Community Ecology – Nature of Communities

Introduction to the Nature of Communities

Types of community

The two main types of community are Major community and minor community.

• Major community: A major community is the smallest ecological unit that can self-regulate and maintain itself. These communities are typically isolated from other communities, such as a pond, a forest, a grassland, or a lake. Only creatures that have effectively adapted to the environment and to the other species in the community can form long-lasting and mature large communities. A major community is made up of a faunal community, floral community, and microbial community).
• Minor Community: Minor communities, also known as merocenoses, are tiny ecological units that are not self-sustaining and depend on interactions with bigger communities to survive. A group of organisms living within a piece of deadwood on the forest floor is an example of a minor community.
• A community can also be classified as open or closed. An open community is one in which organisms, particularly plants, are distributed and thus open to new invasion.
• The organisms in a closed community are clustered together. As a result, no more organisms will be able to live in the area.

Where there is a long environmental gradient, such as that of soil moisture content or the altitudinal slope of a mountain, open communities tend to form. At different spatial scales along the gradients, organisms with differing tolerances to the environment can be found.

Closed communities form if the vegetative structure or physical environment suddenly changes, such as a part of a beach that separates the water from the land.

Different types of ecosystems consist of different communities.

• For example, a temperate ecosystem consists of a community with deciduous trees, coniferous trees, agricultural products, and animals like monarchs and chipmunks. These are all biotic components of the temperate ecosystem.
• Community with plants like cactus, sagebrush, mesquite trees, and animals like lizards, bats, and woodpeckers are biotic components of the desert ecosystem.

Explanation:

Nature of communities (Characteristics of community)

Characteristics of community: The qualities that define communities are highly variable, and there are a number of characteristics that can be used to distinguish them, such as:

Trophic organization, dominance, interdependence, species diversity, growth form and succession, stratification, and ecotone.

1. Trophic organization: Each organism in a community can be classified into one of several trophic levels based on how it obtains nutrients. These trophic levels are classified into three categories:

• Primary producers (also known as autotrophs) use the Sun’s energy to perform photosynthesis, which allows them to make their own food. Green plants and algae are the most common primary producers.
• Consumers, also known as heterotrophs, depend on other organisms for nutrition. Primary consumers, also known as herbivores, consume plants, whereas secondary and tertiary consumers, sometimes known as carnivores or omnivores, consume primary consumers.
• Decomposers (also known as heterotrophs) consume dead plant and animal matter and return the nutrients to the environment. The way energy is transported across different trophic levels can be used to describe communities. In a grassland community, for example, the grass (primary producer) is eaten by a mouse (primary consumer), which is then eaten by a snake (secondary consumer), and finally, an eagle (tertiary consumer) feeds on a snake. Fungi (decomposers) may eat the eagle’s body after it has died.

2. Dominance: At each trophic level, there are usually one or two species that have a greater influence on the community’s function and structure than others. This could be due to their size, population, or behaviors that have a negative influence on other organisms or the environment. These ‘ecological dominants’ can have a significant impact on the community’s nature.

Plants typically dominate land communities; hence, the community’s name is commonly derived from the ecologically prominent plants, such as Douglas-fir Woodland or Rocky Mountain Maple Forest. Although ecological dominants may be responsible for changing a habitat’s abiotic factors, rare species may be just as crucial for the community’s proper functioning.

In a forest, for example, a dominant tree species may influence the quantity of light available to other plants, the temperature in the lower canopy, and the nutrients available to other organisms, while pollination by a rare insect may be required for their reproduction.

3. Interdependence: Communities aren’t just a random collection of plants, animals, and bacteria; each of the organisms in a community is fundamentally dependent on at least one other, but most will interact multiple times.

Interdependence can be divided into three categories

i. Nutritional Interdependence: The transmission of energy and nutrients during feeding is referred to as nutritional interdependence. Certain organisms, such as insects that can only eat one type of plant, are maybe more dependent on the presence of others to meet their nutritional needs.

ii. Reproductive Interdependence: Reproductive freedom can come in a variety of shapes and sizes. Pollination is a common example that occurs in almost all cultures. While the encounter offers nectar for the pollinator, it is critical for the plant’s reproductive success. Certain species may be able to reproduce only on a specific plant or substrate and thus are reliant on its presence in the ecosystem. Another reproductive independence is based on parasitic interactions, such as cuckoos laying their own eggs in the nests of other birds.

iii. Protective Interdependence: The third major interaction is protective interdependence. Most species require some form of shelter, which they may obtain from other organisms in the community. Insects living on trees, for example, rely on the leaves and branches to protect them from bird attacks.

Community relationships are not usually linear and can involve a number of very complicated interactions. Many of these interactions may only occur in specific environmental conditions. The symbiosis between corals and the photosynthetic algae that reside within their body structures is an example of this. The contact provides energy to the coral and nutrients to the algae; however, the algae can only stay within the body at particular temperatures.

4. Species Diversity: The complexity of species in a community is referred to as diversity. The species richness and species evenness (i.e., the relative abundance of species) are the two parameters through which species diversity can be measured. The number of various species coexisting in a given area is referred to as species richness. In comparison to locations near the poles, areas around the equator have the greatest species richness because the natural circumstances (low seasonality and high rainfall) are more conducive to a wider range of species.

• The relative abundance (species evenness) of species is another essential measure. It’s the proportion of a species’ individuals to the total number of individuals in a given habitat. Due to the high production of plants, which get significant amounts of solar energy and possess year-round climatic stability, tropical communities tend to have great species richness and diversity. Community structure in ecosystems like polar tundra, on the other hand, is extremely different, with decreased species richness as a result of less basic resources like sunlight and Communities with a greater diversity of species are more resilient to ecological damage. Here, in the given image, the community has the same species richness but different species evenness.

5. Growth form and Succession: The primary categories of a community’s growth form can be used to characterize it. For example, mosses, herbaceous plants, shrubs, and trees.

The successional stage of a community can also be used to characterize it. The gradual and predictable replacement of one form of the community by another over time is referred to as ecological succession.

The initial colonization of a bare landscape that has never been colonized, frequently following a large ecological disturbance such as a volcanic explosion, is known as primary succession.

Secondary succession happens when a community has existed in the past but has been displaced from its natural habitat, such as a deforested area or abandoned agriculture. In this situation, nutrients are already available in the soil, and growth circumstances are good; therefore, secondary succession occurs much faster than primary succession.

The pattern frequently begins with pioneer plants like grasses and perennials. Higher types of plant species (such as shrubs and pines) emerge after a period of time. The intermediate species is the name given to them. In the end, more advanced plant species emerge (e.g., oak and hickory). The assemblage is referred to as the climax community when it reaches (again) stability. Equilibrium is maintained until the next disturbance occurs.

Once their seeds or spores migrate from surrounding places and successfully germinate, pioneer species are the first to populate a bare landscape. Fast-growing, hardy plants with a limited lifespan and low biomass, which require very little nutrients, make up these pioneer communities. Nitrogen-fixing bacteria are found in the roots of pioneer species, which are necessary for the production of soil and other organic matter.

After the pioneer community, seral communities emerged in the area. These transitional communities are made up of intermediate-sized species with high biomass and nutritional content, such as shrubs and heaths. Biogeochemical cycling helps these species produce soil and nutrients.

The Climax Community is a self-regulating, stable biotic community that develops over time. Longer living and larger species with high niche specialization, complex food webs, and mature interdependent interactions can be found there. Within climax communities, diversity is maximum, and the community is in balance with the habitat and climate.

6. Stratification: A community’s structure can be depicted through zonation or stratification. A lake community, for example, can be separated into three zones: littoral zone, limnetic zone, and profundal zone, according to zonation. Different types of species can be found in each zone.

Natural Climax communities typically have some stratification, in which the community’s populations are divided into specified vertical or horizontal strata. Stratification is the most common structure. Various strata could occur as a result of the evolution of different animals. For example, the sea could be divided into upper and lower strata. Autotrophs often dominate the upper layer, while heterotrophs dominate the lower stratum.

7. Ecotones: Communities come in a variety of sizes, and their boundaries are frequently ill-defined. An ecotone is a zone in between two biomes where communities meet and possibly merge. The presence of an ecotone can help identify adjacent communities. An ecotone is a line that separates two communities. Because it is frequently in a transitional condition, it is more likely to be denser and richer than the two adjacent communities. Edge species are those that live near the ecotone and are therefore restricted. Ecotones include streams that pass through a meadow and estuaries where rivers meet the sea.

Importance of Community:

• The importance of community is that it allows species to interact.
• Nutrition is one of the many reasons that species interact within a community. Creatures, for example, are unable to produce their own food and must depend on plants and other animals for survival. Photosynthesis, on the other hand, is how plants generate their own food.
• Plants depend on animals as one of the primary producers of carbon dioxide. In mammals, this gas is emitted as a waste product of metabolism.
• Plants require carbon dioxide as a chemical reactant in the process of photosynthesis. In exchange, they emit oxygen, which the animals use to meet their metabolic needs.
• Members of the community may also provide a safe place in addition to food.
• A tree, for example, can support a variety of species, including epiphytes, lichens, insects, and arachnids.