Natural succession is the process by which one type of ecosystem turns into another type of ecosystem.
An empty ecosystem – a patch of bare dirt – will be colonized first by whichever plants are able to arrive most quickly. The winners in this race are usually the kinds of plants that people call weeds – plants that are able to tolerate poor conditions, grow quickly, and make lots of seeds. Over time, however, other types of plants will arrive. The second wave is usually dominated by small perennials, with shrubs arriving next. Finally, trees move in, greatly altering the characteristics of the area by casting shade where previously there had been sun. Plants that arrived earlier in the succession are shaded out and are replaced by others that don’t need as much light.
While the details of this progression vary from one place to another, ultimately, almost any area capable of supporting trees will turn into a forest ecosystem. Why, then, do we find ecosystems other than forests?
The reason is that succession is not a linear process. Rather, it is a cycle. Ecosystems can be “reset” to earlier stages of succession when a disturbance eliminates the kinds of plants that characterize later stages of succession. A natural disturbance – such as a fire, tornado, or landslide – tends to knock down trees, creating opportunities for small, sun-loving plants to move back in.
The natural ecosystems of Wisconsin are a good example of this. Prairies and oak savannas remained largely free of tree cover because of regular disturbance by fire. Without these disturbances, southern Wisconsin would historically have been covered by forest.
For this reason, people often say that a prairie “needs” disturbance in the form of fire. This is true in the sense that a prairie would not continue to be a prairie in the absence of fire. Instead, it would become a forest – different, but not necessarily worse.
After a few more sightings, the bird observed a few weeks ago has been identified as a Northern Harrier.
Northern Harriers are a type of hawk. Like other hawks, they hunt for small mammals and birds to eat. The presence of a bird of prey means that there are enough of these small animals in the area to support a predator. It’s a sign that the local ecosystem is doing well!
Garlic mustard is a plant that tastes like it sounds. In its native range, it has been used as a cooking herb for centuries.
Its native range, however, does not include Wisconsin. Here, the plant tends to spread widely, and kill other plants. It does this by poisoning fungi that live in soil and benefit native plant species.
Garlic mustard is easy to recognize: it has fan-shaped leaves and small flowers with four white petals. Unlike dandelions, garlic mustard is easy to pull up. This is an effective way of getting rid of it.
After garlic mustard is pulled, it can be sent to one of three fates:
- If the area has not been treated with herbicides or other chemicals, the leaves of the plant can be eaten. They are delicious in salads and pasta sauces, or on their own!
- If the plant may have chemicals on it, but it has not yet flowered, it can be composted.
- If the plant may have chemicals on it, and it has flowered, it should be placed in the garbage. This is because the plant can finish setting seed after being pulled, and the seeds can survive the composting process, allowing more plants to pop up the following year.
The leaves of garlic mustard look like this:
The flowers look like this:
A group of plants looks like this:
Astronomically, spring comes to the whole Northern Hemisphere around March 21. The date of the spring equinox is determined by the Earth’s movements through space.
Meteorologically, however, the arrival of spring is related to local climate conditions. Winter can be said to end when the temperature rises above freezing and stays that way. Winter returns when temperatures again drop below 32 degrees Fahrenheit.
The days on which these events are likely to occur are called frost dates. The time between the spring frost date and the fall frost date is the growing season. Because these phenomena were important to farmers throughout history, the average frost dates for each area are well known. In Madison, the growing season runs from about May 20 to September 21. Frost dates for other locations can be looked up here.
Because of climate change, however, estimates of frost dates based on past weather are becoming increasingly unreliable. In general, growing seasons are becoming longer. Because a late frost can kill plants, though, it’s often best to err on the side of caution when beginning the gardening season.
Adding to the Sustainability Plan and the Pollinator Protection Plan, Madison is now working on an initiative to more effectively connect children with nature.
While Madison already has lots of urban nature – including more parks per capita than any other US city – these resources aren’t equally accessible to all kids. The new initiative seeks to start from what’s working and find ways to overcome obstacles.
The initiative is currently in a planning phase, with a written plan expected to be released in August. Those who are interested can get involved here.
While not all kids have a yard, those who do benefit greatly from having nature right outside their houses. Nature in the neighborhood is related to less childhood obesity, better functioning in kids with ADHD, and other benefits.
This is a picture of healthy soil.
A year and a half ago, though, it wasn’t soil at all: it was a pile of cardboard, paper, sticks, leaves, and old socks. After the pile was built, nothing further was done to it. Rain fell, worms arrived, and organic matter decomposed.
A core component of natural gardening is turning waste into resources, and letting nature do most of the work to make it happen. Now, instead of sitting in a landfill, the “waste” materials will be used to grow new plants.
Beyond the photo above are several more cubic yards of this healthy soil. Buying that much soil would have cost hundreds of dollars. With a little patience, it was instead produced onsite for free.
Natural gardening doesn’t lend itself to instant gratification, but it harnesses powerful processes that slowly and steadily produce great value.