Communities + physical processes interconnect to form ecosystems Ecosystems are connected by: 1. energy flow between trophic levels; energy also released as heat energy into environment Autotrophs = 10 producers Primary productivity = amount of C fixed in an ecosystem by: CO2 + H20 + light --> (C6H1206) + O2 Heterotrophs Consumers: herbivores, omnivores, carnivores Decomposers 2. Nutrient and water cycling (Biogeochemical cycling) 1. water, 2. carbon, 3. nitrogen, 4. phosphorus Humans have impacts on ecosystems

Energy flow (also refer to Fig. 20.3 & 20.7) Only ~10 % transfers between levels. Loss due to: Metabolism and waste

BioGeoChemical cycles = Nutrients cycle btwn biotic & abiotic forms Definitions of: Reservoirs and fluxes, mineralization, fixation/assimilation Flux rate dependent on ? Major Biogeochemical cycles: Atmospheric cycles = carbon and nitrogen; Sedimentary = phosphorus; Hydrologic 9 9

Carbon Reservoirs = ? Transformations?

Fertilizer, atmospheric deposition Nitrogen - why is N impt? - what is symbiotic N fixation? - cause and results of excess N? Dead organisms NH4+ ammonium NO2- nitrite NO3- nitrate Organic matter Decomposition Mineralization Plants Assimilation Fungi, bacteria, inverts Fungi, bacteria N2 Nitrogen fixation Rhizobium Denitrification Anaerobic bacteria Industrial inputs: Fertilizer, atmospheric deposition

Phosphorus Pools? Transformations? Cause and consequences of excess P in aquatic systems

PO4- is difficult to acquire 80 % of plants have mycorrhizal symbionts to help (fungi); other benefits (+H20) offset cost

Biotic factors increase nutrient retention – how? Excessive disturbance decreases retention – why?

Human Impact 1 Reduced biodiversity, habitat loss, habitat fragmentation

Human Impact 2 Pollution: air, water, land Reduction in ozone layer

Human Impact 3 - Excess N & P

Human Impact 4 - Accelerated release of CO2