Size structure of canopy gaps in broadleaved Korean pine forests in the Changbai Mountains

Three kinds of models, which were used to simulate the size distribution of forest gaps of broadleaved Korean pine forests in the Changbai Mountains, were discussed in this paper. The effect of fitting was analyzed and goodness of fit of the models was evaluated. The results showed that most of the gaps consisted of small and medium-sized gaps with the occasional occurrence of large-sized gaps. According to our field survey data, areas of canopy gaps and expanded gaps in broadleaved Korean pine forests in Changbai Mountains accounted for 12.5% and 28.8% of total survey areas, among which gaps with canopy gap area of 20-100 m ^{and expanded gap area of 80-240 m2 made up of 80.7% and 81.8% of the totals respectively. The size structure of canopy gaps and expanded canopy gaps could be fitted by different unimodal functions with a peak skewed to the left. For the category of the canopy gap area distribution, only the Gaussian Model could be fitted, while for the expanded gap area distribution, all three models, ie the Log Normal Model, the 2nd Order Logarith mic Model and the Gaussian Model could be fitted. In order to evaluate goodness of fit of the models, R, R2, R2_adj, the standard error of the estimate, PRESS, the power of the performed test at α= 0.05 and goodness of fit were calculated. The entire evaluation process reached the same conclusion, ie the order of fitting the best model in descending order was the Log Normal Model, the 2nd Order Logarithmic Model and the Gaussian Model. The models fitted were all unimodal functions with a peak skewed to the left. Both Mathematically and ecologically, this skewness was explained by the fact that small and medium-sized gaps predominate in the broadleaved Korean pine forests.}