Gaia: On recovering the power of soil in Tanzawa Mountains

Let’s return to bok-bok black soil. Whether its black Hoei Scoria, or red Kanto Loam, the strata made of volcanic projectiles are not good for flora to grow. There are certain kinds of species, so called “pioneer plants,” that can first take roots on such harsh conditions. They cannot grow fast and big, but they make the best of the terrain they are given, make seeds or spores, and die down. Their bodies decay to be organic matter and prepare better, if slightly, soil for their offspring to flourish more. After few generations of pioneers, the piled up dead-body become a part of Gaia where more delicate species are possible to take roots with organically richer condition … That’s the way volcanic soil turns into bok-bok. OK, you know, vegetables do not do it alone, don’t you? They have helps from bacteria, worm, insects … I mean something other than flora. The more such hands are available, the faster the road to Black Bok Soil is.

What we’ve observed the other day told us in Tanzawa 丹沢 it took more than 300 years for the forest to have 15cm petit bok-bok above 50cm Hoei Scoria. Er, I did not tell you last week. Where we dug was an afforested area. The forest is made of roughly 70 years old cedars. I don’t know if the place has been for the last 300 years for forestry where deforestation was regular ... Anyway, I was taught one thing about Japanese afforested area with conifers. In general, biodiversity of habitants in floors and below is generally lower in such forests than in forests of deciduous trees. The number and variety of bacteria et al is smaller for artificial forests of coniferous trees in Japan. According to Junichi Aoki (1995), biodiversity of Japanese forest floors can be ranked like

1. 🌞 Well-preserved natural forest or protected forest surrounding old temples and shrines
2. 🌟 Matured mixed forest that may have started as resources for daily use in pre-industrial rural villages
3. 🌲 Young mixed forest or coniferous afforested area
4. 🌷 Parks, residential gardens, school yards
5. 🚗 Roadside planting

* Diagnostics of Environment Using Soil Biota as Indicators. Jun’ichi Aoki, in “Impact Prediction on Natural Environment: result and manual for research methodology,” Environmental Affairs Department, Chiba Prefecture, 1995, 197-271. 土壌動物を用いた環境診断。青木淳一、「自然環境への影響予測-結果と調査法マニュアル」千葉県環境部環境調整課、1995、197-271。

Does coniferous afforested area really have not much habitant in their soil? The other day this June, we, Kanagawa Forest Instructors, actually counted how many kinds of bugs we can find with our naked eyes in a soil of Tanzawa’s afforested area. Yeah, it was not so exciting expedition.

It looks really rich the soil is, doesn’t it?

We dug and collected 4 sets of 50cm*50cm soil of forest floor for cedar trees of about 100 years old. As it was in Tanzawa, we dug only 10cm deep. It was its top soil, not reaching to Hoei Scoria. Before our research we also set for 48 hours traps of tin cans with baits, like sugar, chicken meat, and cheese. We carried both of these samples indoors and counted how many species we can find from them. We strained our eyes for about 1 hour on the soil spread over white plastic table cover, and found

<Group A>

Enchytraeidae (earthworm)

spiders

Acari (mites, ticks)

Springtails

Ants

Rove beetle

<Group B>

Oligochaeta (earthworm)

Thrips

Lithobiomorpha (stone cetipede)

Larva of moss

Weevil

Beetle

Larva of beetle

<Group C>

Diplopoda (Millipede)

Geophilomorpha

Symphyla

Gammaridea

4 traps, with sugar, chicken meat, cheese, and nothing

50cm*50cm

We dug it with this shovel, and carry it in a plastic bag.

Those in Group A can be easily found even in City Parks or road side flour beds along artillery motorways. Group B resides more environmentally rich area, and Group C is picky creatures live only in sufficiently biodiverse forests. We could not find many animals in Group C. No Opiliones (Harvestman), Scolopendridae, or shellfishes / slugs … That was somehow disappointing as we were deep in Tanzawa Mountains. “Yes, this June is really wet. Creatures in soil must have been suffocated with water, and moved to the other drier corners we don’t know.” “In any case, it is an afforested forest, though relatively old one.” “Indeed. Biodiversity is supposed to be poorer than for natural forest.” Er, yes. But I just thought the soils in Tanzawa Mountains are in any case handicapped by thick Hoei Scoria thanks to Mt. Fuji nearby. That would be the best they can do at this moment of geological time … Can we tell them “well done”?

The soil was spread over this plastic cover for us to search.
 Before that, we checked what’s inside the trap.

We’ve found a cricket and a beetle!

The place we dug the soil.

Lessons learned from this adventure, I presume, is, we really have to treat gently the tierra of forests in Kanagawa Prefecture. Thanks to “Rediscovery” of charms in natural forests, and our proximity to downtown Tokyo, these days many many people hike our mountains. Not all of them know the fragility of the nature in Tanzawa. One day, I’ve met a group of senior citizen hikers, about 10 granddads near the peak of Mt. Oyama 大山 (ASL 1252m). In that area, rangers and forest instructors are busy monitoring the environment with lots of deer fences and observation equipment. In the 1980s, we Japanese first recognized that part of forest affected by acid rain from Megalopolis, and dying out of gigantic beeches whose barks were eaten by deer and sawfly (Fagineura crenativora). Keeping healthy soil is vital for the place to recover the damage done. The Prefecture builds and maintains lots of deer fences to fend off deer. The office also prepares good trekking roads expecting humans do not deviate from nice road, aka discouraging humans from invasion. But … At that time, those supposed to be sensible senior adults were criss-crossing the fragile slope of the mountain, off the hiking road, laughing excitedly. “Hey, this way is far faster!” OK, they may have recalled the adventure they had 60 or more years ago when they were kids. But, now they were far heavier adults, probably having grandkids. Their stamping impact on the soil was definitely greater than before. Trudging the forest floor by humans depletes the top soil the most heavily, completely different from what bears do. It destroys the ecosystem underground, and weakens the vegetation depending on the nutrition from the ground. Once the flora becomes unhealthy, so does the animal world sitting above the food chain. Impossible outbreak of insects, like sayfly, would recur. By the way Tanzawa needs at least 300 years to recover 15cm of humus-like soil from Hoei Scoria. Did those grandpas know what they were doing? I doubt that.

This is human power.
 Just walking, we can gouge mother earth this much.
 Could you see the difference in height of the surface
 between the road and the roadside?
 Also, we find lots of big roots running across the road.
 They were once underground,
 but now all the soil over them was gone.
 Pathetic, actually.

So I tell you. Please know our forests are fragile. Don’t deviate from hiking road unless there is absolute necessity. Happy summer hiking season. Oh, I of course told them “Please do not deviate from hiking route. This is a protected area, blah-blah-blah.” They looked a sort of dumbfounded, being told to behave well by a stranger WOMAN in deep-mountain. They were typical of Japanese male, taking it for granted silent females. Heck. Come to think of it, Gaia is a goddess.

If you find an environmental issues in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター

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/