flujo de energia amb terres y acuatic

8/6/2019 Flujo de Energia Amb Terres y Acuatic

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Energy flow within terrestrial and

aquatic ecosystems Energy available for growth and reproduction (as a

function of food availability):

= GPE - NPE

Tells usamount of energy flow

Not rate at which energy flows

Ecosystem and community development is

regulated by therate of energy flow as well

How fast does available energy flow between

trophic levels


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Second question of energy flow within a system is: how fast does energy transfer occur?

Residence time = inverse of energy transfer rate RT = biomass / net productivity

RT (yr) = energy stored in biomass (kJ m )-2

Net productivity (kJ m yr )-2 -1

Measure of biomass accumulation within any given trophic level

(g(C) m )

(g(C) m yr )

-2

-2 -1or


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Wet tropical rainforest:

Produce about 1800 g m-2 yr-1

andLiving average biomass of 42 000 g m-2

42 000 g m-2

1800 g m-2 yr-1= RT = 23 yr


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Temperate scrubland:


and

Living average biomass of 6 000 g m-2

6 000 g m-2

600 g m-2

yr-1

= RT = 10 yr


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Open ocean:


andLiving average biomass of 3 g m-2

3 g m-2

125 g m-2 yr-1= RT = 0.02 yr

(About 9 days)


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Ricklefs (1972)

Peat bogs near Root Springs, Concord MA

Herbivores: assimilate energy at a rate of 0.31 J m-2 s-1

Aquatic plants and algae produce 0.09 J m-2 s-1

So, where is the other 0.22 J m-2 s-1 coming from?


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Ecosystems do not exist

individually autochothonous production = energy fixed

within the system

allochothonous production = energy fixed

outside of the system

energy can be from input from external

system


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General Trends

assimilation efficiency increases at higher trophiclevels

NPE decreases at higher trophic levels

GPE decreases at higher trophic levels

Ecological efficiency averages about only 10%

GPE(n) / GPE (n-1) = efficiency of transfer

between specific trophic levels

Aquatic systems typically support more trophic

levels than terrestrial systems


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Nutrient cycles

Biogeochemical sources

Biotic = nutrients released from decomposers

Abiotic = nutrients released from erosion of

substrate or fixed by primary producers Indirect = nutrients stored in soil

Direct = nutrients absorbed directly from

decomposers Indirect = higher nutrient capital

Amount of stored nutrients within the system


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11/12

Atmosphere

Primary

producers

ConsumersDead organic

material

Soil

Indirect nutrient cycling

Nutrients can flow from source to source

Length of time at each source dependant

upon source characteristics


12/12

Atmosphere

Primary

producers

ConsumersDead organic

material

Soil

Direct nutrient cycling

Nutrient uptake increased by presence

of mycorrhizae (fungal producers)

flujo de energia amb terres y acuatic

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