For the past month, we have been featuring all the articles that were shortlisted for the Harper Prize 2020. The Harper Prize is an annual award for the best early career research paper published in Journal of Ecology.
Feng Jiang’s paper ‘Tree mycorrhizal type mediates the strength of negative density dependence in temperate forests’ was one of the eight papers shortlisted for this year’s award.
I was born and grew up in a small village in central China. When I was a child, I used to plant seedlings of many fruit species. I started my PhD in 2018 at Northeast Forestry University in Harbin, China, supervised by Dr. Guangze Jin. From 2019 to 2021, I joined the Marc Cadotte’s lab at University of Toronto. In the summer of 2021, I will do my PhD defence. Then, I will move on to do a two-year postdoc at Peking University, where I will study global variation patterns of plant leaf traits.
Conspecific negative density dependence (CNDD) is regarded as an important mechanism to improve species coexistence in forest ecosystems. A stronger CNDD can impede conspecific density and increase species richness. Therefore, the variation of CNDD strength across species and regions is expected to determine species diversity across broad scales. Recent studies suggest that CNDD is stronger with decreasing latitude, whereas the CNDD tends to stronger for rare than common species with increasing latitude. Because tree mycorrhizal type changes with latitude and can influence the interactions between plants and soil biota, we hypothesized that the tree mycorrhizal type might influence the CNDD strength and CNDD-abundance relationships, which might explain these latitudinal patterns. In two temperate forest plots (9 and 9.12 ha) in Northeast China, we used survival data of seedlings and saplings to evaluate these two hypotheses.
The demographic data in these two life stages showed that tree species associated with arbuscular mycorrhizal (AM) fungi had stronger CNDD than tree species associated with ectomycorrhizal (EM) fungi. This result was consistent with the pattern that tropical forests dominated by AM tree species had stronger CNDD than temperate forests dominated by EM tree species. On the other hand, at the seedling stage, AM tree species showed a positive CNDD-abundance relationship than EM tree species, which meant that rare AM species had stronger CNDD than common AM species. These results were also consistent with those found by previous studies that CNDD strength was positively related to species abundance in tropical forests and negatively related to species abundance in temperate forests.
To generalize our results above, we then used sapling recruitment data of 15 temperate forests in the Northern Hemisphere and found consistent results. This research has been published in Ecology (Jiang et al. 2021, Ecology, 102, e03259). These results suggest that the distribution and turnover of tree mycorrhizal type across broad scales will influence biotic interactions, which may determine community structure and richness.
Plant functional traits can be different between AM and EM tree species, which will contribute to the difference of CNDD strength between them as we found above. Recently, we are using published datasets to explore whether and which fine root traits differ between AM and EM tree species at the global scale. This will help us to understand the role of functional traits underlying the contrasting ecological patterns and processes between AM and EM tree species. On the other hand, I will also explore the latitudinal variation of plant functional traits because I believe this will provide a good point to understand biodiversity pattern.
We announced the winners for the Harper Prize 2020 at the end of April, find out more on the blog.
You can also read all 8 shortlisted papers in our new Harper Prize 2020 Virtual Issue. These articles are free to read for a limited time!