Biology subjects

Handa, I. T.

Publications and source records attributed to Handa, I. T..

4 recordsLinked to original sources

bioRxiv2026

Montreal Urban Observatory: research platform to monitor urban forest ecosystems for global change adaptation and health

As urban populations grow, cities are increasingly seen not only as drivers of climate change but also as critical arenas for implementing mitigation and adaptation strategies. Urban forests and green infrastructure play a vital role in shaping environmental quality and human health, yet access to these benefits remains inequitable. The Montreal Urban Observatory was designed to investigate the complex relationships among biodiversity, ecosystem functioning, and human health. Twenty-five permanent plots were established across the Island of Montreal, strategically located along gradients in vegetation cover, population density, and mean household income. Interdisciplinary research within the Observatory focuses on themes including urban forest structure and function, abiotic conditions, biodiversity, ecological interactions, natures contributions to people, related human health outcomes, and developing novel methodological approaches. The Observatory supports long-term, cross-scale monitoring and fosters collaborative research on urban social-ecological systems, thus contributing to global initiatives to enhance urban sustainability and equity through nature-based solutions. Early results confirm the relevance of the main gradients for several organisms and response variables, from microbes to trees and abiotic factors. For example, sampling all trees, public and private, within a radius of 200m centered on each plot revealed significant differences in the diversity and structure of private and public trees, including an overwhelming dominance of Thuya occidentalis not captured in commonly used public tree inventories.

ecology↗

bioRxiv2024

Tree diversity increases carbon stocks and fluxes above- but not belowground in a tropical forest experiment

International commitments advocate large-scale forest restoration as a nature-based solution to climate change mitigation through carbon (C) sequestration. Mounting evidence suggests that mixed compared to monospecific planted forests may sequester more C, exhibit lower susceptibility to climate extremes and offer a broader range of ecosystem services. However, experimental studies comprehensively examining the control of tree diversity on multiple C stocks and fluxes above- and belowground are lacking. To address this gap, we leverage data from the Sardinilla experiment in Panama, the oldest tropical tree diversity experiment which features a gradient of one-, two-, three- and five-species mixtures of native tree species. Over 16 years, we measured multiple above- and belowground C stocks and fluxes, ranging from tree aboveground C, over leaf litter C production, to soil organic carbon (SOC). We show that tree diversity significantly increased aboveground C stocks and fluxes, with a 57% higher gain in aboveground tree C in five-species mixtures compared to monocultures (35.7{+/-}1.8 vs 22.8{+/-}3.4 Mg C ha-1) 16 years after planting. In contrast, we observed a net reduction in SOC (on average -11.2{+/-}1.1 Mg C ha-1) and no significant difference in SOC3 stocks (the predominantly tree-derived, i.e., C3 plant-derived SOC fraction) between five-species mixtures and monocultures (13.0{+/-}0.9 vs 15.1{+/-}1.3 Mg C ha-1). Positive tree diversity effects persisted despite repeated climate extremes and strengthened over time for aboveground tree growth. Structural equation models showed that higher tree growth in mixtures enhanced leaf litter and coarse woody debris C fluxes to the soil, resulting in a tightly linked C cycle aboveground. However, we did not observe significant links between above- and belowground C stocks and fluxes. Our study elucidates the mechanisms through which higher tree diversity bolsters the climate mitigation potential of tropical forest restoration. Restoration schemes should prioritize mixed over monospecific planted forests.

ecology↗

bioRxiv2022

Globally invariant metabolism but density-diversity mismatch in springtails

Soil life supports the functioning and biodiversity of terrestrial ecosystems1, 2. Springtails (Collembola) are among the most abundant soil animals regulating soil fertility and flow of energy through above- and belowground food webs3-5. However, the global distribution of springtail diversity and density, and how these relate to energy fluxes remains unknown. Here, using a global dataset collected from 2,470 sites, we estimate total soil springtail biomass at 29 Mt carbon (threefold higher than wild terrestrial vertebrates6) and record peak densities up to 2 million individuals per m{superscript 2} in the Arctic. Despite a 20-fold biomass difference between tundra and the tropics, springtail energy use (community metabolism) remains similar across the latitudinal gradient, owing to the increase in temperature. Neither springtail density nor community metabolism were predicted by local species richness, which was highest in the tropics, but comparably high in some temperate forests and even tundra. Changes in springtail activity may emerge from latitudinal gradients in temperature, predation7, 8, and resource limitation7, 9, 10 in soil communities. Contrasting temperature responses of biomass, diversity and activity of springtail communities suggest that climate warming will alter fundamental soil biodiversity metrics in different directions, potentially restructuring terrestrial food webs and affecting major soil functions.

ecology↗

bioRxiv2021

Non-structural carbohydrate concentrations in woody organs, but not leaves, of temperate and tropical tree angiosperms are independent of the "fast-slow" plant economic spectrum

Background and AimsCarbohydrate reserves play a vital role in plant survival during periods of negative carbon balance. Considering active storage of reserves, there is a trade-off between carbon allocation to growth and to reserves and defense. A resulting hypothesis is that allocation to reserves exhibits a coordinated variation with functional traits associated with the fast-slow plant economics spectrum. MethodsWe tested the relationship between non-structural carbohydrates (NSC) of tree organs and functional traits using 61 angiosperm tree species from temperate and tropical forests with phylogenetic hierarchical Bayesian models. Key ResultsOur results provide evidence that NSC concentrations in woody organs and plant functional traits are largely decoupled, meaning that species resilience is unrelated to their position on the fast-slow plant economics spectrum. In contrast, we found that variation between NSC concentrations in leaves and the fast-slow continuum was coordinated, as species with higher leaf NSC had traits values associated with resource conservative species such as lower SLA, lower Amax, and high wood density. We did not detect an influence of leaf habit on the variation of NSC concentrations in tree organs. ConclusionsEfforts to predict the response of ecosystems to global change will need to integrate a suite of plant traits, such as NSC concentrations in woody organs, that are independent of the fast-slow spectrum and that capture how species respond to a broad range of global change factors.

plant biology↗