A closed terrarium is a self-sufficient ecosystem that is created inside a clear enclosed container replicating a piece of nature. It is built with substrate, natural materials and moisture loving plants. It is essentially a miniature ecosystem that is able to effectively sustain itself with almost no interference from outside. But have you ever wondered how a terrarium actually works? How is it able to sustain life inside an enclosed space without having access to the outside atmosphere? To know that we will have to first understand what plants need to survive.
They need sunlight, carbon dioxide, oxygen, water and nutrients to survive and all of these form part of the nutrient cycle that plants must have constant access to. Let us talk about sunlight which is a key energy source used by plants. We already know that we cannot subject a closed terrarium to direct sunlight. It will create an extreme greenhouse effect and kill everything that is alive inside the terrarium. Indirect sunlight can work but may not always be very effective. Artificial lighting is a much preferred way these days to provide light energy to plants in closed terrariums. As long as plants get sufficient light, be it from indirect sunlight or
artificial source, they will thrive. Photosynthesis is the process used by plants in which they use light, carbon dioxide and water to prepare their food. The carbon cycle and the water or hydrologic cycle comes into play here. Let us understand the carbon cycle first. Carbon is an essential element for plant growth and is cycled between the plants, soil and air in a closed terrarium just as it is in nature.
Let’s start with how carbon enters the terrarium in the first place. Carbon dioxide is present in the air and is taken up by the plants inside the terrarium through tiny openings on their leaves called stomata. Inside the plant, the carbon is used for photosynthesis to create glucose which is used for energy and growth. As the plants grow old and develop, they store carbon in their tissues. When the plants die or shed leaves, the carbon in their tissues is released back into the soil through the process of decomposition. In the soil, microorganisms such as bacteria and fungi break down the organic matter and release carbon back into the air as carbon dioxide. The carbon dioxide is then taken up by the plants again, restarting the cycle. The amount of carbon dioxide in the system remains constant and no new carbon is added or removed from the system. This means that the terrarium is entirely self sufficient and does not require any external inputs of carbon.
In a closed terrarium, the oxygen cycle is a natural process that occurs within the ecosystem of the terrarium. Plants within the terrarium produce oxygen through the process of photosynthesis, where they absorb carbon dioxide and water and convert it into glucose and oxygen. The oxygen produced by the plants and released into the environment is then reused by them during respiration. The oxygen is consumed via stomata and is used up by the cells in the leaves to disintegrate glucose into water and carbon dioxide. In terrariums, which houses animals like springtails and isopods, oxygen is also consumed by them as part of their respiration process. The water cycle, also known as the hydrologic cycle, is another important aspect of a closed terrarium ecosystem. In a closed terrarium, water is constantly cycling between the plants, soil and air, just as it does in nature.
Again, let’s start with how water enters the terrarium in the first place. Initially, the soil and plants inside the terrarium are moistened with water by the person who builds it. The moisture in the soil is then taken up by the roots of the plants, where it is used for various purposes such as photosynthesis, respiration and the formation of new cells. The moisture is returned to the air through the process of evapotranspiration. Evapotranspiration is the combined process of transpiration from the plants and evaporation from the soil. The water vapor in the air then condenses on the cooler surface of the terrarium container and trickles back down into the soil, continuing the cycle.
In a closed terrarium, the water cycle is a closed system. This means that the amount of water in the system is constant and the terrarium is entirely self-sufficient. However, it’s still important to monitor the amount of moisture in the soil to ensure that it stays at an appropriate level for the plants. If the soil becomes too dry, the plants may wilt and die. If it becomes too wet, it can lead to root rot and other issues. To maintain the proper balance of moisture, it’s important to choose plants that have similar water requirements and to monitor the soil moisture regularly during the first few weeks after the setup. Nitrogen is an essential nutrient for the production of amino acids, proteins and nucleic acids which are crucial elements for plant growth. Nitrogen gas is already present in the air inside the terrarium but it cannot be directly used by the plants.
However, some bacteria and fungi are capable of converting nitrogen gas into a form that plants can use in a process called nitrogen fixation. This nitrogen-fixing bacteria and fungi are present in the soil of the terrarium and they convert nitrogen gas into a form of nitrogen that can be used by plants, such as ammonium or nitrate. The plants inside the terrarium take up this nitrogen through their roots and use it for various purposes such as growth and formation of proteins and other essential compounds. In the soil, other bacteria and fungi break down organic matter and release nitrogen back into the air as nitrogen gas through a process called denitrification. It’s important to note that in a closed terrarium the nitrogen cycle is a closed system.
The amount of nitrogen in the system remains constant and no new nitrogen is added or removed from the system. This means that the terrarium is entirely self-sufficient and does not require any external inputs of nitrogen. The soil also supplies other macronutrients like phosphorus, potassium, calcium, magnesium and sulphur to the plants. In relatively small amounts the soil also supplies iron, manganese, boron, molybdenum, copper, zinc, chlorine and cobalt, the so-called micronutrients. These nutrients are absorbed by the plants and again when the shed leaves some of the nutrients are returned back to the soil and the cycle continues. While a closed terrarium is a self-sustaining ecosystem it may still require some maintenance. Over time nutrients can become depleted. To prevent this occasionally nutrients may be added to the terrarium and plants pruned to prevent them from depleting the nutrients too quickly.
In summary, a closed terrarium is a fascinating and self-sustaining ecosystem where plants, soil and air work together to cycle nutrients. By understanding how nutrient cycling works we can create and attain healthy and thriving terrariums that can bring a touch of nature into our homes.