Scientists transported coniferous trees across the ocean and replanted them, and obtained a result that did not fit conventional ecological ideas. In the new conditions, the same species grew up to four times faster and at the same time tolerated periods without water better.
A study published in the journal Nature covered 192 sites on four continents. More than twenty scientists from Chile, Argentina, Spain, the United States and New Zealand compared tree growth rings in their native places and in new territories. The sample included pines, larches and Douglas firs, widely used in forest plantings.
Analysis of the annual rings revealed an unexpected picture. In the Southern Hemisphere, northern conifers accumulated wood significantly faster than in their homeland. At the same time, their growth suffered less during droughts and recovered faster afterwards. Such a combination contradicts the classical idea of a trade-off between growth rate and resistance to stress.
Physiological measurements helped to understand the mechanism. In the new conditions, the trees contained more non-structural carbohydrates — sugars and starches that serve as an energy reserve. Isotopic carbon analysis indicated smaller limitations in gas exchange during photosynthesis. As a result, the plants assimilated carbon more efficiently and formed reserves.
Fast growth and drought resistance make such trees attractive for carbon dioxide sequestration projects. However, the same ability allows them to spread beyond plantings and colonize natural ecosystems. In Patagonia, Brazil and other regions, cases of the spread of introduced pines have already been recorded; they compete with local species and change conditions for fires.
The researchers note that native southern species, for example from the genus Nothofagus, also demonstrate a good combination of growth and drought tolerance. This opens up the possibility of using for forest restoration and climate projects species that are already adapted to local conditions and do not carry the risk of invasion.
The results emphasize how much more complex the real relationships between growth, resistance and environment are than previous models assumed.
