Researchers have long hypothesized that, by intensifying environmental stressors such as droughts or wildfires, climate change could make ecosystems more vulnerable to invasive plants. These plants may in turn alter the environment in ways which amplify the negative impacts of climate change. A new long-term field study conducted by the University of Florida (UF) has now offered the first experimental evidence to support this hypothesis.
The researchers exposed small plots of long-leaf pine to three scenarios: extreme drought, colonization by the rapidly growing and highly adaptable invasive plant congograss, and a combination of the two stressors. After waiting six years for the trees to grow under each scenario, the scientists added yet another stressor, fire, in order to test how each scenario affected the trees’ capacity of survival.
They found that the trees which experienced both drought and the colonization by invasive plants were least likely to survive after the fire.
“Less water meant the trees didn’t grow as tall. At the same time, the cogongrass, which is drought-tolerant, provided extra fuel to the fire, making it burn hotter and increasing the height of flames,” said study lead author Luke Flory, a professor of Ecology at the UF.
According to Professor Flory, the combination of shorter trees plus taller and hotter flames provided little chance of survival to the long-leaf pines. By contrast, in plots where the pines were able to grow taller or were not surrounded by the fire-fueling invasive plant, the trees fared much better and nearly all survived.
Experiments that show the complex interplay between climate change and invasive plants can provide essential information for land managers in fire-prone areas or regions where prescribed fires are used.
“In addition, these findings are one more reason why managing invasive plants is so important to conserving native ecosystems,” Professor Flory concluded.
The study, published in the journal Ecology Letters, is part of a larger global scientific effort called Drought-Net, which collects data from all over the globe to investigate how different ecosystems respond to extreme drought.