In this new post Gisele Biem, postdoc researcher at National Institute for Amazon Research and State University of Mato Grosso, presets her work ‘Ecosystem type affects how Amazonian tree species invest in stem and twig wood’. She talks about the importance of wood density for trees, discusses how traits can upscale to global C models, and shares the beauty of her study sites.
About the paper
Plant characteristics vary immensely between species. This affects their performance across different habitats, influences their spatial distribution, and determines ecosystem functioning. Wood density in particular is a key characteristic of trees because it influences how fasts trees grow, how they resist mechanical stresses against gravity and wind, and how they transport water from roots to leaves through their vascular system. Wood density therefore play crucial roles in tree longevity, growth rate, maximum size, drought resilience and other central aspects of the natural history of all trees. It is also an important determinant of ecosystem function and services. The productivity of forests and their dynamics are both linked to wood density, which in turn, influence how much biomass and biodiversity forests can sustain, as well as how much carbon they store.
Unfortunately, we lack wood density data for many species, especially in tropical forests where tree diversity is exceptionally high. Wood density also varies significantly across species and ecosystems, and explaining this variation can teach is us a lot about trees, the forest they compose, and the functions and services they provide. I wanted to understand the differences in wood density among different forest types in Amazonia, and I suspect that this variation would be pronounced because of large differences in soil and water conditions. We might expect differences in wood density to be an important aspect of tree’ suitability to the particular conditions of each habitat type. A unique twist to this question is that we included two types of wood density for each tree, wood density from its twigs, and wood density from its stems.
In this work, we showed that habitat-specific conditions to flooding and soil fertility are linked to differences in wood density in stems and twigs, reflecting contrasting ecological strategies that allow trees to survive in different environments. The fertile soils of Amazonian white-water floodplain forests (várzea) favored soft-wooded stems compared to non-flooded forests (terra firme), whereas the nutrient-poor black-water floodplain forests (igapó) invested in high-density stems and twigs. What was extremely interesting is that while most of trees have denser stems than twigs, some trees have denser twigs than stems, which was especially concentrated in igapó forests, and therefore associated with poor soil fertility and long flooding. That pattern may arise from the different functions of stems and twigs and suggests that these variations are crucial not only for tree performance across different habitats but also for influencing the amount of carbon and biomass they store, a variation which we do not account for in global estimates.
About the research
In this study, we collated wood density data of stems and twigs from 119 tree species and more than 1,000 individuals across three Amazonian ecosystem types. We combined field surveys with published data, and all samples were obtained following standardized protocols. Stem cores were obtained using increment borers at 1.30 m above the ground in each tree, while twigs were collected from terminal sun-exposed branches by a professional climber. A key aspect of our study is the inclusion of different habitats (forest ecosystem types) giving us a better perspective of the variability of the Amazon, whereas most studies are centered on non-flooded terra firme forests.
With our research, we could show how ecosystem conditions have a strong impact on the variation of wood density in trees, revealing contrasting strategies that are crucial for trees to thrive in diverse environments within the Amazon. We found it fascinating that trees can allocate resources differently to twigs and stems within the same individual. We are eager to explore this phenomenon further across more species and forests, to identify the specific drivers of these variations, and to understand how they are linked to environmental constraints. The next step for this study is to examine the anatomy of stem and twig woods for a more comprehensive understanding of the survival strategies of these remarkable trees inhabiting such diverse environments.
About the author
My interest in ecology began during high school, where my teachers inspired me to pursue a degree in biology at the São Paulo State University (UNESP), Brazil, a campus renowned for its ecological research. During my bachelor’s degree, I had the opportunity to participate in fieldwork campaigns in the Cerrado, Pantanal and Atlantic Forest. These experiences taught me the invaluable lessons that nature offers and deepened my appreciation for fieldwork. An obvious next step for me was to explore the Amazon, leading me to pursue my PhD at the National Institute for Amazon Research (INPA) in Manaus.
I am currently a postdoc researcher at INPA and at the State University of Mato Grosso (UNEMAT), focusing on community ecology, functional ecology and forest dynamics. The tremendous diversity of plant species found in nature amazes me. My primary interest lies in understanding the ecological mechanisms shaping community structure and dynamics, and their consequences for ecosystem processes, particularly in tropical forests. I understand that functional and forest ecology are key tools for addressing the causes and consequences of biodiversity change, and through my research, I hope to contribute to tackling the challenges posed by ongoing environmental alteration.
Like the blog post? Read the research here.
