Biomass and primary productivity relationship

Energy flow & primary productivity (article) | Khan Academy

biomass and primary productivity relationship

In ecology, primary production is the synthesis of organic compounds from atmospheric or (GPP is sometimes confused with Net Primary productivity, which is the rate at which photosynthesis or . Biomass based NPP estimates result in underestimation of NPP due to incomplete accounting of these components. However. and net primary productivity were made in an old-growth pure stand of Alnus viridis in central The above ground biomass and the annual production of . Leaf area index (LAI): Using the relationship between leaf number per branch and. Answer to: The relationship between biomass and primary productivity is that By signing up, you'll get thousands of step-by-step solutions to your.

And, perhaps most problematically, almost every living thing on Earth would eventually run out of food and die. Why would this be the case? In almost all ecosystems, photosynthesizers are the only "gateway" for energy to flow into food webs networks of organisms that eat one another.

If photosynthesizers were removed, the flow of energy would be cut off, and the other organisms would run out of food. In this way, photosynthesizers lay the foundation for every light-receiving ecosystem. Producers are the energy gateway Plants, algae, and photosynthetic bacteria act as producers. Producers are autotrophs, or "self-feeding" organisms, that make their own organic molecules from carbon dioxide.

Photoautotrophs like plants use light energy to build sugars out of carbon dioxide. The energy is stored in the chemical bonds of the molecules, which are used as fuel and building material by the plant.

biomass and primary productivity relationship

The energy stored in organic molecules can be passed to other organisms in the ecosystem when those organisms eat plants or eat other organisms that have previously eaten plants. In this way, all the consumers, or heterotrophs "other-feeding" organisms of an ecosystem, including herbivores, carnivores, and decomposers, rely on the ecosystem's producers for energy. If the plants or other producers of an ecosystem were removed, there would be no way for energy to enter the food web, and the ecological community would collapse.

That's because energy isn't recycled: Image based on similar image by J. The availability of water, obviously, is not an issue though its salinity can be.

biomass and primary productivity relationship

Similarly, temperature, while affecting metabolic rates see Q10ranges less widely in the ocean than on land because the heat capacity of seawater buffers temperature changes, and the formation of sea ice insulates it at lower temperatures. However, the availability of light, the source of energy for photosynthesis, and mineral nutrientsthe building blocks for new growth, play crucial roles in regulating primary production in the ocean.

The relationship between biomass and primary productivity is that |

This is a relatively thin layer 10— m near the ocean's surface where there is sufficient light for photosynthesis to occur. Light is attenuated down the water column by its absorption or scattering by the water itself, and by dissolved or particulate material within it including phytoplankton.

Net photosynthesis in the water column is determined by the interaction between the photic zone and the mixed layer. Turbulent mixing by wind energy at the ocean's surface homogenises the water column vertically until the turbulence dissipates creating the aforementioned mixed layer.

The deeper the mixed layer, the lower the average amount of light intercepted by phytoplankton within it. The mixed layer can vary from being shallower than the photic zone, to being much deeper than the photic zone. When it is much deeper than the photic zone, this results in phytoplankton spending too much time in the dark for net growth to occur.

The maximum depth of the mixed layer in which net growth can occur is called the critical depth.

Trophic Efficiency

As long as there are adequate nutrients available, net primary production occurs whenever the mixed layer is shallower than the critical depth. Both the magnitude of wind mixing and the availability of light at the ocean's surface are affected across a range of space- and time-scales. The most characteristic of these is the seasonal cycle caused by the consequences of the Earth's axial tiltalthough wind magnitudes additionally have strong spatial components. Consequently, primary production in temperate regions such as the North Atlantic is highly seasonal, varying with both incident light at the water's surface reduced in winter and the degree of mixing increased in winter.

Energy flow & primary productivity

In tropical regions, such as the gyres in the middle of the major basinslight may only vary slightly across the year, and mixing may only occur episodically, such as during large storms or hurricanes. Annual mean sea surface nitrate for the World Ocean. Data from the World Ocean Atlas Mixing also plays an important role in the limitation of primary production by nutrients.

Inorganic nutrients, such as nitratephosphate and silicic acid are necessary for phytoplankton to synthesise their cells and cellular machinery. Because of gravitational sinking of particulate material such as planktondead or fecal materialnutrients are constantly lost from the photic zone, and are only replenished by mixing or upwelling of deeper water. This is exacerbated where summertime solar heating and reduced winds increases vertical stratification and leads to a strong thermoclinesince this makes it more difficult for wind mixing to entrain deeper water.

Consequently, between mixing events, primary production and the resulting processes that leads to sinking particulate material constantly acts to consume nutrients in the mixed layer, and in many regions this leads to nutrient exhaustion and decreased mixed layer production in the summer even in the presence of abundant light. However, as long as the photic zone is deep enough, primary production may continue below the mixed layer where light-limited growth rates mean that nutrients are often more abundant.

Iron[ edit ] Another factor relatively recently discovered to play a significant role in oceanic primary production is the micronutrient iron. A major source of iron to the oceans is dust from the Earth's desertspicked up and delivered by the wind as aeolian dust. In regions of the ocean that are distant from deserts or that are not reached by dust-carrying winds for example, the Southern and North Pacific oceansthe lack of iron can severely limit the amount of primary production that can occur.

biomass and primary productivity relationship

These areas are sometimes known as HNLC High-Nutrient, Low-Chlorophyll regions, because the scarcity of iron both limits phytoplankton growth and leaves a surplus of other nutrients. Some scientists have suggested introducing iron to these areas as a means of increasing primary productivity and sequestering carbon dioxide from the atmosphere. Gross production is almost always harder to measure than net, because of respiration, which is a continuous and ongoing process that consumes some of the products of primary production i.

Also, terrestrial ecosystems are generally more difficult because a substantial proportion of total productivity is shunted to below-ground organs and tissues, where it is logistically difficult to measure. Shallow water aquatic systems can also face this problem. Scale also greatly affects measurement techniques. The rate of carbon assimilation in plant tissues, organs, whole plants, or plankton samples can be quantified by biochemically based techniquesbut these techniques are decidedly inappropriate for large scale terrestrial field situations.

There, net primary production is almost always the desired variable, and estimation techniques involve various methods of estimating dry-weight biomass changes over time. Biomass estimates are often converted to an energy measure, such as kilocalories, by an empirically determined conversion factor. Terrestrial[ edit ] In terrestrial ecosystems, researchers generally measure net primary production NPP. Although its definition is straightforward, field measurements used to estimate productivity vary according to investigator and biome.

Field estimates rarely account for below ground productivity, herbivory, turnover, litterfallvolatile organic compoundsroot exudates, and allocation to symbiotic microorganisms.

biomass and primary productivity relationship

There are a number of comprehensive reviews of the field methods used to estimate NPP. The major unaccounted pool is belowground productivity, especially production and turnover of roots.

Belowground components of NPP are difficult to measure. Gross primary production can be estimated from measurements of net ecosystem exchange NEE of carbon dioxide made by the eddy covariance technique.

During night, this technique measures all components of ecosystem respiration. This respiration is scaled to day-time values and further subtracted from NEE. In systems with persistent standing litter, live biomass is commonly reported. Measures of peak biomass are more reliable if the system is predominantly annuals. However, perennial measurements could be reliable if there were a synchronous phenology driven by a strong seasonal climate.

These methods may underestimate ANPP in grasslands by as much as 2 temperate to 4 tropical fold.

biomass and primary productivity relationship

Wetland productivity marshes and fens is similarly measured. In Europeannual mowing makes the annual biomass increment of wetlands evident.