Seed production of over 700 tree species globally quantified and assessed by climate — ScienceDaily

The ability of a forest to regenerate after devastating fires, droughts or other disturbances depends largely on seed production. The results of two new studies by Duke University researchers could boost recovery and replanting after these disasters by providing foresters with new insights into which tree species produce more seeds and how their productivity can vary from place to place.

“Knowing which species produce more seeds and in which habitats helps us better understand how to manage seed trees and optimize forest regeneration, especially in seed-limited areas like much of the western United States. States,” said James S. Clark, Nicholas Distinguished Professor of Environmental Science at Duke, who was the corresponding author of both papers.

Clark and his colleagues published their peer-reviewed studies May 2 in Nature Communication and April 23 at Ecology Letters.

The studies come at a time of growing concern about the ability of many forests to recover from increasingly frequent and severe droughts and fires linked to climate change and increased harvesting to meet growing human demand for wood and other wood products.

On April 25, the Biden administration announced a new initiative in which the departments of agriculture and the interior will team up with states, tribes and the private sector to increase federal capacity for collecting cones and seeds. and seedling nursery, with the aim of expanding forest replanting programs. , especially in the western woodlands scorched by recent wildfires.

“Our findings, which are the first to establish global patterns of tree seed production and quantify the number of seeds produced by different species under different conditions, could be very useful for these types of management and renewal initiatives. of the world’s forests,” said Clark.

The studies synthesize seed production data for more than 700 species – from the tropics to the subarctic – and shed new light on how tree fecundity and seed supply contribute to forest regeneration and biodiversity in different climatic zones, he said. This knowledge is essential for understanding the evolution of forest species and how they respond to loss.

One of the most unexpected findings from these studies is that trees in the humid tropics collectively produce 250 times more seeds than those in dry boreal forests.

The fact that there are more tall trees in the humid tropics and that they produce, on average, 100 times more seeds than trees of the same size in boreal regions, may explain why species interactions are so intense in rainforests, Clark said.

Another key finding is that seed production is not limited by seed size. This dispels a popular assumption that species that produce larger seeds must produce proportionally less and therefore be more likely to lose.

“That’s not true,” Clark said. “While trees with larger seeds produce less than trees with small seeds, we have found that they still produce more than previously thought. When you multiply the number of seeds by the size of the seeds , you find that large-seeded species generate more reproductive output overall.”

A third intriguing finding is that gymnosperms, or conifers, have lower seed production than angiosperms, or flowering trees, possibly because gymnosperms expend a lot of energy making protective cones for their seeds. Knowing this can help guide the replanting and management of many western forests damaged by recent wildfires, Clark said.

It may also provide a clue to help solve Darwin’s famous “abominable mystery” as to why so many species of flowering plants evolved during the Cretaceous period, 145.5 million to 65.5 million ago. million years ago, when most other species (other than dinosaurs) lagged behind.

“This is the first time we have evidence that directly links seed production to species fitness,” Clark said. “It may be that high seed production was what made flowering plants sufficiently adept at thriving and evolving in the harsh conditions of the Cretaceous, just as they do today.”

Researchers from 70 institutions contributed to the Nature Communication paper. The main funding came from the National Science Foundation, the Belmont Forum, NASA and the French initiative Program d’Investissement d’Avenir (“Make Our Planet Great Again”).

Researchers from 67 institutions contributed to the Ecology Letters article. Its main funding came from the National Science Foundation, the Belmont Forum and the French initiative Program d’Investissement d’Avenir (“Make Our Planet Great Again”).

In addition to Clark’s senior faculty position at Duke’s Nicholas School, he holds a position at the Université Grenoble Alpes through the National Research Institute for Agriculture, Food and Agriculture. Environment.

Tong Qiu, Clark’s postdoctoral associate at the Nicholas School, is the lead author of the Nature Communication paper.