Structural characteristics of typical water conservation forests in mountain areas of Beijing.

We investigated 112 sample plots of water conservation forests in the mountain areas of Beijing in terms of their horizontal structure, vertical structure and soil texture, and summarized the structural characteristics of the entire water conservation forests as well as 18 typical forest types. The results showed that, in the mountain areas of Beijing, the natural conservation forests had mostly uneven-aged, double-layer and mixed structure at present; whilst the most plantation conservation forests had characteristics of even age, single level and pure species composition. From the view of forest stability, the structure of natural water conservation forests is advantageous over that of plantations in the mountain areas of Beijing.