[Species structure of natural secondary forest in the Wudaohe farm]

The analysis of soil thickness and slope gradient in natural secondary forest of the Wudaohe forest farm showed that the area of the secondary forest whose soil thickness was lower than 30 cm and slope gradient was higher than 25 degrees was 2390.1 hm2, covering 83.5% of its total area, while the area with soil thickness of higher than or equal to 30 cm and slope gradient of lower than or equal to 25 degrees was only 474.2 hm2, covering 16.5% of the total. It is suggested that the secondary forest is ecologically fragile, and this forest farm should develop a mulriple forest including waterhead-protection forest, lumber stand and economic forest. It was shown by analytic hierarchy process (AHP) that the suitable ratio of three forest types is 72.7%, 18.6%, 8.7%, respectively.