Disturbance

by

E. A. Johnson

• LAST REVIEWED: 27 June 2017
• LAST MODIFIED: 27 June 2017
• DOI: 10.1093/obo/9780199363445-0073

Introduction

Disturbance is often used, intuitively or colloquially, to imply some disastrous event that is disruptive or destructive. In natural sciences, it implies something contrary to the natural order of things, and in natural hazards research it involves the destruction of built facilities or injury and death of humans and domestic animals. Here the term “disturbance” is used in the way it is used in ecology, the history of its recognition and the developing understanding of how disturbance processes are causally connected to ecological processes (see Pickett and White’s The Ecology of Natural Disturbances and Patch Dynamics, cited under the Importance of Disturbance). Natural disturbance studies have made significant contributions in the following areas: the quantitative understanding of recurrent events in both geoscience and ecological science, the mechanisms of natural disturbances that affect processes in ecological systems, and the interaction of natural disturbances with other physical, biological, and human-caused processes. Disturbance research has shown that natural disturbances are frequent enough that ecosystems, rather than maintaining long-term stability, are frequently reorganized into “novel” combinations. The incorporation of process into studies of disturbances is still incomplete, offering many opportunities for interaction with the biological and geosciences, from studies of specific processes and individual organisms to large-scale processes in physical and biological systems.

The Importance of Disturbance

The concept of disturbance began to interest ecologists in the 1930s through the 1960s, in an attempt to determine whether biotic communities were stable and self-propagating. Disturbance was understood as a rare and transitory event that destroyed or interrupted the natural development or succession of biotic communities. Scientific examination of communities focused on finding so-called climax communities and tracing the successional stages toward this climax. Disturbances took place quickly, from the human viewpoint, and were not always understood according to the ecological processes. Raup 1957 is a good discussion of this early period. Raup would also be involved in the changes to follow. Natural disturbances were investigated by North American ecologists in particular because of the widespread belief that parts of North America were still wilderness or little disturbed by Europeans. Disturbances in North America have an interesting dichotomy. In the West, conifer forest and chaparral disturbances generally affect large areas, with wildfire and insect outbreaks as the principal causes. In the East, deciduous forest disturbances are predominantly caused by wind and insects. Wind causes uprooting and breakage in individual trees and whole forests. Differences in the spatial scales of disturbances reinforced an older idea, the concept of gap phase replacement, espoused in Watt 1947 (see also Pickett and White 1985; Yamamoto 1992). In the deciduous forest of eastern North America, for example, gap phase dynamics are used to explain the growth and regeneration of different tree species in holes in the tree canopy created by wind or insects (e.g., Frelich 2002). Hugh Raup recognized that natural disturbances could be recurrent. At Harvard Forest, Raup found that a 1938 hurricane that hit New England had blown down vast areas of mostly old-growth forest, and asked whether hurricanes in the past might have done the same thing. To answer this question, he looked at the ages of the oldest blown down trees and found that most dated to the 1600s and then found historic records of a large hurricane hitting New England at that time. Since then, many studies have confirmed this idea (Foster and Aber 2004).

• Foster, D. R., and J. D. Aber. 2004. Forest in time: The environmental consequences of 1,000 years of change in New England. New Haven, CT: Yale Univ. Press.

  Overview of research on disturbance in New England.

• Frelich, L. E. 2002. Forest dynamics and disturbance regimes: Studies from temperate evergreen-deciduous forests. Cambridge, UK: Cambridge Univ. Press.

  DOI: 10.1017/CBO9780511542046

  Overview of research on disturbance in northern hardwoods of the lake states in the United States.

• Pickett, S. T. A., and P. S. White. 1985. The ecology of natural disturbances and patch dynamics. San Diego, CA: Academic Press.

  This book clearly summarizes the state of research when disturbance was recognized as a normal part of ecosystems. Although more would be done in the next few decades, this book is a classic of changing viewpoints of dynamics.

• Raup, H. M. 1957. Vegetation adjustment to the instability of the site. In Proceedings and Papers, 6th Technical Meeting, International Union for Conservation of Nature and Natural Resources, Edinburgh, June 1956. Edited by International Union for Conservation of Nature and Natural Resources, 36–48. London: Society for the Promotion of Nature Reserves.

  One of the early pioneers in recognizing natural disturbances and the need to understand the processes.

• Watt, A. S. 1947. Pattern and process in the plant community. Journal of Ecology 35:1–22.

  DOI: 10.2307/2256497

  The classic paper on gap dynamics, now somewhat out of date but was important in getting ecology out of its descriptive stage and into studying processes as creators of patterns.

• Whitney, G. G. 1984. From coastal wilderness to fruited plain: An ecological history of northeastern United States. Cambridge, UK: Cambridge Univ. Press.

  Wilderness as a cultural landscape.

• Yamamoto, S.-I. 1992. The gap theory in forest dynamics. The Botanical Magazine, Tokyo 105:375–383.

  DOI: 10.1007/BF02489426

  An early review of gap theory but not from a North American viewpoint.