Energy Dynamics (Trophic organization energy flow pathways, ecological efficiencies)

ENERGY DYNAMICS (Trophic organization, energy flow pathway, ecological efficiencies)

Amount of radiant energy (short wave) available to drive biosphere–atmosphere exchange of CO₂, H₂O, CH₄ and for transfer into other energy forms were determined for a tropical mangrove forest at the land ocean boundary of north-east (NE) coast of Bay of Bengal from January to December 2006. 

The mean annual incoming short wave radiation (435±32.8 W m−2) was partitioned into 29% sensible heat, 35% latent heat, 4% ground heat, 7% physical storage energy and 10% photosynthetic storage energy. The mean budget closing energy flux (68.96±24.6 W m−2) or, budget error was 15.8% of incoming short wave radiation. In Varimax factor analysis, budget closing energy flux showed high loading in association with leaf chlorophyll of different mangrove species, indicating its major role for reflectivity of the surface for short wave. 

There was significant seasonality in CO₂ exchange with net primary productivity of 14.1 μmol m−2 s−1. The mean methane emission was found higher (7.29 μg m−2 s−1) during the daytime than that of night time (1.37 μg m−2 s−1) with maximum methane emission rates of 36.1 and 21.1 μg m−2 s−1 in December and January, respectively. Stepwise multiple regression analysis between storage energy [ΔHs(P)] and fluxes of CO₂, CH₄, H (sensible heat), HL (latent heat of evaporation), ΔR (budget closer energy) showed that the combined explained variability for CO₂ flux, evapotranspiration and budget closer energy (39%) was less than that of CH₄ and sensible heat flux (46%). 

The extent of warming effect by CH₄ and sensible heat flux was predominant over the resultant cooling effect due to the processes such as photosynthesis, evapotranspiration and albedo. The mangrove forest with two trademarks of low albedo and high surface roughness was poorly coupled to the environment

Ecological efficiency

Ecological efficiency is defined as the energy supply available to trophic level N + 1, divided by the energy consumed by trophic level N.

Thinking about ecological efficiency brings the transfer of energy through trophic levels and up the food chain. In general, only about 10% of the energy consumed by one level is available to the next. For example, If hares consumed 1000 kcal of plant energy, they might only be able to form 100 kcal of new hare tissue. For the hare population to be in steady state (neither increasing nor decreasing), each year's consumption of hares by foxes should roughly equal each year's production of new hare biomass. So the foxes consume about 100 kcal of hare biomass, and convert perhaps 10 kcal into new fox biomass. In fact, this ecological efficiency is quite variable, with homeotherms averaging 1- 5% and poikilotherms averaging 5-15%. 

The overall loss of energy from lower to higher trophic levels is important in setting the absolute number of trophic levels that any ecosystem can contain. 

From this understanding, it should be obvious that the mass of foxes should be less than the mass of hares, and the mass of hares less than the mass of plants. Generally this is true, and we can represent this concept visually by constructing a pyramid of biomass for any ecosystem.