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Plant Ecology Text

i. the Science of Ecology

Geologic Timeline
(data downloaded 14 Feb 2011 from
San Diego Natural History Museum)
TIME years BP Climate
Holocene Epoch present warming
Arctic & Antarctic ice
Pleistocene Epoch 10K glaciers retreating
18K global warming begins
1.8M the “Great IceAge” [4]
Pliocene Epoch 1.8M cooling continues
Miocene Epoch 5M global cooling
Antarctic ice sheet forms
Oligocene Epoch 24M generally temperate
Antarctic glaciers begin
Eocene Epoch 34M subtropical
Paleocene Epoch 55M cooling begins
Cretaceous Period 65M generally warm
poles ice free
Jurassic Period 144M subtropical
Triassic Period 206M warming
Permian Period 248M glaciation [3]
Carboniferous Period 290M Southern glaciers
global cooling
Devonian Period 354M warm
Silurian Period 417M global warming
Ordovician Period 443M glacial [2]
Cambrian Period 490M generally mild
Proterozoic Eon 540M late: “Ice House” World [1]
or “Snow Ball” Earth
Archean Eon 2.5B ?
Hadean (Azoic) Eon 3.9B n/a
Earth forms

You have probably already heard that there is some concern about Global Climate Change. The issue is controversial, especially outside the realm of Science. There are those who believe that the future of Human endeavors as we know them depend on our ability to mitigate the effects of climate change, while others believe that the issue is little more than scare tactics. The simplest reality is that the climate change does occur, and is occurring as you read these words. However, this is not a “new” phenomenon; Global Climate Change has been part of the natural world for long as there has been Life on Earth. In the geologic history of the Earth, there have been at least 4 global Ice Ages, separated by global Warm Ages. The first Ice Age was from 850 to 635 million years B.P. [Before Present, although most references now use “B.C.E.”, Before Current Era], the second from 460 to 430 million years B.P., the third from 350 to 250 million years B.P., and the last from 1.3 million to 12 thousand years B.P. A few decades ago, there was speculation that the Pleistocene glacial period is not over because it was the shortest (by far) of the 4 glacial periods (the first three lasted 215 million years, 30 million years, and 100 million years, respectively; while the Pleistocene lasted less than 1.3 million years). If the Pleistocene has not yet ended, we could expect the glaciers to return “soon” [any time within the next 12,000 years]. On the other hand, if Human-caused climate change is occurring, we could expect our survival as a species may be at risk in the “near” future [again any time within the next 12,000 years or so].
    It was during the global warming after the Silurian Ice Age when living organisms moved from the oceans onto the land for the first time in geologic history, and it was during the Permian Ice Age when the greatest mass extinction event took place, so it is clear that climate change is important to ecosystems. Since the integrity of ecosystems is generally considered to be of great importance to Humans, it would be useful to us to have some understanding of how natural ecosystems respond to global climate change. This understanding would allow us to anticipate how ecosystems will change, and what we might be able to do in response to maximize the survival of Civilization. I hope, with this book, to lay the foundation upon which such an understanding can be built.

Traditionally, we begin all introductory science texts with a description of the Methods of Science. Although my teaching philosophy is non-traditional, I see no purpose to be served by skipping the introduction to the Methods of [good] Science.

General characteristics of Science:

Anyone who has ever picked up a document written by a scientist has quickly discovered that scientists use a large amount of “jargon.” The intent is not to confuse the beginning scientists, nor the non-scientist readers, but to impose a degree of precision on our usage of the terminology. This works only so long as we provide sufficient definitions of our terms. Throughout this text, the first use of jargon will appear in this font, and will be followed in text with “the definition in this font”. I define jargon to be “any word which will be used in a restricted sense, including common words with broader meanings as well as words made up by my colleagues”. These can also be found in the Glossary.
    In a broader context, any discussion will communicate its meaning better when the participants agree on the definitions of words. This is best achieved by reporting the intended definitions of key words to the participants in the discussion. In a sense, then, I am taking the advice of Humpty Dumpty: “'When I use a word,' Humpty Dumpty said in rather a scornful tone, 'it means just what I choose it to mean – neither more nor less'” (Carroll, Lewis. Alice's Adventures in Wonderland and Through the Looking Glass. Western Publishing Co (Whitman), Racine, WI, 1970. p 164). This would seem to lead to a form of linguistic anarchy; however, this also provides a means by which we can assure that all participants in the discussion are in agreement as to the meaning attached to each key word. The writer or speaker retains the opportunity to use words to mean just what he chooses them to mean, but he is obligated to publish his chosen meaning to the reader or listener. The more precisely the writer chooses to define his terms (and to publish his definitions), the more accurately the reader can understand the intended meaning of the information stream provided.
    This obligates me to define fact as “anything which is observable, either directly or indirectly.” In this context “observable” does not mean that I personally must observe the fact, but allows me to accept the fact as observed by any reliable observer. To observe ‘directly’ is generally understood to mean using any combination of the five senses (sight, hearing, touch, smell, taste). [The standard Chemistry course warning not to use taste applies here too; too many things in the natural world are poisonous -“all natural,” but still poisonous.] To observe ‘indirectly’ is to use some technology between the observer and that which is being observed. For example, animals can be ‘seen’ at night using night vision goggles to extend sight into infra-red wavelengths which the Human eye does not see; depth of a lake can be determined by reflecting sound waves off the bottom; speed can be observed by reflecting a radar beam off a moving automobile. It is also generally understood that “generally understood” does not constitute a definition. You should note that my definition of “facts” limits them to a collection of rather boring information.

    However boring my facts may be, they can become interesting [“anything I find to be interesting is inherently interesting, and I intend to discuss it as if you agree that it is interesting”] depending on what we do with them. We should distinquish between qualitative and quantitative facts because we can treat them differently. Qualitative refers to those characteristics of (facts about) things which can be classified into discreet categories, such as {red, orange, yellow, green, blue, purple}, {smooth, rough}, {soft, hard}. [The “curly braces,{},” are the notation for the set of states the fact could exhibit. Quantitative facts are those which can be measured, such as length, weight, volume. The measurements always include the possibility that the values may have a decimal portion; or that the values are continuous rather than discreet. Many qualitative facts could have been observed as quantitative facts (the number of bird species in an Audubon Christmas bird count is another example of a qualitative fact because there can be no decimal portion), and most quantitative facts could have been observed as qualitative facts. As we accumulate facts about a particular thing (object or event), we refer to the facts as data which we define as “a collection of facts”. Since traditional ecology was a strictly outdoor science, we would collect data while the weather cooperated, then when the weather seemed not to encourage going out, we would think about our data… to determine what questions we could ask about the data. More recently (mid 20th Century on), we think about what questions we could ask about ecological systems so we can design a data collection scheme to get the data we ought to need to answer our question(s).

a Scientific Method:

The Scientific Method exists only in Introductory Science texts (and a few advanced textbooks). Otherwise, although we use scientific methods, we do not follow The Scientific Method as an outline of what we do. Science only becomes a formula when we set out to communicate the results of our studies… the scientific journals require that the written documents we create follow their Style Manual. Failure to follow the correct Stlye Manual results in the paper being rejected, or in the editor returning the paper for a ‘re-write.’
    Well done scientific studies begin with a question. Once we have decided what question we want to answer, we guess what the answer to the question ought to be. We call our guess the hypothesis [defined as “the expected answer to the question under investigation.”] Clearly, if we expect to guess the answer to the question, we should ask only simple questions to which we can guess the answer. We expect that the results of the study will allow us to ask a more difficult question to which we can now guess the answer. This approach is based on a quote from Einstein: an interviewer is said to have asked Einstein how he could come up with the answer to such difficult questions. He supposedly answered, “I don't. I ask simpler questions.” It becomes more important that we ask the simpler questions because our answer is expected to include a prediction of some observable event which will occur if the conditions are met, and this event can not occur if the conditions are not met. This is the standard criterion for a “testable hypothesis,” because it provides for a method for an experiment which is capable of proving the hypothesis to be false. We do not approach our studies with an expectation of actually proving the hypothesis to be true; at best, we can only improve our confidence that the hypothesis may be true.
    Once we know what event ought to occur, we can design an experiment. In one group, called the “experimental group,” the conditions for the hypothesis are met. There is a second group, called the “control group,” in which the conditions for the hypothesis are not met. If the event occurs in the experimental group AND does not occur in the control group, we can state that we have proved our hypothesis to be true (but we understand that this increases our confidence in the hypothesis, but not that it is true). If the event does not occur in the experimental group OR does occur in the control group, we must conclude that our hypothesis has been proven false. Logically, a single instance of a negative result confirms that the hypothesis can not be the correct explanation of the underlying phenomenon, but a single instance of a positive result does not rule out the possibility that the hypothesis is not the correct explanation of the underlying phenomenon. This describes the classic laboratory verification of hypotheses, where the investigator has considerable control over the conditions under which the experiment is conducted. However, in ecology we more often conduct our studies in the field where we have very little control over the conditions under which the experiment is conducted. Unfortunately, there are no clear guidelines for conducting field studies with the same rigor as the scientific community expects from laboratory studies. As a direct result of the difference between the rigor possible in the laboratory and less rigor of field studies, it is more difficult to defend hypotheses about field phenomena.

the History of Ecology

Historical development of Ecology as a science: an excessively brief summary

For Centuries the field of study (Natural History) which ultimately became Ecology was the domain of philosophers (for example, Aristotle, 384 - 322 BCE) or Naturalists. Gradually the number of ‘amateur’ Naturalists working in Natural History field studies increased. Many of the amateurs (including Audubon) recorded very detailed observations and descriptions of Animals and Plants. The main goal was simply to catalog the living organisms of the known World.
    In the 18th Century, Linneaus published his works on taxonomic principles, changing Natural History to a more organized science. Linneaus emphasized that beyond the encyclopedic descriptions of living organisms, it was important to record the habitats and the habits of these creatures. This expanded data laid the ground for later studies to understand how the many species are assembled into larger entities: the community and [later] the ecosystem.
    Around the middle of the 19th Century, Mendel reported his Principles of Inheritance and Darwin reported his Principles of Evolution. Mendel's work was the first hypothesis in Biology to meet the criterion for a scientific Theory by providing both a prediction of events previously not known, and reporting experimental confirmation of the events. Darwin's work, reported as a Theory, did not fully meet the criterion for a scientific theory but is none-the-less generally credited with introducing rigorous science into the field of Natural History. In the first half of the 20th Century, quantitative methods were introduced and the modern science of Ecology began. Not only did the descriptions from Natural History become quantitative, but comparative analyses were undertaken to elucidate the patterns in distribution of living organisms. This led to the development of hypotheses to explain distribution of organisms, and to explain the interactions among the organisms in a given area (community).
    This was followed by a period dominated by laboratory experiments to clarify the mechanisms behind the field interactions among organisms. Attempts were made to move from the laboratory back to the field to manipulate some factors believed to control field distributions and interactions among species. This was followed by a period with computer simulations of ecologial concepts.
    By the turn of the Century (20th to 21st) serious attention was directed toward the formulation of theories. Thus far we have seen mathematical and statistical descriptive models (“model” is another name for Theory, but suggests that it is more simplified than the system being modeled). Descriptive modelling studies allowed the development of interpretive or simulation models. What remains to happen are the predictive models which will support the development of rigorous Theories in Ecology.

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revised: 26 Jan 2011