Disturbance Ecology Top 5 Questions, Answers, and Future Directions Lindsay Berk December 9, 2005

In the beginning…

Questions for the Semester What have we learned? What generalities can we make? What are the obstacles to generality? What are the interesting and important questions? Lecture by Peter White: September 9, 2005

The Top 5

Number of Questions Disturbance Topic n=47

What is it? “A disturbance is any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment.” (White and Pickett 1985)

What is it? Is there an acceptable and universal definition of what constitutes a disturbance? How do we define disturbance intensity? If a disturbance is “any relatively discrete event in time…”, are humans a disturbance?

Diversity & IDH What is the relationship of diversity and disturbance? How common is the diversity-disturbance relationship that is predicted by the IDH? When and why does it not hold? What characteristics define the best disturbance regime for maximizing both productivity and diversity?

Diversity & IDH II Do intermediate disturbance levels produce the best levels of carbon sequestration and nutrient cycling compared to no disturbance or large, frequent disturbances? Instead of asking what the effects of disturbances are on diversity, is there an effect of diversity on disturbance regimes? (i.e. does diversity help to stabilize ecosystems?)

Diversity & IDH III If IDH does operate, what is its effect on diversity relative to other effects? Does ecological complexity increase resilience following disturbance events? Or, said another way, does reduced diversity increase restoration resistance in degraded systems?

Pattern, Process, & Scale Pattern or process? Which are we trying to restore? What about the effects of Process on Process and Pattern on Pattern? (e.g. Parasites & Fire, Floods & Landslides) and (Ecological Memory) How do we untangle the issue of scale and disturbance (severity, time, extent)? Is there a relationship between the scales of these three ranges?

HRV Is historic range of variability a worthwhile concept? Is the alternate stable state concept worthwhile? In what ways and on what scales does the variability of disturbance characteristics in time and space influence ecosystem function?

Large-Scale Interactions What are the long-term effects of multiple, compounded disturbances on ecosystems? Do they just take longer to recover compared to ecosystems experiencing single disturbances?

Invasives How do we (or CAN we) manage disturbance to mitigate for the effects of exotic invasions?

Criticality Does the effect of disturbance intensity on community structure and/or function increase smoothly or are there thresholds? If there are thresholds are they universal or site specific?

Disturbance-Recovery What is the role of disturbance-recovery cycles in the ecology-evolution connection? Are disturbance-recovery systems complex adaptive systems, and if they are, what are the implications? What is the connection between disturbance- recovery cycles and stability/ resilience/persistence? Can we formulate a theory that describes disturbance-recovery parameters that result in these properties?

Restoration & Management How can management mimic variability in disturbance, given the constraints under which managers often operate? Can we predict what impacts climate change will have on disturbance regimes and how does it impact our management of these regimes? Because of long-term departure from historic disturbance regimes, reintroduction of disturbance may lead to undesirable, novel results. Is there a way to predict these novel results?

Restoration & Management II What should be the guiding principles for managing disturbance if we cannot mimic the historic regime? To what extent should we try to replicate the HRV in disturbance regimes for managed lands (given that we can agree on what their HRV should be)? How can humans engineer "disturbed" systems?

Restoration & Management III Given that species respond to disturbance in novel ways, how do we manage systems at both landscape and regional spatial scales? In particular, how do we protect species of conservation concern yet still meet landscape restoration (management) targets? How do we know the appropriate level and type of disturbance to manage for "natural" conditions, considering the likely changes to disturbance regimes from climate change?

Restoration & Management IV Are we doing an adequate job in our conservation planning of setting aside enough land to manage for minimum dynamic area? At what temporal and spatial scale is restoration an attainable goal? How do we preserve systems with intact disturbance regimes? or how do we restore disturbance regimes or manage systems to simulate natural patterns of disturbance?

People & Nature How are human caused and non-human caused disturbances different? Can the same theoretical approach be applied to both? What anthropogenic disturbances are the most detrimental to natural systems and how can the effects of these be mitigated? What are the long range prospects? How will climate change affect disturbance regimes and in turn their stability and richness of ecosystems?

People & Nature II Given the difficulty of predicting the impacts of “natural” disturbance regimes (e.g. fire, flood, hurricanes), how can we ever truly predict the impacts of anthropogenic climate change? What is the contribution of human activities to (changes in) non-human disturbance cycles? (past, present, future?)

Others To what degree is the "suddenness" of the disturbance important? Is there a relationship between disturbance and stability? That is, are systems with a well-established disturbance history (and not the anthropogenic kind) more stable? More productive?

Generalities? What generalities can we make in disturbance ecology? Are there a few variables (ideally, measurable) that can describe the ecologically important properties of any disturbance-recovery system, regardless of system type, size, location, or other dynamics?

Thought Exercise Given $xx million to spend on disturbance research addressing any of the Top 5 questions, which would you choose and why?

Future Directions Where is disturbance ecology headed as a field?

Have we gotten any closer? What have we learned? What generalities can we make? What are the obstacles to generality? What are the interesting and important questions?

Best of… Disturbance Figures from Biology 255 or The Search for Generality

Pascual & Guichard 2005

Mackey & Currie 2001

Shiel & Burslem 2003

Peterson 2002

Schoennagel et al

Hobbs & Huenneke 1992

Brooks et al 2004

Turner MG, Baker WL, Peterson, CJ, and Peet RK Factors Influencing Succession: Lessons from Large, Infrequent Natural Disturbances. Ecosystems 1:

White et al. 2000

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