An American botanist in the Mariana Islands has invented a way to save a dying population of bean trees. Their offspring die in the shade of the forest canopy a few weeks after germination. The researcher conducted an experiment by placing mirrors around the young trees and leaving them for several months. The seedlings treated in this way were taller and survived three times more often.

In the west of the sea there is a group of small islands called the Marianas. The archipelago stretches in an arc along the Mariana Trench, divided into 16 sections to the south and north.

A rare bean tree grows on the lands of the two northernmost islands, Rota and Guam. Serianthes nelsoniiThe number does not exceed hundreds, according to the International Union for Conservation of Nature in 2017. The plant is also protected by the US Endangered Species Act.

But administrative procedures do not address the real problem that prevents the tree from recovering. The fact is that during some research conducted in Guam, botanists found under the adult trunks S. nelsonii hundreds of trees appear every year. But they die within a month. The same thing happened in the nurseries: young legumes died steadily for years while experts tried to grow them.

Everything was complicated by a special reaction to light: seeds S. nelsonii worse germination in full sunlight, and on the contrary, shading increased the growth of trees. In real bush conditions there may be a lack of light under the forest canopy.

University of Guam botanist Thomas Marler decided to help S. nelsoniias well as other trees that disappeared with the help of mirrors placed around the young trunks. The results of the research were published in the journal Agricultural Science.

Marler planted seeds of three species of legumes (S. nelsonii, S. grandiflora, S. kanehirae) in Guam in April 2015. When the ladder emerged, he selected the healthiest individuals, 4.5-5.5 centimeters tall. The botanist placed a mosaic of hexagonal mirrors, 7.5 centimeters in diameter, under 48 selected seedlings, 16 for each species. In the control group, these mirrors were covered with litter to block reflected light. Over the next 11 weeks, the plants were watered regularly and their development was monitored.

A similar experiment was conducted in the Philippines in December 2023 and was only grown. S. grandifloraThirty-two plants were divided into four groups, each with one seedling, around which identical hexagonal mirrors were placed. In the others, the substrate consisted of mulch. The experiment lasted 26 weeks, until June 21.

Many plants treated with only mulch and two seedlings under which mirrors were placed died. The height of the “mirror” legumes was 41% higher than the surviving plants without similar litter. The diameter of their stems also increased – 60% larger than that of ordinary trees on the ground. Mirrors probably also improved leaf growth, because such seedlings had more leaves.

In experiments lasting 26 weeks in the Philippines, seedlings treated with mirrors in litter managed to grow up to 30 centimeters in height, which the researchers say makes them less vulnerable. During this time, seedlings with mulched beds remained weak and died more often. The lifespan of treated trees tripled.

Overall, all three species responded positively to the mirror litter: they received 170% more reflected light than other trees during the experiment. This approach could help restore endangered legume populations that are unable to grow in the dark under the forest canopy.