"Tree Doctor" examines trees and prescribes treatments
Beijing "Tree Doctor" has performed "physical examination" for more than 50,000 trees in East and West; risk early warning will be carried out in the future
On October 16, senior engineer Chao Yang from the Beijing Academy of Landscape Sciences placed a stress wave two-dimensional imager probe on an ash tree, outside the old Gulou Street, preparing to do a "CT" for the tree to conduct a void rate test.
A06-A07 version of photography (except for signature) / Beijing News reporter Hou Shaoqing
People have a cold and will go to the hospital to find a doctor. The trees are speechless. What should I do if I get sick?
In Beijing, there is a group of "tree doctors" who grasp the health and survival of trees early through "health diagnosis", tailor-made "treatment plans" to prevent fallen trees and dead branches from affecting city operations, and maintain the environmental protection of trees. And landscape function.
The Beijing News reporter learned from the Beijing Municipal Bureau of Landscaping and Landscaping that Beijing’s “tree doctors” have taken the lead in conducting “physical examinations” on more than 50,000 trees in the east and west cities.
Before the arrival of extreme weather, professional teams can observe and predict the trees that may have problems in advance, and intervene in time to reduce the loss of people and property caused by the fall of trees.
Auscultation plus CT
On the street outside the old Gulou, nearly one-third of the bark of a pewter plant has fallen off, and mottled mold spots on the trunk are clearly visible.
Its state caught the attention of Dr. Tree's team.
"Once a tree loses its bark, the fungus will directly erode the trunk and accelerate the decay of the trunk." Chao Yang, a senior engineer at the Beijing Academy of Landscape Sciences, used his fingers to squeeze the decayed trunk. The hard logs are already soft and a small piece of trunk is easily covered. Picked it down.
"The mechanical structure of the tree is destroyed, and its load-bearing capacity and bending resistance are greatly reduced. If it falls down, it is likely to hit surrounding vehicles. So we need to check to see if it is still strong."
After the "seeing", Dr. Shu began to "authenticate".
"Bang bang bang", Chao Yang hits the trees with a mallet. Normal and healthy trees will make a crisp sound, but the hollow trees will make a dull sound, which is called "abnormal sound."
Generally speaking, there are cavities under the trees and "solid" above the trees, which is more risky of falling.
Listen to the sound, this tree has holes, but how big is the hole?
It is difficult to infer from the appearance.
Chao Yang took out the "high-end equipment"-a two-dimensional stress wave imager, and prepared to make a "CT" for the trees.
He first measured the stem circumference of the tree, nailed the 8 probes of the imager into the bark at equal distances, "enclosed in a circle", connected the computer through the signal collector, and let the assistant tap the probes one by one.
In about 20 minutes, the computer "draws" a schematic diagram of the cross section of the cavity. "If the color of the picture turns yellow, it means it has begun to decay. If it is purple, it means there is a cavity. If the void rate reaches 50%, it is generally considered This tree falls easily."
Chao Yang explained that computer-aided two-dimensional stress wave imaging is used to detect hollows in tree trunks. A vibration sensor is installed in the probe of the imager. When the probe is tapped, the vibration rate is different in the healthy and decayed parts of the tree, and the hollow part is slower. , The instrument understands the size of the cavity by detecting the vibration transmitted in the material.
"What are you doing?" Throughout the morning, passing citizens looked at the street trees for "physical examination".
"We treat the trees, and we will provide a basis for the management of urban trees in the follow-up." Chao Yang said that when inspecting trees in the park, the tourists who inquired were even more frequent. "We will give everyone science popularization by the way."
Troubleshoot the "risk" tree
Tree doctor is still a new term in China, but it has a century of history abroad.
In 1924, the International Arboriculture Society put forward the idea of a tree doctor.
Why did Beijing introduce Dr. Tree?
Ma Hong, director of Beijing Municipal Landscaping International Cooperation Project Management Office (International Cooperation Office), said that Beijing's landscaping development has risen from "quantity change" to "quality improvement", and urban management and improvement of the ecological environment have become more refined.
Ma Hong introduced that from the 1960s to the 1980s, automobile exhaust and acid rain hindered the growth of Japanese trees. In typhoon season, trees often fell down.
Since the 1990s, Japan has begun recruiting and training tree doctors.
As of the end of 2019, nearly 3,000 people in Japan have obtained the qualifications of tree doctors to diagnose and treat trees, early warning of risks, and disposal.
"This is in line with the concept of'tree health diagnosis and early warning' introduced in 2016 by Beijing."
Ma Hong said that many of the street trees in Beijing's parks, old communities, and hutongs were planted in the 1950s and 1960s.
Like humans, trees can grow old and get sick, and diseased trees are at risk of lodging.
Whether it is a strong wind or a blizzard, after the weather changes suddenly, the risk of trees breaking and falling is greatly increased.
July-September is the most frequent season for sudden catastrophic weather in Beijing. There have been incidents of big trees being uprooted and hitting parked vehicles.
In addition to maintenance, diagnosis and treatment, the tree doctor also conducts risk investigation, pre-judgment and early warning, analyzes the growth of trees, and takes measures in advance to prevent fallen trees from crushing houses in alleys and hitting vehicles.
"There are also some trees that have rotted or hollow bark, which can be seen by naked eyes. Diagnosis and treatment of this kind of trees will also reduce the impact on the appearance of the city." Ma Hong emphasized.
Cultivate tree doctor "artisans"
Arbologists must master all-inclusive knowledge and techniques, such as tree physiology, soil diagnosis and improvement, diagnosis and response to meteorological disasters, and pest control.
In Japan, the entry threshold for this industry is very high, requiring more than 7 years of relevant work experience in tree research, diagnosis, treatment, and protection.
After Beijing introduced the concept of arboriculture in 2018, the International Cooperation Office invited Japanese experts to systematically train more than 130 people including Beijing tree management personnel, designers, pest control personnel, teachers and students of Beijing Forestry University.
As a representative of the maintenance company, Beijing Jindu Landscaping Co., Ltd. engineer Gao Faming participated in the training.
In his view, some of Japan's protective practices are worth thinking about.
"If we find new branches growing in the wound of the tree, we usually cut it to prevent it from consuming the nutrients of the tree. The Japanese practice is just the opposite. They will cut off the strong new branches, leaving the weak branches to continue to grow, so that the nutrients will be transferred. The direction of the wound is transmitted, allowing the wound to heal faster."
"Learning from Japan" is not entirely ethics.
"We conducted localized research on the detection and treatment indicators of Japanese trees, and finally formed a quantitative indicator suitable for Beijing tree species." Ma Hong introduced "pruning" as an example. Because the streets in Japan are relatively narrow, most of the street trees are thin. High morphology, while street trees in Beijing pay attention to width and shading, and hope that the canopy can radiate to a certain range, so in the pruning process, the indicators of the two sides are different.
In addition, Japan has frequent typhoons and has stricter requirements for tree void ratios, while Beijing has adjusted according to climatic conditions to make this index wider.
"The species of trees in the two countries are different. Our observations of pests and diseases will differ in leaf color and branches."
At present, the training has been carried out for two phases. The second phase of training has increased knowledge about tree growth, so as to predict the growth direction of branches in a few years and whether it will hinder the roof or pedestrian routes.
"Now, we are conducting health diagnosis for street trees and trees in densely populated urban areas. In the future, we will also include training on rehabilitation and restoration of high conservation value trees and ancient trees, including restoration techniques for local characteristic cultural tree species."
In this way, more than 200 people in the landscaping industry have received training.
"We have a wish to train some high-end craftsmen to reserve compound talents for the refined and high-quality development of the capital's gardens. They understand the theoretical knowledge base, know the technology, and also know how to operate." Ma Hong said, currently training personnel It is mainly based on experienced technical personnel, and then they will lead the garden and green chemical workers to carry out "practical combat".
50,000 "samples"
After the training, the tree doctors in Beijing conducted "practical operations" non-stop.
Due to the long time for planting trees in the old urban area, intensive personnel activities, and relatively more tree damage caused by human trampling, the tree doctor team was divided into 20 investigation teams in the two summers of 2018 and 2019, and took the lead in investigating the roads of Beijing’s east and west cities. More than 10 representative key garden trees in public places such as parks and green spaces have undergone a "physical examination".
Tree species include Pinus tabulaeformis, Ginkgo, Chinese Sophora, Populus tomentosa, White wax, Willow, Acer truncatum, Platanus vulgaris, Luan tree, Ailanthus altissima, etc.
In the hottest period of July and August last year, Li Hong and his classmates from Beijing Forestry University who participated in the survey wore sun hats and walked the streets of the east and west cities. They worked from 8 am to 4 pm every day, with four or five people. The team can measure more than 200 trees every day.
"If I work under a small tree, there is no green shade on the top of my head. It is very dry. The shade of the big tree is dense, but there are many mosquitoes. Even though I sprayed toilet water, I was still bitten by mosquitoes on my ankle."
According to Liu Yong, a professor at Beijing Forestry University, the diagnosis of urban trees is divided into three steps, namely preliminary diagnosis, appearance diagnosis and precise diagnosis.
The tree doctor first measures the tree height, tree diameter, crown width, observes its leaf color and growth, and checks whether the base of the trunk is loose, etc., and then taps the tree with a mallet, listens for abnormal sounds in the tree, and judges whether there is a cavity; The steel drill is inserted into the damaged part of the base of the trunk to check whether the tree is decayed.
Precision diagnosis is to use high technology such as imagers.
"We will also measure the height of the buildings near the trees, the distance between the trees and the buildings, to see if the trees affect pedestrians."
Liu Yong said that in Beijing, some Chinese Sophora japonica and Baiwa are "advanced" and they are 80 or 90 years old. "Middle-aged" trees are prone to withered branches, hollow trunks, decay, pests and diseases; trees in the "teenage" stage It may also be affected by the surrounding environment, soil and other factors, causing some health problems.
In addition, improper pruning can easily cause trees to rot.
This "physical examination" completed a total of 659 main streets in Dongcheng District and Xicheng District, with 54838 major trees, which accounted for about 60% of the total number of trees in East and West.
The results showed that the excellent and good rate of trees in the core area accounted for about 94%, and 6.01% of the trees had different degrees of trunk holes, rot, large dead branches, and more serious diseases and insect pests, which may cause potential damage to pedestrians, and corresponding treatment measures are urgently needed.
In this investigation, the team members used mobile phones to record each garden plant that had problems such as weakening of the tree, improper pruning, and disease and pest infection, and measured various morphological indicators of the tree, such as tree height, tree diameter, crown width, trunk straightness, etc. ; Record its growth environment in detail.
The data recorded by the mobile phone is instantly transmitted to the back-end database for information integration.
In order to accurately record the location of the trees, "tree doctors" will also use GPS, nail numbering, drawing and taking pictures to locate the trees.
"With the digital archives, we will carry out risk warning work for more than 50,000 trees in East and West cities next year." Ma Hong said that before the arrival of extreme weather, professional teams can observe and predict the trees that may have problems in advance. , Intervene in time to reduce the loss of people and property caused by falling trees.
There are also some trees that are at risk, and professional teams will conduct physical examinations on them again every 3-5 years.
This model will be promoted throughout the city in the future.
One Tree One Policy
Just like human beings, after a physical examination of trees is found, they need to be prescribed by doctors and treated with meticulous care. Some need to be coated with ointment, and some need to be "intubated". Trees like Sophora japonica need "plastic surgery".
According to Gao Fen, an engineer of Beijing Jindu Landscaping Co., Ltd., if the cut of the tree after trimming exceeds two centimeters, the arborist will apply healing agents, preservatives and bactericides to it to accelerate wound healing, and at the same time form a mucous membrane on the surface to prevent Rainwater enters and causes infection, "it's like applying a band-aid after applying medicine."
But if it is to repair the big tree hole, the process is complicated, and there are 7 treatment steps.
The tree doctor must first determine the location and orientation of the tree hole, classify and treat it.
"We first clean up the tree hole, clean up the rotten parts and garbage at the junction between disease and health. Then we will carry out insecticide and sterilization treatment and antiseptic treatment."
In the past, cement was used to fill tree holes. After the cement dries and hardens, the trees are very harmful.
Nowadays, arborists use polyurethane foaming agent, which has elasticity and can adapt to the growth of trees.
After the tree hole is filled, it needs to be fixed with fiber cloth or thin steel wire mesh, and then the hole is sealed with silica gel, but if the color of the plug is too abrupt, it will be like a scar.
In order to make the trees look natural and healthy, Dr. Tree used his brain.
"Different tree species have different bark colors, ranging from grayish brown to turquoise. We adjusted the silica gel to the corresponding color and painted the bark texture. The tree hole repair creates a natural fluid effect based on the tree shape, making the trees more beautiful. "
Soil improvement is also an important treatment.
The doctors found that some pine trees are growing weak, their needles are yellow, and the new branches that grow out every year are very short, and some even stop growing.
The reason is that the soil is stepped on too densely, the soil is compacted and has poor air permeability, and the root system cannot breathe.
"In order to change the soil, we developed a new utility patent, which is to insert a ventilation tube into the soil at the root of a tree." Gao said that the ventilation tube is about 60-80 cm high, and the exposed part is only 3-5 cm.
Arborists can deliver oxygen to the roots of trees through tubes.
Today, the diagnosis and treatment of trees has achieved initial results.
“Last year, we found that the ginkgo leaves on Sanlihe Road were small and there were scorched leaves. Through the application of deciduous tree rejuvenation substrates and burying soil ventilation pipes and other soil improvement technical measures, the ginkgo leaves there were significantly larger this year, and the trees did not fall in advance. The symptoms of weakness disappeared."
Gao said that for the prevention and control of diseases and insect pests, tree doctors use the TCM idea of "incurable diseases and prevent diseases", and adopt comprehensive technical measures such as biology, physics, and chemistry to maintain and health the trees, improve their own immunity, and prevent diseases and insect pests. Occurrence of, make it less disease and insect pests, or make biological disasters in a controllable range.
If the tree is already sick, the tree doctor needs to treat it according to the symptoms, prescribe the right medicine, and choose high-efficiency, low-toxicity and environmentally friendly agents for prevention and treatment.
Beijing News reporter Zhang Lu