Giant sequoias in the Sierra Nevadas get some of the nutrition they need thanks to Asian dust.

Giant sequoias in the Sierra Nevadas get some of the nutrition they need from dust that traveled from Asia. Photo: Shutterstock

People are largely used to thinking of ecosystems as separate and self-contained. But as scientists learn more about the Earth and how its myriad systems work together to give us the world we know, some things come as a surprise–like the relationship between giant sequoias and Asian dust.

The Sierra Nevadas are naturally low in phosphorous, which is required for plants to grow, and yet they give us the giant sequoia trees. The secret is that much of the phosphorus these trees are using is coming from Central Asia, as far away as the Gobi Desert.

“In recent years it has been a bit of a mystery how all these big trees have been sustained in this ecosystem without a lot of phosphorous in the bedrock,” said Emma Aronson of the University of California – Riverside, one of the authors of a study on this phenomenon. “This work begins to unravel that mystery and show that dust may be shaping this iconic California ecosystem.”

Dust, containing phosphorus, is picked up by wind and carried across the ocean, then deposited in the mountains of California. Dust tends to get up pretty high into the air, and not come back down unless it hits an object such as a mountain, so at higher elevations, the researchers found more dust from distant regions. The percentage of Asian dust found in the Sierra Nevadas, for example, ranged from 20 percent on average at the lowest elevation, to 45 percent on average at the highest elevation. They also found that more dust from Central Asia entered higher elevations later in the dry season than just after the spring rains.

This brings to light just how interconnected the world actually is, and how actions that impact one ecosystem can have impacts in other, sometimes quite distant, parts of the world. It also helps us to have a better idea of how climate change is going to impact these ecosystems.

“Considering we took our measurements in 2014, in the middle of the drought, this makes us think that the drought is a factor here,” Aronson said.

The researchers think their findings will be true in other mountainous ecosystems. If so, this could have tremendous implications for predicting forest response to changes in climate.