Mirrors on the Forest Floor Increase the Growth of Shaded Seedlings by 175%

Indoor plant enthusiasts are familiar with using mirrors to direct sunlight onto plants. Now, scientists have adapted this idea to help endangered tree seedlings struggling to grow in shaded forests. The Serianthes nelsonii, a large tree native to Guam and Rota, is one of the rarest plants in the world, with only one mature tree left on Guam and just 121 on Rota.

The International Union for Conservation of Nature classifies S. nelsonii as “critically endangered,” prompting various efforts to prevent its extinction. Despite hundreds of seedlings sprouting each year under the Guam tree, most perish within a month due to lack of sunlight. While seedlings grown under artificial lights in nurseries have thrived, they struggle to survive once transplanted into the forest.

Using Mirrors to Boost Seedling Growth in Shaded Forests

What’s truly needed is a way to provide more light to seedlings grown in the forest. Installing artificial lighting isn’t feasible, so Thomas Marler and his team at the University of Guam turned to mirrors for a solution. They drew inspiration from the plastic mulch often used in commercial agriculture.

While “mulch” typically conjures images of shredded materials, plastic mulch refers to plastic sheeting laid over soil, allowing crop plants to grow through holes while blocking sunlight to prevent weeds and retain moisture.

Some growers use brightly colored plastic to reflect sunlight onto plants, enhancing their growth. Although highly reflective silver or aluminum foil mulch has been studied, its high cost limits its use on large fields.

However, cost is less of a concern when growing a few hundred seedlings. With this in mind, Marler’s team opted for actual mirrors instead of foil mulch. They created small mosaics made of hexagonal mirrors arranged in a ring with an open center.

Mirror Mosaics Boost Growth in Shaded Seedlings

These mosaics were placed around Serianthes seedlings in a cloth-shaded nursery in Guam and on a shaded forest floor in the Philippines. Half of the plants had mirrors exposed to sunlight, while the other half were covered with leaf litter as a control.

The results showed that the unblocked mirrors reflected over 70% of incoming sunlight to the plants. Those benefited by mirrors grew up to 175% taller and had a 161% higher survival rate compared to the controls.

The researchers concluded that using reflective surfaces below plants could be a cost-effective way to enhance survival rates in conservation nurseries, increasing the chances of successful recruitment in natural habitats. This finding was published in the journal Agronomy.

Read the original artlce on: New Atlas

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