What to keep: Retention forestry for Hiromachi Ryokuchi Forest 広町緑地

 

Let’s return to the crossing where we entered Kotakegaya Valley 小竹ヶ谷 at the forest of Japanese lacquer tree. This time we take the road to the south. This route brings us Takegaya Valley 竹ヶ谷. In Japanese, prefix “ko” can mean “small.” So, I surmise Takegaya Valley was thought larger than Kotakegaya Valley when people named the place millennium years ago. Indeed, the size of the valley to this direction is definitely bigger and the stream we walk along is longer than that for Kotakegaya. After a bit of stroll on an ordinary country pass, we enter a well-maintained boardwalk. The Vally is a good-sized wetland in which casual visitors need elevated route to ramble. The walk is roughly 150m long and both sides of it show various kind of vegetation changing its face from season to season. Beneath the board, there are streams and ponds where aquatic creatures, like larva of fireflies, live.

The beginning of the Takegaya Valley

The stream in Takegaya Valley has a good amount of flow.

Especially during winter,
volunteers do repair work for ponds in Takegaya Valley.

The well-maintained boardwalk

The bog seen from the boardwalk in winter

When we enter the forest from this direction, it becomes clearer the impression of “lots of trees” we had when we proceed along the farming area (; my post last week). Of course, the ecosystem of natural wetland gives us more diverse living things compared with dry-land forests. But I think it’s not only for this reason, but also from the surrounding forest itself. Strangely, even comparing with celebrated Koajiro Forest (; my post on July 15, 2016), the forest of Hiromachi Ryokuchi looks having more mixture of vegetations. Geologically speaking Koajiro and Hiromachi stood on the same Miura Group. At least the dryland part of the environment for both Koajiro and Hiromachi forests could be more or less the same. But …

The forest surrounding the Valley
looks biodiverse in Hiromachi Forest.

The recent scenery from Koajiro Forest.
During winter we can easily notice
 some places of the forest is getting dry,
and sasa bamboos easily start dominating the site.

Yeah, I do not know scientific research done for these places measuring biodiversity. My intuition in this post is purely from my subjective feeling. To be fair for Koajiro, it is still suffering the aftereffects of 3.11. tsunami that attacked the place 14 years ago. The killer wave entered deep inside the wetland of Koajiro, swept some vegetations stood at the rim of the marsh. In addition, the Koajiro is damaged by rampant oak tree wilt that has made gaps in the forest spreading along the boardwalk. Still, it might not explain everything. The keeper of Koajiro Forest, NPO Koajiro Field Activity Coordination Conference 小網代野外活動調整会議, heavily engineers the water flow of the Koajiro in order to maintain the size of wetland. Their way of keeping the ground wet is manual constructions of numerous small dams and banks that control the flow of water. Such human intervention prevents the ground from aridification. Why do they do so? When the volunteers came in more than 10 years ago for reconstructing the place, their rice paddies were abandoned, and the place was showing rapid drying. In contrast, Hiromachi’s wetlands are smaller and even today showing previous usage as rice paddies, i.e. not showing possible collapse as a swamp. Probably it allows the Kamakura Hiromachi Forest Citizen Association 鎌倉広町の森市民の会, the keeper of the forest, hands-off approach, such as their “complete” organic farming. The end result is a rich forest of broadleaved trees thriving amid the sea of suburban landscape of houses.

A scenery from a slope for Takegaya Valley

We proceeded on the boardwalk, and soon the road rapidly climbing up for the ridge way. If we continue straight from the point we reached the ridge, it leads us to Johka Centre Entrance 浄化センター入口that is the nearest gate of the forest for Shichirigahama Station 七里ガ浜駅. To the east, we head for Kamakurayama Iriguchi Entrance 鎌倉山入口. To the west, we can go down to Kamakura Highschool Station 鎌倉高校前駅 via Shichirigahama Entrance 七里ガ浜入口. It is also very interesting strolling the ridge way of Hiromachi Ryokuchi. We notice there is a variety of large broadleaved trees, evergreen and deciduous. Many have name plate placed by the volunteers, a show of love to the place. The road is sometimes narrow, but well-maintained and difficult to lose direction. Even though, the bushes of, say, sasa bamboos and Japanese laurel, often remained intact. Thanks to such forest maintenance, the place is famous for little wild birds needing bushes for their home and refuge. Japanese bush warbler, black-faced bunting, red-flanked bluetail, Siberian blue robin, blue and white flycatcher … Where small birds and mammals thrive, there are birds of prey at the peak of food chain. Eastern buzzard, Eurasian goshawk, owl, … It tells something of success for maintaining biodiversity through human intervention.

The ridge way to the direction of Shichirigahama Entrance

Shichirigahama Entrance.
The route dives straight into a suburbia of houses.

Passing the Shichirigahaa Entrance,
and going to the direction of Johka Centre Entrance,
we walk through bush of sasa bamboos.
The road is clear,
i.e. the volunteers control the invasion of sasa into the route.
Such an environment is loved by small birds as their home.

Mixture of Japanese laurel and large broadleaved trees.
Beautiful.

This is a large Cerasus jamasakura in winter.

During winter, we can easily notice
fat trunks of large trees in the ridge way of Hiromachi.

Going down to Johka Centre Entrance

The other day, I attended a zoom session done by Dr. Yuichi Yamaura of Forestry and Forest Products Research Institute (FFPRI) of Japan. He said retention forestry is currently the most understandable tool for maintaining biodiversity of a forest. Forestry is in the end the way to use forest for human business. The best method for cost minimization is clear-cut logging = deforestation = damage to biodiversity. In retention forestry, human intervention to a forest is done by strategically selecting trees to be retained. Those preserved trees then act as mother trees. The environment around them is not disturbed even if it might be a small area. They also spread their seeds, which makes the germination rate higher. Gene level contamination can be avoided for the environment, in contrast to the method of planting seedlings brought from some other places. Nature is a strong creature. If a sufficient condition is met, notwithstanding human money-making activities, a forest and biodiversity can recover rather sooner in such retention forestry. Humans can also achieve a successful forestry business by harvesting the trees. The issue in this approach for Japan is our highly diverse geography. Our forest can show different ecosystems even between minute valleys locating side-by-side sandwiching a ridge. A way of selecting mother trees on this side of valley may not be optimum for another side. Inevitably, the Japanese way of retention operation is the process of trials and errors …

I love this scenery in the ridge way of Hiromachi.
Bushes and large trees consist of many kinds of vegetation.
Yet, the road is well-maintained.

I think the enthusiastic “organic operation” Kamakura Hiromachi Forest Citizen Association is very successful so far for biodiverse forest. It would be an example of effective retention forestry for urban forest park. But it may not be suitable for Koajiro Forest that has larger wetland and directly facing sea. Or how about for Niiharu Citizen Forest? It’s difficult to have a conclusion … Still, please visit Hiromachi Ryokuchi Forest where lots of living creatures including enthusiastic organic volunteer farmers are calmly busy all year round. It’s just another side of the noisy tourism melee of Slam Dunk.

The management office which is what we’ve found at the entrance is

Kamakura Hiromachi Ryokuchi Management Office 鎌倉広町緑地管理事務所
1133 Tsu, Kamakura, 248-0032
〒 248-0032 鎌倉市津1133番地
Phone/FAX：0467-32-5112

The city office who oversees the place is

Parks and Green Spaces Section, Kamakura Cityscape Division 都市景観部みどり公園課　
18-10 Onarimachi, Kamakura, 248-8686
〒248-8686鎌倉市御成町18-10 本庁舎3階
Phone: 0467-61-3491 

park@city.kamakura.kanagawa.jp