2023 HARPER PRIZE SHORTLIST: Throughout March, we are featuring the articles shortlisted for the 2023 Harper Prize. The Harper Prize is an annual award for the best early career research paper published in Journal of Ecology. Yikang Cheng’s article ‘Divergent trait responses to nitrogen addition in tall and short species‘ is one of those shortlisted for the award:

👋 About me

I was born and grew up in the southern part of China. I didn’t realize how special nature was in my teens until I went to University and started learning about botany and ecology. During my masters at Hainan University, I worked on tropical cloud forests and mainly focused on the community assembly mechanism. After that, I did my PhD at Fudan University on alpine meadow communities from 2019 to 2023. I conducted my PhD thesis on the effects of nitrogen addition on plant and root-associated arbuscular mycorrhizal fungal communities and their underlying mechanisms in an alpine meadow. In November 2023, I started working at Hainan University.

🔎 About the shortlisted article

The article ‘Divergent trait responses to nitrogen addition in tall and short species’ investigates the potential driving mechanisms for plant species loss of alpine meadow under nitrogen addition. Asymmetrical light competition and the direct detrimental effect of nitrogen have been proposed as two main mechanisms driving species richness declines following nitrogen (N) addition. N addition is also known to alter functional trait composition towards increased dominance of tall and fast-growing species. Thus, exploring the responses of plant species at different height strata may provide new insights into the relative importance of these two mechanisms.

To address this, based on a long-term N addition experiment conducted on alpine meadows (Fig. 1), we measured the natural height of 44 plant species and the photosynthetic active radiation at seven heights in the vegetation and identified a clear stratification of the plant community into tall species (>30cm tall), which experienced high light conditions, and short species that grew under the canopy, then we examined the responses of short and tall species to N addition.

We show that N addition significantly reduced species richness by enhancing light asymmetry, and had no direct effects, suggesting that N detrimental effects are negligible in our system. Consistent with this, we found different responses of traits and diversity for the tall and short species. Specifically, N addition reduced the number of short species but increased the number of tall species. In addition, specific leaf area increased, and leaf dry matter content decreased, for short species only, suggesting that they shifted to a fast growth strategy to cope with lower light levels. In contrast, tall species increased their height further to capture more light at the top of the canopy. 

Overall, our study is particularly important to the field for two main reasons: first, it provides an alternative and feasible way of detecting the role of light asymmetry in driving species loss under N addition. Second, it provides a new insight from the perspective of plant traits to explain biodiversity maintenance in the face of global changes, and highlights that understanding trait responses to global change requires a more detailed approach to fully predict how different species respond.

🌳 What’s next?

For the next three years, I will develop a new project that builds on the set-up of unique experiments in the species-rich tropical rainforest of Hainan Island. We aim to investigate the coexistence mechanisms of plant species with different mycorrhizal types driven by competition for above-ground light and below-ground soil phosphorus resources.

Find Yikang on ResearchGate.

Read the full list of articles shortlisted for the 2023 Harper Prize here.