Drones with spreaders and seed pellets help rescue and restore trees in mountain forests
Restoring landslide sites in mountain forests is not easy, because many places are hard to reach, let alone plant trees. The Soil and Water Conservation Bureau of the Council of Agriculture once used helicopters to fly over remote mountain landslide sites and scatter tree seeds, but it was almost ineffective, because the seeds were too light and the helicopter's main rotor was spinning, so all the seeds were blown away. The Forestry Bureau is now switching to operating drones, flying to designated locations, and then scattering specially made seed pellets containing seeds, so that the seeds land in the correct positions and the germination rate can be increased. Three test sites have now been completed, and the results can be accepted in July.
UAV drone technology is advancing rapidly and becoming more and more stable. In addition to spraying pesticides and surveying disasters, it seems it can also be used to restore mountain forests. The Forestry Bureau said that for landslides in some remote areas, because transportation cannot reach them, vegetation can only be restored through natural regeneration, but the waiting time is long, and during that period disasters are also likely to occur again. In order to accelerate the restoration of mountain landslide sites, experts were commissioned to develop seed pellets and a spreader mounted on a drone. Together with the drone, they formed a drone aerial vegetation team.
Wang Chao-pao, section chief of the Forestry Bureau's Watershed Management Division, said the seed pellets were developed by commissioned research at National Chung Hsing University, while the spreader that can be mounted on a drone and has a remotely controlled valve was developed by commissioned research at Feng Chia University. The seed pellets are about the size of large marbles. The seeds inside the pellets include both trees and grasses: bahia grass, tall fescue, Lespedeza bicolor, earleaf acacia, Taiwan red cypress, and so on. Each pellet contains about 390 seeds. The seed pellets are dried, so they can be stored for about 1 month. Upon contact with water they can immediately absorb water and germinate, so after the pellets are scattered and fall onto the soil, they will germinate when it rains. If they encounter rain within 1 month, the germination rate is highest; after 1 month, the germination rate may decline.
The drone chosen is a single-rotor helicopter, with a maximum wheelbase of 216 cm and a maximum takeoff weight including the body of 28 kg, so the maximum payload is 15 kg. However, in actual operation, only 8 to 10 kg of seed pellets are loaded, releasing about 700,000 seeds at a time, because when flying in mountain forests, wind shear in the mountains is a major problem, and if the body is too heavy, it will be more difficult to control. Although this single-rotor helicopter uses a fuel engine, its flight time is still limited, so a spreading area of 0.2 hectares requires at least 30 flights.
At present, 3 sites inaccessible to manpower have been selected for testing, including: the landslide site upstream of the Liumao'an tribe in Datong Township, Yilan County; the landslide site at Bitan Creek upstream of Deji Reservoir in Heping District, Taichung City; and the landslide site beside the 7K mark of the Aowanda access road in Ren'ai Township, Nantou County. The Forestry Bureau will conduct an aerial vegetation results survey 3 months after sowing, analyze the effect of this equipment and operation model on landslide site restoration, and compile the test results into an operation manual to provide for subsequent promotion and application, accelerating the restoration of landslide sites in remote areas of upstream national forest.
The Forestry Bureau's use of drone aerial vegetation operations
The helicopter flies to the designated location. After the spreader is opened by remote control, the seed pellets fall at the designated location, and they can germinate once rain comes.