Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Slide 53Slide 54Slide 55Slide 56Slide 57Slide 58Slide 59Slide 60Slide 61Slide 62Slide 63Slide 64Slide 65Slide 66what do plants respire for?Slide 68Slide 69Slide 70Slide 71Slide 72Slide 73Slide 74Slide 75Slide 76Slide 77Human ActivityDirect: ClORPTHThe “Jenny State Factor Model”: Soil/Ecosystem = f(Cl, O, R, P, T,…)The fundamental independent variables driving ecosystem developmentHuman ActivityIndirect: Climate ChangeSpecies introductionsPossum in New ZealandClORPTHNitrogen depositionHuman ActivityIndirect: ClORPTHClORPTH & Disturbance:Any physical force, such as fire, wind, flood, extremely cold temperature, and epidemic, that damages natural systems and results in the mortality of organisms or loss of biomass. Smith. 1996: Ecology & Field BiologyRelatively discrete event in time and space that alters the structure of populations, communities, and ecosystems and causes changes in resource availability or the physical environment.Chapin et al. pg. 379Climate variability:extremes come from disturbance1999: Boundary Waters Canoe Area2008 Santa Barbara 2005: Santa Barbara2007: ManitobaThese are common and critical in structuring ecosystemsClORPTHfrequency distribution of disturbance in Northern forestsFrelich and Lorimer 1991. Ecological Monographs 61: 145-164Small disturbances are commonLarge disturbances are rareClORPTHDisturbance & time:Disturbance and spaceConsider fire in:a 1,000 Km2 of foresta10 m2 patch of forestsource:http://3.bp.blogspot.com/_CjwpWolRwVI/Sj61QPUCNBI/AAAAAAAABL4/NgD6Z4dBoQw/s400/P6217595.JPG; http://www.dendronautics.com/USERIMAGES/canopy-img0086.jpgClORPTHsource:http://upload.wikimedia.org/wikipedia/commons/7/7f/20070801_forest.jpgDisturbance & climate: Arctic drunken forestsClORPTHwhat is soil?SoilA soila complex material with natural structure the basis of all terrestrial processessoil processes control plant growth and ecology:Water Nutrientsnet primary productivity (NPP)resource allocationDespite this, many ecologists see soil as “external” to the system1. Ecologists have traditionally started as botanists/biologists2. Soil development is slow (100’s – 1000’s of years)WHY?key characteristics of soil• Texture: sand, silt, clay• Organic matter content• Chemical composition (mineralogy, pH, etc.)• Physical structuresoil developmentVermont New York Delaware GeorgiaCalifornia Wisconsin Iowa Puerto Ricogeneric soil profileRegulating water. Controls where rain, snowmelt, and irrigation water (& dissolved solutes) goes. Sustaining plant and animal life. The diversity and productivity of living things depends on soil.Filtering potential pollutants. Soil minerals & microbes filter, buffer, degrade, immobilize, & detoxify organic & inorganic materials (e.g. industrial byproducts & atmospheric pollution).Cycling nutrients. Carbon, nitrogen, phosphorus, and many other nutrients are stored, transformed, and cycled through soil.Supporting structures. Societies depend upon stable soils for buildings, development & agriculture.Why care about soil?Key things to know about soil:Texture: How much clay/sand/silt?Mineralogy: What type of clay?Structure: How is the soil put together?soil texturesand: 2 mm – 50 µmsilt: 50 µm – 2 µmclay < 2µmsource: http://school.discovery.com/schooladventures/soil/teacher_tips.htmlsoil texturesand: 2 mm – 50 µmsilt: 50 µm – 2 µmclay < 2µmsoil structure: how individual soil granules clump or bind together and aggregate  therefore, the arrangement of soil pores between them. Has a major influence on water & air movement, biological activity, root growth & seedling emergence.source: http://ohiodnr.com/H_Nav2/Soils/OhiosSoils/IntroductiontoSoils/tabid/17818/Default.aspxBlockyPlatyGranularColumnarsoil structureelectron micrograph of grassland soilsoils are complex!CLAY STRUCTUREtetrahedral octahedralA 1:1 clay: one tetrahedral sheet and one octahedral sheet1:1 clay minerals2:1 clay mineralsO– opposite each other:REPELA 2:1 clay: an octahedral sheet sandwiched between two tetrahedral sheets (2:1 ratio silica: Al3+, Mg2+, Fe3+)2:1 clay minerals: allow H2O/ionssurface areaclays have a large surface area:1:1’s: 10-20 m2/g2:1’s: ~800 m2/gchemically active: organic matter, ions, and microbes stick to claysbacterium++++Clay—negatively chargedSOLUTIONCation (NH4+, Mg+2, K+, etc,) Exchange Capacity: CECclay minerals: major CEC source in most soils  ions concentrate at clay surfaces2:1 minerals have more CEC than 1:1 minerals1:1’s: 20–80 µM of electric charge/g2:1’s: 1,000–2,000 µM/gSOM  also high CECWater Holding Capacity (WHC)Fine pores and surfaces hold water Clays promote structure with lots of small pores 2:1’s hold water in interlayerssoil organic matter (SOM)What is SOM?Complex mix of stuff—• dead plant material• microbial products• humified materialfunctions:• soil structure—OM acts as glue• H2O movement and retention• high cation exchange capacity (CEC)• nutrient supplySoil Organic MatterThe bulk of carbon in the terrestrial worldThis stufIt is no longer plant litter: it has been processed and reprocessedsoil organic matter (SOM)Soil Organic Matter: Why is it important?Global pools of C:Atmosphere 750 Tg (1015 g)Plants 560 TgSoils 1500 Tg (underestimate!)Tropical Rainforest:Plants 400 t/haSOM 300 t/haBoreal ForestPlants 120 t/haSOM 310 t/hasources of SOM Inputs into soil Transformation of plant detritus into SOM Inputs: Leaf/aboveground litter: 20-60% Root death: 30-60% Root exudates: 5-10%Soil organic matter is complex:Plant detritusMicrobial biomass and productsHumic materialsFulvic acidHumic acidHuminwell-decomposed organic matter &highly stable organicmaterialHow do we characterize SOM?Historical:Fulvic Extracted with 0.1 M NaOH Humic Extracted with 0.1 M HClHumin InsolubleHow do we characterize SOM?How do you go from plant inputs to SOM?Some goes straight into microbial biomass and then into various microbial product poolsLigninPolymerPhenolicMonomerMicrobialBiomassHumicsNew PolymerConceptual