For large and old trees, it is downhill in terms of reproduction
As people get older, their ability to reproduce decreases. But what about the tree? As they grow larger, will their ability to produce seeds, nuts, or fruits continue to grow? A new study of nearly 600 species worldwide has nipped this hypothesis in its infancy. In about 80% of the species examined, the fecundity of trees peaked or stabilized when they reached a medium size. After that, it refused. The other 20% may also experience a decline; the authors of the study said that there is not enough data to determine the older, larger trees of their species. The research is published On the 16th of August Proceedings of the National Academy of Sciences.
“Tree fruits and nuts make up 3% of the human diet and are also important for many birds and small mammals, and tree seeds are essential for forest regeneration,” said Tong Qiu, a postdoctoral researcher at Duke University who led the research. “In order to effectively manage and protect these resources, we need to know whether fertility will decline, and to what extent or age they may decline.”
Until now, answering these questions has forced ecologists to be helpless.
Co-author Maria Uriarte surveys trees in Puerto Rico. (Kevin Krajic/Earth Institute)
“On the one hand, given our understanding of the age-related degradation of humans and all other multicellular organisms, it is extremely incredible that the fecundity of trees increases indefinitely with age and size,” said James S. Clark, a professor of environmental sciences. At Duke. “On the other hand, strictly speaking, there is no conclusive evidence to refute.”
As yields begin to decline, many fruit tree crops are replaced every two to three years, and because it is difficult to monitor seed yields of non-cultivated trees, most studies on tree fecundity rely on data that favors young trees that still exist set. Small or medium-sized. Due to the lack of sufficient data on seed yields of many species in later years, scientists had to estimate these numbers based on average values from earlier stages. The problem is that regardless of size or age, trees do not necessarily produce a fixed number of seeds each year. Although the overall yield of a tree tends to be heavier in the early stages, there can be huge differences between each year and the tree, from zero seeds in one year to millions in the next year.
This new study avoids this trap by integrating the seed production and maturity status data of 585,670 individual trees of 597 species monitored by a network of long-term research sites involving dozens of institutions around the world. The network’s database contains detailed records of the annual seed production of trees grown in more than 500 different locations in North America, South America, Asia, Europe and Africa, usually dating back decades. Observations are usually obtained through seed traps or estimates of total seed yield based on the number of cones. Having access to such a large data repository allowed the team to develop a calibrated model to more accurately calculate long-term fecundity.
For example, a team led by research co-author Maria Uriarte of Columbia University’s Earth Institute has collected fruits and seeds from a Puerto Rican block every two weeks since 1992. Data from this site shows that trees reduce their investment in seed production as they age. “This information is critical to our ability to use models to accurately predict future forest composition and the ability of tree species to disperse into new environments in a changing climate,” Uriarte said.
“For most of the species we study, including humans, one of the most basic variables we measure is the birth rate,” Clark said. “For animals, this is usually easy—you count the number of eggs in the nest or the number of pups in a nest. But when you get to the tree, it’s even more tricky. You can’t directly observe how much is being produced. Seeds, and as this research shows, approximation does not work. You need another way to do this.”
59 researchers from 13 countries or regions (Chile, Italy, Canada, Poland, France, Spain, Switzerland, Japan, Slovenia, Germany, Panama, Puerto Rico, and the United States) co-authored the study. The main funding comes from the National Science Foundation, NASA and the French Ministère de’Enseignement Supérieur de la Recherche et de l’Innovation.
Adapted from a press release from Duke University.
