(VAN) Looking down from the green cypress forest, one can only see steep cliffs. Hikers walking ahead only see others’ tops of heads, and those behind can only hear others’ voices.

From the headquarters of the Phong Nha - Ke Bang National Park Management Board, one has to travel 40 kilometers (around one hour if rushing) to reach the mountain range where the evergreen cypress forest lies.

On the way to the forest, the Eight Ladies Cave marks a sacred place in the Annamite Range. The cave was named after youth volunteers who sacrificed during the resistance war against the US.

The Annamite Range is at the peak of its rainy season. The sky was clear and cloudless in the morning, so we took advantage of the nice weather and hiked early. Following Director Pham Hong Thai’s instructions, we headed straight towards Provincial Road 562 to the southwest. The higher the road, the more sinuous and steep it became. It was mostly 10% slopes, some parts were 13-15%.

After walking for hours, we saw houses scattering in the distance, marking our arrival at Ranger Post 39, named after Kilomet 39 of this 562 road. This is the Thuong Trach Forest Ranger Station checkpoint in Thuong Trach commune, Bo Trach district, Quang Binh province.

Seeing the car’s license plate from a different locality, the forest rangers understood the vehicle belonged to a working group. They helped us park the car, and came to greet us with warmth. By the table made from a monolithic rock, we discussed with the rangers about our work trip.

According to the park’s assignment, Mr. Le Quang Ngoc, a forest ranger, would take us to the evergreen cypress forest. Because it was almost noon, Ngoc reminded us: “The path up there is very steep, dangerous, and far away, so you should bring water and some snacks because you won’t return in time for dinner. We should go as soon as possible to avoid the rain, making it more difficult to get back here.”

We understood the situation and quickly prepared, stuffing our backpacks with food and drinks beside the cameras and extra clothes. Ngoc also noticed we wore sneakers, so he suggested changing to the rangers’ sandals. Otherwise, we would not be able to climb the mountains. So we changed, tucked pants into our socks, and secured it with a few rounds of tape to prevent slugs and jungle leeches. We embarked on the journey to see evergreen cypress trees.

About one kilometer from the checkpoint, a large sign “Evergreen Cypress Forest” signified the entrance. We arrived when the rain was light and the sky was gloomy, but we were still determined to enter the forest. Only if the rain turned heavy would we walk back.

Five humans walked through the foliage, crossed small slopes filled with fallen leaves and tree trunks with close attention, and finally reached the foot of the cliff. At this time, there were no more clear roads. We had to climb with two hands and two legs and follow ranger Ngoc. He had memorized the path after hundreds of patrols in the forest.

The precipice was sharp but sturdy. We followed each other and jumped up along the cliff. “Don’t be afraid and stressed. The more you brace yourself, the harder it is to climb,” the forest rangers spoke to us from above our heads.

Because of the danger, the whole group must keep a certain distance, staying neither too far nor too close (to avoid the person in front slipping and hitting the person behind, which might cause a series of accidents). The ideal distance was when one could see the heels of the hiker in front.

The 600-meter road took us one hour to traverse. As we stopped to rest, Ngoc picked up a tree trunk and said: “These are evergreen cypress leaves! We are standing at their roots, only 20 meters until we reach the forest. C’mon guys!” We shifted our sluggish bodies to see the gigantic cypress tree roots. A red color was revealed where the bark was scratched.

The steep cliff ahead of us made everyone hesitate. But we had come this far, so we picked up our belongings and also our spirits, following ranger Ngoc to crawl up the cliff. Only 20 meters into the forest, but we could not climb directly. We walked to the side of the cliff to find enough space to climb.

Passing the cliff, an evergreen cypress forest revealed itself. The tree canopies intertwined at an altitude of nearly 700 meters above sea level, covering the sky. As far as the eye can see, the evergreen cypress trees alternated with the rocky outcrops. Their trunks were imprinted with traces of time, and full of moss and mold.

Evergreen cypress (scientific name: Calocedrus rupestris) is a unique species that only grows on rocky mountain tops. They look like giant bonsai trees soaring high into the sky from rocky tips. Below, plump root clusters, winding like water flowing into the rocks, cling tightly and support tree trunks up to 20 - 30 meters high.

As if returning to a familiar place, Ngoc opened his eyes to the forest and pondered: “I don't understand how these evergreen cypress trees survive because the vegetation is insignificant and the water source is scant.”

He added that during surveys in this forest, scientists assessed that there were trees up to 500 years old. Another characteristic is the symbiotic ecosystem on the evergreen cypress trees. Their trunks are dense with mosses, ferns and even orchids.

One of us had his hand cut by scratching on rocks and thorns of the forest trees. Ranger Ngoc picked a bunch of unidentified moss on the cypress trunk and covered the wound. The bleeding stopped and the wound completely dried up.

On the limestone cliff, we squeezed into a small flat space of about two meters square. We took turns to find positions to record, film and capture the rare flora.

After work, as we ate and drank to recover from climbing mountains, ranger Ngoc carefully reminded us to put all the wrappers and bottles in our backpacks instead of littering there.

Climbing to the top of the mountain was rough, but climbing down was even more difficult. If climbing up requires you to use your hands and feet intuitively, then climbing down feels as if you are completely “blind,” not knowing where to place your body. Looking down from the cliff top, I occasionally thought, “Can I really get down?” If it were not thanks to Ngoc, we definitely would not have made it. The forest ranger was our eyes when we were blind, leading us back safely.

With quick and decisive movements, Ngoc found a firm place to hold on and then called out: “You guys sit down, hold on firmly with your hands and gradually move your feet down, I will show you where to put your feet. Absolutely do not look back. If you falter, you will fall.”

Then, he showed us every hole in the ground from the cliff so we could put our feet in and lean firmly to go down the mountain. “Try to synchronize your hands and feet, hold on tight before making a move,” Ngoc constantly reminded us.

There were parts where the cliff was too rough and some people couldn’t climb due to lack of experience; the ranger offered his thigh as a fulcrum for us. Indeed, without his kindness, it would be difficult for us journalists to get down the mountain safely.

After we passed the cliff and reached the slope, rain poured down in the Annamite Range. Under the forest canopy as thick as a shield, we quickly retreated down the mountainside regardless of the rain.

The 1.2-kilometer roundtrip took us hours: we started at 10 am; reached the mountain top at 11 am; then came back to the edge of the forest at 12:30 pm. We laughed: “Maybe it was the longest 600 meters since we were born.”

Phong Nha - Ke Bang National Park is the largest national park in Vietnam, with an area of 123,000 hectares, nurturing incredible biodiversity. It hosts the largest population of primeval evergreen cypress trees in Vietnam, with a total area of 3,000 hectares, accounting for nearly 2.5% of the entire forest area. This population is distributed on rugged limestone mountain terrain with many elevations greater than 80 degrees above the horizon.

Evergreen cypress (Calocedrus rupestris) was first discovered in Na Ri district, Bac Kan province, by Dr. Leonid Averyanov and colleagues in 2004, followed by more discoveries in Lang Son, Bac Kan, Ha Giang, Son La, Hoa Binh, Nghe An, Quang Binh. According to Averyanov and his colleagues, the rock cypress population in Phong Nha - Ke Bang National Park is considered the only primitive in Vietnam that has never been affected by humans.

Evergreen cypress has a relatively low height under the branches and a rough trunk shape. The body is relatively straight and evenly rounded when living in relatively flat terrain, The trunk is knobby and twisted when the tree lives in steep, rocky terrain.

The outer bark of the evergreen cypress tree often cracks longitudinally and peels off into strips along the trunk. Trees that live in places with high humidity and lack of light often have reddish-brown skin. The tree lives in dry, well-lit places and has silver-brown bark. The inner shell is bright pink, 4 - 12 millimeters thick, containing many large plastic pipes. The resin has a light yellow color and a very fragrant smell.

When fresh, evergreen cypress wood is light pink and relatively soft. When dry, the wood is light yellow, the grain is dark brown, smooth, and fragrant. Evergreen cypress wood is weighty (0.91 gram/cm3), and has a low shrinkage rate (5.3%) and average compressive strength along the grain (55.4N/mm2).

When the tree is young, the foliage often has a blunt conical, or inverted ovoid shape. Mature trees’ foliage is often irregular (round or ovoid). Evergreen cypress branches grow early, nearly perpendicular to the trunk, and point upward. The height under the branches of a mature evergreen cypress usually accounts for one-third to half of the tree’s total height.

Mature cypress trees are distributed on the slopes and peaks of limestone mountains in the Phong Nha - Ke Bang National Park with an average diameter at a breast height of 34.92 centimeters; an average towering height of 8.52 meters; an average canopy height of 3.33 meters and an average canopy diameter of 4.48 meters.

The population of green cypress in Phong Nha - Ke Bang grows concentrated in primeval forests of mixed broad-leaved and coniferous trees on the slopes and peaks of limestone mountains with a number of species belonging to the beech family (Fagaceae), laurel family (Lauraceae), and guttiferae family (Clusiaceae).

Evergreen cypress is distributed mainly in the Southwest, Northwest and Southeast exposure directions, belonging to primary forests on rocky mountains with forest status from medium to rich forest.

Research conducted at Phong Nha - Ke Bang National Park shows that the evergreen cypress is a large, evergreen tree. The cone season is from April to August, and the ripening season is from November to December.

The fruiting cycle and flowering ability of evergreen cypress are not homogeneous between years. In primeval forests mixed with broad-leaved and coniferous trees, evergreen cypress grows concentrated on the slopes and tops of mountains at altitudes between 572 and 820 meters above sea level, on limestone mountains with thin humus layer. High total organic matter content is rich in phosphorus, alkaline and poor in nitrogen.

The average density of the forest stand where the evergreen cypress species is distributed is 646 trees per hectare, of which the evergreen cypress species has an average density of 285 trees per hectare. The average forest reserve is 163 meters per hectare, of which the green cypress population has an average reserve of 131 meters per hectare.

Evergreen cypress is the dominant species and in the main canopy layer of the forest, including species typical of forests on limestone mountains such as upper cinnamon, saffron, Vietnamese star, and bamboo pine. The number of tree species participating in the forest formation formula is small (from 2 to 3 species), in which the evergreen cypress accounts for a very high proportion of the forest formation.

In Phong Nha - Ke Bang, 34 species of trees grow with the evergreen cypress, but only three species (green cypress, saffron and mango) often appear next to each other. There are 30 to 35 species of regenerating trees, of which five species dominate (from 50 - 60%).

Regenerated evergreen cypress usually accounts for the highest proportion with a very high density and rate of promising regenerated trees (from 72.76 - 91.48%), mainly concentrated at the height under 0.5 meters, divided clustered on the forest ground surface. The density of regenerated green cypress trees gradually decreases with height level. The higher the forest, the lower its regeneration density.

According to the assessment of specialized agencies, to protect and preserve the largest population of primeval evergreen cypress trees in Vietnam, the authorities should promote, educate and raise people’s awareness. Ethnic minorities living near the forest also play a crucial role in protecting the evergreen cypress population. People should consider evergreen cypress as an endemic tree species with an endangered conservation status - a heritage tree species - to manage and conserve with appropriate measurements.

Besides, specialists will continue monitoring the phenological characteristics of the evergreen stone cypress species; and conduct in-depth research on age structure, species succession, and populations to evaluate past changes in the environment and biodiversity, reflecting the current situation and future trends of the evergreen cypress population rocks at Phong Nha - Ke Bang National Park.

Specialists should further analyze the influence and interaction of environmental, ecological factors and vegetation structure on the distribution of evergreen cypress, especially climate change’s impact on the green cypress population.

They should select standard cells to monitor and compile records; monitor developments to evaluate the changing trend of the blue cypress population; determine trees with good quality, growth and development to be recognized as dominant trees; provide seeds along with testing propagation by cuttings and tissue culture to create a source of seeds for afforestation.

Accordingly, species such as saffron, Vietnamese star, mangosteen, and bamboo pine should be chosen to plant mixed forests with evergreen stone cypress.

Scientists also recommend to carry out silvicultural technical measures such as zoning off to protect forests, promoting natural regeneration, and additional planting in areas with old, hollow evergreen cypress populations with a high rate of rotten trees that are unlikely to self-recover.

Authorities should develop programs and projects to conserve the genetic resources of the evergreen cypress species; investigate and establish evergreen cypress forests; and select mother trees to collect seed sources to serve ex-situ conservation.

With climate change and global warming affecting global biodiversity, we must deploy synchronous solutions to conserve the species. We should also preserve and promote the values of the World Natural Heritage Phong Nha - Ke Bang National Park.