Ecological Succession | amur-leopard

Ecologicial Succession (Temporal Changes)

In order for ecosystems to become stabilised, they have to go through an Ecological Succession. A succession is where gradual and natural changes occur within a given ecosystem, altering the environment and influencing the species of organisms that reside within them (Sahney and Benton, 2008).

Succession can occur in two forms; Primary succession and Secondary succession.

Primary succession is the beginning of changes within an environment without soil, such as barren environments including rocky crevices and volcanic areas. The lack of soil make a suitable environment for biotics that can survive without the need for soil, such as a symbiotic species known as Lichen; Lichen grow along rocks and trees and break down matter into nutrients (Biology Online, 2011). Lichens and other similar organisms can be known as pioneer species; these are usually opportunistic and are the first organisms to settle within new environments (Matthew, 2014).

Lichen grow across the rocky landscapes and breaks the rock down into smaller graduals. This process of gradual breakdown of rock is assisted through factors that change and alter ecosystems, such as weather, erosion and corrosion of stone. When Lichen dies, it rots and becomes nutrient-filled soil, which begins to develop around the other growing Lichen. This eventually builds up and bulks out into a thin layer of soil across the rock, giving the land the opportunity to pocket seeds from small plants.

Simple plants (plants who need little to survive) such as ferns and mosses are then able to grow within this new pocket of soil. Lichen continues to spread across the surface of rock and continue the process until there is more soil-based land, and further spreads the areas for plants to grow. The simple plants begin to die off and regrow, decomposing into the soil and making the soil richer in organic matter and nutrients. This also layers up the soil until it begins to thicken further, allowing growth for larger plants (Walker, 2011).

Plant seeds need to be deposited successfully within the soil; simple plants usually spread their seeds through the wind where they occasionally land within the stable soil. The introduction to new plants encourages the arrival of birds and insects; birds migrate from other locations and bring their stomach contents with them; when they defecate they release eaten seeds and new plant species are introduced within the new area. If a plant is unsuccessful at growing in the new area (as it may be too large for the shallow layer of earth) it would die and add more matter to the earth, further assisting in the soil development (McClanahan, 1986).

Eventually, the soil layer thickens enough for grass and wild flowers to take residence, which encourage the arrival of more insects and smaller organisms begins to flourish. These continually die and regrow, further adding to the soil layer until eventually, tree saplings will have the ability to stay rooted and supplemented in the new area. Trees begin to grow all over, bringing the ecosystem new food, shelter, and habitats for other species. Small mammals and other species migrate into the area, allowing the ecosystem to begin stabilising and reducing in change (see figure 21). When the ecosystem is stabilised, it will end as a Broadleaf Forest; this is known as a Climax Community (Pidwirny and Jones, 2009).

Figure 21. The process of primary succession (Britannica, 2006).

A Climax Community is the final stage of the succession process; where the environment settles into a predictable environment with little to no changes (Hogan, 2012).

Secondary succession is the beginning of environmental changes in an area that already has soil and previously held other organism species. This occurs in environments that have been destroyed through factors such as floods, storms, volcanic eruptions, and overall scarring of the environment that leaves it inhabitable for species (Baldocchi, 2011). Secondary succession is a much speedier process than primary succession because it already has the previous nutrients from its last Sub-Climax Community (see figure 22).

Figure 22. The process of secondary succession (Britannica, 2006).

Sub-Climax Communities are the stages of different ecosystems that lead towards a succession; but are still undergoing changes that are needed in order for the ecosystem to meet Climax community standards. An example of a Sub-Climax community includes Moorlands and Prairie Lands (Godwin, 1929).

Succession not only occurs terrestrial, but also in aquatic circumstances. A body of water can develop into solid land and an eventual broadleaf woodland; this process is known as Hydrosere (Offwell Woodland & Wildlife Trust, 2000).

Similar to terrestrial succession, the development of soil is the main factor of development. The speed of succession can be effected by various external factors, including pollution levels, weather, and natural disasters (Brown, 1997).

Hydrosere occurs when plant matter and organisms decay at the bottom of ponds and pockets of water. Their remains build up as sediment and increase the build-up of soil. When ponds develop enough sediment they become wetlands. Wetlands are essential for migrating wading birds who heavily depend on the organisms found within the ecosystem. The water is shallow enough to be waded through but deep enough to contain organisms to forage on. Wetlands will continue to build-up sediment until it becomes a marsh. Further soil development will succeed further into a carr. This damp unsettled land is important for developing larger plant organisms such as willow trees. Eventually, the soil formation solidifies into stable land until a broadleaf woodland can grow and reach its Climax Community (see figure 23) (Tutin, 1941).

Despite all successions leading to similar based environments, it is important to prevent this from occurring. Sub-climax communities have the greatest diversity of species within their habitats more than climax communities. Succession of the land also results with both local and global extinction of species. Without the wetlands, migratory birds would not have anywhere suitable to sustain themselves and would likely die out.

In order to prevent the wetlands from succeeding into a woodland, management strategies can be implicated by humans.

These can include:

Dredging (Dennis et al, 2013)

Sediment and soil is removed to prevent build up from occurring.

Tree Removal (Boreham, 1989)

Trees are removed fromthe environment to prevent anchoring and stabilising the ground. These can be removed by hand (sawed trees), by machine (deforestation), and by introducing grazing animal species to eat any sprouting plants.

Education/Conservation (Northeast Forestry University, 1990)

Spreading awareness of the environment and its effects on the ecosystem and educating the public on how to assist maintenance. This also introduces public involvement within activities such as creating visiting centres and boardwalks.

Boardwalk inclusions (Jackson et al, 1988)

Introducing boardwalks to allow travel without the need of constructing paths or levelling the land.

Flooding (Krausman and Leopold, 2013)

Diverting excessive water into an area to prevent soil from stabilising and maintain a wet environment. This is usually accomplished through rainwater drains.

Species Introduction (Toivonen and Meriläinen, 1980)

Introducing plant and animal species to prevent larger plants from growing and anchoring the soil into a stable area for trees to sprout.Animals are used to eat any sprouting plants and keep them trimmed and stunted.

Expansion (Klinger, 1996)

Digging edges of water areas and further removing soil build up. This also aids in the creation of river banks, which are used by aquatic organisms.

Restriction of Access (Walker and West, 1970)

Banning the public from entering the area and protecting the ecosystem from man-made pollution or tampering with the environment. This can be in the form of conservation and national reserves.

Figure 23. The gradual process of hydrosere (Weebly, 2015).

Ecological Succession of Primorsky Krai

Primorsky Krai is diverse in its ecosystems, holding a variety of both sub-climax and climax communities; providing diversity for species of organisms. Although it mostly consists of terrestrial (on land) succession, it also shows the process of aquatic (in water) succession (WWF, 2015).

Primorsky Krai is covered in 1000 miles of mountainous terrain known as the Sikhote-Alin Mountain Range, which seperates into a long expanse of water known as the Ussuri River. This is the main river that splits into other smaller rivers, including the Amur and Bikin River. There are an estimated 503.4 million Pinus Koraiensis (Korean Pines) and other broadleaf forests. The rivers eventually reach the Sea of Japan (Newell, 2004).

Pinus Koraiensis and broadleaf forests are examples of Climax Communities; where they have reached the final stage of their progression of growth. Containing unique species of flora and fauna, Primorsky Krai forests are common to set alight from forest fires; usually occurring once every 10 years. The last fire occurred in Slavyanka in 2009, burning forests to ash and killing organisms that lived there. Forest fires are one of the factors affecting the survival of Panthera Pardus Orientalis, further reducing the size of territory within the land (see figure 24) (Amur Leopard & Tiger Alliance, 2011).

The regrowth of these forests from natural fires are an example of Secondary Succession; the ash remaining from the fires have made the land rich in nutrients and aided in the regrowth of plants within the area. Although past plants and animals are lost, the reintroduction of new growth occurs frequently and with it returns any mobile organisms that immigrate back into the environment (Marietta, 2013).

Primorsky Krai

Figure 24. A map observing damaged lands caused from forest fires within Primorsky Krai (Wildlife Conservation Society, 2012).

In order to monitor and reduce fires within Primorsky Krai, Slavyanka Municipality and Wildlife Conservation Society have implemented various fire management preventatives including:

Mobile fire brigades for wild forest fires
Local fire wardens
Monetary fines for prosecutors deemed responsible for fires
Introducing firebreaks
Increasing awareness to the public
Improving training for field staff and agencies in charge of regulating fires (Wildlife Conservation Society, 2012).

A Sub-Climax Community of primary succession can be seen within the wetlands around Lake Khanka (Xingkai), which separates Russia from China. The lake is connected to 23 rivers, causing it to regularly flood into the remaining land. In order to aid the land into maintaining its wetland environment and preventing it from spreading into a larger drink of water, it is drained solely from the Song’acha River, which carries its waters into both the Ussuri River and the Amur River system. This provides access to aquatic biotics to migrate to and from the various rivers (Lake NET, 2004).

The wetlands surrounding the lake need to be maintained for the benefit of the diverse numbers of migratory bird species (see figure 25). In order to keep the area maintained, the Lake and its surrounding wetlands are now protected as the Ramsar Convention wetland site (Birkett and Mason, 1995). Not only this, but the area is left to flood regularly by the 22 rivers it is connected to, keeping the surrounding area a constant wetland. Due to being a restricted area, land development is banned in order to maintain it's sub-climax status and prevent it from succeeding into an eventual woodland, allowing for more diversity within the ecosystem.

Figure 25. Wetlands found in the West of Lake Khanka, Primorsky, Krai, Russia (Jonathan, 2014).