What Is The Role Of Plants In The Cycling Of Carbon In The Terrariums?

Terrariums are miniature indoor gardens enclosed in glass containers. They create a unique, self-sustaining ecosystem that highlights the essential role plants play in the carbon cycle.

The carbon cycle refers to the continuous movement of carbon atoms between the atmosphere, land, plants, animals and oceans. Plants, through photosynthesis, absorb carbon dioxide from the atmosphere and convert it into energy and oxygen. The carbon becomes part of the plant structure. Plants also release carbon back into the air through respiration and decomposition. This cycling of carbon allows ecosystems to maintain a balance.

In a terrarium, plants are the primary drivers of the carbon cycle. They uptake carbon dioxide and release oxygen through photosynthesis, store carbon in their tissues, and produce carbon dioxide through respiration. Their key role makes plants essential components of an enclosed terrarium environment.


Plants play a critical role in the carbon cycle within terrariums through the process of photosynthesis. During photosynthesis, plants use energy from sunlight, water, and carbon dioxide to produce glucose and oxygen. The chemical equation for photosynthesis is:

6CO2 + 6H2O + Light → C6H12O6 + 6O2

This shows that plants take in carbon dioxide (CO2) and water (H2O) and use energy from sunlight to convert these into glucose (food) and release oxygen (O2) as a byproduct. The absorption of carbon dioxide and release of oxygen is key to regulating carbon levels in a contained ecosystem like a terrarium.

Within a closed terrarium, plants will take in carbon dioxide produced by animals and microorganisms breathing and decomposing organic material. The plants use this carbon dioxide in photosynthesis, incorporating the carbon to build new plant structures and biomass. This helps regulate and recycle excess carbon dioxide in the terrarium’s atmosphere.


Plants need to undergo cellular respiration just like animals in order to produce energy. During this process, plants take in oxygen and release carbon dioxide. Cellular respiration occurs in the mitochondria of plant cells. Through a series of chemical reactions, glucose from photosynthesis is broken down, and energy is released. Oxygen is used to break down the glucose, and carbon dioxide is produced as a byproduct.

The carbon dioxide released during plant respiration is one way that carbon is cycled back into the atmosphere from plants. This allows plants to maintain a balance of carbon so they don’t accumulate too much through photosynthesis. The amount of carbon dioxide released through respiration is much less than the amount taken in during photosynthesis. But over time, the combined respiration of many plants returns significant carbon to the atmosphere.

In a closed system like a terrarium, the carbon dioxide released from plant respiration can build up. But terrariums are designed to allow for gas exchange, so the accumulating carbon dioxide can escape into the outside air. This gas exchange helps maintain the carbon balance within the enclosed ecosystem.


Decomposition is a key process in the carbon cycle within terrariums. As plants die, the organic matter begins to be broken down by decomposer organisms like bacteria and fungi. These decomposers feed on the dead plant matter and break it down through metabolic processes that release carbon dioxide (CO2) gas back into the air.

The exact decomposition process depends on factors like temperature, moisture, and oxygen levels within the terrarium. But in general, as the plant tissues are broken down, the stored carbon compounds are oxidized and release CO2. The structure and composition of the plant matter, such as the lignin and cellulose content, impact the rate of decomposition.

Therefore, decomposition facilitates the movement of carbon from solid organic matter back into a gaseous state. The CO2 released can then be reused by live plants in the process of photosynthesis. This cycling of carbon between plants, decomposers, and the atmosphere is essential for sustaining life within closed systems like terrariums.

Managing decomposition through proper terrarium design, plant selection, and maintenance helps ensure the carbon cycle continues uninterrupted. Dead plant matter that accumulates without fully decomposing can tie up carbon and prevent it from being cycled efficiently within the terrarium environment.

Carbon Sinks

Plants act as carbon sinks by absorbing and storing excess carbon through the process of photosynthesis. During photosynthesis, plants use sunlight, water, and carbon dioxide to produce carbohydrates for growth. However, plants often absorb more carbon dioxide than they immediately need. The excess carbon is converted into sugars and starches and stored within the plant tissues.

Trees and other woody plants are especially effective carbon sinks because they continue to grow over many years, allowing them to sequester significant amounts of carbon in their trunks, branches, roots and leaves. For example, a single mature tree can absorb over 48 pounds of carbon dioxide per year. Much of this absorbed carbon remains locked within the tree’s woody biomass as the tree continues to grow.

Carbon stored within plants’ tissues remains sequestered from the atmosphere until the plant dies and decomposes. Therefore, preserving and planting trees and other carbon-storing plants can help mitigate climate change by removing excess carbon dioxide from the air.

Within a closed system like a terrarium, plants act as crucial carbon sinks by absorbing the carbon dioxide released through the respiration of animals and microbes. This helps maintain balanced carbon levels within the terrarium’s miniature ecosystem.

Oxygen Release

Plants release oxygen back into the terrarium through the process of photosynthesis. During photosynthesis, plants use energy from sunlight to convert carbon dioxide from the air and water into glucose sugars for growth. Oxygen is released as a byproduct of this reaction.

The photosynthesis chemical equation is:

6CO2 + 6H2O + Light Energy → C6H12O6 + 6O2

This shows that for every 6 molecules of carbon dioxide consumed, 6 molecules of oxygen are released. The oxygen gas produced is released through the leaves and stems of the plant, entering the air within the enclosed terrarium. This contributes to refreshing and renewing the available oxygen supply for any animals that inhabit the terrarium.

Having actively photosynthesizing plants is crucial for maintaining adequate oxygen levels within the closed system of a terrarium. The plants continuously replenish the oxygen during daylight hours through photosynthesis. This oxygen release helps sustain the respiration of animals and aerobic decomposition by bacteria within the terrarium’s ecosystem.

Carbon Storage

Plant tissues can store significant amounts of carbon over extended periods of time through the process of carbon sequestration. As plants grow, they absorb carbon dioxide from the atmosphere through photosynthesis. Some of this absorbed carbon gets incorporated into tissues like stems, roots, leaves, flowers, fruits and seeds. The carbon stored in plant biomass can remain locked up for the lifetime of the plant.

Woody plants like trees and shrubs are particularly good at storing carbon long-term. Up to 50% of a tree’s biomass can be carbon. Large trees can store hundreds to thousands of kilograms of carbon in their wood. The oldest trees store the most carbon, as they’ve had decades or centuries to accumulate biomass.

In addition to above-ground tissues, plants also transfer significant carbon below ground. Up to 30-50% of the carbon fixed during photosynthesis gets transported to roots and soil. This carbon can persist in soils for decades to millennia if undisturbed. Root systems and fallen leaves continuously contribute organic carbon to soils through decomposition and root turnover.

Overall, terrestrial plants and soils play a crucial role in the global carbon cycle by sequestering atmospheric CO2. Plants act as carbon sinks, offsetting some of the emissions from human activities. Maintaining natural vegetation is important for mitigating climate change.

Terrarium Design

When designing a terrarium to maximize plant carbon cycling, there are several key factors to consider:

First, include a mix of fast and slow growing plants. Fast growing plants like ferns or moss will absorb carbon dioxide quickly through photosynthesis. Slow growing plants like succulents will store carbon in their tissues for longer periods. A diversity of plants ensures consistent carbon cycling.

Second, use activated charcoal in the soil mix. Charcoal has a porous structure that helps store and stabilize carbon from decomposing plant matter and prevent its release back into the air. Just a thin layer of charcoal powder or gravel in the bottom of the terrarium can make a difference.

Third, avoid overwatering or overcrowding plants. Excess moisture promotes bacterial growth which speeds up decomposition and carbon release. Allow room for each plant to grow to its natural size and open space for air circulation.

Fourth, open the terrarium lid occasionally to allow an exchange of gases. Stagnant air allows CO2 to accumulate and O2 levels to drop. Letting in fresh air simulates the gas exchange that happens naturally between plants and their environment.

Following these simple principles will create ideal conditions for your terrarium plants to absorb, use, and store carbon through their natural growth cycles.

Additional Factors

In addition to plants, there are other factors that influence the carbon cycle within a terrarium. A major one is microbes found in the soil. Fungi and bacteria help break down organic matter through decomposition, releasing carbon dioxide. The rate of microbial decomposition is affected by soil moisture and temperature. Drier and cooler soil conditions will slow the activity of microbes.

The amount of soil organic matter also plays a role. Soil with more decaying plant material supports larger microbial populations and higher CO2 release. Turning and aerating the soil allows more oxygen to penetrate, which can accelerate decomposition and CO2 production.

Furthermore, the configuration of the terrarium itself makes a difference. An enclosed terrarium with little ventilation will allow CO2 to accumulate to higher concentrations, while an open-air design lets gas exchange occur more freely with the outside environment. Consideration of these factors allows for greater control over the carbon cycle within a terrarium.


Plants play a crucial role in carbon cycling within terrariums. Through photosynthesis, they absorb carbon dioxide and release oxygen into the terrarium’s atmosphere. Respiration and decomposition further facilitate the movement of carbon between plants, animals, microbes, soil and the air. Plants act as carbon sinks, absorbing and storing carbon in their tissues. The carbon absorbed by plants is later released back into the environment when the plants respire, shed leaves/roots, or die and decay. The carbon storage capacity of plants regulates carbon dioxide levels and availability of oxygen within the closed terrarium environment. By designing terrariums with lush plant growth, the natural carbon cycle can be maintained in equilibrium. In summary, plants drive carbon cycling and create a livable micro-climate within terrariums through photosynthesis, respiration, and decomposition. Their role is vital for oxygen production, carbon sequestration, and sustaining life within these miniature ecosystems.

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