科尔沁沙质放牧草地植被分异规律的聚类分析

Cluster Analysis on Change Laws of the Vegetation under Different Grazing Densities in Horqin Sandy Pasture

通过野外放牧试验，得出如下结果和结论：①在不同放牧压力下，植被盖度、高度和牧草产量发生明显分异，其中连续轻度放牧下植被恢复明显，持续重牧下植被严重退化，持续中牧下植被随气候（降水）波动而变化；②在重牧条件下，群落中多年生牧草和适口性较好的一年生牧草相继退出，劣质一年生草占绝对优势；在封育和轻牧条件下，草地中多年生牧草和一年生牧草的优势度比值一般为２∶３，其中封育下的牧草地质量要好于轻牧区；中牧区牧草优势种更替较慢，多年生牧草与一年生牧草优势度比为１∶４左右；③沙质草地对放牧扰动十分敏感，一经放牧立即表现出明显变化，在不同放牧强度下草地沿着各自的方向演替，其演替速度不仅与放牧强度有关，更决定于放牧持续时间。

The results are got by field grazing experiment as follows: ① As the grazing density increases, vegetation coverage, height and forage production decrease obviously, of which degenerated grassland tends to recover under light grazing and the vegetation tends to deteriorate under overgrazing and the vegetation changes with climate change under moderate grazing; ② Perennial plants and palatable annual plants withdraw in succession from grassland and annual plants of poor quality dominate absolutely under overgrazing; Ratio of domination index between perennial plant and annual plant is 2∶3 under no grazing and light grazing; The change of domination plants is slow and domination index ratio between perennial plant and annual plant is 1:4 under moderate grazing; ③ Sandy grassland is very susceptible to disturbance in grazing, obvious change appears in the vegetation as soon as the grassland is grazed. The vegetation changes along individual direction under different grazing densities, and the speed relates to the grazing density, especially to the duration.