The time processes of photosynthetic induction responses to various irradiances in Korean pine (Pinus koraiensis) seedlings grown in open-light environments and in understory of forest were studied in an area near the Research Station of Changbai Mountain Forest Ecosystems, Jilin Province, China from July 15 to August 5, 1997. The results showed that at 200 靘olm-2s-1 photosynthetic photon flux density (PPFD) and 500 靘olm-2s-1 PPFD, the induction time for the photosynthetic rates of understory-grown seedlings to reach 50% and 90% steady-state net photosynthetic rates was longer than that of the open-grown seedlings. The induction responses of open-growth seedlings at 500 靘olm-2s-1 PPFD were slower than those at 200 靘olm-2s-1 PPFD, but it was the very reverse for understory-growth seedlings, which indicates that the photosynthetic induction times of Korean pine seedlings grown in the understory depended on the sunfleck intensity.
Twenty plots were investigated on northern slope of Changbai Mountain at an attitude interval of 100 m (from 700 to 2600 m). The species co-possession between plant communities at different altitudes was analyzed by Jaccard index. The analytical results showed that the co-possession calculated according to species in different layers or all species between adjacent communities was higher than that between disjunct communities. The co-possessions between adjacent communities calculated by species in different layers had comparability and dissimilarity. If the two adjacent communities belong to different types of vegetation, then their co-possession was lower. The peak values and valley values of species co-possession between communities along elevation gradient just matched vegetation gradient patterns, and species subrogation of shrubs had more obvious rule on northern slope of Changbai Mountain. Co-possessions between communities with same altitude difference were much similar, and it decreased as the increase of elevation difference, which showed that species compositions in different layers of the communities were highly related.
Growth model is an efficient way to study growing process of some factors of plants quantitatively. Height growth of Korean pine (Pinus koraiensis) was studied by using Hyperbola equation, Logistic equation, Richards equation with three parameters, and Richards equation with four parameters in this paper. The results showed that Richards equation with four parameters was the most suitable and could be turned into other theoretical equations when some parameters were given different value. The maximum height of trees could be given in advance when using Richards equation with four parameters, and it was even more corresponding to reality. In addition, a height growth model with real height of fixed age as a parameter was discussed in this paper. This kind of growth model could be used to calculate height growth of a given tree effectively.
