- NPP is highest in the tropics
- NPP in terrestrial systems is often limited by climatic factors: Temperature and Precipitation
- NPP-aquatic systems-control-light, nutrients
- Element cycling in Ecosystems
• there is continual recycling between the organisms and the physical environment
• nutrients, unlike energy, are retained within the ecosystem
- Compartments
• Organisms (biosphere)
• Air (atmosphere)
• water (hydrosphere)
• land (lithosphere)
- Reservoirs VS Fluxes
• Reservoirs (stock)
- where energy (C) or nutrients are stored
• Flux
- movement of energy or nutrients between reservoirs
- measured as a rate (unit/time)
- Redox
• oxidized -low energy
- follow any given nutrient through time. there would be a continual alternation between living and nonliving compartments of the ecosystem
- gains and losses from outside of the ecosystem are small when compared to the rate at which nutrients are cycled within the system
- ecosystem element cycling can be driven by an organism's need for growth, or by an organism's need for energy. Physical factors can also move elements (ex. wind moving sand)
- Why do nutrients limit plant productivity?
• Photosynthesis uses a lot of N
- 50% of N in leaves tied up in Rubisco and other photosynthetic enzymes
• Nitrogen is often hard to come by
- type of N-organic
• P needed to make DNA and ATP
• P-type-inorganic
- N2 fix
• Abiotic fixation
- lightening
• Biotic fixation
- free living bacteria
- symbiotic bacteria
• Bacteria form a mutualistic symbiotic relationship with plant roots
• N2 -> NH4+ , NO3-
• Plants give bacteria carbohydrates and get N in return
• N2-triple bond
- uses 25% of energy made from photosynthesis to break
- Mineralization
• chemical conversion of organic matter into inorganic nutrients
- Nitrogen cycle
• N changes forms due to enzymatic (biological) redox reactions
• N is source of E for some microbes,
• most terrestrial ecosystems (outside of tropics) are N limited
Similar posts:
Ecosystems Lections