What tree species are suitable for planting in Hunan, and what tree species have the highest cost performance.

We can consider developing eucalyptus. Several key problems of eucalyptus development in Hunan Province (Speech by Zhao Aiqun, Deputy Director of Hunan Forestry Department at the National Eucalyptus Cold-tolerant Variety Research Association and the Eighth Five-Year Summary Meeting (Excerpt)). ) 1 Introduction of Eucalyptus in Hunan Province 1. 1 Introduction History and Experience and Lessons Before the founding of the People's Republic of China, the railway department mainly planted eucalyptus as a roadside tree species along the Beijing-Guangzhou Railway. In 1950s, the forestry department introduced a variety of eucalyptus from Guangdong and Guangxi to start trial planting. By the mid-1960s, there was an upsurge of planting eucalyptus: the railway department planted eucalyptus in all directions along the railway south of the Yangtze River to solve the sleeper problem on the spot, the forestry department planted eucalyptus as a timber tree species, and the highway department planted eucalyptus as a greening tree species throughout the province to build eucalyptus nurseries and demonstration forests. Since the late 1970s, our province has strengthened the introduction research and experimental demonstration of eucalyptus. Up to now, eucalyptus has spread all over most counties and cities in our province, with a preservation area of nearly 50 thousand mu plus "four sides" tree planting. Loudi, Lingling, Hengyang, Chenzhou, Shaoyang, Changsha and Xiangtan are more preserved. Eucalyptus rubra and its varieties are the most preserved tree species, followed by Eucalyptus broadleaf, Eucalyptus macrophylla, Eucalyptus globulus, Eucalyptus angustifolia and Eucalyptus vitis. The better provenances of Eucalyptus rubra are transitional provenances such as Dukou in Sichuan, Guixi in Jiangxi and Kaiyuan in Yunnan. Eucalyptus preserved in our province has experienced many tests of strength and low temperature, showing strong cold tolerance, such as Eucalyptus rubra in Xinning county -8.8℃, Eucalyptus rubra in Hengyang suburb -7.9℃, and Eucalyptus rubra in Huarong county, northern Hunan province -9.6℃, with freezing weather for 9 consecutive days. And under the condition of poor site conditions and lack of management and protection, it shows the inherent characteristics of fast growth. For example, the 5-year-old eucalyptus globulus in Loudi City has a height of 18m and a DBH of 28.1cm. 9-year-old eucalyptus globulus, with the same height as 17 m and DBH 36 cm; Eucalyptus hongye 14 was born in Xiangxiang city, with a height of 17.5m and a DBH of 34.6cm. The 24-year-old eucalyptus hongye in Hengyang city is 26.6m high and has a DBH of 52 cm. In recent years, Central South Forestry College and forestry research extension units in our province have introduced more than 40 kinds of eucalyptus, among which the average DBH 10.7cm, average height 12. 1m and storage capacity of eucalyptus grandis planted in Zixing Dongjiang reservoir area are 63.04 cubic meters/hectare. Some achievements have been made in the introduction of eucalyptus in our province, but there are also profound lessons, that is, most of the eucalyptus introduced on a large scale in the 1950s and 1960s were destroyed by the cold damage of 1976. The main reason is that there is no tree species selection and introduction test. After suffering from cold damage, the whole eucalyptus tree species was simply denied without scientific analysis. As a result, some cold-resistant eucalyptus trees that did not freeze to death were also blown away, which seriously dampened the development of eucalyptus trees. This is a great lesson for the introduction of eucalyptus in our province. 1.2 Actively carry out eucalyptus introduction test and fine variety breeding. After eucalyptus suffered from cold damage, our province did not give up its efforts to introduce eucalyptus, and set up the provincial eucalyptus scientific research cooperation group and the eucalyptus professional Committee of the provincial forestry society to carry out various forms of eucalyptus introduction experiments and selection in an organized and planned way. 1.2. 1 Central South Forestry College takes the lead in selecting excellent tree species and provenances of eucalyptus, and selects excellent tree species and provenances for our province and the central subtropical region. This work was strongly supported by the Eucalyptus Research and Development Center of the Ministry of Forestry, and was included in the national "Eighth Five-Year Plan". At present, many tree species and provenances have been introduced from home and abroad, and experiments have been arranged all over the province, and observation and analysis are under way. 1.2.2 Study on the Selection of Fuelwood Energy Tree Species. This is a key scientific research project undertaken by the Forestry Department of our province. In this project, most families, genera and tree species in Hunan are selected as the research objects. Through cultivation experiments and tests, it has been shown that many eucalyptus varieties are ideal high-energy fuelwood trees. The final study shows that eucalyptus, masson pine and oak are the main species of firewood forest in Hunan Province. 1.2.3 Selection of excellent cold-resistant individuals of Eucalyptus rubra. Our province is located in the middle subtropical zone, which is the northern edge of eucalyptus development in China at present. Because of the terrain surrounded by mountains in the east, south and west and open to the north, the cold current in the north is easy to invade and stay in winter, so the winter temperature in our province is lower than that in other areas of the same latitude. It is an area with great hope of success and high risk of failure in developing eucalyptus. The key depends on whether there are cold-tolerant and suitable varieties. For this reason, we used the extremely low temperature screening method to screen the relatively cold-resistant Eucalyptus rubra varieties introduced in our province for many years, and selected the most cold-resistant individuals from the plants preserved at high and low temperatures for many times. We think that this method has a short period from breeding to production, and can quickly solve the problem of improved varieties developed recently; At the same time, the cold-resistant varieties selected locally have a greater grasp of the success of local development. This work is related to the overall situation of eucalyptus development in our province. Our office has set up a leading group for the breeding of cold-resistant eucalyptus varieties in the province to directly grasp this work. The province has formulated a unified selection plan and issued documents to municipalities to stipulate the selection work. Since 1988, our province has held a eucalyptus selection meeting every year to organize the acceptance of eucalyptus trees. Eight cities with more eucalyptus resources organized professional teams to select eucalyptus seeds. Eighty-nine superior cold-resistant trees were selected in the whole province and passed the technical appraisal on 1994. Clonal cutting nursery and seed orchard are being established at present, and 52 plants have been collected. Through clone identification test, it can be used in production soon. This work has also been strongly supported by the Eucalyptus Research and Development Center of the Ministry of Forestry and included in the national scientific research plan. 1.2.4 Carry out research and experimental demonstration on high-yield cultivation of eucalyptus. The Forestry Science and Technology Extension Station of our province has undertaken the sub-topic of the National Eighth Five-Year Plan key scientific research project "Density and Fertilization, Density Structure Combination" and the key extension project of the Ministry of Forestry "Popularization of High-yield Cultivation Techniques of Eucalyptus rubra and Eucalyptus macrophylla". Central South Forestry College, Hengyang City, Zhuzhou Forestry College, Changsha City, Zixing Forestry Bureau and other units have undertaken the key scientific research projects of "Eucalyptus Pilot Cultivation Demonstration" of the Provincial Science and Technology Commission. Test sites and demonstration bases have been established in the main site types in the south-central part of our province. All the experimental demonstration projects have achieved phased results, among which the eucalyptus pilot cultivation demonstration project is about to undergo technical appraisal. The general guiding ideology of developing eucalyptus in our province is: active and steady directional cultivation; Select suitable sites and trees and guide the classification; Superior varieties first, asexual use. 2. 1 actively and steadily cultivate short-term industrial timber forests such as eucalyptus needed for economic and social development in our province, which has already possessed the basic conditions and introduction basis for the development of eucalyptus, and can be successfully developed in a large area through efforts. Therefore, we should actively strive for development, but due to the unfavorable factors of low temperature in winter, we should proceed cautiously and steadily. We plan to go in two steps: the first stage, that is, the Ninth Five-Year Plan period, is the stage of seed breeding and experimental demonstration, and we should select improved varieties suitable for the development of our province, and establish seed orchards and clonal cutting nurseries. Further carry out high-yield cultivation experiments and establish high-yield demonstration bases. The second stage, from the Ninth Five-Year Plan to 20 10, is a large-scale and high-speed development stage, and it is necessary to develop 500,000 mu of various eucalyptus forests on the basis of the existing area. At present, the main raw materials for papermaking in our province are reed (400,000 tons/year) and Pinus massoniana forest (300,000 tons/year), and there are other grass raw materials such as Phyllostachys pubescens, kenaf, wheat straw, winter grass stems and Chinese alpine rush. The paper industry with broad-leaved forest as raw material is still blank. In order to improve the grade and economic benefit of paper, eucalyptus, a high-quality raw material, must be sought to replace or supplement it. The annual output of coal in our province is more than 30 million tons, of which rural collective and individual mining accounts for 5 1%. There are many small coal mines and many firewood pits, with an annual demand of more than 700,000 cubic meters, almost entirely relying on Pinus massoniana. Developing eucalyptus can reduce the mining cost and alleviate the excessive consumption of Pinus massoniana resources. Many wood-based panel enterprises in our province have fallen into economic crisis due to the lack of raw materials. There are160 thousand people in our province who lack firewood all the year round, and 52% of them lack firewood for more than 6 months. It is urgent to develop firewood trees with strong germination and high calorific value, which can be reused once planted. According to the needs of national economic construction in our province, the goal of eucalyptus directional cultivation in our province is to develop 654.38+million mu of pulp raw material forest, 654.38+million mu of coal pit forest, 50,000 mu of wood-based panel raw material forest, 200,000 mu of firewood forest, and 50,000 mu of shelter forest and soil and water conservation forest. In addition to the existing 50,000 mu, 450,000 mu has been newly planted. 2.2 Choosing trees for the right place and classifying them to guide our province's landform types are complex, and there are serious climatic and ecological differences among different landform types. Tree species must be selected according to site type. Therefore, the overall layout of eucalyptus development in our province is: key development areas in southern Hunan. Located in the county south of Yongxing-Yongzhou line, this area is a typical subtropical broad-leaved forest area. The extreme minimum temperature is above -5℃ all the year round, and -8℃ appears in a few places, but the annual frequency of this low temperature is extremely low. Rich water and heat are beneficial to the growth and development of eucalyptus. In the hilly area of this area, short-rotation cutting forests of Eucalyptus rubra, Eucalyptus grandis, Eucalyptus grandis pulp and sawdust are developed. Development of Eucalyptus grandis, Eucalyptus grandis and Eucalyptus dunnii pit wood forests in low mountain and hilly areas. Develop large-diameter timber forests such as Eucalyptus dunnii, Eucalyptus grandis, Eucalyptus grandis and Eucalyptus urophylla in low mountainous areas. Develop pulp forests of Eucalyptus bicolor and Eucalyptus rubra in mountainous areas. The hilly basin in central Hunan is the second gradient area of eucalyptus development in our province. Red soil purple soil hilly basin in south-central Hunan, namely Hengyang, Huo Ling, Hengnan, Qidong, Qiyang, Yongzhou, Leiyang and Yongxing. The annual average low temperature ≤-5℃ in this area is 0.3- 1.2 days, and the extreme minimum temperature is -6.4-9.3℃, but the annual frequency is extremely low. The area is densely populated, and there is a shortage of industrial and civil materials. Eucalyptus rubra, Eucalyptus dunnii and Eucalyptus grandis are planted in the hilly area of the basin in this area. Lianshao area in central Hunan is a famous coal mining area with obvious basin, with an average annual low temperature of ≤-5℃ for 0.6- 1.8 days and an extreme minimum temperature of -9.9- 12. 1℃. Since the beginning of this century, there have been low temperatures of-10℃ in six counties. This area mainly develops eucalyptus camaldulensis pit wood forest and firewood forest. The red soil hilly basins in central and northern Hunan, namely Ningxiang, Wangcheng, Liuyang, Zhuzhou, Xiangtan, Xiangxiang, Hengshan, Hengdong, Youxian and Chaling, have an average annual low temperature of ≤- 5℃0.6- 1.5 days. Since the beginning of this century, the temperature in seven counties has been lower than-10℃. This area mainly develops soil and water conservation forest, firewood forest, mixed forest of eucalyptus globulus, oak and pine or raw material forest of eucalyptus globulus and eucalyptus dunnii particleboard. Binhu district in northern Hunan. The winter temperature in this area is low, which is mainly used as the screening area for eucalyptus freezing domestication in our province, and the "four sides" green forest and firewood forest of Eucalyptus rubra, Eucalyptus dunnii and Eucalyptus branchii will be built on a moderate scale. 2.3 The focus of eucalyptus development in our province is to give priority to improved varieties and use cold-resistant improved varieties asexually. We have done some work in this regard and will try to solve this problem in the future. Eucalyptus is easy to hybridize and has a high degree of seedling differentiation, so it should be used asexually on the basis of improved varieties in production to achieve early fast growth and short rotation.