Wednesday, July 08, 2026

How tall and short trees can coexist in old growth forests

Efficiency of light interception and use drive secondary forest succession

Kyoto University

Main image - forest — image:
A lush green forest, one of the study sites used in this study. While appearing peaceful at first glance, the forest is a fierce battleground for survival among trees.
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Credit: KyotoU / Yusuke Onoda

Kyoto, Japan -- Forests are shaped by light competition. The trees that grow the tallest have access to the most sunlight, blocking the rays and rendering the shaded space around them inhospitable to shorter trees below. In this stem exclusion phase of forest succession, the shorter trees often die. Yet scientists have observed that in old growth forests, trees of vastly different sizes successfully coexist, proving that reaching the top of the canopy is not the sole winning strategy for survival in a forest environment.

The height diversity of trees in mature forests indicates that light competition and species coexistence can balance out in forest succession. To understand how, quantifying light competition among trees is essential, but the complex architectural structures of natural forests and individual crowns have hindered rigorous scientific evaluation. A team of researchers from Kyoto University resolved to take on the challenge and solve this mystery.

"The competition for light among trees is frequently referred to as an evolutionary arms race, but trees of vastly different sizes successfully coexist in mature forests," says first author Yusuke Onoda. "We became interested in this paradox."

The team chose an approach with a novel framework analyzing a tree's relative growth rate, or the speed at which a tree grows relative to its size, separated into two key factors: light interception efficiency, which indicates how much sunlight a tree captures per unit of biomass, and light use efficiency, which describes how effectively a tree converts the intercepted sunlight into biomass. To test their framework in the wild, the scientists mapped the crown shapes and 3D light profiles of each tree within 12 different forest plots of varying ages in Japan, totaling more than 2,000 individual trees of 50 different species.

The results revealed a mechanistic explanation behind how light competition quantitatively drives secondary forest succession. In younger stands, or plots in a forest, taller trees have disproportionate advantages in light capture, forcing rapid height stratification. In older stands, however, the higher light use efficiency of shade-tolerant species enables them to thrive under tall canopies, promoting vertical species coexistence.

By uncovering the hidden mechanics of forest succession, this study offers a new perspective on how trees navigate light competition and establishes a new principle that explains how forests change across time and space. These insights have the potential to improve climate modeling and enable smarter forest management.

The team is applying their approach to other forest sites of different ages across various climate zones, including warm temperate and tropical forests. They hope this will validate and establish their framework as a general, universal principle on a global scale.

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The paper "Partitioning tree growth into light interception and use efficiencies clarifies the role of light competition in secondary forest succession" appeared on 8 July 2026 in the Journal of Ecology, with doi: 10.1111/1365-2745.70375

About Kyoto University

Kyoto University is one of Japan and Asia's premier research institutions, founded in 1897 and responsible for producing numerous Nobel laureates and winners of other prestigious international prizes. A broad curriculum across the arts and sciences at undergraduate and graduate levels complements several research centers, facilities, and offices around Japan and the world. For more information, please see: http://www.kyoto-u.ac.jp/en

By breaking down tree growth into light interception and use efficiencies, this study reveals how light competition drives secondary forest succession. In young stands, the superior light capture of taller trees dominates, forcing rapid height stratification. In older stands, higher light use efficiency of shade-tolerant species enables them to thrive under tall canopies, promoting vertical species coexistence.

Credit

KyotoU / Yusuke Onoda

Journal

Journal of Ecology

DOI

10.1111/1365-2745.70375

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Partitioning tree growth into light interception and use efficiencies clarifies the role of light competition in secondary forest succession

Article Publication Date

8-Jul-2026

Soil thickness controls landslide occurrence, study finds

University of Tsukuba

Tsukuba, Japan—Landslides triggered by heavy rainfall and earthquakes are becoming increasingly severe across Japan. However, accurately predicting their location and magnitude remains challenging. One obstacle is the difficulty of characterizing the shallow subsurface soil layers—directly involved in landslides. These layers are typically only tens of centimeters to a few meters thick. Advances in airborne laser surveying now make it possible to capture high-resolution topographic data before and after a disaster, allowing detailed analysis of landslide geometry. The team drew on these datasets to investigate the mechanisms that govern when and where landslides occur.

Working with pre- and post-event digital elevation models from catchments hit by past heavy-rainfall disasters, the researchers compared landslide area, depth, and slope gradient. They found that the widely assumed relationship between landslide area and depth holds only weakly, especially for shallow landslides, and that slope gradient exerts a much stronger control on depth. Notably, they found that the thickness of the failed soil layer falls within a relatively constrained range that varies systematically with slope gradient. Theoretical models such as the infinite slope stability framework, a standard tool for evaluating slope failure, have long predicted this pattern, but the study provides clear empirical confirmation across a large set of real disaster cases.

The findings suggest that the location and size of landslides can be estimated from relatively simple indicators, namely slope gradient and soil thickness. They also offer a foundation for hazard maps and risk assessments that account for the heavier rainfall expected under climate change. By making landslide assessments easier to apply in practice, the approach could strengthen disaster prevention and mitigation.

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This study was supported by JSPS KAKENHI (Grant Number JP20H03019-JP23H02246), the Environment Research and Technology Development Fund of the ERCA (JPMEERF20252004) funded by the Ministry of the Environment, and the Support for Pioneering Research Initiated by the Next Generation (SPRING) program funded by the Japan Science and Technology Agency.

Original Paper

Title of original paper:
Depth of rainfall induced landslides revealed by DEM of difference analysis using airborne LiDAR data in igneous terrains

Journal:
Scientific Reports

DOI:
10.1038/s41598-026-46714-4

Correspondence

Professor UCHIDA, Taro
Institute of Life and Environmental Sciences, University of Tsukuba

KUDO, Yuki
Doctoral Program in Environmental Studies, Degree Programs in Life and Earth Sciences, Graduate School of Science and Technology, University of Tsukuba

Atomic-level engineering of Cu nanoclusters improves conversion of carbon dioxide to fuel

The careful fine-tuning of copper nanoclusters can make a big difference in how chemical reactions proceed – improving our ability to turn carbon dioxide into something useful

Tohoku University

image:
Representation of the whole work with nanocluster structures and their CO₂ reduction capabilities. Hydrogen atoms are omitted for clarity.
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Credit: Yuichi Negishi et al.

A collaborative research team from Tohoku University and the Indian Institute of Technology Indore has made a significant breakthrough in carbon dioxide (CO₂) conversion. Their discovery offers a promising strategy for converting harmful CO₂ into valuable fuels and chemicals under mild conditions, advancing efforts toward sustainable carbon utilization and clean energy technologies. The findings were published in JACS Au on June 30, 2026.

Nanoclusters made of copper (Cu) - an inexpensive, naturally abundant material - have been gaining traction as promising aids of catalytic transformations. If developed correctly, these nanoclusters can improve the efficiency of a reaction called the electrochemical CO₂ reduction reaction. Doing so may bring us closer to developing better renewable energy storage and becoming a carbon neutral society.

One issue in this reaction is that formate - an unwanted byproduct - is conventionally produced. To suppress formate production, the research team modulated the Cu(I)/Cu(II) ratio in a Cu nanocluster. Instead of formate, the reaction now selectively produces the desired outcome: methanol (CH3OH). This greatly improves the efficiency of the reaction.

To achieve this boost in efficiency, the researchers needed to precisely engineer the structure of the nanocluster. The result was a structurally well-defined sulfide-templated Cu nanocluster, [S@Cu₅₀S₁₂(StBu)₂₀(CF₃COO)₁₂] (S@Cu₅₀) featuring a unique core-shell architecture composed of an inner S@Cu₁₄S₁₂ core surrounded by an outer Cu36(StBu)20 shell protected by thiolate ligands. This allowed for the controlled modulation of the Cu(I)/Cu(II) ratio, while preserving the overall geometric framework.

In addition, the team compared this nanocluster to a reported Cu₅₀S₁₂(StBu)₂₀(CF₃COO)₁₂] (Cu₅₀) nanocluster analogue, to directly investigate the influence of valence-state changes on catalytic performance.

Although both nanoclusters share very similar structural frameworks, the introduction of a sulfide ion at the center of the S@Cu₅₀ cluster led to subtle but crucial changes in its electronic properties. Altering the overall valence-state distribution of Cu and shifting the electronic structure significantly changed how reaction intermediates interacted with the catalyst surface, ultimately redirecting CO₂ conversion.

The researchers found that although both nanoclusters exhibited comparable overall catalytic activity, their product selectivity during CO₂ electroreduction differed remarkably. While Cu₅₀ predominantly produced formate (the undesired outcome) with a Faradaic efficiency of 38%, the newly developed nanocluster significantly suppressed formate formation to below 11% and instead enabled selective methanol production with a Faradaic efficiency of approximately 19% at −1.0 V versus RHE - a product completely absent in the Cu₅₀ system.

"This study provides the first clear evidence that precise modulation of the copper valence state in Cu nanoclusters can directly influence the selectivity of CO₂ reduction pathways," explains Professor Negishi (Tohoku University).

This breakthrough marks an important step toward designing next-generation catalysts, where atomic-level control can unlock cleaner and more efficient pathways for converting CO₂ into valuable fuels.

Detailed structural architecture of synthesized S@Cu₅₀ NC (a) Overall core-shell structural architecture (b) geometry of core and (c) geometry of shell. Hydrogen atoms are omitted for clarity.