Miyawaki, Dense plantation, carbon sequestration, stem girth.

The scientific evidence warns that global warming is primarily caused by increased atmospheric concentrations of greenhouse gases (GHG), such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The anthropogenic rise in global surface temperature from 1850 to 1900 to 2010-2019 ranged from 0.8 C to 1.3 C, with a best estimate of 1.07 C. In 2019, global net anthropogenic GHG emissions were estimated at 59 ± 6.6 GtCO2-eq, marking an increase of approximately 12% (6.5 GtCO2-eq) since 2010 and 54% (21 GtCO2-eq) since 1990. The most substantial share and growth in gross GHG emissions were observed in CO2 from fossil fuel combustion and industrial processes (CO2-FFI), followed by methane, while the highest relative growth was noted in fluorinated gases (F-gases), which began from low levels in 1990 (IPCC, 2023). These changes have detrimental effects on global environments, including alterations in precipitation patterns, sea level rise, and an increased frequency and intensity of extreme weather events. 

Tree plantations are considered a strategy to reduce atmospheric greenhouse gas concentrations. In 2023, forests covered 713,789 sq km in India, accounting for 21% of the country's total geographical area, with a 19% loss of forest cover over the past 23 years (Geography Host, 2023). The reduction in forest cover in India has significant implications for biodiversity and ecosystem services (Veldkamp et al., 2020). To address this issue, the Indian government has implemented various afforestation and reforestation programs. However, the effectiveness of these initiatives in mitigating climate change and restoring ecological balance remains a topic of debate among environmental experts (Pérez-Silos et al., 2021). In recent years, the Miyawaki method of afforestation has gained recognition as a transformative strategy for establishing dense, biodiverse forests in limited spaces, thereby facilitating rapid ecological restoration and carbon sequestration. Developed by Akira Miyawaki, a Japanese botanist, since 1980, this technique is inspired by natural ecosystems and involves the dense planting of 15-30 different species in a relatively small area to enhance biodiversity. The Miyawaki method is characterized by its ability to create dense, multi-layered forests that mimic natural ecosystems. This approach entails the close planting of a diverse array of native species, typically 3-5 trees per square meter, promoting rapid growth and competition for light. The resulting forests are notable for their high biodiversity, improved soil quality, and enhanced ecosystem services, including carbon sequestration, air purification, and wildlife habitat provision (Briske et al., 2024; Nan et al., 2024). 

The method's success is attributed to its emphasis on site-specific soil preparation, the careful selection of native plant species, and intensive management during the initial years of growth (Farooqi et al., 2020; Moomaw et al., 2019; Wang & Huang 2020; Singh et al., 2023). The Miyawaki method holds significant promise for climate change mitigation. Forests established using this method can grow up to ten times faster and achieve densities thirty times greater than conventional plantations, thereby potentially sequestering carbon at a significantly higher rate (Wang & Huang 2020). Furthermore, the method's adaptability to diverse climatic conditions and its capacity to thrive in urban environments render it a versatile tool for ecological restoration and carbon offsetting across various contexts. As global initiatives to address climate change intensify, the Miyawaki method presents a promising approach for rapid reforestation and carbon sequestration, complementing broader strategies aimed at reducing greenhouse gas emissions and mitigating the impacts of global warming. However, there is a paucity of data regarding carbon pools in the above-ground and below-ground biomass and soil of young eco-forests established using the Miyawaki method. Further research is required to quantify the carbon sequestration potential of Miyawaki forests across different climatic zones and soil types. Long-term studies comparing the carbon storage capacity of Miyawaki forests with traditional reforestation methods could yield valuable insights for climate change mitigation strategies. Additionally, exploring the potential of Miyawaki forests to enhance biodiversity and ecosystem services alongside carbon sequestration could provide a more comprehensive understanding of their environmental benefits.

Objective. The primary aim of this study was to estimate the carbon stock accumulated within the biomass of various tree species and the extent of soil carbon sequestration in an eco-forest established using the Miyawaki planting method. By quantifying these carbon pools, this study seeks to enhance the prediction of climate impacts and improve our understanding of carbon cycling dynamics within rapidly growing and densely planted eco-forest systems. The Miyawaki method, renowned for its capacity to create dense, diverse forests in a short period, presents a promising approach to urban greening and carbon sequestration. The findings of this study could offer valuable insights into the potential of such eco-forests as nature-based solutions for climate change mitigation in urban areas. Furthermore, the results may inform urban planning and policy decisions regarding the implementation of Miyawaki forests as an effective strategy for enhancing carbon sinks in cities.

The site study, conducted from 2022 to 2024 at the Veterinary College and Research Institute in Orathanadu, Tamil Nadu, India, aimed to restore multi-layer natural communities and iv=ncreasing carbon sequestration potential using native tree species. The site's precise geographical coordinates (10°37'0.12″ N latitude, 79°16'0.12″ E longitude) locate it in the eastern region of the Tamil Nadu District. In 2022, a diverse selection of 16 plant species, including both fruit-bearing trees and ornamental plants, was introduced to the area. This selection comprised a variety of herbs, shrubs, and trees, with a total of 1,600 saplings planted. The chosen species included popular fruit trees such as Psidium guajava (guava), Syzygium cumini (jamun), Citrus limon (lemon), Annona squamosa (custard apple), Punica granatum (pomegranate), Phyllanthus emblica (Indian gooseberry), Artocarpus heterophyllus (jackfruit), and Mangifera indica (mango). Additionally, ornamental plants like Jasminum (jasmine), Hibiscus, Artabotrys hexapetalus (climbing ylang-ylang), and Nyctanthes arbortristis (night-flowering jasmine) were incorporated. To assess the carbon sequestration potential of these planted species, a carbon storage calculator was employed, utilizing measurements of tree circumference and dry weight, as recommended by Jones (2018). This methodology enables the quantification of carbon sequestered in the newly established vegetation, thereby providing essential data on the project's contribution to carbon sequestration and climate change mitigation. The planting initiative aimed to enhance biodiversity and establish a sustainable ecosystem within the campus grounds. Regular monitoring and maintenance were conducted to ensure the survival and growth of the newly introduced species. This restoration project not only serves as a valuable educational resource for veterinary students but also contributes to local conservation efforts and climate change mitigation. 

The carbon sequestration capacity of trees exhibits a significant trajectory of growth and variation over time. In the initial year, individual trees demonstrate a modest capacity, sequestering between 0.02 and 0.15 kg of carbon. However, this capacity expands considerably in the second year, ranging from 0.15 to 0.70 kg, with an average of 0.36 kg per tree. As trees mature, their carbon sequestration potential continues to increase exponentially. By the fifth year, individual trees can sequester between 1.5 and 3.5 kg of carbon annually, contingent upon species and environmental conditions. This rapid growth in sequestration capacity underscores the importance of long-term forest management strategies in maximizing the carbon mitigation potential of tree planting initiatives. A study by Stephenson et al. (2014) found that for 97% of 403 tropical and temperate tree species, mass growth rate increases continuously with tree size, contradicting the assumption that tree carbon accumulation peaks early in life. 

When converted to CO2 equivalent, the sequestration potential shows an even more dramatic increase, rising from 0.07 kg per tree in the first year to 2.60 kg in the second year. This substantial growth in carbon capture ability underscores the accelerating efficiency of trees as carbon sinks as they mature (Dold et al., 2019; Kathiresan et al., 2013). The total carbon sequestration potential in CO2 equivalent by the end of the second year ranged from 63 kg to over 1695 kg, depending on the number and types of trees involved. This extensive range underscores the substantial influence that strategic tree planting and forest management initiatives can exert on carbon capture efforts. Furthermore, the data indicates that as trees continue to mature beyond the second year, their carbon sequestration capacity is likely to further increase. This highlights the long-term advantages of afforestation and reforestation initiatives in mitigating climate change, underscoring the critical role that mature forests play in global carbon cycles and climate regulation (Domke et al., 2020; Li et al., 2023). The exponential growth in sequestration capacity from the first to the second year also underscores the importance of protecting young forests and ensuring their survival to maximize their potential as effective carbon sinks in the fight against climate change (Sun et al., 2024). 

Table 1: Calculations of Carbon Sequestration potential of various trees and shrubs.

The research identifies several areas for future investigation and application:

∙ Further Quantification: More research is needed to quantify the carbon sequestration potential of Miyawaki forests across diverse climatic zones and soil types.

∙ Long-term Studies: Conducting long-term studies to compare the carbon storage capacity of Miyawaki forests with traditional reforestation methods will provide valuable insights for climate change mitigation strategies.

∙ Comprehensive Environmental Benefits: Exploring the full potential of Miyawaki forests to enhance biodiversity and a broader range of ecosystem services, alongside carbon sequestration, will lead to a more comprehensive understanding of their environmental benefits.

∙ Climate Change Mitigation: The research contributes to a better prediction of climate impacts and an improved understanding of carbon cycling dynamics within rapidly growing and densely planted eco-forest systems, underscoring the Miyawaki method's role as a vital tool for ecological enhancement and climate change mitigation.

∙ Soil Carbon Dynamics: Deeper analysis into the below-ground biomass and soil carbon sequestration within Miyawaki eco-forests, as comprehensive data in this area remains limited.