Air pollution is increasing daily, and this happens because some of our activities will produce carbon (CO2) exhaust substances. People and institutions have made several efforts to reduce air pollution by reducing energy use, using electric vehicles, and CO2 storage through forestry and agroforestry. Among all these techniques, agroforestry is recognized as an important way to reduce CO2 emissions and increase carbon storage. Given the importance of agroforestry in carbon storage, researchers from the Universitas Sumatera Utara, Latifah, and colleagues conducted a study on species diversity and carbon storage in agroforestry systems in special purpose forests in Aek Nauli, North Sumatera Province, Indonesia.

It should be noted that there has been a lot of research on CO2 storage in Indonesia but not much on biomass and carbon storage in special-purpose forests with agroforestry systems with conservation value and economic functions. For two reasons, agroforestry can store large amounts of carbon. First, current crop and pastoral systems cover large areas. Second, although carbon storage density is low compared to forests, woody biomass from agroforestry systems can provide a local fuel source. This fuel will reduce pressure on the remaining forests in the area and serve as a substitute for fossil fuels. This consequence is important because the most effective strategy for using land for atmospheric carbon stabilization is to substitute woody fuels for fossil fuels rather than reforestation.

The study measured the number of individuals of each understory species and litter in various research plots. Biomass and carbon storage measurements were conducted regularly for two months, from April to May 2016. Tools used in this study include recording sheets, digital cameras, raffia, GPS (Global Positioning System), compasses, wooden or bamboo sticks, machetes, and wooden squares. The materials used in this study were T. sureni, P. merkusii, and Arabica coffee.

T. sureni and P. merkusii were planted at a 3.0 x 2.0 m distance, while C. arabica and P. merkusii were planted at a distance of 3.0 x 3.0 m. T. sureni is 14 years old, C. arabica is 4-5 years old, and P. merkusii is 12-14 years old. The rainfall in the Aek Nauli region belongs to Type A, with an average rainfall of 2199.4 to 2452.0 mm and an average monthly temperature of 23 to 24°C. The research plots were randomly selected to avoid bias and ensure that the data obtained represented the actual conditions in the field. According to the plant species in the agroforestry system, a total of 6 plots measuring 20 x 100 m were installed. Plot placement was done by systematic random sampling. Ten 1.0 x 1.0 m subplots were used for each sample plot to measure species diversity, biomass, and carbon storage of understory and litter species.

The study showed that agroforestry with T. sureni had higher understory species diversity than agroforestry systems involving P. merkusii. The researchers stated that the diversity of understory species in the T. sureni agroforestry system was very diverse, indicating that the system could support more plant species. T. sureni, also known as Suren or Toon, is a tree often recognized for its rapid growth and tolerance to various soil conditions. This high diversity of understory species suggests that T. sureni provides a more favorable environment for other plant species than P. merkusii or red pine.

In addition to species diversity, the study also showed that agroforestry with T. sureni had higher biomass and carbon storage capacity. Researchers found that systems with T. sureni stored more carbon, essential for climate change mitigation. Higher biomass means more carbon is absorbed and stored in living plants, which helps reduce the amount of carbon dioxide in the atmosphere. The higher carbon storage in agroforestry with T. sureni shows the great potential of this system in contributing to global climate change mitigation efforts.

Agroforestry offers many environmental benefits, including carbon storage, biodiversity maintenance, and soil erosion reduction. In addition, agroforestry also provides economic benefits to farmers by providing additional sources of income through non-timber forest products and other agroforestry products. Agroforestry can be integrated with national and international environmental policies to mitigate climate change. Governments and international agencies can incentivize and support farmers to adopt agroforestry practices. In addition, further research is needed to develop more efficient methods of measuring and monitoring carbon storage in agroforestry systems.

In general, agroforestry is a vital strategy to address deforestation and land degradation and improve agricultural sustainability. By selecting appropriate tree species, such as T. sureni, farmers can increase carbon storage efficiency and support biodiversity. Good agroforestry practices can provide sustainable solutions to environmental problems like deforestation and land degradation and contribute to climate change mitigation.

Agroforestry's large potential for carbon storage plays an important role in climate change mitigation. This study shows that agroforestry systems in the Aek Nauli special-purpose forest can store large amounts of carbon in the form of below-canopy biomass and litter. Integrating agroforestry with environmental policies can help achieve climate change mitigation and biodiversity maintenance goals.

Further research and government policy support are needed to optimize agroforestry's potential for mitigating climate change and providing economic benefits to farmers. With the right approach, agroforestry can effectively address climate change challenges and promote environmental sustainability.