem Processes Deborah A. Neher University of Vermont Jayne Belnap USGS - Southwest Biological Research Center Cheryl Kuske Los Alamos National Laboratory Thank you to B. Darby, D. Housman, S. Johnson and DOE PER

2. Average increased soil warming: surface +2.9 o C, 5cm +2.7 o C, 15cm +2.5 o C % of 24 hr period with additional warming of >0 o C and <5 o C: 78, 81, 93% % of nighttime hrs with additional warming of >0 o C and <5 o C: 92, 82, 93%

3. Hypotheses Biological soil crusts (BSC’s): H1: Increased temperature and summer precipitation will alter species composition, abundance, activity times and physiological functioning of BSC’s. This will reduce C and N inputs into soils. Increasing both temperature and precipitation will have a greater effect than either factor alone. Subsurface soil biota: H2: Increased temperature and summer precipitation will alter the species composition, abundance, activity times, and physiological functioning of subsurface soil biota due to their dependence on C and N inputs from BSC’s, as well as direct effects of altered temperature and precipitation on their physiological functioning. Increasing both temperature and precipitation will have a greater effect than either factor alone. Soil processes & vascular plants: H3: Alterations in the species composition, abundance, activity times, and physiological functioning of soil biota will affect soil processes and vascular plant performance.

4. Field Measurements Air & soil temp, humidity, precipitation, wind, & net radiation Soil water at three depths CO 2 flux in warmed and control plots Crust cover, composition & pigments Photosynthesis & Fv/Fm Nitrogen (total, fixation, mineralization, isotopes) Soil bacteria biomass & metabolism Photosynthetic and N cycling bacterial abundance/composition Soil fauna composition & abundance Soil chemistry (nutrients, texture, OM, decomposition) Soil enzymes

5. Baseline: No significant difference in photosynthesis, Fv/Fm, N fixation, bacterial biomass, or faunal abundance Early Warming Results: Winter C loss greater in warmed vs. control plots Abundance of late-winter soil fauna similar across treatments except for amoebae

6. Drydown Experiment Single drying events of 10, 20, 30(typical), and 120 min. Soil faunal abundance similar across drying treatments, but < controls. N - fixing ability (nifH mRNA) declined slowly in dried soils. Total RNA content and ammonia-oxidizing ability similar across treatments. Soil crust Fv/Fm and pigments similar across treatments.

7. Experimental field study of the interactive effects of extremes (temperature and precipitation) on ecosystem function and diversity (including genetic diversity) in drylands.