Raymond
L. Lindeman 1942
The
Trophic-Dynamic Aspect of Ecology
In this work Lindeman studies the food-cycle relationships
of aquatic systems and tries to describe the dynamics of trophic levels as the
ecosystem passes through the phases of community succession. He starts off by discussing
the term and concept of ecosystem and its importance or relevance in ecology in
understanding the processes of nature. Lindeman
makes the point that ecology is dynamic and it is arbitrary and unnatural to
create distinct lines that distinguish the living biotic community from the
non-living environment because doing so forces a biological emphasis on basic
functional organization like the organic-inorganic cycle of nutritive substance
that is so completely integrated that biotic and abiotic components are not
clearly separate. This idea emphasizes the term and concept of ecosystem as
described by Arthur Tansley in 1935 where the whole system of biotic and
environmental factors be considered together rather than separately.
Trophic
Dynamics
Lindeman
defines the basic process of trophic dynamics as the transfer of energy from
one part of the ecosystem to another. It
begins with the assimilation of sun energy into the structures of living
organisms via photosynthesis (primary producers). Primary consumers then feed
directly on plant material while secondary consumers feed on primary consumers,
etc. Saprophytes feeding on dead material, particularly specialized
decomposers, transform organic substances into an inorganic state making
nutrients available for autotrophic plants and thus completing the cycle.
Lindeman concerns himself with the quantitative measurement of productivity and
efficiency for each trophic level. Productivity is defined as the rate of production
which is typically measured in terms of annual yield, a value which must then
be corrected for respiration, predation, and post-mortem decomposition. Next Lindeman addresses the issue of
biological efficiency – trophic level efficiency with respect to lower levels. As
a result he identifies two fundamental trophic principles:
1.
Percentage loss of energy due to respiration is
progressively greater for higher levels in the food cycle because they expend
more energy to acquire their food.
2.
Consumers at progressively higher levels in the
food cycle are progressively more efficient in the use of their food supply
because the increased activity of predators considerably increases the chances
of encountering suitable prey.
In conclusion, the increased respiration and efficiency with
each successive level of predator appears to be important in restricting the
number of trophic levels in a food cycle as pointed out by Elton 1927 that food
cycles rarely have more than 5 trophic levels.
Eltonian
Pyramid
The Eltonian
pyramid describes the general relationships of higher trophic levels to one
another and to community structure where the number and size of animals in an ecosystem
follow a pattern. The animals at the base of the food chain are relatively
abundant while those toward the peak are progressively fewer in number. This is
explained by the fact that abundances of organisms in lower trophic levels must
be adequate to support predation by the next level up and still maintain
existence.
Trophic-Dynamics
in Succession
Lindeman
tries to describe how trophic level interactions, specifically productivity,
change over the course of hydrarch succession (Figure 3.) He mentions that
typically there is a high rate of productivity at first which then slows over
time until a climax state is reached. He also recognizes that there may be
stages of succession that remain unchanged for long periods of time
representing a pseudo climax or equilibrium state. Lastly, progressive
efficiencies of consumer levels seem to increase throughout the aquatic phases
of succession but this is an areas that deserves more study.
Questions
1.
Is productivity for a given trophic level still quantified
in the same way today? Do we still try to quantify efficiency?
2.
Do both trophic principles as presented by
Lindeman still hold today?
3.
What kind of trophic dynamics have been observed
in terrestrial ecosystem succession with respect to productivity and
efficiency?
Lindeman presents his trophic-dynamic theory as taking into account Clements' view (static) and Gleason's view (successional), while introducing the analysis of quantifiable energy transfer within the context of an ecosystem. Lindeman's ecosystem seems as though it is a powerful conceptual tool when compared with the previous, more limited ideas of biological communities, since it includes everything in an area, and can be any size.
ReplyDeleteIn Lindemann's discussion of the ratio of respiration to growth in predators, It is surprising that based on studies of five species, he so quickly generalizes to a value of 140% for all aquatic predators. This leads one to wonder what his original data for Cedar Bog Lake were, and how he arrived at units of g-cal/cm^2/year. However, to his credit, he states in his conclusion that his sample sizes are too small for his derived principles to stand on a statistical basis. Kingsland points out that this paper received negative reviews "because it was too theoretical and went far beyond the data available at the time." Despite this, it appears that Lindeman's reasoning was solid: according to Web of Science, The Trophic-Dynamic Aspect of Ecology has been cited 1,283 times.
Lindeman mentions that his definition of efficiency [(lambda-n)(100)/(lambda-m), p. 407] was taken from something Hutchinson wrote in 1942, but does not explain the basis for this. Why multiply by 100?
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ReplyDeleteThe Greek noun "trophe" means "food" or "nourishment." This use goes all the way back to Herodotus.
ReplyDeleteMartina asked: Do both trophic principles as presented by Lindeman still hold today?
ReplyDeleteI think the ideas presented in this article are most definitely still apt today. The idea that energy transfer exists within an ecosystem between the biotic and abiotic components seems to me one of the fundamental pillars of the field of Ecology. I agree with Julie when she said that this is a powerful conceptual tool when we compare it to the past view of a separate, close-circuit ecosystem. The trophic principles presented by Lindeman are still applicable in my mind - the African savannah popped up in my head as the perfect example for this. Predators (lions, cheetahs, etc.) do expend more energy to obtain their food, but have to feed much less often than an antelope, which spends the majority of its time grazing and taking in a small but constant energy source. This ties into his second principle as well.
This also makes me wonder where Lindeman would think allometry (body size scale) fits into his study. For example, would he take into account that while elephants have some of the largest terrestrial bodies, they are not necessarily considered a predator? Where would they fit into his trophic scale? The amount of energy they expend searching for food is pretty high, just because they need much more to satisfy their energy needs.
At least when looking at vertebrates, I can't think of a single example through time where the largest organism was not an herbivore (late Permian maybe?). I would imagine this has to have something to do with morphology and the need to chase down and over power prey... at some point you get too big to hide, and can't effectively stalk anything, which, coincidentally is a great strategy for herbivores, as at some point you get too big to be eaten by anything.
DeletePoint being, regardless of body size, your carnivores are still expending more energy into getting food than even the largest herbivores. Even when you look at potentially very large scavengers (ie, Tyrannosaurs), those animals are still having to traverse massive ranges to find food to scavenge, and moving that much animal around for a half-eaten carcass is not particularly energy-efficient.
This paper is laying the foundations for the concepts of dynamic flow of energy in plant and animal assemblages. One of the main contributions was to explain the important role of trophic functions. The approach that he used was very quantitative, stressing the effects of succession in structuring the plant and animal communities.
ReplyDeleteThis paper looks at how energy flows through trophic levels ecosystems. It explains that there is no clear line between the biotic and abiotic communities. It uses Cedar Creek Bog as a model, a senescent lake. It explains that lakes increase in productivity and efficiency until reaching “eutrophic stage equilibrium” and then slowly decline as the lake ages to increase again in productivity as the former lake becomes a terrestrial environment. In this way Lindeman uses energy flow and transfer to show how an ecosystem changes over time. As mentioned in a previous post this paper gave new concepts of how ecosystems function and has been cited numerous times, despite early negative reviews delaying its publication.
ReplyDeleteI found these early stages in his development very interesting, his paper was rejected for reasons of theoretical illegitimacy. The referees stated that the paper was "without sufficient evidence and premature and therefore not suitable for ecology." I find this interesting because his ideas seem to be so advanced. I guess this goes to show you that predecessors, although very knowledgable in their field, can be intolerant of new ideas if they are not open to change.
DeleteLindeman manuscript used quantitative data, tropic principles, and succession to develop his ideas on the “tropic-dynamic aspect of ecology”. I agree with Julie that Lindeman concepts were spot on, but his quantitative methods and statistical significance were sub-par by our modern standards. Unlike his predecessors, Lindeman connected the abiotic and biotic factors of the lake into an “integrated system.” Conceptually, Lindeman was progressive in connecting various ideas into a cohesive manuscript.
ReplyDeleteThis contribution by Lindeman is impressive and impactful as it seems to have set the framework fro the way we currently understand trophic dynamics. I don't know enough (or recall enough from my undergrad ecology courses) to say if we quantify trophic dynamics in the sam way today but its clear that the broader implications presented therein hold there own today. This is all the more impressive given Lindeman's short career.
ReplyDeleteThis conclusion of the foundational papers really indicated the progression of writing in ecology. The paper compiles a satisfactory and thorough account of trophic dynamics that begins to set the bar for the standard of scientific writing.
ReplyDeleteExactly! This paper really looks like a modern ecology paper and is also representative of some of the science that gets turned into pop science. I have read numerous accounts that reflect this idea of trophic levels in food ecology and energy transfer from one level to another. It is cool to see something that is so well represented today in the non-scientific community.
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