Diverging shifts in spring phenology in response to biodiversity loss in a subtropical forest

Prepared by Yanjun Du, Bo Yang, Si‐Chong Chen & Keping Ma

Evidence of climate change has been widely documented in the Northern Hemisphere, particularly linked with anthropogenic forces. It is well recognized that anthropogenic climate change has already begun to affect global biodiversity and phenology. Despite our increased understanding of how abiotic factors influence plant phenology, it remains poorly studied whether the loss of diversity could alter the phenology. If spring phenology shifts with the biotic factor, future changes in spring phenology could be much bigger than would be expected from global warming alone.

Our study provides the first empirical evidence concerning the effects of biodiversity loss on plant spring phenology for woody species. We conducted the study on the platform of the ‘Biodiversity–Ecosystem Functioning Experiment of China’ (BEF -China) in East China. In total, 40 different native broad-leaved tree species were planted in various combinations to create plots with tree richness levels of 1, 2, 4, 8, 16 and 24 species. Results showed that reducing the number of species in this forest ecosystem can cause a shift in leaf-out times. Leaf-out date advanced an average of 0.3 days per species lost, indicating that the magnitude of the advancement in leaf-out date under global warming is equivalent to the loss of seven species in this subtropical region. Our findings illustrate that biotic interactions, or how plants interact with each other, influence phenology in a way that is critical to understanding the combined anthropogenic effects on spring phenology.

However, we found diverging shifts in spring phenology in response to biodiversity loss, with two species leafing out earlier in the low diversity plots, one leafing out later and four showing no significant difference. The magnitude of this change in leaf-out timing is less than the magnitude of flowering times shifts in a grassland ecosystem in California by Wolf, Zavaleta and Selmants (2017). They found biodiversity loss shifts flowering phenology at same magnitude as global warming.

The observed changes in leaf-out date may be mediated by changes in the physical environment, such as soil temperature, soil moisture or nitrogen availability. It could be due to resources that are freed up by the loss of other species, but we have not yet been able to test that experimentally. We found abiotic variables were more important than biotic variables (species diversity) in determining leaf-out dates in this subtropical forest. For flowering time, neither loss of diversity nor abiotic variables had significant effect. Altogether, our findings indicate that declining diversity could exacerbate the phenological changes attributed to rising global temperatures.

References

• Wolf, A. A., Zavaleta, E. S. & Selmants, P.C. (2017). Flowering phenology shifts in response to biodiversity loss. Proceedings of the National Academy of Sciences, 114, 3463–3468. (https://doi.org/10.1073/pnas.1608357114)

This is a plain language summary for the paper of Du et al. published in the Journal of Vegetation Science (https://doi.org/10.1111/jvs.12806). This post was prepared by the main author of the paper, Yanjun Du.