Proceedings: Alexander von Humboldt’s Natural History Legacy and Its Relevance for Today
2001 Northeastern Naturalist Special Issue 1:57-90
* Geographisches Institut, Universität Kiel, 24089 Kiel, Germany,
ALEXANDER VON HUMBOLDT’S HOLISTIC
WORLD VIEW AND MODERN
INTER- AND TRANSDISCIPLINARY
OTTO FRÄNZLE *
ABSTRACT – The complex subject-matter of the 21st century world presents
an enormous challenge to a discipline-based scientific system. Transdisciplinarity
is demanded; it goes beyond interdisciplinarity and focuses both on the relevance
of research to the problem at hand and on the feasibility of conducting and
implementing it. Problem areas in which different sectors of society and academia
may make effective contributions to include new technologies like genetic engineering,
biotechnologies, energy, mobility, and nutrition; the creation, organization,
and distribution of welfare and resources; human health, age, urban and
regional development, and North-South cooperation; new modes of learning, new
social systems and decision-making processes; and environmental issues like
climate, biodiversity, soil, water, air, recycling, and waste.
Real-world problems determine the kind of action to be taken and not, or at
least to a distinctly lesser degree, the competence or the instruments available at
any given time. Transdisciplinary research adopts an integrative approach to
identifying such problems and working towards solutions. Industry, business,
public administration, non-governmental organizations, and consulting firms all
possess know-how which may be as important to developing new solutions as the
knowledge generated and collected by universities or other scientific institutions.
Thus, transdisciplinarity is a vital means of appropriately confronting many of the
challenges of the present century. It also promises better and quicker solutions at
lower costs, since its value lies not only in its potential for efficiently solving realworld
problems but also in its ability to identify such problems at an early stage.
It is the purpose of the present contribution to show, by way of example,
how Alexander von Humboldt, who received his education in a time when the
modern clear-cut distinction of science and art did not yet exist, aimed at an
inter- and transdisciplinary comprehension of his World, and how his ideas
became implemented in the second half of the past century in the form of
application-oriented long-term ecosystem research.
ALEXANDER VON HUMBOLDT’S HOLISTIC WORLD VIEW
Considering the history of geography from its beginning in classical
antiquity up to the 18th century, a series of brilliant stars stands out quite
clearly: Herodotus, Strabon, Ptolemaios, Sebastian Münster, Bernhard
Varenius, Anton Friedrich Büsching, Georg Forster, and Carl Ritter
58 Northeastern Naturalist Special Issue 1
(Beck 1982). When we ask what distinguished Humboldt from these master-
minds one answer is clear: none of them had tried to understand the
Earth or parts of it in their structural diversity and the complexity of biotic
and abiotic interrelationships, nor did they include an impressive variety
of societal aspects, as did Humboldt in his double capacity as an explorer
and a geographer.
The Roots of Alexander von Humboldt’s Holism
While other contributions to the present Symposium have dealt in
greater detail with Humboldt’s biography, the emphasis now is on of the
mainstream of ideas which, together with contacts to leading scientific
personalities of his early years of study, became the backbone of his
holistic world view.
Humboldt, who had been urged to study cameralistics at the Frankfurt/
Oder University, considers the visit of the young brilliant Berlin botanist
Carl Ludwig Willdenow in 1788 as the decisive and most important for his
whole life (Biermann and Lange 1969). The desire to accompany
Willdenow on a scientific mission grew, and for preparation purposes
Humboldt read “all available floristic literature on both Indies, i.e. the
West and East Indies.” It should be noted in the light of present-day usage
that in Humboldt’s time the notion “West Indies” meant the whole of the
New World, and the tropical Americas in particular. A year later this
longing for the tropics was still intensified by Georg Forster, whose
acquaintance Humboldt made at Mainz in 1789, and whom he accompanied
from March to July 1790 to Holland, England, and France.
Back in Berlin, Humboldt managed to obtain permission for studying
engineering in the oldest mining college of the world, now the
Freiberg Institute of Technology in Saxony. Incorporating the previously
acquired cameralistic knowledge, this paved the way to a brilliant
career in the newly Prussian Margraviate of Ansbach-Bayreuth where
he soon, and also owing to his nobility, became head of the mining
industry, a position which he held with great professional enthusiasm
and considerable social commitment. In addition he found time for
scientific research (A. v. Humboldt 1797), and, what may appear more
important in retrospect, for conceiving three major geoscientific research
The oldest program, dating from 1791/92, focused on a “History of
Plants;” showing that botany has opened Humboldt’s way into the world
of natural sciences, which clearly reflects the lasting influence that
Willdenow had exerted. Willdenow had published an herbal book with a
chapter on the history of plants, which meant in 18th century usage the
attempt to trace the way of plants from their original habitat to the
subsequent areas of cultivation. The second program established the
corroboration of A.G. Werner’s law of strike and dip which is of lesser
2001 O. Fränzle 59
importance in the present context. The third dealt with the development
of a so-called pasigraphy, i.e., a self-explanatory geological semeiotics,
which led Humboldt to the fundamental distinction of hypsometric and
These programs summarize Humboldt’s most ambitious scientific
aims; their importance is reflected in the fact that the pertinent publications
envisioned in all of these fields led him to undertake comprehensive,
comparative field research in different zones of the earth. Thus, in
1793, Humboldt started his unparalleled preparation for travel to the
West Indies, which took him to northern Italy, Switzerland, and Austria,
where he studied tropical plants in the greenhouses of Schönbrunn
Castle, near Vienna, and met explorers who had already visited his
dream-lands. Owing to his diplomatic skill he managed to obtain royal
permission to explore the Hispano-American Colonies, accompanied by
the talented French physician and botanist Aimé Bonpland. It is this
expedition in the years 1799-1804 that personified him as an earth
scientist who combined in a unique way the outstanding qualities of an
enduring, daring explorer with those of a holistic geographer.
Humboldt’s Physical Geography and the Sense of Unity
The above characterization of Humboldt indicates that for him exploring
travels and geography were two necessarily interdependent prerequisites
for a deeper understanding of the world. On the one hand
geographical key-notes made his expedition reports go far beyond a
simple description of the routes followed. On the other, the enormous
experience gained in the New World made his geography realistic and
substantial. Obviously it was important for the conceptual development
of Humboldt’s geography that in 1793 he had already applied systematics
to his “Florae Fribergensis Specimen,” which was derived from the
introduction to Immanuel Kant’s (1802, 1968) “Physical Geography,”
marking an historical turning-point in so far as it moved geography from
its classical incorporation into theological thought in general and
physicotheology in particular (Beck 1982; Hard 1993; Vermij 1991,
1993). Here a complex organization of human experience is defined: (1)
logical in the sense of Linné’s “Systema naturae” (1735), (2) historical,
(3) geographical, i.e., in the sense of spatial differentiation.
Kant’s classification, which implied a principal separation of geography
from history irrespective of manifold links persisting, was transferred
by Humboldt to the sciences of the earth, where he distinguished:
(1) Physiographia (Histoire naturelle descriptive), (2) Historia telluris
(Histoire du globe; closer to position 3 than 1), and (3) Geognosia
(Théorie de la terre, Géographie physique, Physique du monde). Taken
together these three dimensions of a comprehensive approach to a better
understanding of the Earth, which combined both holistic and reduc60
Northeastern Naturalist Special Issue 1
tionist aspects and the experience gained during the six preparatory
years of his expedition, brought about a geographical concentration still
unparalleled many decades later.
At this point, and referring to (3) above, it appears appropriate to add a
few remarks on Humboldt’s equating “Geognosia” to “Erdkunde,”
“Théorie de la terre” or “Géographie physique” and not simply to geography.
The reason is, as an analysis of the “Relation Historique” shows
(Beck 1982), that Humboldt considered himself more as a “physicien”
than as a geographer in the habitual sense of the 18th century, i.e. a
cartographer. Therefore, the term “physical geography” as synonymous
to the terms enumerated above appeared more appropriate to describe the
realm of analytical studies envisioned and the subsequent synthetic presentation
of the results obtained. This type of physical geography includes
consideration of the role of humans in shaping the face of the earth,
which once more reflects Kant’s influence on the evolution of
Humboldt’s notional concepts (Hard 1993). Moreover, it illustrates, furthermore,
that his basic interests were not so much focused on the
discovery of new species and the collection of biotic and abiotic specimens
for banking purposes, as on the evaluative integration of known and
new facts into a science which he finally no longer called “Physik” or
“Theorie der Erde” but almost exclusively “physical geography.”
A comparative analysis of the contemporary scientific literature
indicates that notions like “Théorie de la terre” (Buffon, James Hutton,
J. Forster), “Système de la nature” (Linné, Miraband), “Géographie
physique” (Buffon, Buache, Desmarest, J.R. Forster, Kant), and
“Philosophia naturae” (Linné, A.v. Humboldt) were common property
of the scientific community. All of its leading representatives were in
fact less interested in detailed generic analyses or unravelling specific
microscale causalities, which became the explicit program of the socalled
“organismic physics” of the 19th century (Fränzle 1998a, Markl
1995), but aimed primarily at defining interrelationships. At the same
time it is an interesting illustration of continuing physico-theological
thought that Linné saw many ecological relationships, e.g., food webs,
in the light of Divine Providence and consequently described them as
“oeconomia divina.” In the case of the majority of the above scientists,
who preferred to speak of an “oeconomia naturae,” the basic world view
and orientation of work was the same.
Strangely enough, the fact that Humboldt began his great report on
the 1799-1804 expedition with the “Essai sur la géographie des
plantes” passed largely unnoticed. In the conceptual context of physical
geography which had emerged out of the common ground of European
Enlightenment, one reason is that Humboldt wanted to present an
expression of the results obtained (Beck 1982). The other reason,
equally important when speaking about Humboldt’s holistic world
2001 O. Fränzle 61
view, is deeply rooted in the fact that the 18th century had no clear
distinction between art and science, as is the case in our time. On the
contrary, it was a generally held belief that sciences were to reveal new
phenomena to the artist, and to painters in particular, who were attributed
with the ability to bring about the best and immediately comprehensible
representation of nature (Trepl 1987). In the realm of science
this unifying world view led to an emphasis on physiognomy, in particular
with regard to man, plants, landscapes, and not least in landscape
gardening (e.g., Bonnet 1764, Chambers 1772, Dezallier
d’Argenville 1760, Hirschfeld 1779-85, Lavater 1775-78; see also
Goethe’s “Urpflanze” and “Urphänomene” 1949).
Physiognomy became the model concept for proceeding from the
visible qualities of entities to their very essence, i.e., the “substantia” in
the sense of scholastic philosophy. Embedded into this intellectual and
methodological background, Humboldt’s “Physiognomik der
Gewächse” (1806), aiming at the determination of the reciprocal interrelationships
between site qualities and the “physiognomy” of individual
plants, stands, or vegetation complexes, is rightly considered the starting
point of an ecologically oriented plant geography. In view of the farreaching
influence of this masterpiece, it appears that the background to
Humboldt’s decisive break with the predominantly inventorying type of
18th century natural history, as reflected in the “Ideen zu einer
Geographie der Pflanzen” (Humboldt 1807), is basically an estheticoemotional
one. This is best illustrated by a literal quotation from the
famous work Cosmos (1848, p. 22): “General views lead us habitually to
consider each organism as a part of the entire creation, and to recognise
in the plant or the animal, not merely an isolated species, but a form
linked in the chain of being to other forms either living or extinct. They
aid us in comprehending the relations that exist between the most recent
discoveries and those which have prepared the way for them. Although
fixed to one point of space, we eagerly grasp at a knowledge of that
which has been observed in different and far distant regions.” This
sentence reflects Humboldt’s conviction that only by means of a sufficiently
differentiated analysis of the nested structure of reality which
has to be coupled with a synthesizing “word picture,” the type of
comprehensive world view could be achieved which is necessary for
widening the intellectual horizon of man.
In this context, a misunderstanding, or rather a spurious allegation,
should be mentioned which concerns the term “landscape.” In geographical
reasoning, where this term is frequently considered peculiar to
defining the principal objective of analysis, landscape is not infrequently
equated to the “total character of a region,” ascribed to
Humboldt. The analysis of Humboldt’s works shows, however, that he
only refers to the “global impact” that an observer has of a region: “for
62 Northeastern Naturalist Special Issue 1
appropriately describing the physiognomy of the vegetation cover of a
country it is not necessary to specifically refer to taxonomic criteria (as
is the rule in botany) but focus has to be on what determines the global
aspect (Totaleindruck) of a region. The painter, whose artistic sentiment
is of prime importance in this connection, distinguishes in his works, for
instance, pine trees or palm stands from beech stands but not the latter
from other deciduous species” (translated from p. 207 in: Zaunick 1958;
emphasis by the author).
The impressiveness of Humboldt’s ideas, in particular the “word
pictures” he painted of his response to the tropical landscapes in South
America, also had a tangible impact across the North Atlantic. His
works, particularly the English translation of Cosmos that appeared in
1852, were widely read by many of the prominent writers of midcentury
North America, such as Emerson, Thoreau, and the zoologist
Agassiz (Edwards 1999). Humboldt’s emphatic exhortation to artists to
visit the tropics and bring his perception of the grandeur of tropical life
to a northern public bore fruit in the work of the great landscape painter
Frederic Edwin Church. He did follow Humboldt’s footsteps and
brought to an eager public the very unity in diversity of the tropics
which may be seen as the fundamental message of Humboldt’s works.
Church’s epic paintings such as “Heart of the Andes” or “Cotopaxi” had
an extraordinary impact on the thousands who flocked to view them.
Other landscape painters such as Bierstadt and Morau did the same for
the great landscapes of the North American West. They contributed
considerably to arousing public awareness of these marvels of nature,
which in turn played its part in the politics leading to the creation of the
first national parks in the world, in North America. Thus, Yellowstone,
Sequoia, and Yosemite National Parks owe their preservation at least in
part to the impact of Humboldt and his writings.
In summary, it can be said that Humboldt’s enthusiastic zeal for a
comprehensive understanding of nature by way of comparative analyses
of its complex structures with their bewildering number of static and
functional interrelationships was deeply rooted in his artistic genius.
Science appears as a necessary element of aesthetics, and thus the
demonstration of causalities or propensities by means of pertinent indicative
phenomena was seen analogous to the revelation of the spiritual
substance of a material entity. In the sense of Popper’s (1959) wellknown
notional distinction, Humboldt appears more as a representative
of the first type of holism, i.e., the artist’s view of the world. However,
when analyzing interrelationships in the sense of functional networks,
Humboldt basically tried to practice a holism of the second type, which
established the basis for modern science in general and ecology in
particular. It is characterized by defining the objectives of research in
terms of open systems, i.e., sets of elements in dynamic interaction,
2001 O. Fränzle 63
exchanging energy, matter, and information with their environment,
presenting import and export, building-up and breaking-down of their
material components (Bertalanffy 1968).
ECOSYSTEM STUDIES AND THEORY BUILDING
Of Humboldt’s many profound legacies to science and art, perhaps
the greatest was his sense of unity within the complexity of what we
now call ecosystems. Clearly the ecosystem concept has been fundamental
in the development of modern ecology, although its history
shows that ecologists did not share a common understanding of this
concept (Fränzle 1998, Golley 1993, Jax et al. 1992, McIntosh, 1985).
Definitions involve basic assumptions on the “nature” or properties of
ecosystems which occur in different combinations and thus account for
differences among the definitions:
• ecosystems are1 delimitable in space and time (e.g., Odum 1971,
Rowe 1961, Streit 1980, Stöcker 1979)
• ecosystems are mental constructs of the observer (e.g., Stöcker 1979,
• ecosystems are real entities of nature (e.g., Leser 1984, Odum 1971)
• ecosystems consist of interdependent components such as organisms
and abiotic elements (e.g., Ellenberg et al. 1986, O’Neill et al. 1986)
• ecosystems are in a state of dynamic equilibrium or evolve towards
equilibrium (e.g., Jørgensen et al. 1992)
• ecosystems are self-regulating (cybernetic) systems (e.g., Odum
1981, Patten and Salthe 1985)
The purpose of this section is to outline the role of ecosystem
research in the sequential refinement of ecosystem theories as reflected
in model building. It ranges from empirical models for practical purposes
to rather abstract ones, aiming at qualitative general insights. At
one end of this spectrum are detailed and mechanistic descriptions of
specific systems such as soil horizons or precisely defined soils interacting
with one or a few pure chemicals in aqueous solutions. At the
opposite end of the spectrum are relatively general models which must
sacrifice numerical precision for the sake of general principles. Such
conceptual models need not correspond in detail to any single “real
world” process, but aim to provide a framework for the discussion of
broad classes of phenomena or simply of contentious issues. Rationally
handled, these different approaches mutually reinforce each other, thus
providing reciprocally new and deeper insights.
To illustrate this, an exemplary summary of ecosystem research
orientations is presented in the framework of the International Biological
Program (IBP) and UNESCO’s Man and the Biosphere Program
1 for the sake of brevity “are” always stands for “are considered as being...”
64 Northeastern Naturalist Special Issue 1
(MAB). This is followed by a detailed description of Ecosystem Research
in the Bornhöved Lake District in Germany as a MAB pilot
project. Next, focal aspects of current theoretical reflections on evolution,
structure, and stability of ecosystems are demonstrated on the basis
of inquiries into tropical rainforest stands, which had been a favorite
topic of Humboldt’s research.
Ecosystem Research in the Framework of IBP and MAB Programs
The history of systems ecology illustrates the emergence of favorite
orientations and foci of ecological interest as the result of an increasingly
intensive feedback between theoretical reflection or modelling
and theory-based interdisciplinary ecosystem research. By the mid-
1960s teams of researchers studied whole forests or lakes, while individual
scientists focused on processes within systems, such as rates of
primary production, material and energy transfers between trophic levels
and populations, and the ways and rates of organic decomposition.
Since only a largely unorganized body of theory was available at the
time to stimulate research, ecosystems were viewed from a variety of
perspectives, and frequently researchers reasoned analogically from
physical, chemical, or biological systems to ecosystems (Fränzle 1998a,
Golley 1993, McIntosh 1985). Thus, ecosystem theory was constructed
from field natural history (Trepl 1987) or the type of physical geography
conceived by Humboldt, from thermodynamics, from evolutionary
theory, from information theory, and so on. As a consequence, part of
the ecological community considered systems theory as the most appropriate
paradigm to organize the information about ecosystems, since this
approach provides definitions and general rules which allow very complex
structures to be understood and predicted (Bertalanffy 1968).
When allied to mathematical modeling techniques, system theory provides
the conceptual framework for a highly effective general approach
to the study of ecosystems.
It ensues from the preceding summary of assumptions underlying
definitions of ecosystems that all of them contain, at least implicitly,
certain definitions of structure, order, complexity, or the like. These
definitions presuppose, therefore, the existence of interrelated parts or
system variables. Parts or elements can be defined qualitatively, variables
quantitatively. Since a system is also characterized by function or
activity, it is possible to ascribe function to the elements as well as to the
relations connecting them; function is thus channeled and guided by the
relations. By depending on these relationships (permanent or transient,
weak or strong, etc.), certain alternatives of activity can be defined in a
space of possibilities and actualities; this involves constraints (e.g.,
boundary conditions) that must become or be made manifest. Thus an Sstructure,
dealing with the invariant couplings between the elements
2001 O. Fränzle 65
may be discerned from the P-structure, denoting the temporal behaviour
or activity (Locker 1973).
This problem of identifying parameters must be subsumed under the
more general task of recognizing systems organization which is created
by additional specifications, including recourse to specific theories of
biology, geosciences, etc. It has been proposed, quite correctly and not
only on the basis of a conventionalist attitude to reality, that order is a
projection of the observer and its extent evidently depends on the
subtlety of the description applied (Bennett and Chorley 1978,
Waddington 1977). The balance between simplicity and complexity
which would be both epistomologically trivial in their extreme forms, is
determined by optimization considerations (e.g., with regard to stability
or resilience problems). In regard to the former, a distinction between
local, global, and structural stability is indicated. Local stability, or
stability in the vicinity of an equilibrium point, describes the tendency
of a community to return to its original state when subjected to a minor
perturbation. Global stability describes this tendency when the community
is subjected to a major disturbance. This involves an appropriate
recognition of the fact that real-world environments are uncertain and
stochastic, which means that the corresponding environmental parameters
in the model equations exhibit random fluctuations (Begon et al.
1990, Gigon 1983, van der Maarel 1976). This leads to a yet more
general meaning of stability, termed structural stability, which refers
to the qualitative effects upon solutions of the model equations which
are due to gradual variations in the model parameters. Thus, a system
may be considered structurally stable if these solutions change in a
continuous manner. Conversely, a system is structurally unstable if
gradual changes in the system parameters (e.g., alterations in site factors
of a community) produce qualitatively discontinuous effects (Fränzle
1993, Jørgensen 1990, van der Maarel 1976).
The International Biological Program
In practice, the application of the systems paradigm resulted in two
complementary approaches, the first of which was characterized by
ecosystem modeling from information about system components and
linkages. The other, pioneered by Odum (1957) at Silver Springs, considered
the ecosystem from the perspective of an object of research
whose input-output relationships had to be determined in order to
mechanistically explain the conversion of inputs into outputs by the
system. The opportunity to test and further develop these alternatives
was the primary research area of the International Biological Program
(IBP) which had an overall focus on biological productivity as a basis
for human well-being. Ultimately, it developed into a largely ecological
66 Northeastern Naturalist Special Issue 1
program, as the scientific director of the IBP, Worthington (1975, p. 64),
stated in the synthesis volume:
“It is this ecosystem approach which distinguishes much of the IBP
research from what had dominated ecology before. Essentially it consists
of the careful selection of a number of variables — biological,
chemical and physical — about which data are collected, quantitatively
as well as qualitatively. Thereby the ecosystem can be analyzed in order
to ascertain which factors and processes are important in causing the
dynamics of the whole. In this, the application of system analysis to
biological systems has been one of the major innovations developed
As regards terrestrial productivity, in the U.S.A. the program proposal
was to study “landscapes as ecosystems,” with emphasis on production
and trophic structure, energy flow pathways, limiting factors,
biogeochemical cycling, and species diversity. An important feature
was not to confine these studies to natural areas only; another was to use
systems analysis as a mechanism for integrating the results of a study. In
a comparative evaluation of the pertinent biome projects organized in
the grasslands, tundra, deserts, coniferous forests, and deciduous forests,
a critical American ecologist came to the conclusion that they
furthered ecological knowledge but failed to contribute to the development
of ecosystem theory: “The programs were not designed to sort out
competing or contradictory ideas. Rather, they were driven, at least
initially, by the idea that ecologists could construct a mechanical systems
model built on the concepts of trophic levels, the food web, or the
food cycle, and then represent the dynamic behaviour of the components
by data from organisms or populations that are surrogates of the component.
This ‘bottom-up’ or ‘design-up’ approach did not prove possible
or useful. Further, the biome projects did not effectively promote landscape
ecology, as Odum had hoped. The biome was the setting for site
research but was not really addressed as such in an effective manner”
(Golley 1993, p. 139).
In comparison to the U.S. biome studies, the German IBP project,
located in the Solling Mountains, was organized in a way similar to
the Hubbard Brook project, located in the White Mountains of New
Hampshire (Likens et al. 1977). Both approached ecosystem analyses
from the components which could then be linked together systematically
in a model-based theory or as a natural object (in Popper’s 1959
sense) studied by means of conventional scientific methods. Like the
Hubbard Brook investigations, the Solling project also took a landscape
approach from the beginning, based on an apriori ecological
knowledge of the area which probably exceeded that in most other
places where IBP research was undertaken. It focussed in a comparative
way on natural-like ecosystems, nature-resembling ecosystems,
2001 O. Fränzle 67
transformed ecosystems, and degraded systems. To this end, the study
sites included acidophilous beech forest and planted spruce forest
stands at several different ages, along with permanent grassland and
cultivated fields. Research proceeded from a description of climate
and soils and the abundance and productivity of vegetation, animals,
and microorganisms, to plant physiology, nutrient fluxes, and energetics
(Ellenberg et al. 1986).
In comparison to the majority of national IBP programs which
focused on a single question or a few questions at best, and in comparison
to studies undertaken in technologically advanced countries which
mostly dealt with natural ecosystems, the Solling project was exceptionally
successful. It provided a wealth of sound data on ecosystem
structure and function, thus building the scientific concept of the ecosystem.
Furthermore, it formed a promising basis to reason about the
causes of forest dieback which was considered a serious problem in
Germany in the 1980s. Unlike the biome programs of the United States,
however, the final summary report of the Solling project did not attempt
to force the results into a single synthesis on the basis of an
abstract theoretical device or a model. Instead, each part was placed
with a site-specific conceptual ecosystem model and developed a
theme within its own logic. Owing to this methodology, the Solling
project is rightly considered a milestone in the development of a
theory-based ecosystem research.
Both the conceptual framework and the practical experience gained
in interdisciplinary research exerted a considerable influence on the
conception of a comprehensive ecological surveillance system for Germany
(Ellenberg et al. 1978). Composed of three interrelated components,
namely an ecological monitoring network, comparative ecosystem
research, and an environmental specimen bank, it is intended and
largely implemented in Germany to promote both theoretical ecology
and, in a transdisciplinary context, planning and policy. The integrative
ecosystem research component of this German program has become an
essential part of UNESCO’s Man and the Biosphere (MAB) Program
which was developed out of the IBP experience. In the following section
this will be considered in regard to its bearing on ecosystem research,
theory, and modeling.
Man and the Biosphere (MAB) Program
The general objective of the MAB program, as launched by
UNESCO in November 1971, endorsed by the UN Conference on the
Human Environment (1972), and supplemented in 1986 and 1992, has
been defined as: “... to develop within the natural and social sciences a
basis for the rational use and conservation of the resources of the
biosphere and for the improvement of the relationship between man and
68 Northeastern Naturalist Special Issue 1
the environment; to predict the consequences of today’s actions on
tomorrow’s world and thereby to increase man’s ability to manage
efficiently the natural resources of the biosphere” (Unesco 1998). The
specific aims of the program are:
• To assess the changes within ecosystems resulting from man’s activities
and the effects of these changes on man.
• To study and compare the structure, functioning, and dynamics of
natural and modified ecosystems.
• To study and compare the dynamic inter-relationships between “natural”
ecosystems and socio-economic processes and especially the
impact of changes in human populations, settlement patterns, and
technology on these systems.
• To define scientific criteria as a basis for rational management of
• To establish standard methods for acquiring and processing environmental
• To promote the development of simulation and other techniques of
prediction as tools for environmental management.
• To foster environmental education in its broadest sense and encourage
the idea of man’s responsibility for and personal fulfilment in partnership
The MAB Program consists of fourteen international project areas
which include the main ecological systems and physiographical units:
tropical forests, mediterranean-type and temperate forests, grazing
lands (savanna, grasslands, etc.), arid and semi-arid zones, lakes,
marshes, rivers, deltas, estuaries and coastal zones, mountain and tundra
lands, and island ecosystems. Man-made as opposed to natural ecosystems
and man’s use or abuse of energy are also covered, as are four
major fields of human activity or interaction with the biosphere: conservation
of natural areas, effects of pesticides and fertilizers, major engineering
works, and genetic and demographic changes.
Ecosystem Research in the Bornhöved Lake District
In the sense of methodology by example, a short description of the
MAB pilot project “Ecosystem Research in the Bornhöved Lake District
(Northern Germany)” illustrates the relevant approaches in the framework
of this international program.
The Bornhöved Lake District (Fig. 1), selected by means of comparative
geostatistics as a core area of the German ecosystem research
network (Fränzle et al. 1987), is situated some 30 km south of Kiel
(Schleswig-Holstein) and covers about 50 km2 in terms of interrelated
drainage basins. It is characterized by moraines of the Weichselian
Pleniglacial with intercalated outwash sediments including kame deposits,
dead-ice depressions with lakes, fens or wetlands, and Late Saalian
moraines in the south. Thus, the assemblage combines the essential
2001 O. Fränzle 69
geomorphic features of northern Germany, which ensures a high degree
of spatial representation in the research results obtained, which is essential
for purposes of extrapolation (Fig. 2).
Owing to the complicated geomorphic history (Fränzle 1981a,
Garniel 1991, Piotrowski 1991, Stephan and Menke 1977), a great
variety of natural ecosystems has evolved in the course of the last
12,000 years. Human impact began in the Late Mesolithic, reached a
first maximum in the first millenium B.C., was minimum in the 7th, 8th,
and 14th centuries A.D., and has increased thereafter to its present-day
maximum (Fränzle 1990, Garbe-Schönberg et al. 1998, Schleuss 1992,
Scholle and Schrautzer 1993). Thus, these ecosystems have faced longand
short-term natural and anthropogenic changes which are quantitatively
identified, on a comparative basis, in terms of basic processes
Figure 1. Core areas of the German MAB Program.
70 Northeastern Naturalist Special Issue 1
such as energy, water, and nutrient cycles in order to improve ecosystem
management. This involves cultivation experiments on arable land and
pastures to define more precisely their susceptibility to different management
practices and environmental chemical impact, comparable investigations
on forest ecosystems and lakes, and the assessment of
agricultural practices with regard to eutrophication and groundwater
resources management. In this context, inquiries into the specific role of
ecotones are particularly important. More specifically they relate to
exchange and filter processes and the influence of ecotone structures on
both stability and resilience of the adjacent aquatic or terrestrial ecosystems,
respectively (Fig 3).
In the framework of the socio-economic orientation of the
Bornhöved Project, questions of environmental perception and economic
expectations among farmers and fishermen, and the resultant
private and public investment behaviour in the light of both national and
international (EU) marketing policies, are also subject to assessment
and modeling approaches (Fig. 4a,b).
Figure 2. Saalian and Weichselian Glaciations in northern Germany (adapted
from Ehlers 1983).
2001 O. Fränzle 71
Thus the general aims of the Bornhöved Project are:
• defining and modelling structure, dynamics, and stability conditions
of the interrelated terrestrial and aquatic ecosystems of the study area
in terms of site characteristics and biocenotic diversity, natural and
anthropogenic fluxes of energy and matter, productivity, and land use
• determining and modeling environmental strains and resilience
mechanisms of the ecosystem compartments affected by disturbances
with particular reference to chemical impacts.
In view of the specific structure of the study area, particular objectives
of research are:
• modeling of biotic, energetic, and material exchange processes between
neighbouring ecosystems of different land-use and fishery patterns;
• modeling site-dependent relationships between lakes and their drainage
basins with focus on the role of different land/water interfaces;
• modeling of agro and pasture ecosystems in the light of national and
international production and marketing regulations;
• ecotoxicological research on the fate and behaviour of environmental
• inquiries into the efficiency of environmental protection and conservation
• testing the validity of spatial extrapolations of simulation models by
means of comparative site analyses and geographic information systems;
Figure 3. Model of an ecosystem (adapted from Ellenberg et al. 1986).
72 Northeastern Naturalist Special Issue 1
• the paleoecological and historical reconstruction of ecosystem evolution
in the study area since the end of the Weichselian Glaciation.
In greater detail, these objectives are defined in a hierarchically structured
system of several hundred working hypotheses on five levels of
increasing generality which form the conceptual basis of interdisciplinary
cooperation. It has grouped about 140 scientists from the following
disciplines: agricultural management, bacteriology, chemistry, climatology,
computer science, ecotoxicology, geobotany, geomorphology,
human geography, hydrogeology, ichthyology, limnology, mathematics,
meteorology, paleobotany, paleozoology, physical geography,
physics, planktology, plant nutrition, plant physiology, soil microbiology,
soil science, toxicology, and zoology (Fränzle 1990, 1998a; Müller
1992; Müller and Windhorst 1991).
A particularly important type of change studied in the Bornhöved
Project is adaptation, and the influence eliciting it can generally be
considered as a stimulus and the adaptive process as a response, i.e., a
Figure 4 a. Summary of ecological modelling approaches.
2001 O. Fränzle 73
stabilization. In greater detail, the behaviour of an adapting system
can be classified into (1) goalseeking, (2) purposive, and (3) purposeful.
The first adaptative mechanism consists in a one-to-one correspondence
between stimulus and response, while a purposive system displays
a one-to-many correspondence, which means that each stimulus
normally elicits a number of responses. The term “purposeful” finally
indicates an adaptive mechanism which brings about a change in the
Since the system achieves, during the process of adaptation, a new
kind of structural or functional order or organization, it undergoes selforganization.
This process includes not only adaptation per se, but also
cognition and learning with regard to constraints involving energy and
matter. The exergy concept (Jørgensen 1992) is one basis of current
attempts to develop thermodynamically founded models of ecosystem
functioning which may, for example, make it possible to predict how the
biota of an ecosystem might respond to specific environmental changes.
Depending on the ratio of energy inflow to outflow, a nucleation (i.e., a
clustering or aggregation of system elements) may occur. In these clusters,
or regions in geographical terminology, a conversion of energy into
signals is carried out, whereby the activity of the energy converter is
decisive for the signal connectivity which in turn defines the interactions
between elements. This is a principal statement connecting thermodynamics
with information theory (e.g., Patten and Jørgensen 1995).
Figure 4b. Spatio-temporal scales of models used in the framework of the
Bornhöved Ecosystem Research Project (Schleswig-Holstein).
74 Northeastern Naturalist Special Issue 1
Because the regions are characterized by their states, the process of
self-organization can be considered as a transition between these states,
undergoing new formations between the elements, provided the stimuli
exceed certain threshold values. In addition to cybernetics (e.g., de
Angelis 1995, Straskraba 1995), network theory (Higashi and Burns
1991, Patten 1992), catastrophe theory and bifurcation analysis have
proven useful for formalized descriptions of such systems in transition.
Catastrophe theory limits systems of interest to so-called gradient systems
which arise from the minimization of some objective function and
associated dynamics (or maximization of its negative). The latter kind of
branching behaviour is relevant to systems of a more general type than the
first, which cannot be appropriately characterized by the gradient of a
potential function. Typically, differential equations of non-gradient systems
have a small number of isolated stable equilibrium points and
information about system behavior is presented as trajectories on state
space (or phase) diagrams. The stable points act as attractors, and correspondingly
unstable points as repellors, and these points shape the contours
of the trajectories in state space accordingly. Bifurcation is reflected
in the existence of critical parameter values at which the nature of the
solution to the differential equation changes. However, there is no simple
classification of possible “cases” as in catastrophe theory, and empirical
inquiry into systems behaviour is essential to proceed in more precisely
determining the realm of applicability of bifurcation methodology to
generalized ecosystem analysis and modeling.
Inquiries into self-organization processes involve comparative
analyses of community and ecosystem succession and the
chronosequential approach, or space-for-time substitution, is a traditional
tactic applied. As a consequence of the probabilistic character of
living systems, this approach may be misleading. Consequently, longterm
studies were recognized by founders of ecology to be necessary for
a reproducible understanding of succession (see Clements 1916).
Despite the failings of vegetational or soil chronosequences, their
value is clear if certain limits are kept in mind. In the framework of
system evolutionary analyses of holarctic and tropical plant associations,
space-for-time substitution has been employed to assess structural
or compositional aspects (Fränzle 1994). The same applies to old-field
successional studies which document trends in life history types, pathways
of dominant species, convenient “stages,” and regional differences
(Pickett 1989a). Many of these insights could, in principle, have come
from long-term studies. However, the understanding that has emerged
from the few long-term investigations of old-field succession is of a
different sort, since they documented the nature of transitions, the role
of year-specific conditions, the problems with end points, and the role of
newly invaded species in succession (Asshoff 1997, Bobrowski 1982,
2001 O. Fränzle 75
Biodiversity Analyses of Tropical and Holarctic Plant Communities
An important issue of the self-organization paradigm is how
biodiversity relates to community structure and which community-level
properties emerge from the disparate interactions of organisms, populations,
and site qualities. Possible examples of such “emergent properties”
include trophic and guild structures, stability, resilience, and successional
stages. A generalized offshoot of the concept of emergent
properties is the notion that biological systems are hierarchically organized,
with new properties at each level of the hierarchy (Allen and Starr
1982, O’Neill et al. 1986, Solbrig and Nicolis 1991). According to this
view, diversity is better understood if ecosystems or biota are decomposed
hierarchically so that each process can be viewed as a stabilizing
or disruptive factor at each level in a hierarchy of time and space scales.
Such hierarchical organization can be easily visualized or defined
for the level of molecules through organisms where the hierarchies are
nested, i.e., all lower-level hierarchies are included in one higher category.
Species, however, not infrequently are part of more than one
higher community or ecosystem. Thus, a mutation may be detrimental to
the species living in one (adverse) environment but not when it lives in
another. Therefore, the validity of hierarchy theory at the community
and ecosystem levels is more controversial than at distinctly lower
levels of organization.
The following section on biodiversity analyses of tropical and
ectropical plant communities is an attempt to combine viewpoints of
hierarchy theory and thermodynamics of open systems, which leads to
the following hypotheses:
• Species diversity of climactic lowland rainforests is, ceteris paribus, for
negentropic reasons inversely related to the nutrient content of soil.
• Under conditions of long-lasting climatic and geomorphic stability
ecosystem complexity evolves in a non-monotonous way with the
nutrient status of soil. If soils form on basic or intermediate parent
materials, pedogenic nutrient supply and species diversity may both
increase during periods of 1 - 10 (possibly 100) ka, provided the water
and energy factors are not limiting. Shorter fluctuations of variable
but generally decreasing amplitude are likely to be superimposed on
this long-term trend. In the following period of evolution, which can
last several hundred or even thousand ka, soils degrade in regard to
nutrient supply but species diversity keeps increasing for negentropic
Biodiversity and Thermodynamics of Tropical Rainforests
The verification of the first hypothesis is based on the comparative
analysis of diversity and abundance spectra of neo- and paleotropical
rainforest associations and their related soils. McIntosh’s (1967) diver76
Northeastern Naturalist Special Issue 1
sity index is applied, as it appears better suited for comparison with the
literature. The indices of stands 30-62 are derived from primary data
kindly provided by Professor Brünig (Hamburg), the others are based on
species lists from Aubréville (1961), Davis and Richards (1933, 1934),
and Richards (1963). In order to better compare with similar figures in
the literature, it is noted that values in the abscissa are standardized by
introducing a relative abundance parameter Â, defined as number of
species per 100 individual plants (Fig. 5).
Figure 5 clearly shows that in most cases rainforest stands on highly
nutrient-depleted ferralsols, acrisols, and podzols of tropical lowlands
attain diversity indices above 90% of the theoretical maximum. However,
further differentiation according to local nutrient status and water
budget is not possible, given the available data. Stand 38 (Borneo) is of
particular interest since it represents a forest which developed on a
tropical bog. Its exceptionally low index value allows the conjecture
that its nutrient supply has fallen below the critical value defined below.
On a very general level, the apparently unusual inverse relationship
between nutrient status of soils and diversity of related plant communities
may be interpreted in terms of biological thermodynamics
(Prigogine 1976). Biotic communities are open systems in exchange of
energy and matter with their environment; their entropy production, dS,
comprises the terms diS and deS, where diS denotes the entropy produc-
Figure 5. Diversity indices of paleo- and neotropical rainforest stands.
2001 O. Fränzle 77
tion within the system while deS is a flux term describing entropy
“export” into the environment:
dS = diS + deS. (1)
Only diS > 0, but deS can be negative. By identifying entropy with
disorder, it follows from Eq. 1 that an isolated system can only evolve
towards greater disorder. For an open system, however, the “competition”
between deS and diS permits the system, subject to certain boundary
conditions, to adopt new states or structures. These are stationary if
dS = 0 (2.1)
or deS = -diS < 0 , (2.2)
diS can be expressed in terms of thermodynamic “forces,” Xi, and rates
of irreversible phenomena, Ji (Prigogine 1976). Xi may be gradients of
temperature or concentration; the corresponding “rates” are then heat
flux and chemical reaction rate. Hence,
diS n (3)
— = Σ JiXi
Provided the reservoirs of energy and matter in the environment of the
open system are sufficiently large to remain essentially unchanged, the
system can tend to a non-equilibrium stationary state far beyond the
domain of linear thermodynamics. This state may be associated with
dissipative structures (Glansdorff and Prigogine 1971), i.e., structures
resulting from a dissipation of energy rather than from conservative
Considering phytocenoses from the point of view of stationary dissipative
structures, the relationship of diS and deS as expressed in Eq. 2
and the specific boundary conditions controlling entropy production and
flux rates appear to be particularly important. It is a consequence of Eq.
2.2 that, thermodynamically speaking, stability or the capacity to maintain
a non-equilibrium steady state is coupled with a (relative) minimum
of total entropy production dS. Clearly this can be accomplished by
either minimizing diS or maximizing deS, or a combination of both
Concentration processes involved in the normal metabolic activities
of living systems play an important role in this connection, as can be
seen from the following equation.
ΔG° = R·T·ln — , (4)
78 Northeastern Naturalist Special Issue 1
where ΔG° = difference in standard free energy, R = 8.31 J· mol-1 · K-1, T
= temperature in Kelvin, and C2, C1 = higher or lower thermodynamic
concentrations, respectively. Changes in concentration are a physical
prerequisite for the production of a great many compounds, and an
absolutely cogent one if substances are produced whose free energy is
higher than that of the corresponding “raw materials.”
In Amazonia, for example, forest stands with their mosaic-like structure
owing to the patchiness of natural rejuvenation processes, developed
specific adaptations facilitating these concentration processes. A
dense root mat is formed over the soil in intimate contact with litter, and
root tips growing upwards into the fallen litter (Klinge 1983). Mycorrhizal
associations, as the most common plant root-soil microorganism
symbioses, benefit their host plants by effectively increasing the absorptive
surface area of the root system, thus providing for increased uptake
of nutrients (Harley and Smith 1983), and by biological nitrogen fixation
in the root-humus-soil interface (Dommergues et al. 1985; Herrera
et al. 1981; Fittkau 1983, 1991). The dense fabric of predominantly fine
roots also plays an important part in exchange and adsorption of nutrients
from throughfall water. In addition, the structure of the foliage
favors the use of nutrients by a long active life, the retransport of certain
nutrients before leaf shedding, and a high polyphenol content and coriaceous
nature which reduce herbivory. Another factor of high importance
is the multilayered structure of the forest and the activities of epiphytes
and microorganisms on much of the exposed surfaces, which together
form highly efficient filtering systems scavenging nutrients from rainwater.
Research in New Guinea and the Ivory Coast has shown that in
the rainforests approximately two-thirds of the potassium input of about
100 kg / (hectare * year) and one-third of the magnesium input of around
30 kg / (hectare * year) came from rainfall and leaching from tree
crowns. The remainder was due to litter fall (Schultz 1988).
The effectiveness of these negentropic processes is further enhanced
by most efficient entropy fluxes related to the transpiration and nocturnal
respiration of plants. The molal entropy of H2O increases from 63 J x
mol-1 x K-1 (liquid) to 189 J x mol-1 x K-1 (gas) in the course of evaporation,
and CO2 has a molal entropy of no less than 214 J x mol-1 xK-1.
Thus, the reverse process, the photosynthetic fixation of CO2, is also of
comparable importance for the negentropy balance in the light of Eqs.
2.2 and 4.
Even in the simplest cells the normal metabolic pathways imply
several thousand complex chemical reactions which must be coordinated
by means of an extremely complicated functional network; this
means that hierarchical order in both functional and spatio-temporal
respect constitutes a further highly important negentropic factor. It
characterizes every living system from the sub-microscopic level to
2001 O. Fränzle 79
rainforest communities like those of the Amazonian Hylaea which also
comprise extremely diversified faunal assemblages (e.g., 80 ant species
on one tree). The evolution of such a nested system is a multiple-level
process, in which patterns generated at one level determine the evolutionary
dynamics and evolutionary potential at other levels (Hogeweg
1994). It is also a particularly good example of May’s (1972) cybernetic
model of community behaviour after small disturbances, which suggests
that increases in species number lead to lesser stability unless compensatory
decreases occur in the degree of web connectance (i.e., the
fraction of all possible pairs of species interacting directly) or interaction
strength (Fränzle 1998b). Summarizing, it may be said that the
combination of these highly efficient negentropic community structures
and processes is apt to overcompensate the high entropy status of the
related soils as defined in terms of nutrient supply, which brings about
the long-term stability of tropical rainforest ecosystems under the stable
climatic and geomorphic boundary conditions assumed above.
Species richness and site analyses of ectropical plant communities
A verification of the second hypothesis involves a basically analogous
approach with regard to ectropical phytocenoses as the above
diversity and site analyses of tropical lowland rainforest communities.
For the sake of brevity, Figure 2 summarizes the results of comprehensive
cluster (centroid sorting) and regression analyses of 108
phytocenoses from northern Germany, in the form of a matrix defining
the absolute frequencies of stands characterized by N ⊕ M nutrient and
soil moisture contents and H ⊕ Â combinations. It shows that highly
diversified plant communities of medium to low abundance (classes 12-
16) are most frequent on sites characterized by high nutrient but medium
to low soil moisture contents (classes 1-5). Phytocenoses of both high
diversity and abundance (i.e., classes 5-7), however, are relatively rare
on sites of this type (Fränzle 1994).
Thus, at the sub-continental scale, in northern Germany species
diversity tends to increase with pedogenic nutrient supply, and is largely
independent of differences in soil moisture regime. A comparable analysis
of North American plant communities (Fränzle 1981b) permits, at
the continental scale, a more precise definition of the qualitatively wellknown
dependence of plant growth on the water factor. In statistical
terms, the plant-available amount of soil moisture is the major controlling
factor of species richness (Fig. 6).
A triphase model of ecosystem evolution
In conclusion, the inverse species richness/nutrient relationship of
tropical and ectropical plant communities leads to the question of
whether a unifying interpretation of the above results is possible. The
80 Northeastern Naturalist Special Issue 1
affirmative answer can be summarized in form of a triphase evolutionary
model (Fig. 7).
(1) Phase I is characterized by a parallel increase in pedogenic
nutrient supply and species richness owing to accelerated immigration
of plants, provided that water and energy factors are not limiting. Spatial
heterogeneity of sites is reflected in a corresponding variability in
numbers of species and plant individuals. With this variability, plant
associations may simultaneously retain genetic and behavioural types
that can maintain their existence in low populations together with others
which can capitalize on opportunities for dramatic increase. Ecosystems
are consequently characterized by a (comparatively) high resilience but
much lesser stability.
Figure 6. Absolute frequencies of clustered stand characteristics (H ⊕ Â) on
different sites (N ⊕ M).
2001 O. Fränzle 81
(2) Phase II can last for several hundred or even thousand ka; and the
ecosystems as complex hierarchial structures are characterized by
marked soil degradation in terms of nutrient supply on the one hand,
while species richness keeps increasing for negentropic reasons on the
other. The more homogeneous the climatic and edaphic environment in
space and time, the more likely is the macrosystem to display low
overall fluctuations; i.e., its overall stability has attained a maximum,
while resilience is distinctly less than during phase I.
Tropical rainforests represent such buffered and (largely) self-contained
systems with relatively low (natural) variability on highly nutrient
depleted soils of the ferralsol, acrisol, and podzol classes. Temporary and
larger-scale disturbances are likely to affect a proportionally higher
number of species than in phase-I populations, where the interspecific
differences in ecological valence are usually distinctly higher. At a lower
level of the hierarchically differentiated analysis; i.e., in higher spatial
resolution, however, the patchiness of the vegetation cover as a result of
interspersed small-scale rejuvenation processes is an expression of shortterm
localized instabilities out of phase, which efficiently contribute to
enhance the overall long-term stability of the macrosystem.
(3) Phase III marks the eventual and comparatively rapid decrease in
species richness of phytocenoses, once the nutrient status of soil has
fallen below a critical level which can no longer be compensated by the
set of negentropic mechanisms described. Consequently plant communities
may be highly resilient, although unstable.
In the light of this model it seems appropriate to finally restate the
three ecological principles of Thienemann (1956), two of which were
first proposed in 1920 but repeatedly discovered and put forward as new
• The greater the diversity of site conditions, the larger is the number of
species which make up the biotic community.
• The longer a site experiences the same evolutionary conditions, the
richer and more stable becomes its biotic community.
Figure 7. Model of pedogenic nutrient supply and species diversity in the course
of ecosystem evolution.
82 Northeastern Naturalist Special Issue 1
• The more site qualities deviate from normal, and hence from the
normal optima of most species, the smaller is the number of coexisting
species while their abundances are proportionally increased.
The evolutionary model suggested, allows for more precise definition
of the realms of validity of these principles: in the above sequence of
quotation they refer to phase I, II, and III or I populations, respectively.
UNITY IN COMPLEXITY –
QUEST FOR A UNIFIED ECOSYSTEM THEORY
The analysis of real communities with their site characteristics and
the comparative assessment of ecological models have provided a better
insight into their bewildering complexity which clearly fascinated
Humboldt. Population dynamics of real-world ecosystems are spatially
distributed in general, associated with a marked temporal variation,
providing a multitude of ways in which the probability of coexistence is
enhanced and biodiversity increased. Coexistence under stochastic,
non-equilibrium conditions as described by patch-dynamics models at
different scales can be just as strong and stable as that occurring under a
deterministic, niche-differentiation model. In a single patch, species
extinction can occur as a result of competitive exclusion,
overexploitation, and other destabilizing interspecific interactions or
they are due to environmental instability, e.g., unpredictable disturbances
or changes in conditions. In this connection it is worth remembering
that soil conditions are largely controlled by pH and redox
systems. Since both are nonlinear interrelated buffering systems, soil
stability with regard to sorption and mobilization processes is liable to
unpredictable, chaotic changes.
An important parallelism seems to exist between the properties of a
community and the properties of its component populations which will
be subject to a (relatively) high degree of K selection in stable environments;
r selection predominates in variable environments. K-selected
populations with their high competitive capacity, high inherent survivorship
but low reproductive rates, are normally resistant to disturbances.
However, once perturbed they have little possibility to recover,
i.e., low resilience. The r-selected populations, by contrast, have less
resistance but distinctly higher resilience. This inverse relationship between
resistance and resilience is of particular importance in
In conclusion it may be said that most communities are probably
organized by a temporally and spatially varying mixture of “forces,”
namely competition, predation, and disturbances, with competition and
predation being presumably less important in more disturbed environments.
Thus, there is no such thing as a single stability or sensitivity
2001 O. Fränzle 83
measure for a community. Stability varies with the aspect of the community
or ecosystem under study and the nature of the disturbance. Without
pertinent semantic specifications relating to defined temporal and spatial
scales (duration and dimensionality of observations), indicator variables,
and the nature of perturbation, statements about systems stability
and sensitivity would be meaningless in the ecological as in many other
respects (Fränzle 1998b).
This (necessarily incomplete) summary of focal points of ecological
interest may indicate that the present theoretical background to ecosystem
research has not yet reached the level of a comprehensive unified theory.
There exist, however, a commendable number of unifying concepts and
integrative approaches with regard to ecosystem research. Here it may
suffice to quote the following, which not infrequently exhibit a considerable
amount of convergence. Catastrophe theory (Thom 1975, Wilson
1981) concerns both the stability and creation of forms, and each of the
pertinent concepts also implies a general concern with dynamical analysis.
Jørgensen (1992, 1995) introduced the exergy principle and deduced
a theory of ecosystem evolution on this basis. Exergy may be associated
with holistic indicator variables such as entropy, emergy, and ascendency
(Jørgensen 1997 a, b). Schneider and Kay (1994 a, b) identified thermodynamic
non-equilibrium, exergy gradients and flows as equally useful
indicators of ecosystem functioning. Following Odum’s (1969) succession
concept and touching upon cybernetic system analysis, Patten (1998)
ascribed to certain state functions the intrinsic quality of attractors; in
Bossle’s (1992) terminology they constitute ecological orientors or goal
functions (Müller and Leupelt 1998).
Epistemologically speaking, all of these concepts are derived from,
or associated with, systems theories in general and, more specifically,
with theories of self-organizing ecological systems. The latter, in turn,
amalgamate components of the thermodynamic theory of irreversible
processes (Nicolis and Prigogine 1977; Prigogine 1967, 1976, 1985)
with elements of the above catastrophe theory, furthermore with deductions
from the information and network theories (Margalef 1995;
Ulanowicz 1986, 1995), the theory of games (McMurtrie 1975, Pimm
1982, Ulanowicz 1986), and hierarchy theory (Allen and Hoekstra 1992,
Allen and Starr 1982, O’Neill et al. 1986).
One of the most conspicuous representations of self-organization
processes in open systems is the formation of gradients whose structural
and functional analysis provides for a particularly integrative aspect in
ecosystem studies (Fränzle 1994; Müller 1998; Prigogine 1976;
Schneider and Kay 1994 a, b). In an open system the “competition”
between internal entropy production and entropy “export” into the environment
permits the system, subject to certain boundary conditions, to
84 Northeastern Naturalist Special Issue 1
adopt new states or structures. Thus, gradients with their specific coefficients,
e.g., coefficients of thermal conductivity or diffusion, are related
to, and an expression of, exergy flows in ecological systems. For evolving
biotic networks primarily isolated notional characterizations like
homogenization, amplification, synergism (Patten 1992), ascendency
(Ulanowicz 1986), power, or energy (Odum 1983) can be conveniently
associated with energetic or nutritional gradients. Also ecological hierarchies
can, for the sake of a unifying generic characterization, be
described in terms of scale-dependent hierarchies of gradients.
Gradients are the most conspicuous reflection of a system’s heterogeneity
which is, in the operational sense of the term, a scale-dependent
outcome of the regionalization procedures adopted. The generic definition
and analysis of ecologically relevant fluxes of energy, matter, and
information, including the determination of thermodynamic “forces”
and gradients, is therefore intimately linked with the appropriate definition
of spatial structures which frequently undergo seasonal or other
temporal variations. This fact assumes a particular quality when considering
ecosystems or their major compartments from the viewpoint of
self-organized dissipative structures (Fränzle 1994, Prigogine 1976). To
most effectively maintain the whole set of intra- and intersystemic
fluxes essential for the negentropy-related stability, the systems must
continuously degrade and re-establish a whole network of gradients
(Schneider and Kay 1994a). This implies that concentration processes
are necessarily coupled with entropy-exporting dissipative processes,
such that the succession of gradient formation and degradation can be
characterized by a temporal cyclicity as suggested by Holling (1986).
A final point to be made with regard to all concepts of ecosystem
analysis and modelling is the fact that the analyst in most cases has
incomplete and partial knowledge of the system which he seeks to
understand and control. The nature of his knowledge is often incremental
in that greater insight is gained as analysis or control continue. This
is the elementary basis for claiming long-term commitments for ecological
studies (Bennett and Chorley 1978, Pickett 1989b). However,
even under such favourable technical boundary conditions, elements in
the analysis of ecosystems will normally be necessarily indeterminate,
both because of the complexity of such systems and because of the
intimacy of man-environment interrelations or subjective constraints on
understanding. The major limitations are due to methods or measurement,
the presence of stochastic variation and the methods of system
analysis adopted, and finally the manner in which systems knowledge is
obtained, accumulated, and applied. Each of these points is of crucial
importance, and each constitutes a major challenge to both theoretical
reflection and systematic empirical research.
2001 O. Fränzle 85
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