Presentation on theme: "Decomposers, Aquatic and Nutrient Cycles"— Presentation transcript:
1Decomposers, Aquatic and Nutrient Cycles HeatFirst TrophicLevelSecond TrophicThird TrophicFourth TrophicSolarenergyProducers(plants)Primaryconsumers(herbivores)Tertiary(top carnivores)Secondary(carnivores)Detritvores(decomposers and detritus feeders)
2Three Major Types of Nutrient Cycles Hydrologic (or water) Cycle – water in the form of ice, liquid water and water vapor cycles through the biosphere.Atmospheric Cycle – a large portion of a given element exists in a gaseous form in the atmosphere.Sedimentary Cycle – An element does not have a gaseous phase, or its gaseous compounds do not make up a significant portion of its supply.
3Hydrologic CycleCollects, purifies, and distributes the Earth’s fixed supply of water – powered by the sun.Distribution of Earth’s Water Supply:Salt water (oceans) = 97.4%Freshwater = 2.6%80% in glaciers and ice caps20% in groundwater0.4% in lakes and rivers (0.01% of all water!)Anytime of year, the atmosphere holds only % of water on the planet.Although large quantities are evaporated and precipitated each yearAbout 84% of water vapor comes from the ocean
4Main Processes of the Hydrologic Cycle Evaporation – conversion of water into water vaporTranspiration – evaporation from leaves of water extracted from soil by rootsCondensation – conversion of water vapor into droplets of liquid waterPrecipitation – rain, sleet, hail, and snowInfiltration – movement of water into soilPercolation – downward flow of water through soil and permeable rock formations to groundwater storage areas called aquifersRunoff – downslope surface movement back to the sea to resume cycle
10Seasonal shift in rainy/dry seasons Rainy SeasonSeasonal shift in rainy/dry seasons
11Matter Cycling in Ecosystems Nutrient – any atom, ion, or molecule an organism needs to live, grow, or reproduceSome (such as C, O, H, N, P, S, and Ca) are needed in fairly large amountsSome (such as Na, Zn, Cu, and I) are only needed in trace amounts.
12Nutrient Cycles Compartment – represents a defined space in nature Pool – amount of nutrients in a compartmentFlux rate – the quantity of nutrient passing from one pool to another per unit time.
14Hypothetical Phosphorus Nutrient Cycle PlantsHerbivoresWater126811.49133745191009.5Flux rate and pool size together define the nutrient cycle within any particular ecosystem
15Nitrogen CycleNitrogen is used to make essential organic compounds such as proteins (amino acids), DNA, and RNA.Nitrogen is the atmosphere’s most abundant element (global gaseous cycle).78% of the volume is chemically un-reactive nitrogen gas N2.Takes a lot of energy to break the triple covalent bonds holding N NMicrobes mostly responsible for N cycle
16Have You Hugged Your Microbes Today Have You Hugged Your Microbes Today? Besides making beer, they are responsible for:Nitrogen fixation –conversion of gaseous nitrogen (by Rhizobium, Azotobacter, and cyanobacteria) to ammonia (N2 + 3H2 2NH3) which can be used by plants.Nitrification - Two-step process in which ammonia is converted first to NO2- (by Nitrosomonas) and then to NO3- (by Nitrobacter).Denitrification – conversion of nitrate ions (by Pseudomonas or other anaerobic bacteria in waterlogged soil or in the bottom sediments of a water body) into nitrogen gas (N2) and nitrous oxide gas (N2O)Ammonification – the conversion (by decomposer heterotrophic bacteria) of nitrogen-rich organic compounds, wastes, cast-off particles, and dead bodies into available ammonia (which can be used by plants).
20Phosphorous CycleThe phopsphorous cycle is slow, and on a human time scale most phosphorous flows from the land to the sea.Circulates through the earth’s crust, water, and living organisms as phosphate (PO4)Bacteria are less important here than in the nitrogen cycleGuano (bird poop), mined sediments, and ‘uphill’ movement of wastewater are the main ways phosphorous is cycled in our lifetimeGeologic process (mountain formations / uplifting of ocean sediments) cycle phosphorus in geologic time
21Phosphorous Cycle Guano Food web River Flow Soil Ocean Water Geologic UpliftingFood webMiningSediments
22Phosphorous is Important Most soils contain very little phosphorous; therefore, it is often the limiting factor for plant growth on land unless added as fertilizer.Phosphorous also limits primary producer growth in freshwater aquatic ecosystems.
24Sulfur Cycle The sulfur cycle is a gaseous cycle. Sulfate (SO4) is the principal biological formEssential for some amino acidsUsually not limiting, but the formation of iron sulfides converts the insoluble form of phosphorous to a soluble formSulfur enters the atmosphere from several natural sources.Hydrogen sulfide (H2S) is released by volcanic activity and by the breakdown of organic matter in swamps, bogs, and tidal flats (you can smell this at low tide in the salt marsh).Sulfur dioxide (SO42-) enters from volcanoes.Particles of sulfate (SO42-) salts, such as ammonium sulfate, enter as seas spray.
27Carbon CycleCarbon is the basic building block of organic compounds necessary for life.The carbon cycle is a global gaseous cycleCarbon dioxide makes up 0.036% of the troposphere and is also dissolved in waterKey component of nature’s thermostatToo much taken out of the atmosphere, temp’s decreaseToo much added to atmosphere, temp’s increase
28Available to Consumers Primary ProductivityCO2C6H12O6PhotosynthesisRespirationSolar EnergyHeat EnergyBiomass (g/m2/yr)O2Available to ConsumersChemical Energy (ATP)GPPNPP
29Atmospheric / Aquatic CO2 Combustion of wood / fossil fuels Food WebPhotosynthesisRespirationCombustion of wood / fossil fuelsLimestone RocksCarbon CycleSedimentationWeatheringVolcanic Action
30The RecyclersDetritus – parts of dead organisms and cast-off fragments and wastes of living organismsDetritivores – organisms that feed on detritus (detritus feeders and decomposers).Detritus feeders – extract nutrients from partially decomposed organic matter in leaf litter, plant detritus, and animal dung (crabs, carpenter ants, termites, earthworms).Decomposers (certain types of bacteria and fungi) are very important in recycling nutrients in an ecosystem
31Detritus Feeders and Decomposers Without detritus feeders and decomposers, the lack of nutrients would quickly stop primary production!
32Turnover and Residence Times Turnover rate – the fraction of the total amount of a nutrient in a compartment that is released (or that enters) in a given periodTurnover time – the time needed to replace a quantity of a substance equal to its amount in the compartmentResidence time – the time a nutrient stays in a compartment (similar to turnover time)
33Nutrient Cycles in Forests Inputs – outputs = storageNutrients accumulate in the leaves and wood over time
34Nutrient Storage in Trees is Temperature and Vegetation Type Related Organic matter (kg/ha)Nitrogen (kg/ha)Forest Region#TreesTotal% Above GroundBoreal coniferous351,000226,000191163,2504Boreal deciduous197,000491,000203313,7806Temperate coniferous13307,000618,000544797,3007Temperate deciduous14152,000389,000404425,6198Mediterranean269,000326,000837451,02573Average208,000468,000454295,893In cold climates nutrients are tied up in the soil.
35Nutrient Turnover Time is Temperature Related Mean turnover time (yr)Forest Region#Organic matterNKCaMgPBoreal coniferous3353230.094.0149.0455.0324.0Boreal deciduous12627.110.013.814.215.2Temperate coniferous1317220.127.116.112.915.3Temperate deciduous1445.51.33.03.45.8Mediterranean18.104.22.168.9All Stands321234.113.021.861.446.0Turnover time – the time an average atom will remain in the soil before it is recycled into the trees or shrubs
36Net Primary Production and Nutrient Cycling In general, NPP is closely related to the speed of nutrient cycling.Tracking the decay of a leaf and the cycling rate of nutrients provides an indicator of biome productivity.Mean Residence Time (In Years)*BiomeOrganic matterNitrogenPhosphorousPotassiumCalciumMagnesiumNPP(g C/m2/yr)Boreal forest35323032494149455360Temperate forest22.214.171.124.03.4540Chaparral126.96.36.199.45.02.8270Tropical rain forest0.42.01.60.71.51.1900* Mean residence time is the time for one cycle of decomposition.
37Rapid Cycling in the Tropics Reasons for rapid cycling in the tropics:Warm climateNo winter to retard decompositionAn army of decomposersAbundant mycorrhizal fungi on shallow rootsFungi that grow symbiotically with plant rootsFacilitate water and nutrient uptake
38The Tropics: A Closed System The speed of nutrient cycling in the humid tropics promotes high productivity, even when soils are poor in nutrients.Nutrients are cycled so quickly there is little opportunity for them to leak from the systemWaters in local streams and rivers can have as few nutrients as rain waterBecause there is virtually no loss of nutrients, many tropical forests have virtually closed nutrient cycles.The opposite would be an open system, in which nutrients are washed out rapidly
39Tropical Rain Forest Paradox Most tropical rain forests are poor in nutrients – especially oxisol.When the forests are cleared for farmland, the land can only support three or four harvests.Well, how can they support the amount of primary production we find in a tropical rain forest?
40Standing BiomassStanding Biomass - all the plant matter in a given area.Nutrients are either found in the soil or in the standing biomass.In a temperate forest system, recycling is slow.Consequently, at any given time, a large proportion of nutrients are in the soil.So when the land is cleared, it is fertile and can support many years of agriculture
41Tropical SoilsIn the humid tropics, as little as 10% of the total nutrients are in an oxisol (soil) at any given time.Hence, when the logging trucks take the trees, they are carrying the majority of the nutrients!An increase in soil acidity often follows timber removal to the point that available phosphorous is transformed to an insoluble form.
42Watershed Biogeochemistry Watershed – catchment or drainage basin of a riverStreams and rivers are main conduits of nutrient lossVegetation type can influence nutrient loss:Mean calcium concentrations (% dry wt) in three plant species.SpeciesBarkWoodTwigsLeavesChestnut Oak1.25 ± 0.170.09 ± 0.010.68 ± 0.060.58 ± 0.07Flowering Dogwood2.36 ± 0.260.11 ± 0.010.80 ± 0.061.85 ± 0.11Rhododendron0.30 ± 0.100.07 ± 0.310.99 ± 0.241.20 ± 0.29
43Normal Nutrient LossRain runoff is the major vector of nutrient loss from most ecosystemsPrecipitation (mg/L)Streamwater (mg/L)Calcium0.211.58Magnesium0.060.39Potassium0.090.23Sodium0.120.92Aluminum---a0.24Ammonium0.220.05Sulfate3.106.40Nitrate1.311.14Chloride0.420.64Bicarbonate--- a1.90Dissolved silica4.61ba Not determined, but very low; b Watershed 4 only
44Deforestation Can Increase Loss of Nutrients From Areas Due to Runoff Note Scale ChangeStream Nitrite ConcentrationOther stream nutrient increase two years after the deforestation:Calcium 417%, Magnesium 408%, Potassium 1,558%, Sodium 177%
45Riparian Buffer ZoneAreas of trees, shrubs and other vegetation, that are adjacent to a body of water, that are managed for several purposes:to maintain the integrity of stream channels and shorelines;to reduce the impact of upland sources of pollution by trapping, filtering, and converting sediments, nutrients and other chemicals;to supply food, cover and thermal protection to fish and other wildlife.The main purpose of a riparian buffer is to help control non-point source pollution.
47Other Methods to Control Erosion Silt Fence / hay balesAllows water to pool so that sediment is dropped.
48What is Soil?Complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and billions of living organisms (mostly decomposers)Soil is created byWeathering of rockDeposit of sediments by erosionDecomposition of organic matter in dead animals
49Soil Horizons (Profiles) O horizon - Consists mostly of freshly fallen and partially decomposed leaves, twigs, animal wastes, fungi, and other organic materials.A horizon - A porous mixture of partially decomposed organic matter (humus) and some inorganic mineral particles.Humus is a sticky, brown residue of partially decomposed organic material.B Horizon (sub-soil) and C horizon (parent material) - Contain most of a soil’s inorganic matter. Mostly broken-down rock consisting of varying mixtures of sand, silt, clay, and gravel.
50Soil Horizons (Profiles) O horizonLeaf litterA horizonTopsoilB horizonSubsoilC horizonParentmaterialMature soilYoung soilRegolithBedrockImmature soil
51Life in SoilThe two top layers of most well-developed soils teem with bacteria, fungi, earthworms, and small insects that interact in complex food webs and nutrient cycles.
52Soil Texture Clay – very fine particles Silt – fine particles Sand – medium-size particlesGravel – Coarse to very coarse particlesLoam – roughly equal mixtures of clay, sand, silt, and humus
54Topsoil – Renewable Resource? Is regenerated by renewable resources, but it takes ,000 years to produce about an inch of topsoil in tropical and temperate climatesRate depends on climate and soil typeIf erosion exceeds regeneration, then the resource is not renewable
55Soil erosion – movement of soil components, especially surface litter and top soil, from one place to another.- Typically caused by flowing water and windAny activity that destroys plant cover makes soil vulnerable to erosion (e.g., farming, logging, construction, over-grazing by livestock, off-road vehicles, and deliberate burning of vegetation).
56Moving Water Causes Most Soil Erosion Sheet Erosion – fairly uniform sheets of soils are removed as surface water flows over a slope or across a field in a wide flow.Rill Erosion – occurs when surface water forms fast-flowing rivulets that cuts small channels in the soil.Gully Erosion – occurs when rivulets of fast-flowing water join each other and with each succeeding rain cut the channels wider and deeper until they become ditches or gullies.
57Harmful Effects of Soil Erosion Loss of soil fertility and its ability to hold waterRunoff of sediment that pollutes water, kills fish and shellfish, and clogs irrigation ditches, boat channels, reservoirs, and lakes.