Basic situation In 2002, Jiangsu Nantong Medical College celebrated the school celebration and decided to carry out the greening transformation of the school. In March 2002, a greening program was established. In addition to the original 7 large cedars (3 DBH, 4 DBH), other tree species were removed, Manila lawns were laid on the ground, drainage channels, lawn lights, and automatic Sprinkler irrigation and other ancillary facilities. According to the transformation plan, a tender was conducted in April 2002. Finally, a bid was awarded for a greening project company (third-level qualification) as the successful bidder. Formal construction began on April 20, 2002, and specific construction plans were formulated in accordance with the requirements of the greening renovation program. First, the construction of drainage pipes, lawn lamps and automatic sprinkler pipes shall be carried out. Drainage pipes are excavated with a depth of 80cm for laying pipes, and lawn lights and automatic sprinkler pipes are excavated with a depth of 30cm for laying. After the completion of the laying of the pipeline, in May 2002, the construction of the soil and laying of the lawn began. First of all, the root shovel is used to remove the original weeds. As the flower garden is relatively low-end, in order to avoid flooding of the flowerbeds and cedar flooding, the soil from the school's Animal Center north of Tushan is used to make earth. The soil is about 20cm to 25cm thick (mixed with some pig manure), and the Manila lawn is laid after the leveling. In 2002, the rainy season in the area was ahead of schedule. In order to catch up with the construction period, it was sometimes necessary to carry out rain construction. The project was completed in mid-May. After the completion of the project, in order to ensure the survival of the lawn, the construction party often turns on the automatic sprinkler irrigation to water, sometimes the irrigation time is longer. After the greening project was completed, the appearance was completely renewed. It was once praised by teachers and students. In mid-July 2002, we suddenly discovered that there were some yellow abnormalities in the pine needles of the two cedar trees on the north side of the tender. We immediately invited relevant experts and professors from provinces and cities to the on-site consultation. They believe that: cedar is free of pests and diseases, mainly due to excessive filling of roots and laying of lawns, resulting in closed roots, poor ventilation, and excessive humidity in the roots, resulting in the decay of some fibrous roots, diminished supply function of fibrous roots, and continuous transpiration of high temperature crown transpiration. is too big. According to their opinions and requirements, we immediately took the following rescue measures: (1) remove the lawn, take soil 20cm, restore the original surface to ensure that the surface is loose and breathable; (2) dig deep trenches around the cedar, fill the stones to drain wet, give Cedar root ventilation and oxygen; (3) build shading sheds, trunks tied grass rope, reduce the amount of transpiration; (4) the morning and evening regularly spray water canopy, trunk, and regular spraying "Gao Mei Shi" nutrition solution; (5) Partially trimmed branches. After nearly half a year's rescue, it was still unable to recover. In the end, 7 cedar trees died, 5 died, and 2 survived, making people feel very sad. Analysis of causes According to expert analysis, the causes of cedar death are many, but the root cause is the lack of adequate understanding of the cedar growth habits and management of the construction process is not in place. The specific reasons are as follows: 1. Cedar is a shallow root tree species. Its fibrous roots grow within 30cm of the surface and absorb nutrients and water. The addition of 20cm to 25cm thick soil on the surface directly closes the oxygen absorption conditions of cedar fibrous roots, resulting in fibrous root rot. It is the root cause of cedar death. 2. Cedar is a kind of tree that is very humid and intolerant. It is suitable for growing on the plateau or in the hilly areas. It grows poorly or even dies when the water level is high or the water table is too high. Due to the construction period of the project, especially during the laying of the pipeline project, during the rainy season, the rainwater continued to increase. In addition, the tender area was close to the river and the river water increased, resulting in excessive soil moisture. After the completion of the construction of the pipeline, in order to catch up with the construction period, it is not necessary to cover the soil after draining the water in the trench, and then laying the lawn again. In order to ensure the survival of the lawn and open the automatic sprinkler irrigation for a long time, the soil in the marked low-lying soil has too much moisture and the water can not be discharged in time. The cedar root system is in a soil with excessive humidity for a long time, causing the fibrous root to rot. It is the main cause of cedar death. 3. Apply too much pig manure to the cedar roots. As the backfill was taken from the soil in the center of the animal center, a large amount of pig manure was accumulated on the soil. When the construction was completed, a large amount of pig manure was not backfilled with the soil, resulting in excess fertility around the roots, which was also an important reason for the death of the cedar. 4. The establishment of the construction plan has not been verified by experts, leading to serious mistakes in the construction plan, which is also an important reason for the death of cedar. Lessons Learned In summary, the main reason for the death of cedar was due to improper construction and management. As a greening manager, we must learn the following lessons from this: 1. Some greening construction programs must increase the procedures for expert argumentation. 2. Cannot simply pursue the low price bid in the bidding, and must also comprehensively examine and analyze the construction unit's ability, performance and work attitude. 3. During the construction process, site representatives must closely monitor all aspects of the construction period and timely and decisively handle technical and quality issues. Recently, many cases of cedar death due to improper construction have been learned from the media. Most of them are due to excessive filling of roots and laying of lawns, resulting in closed roots and poor ventilation, resulting in the death of cedar. This article is for reference of green workers to avoid similar accidents. (Source: China Flower Gardening Li Shidong)
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