Boundaries of Ecosystem

Introduction to the Boundaries of an Ecosystem:

This unit makes the ecosystem a specific entity (system). Boundaries of ecosystems are features of any entity. The ecological boundaries or boundaries of an ecosystem are the “outer envelope of an ecological entity such as individual, species, population, community or an ecosystem”. Cadenasso (2003) called them “the zone of contact that arises whenever an area is portioned into contrasting patches”. Krause referred to compartments in a food web as reflecting sutures (boundaries). These are actually “the locations exhibiting gradients of change in environmental conditions and a related shift in the composition of plant and/or animal communities”. Their presence and attributes affect neighboring areas or systems.

Ecologists have defined a community as “a group of organisms living in the same area at the same time”. However, where this area (space) begins or ends, is out of the definition. Boundaries of ecosystems always overlap each other. It is quite difficult to define exactly where it starts or ends. A big challenge in tackling boundary-related issues is the overlapping nature of the boundaries of the ecosystem. A boundary may contain other boundaries partially or fully. Such nested overlaps and shared boundaries are universal. This case is more obvious in Lake Ecosystem. Ecologists stop short of elaborating further on the concept of boundary maybe because they assume that boundaries of ecosystems are obvious but their selection was arbitrary and random.

Kinds of Boundaries of the Ecosystem:

Boundaries are where an ecological entity ends or two ecological entities meet. Ecologists have defined different kinds of ecological boundaries of ecosystem using the following approaches;

1. The steepness of the gradient and edaphic factors.
2. Amount of contrast and differences among adjacent patterns.
3. Different entities (factors or organisms) as owners of the boundary.

For density-dependent and density-independent factors of an ecosystem, click here;

Based on different aspects, there are the following kinds of boundaries of an ecosystem;

Cultural Boundaries of Ecosystem

Territorial Boundaries of the Ecosystem

Range Boundary

Factors like a geographical obstacle, availability of resources, historical pattern of migration, seasonality, etc, maintain these boundaries. Migration ranges are expanded to more than one ecosystem even, while some other factors may have a limited scale of range boundary.

Associative Boundary

Physical Boundary

These boundaries are among communities and ecosystems due to physical landscape features. These features may include topographical, hydrological, climatic, or geological ones. Such features lower the intensity of interaction among different communities. For example, pests of grassland are different from the aquatic ecosystem due to this physical barrier.

Boundaries of Ecosystem Complex

Functions of Boundaries:

All ecosystems connect to form Biomes. Adjacent ecosystems connect via flows of energy, material, and organisms across ecosystem boundaries. Boundaries play a vital role in governing and maintaining different mechanisms across different ecosystems. The functions of boundaries are as follows;

1. Boundaries govern the transfer of materials, information, and organisms from one ecosystem to another.
2. Transformation: Boundaries can be Oxic-anoxic (with a limited or ample supply of oxygen). Such kind of boundaries transform material moving entirely into a new form. For example, groundwater containing dissolved ammonia when moved to the top of the surface where there is plenty of oxygen available may transform into nitrate. Similarly, the soil crust transforms nitrogen and carbon dioxide into ammonia and organic carbon respectively.

• Permeability: They act as a filter by allowing some factors to enter a particular system while hindering others. For example, wind speed slows down when it crosses the boundary from grassland to forest. Tall and over-story trees reduce the speed of the wind. Similarly, animals are habitat-specific and are reluctant to cross boundaries and leave their habitat.

1. Absorption: Boundaries always absorb energy and matter approaching them. For example, wave energy is absorbed by the shore. The energy of moving water currents causes the erosion of the banks. All the materials contained within an aquatic ecosystem are deposited along the banks and shores.
2. Amplification: Sometimes, when materials move across the boundary of ecosystems, they absorb minerals. When water moves from a region containing sandstones to a region that has reserves of limestone, dissolved inorganic carbon (DIC) contents increase in water.
3. Reflection: These boundaries are also known as Hard Boundaries. They reflect any organism or material that approaches the boundary. For example, the sea shore acts as a reflector for fish as it moves back to the aquatic ecosystem from the boundary. In nature, biogeochemical cycles also follow this type of reflection and show cyclic movement.

• Neutral: Some of the boundaries are neutral and have no effect at all on matter and energy flowing across it.

Conclusions:

1. The boundary of an ecosystem can take a great range of forms and meanings. The term “boundary” is quite diverse.  It has different names like edge, ecotones, boundary layer, clines, interfaces, gradients, transition zones, sutures, etc.
2. Ecosystem boundaries are the locations exhibiting gradients of change in environmental conditions and a related shift in the composition of plant and/or animal communities.
3. The concept of the boundary of an ecosystem becomes clear only with the concept of a system enclosed (entity). The proper definition of a boundary is dependent upon the ability to define an ecosystem.
4. Depending upon the system, boundaries can be diffused or discrete. Any ecological system has definite boundaries among its components at different scales.
5. Naturally, occurring ecosystem boundaries can represent unique habitats. Many species adapt to these naturally occurring ecosystems.
6. Anthropogenically created ecosystem boundaries often support high species diversity. The combination of species present at the edges is very different from the one found deep inside the adjacent ecosystems.
7. Neighboring ecosystems experience flows of organisms, materials, and energy across the shared boundary.
8. Boundaries always appear at different scales in different ecosystems. Some ecosystems have shorter boundaries while some have broader ones.