Week 3 Discussion Questions: Organized list

Mechanics of pattern formation

Which are the effects of diffusion in the relation of pattern develop of spatial structures?

The authors explain several natural patterns in vegetation, reefs, and mudflats that involve a short-distance positive feedback and a long-distance negative feedback. What is the cutoff for “short” and “long” distances, and what happens if more than two spatial feedbacks are at play (e.g., one at the scale of meters, on at the scale of tens of meters, and one at the scale of kilometers)?

Clarification questions: Can you explain power-law clustering of vegetation in arid ecosystems? Why is this short distance positive feedback showing long-distance negative feedback is important? Why do the observation of regular pattern formation and power-law clustering provide a strong indication of the “omnipresence” of spatial self-organization?

What other systems can we place into this patterning framework (i.e., patterning by short-range facilitation/long-range inhibition)?

Is such patterning primarily driven by biological systems, or do geological systems exhibit similar properties?

Considering that the spatial patterns and feedbacks that explain the configuration of the ecosystems; Could you consider the alellopathic effect of some plant species for the explanation the patterns of a vegetation? Could the home range of a carnivorous predator explain the pattern of distribution of the same species in a region?

Could the tectonic movement of the plates of the earth be analyzed as a natural pattern? Can be the change in the ocean current be analyzed as a spatial pattern?

Pattern initiation, development, and geography

Does the patterning tend to erase the historical footprints of the ecosystems?

What are the primary drivers of anisotropy in patterned systems?

Would we find more or fewer patterns in environments with gradients? Are pattern formations only very relevant where biologically mediated resource concentrations or stress alleviation is important?

Would we find more or fewer examples in benign conditions for scale dependent feedbacks? Would it be harder to detect the effect of inhibition at larger distances?

Environmental heterogeneity and noise

Are ecosystems with regular patterns ever considered heterogeneous?

Rietkerk and van de Koppel mention that environmental heterogeneity can obscure pattern formation. Is this an example of white noise in a system, or rather confounding factors in a more complex system? Can noise be separated out to understand pattern formation with a technique like nonlinear forecasting? How does this complement the techniques described for determining long-distance feedbacks (removal and cross- correlation)?

Length scales and timescales

Do these patterns (given no large disturbance in environment), tend to remain the same year after year? I.e., are they mostly immune to temperature changes?

How are length-scales of regular patterning related to length-scales of feedback mechanisms or other factors?

In the case that you use a discrete model to explain the spatial pattern; How many landscape scales could you use the same model to predict spatial patterns?

The example of forests in Siberia, wherein lines of trees modify wind patterns so that snow drifts between the lines, is similar to restoration strategies that involve the construction of infiltration basins along contour lines. The authors suggest that mimicking regular natural patterns in restoration efforts may increase success. How can their observational findings be quantified in a more general form, to yield (for example) an optimal distance between contour trenches or lines of trees for a given site?

Implications for resilience and landscape function

How can you calculate the thresholds that change a potentially self-recover ecosystem to a catastrophic ecosystem scenario?

How could changes in regular patterns indicate a loss or gain of resilience or resistance in real ecosystems? Examples beyond desertification? Would change detection (or change itself) in the ecosystem be influenced by whether it was benign (humid?) or stressed (arid)?

The mechanisms for increased ecosystem functionality with patterning seem to be related to positive local feedbacks, but long-distance negative feedbacks are the critical factor for the emergence of regular patterning. How does long-distance negative feedback increase system functionality? Perhaps through an ability to make “optimal use of limiting resources”?

Inferring mechanisms from pattern

What can be determined about factors driving the changes in an ecosystem (e.g. rainfall, soil quality, etc) by only looking at the patterning?

Model formation and validation

How does one tackle the question of balancing realism and simplicity in CES models? For example, in tidal mudflats there are both physical and biological mechanisms for pattern formation. How do you determine which mechanisms are important? How do you determine that you are examining the relevant mechanisms and not over-simplifying the system?


Comments

Week 3 Discussion Questions: Organized list — 7 Comments

  1. (Suding et al.)
    1. What physical or climatological processes might indicate whether an ecosystem is likely to exhibit resilience in its degraded state? (Didham et al. address one such process regime).
    2. The examples in Suding et al. come primarily from terrestrial ecosystems or wetlands with emergent vegetation, and focus on vegetation re-establishment as a “target”. How do these principles translate into the fluvial environment, wheere vegetation is arguably less important, and other kinds of processes exert strong drivign forces on habitat condition and species distribution?
    3. Does “stable” include dynamially stable (e.g. oscillating) systems, and if so, how might the timing of a restoration intervention (to coincide with a particular tranistory state) influence outcomes.

    (Didham and Watts 2005)
    1. The authors point out the importance of the scale of observation in determining whether a coummunity is abiotically or biotically driven (413). However, at large enoubh scales, every ecosystem is abioticlly driven. Is the key, then, to first identify the scale of a restoration intervention (usually dictated by politics, land ownership, or resources) and then determine whether biotic or abiotic drivers are more important at that scale?
    2. What is meant by “transient states” and how can they be distinguished from alternative stable states?
    3. Many degraded ecosystmes characterized by invasive species exhibit low diversity. Are these systems also examples of systems where “traits of species are markedly under-dispersed”? (414).

  2. How does one tackle the question of balancing realism and simplicity in CES models? For example, in tidal mudflats there are both physical and biological mechanisms for pattern formation. How do you determine which mechanisms are important? How do you determine that you are examining the relevant mechanisms and not over-simplifying the system?

    How are length-scales of regular patterning related to length-scales of feedback mechanisms or other factors?

    Rietkerk and van de Koppel mention that environmental heterogeneity can obscure pattern formation. Is this an example of white noise in a system, or rather confounding factors in a more complex system? Can noise be separated out to understand pattern formation with a technique like nonlinear forecasting? How does this complement the techniques described for determining long-distance feedbacks (removal and cross-correlation)?

    The mechanisms for increased ecosystem functionality with patterning seem to be related to positive local feedbacks, but long-distance negative feedbacks are the critical factor for the emergence of regular patterning. How does long-distance negative feedback increase system functionality? Perhaps through an ability to make “optimal use of limiting resources”?

  3. Posted these in the wrong place at first. Oops!

    Week 3 discussion questions (Rietkerk & van de Koppel 2008)

    1. Are ecosystems with regular patterns ever considered heterogeneous?

    2. Would we find more or fewer patterns in environments with gradients? Are pattern formations only very relevant where biologically mediated resource concentrations or stress alleviation is important?

    3. Would we find more or fewer examples in benign conditions for scale dependent feedbacks? Would it be harder to detect the effect of inhibition at larger distances?

    4. Clarification questions: Can you explain power-law clustering of vegetation in arid ecosystems? Why is this short distance positive feedback showing long-distance negative feedback is important? Why do the observation of regular pattern formation and power-law clustering provide a strong indication of the “omnipresence” of spatial self-organization?

    5. How could changes in regular patterns indicate a loss or gain of resilience or resistance in real ecosystems? Examples beyond desertification? Would change detection (or change itself) in the ecosystem be influenced by whether it was benign (humid?) or stressed (arid)?

  4. 1. What can be determined about factors driving the changes in an ecosystem (e.g. rainfall, soil quality, etc) by only looking at the patterning?

    2. Does the patterning tend to erase the historical footprints of the ecosystems?

    3. What are the primary drivers of anisotropy in patterned systems?

    4. Do these patterns (given no large disturbance in environment), tend to remain the same year after year? I.e., are they mostly immune to temperature changes?

    5. Is such patterning primarily driven by biological systems, or do geological systems exhibit similar properties?

  5. 1. Considering that the spatial patterns and feedbacks that explain the configuration of the ecosystems; Could you consider the alellopatic effect of some plant species for the explanation the patterns of a vegetation? Could the home range of a carnivorous predator explain the pattern of distribution of the same species in a region?

    2. Could the tectonic movement of the plates of the earth be analyzed as a natural pattern? Can be the change in the ocean current be analyzed as a spatial pattern?

    3. Which are the effects of diffusion in the relation of pattern develop of spatial structures?

    4. How can you calculate the thresholds that change a potentially self-recover ecosystem to a catastrophic ecosystem scenario?

    5. In the case that you use a discrete model to explain the spatial pattern; How many landscape scales could you use the same model to predict spatial patterns?

  6. Here are this week’s questions…

    Max Rietkerk1 and Johan van de Koppel2
    1. The authors explain several natural patterns in vegetation, reefs, and mudflats that involve a short-distance positive feedback and a long-distance negative feedback. What is the cutoff for “short” and “long” distances, and what happens if more than two spatial feedbacks are at play (e.g., one at the scale of meters, on at the scale of tens of meters, and one at the scale of kilometers)?
    2. The example of forests in Siberia, wherein lines of trees modify wind patterns so that snow drifts between the lines, is similar to restoration strategies that involve the construction of infiltration basins along contour lines. The authors suggest that mimicking regular natural patterns in restoration efforts may increase success. How can their observational findings be quantified in a more general form, to yield (for example) an optimal distance between contour trenches or lines of trees for a given site?

    Sole and Bascompte
    1. On p. 82, the authors contrast von Hardenberg et al.’s model, which accounts for runoff, with Klausheimer’s model, which assumes a flat surface (among other simplifications). Runoff is approximated by runoff depth and is assumed to vary linearly with vegetation density; how does slope affect runoff in this model?

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