Examples of Our Activities

When working with nature, things don't always go as planned. That's why ongoing surveys after forest maintenance are crucial. Sometimes, results exceed expectations, while other times, efforts end in complete failure. Here are some examples of challenges and discoveries encountered during our activities.

These Deer Weren't Here Last Year

In our Natural Water Sanctuary Okudaisen, 2 to 3 meters of snow accumulates during winter. Because of this, deer had never been seen in the area until recently. However, signs of deer feeding on grass and shrubs started to appear. In response, cameras were immediately set up, revealing a significant presence of deer.

The original maintenance plan for our Natural Water Sanctuary Okudaisen was designed for a forest without deer. Until recently, this sanctuary stood out as an exceptional example where biodiversity thrived and maintenance results were highly effective.

Unfortunately, the unexpected arrival of deer meant the plan had to be completely revised. The first step was to fence off key areas. However, standard metal fences would be damaged as melting snowpacks move during the spring thaw. To address this, we are taking an emergency measure of installing a resin net immediately after the snow begins to melt, and then laying the net flat on the ground when the snow starts to accumulate.

Deer in Okudaisen

Installed resin net

A Mountain Made of Pumice?

When the agreement was signed to create our Natural Water Sanctuary Shizuoka Oyama, the most surprising aspect of the forest management challenge was the fragility of the mountainside. The majority of the existing logging roads had been severely eroded by heavy rains, leaving deep trenches throughout.

In fact, this mountain is composed of alternating layers of volcanic ash from past eruptions of Mount Fuji and small pumice stones called scoria. When roads or other clear-cuts expose the ground, the pumice layer is quickly eroded by water.

As a result, we decided to turn unnecessary logging roads back into forest. Unfortunately, these areas are also frequented by many deer. So, on the flat roadbeds we planted mitsumata (Oriental paperbush) and susuki (Japanese silver grass), which are less palatable to deer. Although susuki is generally disliked by deer, for some reason they like to pull out the young plants. So, we are covering them with agricultural bird netting until they are well-established. The broadleaf trees planted on one side are being protected as individual trees.

Mitsumata (Oriental paperbush)

Susuki (Japanese silver grass) protected by bird netting

New Discoveries During Forest Management

As we continue to repeat our process of R-PDCA (research, plan, do, check, and act), we sometimes make unexpected discoveries. Here are some of the surprising discoveries we have made about wildlife during our forest management activities.

Deer Feeding Almost Exclusively on Fallen Leaves During Winter!

As part of our Natural Water Sanctuary Project Chichibu with the Univ. of Tokyo, we conducted DNA analysis of deer droppings to investigate what they eat in different seasons. The results were astonishing.

During winter, the primary food source for deer turned out to be maples and dogwoods. However, both of these tree types are deciduous. This means in winter, there are no green leaves available to eat. Later, using footage from fixed-point cameras we confirmed that deer herds are feeding on fallen leaves. As you can see, the deer were in good condition and showed no signs of malnutrition.

Deer eating fallen leaves

If deer can survive on fallen leaves, then their food resources are virtually limitless. This discovery invalidates the once-optimistic assumption that if deer eat up all the undergrowth, they will eventually starve and their numbers will decline. We are now developing new strategies to protect forest biodiversity.

Experts involved in this Initiative

Hirao Toshihide

Lecturer, The University of Tokyo

A Possible Solution for Invasive Bamboo?

In our Natural Water Sanctuary Tennozan, a logging road was built alongside a bamboo grove. To protect the road’s embankments (norimen*1), we planted mitsumata (Oriental paperbush) —a species that deer do not eat.

Then, something unexpected happened. Along the sides of the road where mitsumata was densely planted, bamboo shoots stopped sprouting. It appears that mitsumata has an allelopathic effect*2 that inhibits bamboo roots. If this proves correct, it could be a breakthrough solution for controlling invasive bamboo across Japan.

• Norimen refers to the slopes created on both sides of a logging road.
• Allelopathy is the phenomenon where chemicals released by one plant influence the growth of other plants or microorganisms.

Mitsumata-edged road alongside a bamboo grove in our Natural Water Sanctuary Tennozan