The Role of Carbon in the Soils of Massachusetts

By Brianna Nece

As a part of the natural carbon cycle, carbon is transported through five major pools: oceans, biomass, soils, fossil carbon, and the atmosphere. The majority of carbon is stored within the oceans, while soils contain only about 5 percent of the global carbon. Several factors can contribute to soil carbon fluxes, either through natural or human influences. To first understand carbon fluxes, we should begin with the basics of how soil processes organic carbon.

Plants play an important role in processing carbon. Plants take up carbon dioxide from the atmosphere through the stomata found on their leaves. They recycle carbon dioxide into various foods like sugars, lignins, and fibers. There is about 10 to 40 percent that exists through the root system to nourish soil microbes. Naturally, the roots and leaves in plants will decompose over time. When roots secrete, there can be carbon that flows out that can be returned to the atmosphere or remain in the soil and turn into organic matter. About 57 percent of Earth’s carbon comes from organic matter. Soil organic matter has the equivalent of about one ton to 3.677 tons of carbon dioxide. There is an annual increase in soil organic carbon due to biosequestration found within ecosystems such as wetlands, forests, and grasslands. However, when ecosystems become saturated, they are no longer able to do carbon sequestration since they cannot gain new carbon. Each ecosystem has varying levels of saturation based on the climate and soils. Soil type matters for retaining carbon. In clay and slit soils, they have a higher surface area, meaning they are able to retain more carbon due to their smaller particle size. Sandy soils, on the other hand, have a much higher particle size; so, they have a small surface area and cannot retain as much carbon. There is at least one ecosystem that has an outlier to this rule, and that is wetlands. Wetlands are a good source of continuous carbon sequestration because having wet soils allows for aerobic decomposition to occur. Most of Massachusetts has been historically altered and cleared to the point that soils are not saturated to the extent of constant carbon sequestration. These historic alterations are important when it comes to planning for the future. 

It is important to note the changes to soil organic carbon stocks when it comes to gathering information for the Massachusetts Healthy Soils Action Plan. To make a change for the future, there needs to be a baseline understanding. The soil organic carbon stocks stand evaluated at 383 million tons, which is equivalent to 1.4 billion tons of the total carbon. The baseline estimate of carbon dioxide through natural sequestration by 2050 is 2.1 million tons. However, if the sequestration rate is increased or preserved, this means there is still 14 million tons of additional carbon dioxide demanded to accomplish decarbonization. Soil organic carbon stocks can change as a result of several different factors. Things like natural disasters, such as fire or drought, can reduce the soil organic carbon available. Climate change is also a great reducer of carbon availability due to shifting climates, sea level rise, and extreme weather. Human activities degrade carbon sequestration through land development. When a natural forest is cut down and laid with concrete, carbon is no longer being filtered from the atmosphere through plants into the soil. Nevertheless, it does mean that the opposite can also be true. Properly managing land can also mean increasing the soil organic carbon available. Best Management Practices came to be as a result of their good stewardship of untouched and operating lands. These practices have the potential to help improve carbon sequestration. These different effects on carbon sequestration were considered as part of different scenarios put together to help build an understanding and work towards an action plan. Some results indicated the importance of carbon storage available within soils, so a major goal for the plan is to maintain as much soil from land coverage as possible, especially for wetlands, since they can store more carbon than average soils. Additional use of Best Management Practices that support more carbon sequestration is critical.  These strategies are meant to help spark change in municipal and statewide policies for more research and implementing better practices. The hope is for Massachusetts soils to play a bigger part in accomplishing the objective for zero emissions by 2050. To accomplish these objectives, some themes emerged as a part of the process. 

There were three themes associated with this action plan set in place by Massachusetts. These themes were restoration, regeneration, and stewardship. The restoration aspect is about mending the land and soils to what they once were. This could mean the return of fundamental functions that have been lost to ecosystems for centuries because of degradation. The regeneration aspect is to achieve an ecosystem that is functioning with a higher resilience to degradation. Regeneration varies with restoration since it does not necessarily aim to restore land to the initial historical value. The stewardship aspect is the overall management and care for all of the different land types. The purpose is to be able to strive towards strengthening regeneration and restoration practices that can be measured over time. This also means more encouragement for stewardship among landowners. If it were supported by the local and state administrations, landowners could receive tax credits for assistance or allowance. Some of these themes can be found by looking at various management practices. 

Good management practices are important for helping prevent climate change and carbon loss. In forest management for Massachusetts, there are several different practices at play. One strategy is to try to avoid forest loss, such as not altering land for residential use or restoring forest damage. Another strategy is eliminating carbon emissions that are lost during drought, pests, wildfire, or unstable forest practices that cause more tree loss. The other part of this strategy is increasing carbon sequestration through having tree expansion or more carbon being transmitted into long-term carbon pools in forests. These strategies may also involve heavy regeneration being executed for forest enhancement. These strategies can also be implemented for landowners. They can help manage their land for healthier forests through diverse habitats. Landowners can take steps to remove invasive species and do their best to guard the soil and water that is available. These practices are meant to help landowners maintain and increase their carbon stocks, so a management plan that is more climate-informed is important. Understanding the different land cover types helps to form Good management practices.

Forests are just one type of land cover that is addressed in the Massachusetts Healthy Soils Plan. There are several land covers addressed to help build a comprehension of the climate change effects on soils and carbon. One of the bigger takeaways from understanding each of these land types is good land management. Landowners play a significant role in helping to maintain healthy soils and carbon sequestration. However, these findings are meant to be encouragement for more involvement beyond landowners. We all have a responsibility and a role to play in our changing environment.

Citations

1. Commonwealth of Massachusetts (2023). The Healthy Soils Action Plan. https://www.mass.gov/info-details/resilient-lands.

2. Managing forests for carbon in Massachusetts. https://www.massaudubon.org/content/download/62444/file/MassAudubon_Carbon-Guide_Digital.pdf.