Fig. 1 Illustration of nested sampling. The numbers indicate the sampling sequence.

Fig. 2 Systematic sampling sites for plant community inventory in the North China and the adjacent areas. The background shows the distribution of vegetation based on the Vegetation Atlas of China (1:1,000,000) (Hou, 2001).

Fig. 3 Illustration of vertical structure of the forest comm- unity (from Lin, 1990). The plot is located at Erliping, Cuian County, Fujian, at an altitude of 770 m above sea level. The species are: 1, Castanopsis eyrei; 2, Cyclobalanopsis glauca; 3, Lithocarpus harlandii; 4, Photinia glabra; 5, Symplocos confusa; 6, Rhododendron latoucheae; 7, R. ovatum; 8, Lasianthus chinensis; 9, Oligostachyum oedogonatum; 10, Eurya nitida; 11, Hicriopteris chinensis.

Fig. 4 Plot setting and quadrate coding for forest communities. The 20 m × 30 m plot is composed of six quadrates (A-F), each with an area of 10 m×10 m. The shadowed quadrates (S1 and S2) were selected for shrub layer investigation, and subplots (H1-5) were selected for herbaceous layer investigation. A buffering zone of 10-20 m at each side of the plot is necessary to keep the plot away from apparent human activities.

Fig. 5 Positions for measuring diameter at breast height (DBH) in different situations

Fig. 6 A photo illustrating measurement of tree height in the field

Fig. 7 Plot setting of shrub (grassland) communities. Five subplots (H1-5) were selected within each 10 m ×10 m plot. A buffering zone of 10 m at each side of the plot is necessary to keep the plot away from apparent human activities. For shrubs, whole plot (10 m × 10 m) should be investigated, and for grasslands, five subplots will be investigated.

Fig. 8 Plot setting of aquatic plant communities in deep water areas