Decomposers, Aquatic and Nutrient Cycles

1. First Trophic Level Second Trophic Level Third Trophic Level Fourth Trophic Level Producers (plants) Primary consumers (herbivores) Secondary consumers (carnivores) Tertiary consumers (top carnivores) Heat Heat Heat Heat Solar energy Heat Heat Heat Detritvores (decomposers and detritus feeders) Decomposers, Aquatic and Nutrient Cycles

2. Three 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.

3. Hydrologic Cycle • Collects, 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 caps • 20% in groundwater • 0.4% in lakes and rivers (0.01% of all water!) • Anytime of year, the atmosphere holds only 0.0001% of water on the planet. • Although large quantities are evaporated and precipitated each year • About 84% of water vapor comes from the ocean

4. Main Processes of the Hydrologic Cycle • Evaporation – conversion of water into water vapor • Transpiration – evaporation from leaves of water extracted from soil by roots • Condensation – conversion of water vapor into droplets of liquid water • Precipitation – rain, sleet, hail, and snow • Infiltration – movement of water into soil • Percolation – downward flow of water through soil and permeable rock formations to groundwater storage areas called aquifers • Runoff – downslope surface movement back to the sea to resume cycle

5. 3 4 2 1 5 6 Hydrologic Cycle 7

6. Global Air Circulation & Regional Climates • Uneven heating of the Earth’s Surface • Air is more heated at the equator and less at the poles.

7. Global Air Circulation & Regional Climates • Seasonal changes in temperature and precipitation

8. Insolation B A C

9. Solar Energy

10. Rainy Season Seasonal shift in rainy/dry seasons

11. Matter Cycling in Ecosystems • Nutrient – any atom, ion, or molecule an organism needs to live, grow, or reproduce • Some (such as C, O, H, N, P, S, and Ca) are needed in fairly large amounts • Some (such as Na, Zn, Cu, and I) are only needed in trace amounts.

12. Nutrient Cycles • Compartment – represents a defined space in nature • Pool – amount of nutrients in a compartment • Flux rate – the quantity of nutrient passing from one pool to another per unit time.

13. Major Nutrient Cycle Pathways Flux rate Pool

14. Plants Herbivores Water Hypothetical Phosphorus Nutrient Cycle 126 81 1.4 9 133 7 45 19 100 9.5 Flux rate and pool size together define the nutrient cycle within any particular ecosystem

15. Nitrogen Cycle • Nitrogen 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 N • Microbes mostly responsible for N cycle

16. 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).

17. Ecosystem Nitrogen Cycle Gaseous N2 Nitrogen Fixation Ammonification Ammonia: NH3, NH4+ 1. Nitrification Nitrogenous Waste Food Web Nitrite: NO2- 2. Nitrification Nitrate: NO3- Denitrification Loss by Leaching

18. Proteins Provides Energy Requires Energy Nitrate Energy and the Nitrogen Cycle

19. Nitrogen Cycle

20. Phosphorous Cycle • The 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 cycle • Guano (bird poop), mined sediments, and ‘uphill’ movement of wastewater are the main ways phosphorous is cycled in our lifetime • Geologic process (mountain formations / uplifting of ocean sediments) cycle phosphorus in geologic time

21. Phosphorous Cycle Guano Food web River Flow Soil Ocean Water Geologic Uplifting Food web Mining Sediments

22. Phosphorous 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.

23. Phosphorous Cycle

24. Sulfur Cycle • The sulfur cycle is a gaseous cycle. • Sulfate (SO4) is the principal biological form • Essential for some amino acids • Usually not limiting, but the formation of iron sulfides converts the insoluble form of phosphorous to a soluble form • Sulfur 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.

25. Volcanoes, Sea spray Excretion Sulfur bacteria Food Web SO4 Rapid Cycling Aerobic Sulfide-oxidizers Anaerobic Sulfur-reducers Organic Matter H2S S Heterotrophic microorganisms Sulfur bacteria OH SH +Fe3 FeS Very Slow Flux Rate Soluble Phosphorous FeS2 Black Anaerobic Mud Sulfur Cycle

26. Sulfur Cycle

27. Carbon Cycle • Carbon is the basic building block of organic compounds necessary for life. • The carbon cycle is a global gaseous cycle • Carbon dioxide makes up 0.036% of the troposphere and is also dissolved in water • Key component of nature’s thermostat • Too much taken out of the atmosphere, temp’s decrease • Too much added to atmosphere, temp’s increase

28. Primary Productivity Heat Energy Chemical Energy (ATP) Solar Energy CO2 Respiration Photosynthesis C6H12O6 O2 Available to Consumers Biomass (g/m2/yr) GPP NPP

29. Carbon Cycle Atmospheric / Aquatic CO2 Photosynthesis Respiration Combustion of wood / fossil fuels Food Web Weathering Sedimentation Limestone Rocks Volcanic Action

30. The Recyclers • Detritus – parts of dead organisms and cast-off fragments and wastes of living organisms • Detritivores – 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

31. Detritus Feeders and Decomposers Without detritus feeders and decomposers, the lack of nutrients would quickly stop primary production!

32. Turnover 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 period • Turnover time – the time needed to replace a quantity of a substance equal to its amount in the compartment • Residence time – the time a nutrient stays in a compartment (similar to turnover time)

33. Nutrient Cycles in Forests • Inputs – outputs = storage • Nutrients accumulate in the leaves and wood over time

34. Nutrient Storage in Trees is Temperature and Vegetation Type Related In cold climates nutrients are tied up in the soil.

35. Nutrient Turnover Time is Temperature Related Turnover time – the time an average atom will remain in the soil before it is recycled into the trees or shrubs

36. Net 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 is the time for one cycle of decomposition.

37. Rapid Cycling in the Tropics • Reasons for rapid cycling in the tropics: • Warm climate • No winter to retard decomposition • An army of decomposers • Abundant mycorrhizal fungi on shallow roots • Fungi that grow symbiotically with plant roots • Facilitate water and nutrient uptake

38. The 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 system • Waters in local streams and rivers can have as few nutrients as rain water • Because 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

39. Tropical 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?

40. Standing Biomass • Standing 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

41. Tropical Soils • In 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.

42. Watershed Biogeochemistry • Watershed – catchment or drainage basin of a river • Streams and rivers are main conduits of nutrient loss • Vegetation type can influence nutrient loss: Mean calcium concentrations (% dry wt) in three plant species.

43. Normal Nutrient Loss • Rain runoff is the major vector of nutrient loss from most ecosystems a Not determined, but very low; b Watershed 4 only

44. Stream Nitrite Concentration Note Scale Change Deforestation Can Increase Loss of Nutrients From Areas Due to Runoff Other stream nutrient increase two years after the deforestation: Calcium 417%, Magnesium 408%, Potassium 1,558%, Sodium 177%

45. Riparian Buffer Zone • Areas 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.

46. Three Zone Riparian Buffer

47. Other Methods to Control Erosion • Silt Fence / hay bales • Allows water to pool so that sediment is dropped.

48. What is Soil? • Complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and billions of living organisms (mostly decomposers) • Soil is created by • Weathering of rock • Deposit of sediments by erosion • Decomposition of organic matter in dead animals

49. Soil 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.

50. Immature soil O horizon Leaf litter A horizon Topsoil Regolith B horizon Subsoil Bedrock C horizon Parent material Young soil Mature soil Soil Horizons (Profiles)