Exotic Southern Hemisphere pines grow faster and withstand drought better

Exotic pines in the Southern Hemisphere appear to break a long-standing rule of plant ecology: they can grow rapidly while also tolerating drought. A new study found that these conifers grew faster and were more resilient during dry periods than related populations in the Northern Hemisphere.

Researchers examined 192 sites across the Americas, Europe, Africa and Oceania. They compared native and exotic populations by studying the width of annual growth rings, which closely reflects climate conditions. Exotic conifers reached growth rates up to four times higher than Northern Hemisphere populations.

The faster growth did not come with the expected loss of drought tolerance. Southern Hemisphere populations were less affected by water shortages and recovered more effectively after drought episodes. The team also found that trees growing outside their natural range had higher concentrations of nonstructural carbohydrates, or carbon reserves that help plants cope with water stress.

Carbon isotope signatures provided another clue. Exotic conifers in the Southern Hemisphere appeared better able to maintain photosynthesis during periods of drought. One possible explanation is that they face fewer natural enemies, allowing their growth and carbon balance to remain less disrupted.

The researchers cautioned against treating the findings as a general argument for planting exotic species to address the climate crisis. Some of the conifers studied are invasive in the Southern Hemisphere. Lodgepole pine, or Pinus contorta, has spread beyond plantations and threatens native ecosystems in Chile’s Aysén region.