Strange response in desert plants to global warming

March 28 () –

In the hottest desert in North America, climate change is causing the decline of plants considered near-immortal and replacing them with shrubs more adapted to the new environment.

Many studies have documented how a hotter and drier world is causing a redistribution of plants in temperate montane regions. A new investigation of the University of California Riverside (UCR) documents the unexpected ways in which plants in part of the desert of snow they are doing the same.

“Plants are changing, but in strange ways,” he said it’s a statement Tesa Madsen-Hepp, first author of the study and PhD candidate in ecology and evolution at UCR. “We thought most of them would move to higher elevations with cooler temperatures. But while some lower elevation trees are declining and moving upwe’re also seeing some other species moving into the warmer parts of the desert.”

In addition, the researchers believe that the trends they observed are likely to continue despite extreme rainfall in recent months. “It’s really the warmer temperatures that cause the most stress for these species, and one year of rain is not going to mitigate the long-term drought trajectory,” Madsen-Hepp said.

Published in the journal Functional Ecology, the research not only documents how some types of plants move downward in elevation, rather, it examines the physical characteristics of those plants to explain why the change occurs.

To make their observations, the research team visited the Boyd Deep Canyon Desert Research Center, just south of Palm Desert, in 2019. The research area spans a range of 2,700 meters from the desert to the mountaintop. through which they traveled from top to bottom sampling plants. This same area had previously been examined by ecologists in both 1977 and 2008, providing a basis for comparison with the most recent findings.

“Species that we normally think of as fairly stress-tolerant, such as California juniper and pinyon pine, are either declining or increasing. And while they are increasing, they don’t seem to be thriving in their new locations.“Madsen-Hep said. “Moving to their former low-elevation haunts are plant species with shallower root systems, such as frankincense, donkey grass and ocotillo.”

In addition to root systems that are less dependent on water from deep soil, which is increasingly scarce, these smaller plants are also able to grow faster and invest fewer resources in their leaves.

“These are more weedy species. They have ‘cheaper’ leaves in terms of the carbon cost to produce them, and are drought deciduoussaid Marko Spasojevic, lead author and assistant professor in the UCR Department of Evolution, Ecology, and Biology of Organisms.

“In other words, they can drop the leaves when conditions get too stressful and wait out the drought.”

Plants that keep their leaves year-round tend to invest in thicker leaves with higher carbon content. They are at a disadvantage compared to plants that detach more easily. When plants shed leaves, the atmosphere can no longer draw water from them, relieving the demand on the roots to provide the lost water.

“The live slow die old strategy that used to work for plants in this environment no longer works as well. Increased climate stress in an already extreme environment is pushing them to their physiological thresholds,” Madsen-Hepp said. “Once these plants reach their limit, there is no solution. There’s just not much we can do to get them back.”said.

The team also found that, unlike more temperate ecosystems, the lower elevations of the desert are warming faster than the higher elevations. The shrubs and bushes that take over do not necessarily come from the highest points of the desert. They are also lower elevation plants that have generally expanded their range.

At about 29 meters per decade, the upward range changes are on par with the upper end of global rates of plant movement in response to climate warming. On average, plants in temperate regions have shown rates of range change between 5 and 30 meters per decade.

“We often think of the tundra as the indicator of climate change. Arctic and alpine ecosystems are very sensitive. We’re seeing here that this ecosystem is just as sensitive, if not more,” Spasojevic said. “And we already know the answer to alleviating stress. It’s very simple. Reduce fossil fuel emissions.”