Research

The Environmental Ecology Laboratory conducts research on forests in the tropical and temperate regions, mainly on the following themes.

  • Fundamental Ecology: How do diverse organisms coexist within forest ecosystems?

  • Applied Ecology: How can forest use and biodiversity conservation be effectively balanced?

To address these questions, we employ a multidisciplinary approach that integrates field surveys, drone-based remote sensing, DNA analysis, data science, and theoretical modeling.

Research keywords

Biodiversity, Ecosystem services, Tropical forests, Species diversity maintenance mechanisms, Forest renewal, Seed dispersal, Pollen dispersal, Sustainable Forest management, , Deciduous broad-leaved forests, Climate change, APBON

Main Research Topics

Mechanisms underlying the maintainance of tropical forest biodiversity 

The tropical rain forests in Southeast Asia are among the highest biodiversity on Earth. How can so many species coexist in a single forest?
We are investigating this question by combining tree species diversity data collected in the field, aerial drone observations, and theoretical models of ecology.
For example, in a study using drones to analyze the spatial structure of forests (Takeuchi et al. 2023), it was found that trees in the upper canopy layer of the forest (the tree layer) retain a large amount of biomass (stored carbon), but it is dominated by a small number of tree species. On the other hand,  the understory and forest floor layers harbor a much greater diversity of species, forming the core of the forest’s species richness. This vertical stratification—where different plant species occupy different forest layers and play distinct ecological roles—enables high levels of biodiversity to persist within limited space. In essence, the structural complexity of vertical forest layers is a key mechanism promoting species coexistence.

Biological diversity in the tropical forest

We are also conducting basic ecological research on rare plants that are unique to the tropical forests of Southeast Asia. These include Nepenthes, an insectivorous pitcher plant, and Rafflesia, known for producing some of the largest flowers in the world.

The phenomenon general flowering and fruiting

In the lowland tropical forests of Southeast Asia, a phenomenon called "general flowering" is known in which multiple species of trees simultaneously flower and set fruit at irregular intervals every few to several years or decades. Why it exists only in this region, what triggers flowering, and why general flowering has evolved are still mysterious.
To address these questions, we are investigating the seed and pollen dispersal patterns and their ecological roles in Dipterocarpaceae, a dominant tree family that plays a central role in general flowering events.

Impact of forest fragmentation on biodiversity

As development advances, forest fragmentation has become a serious threat to tropical forest ecosystems. Fragmentation alters habitats, disrupts species interactions, and destabilizes ecological balances.
Our research focuses on how this forest fragmentation affects plant reproduction and generation. Previous research has shown that self-pollination and mating with nearby parent trees in dipterocarp trees have detrimental effects (inbreeding depression), such as smaller seeds and the appearance of "albino" individuals with no chlorophyll in their leaves. These studies have raised concerns about the long-term effects of forest fragmentation, as the transport of pollen and seeds over long distances (long-distance dispersal) is essential for the maintenance of tree populations.

Biodiversity and conservation value of community reserved forests in Borneo

Indigenous communities in Borneo have preserved forests called "community reserved forests" or community forests in their communities. We conduct research focusing on both the biodiversity of these forests and their significance as resources for local communities.

Surveys in community reserved forests have shown that these forests are genetically rich and have as many tree and mammal species as the old-growth forests. For local communities, community reserved forests are also a source of water, building materials, food, and other resources. In particular, a climbing plant called rattan has been used as a material for baskets and mats. Villagers have the knowledge (traditional knowledge) to distinguish between different types of rattan and their characteristics, and use them for different purposes. For example, multiple types of rattan are used for a single basket, and basket weaving that makes use of the differences in materials can be seen.

Sustainable forest use in Sarawak

In Sarawak, Malaysia, a large portion of the forest is designated as production forest for timber harvesting. A key challenge is finding a balance between sustainable forest management and biodiversity conservation.

In collaboration with the Forest Department Sarawak, we are developing methodologies to monitor and evaluate forest volume following logging activities. Our research aims to quantitatively assess both forest volume and biodiversity by integrating advanced technologies—such as drone-based aerial surveys, satellite-based large-scale monitoring, and DNA analysis for tree species identification. These efforts support the development of science-based approaches for sustainable forest use that maintain ecological integrity.

Climate change impact for forests in Japan

In recent years, the effects of global warming and climate change have become increasingly evident in forests across Japan. Using long-term ecological monitoring data—such as those from JaLTER and the Survey of Specified Plant Communities—we analyze how forest composition and structure are changing over time.

Our findings reveal trends such as an increase in evergreen tree species and a decline in deciduous species in certain regions, as well as a retreat of cold-adapted species and the expansion of species typically found in warmer climates.

These studies provide critical scientific insights to support adaptive forest management and biodiversity conservation strategies, especially as climate change impacts are expected to intensify in the coming decades.

Biodiversity observation and conservation network linking Japan, Asia and the world

We are actively engaged in the Asia-Pacific Biodiversity Observation Network (APBON), an international initiative that brings together researchers and policymakers to advance biodiversity monitoring and conservation across the region.

As a platform linking science and policy, APBON promotes collaboration among experts from Japan and other Asia-Pacific countries. Our activities focus on:

  • Sharing biodiversity issues and challenges across diverse countries and regions, and building cooperative frameworks based on shared knowledge and experiences
  • Exploring mechanisms for implementing effective biodiversity observation and conservation tailored to national contexts
  • Building capacity for biodiversity monitoring through training, data sharing, and international dialogue

Through these efforts, we aim to connect local and regional achievements to global goals and promote international cooperation toward a more sustainable future.