China is an agricultural country. It has to solve the imperative problems of feeding, clothing and housing its population of 1.2 billion people. In addition to their role in providing timber, important functions of forests are: sheltering of agricultural crops, improving the environment and enhancing soil and water conservation.
Since the eighties, the research program "selection and breeding of main forest tree species" has attained national priority with the following special areas: provenance testing, seed orchards, seed stands, clonal forestry as well as selection for non-timber traits. Until now, the most detailed studies were carried out on the geographic variation of the main conifer species such as Cunninghamia lanceolata, Larix spp., Pinus tabulaeformis and Pinus massoniana etc. It could be demonstrated that through careful selection of provenance, volume gains over 10 to 15 % could be expected.
The second generation of seed orchards of Cunninghamia lanceolata is already planted and nearly all of the seed demand of the intensive-care Cunninghamia plantations originates from seed orchards.
The selection and conservation of genetic resources of broadleaved tree species such as Populus, Salix, Ulmus, Robinia, Paulownia and others has been pursued as well. Over 100 various improved clones have been introduced to agroforestry and plantations; the volume gains are between 30 and 100 % or higher. For instance, selected hardy clones of Populus tomentosa may be cultivated in short rotation (5 years) for pulp and in 10-year rotation for veneer log even in the continental climate of Northeast China and Inner Mongolia. The average volume increment in 5-year rotation amounts to 15 m3/ha/yr. In addition, a number of natural and artificial allo- and autotriploid clones have been selected. A new selection program is currently initiated to breed further superior triploids.
Key words: tree breeding, conifer provenances, poplar breeding.
Correspondence: Zhu Zhiti, Beijing Forestry University, Beijing 100083, China