Evaluation of wood quality characteristics of the afforestation trees planted in China deserts as woody resources

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The purpose of this study is to estimate the amount of utilizable wood portion, that is, to evaluate the amount of juvenile wood portion within the trunks of the afforestation trees planted in arid or semiarid regions in China for combating desertification. The testing materials were collected from the two kinds of poplars stands, Populus simonii(Pos) as a native species and Populus beijingensis (Pob)as a hybrid species, and native pine (Pinus sylvestris var mongolica)(Pis)stands.First, wood quality characteristics were judged on the basis of the horizontal variation of two kinds of fiber length, that is, vessel-element length and wood fiber length. Good growth species of Pob showed 15 years earlier wood-quality maturation than that of slow growth species of Pos under non-irrigation conditions. Maturation age of Pos is promoted about 10 years under irrigation conditions. Slow-growth species of ~had large amount of juvenile wood portion, but this portion is able to reduce by promoting t … More he radial growth under irrigating conditions.Second, wood-quality variation was estimated by using vessel-diameter instead of fiber length. The vessel diameter is effective index for estimating wood-maturity within the poplar trunks, because horizontal variations of vessel-diameters showed similar tendency of vessel-element length and fiber length in Pos and Pob. The accuracy in decision of the demarcation of juvenile-and adult-wood, vessel diameter index is much better than vessel element length, because of less variation in each data plot.Third, crystals containing within the poplar woods, irrigated and no-irrigated Pos and Pob, were investigated. The crystals were existed intensively within the transition-wood region and heart wood portion, but none in sap wood portion. Native species of Pos had tendency to contain much crystals rather than Pob, however, this tendency is improved by applying irrigation.Forth, wood quality variation of Pis is very similar to the published data of pine trees grown intemperate zone. The maturing age was 23 to 25 years old. Less