Abiotic factors in communities

Abiotic factors are the non-living conditions that affect organisms. A change in an abiotic factor can affect how well organisms survive, grow and reproduce. This can change a population’s abundance—how many individuals are present—or its distribution—where they are found.

A community consists of populations of different species living and interacting in the same area. If an abiotic change affects one population, it can also affect populations that depend on it. For example, conditions that reduce plant growth may leave less food for animals that eat the plants. As populations change, the species present and their relative abundances can change, altering the community’s composition.

Abiotic factors and their effects

• Light intensity affects the rate of photosynthesis and therefore plant growth. A plant receiving too little light may grow more slowly.
• Temperature affects biological processes. Species differ in the temperatures they can tolerate, so a temperature change may favour some species while harming others.
• Moisture affects how much water is available to organisms.
• Soil pH and mineral content affect conditions for plant growth and the availability of mineral nutrients.
• Wind intensity affects how exposed organisms are and can increase water loss. Wind direction affects which locations are exposed.
• Carbon dioxide availability can affect the rate of photosynthesis in plants.
• Dissolved oxygen availability affects respiration in aquatic animals.

An increase in a factor is not always beneficial. Its effect depends on the organism and the conditions involved. For example, an increase in temperature may improve conditions for one species but move them beyond the range tolerated by another.

Using data on abiotic factors

Charts, graphs and tables can show how abundance or distribution varies with an abiotic factor. Before comparing values, check the axis labels or table headings and units to identify what is being measured and which organisms or conditions are being compared.

Read the relevant values, then look for a trend or difference. For example, a graph may show that a species is more abundant at some moisture levels than at others. Use that pattern and the context provided to explain how the factor may affect the species and, through its interactions with other populations, the community. A pattern alone does not establish that the abiotic factor caused the difference; other conditions may also have an effect.