Understanding Ecosystems: Structure, Function, and Services
Ecosystem Structure and Function
You have looked at the various components of the environment – abiotic and biotic. You studied how the individual biotic and abiotic factors affected each other and their surroundings. Let us look at these components in a more integrated manner and see how the flow of energy takes place within these components of the ecosystem. Interaction of biotic and abiotic components results in a physical structure that is characteristic for each type of ecosystem. Identification and enumeration of plant and animal species of an ecosystem gives its species composition. Vertical distribution of different species occupying different levels is called stratification.
Productivity in Ecosystems
A constant input of solar energy is the basic requirement for any ecosystem to function and sustain. Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. It is expressed in terms of weight (g-2) or energy (kcal m-2). The rate of biomass production is called productivity.
Decomposition Processes
You may have heard of the earthworm being referred to as the farmer’s ‘friend’. This is because they help in the breakdown of complex organic matter as well as in loosening of the soil. Similarly, decomposers break down complex organic matter into inorganic substances like carbon dioxide, water, and nutrients, and the process is called decomposition. Dead plant remains such as leaves, bark, flowers, and dead remains of animals, including fecal matter, constitute detritus, which is the raw material for decomposition. The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification, and mineralisation.
Energy Flow in Ecosystems
Except for the deep-sea hydrothermal ecosystem, the sun is the only source of energy for all ecosystems on Earth. Of the incident solar radiation, less than 50 percent of it is photosynthetically active radiation (PAR). We know that plants and photosynthetic and chemosynthetic bacteria (autotrophs) fix the sun’s radiant energy to make food from simple inorganic materials.
Ecological Pyramids
You must be familiar with the shape of a pyramid. The base of a pyramid is broad, and it narrows down at the apex. One gets a similar shape whether you express the food or energy relationship between organisms at different trophic levels. Thus, the relationship is expressed in terms of number, biomass, or energy.
Ecological Succession
Consider the characteristics of population and community and also their response to the environment and how such responses vary from an individual response. Let us examine another aspect of community response to the environment over time. An important characteristic of all communities is that composition and structure constantly change in response to the changing environmental conditions. This change is orderly and sequential, parallel with the changes in the physical environment. These changes lead finally to a community that is in near equilibrium with the environment, and that is called a climax community. The gradual and fairly predictable change in the species composition of a given area is called ecological succession.
Ecosystem Services
Healthy ecosystems are the base for a wide range of economic, environmental, and aesthetic goods and services. The products of ecosystem processes are named as ecosystem services; for example, healthy forest ecosystems purify air and water, mitigate droughts and floods, cycle nutrients, generate fertile soils, provide wildlife habitat, maintain biodiversity, and pollinate crops.