Climate factors outside the growing season may have stronger impacts on plants than previously assumed.
Two out of every five plant species in the world are at risk of extinction. In the face of climate change, understanding why some plant species are facing extinction while others reign is more urgent than ever. Previous studies linking bioclimatic rates with vegetation have found relatively modest effects, sometimes leading to the conclusion that other threats, such as land use change, may still be more important than climate factors. However, these conclusions can result from erroneous assumptions about the times of the year (ie a “time window”) climatic factors such as temperature and precipitation that affect plant species. “Most researchers assume that plant populations respond to climate within twelve months and only use this time window in their models to analyze plant responses,” says first author Sanne Evers of iDiv and MLU.
The climatic conditions are often overlooked during the seasons of idle
For their study, the team of researchers led by iDiv, MLU and UFZ analyzed 76 studies of 104 plant species that link climatic factors to demographic responses. They found that 85% of all studies considered one-year time windows, often focusing on the growing season (such as spring and / or summer). However: “There are many ways in which the climate during the inactivity season, or the climate that occurred in a few years in the past, can affect the survival, growth and reproduction of plants. For example, species can grow significantly during the cold season, at least.” When the cold season does not drop below 5 ° C. In addition, it may take years for plants to die after the physiological damage caused by drought, “says Aldo Compagnione of iDiv and MLU and the lead author of the paper.
To explore which combination of climatic factors and the time window with the best predictive power, the researchers used four exceptionally long-term data sets: the mountain plants Helianthella quinquenervis, Frasera speciosa, and the arid plants Cylindropuntia imbricata and Cryptantha flava. For this plant species, data were available from 15 to 47 years old. And although they are all perennials, they come from completely different habitats with clearly defined seasons, ”San Evers explains.
Climate stress may only become visible years later
The results are clear: in many cases, it can take several years for plants to respond to the climate. “Plant responses to late climatic and / or off-season drivers are the rule, not the exception,” says co-author Tiffany Knight, professor at MLU and UFZ and chair of the iDiv research group. “This can be explained by the physiological features of some plants: for example, in alpine environments, it may take up to four years for the leaves and flowers of plants such as F. speciosa to reach maturity.” Accordingly, the effects of a severe climate event may only appear in the number of leaves and flowers four years after this event affected the formation of these structures.
While this study focuses on studying the effects of past climate on plants, there are important implications for understanding how plants will be affected by climate change in the future. This study highlights that plant responses to climate are more complex than previously estimated. We need to prioritize experiences and observations of terrestrial ecosystems in order to create robust scenarios for the plant species that are critical to human well-being.
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