Matter cycles within ecosystems energy flows unidirectionally through ecosystems matter cycles at local and global scales movement of elements among various global pools pool size and flux rates

Matter cycles within ecosystems fluxes determined by both biotic and abiotic processes

Matter cycles within ecosystems fluxes determined by both biotic and abiotic processes

Matter cycles within ecosystems fluxes determined by both biotic and abiotic processes energy movement between ecosystem compartments parallels movement of matter CO 2 + H 2 O + (e - ) ↔ CH 2 O + ½O 2

Matter cycles within ecosystems fluxes determined by both biotic and abiotic processes energy movement between ecosystem compartments parallels movement of matter global pools serve as sources or sinks

The global water cycle physical analogy for material cycling pools and fluxes produced by biotic processes are relatively insignificant energy absorption and heat release drive the global water cycle Units = km 3 /yr

The global carbon cycle carbon cycles between biotic and abiotic CO 2 compartments via photosynthesis and respiration

The global carbon cycle carbon cycles between biotic and abiotic CO 2 compartments via photosynthesis and respiration –oceans –atmosphere –fossil carbon –terrestrial biomass Units = g C/yr

The global carbon cycle carbon cycles between biotic and abiotic CO 2 compartments via photosynthesis and respiration oceans serve as massive carbon sinks

The global carbon cycle carbon cycles between biotic and abiotic CO 2 compartments via photosynthesis and respiration oceans serve as massive carbon sinks the atmosphere is currently a carbon sink

The global carbon cycle fossil carbon deposits are now an important carbon source

The global carbon cycle fossil carbon deposits are now an important carbon source considerable local variation in carbon storage and release by terrestrial biomass –P/R ratio expresses the source-sink carbon budget of terrestrial biomass –role of biological decomposers

The global carbon cycle fossil carbon deposits are now an important carbon source considerable local variation in carbon storage and release by terrestrial biomass global carbon flux estimates can’t account for 1.8 × g y -1

The global nitrogen cycle the most biologically important N fluxes involve NO 3 atmospheric nitrogen pool is huge nitrification pathway denitrification pathway biological nitrogen fixation Units = g N/yr

The global nitrogen cycle the nitrogen cycle has been disrupted by human activity –agricultural fertilizer –petroleum combustion

The global nitrogen cycle the nitrogen cycle has been disrupted by human activity NO and NO 2 contribute to acid precipitation N 2 O is a greenhouse gas 200 times more potent than CO 2

The global phosphorus cycle source of biologically available phosphorus is weathering of bedrock –atmospheric pool is not significant –delivery rate of new P is much slower than its rate of biotic cycling –most available P is from decomposing organic material

The global phosphorus cycle source of biologically available phosphorus is weathering of bedrock –assimilated by plants as orthophospate, PO 4 –incorporated into organic tissues as particulate organic phosphate

The global phosphorus cycle source of biologically available phosphorus is weathering of bedrock also occurs as insoluble colloidal phosphate and as mineral phosphate precipitates soil and ocean pools are large, but only a tiny fraction is actually available

The global phosphorus cycle terrestrial NPP is often phosphorus limited when N is supplied phosphorus containing minerals are frequently mined and added to fertilizer runoff can be hazardous to aquatic ecosystems

The global phosphorus cycle most freshwater P is sequestered within biomass, especially phytoplankton –available PO 4 limits NPP phosphate enriched runoff increases aquatic NPP –leads to eutrophication –increases BOD

The global sulfur cycle. poorly understood –primary natural sources are volcanoes and hydrothermal vents –S does not reside in atmosphere for long, but atmospheric flux is large –ocean is currently a sulfur sink –fossil fuel combustion disrupts sulfur cycle

Global element cycles often interact in complex ways Example: –NPP limited by nitrogen availability –can influence global climate change –a terrestrial biome with high biomass storage can be a carbon sink or source