22 April 2024

In canopy soils there is an undiscovered biodiversity


A Japanese study highlights the variety of invertebrate species found in canopy soils, the soils created through the transformation of organic matter on branches

by Matteo Cavallito


Canopy soils are home to an astonishing biodiversity which is still largely unknown. A phenomenon that is spurring new research efforts aiming to shed light on a peculiar ecosystem within the forest ecosystem. These include the recent investigation by scholars at the University of Tsukuba, Japan, whose findings have been published in the journal Biological Conservation.

The canopy ecosystem

The study examined a very special environment whose importance is often underestimated. These ecosystems form on plant branches where organic matter accumulates. Over time the organic matter transforms to create a kind of soil. The phenomenon is particularly evident in the longest-lived forests including, researchers recall, the Yaku-sugi forests, the thousand-year-old cedars of Yakushima Island.

Here, an ecosystem “formed by the accumulation and decomposition of leaves at the junctions of branches and trunks in the old-growth cedar forests” is located on tree crowns, a statement from the Japanese university explains.

Such an ecosystem, the authors note, hosts “a taxonomic composition of animals that significantly differs from that of the ground soils.” The study allowed the researchers to verify this hypothesis by overcoming the technical difficulties of this kind of investigation. “Canopy ecosystems provide a wide range of ecosystem services, but because they are difficult to access, knowledge about their conservation is limited,” the research explains.

The study

A team of researchers thus traveled to Yakushima to collect samples of tree soils for genetic investigation. Since the 17th century, the scholars recall, many trees on the island have been cut down. Today, as a result, a large population of plants that have regenerated over the past 300 years sit alongside the surviving thousand-year-old specimens. The study examined four regenerated trees and five surviving trees.

The researchers used DNA metabarcoding, a technique that allowed them to identify “the taxonomic composition of invertebrates in canopy and ground soil samples.” In total, “invertebrates in 33 orders and 183 families were detected.”

Moreover, “Invertebrate taxonomic richness identified from the canopy soil of retained trees was similar to that from ground soil, but taxonomic composition differed markedly,” the research states. “Canopy soil of retained trees was deeper and more developed than that of regenerated trees, and held a higher number of taxonomic groups per soil sample area.”

Conserving old-growth forests and their biodiversity

The implications are obvious. In regenerated plants, not even three centuries of time have served to fully restore the original species diversity. This is definitely significant in a global context characterized by the progressive reduction of old-growth forests where large trees are present. The study, the authors point out, thus highlights the biodiversity value of such forests from a new perspective.

“Our findings confirm that protected areas with old trees that exclude human disturbances are important for conservation of biodiversity in canopy ecosystems,” the researchers say. “We also recommend elongation of harvest cycles and a tree retention approach in forestry areas to minimize the impact of logging disturbance.”