Chiariello, N. Mooney and K. Williams Growth, carbon allocation and cost of plant tissues. Chapman and Hall, London. Rodin, L. Scripta Technica Ltd. Hussey, A. Long Seasonal changes in weight of above-and below-ground vegetation and dead plant material in a salt marsh at Colne Point, Essex. Hansson, A. Andren Below-ground plant production in a perennial grass ley Festuca pratensis Huds. Long, S. Mason Saltmarsh Ecology 1st edn.
Blackie, Glasgow, London. Evans Primary production and the disappearance of dead vegetation in an old field in South-eastern Michigan. Ecology 45 , 49— Lomnicki, A. Bundola and K.
Jankowska Modification of the Wiegert-Evans method for estimation of net primary production. Ecology 49 , — Suppose we have some amount of plant matter consumed by hares, and the hares are in turn consumed by foxes.
The following diagram Figure 2 illustrates how this works in terms of the energy losses at each level. A hare or a population of hares ingests plant matter; we'll call this ingestion. Part of this material is processed by the digestive system and used to make new cells or tissues, and this part is called assimilation. What cannot be assimilated, for example maybe some parts of the plant stems or roots, exits the hare's body and this is called excretion.
The hare uses a significant fraction of the assimilated energy just being a hare -- maintaining a high, constant body temperature, synthesizing proteins, and hopping about. This energy used lost is attributed to cellular respiration. The remainder goes into making more hare biomass by growth and reproduction that is, increasing the overall biomass of hares by creating offspring.
The conversion of assimilated energy into new tissue is termed secondary production in consumers, and it is conceptually the same as the primary production or NPP of plants. In our example, the secondary production of the hare is the energy available to foxes who eat the hares for their needs. Clearly, because of all of the energy costs of hares engaged in normal metabolic activities, the energy available to foxes is much less than the energy available to hares. Just as we calculated the assimilation efficiency above, we can also calculate the net production efficiency for any organism.
This efficiency is equal to the production divided by the assimilation for animals, or the NPP divided by the GPP for plants. The "production" here refers to growth plus reproduction. These ratios measure the efficiency with which an organism converts assimilated energy into primary or secondary production. These efficiencies vary among organisms, largely due to widely differing metabolic requirements. The reason that some organisms have such low net production efficiencies is that they are homeotherms , or animals that maintain a constant internal body temperature mammals and birds.
This requires much more energy than is used by poikilotherms , which are also known as "cold-blooded" organisms all invertebrates, some vertebrates, and all plants, even though plants don't have "blood" that do not regulate their temperatures internally.
Just as we can build our understanding of a system from the individual to the population to the community, we can now examine whole trophic levels by calculating ecological efficiencies. You might think of it as the efficiency of hares at converting plants into fox food. Note that the ecological efficiency is a "combined" measure that takes into account both the assimilation and net production efficiencies.
You can also combine different species of plants and animals into a single trophic level, and then examine the ecological efficiency of for example all of the plants in a field being fed on my all of the different grazers from insects to cows.
Thinking about the overall ecological efficiency in a system brings us back to our first rule for the transfer of energy through trophic levels and up the food chain. For example, If hares consumed kcal of plant energy, they might only be able to form 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 kcal of hare biomass, and convert perhaps 10 kcal into new fox biomass.
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 see Figure 3.
A pyramid of biomass showing producers and consumers in a marine ecosystem. Pyramids of Biomass, Energy, and Numbers A pyramid of biomass is a representation of the amount of energy contained in biomass, at different trophic levels for a given point in time Figure 3, above, Figure 4-middle below.
The amount of energy available to one trophic level is limited by the amount stored by the level below. Because energy is lost in the transfer from one level to the next, there is successively less total energy as you move up trophic levels. In general, we would expect that higher trophic levels would have less total biomass than those below, because less energy is available to them. We could also construct a pyramid of numbers , which as its name implies represents the number of organisms in each trophic level see Figure 4-top.
For the grassland shown in Figure 4-top, the bottom level would be quite large, due to the enormous number of small plants grasses. For other ecosystems such as the temperate forest, the pyramid of numbers might be inverted: for instance, if a forest's plant community was composed of only a handful of very large trees, and yet there were many millions of insect grazers which ate the plant material.
Just as with the inverted pyramid of numbers, in some rare exceptions, there could be an inverted pyramid of biomass, where the biomass of the lower trophic level is less than the biomass of the next higher trophic level. The oceans are such an exception because at any point in time the total amount of biomass in microscopic algae is small. Thus a pyramid of biomass for the oceans can appear inverted see Figure 4b-middle.
You should now ask "how can that be? This is a good question, and can be answered by considering, as we discussed above, the all important aspect of "time". Even though the biomass may be small, the RATE at which new biomass is produced may be very large. Thus over time it is the amount of new biomass that is produced, from whatever the standing stock of biomass might be, that is important for the next trophic level.
We can examine this further by constructing a pyramid of energy , which shows rates of production rather than standing crop. Once done, the figure for the ocean would have the characteristic pyramid shape see Figure 4-bottom. Algal populations can double in a few days, whereas the zooplankton that feed on them reproduce more slowly and might double in numbers in a few months, and the fish feeding on zooplankton might only reproduce once a year. Thus, a pyramid of energy takes into account the turnover rate of the organisms, and can never be inverted.
Note that this dependence of one trophic level on a lower trophic level for energy is why, as you learned in the lectures on predation, the prey and predator population numbers are linked and why they vary together through time with an offset. Figure 4: Pyramids of numbers, biomass, and energy for various ecosystems.
The Residence Time of Energy. We see that thinking about pyramids of energy and turnover time is similar to our discussions of residence time of elements. But here we are talking about the residence time of "energy".
This difference in residence time between aquatic and terrestrial ecosystems is reflected in the pyramids of biomass, as discussed above, and is also very important to consider in analyzing how these different ecosystems would respond to a disturbance, or what scheme might best be used to manage the resources of the ecosystem, or how you might best restore an ecosystem that has been degraded e.
Humans and Energy Consumption All of the animal species on Earth are consumers, and they depend upon producer organisms for their food. For all practical purposes, it is the products of terrestrial plant productivity and some marine plant productivity that sustain humans.
What fraction of the terrestrial NPP do humans use, or, "appropriate"? It turns out to be a surprisingly large fraction, which launches us immediately into the question of whether this appropriation of NPP by humans is sustainable. Let's use our knowledge of ecological energetics to examine this very important issue. Why NPP? Because only the energy "left over" from plant metabolic needs is available to nourish the consumers and decomposers on Earth.
In a cropland NPP and annual harvest occur in the same year. In forests, annual harvest can exceed annual NPP for example, when a forest is cut down the harvest is of many years of growth , but we can still compute annual averages.
Note that the following estimates are being successively revised in the literature, but the approach to the problem is always the same. Outputs: 2 Scenarios Total productivity of lands devoted entirely to human activities. This includes total cropland NPP, and also energy consumed in setting fires to clear land.
A high estimate is obtained by including lost productive capacity resulting from converting open land to cities, forests to pastures, and due to desertification and other overuse of land.
This is an estimate of the total human impact on terrestrial productivity. Table 1 provides estimates of total NPP of the world. There is some possibility that below-ground NPP is under-estimated, and likewise marine NPP may be underestimated because the contribution of the smallest plankton cells is not well known. Estimate of human harvest of grains and other plant crops is 1. This implies loss, spoilage, or wastage of 0.
Our low estimate uses 2. Amount used for firewood, especially in tropics, is not. The table gives a low estimate. The total is The High Calculation: See Table 3 For the high estimate we now include both co-opted NPP and potential NPP lost as a consequence of human activities: a Croplands are likely to be less productive than the natural systems they replace.
If we use production estimates from savanna-grasslands, it looks like cropland production is less by 9 Pg. The total for the high estimate is Holmes, R. Bird community dynamics and energetics in a northern hardwoods ecosystem. Journal of Animal Ecology Huggett, B. Hawley and C. Long-term calcium addition increases growth release, wound closure, and health of sugar maple Acer saccharum trees at the Hubbard Brook Experimental Forest.
Canadian Journal of Forest Research Jenkins, J. Chojnacky, L. Heath and R. National-scale biomass estimators for United States tree species. Forest Science Johnson, C. Driscoll, T. Siccama and G. Element fluxes and landscape position in a northern hardwood forest watershed-ecosystem.
Ecosystems Keenan, T. Hollinger, G. Bohrer, D. Dragoni, J. Munger, H. Schmid, and A. Increase in forest water use efficiency as atmospheric carbon dioxide concentrations rise. Nature, in press. Keeton, W. Whitman, G. McGee and C. Late-successional biomass development in northern hardwood-conifer forests of the northeastern United States.
Kelty, M. Forest Ecology and Management Lichstein, J. Wirth, H. Horn and S. Biomass chronosequences of United States forests: Implications for carbon storage and forest management, pp. Wirth et al. Ecological Studies , Springer-Verlag, Berlin. Long, R. Horsley, R. Hallett and S. Sugar maple growth in relation to nutrition and stress in the northeastern United States.
Ecological Applications — Norby, R. DeLucia, B. Gielen, C. Calfapietra, C. Giardina, J. King, J. Ledford, H. McCarthy, D. Moore, R. Ceulemans, P. De Angelis, A. Finzi, D. Karnosky, M. Kubiske, M. Lukac, K. Pregitzer, G. Scarascia-Mugnozza, W. Schlesinger and R. Forest response to elevated CO 2 is conserved across a broad range of productivity.
Proceedings of the National Academy of Sciences Reiners, W. Driese, T. Fahey and K. Effects of three years of regrowth inhibition on the resilience of a clear-cut northern hardwood forest. Ecosystems , doi Ryan, M. Binkley, J. This is in agreement with Fromard et al. The present study showed that mangrove communities with similar mean height and mean diameter produced different biomass production with different basal area Fig.
For example, mean height 6. This variation is due to the differences in basal area of the stand. These results are generally consistent with the findings of Fromard et al. This study showed that the mean above-ground biomass of This value was higher than those reported for subtropical mixed mangrove forest at Ishigaki Island, southern Japan The present value of accumulation of mean aboveground biomass was within the converted range of AGB from aboveground biomass carbon for Sundarbans mangrove forests Compared to the previous studies, the present study indicates that biomass productivity of the mangrove species in the present study was relatively high among the mangrove forests in the tropical and subtropical areas, showing that mean annual wood production of 7.
A similar observation was made by Putz and Chan , who reported that the average stem production over 31 years for a Rhizophora - Bruguiera forest in Malaysia was 6. The mean value of AGB increment was higher than the 5. It is important to mention that AGB of the studied mangrove communities is accounted for mainly due to stem biomass and is also a permanent indicator of biomass increment.
Small branches and leaves mainly contributed in the litterfall production. This value is higher than the records for Ceriops tagal Perr. This mean value is similar with records for other mangrove species at New South Wales 1. Mangroves are usually coping a saline environment with the stress of high water tables but physiologically dry condition for the plants and deficiency of oxygen Ball ; Havanond and Maxwell , so a large portion of biomass is allocated to the underground parts of the mangrove species to adapt to the harsh environment.
This larch species must also cope with a harsh environment of limited soil nutrients and low soil temperature Kajimoto et al. This is the first report of litterfall production of the Sundarbans mangrove forest, Bangladesh.
The mean total litterfall production The mean total litterfall of the present study was higher than those recorded on southeastern Mexican mangrove forest 3. Mangrove leaves are shed continuously throughout the year especially in case of a community of mixed mangrove species.
Day et al. Thus, regular tidal inundation, lower salinity level, and regular nutrient input may be the factors related to higher mean productivity in the present study.
This study showed that maximum leaf litterfall of the investigated species occurred in winter or dry season and late summer or rainy season. In many mangrove areas, similar findings were observed that peak litterfall occurs during the rainy season Leach and Burgin ; Day et al.
In the tropics, where temperatures are always favorable for tree growth, seasonal development is often not correlated with climate. In tropical rain forest many trees flush and flower at the same specie-specific time each year, but others do so at irregular intervals Borchert The tropical climate could cause multimodal peaks of leaf litterfall in mangroves in this region. This is the first report of net primary productivity of the Sundarbans Mangrove forest, Bangladesh.
The present stand had above-ground biomass of The present value of NPP was higher than those reported for R. The study area is located in the oligohaline zone of the Sundarbans mangrove forest and the area is flushed frequently by tides that may cause higher NPP of this mangroves.
Similar findings were observed by Day et al. There are three ecological zones in the Sundarbans such as oligohaline, mesohaline, and polyhaline zone based on the degree of salinity and floristic composition. The floristics composition of Sundarbans is defined by the distribution of three species: H.
All three species occur throughout the Sundarbans but in different proportions depending on salinity. Depending on the site of mangroves along the salinity gradient of an estuary and with distance inland from the shore, the properties of mangrove communities vary within an environmental setting Chen and Twilley So in the present study, mangrove communities in the oligohaline zone may have higher productivity and turnover than other ecological zones of Sundarbans, Bangladesh. When comparing our estimated rates of litterfall and biomass increment both in AGB and BGB, it becomes evident that litterfall production only amount up to NPP of the mangrove forest along the oligohaline zone of Sundarbans, Bangladesh, is conservative and the estimation was lower because we do not have data regarding coarse root and fine root production and their contribution is not included.
As well as we do not have any data regarding vegetative damage including leaf and reproductive organs by direct consumption of the herbivory animals. Our results agree with the summarization of Teas , who reported that the assumption of total AGNPP for mangroves is three times as large as the amount of total litterfall.
It is not possible to clearly determine how much difference there are in the production of mangrove forests among different studies, due to differences in methodology, inter-annual variation, site condition, and stage of mangrove development. Moreover, there is no standard technique to compare the production capability of the mangrove stands all over the world. The unique characteristics of the Sundarbans mangrove forest also provide important information to decision makers on the strategy for sustainable management of the mangrove forests.
Bangladesh J Bot — Article Google Scholar. Aquat Bot — Water use in relation to growth, carbon partitioning, and salt balance. Aust J Plant Physiol — Blasco F Outlines of ecology, botany and forestry of the mangals of the Indian subcontinent. In: Chapman VJ ed Wet coastal ecosystems, ecosystems of the world, vol 1. Elsevier, Amsterdam, pp — Google Scholar. Borchert R The phenology of tropical trees.
Accessed 18 May Wetlands — Oecologia — Ecol Lett —
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