by
Hong Jusheng
Forest Research Institute of the
Chinese Academy of Forestry, Beijing, China
INTRODUCTION
China has 122 million ha of natural and man-made forests covering 12% of her total land area. The total forest volume is estimated at 9,500 million m3. The per capita forest volume is 10 m3 and the per capita forest area is 0.13 ha, both of which are well below the world average figures. The forest types vary from the coniferous belt in the colder northern latitudes to broadleaved monsoon and rain forests in the tropical zone in the south, and China is very rich in both coniferous and broadleaved genera, with an estimated 3,200 tree species.
Since the People's Republic of China was established in 1949, great importance has been attached to afforestation. Twenty-eight million ha have been planted during this period, of which six million ha are state-owned. In the northern provinces priority is given to the planting of farmland shelterbelts and windbreaks and to tree planting for soil and water conservation, while in the southern provinces more emphasis is placed on the establishment of fast-growing commercial forests. Some aerial seeding has been adopted in remote and sparsely populated mountainous areas.
In order to protect natural ecology and rare animals and plants, 57 natural reserves have been designated throughout the country, with a total area of 1.6 million ha, or 0.16% of the total land area.
Forest Tree Improvement
The vast scale of afforestation in China provides a wide scope for research in, and application of, all aspects of tree improvement. The first professional institution of forest tree breeding - the Department for Research on Genetics and Seed Selection within the Forest Research Institute of the Chinese Academy of Forestry - was established in 1952. In the early fifties research work was concentrated mainly on: (1) Hybridization and introduction of exotic cultivars in Populus; (2) Reproduction and seed zoning in Cunninghamia and Pinus; (3) Plus tree selection in Pinus and establishment of seed orchards; (4) Techniques for evaluating physiological quality in forest tree seeds. Research was largely suspended during the period 1966–1977 but was resumed in 1978, since when considerable progress has been made.
At present the following professional institutions are engaged in forest tree improvement in China: (1) Forest Tree Breeding Research Institute and Sub-tropical Forestry Institute under the Chinese Academy of Forestry; (2) teaching and research sections in forest tree breeding in the Northeast China College of Forestry, Beijing Forestry College and Nanjing Forestry College; (3) there are Forest Tree Breeding Research Departments in the Forestry Research Institutes in Guangdong, Jiangxi, Jiangsu, Sichuan, Hunan, Heilongjiang provinces; and (4) tree breeding research groups in all other provincial Forestry Scientific Institutes.
The professional personnel engaged in the work of forest tree improvement in the whole country are about two thousand in number. Our work falls under five main headings which are discussed briefly below: (1) Introduction of exotic trees; (2) Provenance testing; (3) Seed orchards; (4) Hybridization; and (5) Tissue culture etc.
(1) INTRODUCTION OF EXOTIC TREES
China is vast in territory. Variations in soil and climatic conditions and diversity in agriculture provide numerous opportunities for tree introduction.
Exotic trees have been introduced into China for over 1,000 years. Before liberation, most introductions were only for ornamental purposes and on a small scale. After liberation, introduction of exotic trees became an important work for wood production and roadside planting. Up to now, nearly 700 exotic tree species have been introduced to our country. Among them about 30–40 species have been widely used in afforestation. Poplars have been introduced from both Europe and North America. They include P. euramericana cv. 1–214 and Populus × euramericana cv ‘Sacrau 79’ in the central plains and Northern China; P. euramericana No. 63, 69 and 72 (Populus deltoides × Populus nigra) in the south, in the lower reaches of the Yangtze River, where they are very successful. We have planted them widely for wood and fibre. The introductions of Eucalyptus are important in China's forestry, especially in Guangdong province and Guangxi Zhuang Autonomous Region, i.e. the tropical and sub-tropical regions. Some Eucalyptus spp. were introduced to Guangdong at least one hundred years ago. So far about one hundred species of Eucalyptus have been introduced, but only three to five species are widely planted, i.e. Eucalyptus citriodora Hook, E. exserta F.V.N., E. robusta Sm., E. globulus Labill, and E. camaldulensis Dehnh.
Loblolly pine (Pinus taeda L.) and Slash pine (Pinus elliottii Engelm. var. elliottii) are among the most widely planted species in China. Approximately 130,000 ha of P. taeda and P. elliottii plantations have been established since 1972. P. elliottii has been planted in sub-tropical low hills at elevations below 300 m, P. taeda is planted between 200 and 500 m. Both species are widely planted in the Pearl and Yangtze river valleys. Some other southern pines have been planted also, such as Pinus serotina and Pinus palustris (long leaf pine). Some tropical pines such as P. caribaea and P. oocarpa have been introduced to southern China since 1964. Among the three varieties of P. caribaea (P. caribaea var. caribaea, P. caribaea var. hondurensis, and P. caribaea var. bahamensis), P. caribaea var. caribaea from Cuba is the best in growth and stem form.
Larix leptolepsis Sarg. from Japan is one of the most successful exotic species in China. It has been planted in some parts of Liaoning, Heilongjiang, Sichuan, Henan and Hubei provinces and so far has been successful. Further afforestation with this species will be continued.
Other successful exotic trees in China are Robinia pseudoacacia, Cryptomeria japonica, Taxodium distichum var. nutans and T. distichum, Liriodendron tulipifera, Carya illinoensis (Pecan), Juglans nigra, Casuarina spp. etc.
To summarize our experience in the introduction of exotic trees, the most successful donor regions for us are: the eastern part of N. America, Japan, southeast Asia and eastern Australia. The species from the western part of N. America and the Mediterranean regions have proved unsuccessful.
“Introduction of Exotic Trees in China”, written by the former deputy director of the Chinese Academy of Forestry, was published in 1983.
(2) PROVENANCE TESTING
The requirement of provenance testing in China was posed in the fifties. At that time the institute under the Chinese Academy of Forestry started to investigate the provenances of Pinus and Cunninghamia and put forward in a preliminary way the suggestion of division into districts for forest tree seed translocation. Later several species have been further studied, such as Pinus massoniana and Cunninghamia lanceolata. Most of the larger and better designed tests were initiated after 1977. Plans and leadership are now being provided for the provenance testing on a national basis by the Chinese Academy of Forestry. Up to now, we have carried out provenance testing on 24 species, including 17 coniferous species and 7 broadleaved species. Among them 16 species have been put into the national plan of science. They are:
Cunninghamia lanceolata (Chinese fir)
Eucalyptus spp. (E. exserta, E. citriodora, E. saligna)
Larix gmelini
L. leptolepis (Japanese larch)
L. olgensis
L. principis - rupprechttii
Pinus armandii (Armand pine)
P. elliottii (slash pine)
Pinus koraiensis (Korean pine)
P. massoniana (Masson pine)
P. sylvestris var. mongolica
P. tabulaeformis (Chinese pine)
P. taeda (Loblolly pine)
Platyeladus orientalis
Tectona grandis
Ulmus pumila
Other species being tested are: Pinus yunnanensis, P. caribaea, P. oocarpa, Robinia pseudoacacia, Paulownia fortunei, Populus tomentosa, P. simonii, Cryptomeria fortunei, C. japonica. The contents of experiment already arranged are: the overall comparison in performance between provenances; the interaction between provenances and environment; variation between provenances in morphology, phenology, growth, survival, cold resistance, disease resistance, pest resistance, biochemistry, chromosomes, etc.
At present, some results have been obtained on species included in the earliest tests, such as Cunninghamia, Pinus massoniana, P. armandii, Ulmus pumila, Tectona grandis and Pinus tabulaeformis.
(3) SEED ORCHARDS
The huge tree planting programme in China requires a bountiful supply of seeds. Those seeds are currently obtained from natural stands for indigenous species and from seed imports, also to a very limited extent from plantations within China. So we need to build seed orchards that will ensure production of high quality seeds.
The established research work on selective breeding and the set-up of seed orchards and nurseries of cuttings was started in the late fifties and especially after the sixties. In 1964 a resolution was adopted during the “First national academic discussion on selective breeding of elite forest trees” to engage in selective breeding systematically and to build seed orchards and nurseries of cuttings. With this came China's first seed orchards - Taishan County Hongling Pinus elliottii Seed Orchard in Guangdong province and Yangkou Cunninghamia Seed Orchard in Fujian province. The meetings of the National Elite Tree Association held in 1972 and the “working meeting on forest tree fine breeds” sponsored by the Chinese Forest Tree Company of the Ministry of Forestry all gave impetus to the development of seed orchard undertakings.
Since 1972 the work in seed orchards has made considerable progress in China. Up to now nearly 19,000 plus trees have been selected and 7,300 ha of grafted seed orchards, 677 ha of nurseries of cuttings, and 30,000 ha of seed stands have been established. At present 20 tree species have been used in selective breedings, seed orchards and cutting nurseries. Among them 13 were coniferous tree species and seven broadleaved. The main species are: Cunninghamia lanceolata, Pinus massoniana, P. tabulaeformis, P. sylvestris var. mongolica, P. elliottii, P. taeda, Larix olgensis, L. gmelini, L. leptolepis, L. principis rupprechttii, Populus spp., Ulmus pumila, Eucalyptus spp., Robinia pseudoacacia. Now we have started to collect seed from some seed orchards which were established in the earliest period, such as Cunninghamia, Pinus elliottii, P. taeda. Cunninghamia seed orchards can now supply 30% of the seeds needed for the annual planting programme of this species. As a rule the work of selective breeding is from phenotypic selection as a starting point, but now we have started progeny tests and have got some results already. On the basis of the results of progeny tests in some tree species we have begun to establish the improved first generation (1.5) seed orchard, e.g. in Cunninghamia, Pinus elliottii, and P. taeda; and in Fujian province a second generation seed orchard of Cunninghamia has been established.
(4) HYBRIDIZATION
A comparatively large scale of hybridization in tree species was carried out after the founding of the People's Republic of China. In the past thirty years we have done interspecific and intraspecific crossing in Populus, Pinus, Cunninghamia, Larix, Salix, Ulmus, Paulownia, Eucalyptus, Thea oleosa, Aleurites fordii, and Phyllostachys edulis, etc. The work of hybridization in some species has made considerable progress.
Populus
The work of Populus hybridization engaged by Prof. Xu Weiying in the Forestry Research Institute of the Chinese Academy of Forestry is characterized by its early development, large scale, numerous combinations and conspicuous achievement as compared with that of other species. We started with the interspecific crossing within groups and between groups of Populus nigra and P. cathayana, and now come to the interspecific crossing within the group of Populus alba, the cross breeding between Populus alba and other groups, as well as the cross breeding between the groups of Populus cathayana and P. euphratica. At present, the hybrids which are widely planted and conspicuously effective in afforestation in China are as follows: P. × popularis Hsu., P. simonii, P. simonii nigra var. italica Keohe No. 12', P. × pekineca Hsu, P. simonii × P. italica.
Salix
Regarding Salix hybridization, members of this genus are widely used for firewood and commonly planted for erosion control and stream bank stabilization. The extensive breeding and hybridization programme is mainly carried out in the Forest Science Research Institute, Jiangsu province.
The components of this programme include selection, hybridization, cloning and field testing. Recently some hybrids have been developed with fast growth and good stem form. Afforestation continues with this genus.
Pinus
In the early sixties the Teaching and Research Section of Forest Tree Breeding in Nanjing Forestry College started interspecific and intraspecific crossing of Pinus. The results of this research show that the first (F1) generation of Pinus thunbergii × P. palustris, P. thunbergii × P. yunnanensis and P. thunbergii × (P. elliottii + P. taeda + P. yunnannensis) possesses high heterosis (hybrid vigor). When six years old, it is 55–69% higher than the progeny from open pollination of the parental Pinus thunbergii and the amount of root and stem growth is 33–44% greater than the latter.
Larix
The breeding work of Larix is carried out in the Forest Science Research Institute of Heilongjian province and Northeastern Forestry College. Now some hybrids have been obtained. They are: Larix gmelini × L. leptolepis, L. leptolepis × L. olgensis. Some successes have been achieved in hybridization of other species, such as Eucalyptus exserta × E. robusta, Liriodendron chinense × L. tulipifera, Juglans mandshurica × J. regia, Paulownia fortunei × P. fargesii, Paulownia kawakamii × P. fortunei, and Aleurites fordii, Thea oleosa, etc.
(5) Tissue culture, etc.
Some scientific researchers in tree breeding in China are interested in tissue culture of forest trees. Questions range from methodology and research to overall philosophy and scope. Emphasis is now on propagating various Poplar species and their hybrids, Ulmus pumila and U. japonica, Cunninghamia lanceolata, Taxodium distichum var. nutans, Paulownia, Eucalyptus hybrids, etc. The Eucalyptus tissue culture has been put into commercial production in Guangsi Zhuang Autonomous region. We have done some work in forest tree genetics too, beginning with chromosome and karyotype analysis, as well as in the application of isoenzymes for the assessment of hybrids and provenance. For example, initial results of analysis and research in Cunninghamia karyotype have been reported. Headway has also been made in other aspects, such as protoplasm segregation, mutation breeding and breeding genotypes which respond to low light intensities.
To sum up, China's forest tree improvement is developing vigorously, and success has been gained both in solving problems in production and in studying scientific laws. Generally speaking however, our science is still young, our work still in the embryonic stage and many problems remain. Compared with the advanced countries in the world on forest tree improvement, we still have a long way to go. We would like to learn from them and are prepared to redouble our efforts.
Manuscript received in December 1984
