Even in the desert, plants feel the heat of global warming
By Monica Konija, National Science Foundation
livescience.com – Sat Apr 3, 9:02 am ET Global warming is a hot topic, and it’s causing concern for scientists studying winter annuals in the Sonoran Desert. While desert winters have become warmer and drier over the years, climate changes have pushed the arrival of winter rains later in the year, forcing winter-annual plants like the curvenut combseed (Pectocarya recurvata) to emerge later when temperatures are colder. In 1982, Larry Venable, an ecologist at the University of Arizona (UA) in Tucson, began a study at The Desert Laboratory on nearby Tumamoc Hill in order to investigate adaptive “bet-hedging” in plants. Bet-hedging is an adaptive response by seeds that allows them to delay germination. The delay lets the plant attempt survival by avoiding harsh environmental periods. The germination delay can be caused by insufficient rainfall, lack of nutrients, inappropriate temperatures or any adverse condition that would affect the survival of a seed. The seeds can remain dormant for extended periods if the environment is unfavorable for germination and survival. “No one had bothered to study real desert annuals to see what happens, and here I was, suddenly working as a plant ecologist in the middle of the desert,” Venable said. “The theory involved plants that hedge against year-to-year variation in reproductive success, so I thought I’d set up some field plots and measure it.” The later arrival of Sonoran desert winter rains pushes the germination of the winter annuals later into the year and has affected the types of winter annuals that dominate the location. Researchers measure carbon and nitrogen in the plants’ leaves to learn how well the various species grow at winter’s lower temperatures. … The winter annuals are not the only vegetation affected by the climate shift occurring in the Sonoran desert. The increasingly drier climate has caused a decrease in dominant desert shrubbery as well. The lack of water available to the shrubs has caused them decrease in size so they can more efficiently utilize the amount of water that’s available. If the later arrival of winter rains continues, the germination of the winter annuals will subsequently occur later in the year, and the plant community will continuously change and favor plants that thrive in colder environments.
