ECOSYSTEM PROCESSES
Ecosystem: an organized system made up of plants, animals, and inorganic components which are linked together by flows of energy and materials. examples…
Harnessing solar radiation is the basis of ecosystem energy flow.
Biomes: regional ecosystems with generally similar climates, soil forming conditions & plant-animal communities
tropical forests, temperate grasslands, deserts, etc...
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Plant-Environment Interactions, productivity
limiting factor of production: physical or chemical abiotic component that most inhibits biotic activity.
(sunlight, nutrients, water, temperature, physical habitat & more)
tolerance and the ecological optimum: (draw curve)
which plants dominate?
competition and ecologic niche
sunlight, temp, H2O, nutrients
photosynthesis harnesses carbon dioxide, water, and solar energy to form high energy carbohydrates:
carbon dioxide + water + solar energy → carbohydrate + oxygen
respiration: the breakdown of carbohydrates for maintenance, releasing the energy they contain:
carbohydrate + oxygen → carbon dioxide + water + heat energy
primary producers: organisms that use light energy to convert CO2 and water to carbohydrates through photosynthesis.
Gross Primary Productivity (GPP) = total amt. of energy fixed by primary producers (photosynthesis)
Net Primary Productivity (NPP) = GPP - Respiration. NPP is indirect measure of accumulation of biomass over time.
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Typical NPP: fixed carbon per square meter per year (g/m2/yr):
Terrestrial:
tropical rainforest 2200
trop. deciduous forest1300
temperate (mid latitude) forest 1200
temperate grassland 600
tundra & alpine 140
desert 50
Marine
open ocean 125
upwelling ocean zones 500
coastal algal beds, coral reefs700-2500+
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NPP geography in above table explained by limiting factor(s):
Function of water abundance in soils:
Rainfall and evaporation influence nutrient availability in an ecosystem. The rainfall in wet environments leaches (removes) nutrients from soils more than in drier environments. Therefore:
1)ecosystems in wet environments have a significant proportion of total nutrients in biomass (forests), while
2)ecosystems in desert and semi-arid (grassland) environments have a greater share of their nutrients in the soils rather than vegetation
Efficient nutrient cycling in coral reefs and rainforests overcomes otherwise limited nutrient availability.
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Oceans and Land as Habitat
Oceans cover 70% of Earth’s surface, but 99% of living volume
(land’s inhabited zone ~ 30m above surface to ~1m below, while oceans are inhabited down to ultimate depths of 11,000m).
There are far more total land species (perhaps 20 million) than marine species (perhaps 250,000).
Why?
-Diversification/speciation require the isolation of small populations by geographic barriers to dispersal. The ocean is continuous, relatively stable and uniform. The terrestrial environment is not. (only 2% of marine species inhabit the water mass itself; 98% are associated with the more diverse and fragmented bottom sediments)
The terrestrially dominant photosynthetic organisms (autotrophs) are much larger than the marine ones (most are microscopic). Why?
- Many land plants grow tall to compete for light. But average depth of seas is 4000m. (not an option)
- Living tissue is denser than sea water due to organic molecules and salts. Marine autotrophs need to be in photic zone, and smaller organisms sink more slowly than larger ones. (weight is proportional to volume, frictional resistance is proportional to surface area, and small objects have a large surface area in relation to their volume)
- Rapid herbivory and need to be in photic zone favors a more rapid reproduction than would be possible with larger organisms. Small organisms can reproduce more rapidly.
- Small organisms have a greater nutrient uptake to mass ratio, and marine organisms cannot afford to have the larger mass required by the roots that most land plants have.
- Thus, being small helps.
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VEGETATION CHANGE THROUGH TIME
plant succession: where one type of plant is replaced by another.
pioneer species: dominant invaders after a major disturbance, often fast growing and aggressive, but generally short-lived.
seral species: those that dominate after the pioneers
W. forests – Douglas-fir, near coasts Sitka Spruce, in riparian environments Red Alder
climax vegetation: the phase of vegetation succession where the structure of the plant community sustains itself indefinitely, without major changes. (in absence of disturbance) W. forests: Western Redcedar, Western Hemlock
WHY DO THESE TREES BECOME DOMINANT, EVEN IF THEY DON’T DOMINATE FIRST?
Some Kinds of Succession:
1. linear succession: when plants cause changes in their environment which result in progressive patterns of vegetation change that are generally not repeated. example: lake infilling
2. cyclical succession: when a pattern of vegetation leads to a new pattern, only to be later succeeded by the original pattern.
ex: forestation of permafrost areas (draw)
3. allogenic succession: when an outside force induces vegetation change that has long term persistence.
Example: planting of European Beach Grass on Nehalem Spit (OR Coast) forestation now happens due to dune stabilization
Special module: Pine beetle invasion
-uniformly old age stands:
-warmer winters: (less severe and shorter cold air outbreaks)
-longer summer reproductive season: (warmth)
-warmer summers: evapotranspiration ↑ more water stress lowers…
-beetle population dynamics: