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Glossary

Glossary of selected terms

  • Allochthonous energy: Energy imported into an ecosystem from external sources in the form of organic material. Aphotic A zone where light intensity is too low to support photosynthesis
  • Autochthonous energy: Energy captured from abiotic sources in situ by autotrophs living within an ecosystem.
  • Autotroph: An organism that fixes carbon from its surroundings, manufacturing complex energy-storing organic compounds, generally using energy from light (photosynthesis) or inorganic chemical reactions (chemosynthesis). Autotrophs are primary producers in trophic webs.
  • Biogenic: A structure created by living organisms, e.g. a coral reef, tunnels in soils or sediment
  • C3: The most common photosynthetic pathway in plants based only on the Calvin cycle with associated energy loss to photorespiration and dependence on daytime CO2 uptake, dominating environments with abundant moisture, and cool temperatures.
  • C4: A photosynthetic pathway with a supplementary C-fixation pathway that minimises photorespiration, reduces CO2 demand and increases water use efficiency, often dominating warm and dry environments.
  • CAM: A specialised C4 photosynthetic pathway in which CO2 uptake and fixation occurs during the night, followed by internal release in daytime when light dependent photosynthesis can take place. Stomatal closure during the day, reducing moisture loss enabling survival in very hot, dry conditions.
  • Chemoautotroph: An organism that fixes carbon from its surroundings using energy from inorganic chemical reactions.
  • C:N ratio: Carbon to nitrogen ratio in biological tissues. Reflects differences in tissue composition related to nitrogen availability and capture, as well as woodiness in plants.
  • Euphotic: A zone with abundant light, and hence able to support photosynthesis.
  • Heterotroph: An organism that cannot manufacture its own food by carbon fixation and therefore derives its intake of nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are secondary and tertiary consumers. Heterotrophs are consumers in trophic webs, including decomposers, detritivores, herbivores and predators.
  • LAI: Leaf Area Index, the projected area of leaves as a proportion of the area of land in which it is measured. Useful in remote sensing for describing vegetation density.
  • Mesophotic: A zone of oderate light intensity, able to support photosynthesis.
  • Photoautotroph: An organism that fixes carbon from its surroundings using energy from light
  • Primary productivity: The amount of chemical energy, expressed as carbon biomass that autotrophs create in a given length of time.
  • Secondary productivity: Biomass of heterotrophic (consumer) organisms generated in a given length of time, driven by the transfer of organic material between trophic levels
  • Semelparous: Plant life cycle with a single reproductive episode before death.
  • SLA: Specific Leaf Area, the ratio of area of a fresh leaf to its dry mass. Positively related to plant relative growth rate.

Notes

Productivity

Descriptive profiles use ordinal descriptors (high, medium and low) of productivity, i.e. Net Primary Productivity, unless otherwise state. For terrestrial and transitional realms, these descriptors are based on estimates from an ensemble of global vegetation models (Cramer et al. 1999; Kicklighter et al. 1999; Huston & Wolverton 2009). For marine surface systems, they are based on estimates of chlorophyll a concentration for upper (Sarmiento et la. 2004; Huston & Wolverton 2009):

Ordinal descriptor Terrestrial and transitional Marine
High >2000 g dry mass m-2.yr-1 >8 mg.m-3 chlorophyll a concentration
Medium 500 – 2000 g dry mass m-2.yr-1 0.1 – 8 mg.m-3 chlorophyll a concentration
Low <500 g dry mass m-2.yr-1 <0.1 mg.m-3 chlorophyll a concentration

Leaf size

Terms describing leaf size follow Raunkiaer (1934):

Size class Leaf area
Megaphyll > 164,025 mm^2
Macrophyll 18,225-164,025 mm^2
Mesophyll 2,025-18,225 mm^2
Notophyll [2,025–4,500 mm^2]
Microphyll 225-2,025 mm^2
Nanophyll 25–225 mm^2
Leptophyll < 25 mm^2