Li-ting Zheng: Functionally diverse tree stands with intensive canopy packing reduce herbaceous diversity and productivity

In this post Li-ting Zheng, a PhD candidate at East China Normal University, presents her recently accepted paper “Functionally diverse tree stands reduce herbaceous diversity and productivity via canopy packing.” She discusses the importance of tree functional diversity in shaping the dynamics of the understorey herbaceous community during the early successional period, and the importance of communication for those pursuing a research career.

About the paper

Tree and herbaceous species are two essential components of plant diversity that together drive forest productivity. Over the last three decades, numerous experiments have manipulated tree diversity to elucidate its impacts on forest productivity. One of the common (and limiting) features of such experiments is that tree species richness levels are maintained through the continuous removal of non-experimental understorey herbaceous species. Consequently, little is known about how tree diversity influences the natural dynamics of understorey herbaceous properties. Therefore, our idea is to examine whether and how tree diversity drives the temporal dynamics of understorey productivity, functional diversity, and composition.

A feature of the forests in Putuo Island. Photo credit: Enrong Yan.
A feature of the forests in Putuo Island. Photo credit: Enrong Yan.

To answer this question, we conducted a non-weeded tree diversity experiment, which was composed of eight tree species that differed significantly in economic strategies and covering 17 scenarios of tree species compositions in Putuo Island, located at Zhoushan Archipelagos in Eastern China. We investigated how understorey herbaceous diversity and productivity differed between 17 stands with continuously increasing tree species mixtures, assembled by species with different functional strategies (i.e., slow- or fast-growing).

The key finding of our work is that functionally diverse stands experience intensive canopy packing (and ultimately more shady conditions), thereby decreasing understorey productivity and diversity. We also found that the species composition of the herbaceous layer shifted significantly toward being dominated by species having a short stature (i.e., lower maximum plant height) and shade-tolerant leaves (i.e., larger leaf specific area), in response to low-light conditions due to increased canopy packing.

Compared with the previous traditional experimental study, our work highlights the significance of natural community processes in determining tree diversity effects on the temporal dynamics of previously neglected key biodiversity components (herbaceous species), which also play a critical role in shaping ecosystem functioning in forest ecosystems.

Setting up the tree diversity experiment at an abandoned agricultural field on Putuo Island, located at the Zhoushan Archipelago, in Eastern China. Photo credit: Li-ting Zheng.
Setting up the tree diversity experiment at an abandoned agricultural field on Putuo Island, located at the Zhoushan Archipelago, in Eastern China. Photo credit: Li-ting Zheng.

About the research

One of the biggest challenges in ecology, is to understand how changes in biodiversity affect ecosystem functioning. Much of the evidence for the plant diversity-ecosystem functioning relationships is drawn from biodiversity experiments, in which the realistic interactions between experimental and non-experimental species have been ignored by continuously removing non-target species. Such experimental managements put into question the generality of these findings for real-world ecosystems. Our study suggests that the consideration of realistic interactions between experimental and naturally occurring species is crucial for elucidating how natural community processes impact ecosystem functioning. From the ecological restoration perspective, the planting of functionally diverse tree species is vital for the maintenance of stable ecosystem structures and productivity during the initial stage of forest stand development.

Although our results come from young experimental plantations on abandoned fields, it is expected that the effects of tree functional diversity would also be relevant over time due to the increasing usage of canopy space. Longer-term experimental studies are still required to better elucidate the dynamics of tree diversity effects on the herbaceous layer. Moreover, the temporal dynamics of herbaceous layer properties can be further related to ecosystem processes such as productivity, stability, and multifunctionality. Future research studies should account for the interactions between experimental species and non-experimental species to gain a better understanding of the biodiversity-ecosystem functioning relationships under realistic situations.

Li-ting Zheng, PhD Candidate, East China Normal University
Li-ting Zheng, PhD Candidate, East China Normal University.

About the author

My undergraduate major was Ecology, and I had some experiences to explore and to understand the natural world at that time, which accordingly brought me into the field of Plant Ecology. Unhesitatingly, I had decided to pursue my PhD at East China Normal University in Shanghai, by focusing on vegetation ecology. Since then, I’ve started to go in-depth into plant functional ecology, and have tried to study the relationship between plant diversity and ecosystem functioning in forests from the perspective of functional traits.

Currently, I am studying at the ecology and biodiversity group at Utrecht University as a visiting PhD student, supervised by Dr. Yann Hautier. My primary interests are to understand the trait-based mechanisms of tree diversity-productivity relationships. In my PhD thesis, I attempt to reveal how tree functional diversity affects the natural dynamics of herbaceous layer properties, and also how herbaceous natural dynamics in turn influence the relationship between tree diversity and productivity. Moreover, I am interested in understanding how multitrophic interactions such as leaf herbivory mediates the relationships between tree functional diversity and ecosystem functioning in forests.

During the past five years for my PhD study, I also participated a lot of field works related to island vegetation surveys, with my advisor Dr. Enrong Yan. This experience contributes much to my knowledge about how the real world actually works, through carefully observing natural phenomena and frequent discussing scientific questions with my supervisor.

There have been no barriers in my research work. If I had to give one piece of advice to someone who is also doing his or her PhD study, it would be to efficiently communicate with both your supervisors and senior people in the field. Sharing your research works with good people around you, you will get a lot of constructive feedback and be able to improve your own research. Open your mind to communicate with others, you will find something that makes such a difference in both your research and other aspects of your life.

Enjoyed the blog? Now read the research!

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