Publications

2025

Dashti, Hamid, Min Chen, Dalei Hao, and Xi Yang. (2025) 2025. “Canopy Structure Exhibits Linear and Nonlinear Links to Biome-Level Maximum Light Use Efficiency.”. Ecology Letters 28 (6): e70142. https://doi.org/10.1111/ele.70142.

Maximum light use efficiency (εmax) represents a plant's capacity to convert light into carbon during photosynthesis. Although prior studies have explored εmax variations between sunlit and shaded leaves or its temporal ties to canopy structure, the spatial relationship between biome-level εmax (εbiome) and biome structure remains poorly understood. We analysed data from 320 eddy covariance sites ( 855 site-years) with satellite-derived near-infrared reflectance of vegetation (NIRv) and leaf area index (LAI). We introduced NIRvN (NIRv/LAI) to isolate architectural effects from leaf quantity. Site-level εmax was calculated and aggregated by biome to derive εbiome. Results show εbiome rises nonlinearly with NIRv and LAI, saturating at high LAI, with crops and tropical evergreen forests deviating from this trend. Conversely, εbiome decreases linearly with increasing NIRvN, indicating that biomes with greater NIR scattering efficiency exhibit lower εbiome. These results enhance understanding of structural influences on carbon uptake across global biomes.

Pierrat, Zoe Amie, Troy S Magney, Will P Richardson, Benjamin R K Runkle, Jen L Diehl, Xi Yang, William Woodgate, et al. (2025) 2025. “Proximal Remote Sensing: An Essential Tool for Bridging the Gap Between High-Resolution Ecosystem Monitoring and Global Ecology.”. The New Phytologist. https://doi.org/10.1111/nph.20405.

A new proliferation of optical instruments that can be attached to towers over or within ecosystems, or 'proximal' remote sensing, enables a comprehensive characterization of terrestrial ecosystem structure, function, and fluxes of energy, water, and carbon. Proximal remote sensing can bridge the gap between individual plants, site-level eddy-covariance fluxes, and airborne and spaceborne remote sensing by providing continuous data at a high-spatiotemporal resolution. Here, we review recent advances in proximal remote sensing for improving our mechanistic understanding of plant and ecosystem processes, model development, and validation of current and upcoming satellite missions. We provide current best practices for data availability and metadata for proximal remote sensing: spectral reflectance, solar-induced fluorescence, thermal infrared radiation, microwave backscatter, and LiDAR. Our paper outlines the steps necessary for making these data streams more widespread, accessible, interoperable, and information-rich, enabling us to address key ecological questions unanswerable from space-based observations alone and, ultimately, to demonstrate the feasibility of these technologies to address critical questions in local and global ecology.

2024

2023

Yang, Xi, Rong Li, Andrew Jablonski, Atticus Stovall, Jongmin Kim, Koong Yi, Yixin Ma, et al. 2023. “Leaf Angle As a Leaf and Canopy Trait: Rejuvenating Its Role in Ecology With New Technology”. Ecology Letters 26 (6): 1005-20. https://doi.org/https://doi.org/10.1111/ele.14215.
Abstract Life on Earth depends on the conversion of solar energy to chemical energy by plants through photosynthesis. A fundamental challenge in optimizing photosynthesis is to adjust leaf angles to efficiently use the intercepted sunlight under the constraints of heat stress, water loss and competition. Despite the importance of leaf angle, until recently, we have lacked data and frameworks to describe and predict leaf angle dynamics and their impacts on leaves to the globe. We review the role of leaf angle in studies of ecophysiology, ecosystem ecology and earth system science, and highlight the essential yet understudied role of leaf angle as an ecological strategy to regulate plant carbon–water–energy nexus and to bridge leaf, canopy and earth system processes. Using two models, we show that leaf angle variations have significant impacts on not only canopy-scale photosynthesis, energy balance and water use efficiency but also light competition within the forest canopy. New techniques to measure leaf angles are emerging, opening opportunities to understand the rarely-measured intraspecific, interspecific, seasonal and interannual variations of leaf angles and their implications to plant biology and earth system science. We conclude by proposing three directions for future research.