3种人工草地不同植被覆盖度实地测量方法比较

植被覆盖度是植被垂直投影面积占统计区域面积百分比;理想覆盖度实地测量方法耗时短,工具简单,结果准确,受人为因素影响小.以结缕草(Zoysia japonica)、白三叶(Trifolium repens)和雀稗(Paspalum thunbergii)人工草地为研究对象,以照相法测量值为参考,比较样线法、目估法、样针法...

Comparison of different plant cover investigation methods for three artificial grasslands

Plant cover is the percentage of the ground surface covered by vegetation material. An ideal plant cover investigation method should take minimum time, utilize easy-to-use field equipment, possess accurate results, and minimize interference from human operators. Three artificial grasslands, including Zoysia japonica, Trifolium repens, and Paspalum thunbergii, were explored in this study. The errors of eight investigation methods, including the line intercept, visual estimation, pin frequency, and point frame method, as well as the grid point method 1 × 1, and grid point method 5 × 5, grid method 1 × 1, and grid method 5 × 5, were compared for use in the three grasslands based on reference values acquired using the photographic method. The results showed that the line intercept method had errors of less than 5% and a low demand for field time and equipment. The visual estimation method had errors larger than the line intercept method;this method may be more suitable for short grasslands with very low or high plant cover. The pin frequency method had errors larger than the line intercept and visual estimation methods. The pin frequency method was mainly affected by the height and hardness of stems and leaves of plants, and is suitable for dwarf grasslands with low hardness. Most errors of the point frame method, grid point methods, and grid methods were greater than 10%. The errors of grid methods were affected by both plant cover and grid side length. The peak error of grid methods appeared on quadrats whose plant cover was approximately 65%, and the error increased with increasing grid side length. There were significant positive correlations(P < 0.05) between plant covers acquired by the eight investigation methods and those acquired by the photographic method, indicating that for similar artificial grasslands, the cover estimates of these methods could be transformed into the actual plant covers using the provided regression curves. With the increase in sampling quadrats, the errors decreased at first and finally reached a stable value. In summary, specific plant cover, height, and hardness characteristics of plants should be considered when choosing ground plant cover investigation methods in the future. This paper highlighted the line intercept method as a powerful technique for plant cover estimation of similar artificial grasslands.