Timothy F. H. Allen

Role of heterogeneity in scaling of ecological systems under analysis

This chapter addresses heterogeneity in the context of scale. Scale is emerging as one of the critical problems that must be adequately considered if different ecological studies are to be either compared in a corroboration or contrasted in a refutation. Some argument in the ecological literature is misdirected because the contentions are differently scaled and so are not competitive (e.g., Belsky, 1986, 1987 versus McNaughton, 1985,1986, as discussed in Brown and Allen, 1989). Disparately scaled ecological situations cannot be compared in any simple way, even if superficially it appears that it is the same community or site that is being addressed.

Disturbance propagation by bark beetles as an episodic landscape phenomenon

Landscapes are the resultant of ecological processes and events operating on many different space-time scales. Large scale disturbance is recognized as a major influence on landscape patterns, but the impact of small scale events is often overlooked. We develop an hierarchical framework to relate lightning and bark beetle population dynamics to the southern pine forest landscape using the concepts of disturbance propagation and amplification. The low level lightning disturbance can be propagated to the landscape level when weather and forest stand structure facilitate bark beetle epidemics. We identify epidemics as biotically-driven episodes that alter landscape structure. The concept of the landscape as the spatial dimension of these episodes is represented in a conceptual model linking insect-host and landscape mosaic interactions.

Potential Corridors for the Rusty Crayfish, Orconectes Rusticus, in Northern Wisconsin (USA) Lakes: Lessons for Exotic Invasions

We sampled 35 lakes in northern Wisconsin to determine the presence of Orconectes rusticus, the rusty crayfish, and related this pattern to several parameters pertaining to potential invasion routes that could influence the distribution of these crayfish in the lakes. The presence of rusty crayfish in lakes was positively related to an index of human use and negatively related to the length of stream connections to other lakes containing the crayfish. Humans appear to act as vectors allowing crayfish to travel along discontinuous routes that otherwise would be inaccessible to them, and thus, provide crayfish with spatially discontinuous corridors that increase the probability of movement by channelizing the space between lakes. In contrast, streams correspond closely to the traditional definition of terrestrial corridors, in that they are spatially continuous. This distribution pattern suggests colonization operating via two corridors with two spatial scales, making management of the invasion of rusty crayfish complex.

Wetland Vegetation Dynamics in Response to Beaver (Castor canadensis) Activity at Multiple Scales

Abstract: Beaver activity is often considered a hydrologic disturbance that “resets” succession. We determined how beaver impoundment and wetland size and water chemistry affected the vegetation and succession of 25 beaver meadows and ponds using the space-for-time substitution. We used aerial photography to investigate whether a large 1947 fire in one region of Mount Desert Island, Maine, led to differences in regional temporal fluctuations in beaver pond occupancy over 60 y and determined whether these fluctuations led to different regional distributions of beaver wetland plant community types. Cluster analysis segregated 4 wetland groups: sedge meadows, sedge fens, shrub fens, and forested fens, which segregated along gradients of time since dam collapse, water chemistry, and wetland size. Beaver did not affect water chemistry or wetland size. Pond vegetation was a function of community type prior to flooding, water chemistry, and geomorphic setting. The successional model consisted of 2 separate cycles, corresponding to differences in pH and peat accumulations. Beaver pond creation rates differed in burned and unburned regions over time. Due to increased activity in the burned region, there was a different distribution of plant communities between the regions. Wetlands abandoned at the peak of beaver pond creation in 1979 were flooded for shorter durations, resulting in forested fen vegetation.. Beaver activity created different successional cycles within different water chemistry and geomorphic contexts. Water chemistry, wetland size, and initial wetland state, which primarily determined non-forested wetland type, were not influenced by beaver.

Conceptual Hierarchical Modeling to Describe Wetland Plant Community Organization

Using multivariate analysis, we created a hierarchical modeling process that describes how differently-scaled environmental factors interact to affect wetland-scale plant community organization in a system of small, isolated wetlands on Mount Desert Island, Maine. We followed the procedure: 1) delineate wetland groups using cluster analysis, 2) identify differently scaled environmental gradients using non-metric multidimensional scaling, 3) order gradient hierarchical levels according to spatiotemporal scale of fluctuation, and 4) assemble hierarchical model using group relationships with ordination axes and post-hoc tests of environmental differences. Using this process, we determined 1) large wetland size and poor surface water chemistry led to the development of shrub fen wetland vegetation, 2) Sphagnum and water chemistry differences affected fen vs. marsh / sedge meadows status within small wetlands, and 3) small-scale hydrologic differences explained transitions between forested vs. non-forested and marsh vs. sedge meadow vegetation. This hierarchical modeling process can help explain how upper level contextual processes constrain biotic community response to lower-level environmental changes. It creates models with more nuanced spatiotemporal complexity than classification and regression tree procedures. Using this process, wetland scientists will be able to generate more generalizable theories of plant community organization, and useful management models.

Liking and Disliking Household Objects: An Empirical Study of Value

The judgment of like/dislike may be an initial judgment in a hierarchy of criteria used to assign value to everyday objects. The finding implies that this subjective judgment, in turn, constrains succeeding value judgments, such as the perception of an objects utility and stylish ness. Forty-one subjects responded to two instruments: pair comparisons of 16 objects on a nine-point scale of similarity of value, and judgment of like/dislike of the same objects. The matrix of similarities was subjected to cluster analysis, producing a dendrogram for each indi vidual. Each dendrogram was compared to all others using an objective criterion. The data matrix of comparisons which resulted was subjected to principal component analysis. Like/dislike decisions were compared with both the dendrograms of each individual and the scatter diagrams summarizing the group. The judgment of like/dislike is discussed in relation to a conceptual framework based on the concepts of inherent and instrumental value.

Hierarchy Theory in Ecology

Hierarchy theory is a metatheory in the preanalytical stage, before questions are formulated. Without hypotheses of its own, it guides hypothesis creation for other theories. It organizes system description with asymmetric relationships that turn sets into levels. Size and scale may order hierarchies. But scaling may alter the type of entity recognized, thus forcing judgment and arbitrary choices on scale change. Hierarchies may be ordered on frequency, constraint, context, and bond strength at different levels. Entities from higher levels that consist of and contain lower levels appear in nested hierarchies, which are powerful for exploration. Non-nested hierarchies are often ordered on control not size (pecking order). Hierarchies address tension in a single entity being a whole, but also a part at some higher level. Holon refers to entities in hierarchies as the surface that integrates the parts so as to present a whole to the rest of the universe. But holons also offer protection to parts by integrating the environment. Hierarchies need not be real in an external world, but certainly appear in human understanding. The richness of hierarchies in ecology invites the theory to untangle elaborate relationships with precision of definition, thus blunting contentions that are merely semantic.

Radical Transitions from Fossil Fuel to Renewables: A Change of Posture

The transition from fossil fuel to renewable resources is more difficult than it at first appears. It is not just a pressing issue of policy and governance; it is a special case of a whole raft of problems that press contemporary society in transition. The trap is that fossil fuel and renewables both are matters of energy in the service of human society, but they are essentially different. The issue invites giving privilege to an engineering level of analysis which is not special except it is regularly chosen by experts. The justification for the privilege of energy as understood by engineers is reification of that level of analysis. Reification in turn leads to an assertion of a situation in material terms, when it is in fact an abstraction. More data do not help if the situation is not material; it is not a data problem. Dominant and recessive genes are not a data problem as conventionally conceived, so the errors coming from reification are commonplace. It has led to 60 years of misconception in the Darwinian new synthesis. The effects of genes do not simply cascade up to phenotype, but instead pass through a hierarchy of physiological processes. Similarly, joules do not simply cascade upward to give sums for fossil fuels and renewables that are equivalent and straightforwardly comparable. The critical complication is the distinction between energy sources versus energy carriers. Embedded in all this are the purposes of energy use. Wheat is an energy source, flour is a carrier, but horse feed uses the source while making cake uses the carrier. At each stage, there are grammars that act as constraints on sources and carriers. The language of fossil fuel use is different from renewable energy use. The reference systems for time and energy are simply different. To bring energy systems into equivalent terms, it is crucial that the language of energy capture in the environment be distinguished from language of energy currency inside the system. Energy use is a complex system because it requires more than one level of analysis, with no simple nor necessary translation between levels. Fossil fuel is so fundamentally different from renewable because fossil fuel is simply consumed while renewables must be hugely processed outside the system. These ideas are remarkably general because goods are carriers of service.

The Observer in Complex Systems: the Gateway Papers

Complexity demands a more sophisticated epistemology, where the mere complicatedness of old conceptions becomes inadequate. The past was modernist realism, where improved quality corresponded to a closer proximity of models to an external reality (Funtowicz and Ravetz 1992). The aim was for ecology to find out about the objective truth, but that can only be shown through distortion. The arts have gone through a similar transition from truth to post-modernity. Picasso’s modernist cubism distorts appearances so as to get closer to reality. There is still a profile to be viewed even if the image is seen in full-face, so cubism includes them both to capture that reality, and it all seems twisted and strange. In one sense cubism is a sophisticated view. But it still embraces a crude modernist pretense that the observer can be pried loose from experience. The observer was denied in distorted early television programs that appeared on black and white screens in living rooms, hiding the fact they were in fact contrivances in a studio. By contrast, David Frost’s BBC television show of 1962 “That Was The Week That Was,” (TW3) was suddenly post-modern. TW3 made no attempt to bend programming to make it seem real. It abandoned reality, and became the first show to allow the audience to see the contrivance of cameras and lights (tired nightly news does it all the time now!). TW3 credits were purposefully not slick, but consisted of pieces of cardboard hand written, held awkwardly in front of each cast member. Modernist distortion is alive and well in normal science ecology. Most ecology is still written up sanitized, hiding the mess of actually doing science, just like 1950s television hid studio devices. But now we live in a world where big problems manifest complexity; we simply cannot get away with hiding the observer, and the mess they bring. A more honest epistemology is required if ecology is to get beyond stamp collecting, so as to address real problems. The papers that influenced me admitted that observations require an observer.