The Battle of the fittest: Water reservoirs and rich vegetation of Oiso Hill 大磯鷹取山

We use a commuter bus service of Kanacyu Bus Hira-31 or -32 (平‐31, 平‐32, time table here) from #2 bus stop in the north exit of JR Hiratsuka Station 平塚駅, and reach to Ikusawa Bus Stop 生沢. In front of us is Higashino-ike Pond東の池. This pond is recorded in a historical document, Sinpen Sagami-no Kuni Fudoki-koh, published in 1841 (新編相模国風土記稿 Newedition for Records of Sagami Region). According to this report, it was constructed in the early 17^th century as one of the two man-made reservoirs to serve agriculture of Ikusawa Village. This is a substantial pond of 4000 m² with a tiny island in the middle connected by a bridge. The island has a petit Itsukushima Shrine, an apparition of grandeur Itsukushima Shrine 厳島神社 in Hiroshima 広島. The place worships the youngest of 3 goddess of Itsukushima Shrine, Tagitsuhime-no-mikoto 多岐都比米克命. The small precinct of the shrine has very old trees, including a spineless holly osmanthus. Osmanthus heterophyllus loses its spines from leaves as tree matures. Oiso Itsukushima Shrine with the spineless holly should be very old. The water of the reservoir has been managed by a cooperative of the local farmers. Until 3 or so years ago, the place was also famous for its gorgeous lotus flowers covering the entire pond. Then in 2015, the lotus suddenly reduced its presence, and from 2016 we could not find any. Oiso Town Council and Town Hall 大磯町議会・役場 consider the situation a possible environmental collapse. At the moment, they are planning to drain the pond to study the bottom. Controlling water is always difficult …

Higashino-Ike Pond.
Certainly no lotus could be found in this photo.

Itsukushima Shrine in Higashino-Ike Pond

This is a very large holly.

We cross the bus road to the northeast and go to the direction of the Hill in front of us. After a bit of walk in an alley among local houses via a small tunnel under Odawara-Atsugi Toll Road, the road plunges into a forest of evergreen broad-leaved trees. The thickness of the forest is amazing, especially when we consider human difficulty getting hold of water here … The protagonists of the forest of Oiso Hill are Microtropis japonica and Machilus thunbergii. In the rainy climate of Kanagawa Prefecture, grounds near sea are relatively warmer than the inland area such as Tanzawa or Hakone. Microtropis japonica and Machilus thunbergii are best suited for such condition. It is considered that once they dominated the forests of coastal area in Kanagawa. After humans settled here and started to exploit the bounty from the forest, such as for firewood or construction materials, Microtropis japonica and Machilus thunbergii were replaced by Quercus acutissima / serrata and coniferous trees. They were also removed for residential development that occurred in large cities including Yokohama. Lots of these trees in Oiso Hill mean the place was spared from such man-made changes. Housing development aside, it’s a kind of evidence the area had difficulty to expand agriculture. The geological feature of Oiso Hill makes it hard for an underground water system for cultivation ...

Please find this signpost and
follow the direction to Mt. Takatori 鷹取山.

The tunnel under Odawara-Atsugi Road

We first enter this magical bamboo forest.
Though, all the forest instructors said
“Well, this place needs definitely more care!”

Actually, we have entered
“Kanto Friendship Road.”
More to this below.

The forest has firewood trees and coniferous trees of course.
But they are not ruling the place.

Litsea coreana.
We can enjoy an enchanted forest if it rains. 😇Er, please do it if you know the place damned well.
Otherwise, play it safe.

Having said that, Oiso Hill has a long history of human activity, which is another reason why paradoxically it keeps Microtropis japonica and Machilus thunbergii relatively well. At the top of the mountain, there is Takatori Shrine 鷹取神社. This is an old one. A record in Azumakagami 吾妻鏡 dated on 27 April 1191 said, the priest of the Shrine petitioned the powers-that-be of the time, probably Minamoto-no Yoritomo 源頼朝, to stop a newly appointed local official cutting mulberry trees in its precinct. A legend says the place was known as Sengen Shrine 浅間神社 for millennia among locals. In less than 5 minutes’ walk from the Shrine, there is the peak of Oiso Hill, called Mt. Takatori 鷹取山 (ASL 230 m). One day of the early 17^th century, when Tokugawa Ieyasu 徳川家康 enjoyed falconry in Hiratsuka 平塚, his falcon escaped from the hands of falconers, but was recaptured at the top of Mt. Takatori. Since then, the place has the name “Takatori-yama” or Falcon-catching Mountain. The shrine had received financial backing from Tokugawa Shogunate Government 徳川幕府 for some 250 years, and attracted lots of worshipers. At the time of Meiji Restoration 明治維新 in the middle of the 19^th century, the shrine was renamed as Takatori Shrine and defined as the village shrine of the area. Having Shintoism shrine at the top of a hill near a village was a prototype of traditional Japanese rural community. Those villagers protected the vegetation around the institution as a part of their god. Takatori Shrine keeps the historical design well, and so the forest around the shrine was spared from developmental activity for centuries. Currently, roughly 1 ha of the forest surrounding the shrine is designated as one of the natural treasures (nature sanctuary) of Kanagawa Prefecture.

Wild Liriope muscari with its blue berries.
Their seeds are natural super balls
bouncing very well on hard surface. 😁

Takatori Shrine.
If you go there,
please take your photo with this structure to collect badges.
More to this below.

Go straight from the Shrine,
and we meet a flat space with sparse trees,
which is the top of Mt. Takatori.
My senior instructors guessed
the place could be for some structure ages ago.
Historical record says Takatori Shrine had priests
in residence until about 150 years ago.
Maybe this place was for their home.

Let’s keep going straight down from the Shrine along a blacktop road. Eventually we meet a signpost showing the directions to Mt. Takatori 鷹取山, to Myoen-ji Temple 妙円寺, and to Shogan-ji Temple 松岩寺. If you take a road to Myoen-ji Temple, the route we take so far becomes Mt. Takatori – Village Route 鷹取山・里の道 which is designated as one of the Kanto Friendship Roads, aka Nature Trekking Roads in Metropolitan Tokyo Area 関東ふれあいの道 (首都圏自然歩道). It’s a fun program organized by the Ministry of Environment of Japan, started in full in 2010. A circling trekking road runs through all the 7 prefectures of Kanto Region 関東地方. The route is demarcated in 160 sections of about 10K distance each that can be completed in a one-day hike. You visit them one-by-one and collect photo evidences of yours at an assigned landmark. When you conquered all the routes in one prefecture, e.g. 17 itineraries in Kanagawa Prefecture 神奈川県コースマップ (details here), you send the photos with your small comments of each road to the prefectural office in charge of the program, e.g. for Kanagawa, Natural Environment Conservation Center 神奈川県自然環境保全センター. They then send you back a certificate of your accomplishment together with a pin-badge. At the time you send your final dossier to the 7^th prefecture of Kanto, please enclose photo copies of the certificates from the previous 6 prefectures. You will receive the 7^th certificate + badge, and the Grand Certificate and a special badge honoring your achievement. As of 2015, there are 30 awardees who acquired the grand pin-badge. For Mt. Takatori – Village Route, your photo point is at Takatori Shrine. You can start your weekend project with the program now!

From the Shrine along a black top road from Hiratsuka City.
To the left from the Shrine,
we peek in the scenery of Lake Wood Golf Club.

You’ll meet this sign post saying
“This route is Kanto Friendship Road.”

The signpost at the crossing of the 3 directions to
Mt. Takatori, to Myoen-ji Temple, and to Shogan-ji Temple

But today, we take the route to Shogan-ji Temple to see an evidence for water problem of Oiso Hill. Turning right at the junction of the 3 roads, the route climbs slightly and then we comes to another hill top, this time with a farmland spreading over it. This is called Yurugi-no-oka Hill ゆるぎの丘 of Kisawa community 吉沢 in Hiratsuka City 平塚市. Hiratsuka City is promoting the hill and the vicinity as agricultural and tourism area. The view from Yurugi-no-oka includes entire Mt. Oyama 大山, Sagami Bay 相模湾 and, weather permitting, Mt. To 塔ノ岳, Mt. Nabewari 鍋割山 + Mt. Fuji 富士山. This is a wonderful spot for your lunch, sans any water facility including toilet. That’s saying something ... From there, the road lazily descending to the foot of the hill where we can meet Yatsurugi Shrine 八劔神社 or “Eight and Sword Shrine” in less than 1km from Yurugi-no-oka Hill. It worships Yamatotakeru-no-Mikoto 日本武尊, Susano’o-no-mikoto 建速須佐之男命, and Oohirunomuchi-no-mikoto 大日霊貴命 (akaAmaterasu 天照大神). All of them are the main protagonists of Japanese mythology, and Susano’o is famous for his adventure with 8-headed dragon which is the demon representing flood 八岐大蛇. Susano’o is also an owner of a mythical sword 草薙剣 that is now (notionally) the property of the Emperor 三種神器. For this modest shrine in a rural community, the residents of Yatsurugi Shrine are rather grande. It is said that the shrine is the protector of Kisawa community for at least 1000 years. And, we meet here the connotation with “flood.” 😉 

We go up from the junction of the 3 roads.

The road soon becomes leisurely.

Yurugino-oka Hill. We can see Mt. Oyama over there.
Unfortunately, when we reached there,
the clouds were still blocking our view
to the ridges of Tanzawa and Mt. Fuji.

Yet, Yurugino-oka Hill has nice picnic benches.

The road rambling down to the foot of Oiso Hill.
We think we have spotted an Accipiter gentilis.

Yatsurugi Shrine

At Yatsurugi Shrine, there is another crossing for the 3 destinations shown by a signpost. Please turn right here to the direction of Shogan-ji Temple 松岩寺. The rural scenery continues for less than 10 minutes, and we reach to another reservoir in approximately 300m from Yatsurugi Shrine. It is Naka-Kisawa Pond 中吉沢の池 created in 1935 in order to secure water for agriculture of the community. It collects water from roughly 400m long stream, called Miyashita River 宮下川 originating from near Yurugi-no-oka Hill. The entire area is on the conglomerate created by tectonic movements and volcanic eruption that made rain water hard to gather subterranean. Before the construction of the Pond, a storm quickly made watercourses torrent and flooded the area. In draught, farmers could only lament their bad luck. The pond has 49m*30m*10m dimension, i.e. substantial, to tackle these problems. Along the reservoir and the stream, there runs a trekking road. Although the place is almost next to the residential area of Hiratsuka City, the way alongside Miyashita River can cause us a false sense of being in a deep mountain. (“Where are houses, or ag lands?”) Crossing several small wooden bridges over Miyashita River, we meet Shimofuri Waterfall 霜降の滝. Unless it rains really hard, Miyashita River is pequeño, but the Waterfall is something to see. The geological structure of the riverbed becomes apparent around the waterfall. This is the spot where we can directly observe the conglomerate spreading below the shallow top soil of Oiso Hill. I was a kind of convinced why it’s so difficult for underground water in Oiso. Rain cannot go underneath this rock.

The junction at Yatsurugi Shrine.
Please turn right here.

On our course, there are signposts for the Pond.

Naka-Kisawa Pond

A trekking road goes along the pond.

Miyashita “River.”
This petit flow can cause headaches.

One of the “bridges” over Miyashita River

Shimofuri Waterfall is over there.

Watching the waterfall from the above,
we can recognize a smooth surface of a gigantic rock
that is a part of Takatori-yama Conglomerate 鷹取山礫岩層.

The end of trekking road along the stream is a narrow, but paved path that leads us to rolling farmlands, and then to the cemetery of Shogan-ji Temple 松岩寺. We pass through the precinct of the temple, and reach to the bus route of Kanacyu commuter services to JR Hiratsuka Station 平塚駅 and JR Ninomiya Station 二宮駅.  To return to Hiratsuka Station, we can take a bus from Shogan-ji Temple Bus Stop 松岩寺バス停 (time tables, here), which is an about 20 minutes ride. I found it ironic because Hiratsuka City along Sagami River was once famous for their rice paddies so difficult  to dry. According to “An Oral Record for Traditional Meals in Kanagawa 聞き書　神奈川の食事,” until the 1950s the farmers in Hiratsuka could not drain their paddies so that in late autumn they waded in freezing semi-pond of rice paddies for harvesting. That’s the story only for the delta of Sagami River that is in less than 1km away from Kisawa community. For humans, it’s so tricky to deal with water … Whatever, those formidable trees in Oiso Hill are impressive. In spite of the conglomerate below, they just simply spread their root and thirstily drink from rain. The fittest, indeed. Perhaps, that would be the reason why we have to rely on the forests to capture water.

Actually this paved road is for farmers
living in the foot of the hill to go to …

... their farmland beyond the waterfall.
We can see Sagami Bay over there.

Shogan-ji Temple

We’ve descended from this road
running in the precinct of the Temple.

Shogan-ji Bus Stop

The contact address for Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター is

657 Nanasawa, Atsugi City, 243-0121 〒243－0121　厚木市七沢657
Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/

Oiso Town Hall 大磯町役場

183 Higashi-koiso, Oiso-cho, Naka-gun, Kanagawa, 255-8555

〒255-8555　神奈川県中郡大磯町東小磯183

Phone ： 0463-61-4100　FAX ： 0463-61-1991

https://www.town.oiso.kanagawa.jp/ikkrwebBrowse/inquiryPC/Sec.do;jsessionid=AC09D1499780CCBD42365B009AB24F7A?mode=pc&inquiryId=53&ref=www.town.oiso.kanagawa.jp/isotabi/

Hiratsuka City Hall 平塚市役所

9-1 Sengen-cho Hiratsuka City, Kanagawa, 254-8686 〒254-8686 神奈川県平塚市浅間町9番1号

Phone：0463-23-1111 Fax：0463-23-9467

https://hiratsuka.custhelp.com/app/ask/p/64/

You can’t always get what you want: water and Oiso Hill 大磯丘陵

When we walk water source forests in Tanzawa 丹沢, it looks like Kanagawa Prefecture cannot have water shortage. Mountain torrents are here and there. Lots of rain washes the soil down when the afforested area has not had enough care … water is abundant. Hmmmmm … recently I noticed lots of rain does not necessarily guarantee water supply. One example we can find in our prefecture is communities in Oiso Hill 大磯丘陵. Let’s do a little hike there this week and next, to find historical ponds our ancestors dug to tackle water problem there.

It happened to be down-pouring in the morning
when we visited Oiso Hill the other day …
Believe me or not,
it’s a gigantic cinnamon tree
grew in the garden of local resident.

Oiso Town 大磯町 is more familiar with its seaside features. Oiso Beach 大磯海岸 is the first modern swimming beach in Japan, opened in 1883. In the 19^th and early 20^th centuries, the beachside was populated by villas of rich and powerful for Japanese national politics. Of this connection, the place was a playground for Yukio Mishima 三島由紀夫, a grandson of the third colonial minister for Sakhalin.  These days, Haruki Murakami 村上春樹 lives near Oiso Beach. All sound pretty much gorgeous, don’t they? When we look north of the JR Oiso Station 大磯駅, the hill is almost over us. Within 10 minutes’ walk from the station, we are on the seashore. A flat zone between Oiso Hill and the beach is quite limited. That’s the reason why the celebrities of the last centuries loved the scenery of the town, for sure. But geologically speaking, the place has a challenging feature especially for water. Nowadays, the town is receiving water from Sagami River so that the problem is solved. Before having modern water supply system, for ordinary folks who tilled the soil for living in Oiso, securing water was a critical issue. The area has lots of rain. So, the problem for commoners in Oiso was how to “safeguard” it.

Oiso Beach in winter.
Once it was a surfing place for Haruki Murakami.

A sunrise in Oiso Fishing Harbor

JR Tokaido Line 東海道本線 runs
along almost the edge of Oiso Hill,
where the south of the railroad is farmlands.

When we observe the southwest direction from Bodai Pass 菩提峠, about an hour walk from Yabitsu Pass ヤビツ峠, we notice there is a kind of land mass between a flat alluvial fan immediately below us, i.e. Hadano City 秦野市, and another urban expansion beyond, i.e. Odawara City 小田原市. The hilly area between 2 cities is Oiso Hill.  The hill itself is divided by an active fault line, Ikusawa Active Fault Line 生沢活断層, where currently Tokaido Shinkansen Bullet Train 東海道新幹線 is running. We can infer the birth of Oiso Hill from this scenery. Kanagawa Prefecture situates itself on the crush line between Eurasian and Philippine plates. About 5 million years ago, the tectonic squeeze pushes up the land mass on Eurasian Plates, and raised the sediments on the seafloor along the friction line of two plates. It created the base of Tanzawa Mountains and Oiso Hill 丹沢山地の衝突現象. This tectonic movement continues even now that is the Ikusawa Fault Line. The sediments from the sea continued to be raised till around 120 thousand years ago, which is now directly observable in the southeast side of the fault line called Shonan Daira 湘南平 of Oiso Hill where Komayama Park 高麗山公園 locates. Around 500 thousand years ago, Mt. Hakone and Mt. Fuji erupted and started to spew out tephra and lapilli. They piled up over the raised ground by plate tectonics, especially on the west side of the Ikusawa Fault Line. The push-up and volcanic tephra eventually created the peak of Oiso Hill, aka Mt. Takatori 鷹取山 at ASL 222m. Thus, the current soil of Oiso Hill is made of the raised seabed and volcanic projectiles whose date is relatively recent. That’s the reason why humans came here about 10 thousand years ago found the hold of local water tricky.

Observing Oiso Hill from near Bodai Pass.
The flat land below us is Hadano City,
then there is Oiso Hill separating
Hadano from Odawara over there.
Could you see
the Oiso Hill is divided by a small fissure on the left?
It’s the Ikusawa Active Fault Line.
The left of the fault line is Shonan Daira
which is very popular for family picnic.
The higher mountains at the background
of this photo is Hakone 箱根.

Observing Shonan Daira
from the estuary of Hanamizu River 花水川.
Hanamizu River originates from
Mt. To 塔ノ岳 and Mt. Oyama 大山 of Tanzawa,
and yet Oiso Town, the west of Hanamizu River,
had water problem thanks to Oiso Hill.

The point where Hanamizu River meets with
Sagami Bay 相模湾 is a peaceful place …

When farmers dug the ground for wells in Oiso Hill, they could easily be blocked by large lapilli. Although the highest altitude of the Hill is not much, the way its created is exactly the same as steep Tanzawa mountains, i.e. plate tectonics and volcanos. The slope of smallish Oiso Hill is sharp, and it’s very near to the sea. Unless the ground is extremely absorptive, rain drops reached to the ground can escape rapidly to the sea. Conglomerate of Oiso Hill is exactly the opposite of spongy soil. Frequent rain along the warm Oiso coast line can nurture a good forest for celebrities to admire, but it does not necessarily guarantee stable water supply.

To see how it actually is in Oiso Hill, we visit the peak of Mt. Takatori 鷹取山. There are several trekking routes one of which is introduced by the Oiso Town in the link above. Though, this time we start from Higashino-ike Pond 東の池, and descend to Hiratsuka City 平塚市 where we can actually observe a gigantic lapilli that prevents rain from becoming an underground reservoir. To go to Higashino-ike directly, we take a commuter bus service of Kancyu Bus Hira-31 or -32 (平‐31, 平‐32, time table here) from #2 bus stop in the north exit of JR Hiratsuka Station 平塚駅. After about 30 minutes ride, we get off the bus at Ikusawa Bus Stop 生沢, next to Higashino-ike Pond. To the south, we are greeted by frequent visits of Shinkansen Bullet Train, and Hiratsuka TV Relay Station Tower of Shonan Daira. Now, let’s continue next week our adventure to the forest that has difficulty to be a water source any way.😉

#2 bus stop
in the northern exit
of Hiratsuka Station

Ikusawa Bus Stop

A Bullet Train and the TV tower to the south of the bus stop

It was raining anyway.

The Oiso Hill covers Oiso Town, Hiratsuka City, and Ninomiya Town 二宮町. The Hill in Ninomiya Town is occupied mainly by private golf courses so that if you find problems during your hike, you’d better make a contact with either Oiso Town or Hiratsuka City. Their contact addresses are

Oiso Town Hall 大磯町役場

183 Higashi-koiso, Oiso-cho, Naka-gun, Kanagawa, 255-8555

〒255-8555　神奈川県中郡大磯町東小磯183

Phone ： 0463-61-4100　FAX ： 0463-61-1991

https://www.town.oiso.kanagawa.jp/ikkrwebBrowse/inquiryPC/Sec.do;jsessionid=AC09D1499780CCBD42365B009AB24F7A?mode=pc&inquiryId=53&ref=www.town.oiso.kanagawa.jp/isotabi/

Hiratsuka City Hall 平塚市役所

9-1 Sengen-cho Hiratsuka City, Kanagawa, 254-8686

〒254-8686 神奈川県平塚市浅間町9番1号

Phone：0463-23-1111 Fax：0463-23-9467

https://hiratsuka.custhelp.com/app/ask/p/64/

Baby sitting: pruning the trees in a water source forest of Kanagawa

In order to take care of afforested forests for water source, there is a cycle of jobs. Preparing the ground, planting seedlings, mowing, pruning, thinning … if the forest is for commercial logging, the final task is deforestation, then, the new cycle of ground preparation begins again. This week, I show you a bit of pruning for Japanese cypresses we’ve done recently. After our activity, I’ve felt a kind of “accomplishment” similar to a sense we have with a warm shower after a jog. Observing our job done gave me really a good satisfaction. It’s not smugness, believe me. Let me start telling you my pruning adventure to nurture the afforested forest for water source in the climate of Kanagawa Prefecture.

At the first stage before planting, the ground must be prepared. There may be a landslide, or deforestation by commercial logging. The space is cleared and the soil is to be plowed for baby trees to settle in. Additionally in Kanagawa prefecture it is a “MUST” these days to construct 2m high meshed barriers enclosing the vacant area in order to prevent the invasion of deer which love to devour baby trees for lunch.  Then, we plant seedlings. Recently it is more common in Kanagawa’s public land to plant broad leaved trees after harvesting of coniferous trees, hoping to create quasi-natural forest of our climate. Since mountains of Kanagawa are steep, the baby trees are often planted at the corner of rectangle whose sides are shorter in ridge and valley sides than for the sides of slopes. Reason? The canopy of trees planted nearer to the ridge grows wider to the direction of valley, which would reduce sunshine for the leaves of trees placed to the next lower place. In order to prevent the effect, we often keep the distance between the seedlings to ridge-valley direction. If they are the babies of coniferous trees, the standard in Kanagawa is 3000 of them per 1ha. For the areas of more intensive commercial forestry in southern Japan, it’s more common to plant 6000-8000 seedlings in 1ha. 3000 “would be optimal here,” I’ve heard from the professionals. We mark the corners of rectangles, and dig a hole there deep enough for the roots of a seedling can be stored with about 0.5 inches of soil covering their basis. We next “do a circle” around the baby tree to tread down the ground to support the seedling standing. I love this process, as it’s like a dancing for babies to grow well. 😊 The planted seedlings are indicated by a bamboo cane tied to their fragile trunk for propping up. These sticks become a mark when we mow the field to avoid chopping them off accidentally.

The seedlings are planted this way in the mountains of Kanagawa.

The seedlings of broad leaved trees
we’ve planted the other day.
The meshed fence behind them is enclosing
the afforestation area, protecting inside from deer lunch.

First
we dig a hole deep enough to cover the roots of a seedling.
The excavated soil is temporary stored
in the upper side of the hole,
and gently moved back to the hole with the seedling.

Stomp-dancing around the seedling.
We gently grab the baby tree and pull it up slightly
while we do a circle around it.

Loosely tie the seedling to a bamboo cane
to support it standing, and as a mark.

Ideally, mowing for an afforested area is done at least once a year during summer for the first 5 years of baby trees. During this period, the seedlings are still small and the weeds dominate the place in Kanagawa’s summer, which could prevent the toddler trees to receive enough sunshine for photosynthesis. For coniferous seedlings, once they become tall enough to escape from the overpowering grass, it is the time of the first pruning. To create straight and long logs for human consumption out of Japanese cedars and cypresses, it is important for a tree to have enough time, 2-3 years, covering sections by epidermis after pruning especially near the root. (Nearer the root, fatter the trunk, so that pretty lower bottom of a tree can provide more substantial logs. Got it?) Moreover, the dead boughs could create a huge hole on a tree’s trunk when we neglect the care for them. The crucks created by dried out branches attract pests and viruses, such as Cerambycidae, that will kill the tree eventually. It is important pruning cedars and cypresses regularly for at least their first 20 years, starting from their 5^th-8^th year.

The no-pollen cedars of their 5^th year summer.
The ground is completely covered with grass and shrubs
but now they are tall enough to receive sunshine by themselves.
The mowing of the place is completed this year,
and probably next year or so we will do the first pruning.
In Japanese forestry lingo,
the first pruning is called Suso-harai 裾払い,
“rear foot sweep” that is from sumo technique.

The traditional theory of afforestation in Japan is, cypresses are for drier place so that it is standard during your hike finding them near ridge after a cedar forest. (People do not follow standard always, of course. 😉) The point to differentiate cedars and cypresses is ground litter. Japanese cedars shed the old branches by themselves. When you find branches of coniferous trees on the ground in Kanagawa’s mountain, the trees around you are cedars. Often they are along the mountain stream, or near the valley. When humans harvest the tree in desired size, their natural discarding could be too late for sections to be wrapped completely with the outer skin. Or, the left-out broken boughs could be an entry way for diseases. Thus, pruning. On the other hand, Japanese cypresses do not drop their bough even when the branches are desiccated.  Cypresses renew their tiny 1-2mm leaves during fall to winter, leaving the boughs sticking out of the trunk. The lifespan of leaves of Japanese cypresses is about 6 years. After summer their 6^th year leaves fall off from the branches and cover the ground underneath.

The stems separated from
the fallen branches  of Japanese cedars

Trekking road in Mt. Oyama 大山
running in the Japanese cypress forest.
Could you see the difference with the above photo?

With these characteristics in mind, pruning is important especially for the health of coniferous forests. A forest of cedars et al without proper pruning is a dark place. Being it cedars or cypresses, the withered boughs and branches block the sunshine reaching to the forest floor. It becomes difficult for undergrowth to take hold when only the tree top receives enough power of sun. In such forests, the trees grow lanky with insufficient development of roots. The slope becomes vulnerable for soil erosion. For example, decay of fallen cypress leaves is VERY slow. In a dark cypress forest, it’s like walking on leaf-confetti without much hurdle of ground-growths. Furthermore, as you may expect, the cypress leaves are too small to stop water flow when it pours over a steep slope. There is this academic paper 林試研報 about substantial soil erosion in cypress forests. It fares better for forests of cedars without pruning whose ground is covered by shriveled branches scattered all over. But their effect is not much for soil protection. In contrast, proper pruning create space within a forest for sun light reaching to the ground. With rain and sun, the dormant seeds of grass, shrubs, and trees will sprout. They eventually protect the soil and forest to be washed away by storms. The trees grow with deep roots and store water underneath. Pruning is vital for maintaining water source forests in Kanagawa.

The cedar forest in the northeast slope of Mt. Oyama.
I think Atsugi City does a good job
for keeping the coniferous forest by pruning and thinning.
The sun light comes in here,
but still the undergrowth is limited at best.
In this photo, we can identify lots of retaining walls
made of thinned logs to prevent soil erosion.
Creating hierarchical structure in a forest is really difficult …

The height of the pruning depends on the objective of the usage of trees. When we plan to harvest a coniferous log for a pillar of standard Japanese house, we prune off branches and boughs sticking out the lower 6-7m part of a tree until its 20-25^th year. For a material suitable for repairs of gigantic temples in Nara or Kyoto, people nurture a cypress for decades or centuries by pruning the lower boughs nearer to withered branches deprived of enough sunshine by the leafs spreading above them. Kanagawa prefectural government does not recommend volunteers pruning with ladders at the height higher than 2m. So, we tackle with the branches within our reach. For creating a beautiful trunk of a tree, best pruning seasons are October-December and March. During dead-winter, trees dramatically reduce their water intake from the ground and their body becomes hard enough to make the operation difficult. When trees drink a lot during late spring to early summer, their vascular bundle is expanded with lots of liquids running inside. When a part of the system of bundle is terminated abruptly in the middle, which is pruning, the vascular organ is exposed suddenly to the outer world with its mouth wide open. For a tree epidermis, it’s difficult to cover the large wound completely. The tree will have a hole under the bark at best. Otherwise, the trunk keeps a cavity, not good for health of a tree or housing material.

This is one way of
reaching to the higher branches.

One weekend of this November, we entered a public forest located in the steep somma of volcanic Mt. Hakone 箱根火山. The place is a water source for Sakawa River 酒匂川 where many parts were afforested by coniferous trees decades ago. We forest instructor trainees have come this area several times as a part of the curriculum. Due to very rainy autumn this year, there were mini-landslides here and there in the area. I noticed several mini-ponds off the mountain stream where a couple of large cedar trees stood in a pool. The waterway had come that far during last storms … Our instructors told us due to 2 consecutive typhoons in October, there occurred numerous mini-land failures, although they did not triggered disaster downstream. Now the prefecture is busy in restoration works for the stability of the collapsed hills. The forest we pruned away this time was populated by 14 years’ old Japanese cypresses. They are still young with 20cm or so diameter. I noticed they preserved their withered branches at very lower part of their trunk. … They could not have their 5 years’ old pruning … the branches and boughs congested the forest. Inevitably, the entire place was very dark despite of a fine fall Sunday. Not much undergrowth was found except sasa bamboos whose roots expand horizontally over the shallow depth of the soil. I a kind of understood the reason of mini-slides in the area.

Could you figure out a mini-land slide over there?

Lots of dead branches are sticking out
from the lower trunk of young cypresses.
Although it was a windy day,
not much air stream penetrated into
the maze of tree boughs.

Our task was to prune off the branches, and mow sasa bamboos to make space for more deep rooted vegetation growing with sunshine. The forest expands over very steep slope which makes pruning the branches sticking to the direction of ridge way easy, but I had hard times to deal with those spreading to the valley side. I, a short Japanese woman, cannot reach them from the front … Properly done, pruned-off part will leave a round cut end surrounded by branch seat which is a part of the trunk. Cutting into the branch seat damages epidermis that would cover the cut end otherwise. I could manage preserving branch seat, but my cut end looked oblong when I had to reach to a valley-side branch from the ridge way direction. Moreover, the young cypresses were surrounded 3-4m long sasa bamboos poking from their roots. Although the bamboos were leggy at about 1cm in diameter (as this place does not have enough sunlight), they block the access to a tree. Worse, they could make the slope more slippery, and our movement around a cypress became more dangerous. “Woops. You have not sawed the bough straight.” “If you find the branch large, first provisionally cut it about 10cm from the branch seat, and then prune it away completely at the mouth of branch seat.” My seniors advised me. Hm. I found the 2-step approach worked well. Doing mowing and pruning at once for each tree on a steep slippery slope required patience and concentration. That was a very meditative task ...

This poor cypress was surrounded by
sasa bamboos and kept its lower twigs
poking out all over.
It would be a candidate for a thinning …
but today, we come here for pruning!

This is a good example of proper pruning for a coniferous tree
(; the photo was taken in cedar forest in another occasion).
Could you see the cut end is round?

I managed to do proper pruning this side
… and the other side is remaining …

Within 3 hours, roughly 80 volunteers of us pruned off the 1.6ha of young cypress forest. From the below, we could see the ground now receiving more sunshine, and the chilly autumn air started to flow among the trees. I hope the forest does not have torrential rain any more this year, but only drizzling or snow. If so, I imagined, early next spring when snow starts to melt slowly, spring ephemeral with enough sun-shine could show their head out of the ground, and start doing their job of stabilizing the soil of cypress forest. By and by, the water stored beneath the cypresses will join Sakawa River and come to Yokohama safely … I felt an accomplishment of our job. It might be self-satisfaction, but there is a scientific logic connecting pruning in the forest of deep-mountain and safe drinking water in a megalopolis. Calling our feeling “smug” could be very cynical and smug, I guess.

We mowed only sasa bamboos and left shrubs,
hoping for multilayered plant structure to materialize in the forest …

The sun light is coming in now!

Kanagawa Water Source Authority

1194 Yasashi-cho, Asahi-ku, Yokohama, 241-8525

Phone: 045-363-1111