Trees are stronger and tougher in hurricane-prone areas

On a fateful journey to the island of Dominica, researchers from Clemson and Harvard witnessed a landscape that seemed to have been ravaged by the merciless forces of nature. As they descended toward the airport, they gazed upon miles of forests filled with trees that resembled broken matchsticks. This was a mere nine months after Hurricane Maria, a Category 5 storm, had struck the West Indies island with devastating consequences.

However, upon closer inspection, the researchers discovered that while an overwhelming 89% of the trees had sustained damage, with 76% suffering major damage, a mere 10% were killed outright. Remarkably, many of the trees had already begun to resprout. 

Benton Taylor, a former graduate student in the Clemson Department of Biological Sciences who is now an assistant professor in the Harvard University Department of Organismic and Evolutionary Biology, commented on this extraordinary finding: “These hurricane-prone forests are, in many regards, incredibly resistant to even extremely powerful hurricanes. I don’t want to minimize the scale of damage that these forests received – it was immense – but the fact that 90% of the trees survived shows an impressive level of resistance.”

As the global climate continues to change, hurricanes have become more frequent and severe. This has serious implications for regions around the world that experience regular hurricane disturbances, as these areas often play crucial roles in carbon, water, and nutrient cycling and are considered global biodiversity “hotspots”. 

Hurricane Maria made landfall on Dominica on September 18, 2017, with winds reaching an astonishing 160 mph, making it the strongest hurricane on record to strike the island. Only days later, Maria laid waste to the U.S. territory of Puerto Rico.

Supported by funding from the Clemson Caribbean Initiative, Saara DeWalt, the Department of Biological Sciences Chair, Benton Taylor, and Dominican researcher Elvis Stedman embarked on a mission to remeasure and assess the damage inflicted on trees in nine forest stands across Dominica. These plots were originally established in 2006 by DeWalt and former Clemson researcher Kalan Ickes. 

In addition to taking measurements, the team also analyzed the wood density and carbon content of the 44 most common tree species, which they paired with tree measurements to estimate biomass and determine how much carbon had been relocated from living to dead matter by the hurricane.

The researchers identified stem snapping (40% of trees) and major branch damage (26% of trees) as the most common types of damage. However, the types of damage that resulted in the highest mortality rates were uprooting and being crushed by neighboring trees, with 33% of uprooted trees and 47% of crushed trees perishing. 

Surprisingly, as DeWalt pointed out, “snapping wasn’t as lethal as you might think.”

What the researchers found

The study also revealed that larger individual trees and species with lower wood density were more susceptible to snapping, uprooting, and mortality, while trees on steeper slopes were more prone to being crushed by neighboring trees.

DeWalt explained the potential implications of more frequent storms for forest composition in hurricane-prone regions: “Forests are adapted to this kind of disturbance, but we may see a shift in the types of species that are most common in these forests with increasing frequency of strong hurricanes. You might get more of the ‘live fast, die young’ species because you’re constantly resetting the forest.” 

This shift towards smaller, high wood-density species could have significant consequences for wildlife, particularly those that rely on larger trees for habitat and nesting.

Benton Taylor, another researcher involved in the study, underscored the importance of understanding the impact of hurricanes on tree populations: “Larger trees tended to suffer more damage and mortality. These large trees store immense amounts of carbon, and in Dominica, many of these large trees create unique habitats for animals, such as the parrots. The data we obtained on how different species and sizes of trees experience damage from hurricanes can help us predict the future of these forests and the many services they provide.”

While the study sheds light on how hurricanes can affect forest ecosystems, Taylor cautions against drawing direct comparisons between the forests of small, mountainous tropical islands like Dominica and those in the coastal plains and piedmont regions of the southern United States. 

“In a field where opportunities to study a phenomenon are rare – hurricanes themselves are rare events and it’s even rarer that one hits a forest plot that was measured before the hurricane hit – any additional data are useful,” he said. “That said, our study highlights that the effects of hurricanes can be very different based on the local topography and tree species that make up a forest. So comparing a small mountainous island populated by tropical rainforest trees to the forests of the coastal plains and piedmont regions of the southern United States should be approached with caution.”

The findings of this groundbreaking study were published in the March 2023 issue of the journal Forest Ecology and Management in a paper titled “Widespread stem snapping but limited mortality caused by a category 5 hurricane on the Caribbean Island of Dominica.” 

Alongside DeWalt, Taylor, and Dominican researcher Elvis Stedman, the study was co-authored by Professor Skip Van Bloem of the Clemson Department of Forestry and Environment Conservation and Assistant Professor Stefanie Whitmire of the Clemson Department of Agricultural Sciences.

Why some trees are stronger than others

Trees are a crucial part of the Earth’s ecosystem, providing us with oxygen, stabilizing the soil, and serving as habitats for various wildlife. However, not all trees are created equal when it comes to their strength and resilience. Some trees are better suited to withstand adverse weather conditions and other environmental stressors than others. In this short-form article, we will explore what makes some trees stronger than others.

One of the key factors that determine a tree’s strength is its wood density. Trees with higher wood density tend to be stronger and more resistant to environmental stressors such as wind, snow, and pests. For example, oak trees have a high wood density and are renowned for their strength and durability. In contrast, trees with lower wood density, such as pine, are more vulnerable to damage.

Another factor that contributes to a tree’s strength is its root system. Trees with deep and extensive root systems are better able to withstand adverse weather conditions such as high winds and floods. Additionally, trees with a robust root system are better able to absorb nutrients and water from the soil, allowing them to grow strong and healthy.

The species of the tree also plays a significant role in determining its strength. Some tree species are naturally more resilient than others. For example, redwoods and sequoias are famous for their ability to withstand high winds and earthquakes. These trees have evolved to survive in their specific environments and are adapted to the challenges they face.

Finally, a tree’s overall health is crucial in determining its strength. Trees that are stressed or unhealthy are more vulnerable to damage from environmental stressors. Factors such as water availability, nutrient availability, and disease can all affect a tree’s overall health and strength.

In conclusion, a tree’s strength is determined by a combination of factors, including wood density, root system, species, and overall health. By understanding these factors, we can better appreciate the resilience and importance of trees in our environment.

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