Laying Fast Tracks Toward Climax Forests

Japanese ecologist and botanist Dr. Akira Miyawaki intended to restore ecological environments through understanding indigenous forest systems. He initiated numerous projects preparing climax-stage forests to emerge from disturbed sites within just a few decades. His surroundings as a teenager spurred this mission to complete a forest maturation process much more quickly than it usually occurs. Forest progression, called ecological succession, varies site by site, beginning with vegetation on bare ground and stabilizing in plant communities surviving a myriad of disturbances. Each naturally occurring successional stage may last for decades.

Climax expression may take a century and as long as 300 years on a site experiencing many disturbances along the way. An effectively permanent forest stage on one site may resemble that of a brief transitional stage on another.

Born in 1928, Miyawaki began college studies in Tokyo just as World War II was ending. He started graduate school at Hiroshima University soon after college in 1949 and focused on weed ecology in nearby war-devastated sites.  Insights gathered during extended field trials led to his developing a routine with common elements, even among sites of vastly differing challenges. He and his understudies took care to find patterns integral to each site's biotic needs. They selected species combinations they predicted as having climax potential and coined the term "Potential Natural Vegetation" (PNV). His prescription of soil preparation, species selection, and intensive care after planting led to interdependent forest function and became known as the Miyawaki Method. Practitioners called quasi-natural small groves cultured in this manner "small forests." Their accelerated complexity outpaced the results of conventional reforestation practices using simpler early-successional-stage species compilations.

How does one begin a restoration project? How does one know what species were present on a restoration site? How does one create the conditions for them to survive through future threats and disturbances? Recreating the infancy of a working forest system is much more complex than planting a landscape, even more than preparing a park or city of streetscapes. Forests are working systems comprising the interdependently functioning living and non-living elements. Interactions depend on the elements being adapted to each site's unique characteristics.

Dr. Miyawaki returned to Hiroshima after spending time studying forest growth in Germany to realize that historical forests were still present. As in many countries, ceremonial tree plantings had long been popular across Japan. For 1,500 years, when a forest was cleared to start a village, a forested shrine was preserved to honor guardian divinities. If no forest remained, the villagers created memorial groves around the shrine. These small forest systems and clues visible in artwork, folk remedies, and lore provided ecologists with the histories needed.

Miyawaki found that recreating the context of a forest begins with learning what the present site holds. What are the soil conditions, moisture, light, heat, and life inter-relationships? This takes time. However, as scientists, citizens, and resolute supporters take on the challenge, more information and advice become available.

Early lessons learned included knowing that plants commonly available are non-native, non-contributing, or are deficient in nutrient value for animal life present. They may grow quickly to dominate the site, but have relatively short lifespans, and eventually die out. Plants that do survive are those more shade-tolerant, that flourish with the provisions naturally on site, and live longer with disturbances absent. Disruptions such as fire, storms, flooding, and human intervention tend to restart the succession at an earlier stage or stall the system’s advance at a stage before climax.

After the study, site preparation is key. Miyawaki's field studies showed soil conditions, rather than climate, prevailed in driving site productivity. Soil testing is crucial, and sites often need the expertise of soil scientists. Most human-caused site disturbances compact soils. Following Miyawaki's recommendations, topsoil is usually specified to be prepared or added to depths from 7 to 20 inches. Such designed sites are often small, around 3,200 square feet or the size of a vacant building lot. Plants may be placed as densely as 3 feet apart, with species selected to occupy the crown, middle, and ground landscape layers. Mulch and protection from wildlife damage are critical. Dedicated watering, weeding, and tending are needed for at least three years. After that, the stands may become more resilient, influencing their own moisture and temperature regimes.

The Miyawaki Method offers a routine to regenerate forest systems in spaces available. Well-researched and conscientious establishment and tending only start the natural inter-relationships that develop through site maturation. If the first assessment is accurate, species selection is careful, and maintenance is diligent, nature may bring forested success. Along the way, all stages provide opportunities to educate mentors, youth, and students. As the forest matures, it will teach resilience and adaptation.

By 2014, at the age of 86 years, Dr. Miyawaki had led more than 3,000 planting festivals in eighteen countries, training others to prepare ecologically functioning groves. His species selections often met with disagreement from local populations. He maintained the position that conifers did not play a climax forest role on many Japanese sites. Opposing scientists argued that forest associations are dynamic, responding to invasive plants and pests or other disturbances. Others held that ecosystems present before human influence cannot be identified to be replicated.

Ecological functionality does not carry spiritual connotations, and the concept sometimes alienates values of spiritual forest enshrinement in Japan's landscape. Japanese tradition holds conifers as symbolic, spiritually and physically embodying continuity between the present and ancestral past. Tree planting decisions are prime examples of collaborations that turn culture into natural expression, concealing power relations and conflicts. Secular research-based recommendations are not accepted by all, and traditional landscape decisions continue alongside newly adopted changes. Having the final say provides the most powerful actors with legitimacy. Tree planting, while symbolic of community resurrection, hope, and harmony, also veils a spectrum of competing values, agendas, and societal consequences.

Resources

Lewis, Hannah. 2022. Mini-Forest Revolution. White River Junction, VT: Chelsea Green Publishing. 205 pp.

Miyawaki, Akira. 2004. Restoration of living environment based on vegetation ecology: Theory and practice. Ecological Research 19: 83-90.

Rots, Aike P. 2019. Trees of tension: remaking nature in post-disaster Tohoku. Japan Forum33(1): 1-24.

Urban Forests Company. 2020. The Miyawaki Method - Data & Concepts. 33 pp.