A new study published in the journal Nature reveals that conifers planted outside their native range in the Southern Hemisphere not only grow up to four times faster than those in the Northern Hemisphere, but also show greater resistance and resilience to drought. The finding challenges one of the most deeply rooted ideas in plant ecology: that plants that grow rapidly generally have a lower capacity to tolerate water stress.
The research was led by Dr. Alex Fajardo, researcher at the Institute of Ecology and Biodiversity (IEB) and professor at the University of Talca, together with Dr. Frida I. Piper (IEB, University of Talca) and Dr. Claudia Reyes-Bahamonde (LiLi Millennium Nucleus, University of Talca), with the collaboration of a network of researchers from 10 countries.
To study how these exotic species respond to environmental conditions outside their natural range, the team analyzed the growth rings of nine conifer species from the Pinaceae family, all native to the Northern Hemisphere. These included radiata pine, ponderosa pine, lodgepole pine and Scots pine.
The researchers analyzed 192 sites distributed across the Americas, Europe, Africa and Oceania, including Chile. In Chile, the researchers conducted sampling in the central part of the country, particularly in the Maule and Ñuble regions, and in the southern part of the country, around Coyhaique. Meanwhile, collaborators in the United States, Canada and Europe conducted sampling in natural populations of the same pine species. At these sites, increment cores were extracted from the trees to determine annual growth-ring widths, which are closely related to climate. In the Southern Hemisphere, particularly in Chile, Argentina and New Zealand, increment cores were also extracted from trees of Nothofagus species growing adjacent to pine plantations.
Challenging ecological theory and natural enemies
The overall results showed a marked difference. Exotic conifers reached growth rates up to four times higher than those of populations in the Northern Hemisphere. But the most striking finding was that this accelerated growth was not accompanied by lower drought tolerance, as would be expected.
On the contrary, populations in the Southern Hemisphere showed greater resistance and resilience during dry periods. This means that their growth was less affected during droughts and that they had a greater capacity to recover after these events.
“What is interesting is that we are seeing a combination that, according to what we would expect based on ecological theory, should not occur: trees that grow much faster while, at the same time, being able to better withstand and recover from drought,” explains Alex Fajardo.
The team also found differences in the functioning of these trees that help explain this behavior. Conifers growing outside their native range had higher concentrations of carbon reserves. Carbon reserves, also known as non-structural carbohydrates, play essential roles in plants and have been associated with a greater capacity to cope with periods of water stress. The researchers also found that the carbon isotope signature in exotic conifers growing in the Southern Hemisphere was related to a greater capacity to maintain photosynthesis under water-stress conditions.
According to Fajardo, one possible reason for this advantage of exotic conifers growing in the Southern Hemisphere is related to the absence of natural enemies. In their original distribution ranges in the Northern Hemisphere, conifers coexist with a diversity of living organisms that can affect their growth and carbon balance. “The most likely explanation for this pattern is that exotic conifers escape their natural enemies, which are present or more abundant in their native range. These include specialized herbivores, pathogens and competing species,” highlights the IEB scientist, a center of excellence funded by Chile’s National Agency for Research and Development (ANID).
This situation could be particularly relevant in the Southern Hemisphere, where there are no native pine species. “The resources that plants in their native range must allocate to defending themselves against natural enemies could, in an exotic range, become available for other functions, such as growth and better coping with water stress,” the researcher adds.
The case of Chile and native forests
In this study, the researchers were also able to observe what happens with native species growing adjacent to plantations in the Southern Hemisphere. In Chile, the team analyzed secondary Nothofagus forests located near pine plantations. The species studied included raulí ( Nothofagus alpina ), coihue ( N. dombeyi ), roble ( N. obliqua ) and lenga ( N. pumilio ), at sites in the Maule and Ñuble regions and around Coyhaique.
“In both areas, samples were collected from both exotic pines and native Nothofagus growing very close to the pine plantations,” says the lead author and IEB researcher.
The results showed that Nothofagus occupied an intermediate position in terms of growth. They grew faster than pines in their native ranges in the Northern Hemisphere, but more slowly than the pine plantations. In terms of their response to drought, however, they showed a similar tolerance to that observed in the exotic conifers.
For Fajardo, this finding opens up a relevant possibility for forest management and carbon sequestration. “A more sustainable solution for increasing carbon sequestration, different from planting exotic conifer species, could be to maintain and increase these native secondary forests. Although Nothofagus grow more slowly than pines, they show similar levels of drought tolerance and have higher wood density, which means more carbon is sequestered per unit of volume,” he says.
The findings are particularly relevant in a climate change scenario marked by increasingly frequent and intense droughts, which may provide new perspectives for forest management and for assessing their capacity to store carbon.
The authors caution that these results do not mean that afforestation with exotic species is a general solution to the climate crisis, since their introduction can also generate impacts on the biodiversity of native ecosystems.
In fact, some of the conifers studied are invasive species in the Southern Hemisphere. This is the case of lodgepole pine ( Pinus contorta ), whose expansion beyond plantations is a conservation concern for native ecosystems in Chile’s Aysén Region. This situation raises a new question based on the study’s findings: could the same characteristics that allow these species to thrive outside their native range also contribute to their success as invasive species?
The researcher emphasizes that the invasive nature of certain pine species was not the focus of this study, and therefore this relationship will need to be evaluated in future research. However, he does emphasize its importance.
“The fact that these exotic species—some of which are invasive—can grow well while also tolerating drought is a trait that could be added to the list of characteristics that make invasive plants successful,” Fajardo concludes.
Nature
Observational study
Not applicable
Pines grow faster and are more drought-resilient in the Southern Hemisphere
2-Sep-2026