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Climate Change in Arid Lands: Effects on Soil Biota and Ecosystem Processes

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.

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Climate Change in Arid Lands: Effects on Soil Biota and Ecosystem Processes

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  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 +2.9oC, 5cm +2.7oC, 15cm +2.5oC % of 24 hr period with additional warming of >0oC and <5oC: 78, 81, 93% % of nighttime hrs with additional warming of >0oC and <5oC: 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 thespecies 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 • CO2 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. 6000 10 Amoebae Nematodes 8 4000 6 4 2000 2 Individuals per gram dry soil 400 3000 Flagellates Ciliates 300 2000 200 1000 100 0 0 Heat Heat Control [Water] Control [Water] Lamp Control Lamp Control Heat [+ Water] Heat [+ Water] 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. 2006 Drydown Experiment - Fauna 10 4000 a Amoebae Nematodes a 8 3000 ab 6 ab ab 2000 b 4 b bc 1000 bc 2 c Individuals per g soil 0 0 Cont 120 30 20 10 Cont 120 30 20 10 2000 200 Flagellates Ciliates a a 1000 100 b b b b b ab b b 0 0 Cont 120 30 20 10 Cont 120 30 20 10 Treatment Treatment 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.

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