Forests

Forests are the most biodiverse habitat on earth. They also drive the terrestrial carbon cycle. Both important features of this biome reflect the biology trees. Technically speaking, trees are simply long lived plants that produce wood. My research examines how variation in wood traits, among others, connects forest biodiversity with climate change.


Why wood? | Forests on the brink | Why do forests vary? | What traits make trees sensitive?

How does wood decay? | What next?


Why wood?

Wood is a marvel of evolutionary engineering. It supports leaves high in canopies, transports water up from the roots and resists chemical degradation more effectively than almost any other tissue. All of this resilience belies the fact that intact wood in healthy trees consists primarily of empty plant cell walls built from just three chemical elements: hydrogen (6%), oxygen (42%) and carbon (50%). Wood stores carbon so effectively that when the first forests appeared 380 million years ago, atmospheric carbon dioxide concentrations plummeted over 50%, which reduced the greenhouse effect enough to plunge the planet into an ice age. Since then, woody plants have evolved from non-woody ancestors many times contributing to the impressive variation in wood characteristics among living tree species.

 

Forests on the brink Snags

Today, forests play a pivotal role as carbon cycling and climate change with human activity. In the decades around the turn of the last century, healthy trees in intact forests converted about a third of human carbon pollution into new wood and soil. Some of the carbon that forests did not absorb stayed in atmosphere where it enhanced the greenhouse effect and destabilized earth’s climate. Resulting extreme weather in the form of heatwaves, droughts and strong storms stresses trees and has sparked extensive forest dieback. As dead trees decompose, microbes release stored carbon back into earth’s atmosphere. Exactly how will determine whether and when earth’s forest carbon sink becomes a carbon source making climate change even more difficult to manage.

 

Why do forests vary? Path

To understand the role of plant trait variation in the forest carbon cycle, I have used a wide range of approaches and datasets. By applying multivariate statistics to forest inventory data, my colleagues and I showed that the strong relationship between forest productivity and species richness depends on how tree canopies shade shorter plants (Oberle et al. 2009). [figure] Similar relationships influence how adult trees versus saplings respond to soil gradients (Spasojevic et al. 2014) and how forest structure changes after logging (Osuzawa-Peters et al. 2015). 

 

What traits make trees sensitive?

In addition to studying why forests differ, I have examined how specific differences influence tree responses to extreme weather. As part of a NSF-funded project, I developed new statistical methods for measuring an important wood trait (Oberle et al. 2016a) and showed how this trait influenced tree mortality during a historic drought (Oberle et al. in prep). Those results informed a multidisciplinary effort to incorporate climate change science into regional forest management (Brandt et al. 2014). 

 

How does wood decay?

Forests change when trees die and they emit carbon when dead trees decay. My research examines how wood traits influence the trajectory of decay from snag to soil. Using national forest inventory data, I showed that the mechanical properties of wood in decks predict how long dead trees stand (Oberle et al. in review). Then, using a detailed inventory, I showed that falling dead trees can move considerable distance downhill (Oberle et al. 2016b), where wood from a broad range of species decomposes faster (Oberle et al., in prep, Zanne et al. 2015). Not only do dead trees emit carbon dioxide, but they also produce methane and even more potent greenhouse gas (Kovey, Oberle)

 

What next?

With colleagues at George Washington University, I am helping examine which microbes are responsible for breaking down deadwood. I look forward to working with students to apply similar techniques to the unique tree species and forest habitats of Florida.

 

When trees fall, they also threaten property and safety. I am working with partners to identify wood traits that make some species risky. Our goal is to put that information into the hands of tree care professionals so that they can help make our neighborhoods safer.

 

 

 

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