Chaoqing Song: Tree demography in a moist tropical forest: Response to water stress and associations with plant functional traits

Chaoqing Song: Tree demography in a moist tropical forest: Response to water stress and associations with plant functional traits

In this new post, PhD candidate at University of Sun Yat-sen University, Chaoqing Song, presents his work ‘Differential tree demography mediated by water stress and functional traits in a moist tropical forest’. He shows the importance of water for tree survivability, highlights how functional traits can help us to understand demography, and thanks data collectors who help to enable science to advance. 

About the paper

Mortality, recruitment, and growth are important demographic processes that influence forest composition, structure, and function. Climate change has shown significant effects on these demographic processes. In this paper, we combined long-term forest plot inventory, meteorological observations, and trait measurements on Barro Colorado Island (BCI) in Panama to investigate how tree demography responds to different water conditions, as well as how plant functional traits contribute to interspecific differences in this response.

The idea of this study was inspired by previous studies. On the one hand, many studies have been devoted to exploring the magnitude, variability, and potential mechanisms of observed climate-induced tree mortality. On the other hand, an increasing number of studies have revealed the adverse effects of climate change on tree recruitment and growth. We thus aimed to provide a comprehensive understanding of climate-related variations in tree demographic processes, especially in terms of recruitment and population change.

Chaoqing Song checks labels on branches (credit: Chaoqing Song)

We calculated mortality rate, recruitment rate, net rate of change (the difference between recruitment rate and mortality rate), and relative growth rate (RGR) of 165 tree species between 1990–2014. Our paper indicated the role of water stress in driving the temporal dynamics of populations of species, with significant differences in mortality rate, recruitment rate, and net rate of change of species under different water stress conditions. In addition to the well-established growth-mortality trade-off, a growth-recruitment trade-off was also observed and this positive growth-recruitment relationship was stronger under low water stress condition. Additionally, our paper displayed the importance of wood density and P50 (embolism resistance) in determining interspecific differences in these demographic rates under both high and low water stress conditions.

About the research

This research could not be completed without the public sharing of relevant data. We thus sincerely appreciate Richard Condit and Stephen Hubbell, as well as the Smithsonian Tropical Research Institute for publicly sharing the plot inventory data and meteorological observations. The findings of this paper imply that tree recruitment is crucial for forest dynamics. In addition, fast-growing species, which exhibit large fluctuations in population change, pose a higher risk of forest functioning loss.

Members of our group (credit: Wenping Yuan)

Our next plan is to focus on the physiological response of trees to water stress. In our view, increase in mortality is only a result of trees responding to stress, and we need to capture the specific physiological processes and thresholds of trees when responding to water stress.

About the author

Chaoqing Song, PhD Candidate, School of Atmospheric Sciences, Sun Yat-sen University, China

I am a PhD candidate at the School of Atmospheric Sciences, Sun Yat-sen University, China. I enjoy walking a trail in the woods, appreciating the beauty and sounds of nature. This inspires me to get involved in ecology and to understand changes and processes that occur in nature.

Enjoyed the blogpost? Read the research here.

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