Environmental Science

134 ENVIRONMENTAL SCIENCE

(1) Autotrophic succession is characterized by early and continued dominance of

autotrophic organisms like green plants. It begins in a predominantly inorganic

environment. In it the energy flow is maintained indefinitely.

(2) Heterotrophic succession is characterized by early dominance of heterotrophs, such

as bacteria, actinomycetes, fungi and animals. This sort of succession begins in a

predominantly organic environment and there is a progressive decline in the energy

content.

Serule

The miniature succession of micro-organic environment and different types of fungi on
the fallen logs of the decaying wood, tree bark, etc. is called serule.

Drury and Nisbet (1973) classified succession into three main types:

(a) Category I includes many classical types of secondary succession and some primary

successions. It involves temporal sequences on one site with climate and

physiography mostly remaining stable.

(b) Category II includes many primary successions (especially those in ponds and

lakes) and a few secondary successions. In this, temporal sequences on site with

the local environment changes under the influence of such external factors as

climate, erosion, drainage, nutrient inputs, etc.

(c) Category III includes those changes, which take place over long (geological) time

scale, and cover spatial sequences on adjacent sites.

Common attributes of Ecological Succession

Some Common attributes of ecological succession are as under:

Table 3.3 Ecosystem Attributes

Ecosystem attributes Development Stage Mature Stages

Community Energetics More or less than 1 About 1 (or

Gross production/community respiration approaches 1)

Gross production/standing crop biomass High Low

Biomass supported/unit energy flow Low High

Net community production (yield) High Low

Food Chains Mainly grazing; detrital Predominantly linear

web like

B. Community Structure

Total organic matter Less More

Inorganic nutrients Extrabiotic Intrabiotic

Species diversity Low High

Biochemical diversity Low High

Spatial heterogeneity and stratification Poor Well-organized

(Contd.)