MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedonyuk 2010

BIOLOGY

CHAPTER 2. BIOGEOCENOTIC LEVEL OF ORGANIZATION OF LIFE AND THE PLACE OF HUMANS IN IT

2.1. FUNDAMENTALS OF HUMAN ECOLOGY

Ecological Succession

A biogeocenosis is a stable, dynamic, self-regulating system. However, the stability of a biogeocenosis is not absolute; it is capable of changing and evolving. Directed, sequential changes within a biogeocenosis are referred to as ecological succession. These processes can lead to the replacement of one biogeocenosis by another. A classic example of such succession is the gradual overgrowth of a small lake, eventually transforming into a marsh and, subsequently, a forest. Plants play the primary role in driving succession, accompanied by the successive replacement of certain plant species by others. Concurrently, the species composition of animals also changes. Successions are classified as either primary or secondary. The Development of vegetation in areas where it did not previously exist is called primary succession (such as the colonization of bare rocks by Lichens or the settlement of sand dunes by higher plants). Conversely, succession occurring in areas with pre-existing vegetation that has been destroyed by certain factors is known as secondary succession (such as forest regeneration after fires or logging). Succession culminates in a climax community—The formation of a stable community whose species composition subsequently undergoes little change. Most successions require hundreds to thousands of years to reach completion. The rate of succession decreases as it approaches the climax stage. Succession ceases when the arrival of new species or the loss of existing ones no longer disrupts the equilibrium. Thus, climax communities are characterized by a state of relatively stable equilibrium.