Pattern and Process

Peter White, Professor, Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 email: peter.white@unc.edu

One of the treasured moments of my career was meeting Alex Watt, then in his 90s with silver hair and a cane, sitting at a table in a Cambridge University coffee shop. Plant ecologist Peter Grubb introduced us. Watt published a paper in 1947 that had become a touchstone for me and I remember feeling that I was in the presence of greatness. I hadn’t known the paper as a beginning student and so had not shaped my thesis around it (though perhaps I should have). Rather, I found this paper after I had developed a passion, part empirical and part intuition, that ecosystem dynamics was not just a one way successional march but also included inevitable death and dynamics that created younger patches that themselves were interesting and enlightening. Watt’s paper presented the case simply and eloquently.

I had discovered other papers that told the story of dynamics, some going back many years (Cooper 1926, Raup 1941) but Watt’s paper pulled all the pieces together for me (and literally so in terms of the internal patches of an ecosystem). What I appreciated about Watt’s paper was seeing an inquisitive mind at work as it developed a general conceptual framework that applied to an interesting problem in diverse ecosystems. The paper also celebrates the empirical details of vegetation as diverse as forests and heathlands. Part of the thrill, to a beginning ecologist, was that this perspective confirmed an egalitarian view of species: instead of the typical competitive hierarchy and the view that ecosystems develop because some species are better adapted, the pattern and process perspective is that all species are “best” in some set of circumstances and, owing to trade-offs, a species can’t be a rapid colonizer when resources are high and also a long-lived best competitor when free resources are scarce (after they have been largely taken up into biomass).

Watt’s paper had a compelling title too, “Pattern and process in the plant community” and this inspired the title of my own first paper “Pattern, process, and natural disturbance in vegetation” (White 1979). But I wasn’t alone: I suspect that many of the readers of this essay can fill in the blank in the following phrase “Pattern and process in _______________”. A small sample of paper titles includes the following phrases where that blank occurs: “ a forested ecosystem”, “cliff ecosystems”, “mangrove ecosystems”, “neotropical secondary rain forests”, “the dynamics of seed banks”, “aquatic ecology”, “plant-pathogen interactions”… One great excitement of ecology is the relationship of pattern and process and determining how one influences the other. This view transforms the view of vegetation from static habitat to a set of dynamic populations, ecological processes, and changing environments. A dynamic view gives us new purpose and excitement in our work and draws us closer to understanding nature itself.

For me, the paper trail runs on from Watt (1947), through John Thompson’s (1978) phrase “patch dynamics” and Pickett and White (1985). An explosion of interest in disturbance and dynamics was by then underway (White and Jentsch 2001). Much empirical detail has been added to our understanding in the last 30 years. Using fire in order to give a few examples, that empirical work includes disturbance adaptations (e.g., Johnson and Gutsell 1993 on the conditions that cause serotinous cones to open), the physical parameters that characterize the ecological work that disturbances do (e.g., thermocouple detection of the temperature and duration regimes of different fires, Ryan et al. 2010), the different roles of top-down (climate) and bottom-up (ecosystem characteristics) influences on disturbance regime that is so crucial to management (e.g., climate versus fuel influences on fire characteristics, Agee and Huff 1987), the influence of pattern on process (e.g., the contrast between the fire regimes of boreal forest and lake islands within the boreal forest, Bergeron and Brisson 1990), ideas about stability and variance (e.g., Turner et al 1993 as a further development of Shugart 1984), and experiments (e.g., Cadotte’s 2007 exploration of the intermediate disturbance hypothesis). Change in fire, wind, flood, coastal erosion, and other disturbances are now rightfully part of climate change research (e.g., for an early paper, Swetnam 1993). There is so much important work that it is, in fact, hard to draw the list and this essay to a close!

Literature cited

Agee, J.K., and M.H. Huff. 1987. Fuel succession in a western hemlock/Douglas-fir forest. Can. J. Forest Research 17: 697-704.

Bergeron, Y. , and J. Brisson. 1990. Fire regime in red pine stands at the northern limit of the species’ range. Ecology 71:1352-1364.

Cadotte, M.W. 2007. Competition-colonization trade-offs and disturbance effects at multiple scales. Ecology 88: 823-829.

Cooper, W. S. 1926. The fundamentals of vegetation change. Ecology 7:391-413.

Johnson, E. A., and S.L. Gutsell. 1993. Heat budget and fire behavior associated with the opening of serotinous cones in two Pinus species. J. Vegetation Science 6: 745-750.

Pickett, S. T. A., and P. S. White (eds.) 1985. The ecology of natural disturbance and patch dynamics. Academic Press, New York, pp 3-13.

Raup, H.M. 1941. Botanical problems in boreal America. Bot. Rev. 7:147-248.

Ryan, K.C., E. Rigolot, F.C. Rego, H. Botelho, J.A. Vega, P.M. Fernandes, and T.M. Sofronova. 2010. In: Wade, Dale D.; Robinson, Mikel L., eds. Proceedings of 3rd Fire Behavior and Fuels Conference; 25-29 October 2010; Spokane, WA. Birmingham, AL: International Association of Wildland Fire. 20 p.

Shugart, H.H. 1984. A theory of forest dynamics. Springer-Verlag. New York.

Swetnam, T. W. 1993. Fire and climate change in giant sequoia groves. Science 262: 885-889.

Thompson, J.N. (1978). Within-patch structure and dynamics in Pastinaca sativa and resource availability to a specialized herbivore. Ecology 59: 443-448.

Turner, M.G., W.H. Romme, R. H. Gardner, R.V. O’Neill, and T.K. Kratz. 1993. A revised concept of landscape equilibrium: disturbance and stability on scaled landscapes. Landscape Ecology 8: 213-227.

Watt, A.S. 1947. Pattern and process in the plant community. J. Ecol. 11:1-18.

White, P. S. 1979. Pattern, process, and natural disturbance in vegetation. Bot Rev 45:229‑299

White, P. S., and A. Jentsch. 2001. The search for generality in studies of disturbance and ecosystem dynamics. Progress in Botany 62:399-450.