The megadrought in the Southwest is putting one of the most common conifers found in the West, the Ponderosa Pine, at risk. New research shows that the species is facing higher mortality rates because of the drought.
The Ponderosa Pine is essential the to local ecology. Lead author of the study and University of Arizona graduate Brandon Strange says the pine, like many plants, has a cooling effect to help make the atmosphere more habitable for plants. But what sets them apart is their influence on snow hydrology.
“How much snow is staying on the ground? How much is then melting and infiltrating into the soil? Things like that,” Strange said. “They can have quite a large influence on the local environment.”
Plants normally will have a system to help reduce water loss. The megadrought is challenging that physiological response.
“If you think of a tree as a giant straw from the soil to the atmosphere, the end of the straw would be like their leaves or needles,” Strange said. “So typically, they will try and pinch the end of that straw, the stomata, to reduce how much water they lose. But in the case of the current megadrought, what we're finding is they're still losing a lot of water despite employing their best efforts.”
The megadrought has decreased snowpack, which is essential to the viability of these forests, and increased temperatures. That could leave lasting effects on the iconic tree.
“If the drought keeps going, it's possible that those forests are going to start experiencing a lot of desiccation where they're just kind of drying out and then maybe, potentially experiencing mortality as well,” Strange said.
Researchers, including Strange, examined 17 different pines across the four corner states, including pines in the middle of the monsoon region–Southern Arizona and New Mexico. Those trees have been able to beat the heat, but monsoon rains might not be able to keep buffering the effects of the heat. These trees could soon experience hydraulic failure, where water loss from transpiration is greater than the uptake by roots causing them to collapse.