关键词: 频次调查法, 巢式样方法, 植物多样性调查, 荒漠草原, 放牧

Abstract: Survey methods of plant diversity is a direct and critical factor affecting the result of plant diversity, which is often lack more attention in previous studies. We investigated plant diversity at different hierarchy levels by nested quadrat survey, high-frequency quadrat survey (1 m×1 m), and low-frequency quadrat survey (1 m×1 m) in a grazed desert steppe under four grazing intensities (i.e., no grazing, light, moderate, and heavy grazing). The results showed that the number of species, genus, family, and plant functional group significantly increased with the increase in survey area of the nested quadrat survey (P<0.05), but these indicators had no significant difference between the high-frequency and low-frequency sample survey. By balancing the accuracy of the study results with the time invested, for no grazing or lightly grazed desert steppe, either 4 m×4 m sample area or high-frequency quadrat survey could obtain accurate results of plant diversity;for moderately and heavily grazed desert steppes, at least 4 m×4 m sample survey was employed to obtain accurate results. These results indicated that the species composition of the grazed desert steppe varied greatly among the three survey methods. This study provides scientific support for evaluating and optimizing plant diversity survey methods in grazed grassland ecosystems, and provides theoretical basis for scientific and rational management of grazed grassland.

Key words: Frequency quadrat survey, Nested quadrat survey, Plant diversity survey, Desert steppe, Grazing