Abstract:

Aims: Herbaceous plants are an important part of plant diversity in temperate forests and play a critical role in regulating ecosystem functioning. However, the diversity patterns of understory herbaceous plants and their contributions to ecosystem functioning have long been neglected. Therefore here, we aimed to determine herbaceous plant diversity in temperate forests at different successional stages and tease apart the relative importance of woody plant mycorrhizal types and environmental variables in regulating the diversity of herbaceous plants.

Methods: Based on continuous two-years survey data from 128 herbaceous plant quadrats (1 m × 1 m) in temperate forests at two different successional stages (i.e., the secondary conifer and broad-leaved mixed forests (CBF) and the broad-leaved Korean pine forests (BKF)) in Changbai Mountains, we estimated the differences in diversity of herbaceous plant community, arbuscular mycorrhizal (AM) and non-mycorrhizal (NM) herbaceous plants in two forests. We also assessed the effects of AM and ectomycorrhizal (EcM) woody plants and environmental variables on the diversity of herbaceous plants using generalized linear mixed-effects model.

Results: Our results showed that the abundance and diversity of herbaceous plants at the community level and AM herbaceous plants were significantly higher in the BKF than those in the CBF, while there was no difference of NM herbaceous plants between the two sites. The abundance and diversity of herbaceous plants were significantly influenced by woody plant neighbors, but the effects of woody plant neighbors were dependent on environmental variables. In the CBF, the diversity of herbaceous plant at the community level and AM herbaceous plants were directly affected by the diversity of woody plant neighbors and leaf area index. The abundance of AM herbaceous plants was negatively correlated with density of EcM woody plant neighbors, but the negative effect of EcM woody plant neighbors reduced with increasing in soil moisture. In the BKF, soil moisture directly influenced the abundance of herbaceous plants at the community level and AM herbaceous plants, and the impacts of woody plant neighbors on the abundance and diversity of herbaceous plants was also dependent on soil moisture.

Conclusion: Overall, our findings indicate that forest disturbance could significantly decrease the abundance and diversity of understory herbaceous plants in temperate forest ecosystems, and provide insight into how the mycorrhizal types of overstory woody plant neighbors and environmental variables interactively modulate the community assembly of understory herbaceous plants.

Key words: herbaceous plants, successional stages, mycorrhizal fungi, species diversity