Can Pinyon Pines Survive Climate Change?
A new study led by an 黑料吃瓜 biologist finds this critically important pine tree struggles to reproduce at higher temperatures.
Pinyon pines are an indispensable part of the American Southwest. Many Native American tribes relied upon the sustenance provided by their pine nuts鈥攁 harvest crop that remains economically important today. Woodland creatures depend upon the trees for shelter and as a food source.鈥淭hey are a very important part of the ecosystem. They are a foundation species.鈥�
So it鈥檚 critical for ecologists to understand how these trees will cope with warmer, drier conditions under climate change, according to 黑料吃瓜 evolutionary ecologist Lluvia Flores-Renter铆a. Findings from her recent studies suggest higher temperatures can interrupt the trees鈥� reproduction, which could reduce their numbers and even lead to localized extinctions in particularly warm areas.
These trees are no strangers to tough environments. They have adapted to thrive in lower-elevation, semi-arid conditions where other pines don鈥檛 grow. As a result, they form enormous open woodlands across drier, lower regions mostly in Arizona, Colorado, New Mexico and Utah. It鈥檚 the dominant pine in Colorado, making up 22 percent of the state鈥檚 forests.
鈥淭hey are a very important part of the ecosystem,鈥� said Flores-Renter铆a. 鈥淭hey are a foundation species.鈥�
Pinyon pines are relatively slow growers. They reach maturity after about 20 years, but don鈥檛 produce female cones until they are some 40 years old. That slow life cycle means the trees can鈥檛 bounce back from die-offs due to drought or wildfire as quickly as some other species. As drier, warmer conditions are expected in the Southwest in the coming years, Flores-Renter铆a and colleagues from Northern Arizona University conducted experiments to learn how these trees might respond to climate change.
They collected pollen from 24 pinyon pines growing at elevations between 1,700 and 2,000 meters in Northern Arizona. Back at the lab, they grew the pollen in petri dishes at one of three temperatures: 30, 35 or 40 degrees Celsius (86, 95 or 104 degrees Fahrenheit). Then they observed the pollen to see if it would germinate, a critical step in plant reproduction in which pollen extend a tube which transmits genetic material to a flower or cone.
Regardless of the elevation, higher temperatures decreased the pollen鈥檚 viability dramatically. In some cases, trees鈥� pollen became totally unviable. These effects were more pronounced in pollen collected from lower and higher elevations, and less pronounced at middle elevations.
That suggests these pines may be unable to reproduce if temperatures rise even modestly. The researchers in the journal Frontiers in Plant Science.
鈥淔our or five degrees may not sound like a big deal to humans, but it can be a really big deal for plants,鈥� Flores-Renter铆a said. 鈥淎nd that kind of temperature increase is about what we expect to see in the future. Over the next 80 years or so, it鈥檚 possible that for trees experiencing heat waves during reproduction, the pollen simply won鈥檛 be able to germinate.鈥�
According to some climate change models, that could mean the localized extinction of pinyon pines in certain areas. Yet Flores-Renter铆a鈥檚 other recent work offers a glimmer of optimism. A study she co-authored last year in Proceedings of the National Academy of Sciences found that certain varieties of pinyon pines have specific types of fungus that grow with them, and these fungi might .
Whether these drought-protective fungi might help lower-elevation pinyon pines to keep reproducing under warmer, drier conditions remains unknown, but their relationship underscores the importance of learning more about the complex biology at work in this critical species, Flores-Renter铆a said.
鈥淯ltimately, we鈥檙e still learning what will be the fate of these trees under climate change.鈥�
