C3、C4植物及其硅酸体研究的古生态意义

本文概述了C₃、C₄植物生理、生态学意义、地理分布及其相应的植物硅酸体形态,进一步讨论了C₃、C₄植物硅酸体形态在我国表层土壤中的分布规律及生态学意义。最后,对洛川黑木沟全新世黄土剖面中C₃、C₄植物硅酸体形态变化特点做了分析,表明地层中典型的C₃、C₄植物硅酸体形态,作为古植物的直接证据,可以较准确地反映古植被、古环境的变化规律。

THE STUDY OF PHYTOLITHS IN C3 AND C4 GRASSES AND ITS PALEOECOLOGICAL SIGNIFICANCE

In terms of photosynthetic pathways, plants can be distinguished into C₃ and C₄ plants. The C₃ photosynthetic pathway is almost universally present in photosynthetic plants. The C₄ pathway occurs in some specially adapted warm season plants. The grasses in Gramineae family, as do other higher plants, also can be divided into C₃ and C₄ grasses. Festucoid, the representative of C₃ grass, is dominated at higher elevation and high latitude areas in northern and southern hemisphere, with lower temperature. The Chloridoid and Panicoid （mostly）, the representative of C₄ grass, are most abundant in the hot arid climates and in the semi-arid or arid regions of the world where high winter and summer temperature prevail. Study of phytolith of C₃ and C₄ grasses from more than 130 samples of the surface soils in China shows that teeth （including long, short, double-teeth, tri-teeth, multi-teeth and plate-teeth） and hat （flat-, cone- and star-shaped） phytoliths, which represent the C₃ grasses, are distributed mainly in northern China. The abundances of these two types increase gradually from South China to North China. The higher contents of phytoliths of C₃ plants were found in high latitude mountains and in cool temperate climatic regions such as in the northern Xinjiang and Kunlum Mountains. Dumbbell and short saddle-shaped or barrel-shaped phytoliths, the types of C₄ grasses: are abundant in South China and East China with bright sunlight, higher temperature and low anti intermediate elevations. The ratio of modern C₄/C₃ phytoliths has apparently decreasing tendency from 3.99 in central China to 0—0.04 in North China, which reflects the climatic changes and the effect of such change on plant population variations. The curve of C₄/C₃ ratio of loess profile at Luochuan, Shaanxi Province, in the northern China, is almost in agreement with the fluctuation of magnetic susceptibility. This implies that the ratio of C₄/C₃ phytoliths can be used as a new climatic indicator of paleoclimatic and paleoenvironmental studies.