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

摘要： 调查方法是影响草原群落植物多样性结果直接且重要的因素，目前研究中缺乏重视。在内蒙古放牧荒漠草原利用不同调查方法探究4种放牧强度下植物多样性特征。研究结果发现：巢式样方法中随调查面积的增加，不同放牧强度下群落物种、属、科的数量和植物功能群多样性类型和数量均显著增加(P<0.05)，但以上指标在高频次和低频次样方调查法间无显著差异。通过调查结果的准确性与投入时间的平衡，对于不放牧和轻度放牧荒漠草原，4 m×4 m样方或高频次样方调查法可获得准确的植物多样性结果。对于中度和重度放牧荒漠草原，至少4 m×4 m的调查样方才能获得准确的结果。这些结果表明不同调查方法对放牧草原植物多样性结果影响极大。本研究为评估和优化放牧草原生态系统植物多样性调查方法提供数据支持，也为放牧草原的科学合理地管理提供理论依据。

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