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The genus Populus is composed of many species with an impressive variety of growth characteristics. Nevertheless, this abundant natural offering has been only partially utilized to date with the objective of promoting poplar breeding and cultivation. Following an old tradition, more or less inflexible production systems are mainly keyed to a few high-yielding P. x euramericana and P. x interamericana clones in most countries. Consequently, considerable economic failures have to be accepted repeatedly as a result of serious calamities.China ranks among the countries characterized by an exceptionally multifarious indigenous flora. Based on ample genetic variation, poplar species were able to settle in divergent habitats and to conserve the ability to survive and reproduce over long periods owing to adaptation processes. The diversity is concentrated, above all, in the subtropical mountain regions of southwest China. Comprehensive studies of the genus Populus in the southern and eastern mountain chains of the Qinghai-Tibet Plateau turned out to be particularly impressive; 3 sections, 17 species and 15 varieties have been recorded and taxonomically classified there. They grow at altitudes between 1500 m and 4300 m above sea level. Many of these poplar sources are notable for their remarkable site adaptation even in harsh conditions and also for their fast and vigorous growth.Species expected to be suitable for international breeding and cultivation objectives in the near future are presented in a general way. The necessarily subjective selection is based on the state of available knowledge mainly about site requirements, environmental importance, growth characteristics, regeneration ability, silvicultural behaviour, yield estimation and wood utilization. In particular, the following species are characterized in the paper in an abridged fashion: P. cathayana, P. davidiana, P. euphratica, P. simonii, P. szechuunica, P. ussuriensis and P. yunnanensis.The potential of poplars in China is considered to be instrumental in expanding and stimulating poplar breeding activities worldwide. Measures to be specified in the paper are considered important and could be implemented on the basis of a close and confident co-operation with Chinese colleagues and institutes relevant to the subject and under the umbrella of the International Poplar Commission.Key words: poplar, tradition, calamities, China, genetic variation, promising species, characteristics, breeding priorities Le genre Populus comprend plusieurs espbces dkmontrant une trbs grande variCt6 de caractCristiques de croissance. Neanmoins, cette abondance naturelle n'a Ct C que partiellement utilisCe B ce jour dans le cadre de la reproduction et de la culture du peuplier. Suivant une vieille tradition, des systkmes plus ou moins inflexibles de production sont principalement 21 la base du peu de clones B haut rendement de P. x euramericana et de P. x interamericana dans la plupart des pays. En conskquence, des Cchecs Cconomiques consid6rables dCcoulant de calamitCs sCrieuses...

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Investigations so far on the suitability of poplars for biomass production in short rotation periods in Germany were conducted almost exclusively with clones conceived for conventional cultivation. To introduce improved plant material, a special breeding program was implemented in Hann. Miinden. It takes into consideration the most important criteria of suitability for the new form of land utilization. A report is given on findings so far from the realization of this program. Comprehensive basic plant material is available for European, North American and East Asian species from the sections Aigeiros, Leuce and Tacamahaca. Interspecific crossings are being carried out mainly in order to make the best possible use of combination and heterosis effects. A period of at least 20 years is necessary to develop new cultivars with high yield performance and yield stability. First results are presented on hybrids of species which are site-tolerant, resistant and particularly fast-growing at the juvenile phase. Plans to produce multiclonal varieties, each with 5 to 10 suitable clones with the same growing rhythm are in place. Special cultivation recommendations advocate clonal mixtures for each of the most important site units and for different rotation periods of from 2 to 5, 6 to 10 and more than 10 years. Objectives and InvestigationsIn Germany, as in some other countries, the surplus of important agricultural produce has long been the reason for seeking new, economically reasonable and attractive possibilities for utilizing land. Chances for alternative forms of cultivation exist in particular when renewable raw materials which are utilisable in industry can be successfully incorporated into the farming enterprises' range of products. We attach considerable importance to lignicellulose in this connection.More than 15 years of investigations have been carried out in our country on the cultivation of fast growing tree species in short rotation periods of 2 to 12 years on land previously used for agricultural purposes. However, the focus of the research is based on only a few projects. Site requirements, growing behaviour and regenerative ability of poplars and willows have been tested, technical methods of piduction have been tried and the ecological consequences of this form of land utilization have been assessed (Muhs 1984; Weisgerber 1984Weisgerber , 1990 Dimitri 1988;Makeschin et al. 1989;Bohnens 1990).More information in areas such as timber harvesting (Loffler et al. 1988; Wippermann 1991), marketing and utilising the raw material produced (Patt et al. 1989;Buchholzer 1992) or concerning the economical, agropolitical and legal framework is clearly needed before large scale recommendations on the new cultivation form can be made. Most field results of production and utilization refer almost exclusively to already known products from the conventional cultivation of fast growing tree species.The yield potential of the most suitable poplar and willow clones under temperate climatic conditions in many countries is repo...

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