The relationships between species richness and driving factors might vary with taxa and spatial scale. For this study we used plant species data of eight groups from nature reserves in China, namely pteridophytes, gymnosperms, angiosperms, vascular plants, Chinese endemic species, rare and endangered plants, woody plants, and herbaceous plants, and eight putative environmental predictors to explore the relationships between plant species richness and environmental factors at two spatial scales (temperate region and national scale). Our data suggested that area, mean annual temperature, and mean annual precipitation were the determinants of variation in species richness within these eight groups in the temperate nature reserves of Shandong Province in China. The relationships between plant species richness and environmental factors were consistent in different groups. However, the relationships between species richness and mean annual temperature varied with spatial scale. In the temperate region, species richness was negatively correlated with mean annual temperature and positively correlated with mean annual precipitation, whereas on a national scale species richness was positively correlated with both mean annual temperature and mean annual precipitation. Our study confirmed that the relationships between plant species richness and environmental factors in nature reserves were consistent in the studied groups and varied with spatial scale.