Past plant diversity dynamics can provide a historical perspective on biodiversity change and ecosystem dynamics as a guide to conservation management in the future. Pollen analysis is one of the most widely used approaches to reconstruct plant diversity change through time, but the representativeness of pollen diversity to plant diversity is not yet fully understood and especially in open landscapes. In this paper, we compare pollen assemblages from topsoil in the open landscapes of the Tibetan Plateau with the surrounding vegetation to investigate their compositional similarity and the correlations between their diversity (richness and evenness), and to evaluate the influence of climate variables, landscape characteristics, and human disturbance on the pollen diversity. The results show that pollen assemblages vary obviously in different vegetation types and they can represent their surrounding plant communities at low taxonomic levels. Pollen richness boarders a better match with plant richness than pollen evenness with plant evenness across the whole study area, but the correlation is weak ( < 0.2, < 0.001). Transforming plants into their pollen equivalents has little improvement for the correlations between pollen and plant richness/evenness. Pollen richness and evenness can capture well the trend in plant richness and evenness along the vegetation gradient, suggesting that they can be used as gamma (landscape scale) rather than alpha (local scale) diversity metrics in the study area. Mean annual precipitation (MAP), mean annual temperature (MAT), and patch richness (PatchS) are positively associated with pollen richness. MAP, PatchS, and human disturbance (HD) are significantly predictors for pollen evenness. These confirm that pollen richness and evenness can provide insights into past plant diversity dynamics and help evaluating the effects of climate and habitat changes and human disturbance on long timescales.

中文翻译：

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青藏高原开阔地区现代花粉-植物多样性关系

过去的植物多样性动态可以为生物多样性变化和生态系统动态提供历史视角，作为未来保护管理的指南。花粉分析是重建植物多样性随时间变化的最广泛使用的方法之一，但花粉多样性对植物多样性的代表性尚未完全了解，特别是在开放景观中。在本文中，我们将青藏高原开阔地表土的花粉组合与周围植被进行比较，研究它们的组成相似性及其多样性（丰富度和均匀度）之间的相关性，并评估气候变量、景观特征的影响，以及人类干扰对花粉多样性的影响。结果表明，不同植被类型的花粉组合差异明显，可以在较低的分类水平上代表其周围的植物群落。在整个研究区域，花粉丰富度与植物丰富度的匹配度高于花粉均匀度与植物均匀度的匹配度，但相关性较弱（<0.2，<0.001）。将植物转化为其花粉等效物对于花粉和植物丰富度/均匀度之间的相关性几乎没有改善。花粉丰富度和均匀度可以很好地捕捉沿植被梯度的植物丰富度和均匀度趋势，表明它们可以用作研究区域的伽马（景观尺度）而不是阿尔法（局部尺度）多样性指标。年平均降水量（MAP）、年平均温度（MAT）和斑块丰富度（PatchS）与花粉丰富度呈正相关。 MAP、PatchS 和人为干扰 (HD) 是花粉均匀度的显着预测因子。这些证实花粉丰富度和均匀度可以深入了解过去的植物多样性动态，并有助于评估气候和栖息地变化以及人类干扰对长期尺度的影响。