Abstract: Using the formulas of Levins niche breadth, Pianka niche overlap and the niche similarity, we analyzed the niche characteristics of 8 trees, 12 shrubs and 10 herbs within a Pinus tabuliformis forest in Manghe National Nature Reserves of Shanxi Province. The results showed that in the tree layer, niche breadth of P. tabuliformis (1.673) was the greatest, followed by P. armandii (0.737) and Platycladus orientalis (0.570). Species with larger niche breadth were Vitex negundo var. heterophylla (1.150) and Rosa xanthina (1.020) in the shrub layer, and Carex chinensis (1.520) and Artemisia giraldii (1.200) in the herb layer. Different degrees of overlap existed among the various layers with a gradual increase from the overstory to the understory. In the overstory, there were 2 pairs of populations with niche overlap being higher than 0.5, accounting for 7.14% of total pairs. There were 9 pairs of populations with niche overlap being higher than 0.5 in the shrub layer, accounting for 13.64% of total pairs, and there were 7 pairs of populations with niche overlap being higher than 0.5 in the herb layer, accounting for 15.56% of total pairs. All in all, species with larger niche breadth had stronger resource utilization capabilities, and their niche similarity and niche overlap were greater than other populations.

Key words: solar greenhouse, soil evaporation, crop coefficient, crop transpiration, water stress coefficient