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Metal Controls and Acidity Controls on Forest Floor and B-Horizon Extractable Phosphorus in Forested Watersheds Michael D. SanClements1, Ivan J. Fernandez2, Stephen A. Norton3 1Dept. of Plant, Soil, and Environmental Sciences 2Dept. of Plant, Soil, and Environmental Sciences & Climate Change Institute 3Dept. of Earth Sciences & Climate Change Institute Research Objectives • Apply P fractionation techniques to an analysis of soil P, Al, and Fe across a suite of acidic soils in forested watersheds to determine: – chemical distributions of P among fractions – metal controls on P availability • Better understand influence of changing chemical climate (e.g. acidic deposition) ALPSS Project Sites (Aluminum and Phosphorus in Soils and Solutions) 3 1 6 2 4 1. 2. 3. 4. Bear Brook Watershed in Maine Hadlock Brook Watershed Mud Pond Watershed Fernow Experimental Forest 5 5. Strengbach Watershed Maine Maine 6. Lesni Potok Maine West Virginia France Czech Republic Conceptual Sampling Design Stream Channel Eight additional sampling points equidistant from each other 20m x 13 Pedons per transect 26 Pedons per watershed 10m x 3m x 1m x 0.1m x Watershed Characteristics • Upper B-horizon pH CaCl2: 3.4 to 4.1 • Upper B-horizon % C: 1.1 to 8.9 • Dominant Vegetation: Red spruce, Norway spruce, American beech, European beech • Soil Orders: Spodosols Inceptisols Phosphorus Fractionation Modified From Psenner (1985,1988) – 1M NH4Cl Labile-P – NaHCO3-Na2S2O4 Reducible Fe-P – 0.1M NaOH Al-P, Fe-P PT Murphy-Riley PT – PI =PO – 0.5M HCl Ca-P – 1M NaOH Residual-P PI Total Soil P by Watershed 900 d Σ Psenner-P (mg kg-1) 800 700 acd 600 500 a 400 ca 300 eab b 200 100 0 EB HB MP F4 LP SB Distribution of P by Fraction Residual-P 14% Labile P 1% Fe-P 4% Ca-P 9% Al-P 72% pH, Al, and P 40 100 1400 80 0 0 30 1200 PNaOH-25 1000 60 HB800 MP F3 600 F4 SB 400 LP EB200 WB 20 40 10 20 3.0 0 3.03.2 3.4 3.6 3.5 3.8 4.0 4.0 4.2 pH CaCl pH CaCl 2 2 4.44.5 4.6 4.8 5.0 AlNaOH-25 mmoles kg-1 PNaOH-25 mmoles kg-1 Al(NaOH-25):P(NaOH-25) AlNaOH-25 Linkages to Biology? B-horizon Controls on Forest Floor P Mean O-horizon P(NH4Cl) mg kg -1 200 SB MP F3 F4 EB WB 180 160 140 120 100 80 60 40 20 0 10 20 30 40 Mean Al(NaOH-25):P(NaOH-25) 50 60 Conclusions 1. The results suggest that Al controls P accumulation, and that Al dynamics are an important control on the biological availability of P 2. Any process or perturbation affecting Al within the ecosystem could directly alter P dynamics Acknowledgements With special thanks to: •Mary Beth Adams, U.S.D.A Forest Service •Tom Navratil, Czech Geologic Society •Marie-Claire Pierret, University of Strasbourg •Cheryl Spencer, University of Maine •David Manski, National Parks Service This research supported by: National Science Foundation Maine Agricultural and Forest Experiment Station