Plants can hide the effects of climate stress for years

Two out of every five plant species are currently at risk of extinction, and scientists are urgently trying to understand why some plants are more vulnerable to climate stress than others. In a new study from iDIV, researchers have found that climate drivers such as temperature and precipitation may have a stronger influence on plants outside of the growing season than what was previously expected. 

Previous studies that analyzed the relationship between climate and plant vital rates have reported only moderate effects. The results suggest that other threats, such as land use changes, are more of a threat to plant health than climate stress. These conclusions, however, may vary depending on the timing and duration of the research.

“Most researchers assume that plant populations respond to the climate within twelve months and only use this time window in their models to analyze plant responses,” said study first author Sanne Evers.

For the current investigation, the researchers analyzed 76 studies performed on 104 plant species that link climate drivers with demographic responses. 

The experts found that 85 percent of all studies accounted for just one year of plant vitals, often focusing solely on the growing season.  

“There are many ways in which climate during the dormant season, or climate that occurred few years in the past, can influence the survivorship, growth, and reproduction of plants. For example, species can grow substantially during the cold season, at least where the cold season temperature does not fall below 5° Celsius,” explained study senior author Aldo Compagnoni.

“In addition, it might take multiple years for plants to die after physiological damage from drought has occurred.”

The researchers set out to determine which combination of climate drivers and temporal window may optimize the ability to predict climate stress on plants. The team zeroed in on four exceptionally long-term data sets: the montane plants Helianthella quinquenervis and Frasera speciosa, and the arid plants Cylindropuntia imbricata and Cryptantha flava. 

“For these plant species, 15 to 47 years of data was available. And even though they are all perennials, they come from very different habitats with clearly marked seasons,” said Sanne Evers.

The study revealed that in many cases, it took several years for plants to respond to climate, and signs of the climate stress were not visible within the first couple of years. 

“Plant responses to climate drivers that are lagged and/or outside of the growing season are the rule rather than the exception,” said study co-author Professor Tiffany Knight. “This could be explained by the physiological features of some plants: For instance, in alpine environments, it may take up to four years until leaves and flowers of plants such as F. speciosa reach maturity.” 

As a result, the effects of an extreme climate event may only become visible in the number of leaves and flowers four years after that event influenced the formation of these structures.

The study reveals that plant responses to climate stress are more complex than what was previously thought, and the findings have important implications for understanding how plants will be affected by future climate change. 

“Our study suggests that considering climatic predictors that fall outside of the most recent growing season will improve our understanding of how climate affects population dynamics,” wrote the researchers.

The study is published in the journal Global Change Biology.

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By Chrissy Sexton, Earth.com Staff Writer