Ed Golson Outdoor Education

succession

What would happen if a farmer simply abandoned one of his fields to see what would happen? Would the field remain barren forever simply because no one would be around to plant crops on it? Of course not. The field would become overgrown with weeds and other wild plants within a year. It wouldn't stop there. The field would undergo a nonstop process of predictable changes called succession. Let's take a closer look to get a better understanding.

The field starts out barren. With no plants to block the wind, many plant seeds have a hard time taking root. With few plant roots holding the soil in place, erosion is a constant threat. There are virtually no animals in the field because it lacks any sort of food or shelter. However, some hardy grasses and weeds would soon find their way to the field. These first plants to grow in the barren field are called pioneer plants . They are specially adapted to the harshest environments.Once these plants take hold, they will thrive because they don't have to worry about competition from other plants. They could reproduce very quickly and cover the entire field before long. Small animals like field mice and ground nesting birds would soon come back to take advantage of the new habitat.

After a few years, the wind will be less of a problem because it will be blocked by all the weeds. Erosion will be much less of a problem because all the plant roots will hold the soil in place. Plus, all of the dead plant material that has built up over the years will make the ground more stable and suitable for different types of plants. Soon, shrubs (like dogwood) and small trees (like aspen) will take root in the area that used to be the field. They will grow bigger and taller, shading out the weeds that are around them. Animals like robins and chipmunks will soon make their home in this changing habitat. Many new species of both plants and animals will find their way to the old field.

As the years go by, most of the grasses and weeds in the field get replaced by shrubs and trees. As more trees enter the area, competition for light starts becoming an even bigger issue. Taller trees will be able to get more sunlight and will have a big advantage over the smaller shrubs. Animals like turkeys, squirrels, and deer start to move in. Soon, the area begins to look a lot more like a young forest than an old field.

As this new "forest" ages, the competition for light becomes the biggest issue for plants. Trees that are more tolerant to shade or grow the fastest and tallest as seedlings will have the advantage. Many of the smaller trees won't be able to keep up and will eventually die off. Within a few years (or more likely decades), the area will be dominated by the larger trees like oak and maple . Throughout most of Michigan, this type of forest is the climax community- meaning that it is the most stable environment and the end of most types of succession in our area.

Unfortunately it's not always that simple...

Of course, this is only one type of succession. Not all areas will have the same steps or the same type of climax community. Some areas will have grassland as their climax community. Others might have a pine forest. Succession also occurs in aquatic habitats. A nearly empty pond may fill up with different species of plants and animals. Or it may eventually fill in with plant debris and silt to the point that it eventually becomes soggy land. Succession is merely the process that nature goes through to get back to normal after something changes.

You should have noticed that during succession, the types of plants and animals in the area are constantly- and slowly- changing. Species that are important or even dominant in one stage may be totally eliminated during a later stage. Some types of living things can live throughout many different stages of succession while others may only be able to live during one specific stage. The easiest way to tell what stage of succession an area is in is to look at the plants and animals are in it.

This whole process from abandoned field to full fledged forest can take up to 200 years- and that's assuming no major disturbances come along and set the whole process back. In fact, many areas face so many different disturbances that they never reach their climax community. A common example of this is the farmer that plows his field every year. By turning over the soil before wild grasses and weeds can take over, the farmer is preventing succession from getting very far.

Another important example of disturbance is a forest fire. Many areas of the state naturally had a large number of forest fires even before European settlers came here. These fires prevented the climax communities from taking over. As a result, those areas were filled with many unique plants and animals specifically adapted to deal with the constant threat of fire.

But when humans started suppressing all the forest fires, the climax communities started taking over again. Many of the plants and animals that had adapted to the fires became endangered or even extinct. In order to reverse the damage, biologists are often now starting controlled fires to prevent the climax communities from taking over. By creating artificial disturbances, we can control the process of succession to maximize the health of the overall environment.

Local Succession

Do you think that Bay City, Michigan has changed over the past 100 years? Compare the two pictures from 1918 to 1997. What differences can you find? Has it stayed the same in any ways?

What causes Earth to change over time? One of the main reasons Earth changes is due to a process called, "succession". There are two types of succession. The first one is primary succession, which is the beginning growth of an area where there has never been growth before. The second form is secondary succession, which is land that has been colonized before it returns back to its original state.

Primary succession began which resulted in pioneer (native) plants growing in Bay City. The pioneer plants added organic material to the soil, and helped to keep the soil in place and prevent erosion. These plants were able to live in areas that did not have good soil because they were easily adaptable and hardy. As conditions changed, other plants were able to colonize this area. Plants continued to recycle and reproduce themselves and this is known as a "climax community".

Bay City had a climax community (large areas of forests) in effect long before humans arrived. The first humans were hunters, gatherers and farmers and were able to settle in amongst the trees and nature. As our needs changed, however, (our population increased and became industrialized), some of the climax communities were cut down and paved over in order to create room for our changing lifestyle. This change took place within a span of about 100 years. Remember that wood is a renewable resource.

The river became a water highway that transported things such as lumber, furs and other goods. Portions of the frozen rivers were cut up into blocks of ice. This ice was used to refrigerate (preserve) food during the summer and fall months. As technology improved so did the way we used the environment. People looked for new ways to improve our life and make it easier. Refrigerators were an invention that could now preserve our food and we no longer had to use blocks of ice in "ice boxes". The river system no longer had to be used as a primary means to transport lumber from town to town as it was put onto new products called trains, trucks, and ships. How the river is used has also changed over time. Once it was used primarily as a water source for crops and animals and as a highway made of water that transported goods and services. We continue to use the river in the ways it has always been used, but we also use it in a variety of new ways. How do you use the Saginaw River and our Bay?

1918 River Entry

1998 River Entry

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