Project Results

In older, unlogged rainforest of Hainan Island, China, leaves of saplings were larger, and fine root systems of saplings were thicker with fewer root tips than in historically logged areas. These results were consistent among 15 Angiosperm lineages, even though families differed widely in their leaf and root traits.

About This Project

Roots are an important, yet understudied, part of tropical forests. We need to better understand how roots vary with environment. We have measured fine root functional traits for 400 individuals of 50 tree species in Jianfengling, Hainan, China, to look at the root trait variability across a soil and forest age gradient. However, we do not fully know the range of soil environmental conditions across which we have sampled, so we are raising funds for laboratory soil analyses.

Ask the Scientists

What is the context of this research?

A recent interest by tropical forest ecologists to better understand belowground processes and their role in carbon cycling of tropical forests is developing. Norby & Iversen (2017) summarize what we know about roots, their biological functioning, and how that scales up to ecosystem-level processes. The favored approach in plant ecology, especially in diverse forests, is to use "functional traits" to help understand general trade-offs in plant strategies among the great numbers of plant species. We used a functional trait approach and sampled fine root traits for >400 individuals of >50 taxa in two forest areas (a 60-year old secondary and a primary) of a tropical island forest in China to see how variable root traits are.

What is the significance of this project?

We are at a crossroads in human history. Never before has human well being and the existence of mankind been so directly at odds with economics, resource-use and consumption. Despite the seeming doomsday scenario, there is hope. That hope lies in better understanding the effect and magnitude of rising carbon dioxide levels on the Earth's ecosystems. Scientific modelers, whose job it is to do just that, have identified a need for more data on belowground carbon pools (i.e. roots) (Kueppers et al. 2016). Modelers can use our trait based measurements, and a better understanding of how they vary with soil conditions and forest age to inform models that predict belowground carbon storage over time and across large areas of tropical forests.

What are the goals of the project?

This project has two goals. The first is examine how plastic root functional traits are within a species (i.e. among individuals). That is why we need to study several individuals of each species in each of the forest types. The recent trend in plant functional ecology has been along these lines, quantifying intraspecific variability rather than treating traits as point estimates. The second goal is to look at how root functional traits vary with forest age and across a soil gradient, which are related in Jianfengling. The primary forest area has nutrient-poor clay soils, whereas the secondary forest has sandier, more nutrient-poor soils. However, quantifying the soil nutrient concentrations in these areas depends on further laboratory analysis of the soils.