Abstract:

Objective: By comparing population structure and seedling growth of Quercus acutissima among three different community types, the purpose of the study was to illustrate the quantitative and structural dynamics of Q. acutissima populations, in order to provide a basis for forest restoration and management in Qiaoshan forest region, southern Loess Plateau, China. Method: Field survey was conducted in 12 fixed plots(3 different stand types×4 reduplicates). All Q. acutissima individuals(DBH>4 cm) were measured for DBH(ground diameter for seedlings), height and crown width. Biomass of different organs was also measured for typical seedlings sampled from each plot. By substituting diameter class for age class, the static life table and survival curve were draw according to the survival amount of Q. acutissima in each diameter class. Differences among growth characteristics(height, ground diameter, crown width, and biomass allocation) of 1-10 years seedlings in three community types were analyzed. Result: The number of individuals tended to decrease with age in all of the three stand types of Q. acutissima, i.e. the low age classes displayed an absolute advantage in number of trees, indicating that the Q. acutissima population is progressive in Qiaoshan region. The static life table of the Q. acutissima population showed that the highest mortality rate occurred at younger diameter class indicating the phase was the most vulnerable stage in life history of Q. acutissima. The life expectancy was the highest in age classes ofⅠand Ⅱ. The mortality of Q. acutissima between age classes of Ⅲ to Ⅳ is far lower in mixed forest of Q. acutissima with broad leaved tree and mixed forest of Q. acutissima with Pinus tabulaeformis than that in pure forest of Q.acutissima. The survival curve of the different Q. acutissima populations was Deevey-Ⅲ type. The ground diameter of seedlings for 1-5 years were larger in the pure forest than in the mixed forest, with the increase of age, the ground diameter of seedlings in Q. acutissima with P. tabulaeformis forest was slightly higher than the other two forest types, but the difference was not significant. The crown width for 2-10 ages was larger in the mixed forest than in the pure forest, and the differences were insignificant among the three forest types in 1-3 years but significant after 4 years. The height of the seedlings of 2-10 ages in the mixed forest of Q. acutissima with P. tabulaeformis was larger than in the mixed forest of Q. acutissima with broad leaved trees and in the pure forest of Q. acutissima. The differences of seedling height among three forest types became significant after 5 years. The biomass of leaves, stems, branches and roots of Q. acutissima seedling in three forest types all increased exponentially with age. The effect of forest types on seedling organic biomass depended on ages(but for root biomass). The effects on leave biomass were insignificant at 1-6 years of age and significant after 7 years, the effects on stem biomass were insignificant at 1-4 years and significant after 5 years, and the effects on branches biomass were insignificant at 1-2 years and significant after 3 years. However, the effect of forest types on seedling root biomass was independent with age. Conclusion: Q. acutissima populations among three representative forest types in Qiaoshan forest region were all developed well with adequate regeneration ability. Although the quantity of young seedlings in pure Q. acutissima forest was relatively high, the mortality rate was also rather high, and the growth characteristics and biomass of older seedlings were lower than that in the mixed forests. The number of larger individuals with high quality in mixed forests was more than that in pure forests. We concluded that the construction of mixed forests has higher wood productivity and more stable community structure, which should be the main direction for forest management in the future.

Key words: Quercus acutissima, population structure, habitat, growth characteristics, biomass