Abstract:

The compositions of fruit types and their differentiation patterns with elevation of 1 943 wild angiosperms in Baishuijiang National Nature Reserve in Gansu Province were explored. The results show that the proportion of dry fruits is 65.67% and 24.60% in fleshy fruits in the area. The most three are capsule (26.56%), achene (12.35%) and drupe (12.20%) among 22 basic fruit types. Fruit types and their species numbers increase and then decrease with elevation. The proportion of dry fruits increases and it vanishes at 3 800 m or so in fleshy fruit with elevation. The proportion of capsule is dominant in each elevation segment and increases with elevation. It decreases and then increases in achene and caryopsis. It decreases in drupe and berry. It decreases and then increases in pome and samara. The cluster result shows that the elevation of 2 000 m is the distribution breakpoint of species numbers of basic fruit types. The vertical differentiation of fruit types may have occurred with changing of water and heat condition and their combined characteristic in corresponding altitude range as well as dissemination mode of fruits. Proportion relationship of fruit types can be used as one of the biological marks to reflect the region's climax on the premise that the classification system of fruit types can be perfected.

Key words: fruit types, vertical differentiation, hydrothermal condition, Baishuijiang National Nature Reserve