Wu, Shengbiao, Jing Wang, Zhengbing Yan, Guangqin Song, Yang Chen, Qin Ma, Meifeng Deng, et al. 2020. “Monitoring Tree-Crown Scale Autumn Leaf Phenology in a Temperate Forest With an Integration of PlanetScope and Drone Remote Sensing Observations”. ISPRS Journal of Photogrammetry and Remote Sensing 171: 36-48.
Publications
2020
Shan, Nan, Yongguang Zhang, Jing M Chen, Weimin Ju, Mirco Migliavacca, Josep Pe\~nuelas, Xi Yang, Zhaoying Zhang, Jacob A Nelson, and Yves Goulas. 2020. “A Model for Estimating Transpiration from Remotely Sensed Solar-Induced Chlorophyll Fluorescence”. Remote Sensing of Environment 252: 112134.
Carter, Kelsey R, Tana E Wood, Sasha C Reed, Elsa C Schwartz, Madeline B Reinsel, Xi Yang, and Molly A Cavaleri. 2020. “Photosynthetic and Respiratory Acclimation of Understory Shrubs in Response to in Situ Experimental Warming of a Wet Tropical Forest”. Frontiers in Forests and Global Change 3: 765-85.
Atkins, Jeff W, Atticus EL Stovall, and Xi Yang. 2020. “Mapping Temperate Forest Phenology Using Tower, UAV, and Ground-Based Sensors”. Drones 4 (3): 56.
Stovall, Atticus EL, Herman H Shugart, and Xi Yang. 2020. “Reply to ‘Height-Related Changes in Forest Composition Explain Increasing Tree Mortality With Height During an Extreme Drought’”. Nature Communications 11 (1): 1-4.
Shugart, HH, Adrianna Foster, Bin Wang, Dan Druckenbrod, Jianyong Ma, Manuel Lerdau, Sassan Saatchi, Xi Yang, and Xiaodong Yan. 2020. “Gap Models across Micro-to Mega-Scales of Time and Space: Examples of Tansley’s Ecosystem Concept”. Forest Ecosystems 7 (1): 1-18.
Miao, Guofang, Kaiyu Guan, Andrew E Suyker, Xi Yang, Timothy J Arkebauer, Elizabeth A Walter-Shea, Hyungsuk Kimm, et al. 2020. “Varying Contributions of Drivers to the Relationship Between Canopy Photosynthesis and Far-Red Sun-Induced Fluorescence for Two Maize Sites at Different Temporal Scales”. Journal of Geophysical Research: Biogeosciences.
2019
Swails, Erin, Yang, Asefi, Hergoualc’h, Louis Verchot, RE McRoberts, and Lawrence. 2019. “Linking Soil Respiration and Water Table Depth in Tropical Peatlands With Remotely Sensed Changes in Water Storage from the Gravity Recovery and Climate Experiment”. Mitigation and Adaptation Strategies for Global Change 24 (4): 575–590.
Stovall, Atticus, Herman Shugart, and Xi Yang. 2019. “Tree Height Explains Mortality Risk During an Intense Drought”. Nature Communications.
Forest mortality is accelerating due to climate change and the largest trees may be at the greatest risk, threatening critical ecological, economic, and social benefits. Here, we combine high-resolution airborne LiDAR and optical data to track tree-level mortality rates for ~2 million trees in California over 8 years, showing that tree height is the strongest predictor of mortality during extreme drought. Large trees die at twice the rate of small trees and environmental gradients of temperature, water, and competition control the intensity of the height-mortality relationship. These findings suggest that future persistent drought may cause widespread mortality of the largest trees on Earth.
Raczka, Porcar‐Castell, Magney, JE Lee, Köhler, Frankenberg, Grossmann, et al. 2019. “Sustained Nonphotochemical Quenching Shapes the Seasonal Pattern of SolarâInduced Fluorescence at a HighâElevation Evergreen Forest”. Journal of Geophysical Research: Biogeosciences 124 (7): 2005-20.
Traditional methods of carbon monitoring in mountainous regions are challenged by complex terrain. Recently, solar‐induced fluorescence (SIF) has been found to be an indicator of gross primary production (GPP), and the increased availability of remotely sensed SIF provides an opportunity to estimate GPP across the Western United States. Although the empirical linkage between SIF and GPP is strong, the current mechanistic understanding of this linkage is incomplete and depends upon changes in leaf biochemical processes in which absorbed sunlight leads to photochemistry, heat (via nonphotochemical quenching [NPQ]), fluorescence, or tissue damage. An improved mechanistic understanding is necessary to leverage SIF observations to improve representation of ecosystem processes within land surface models. Here we included an improved fluorescence model within the Community Land Model, Version 4.5 (CLM 4.5), to simulate seasonal changes in SIF at a subalpine forest in Colorado. We found that when the model accounted for sustained NPQ, this provided a larger seasonal change in fluorescence yield leading to simulated SIF that more closely resembled the observed seasonal pattern (Global Ozone Monitoring Experiment‐2 [GOME‐2] satellite platform and a tower‐mounted spectrometer system). We found that an acclimation model based on mean air temperature was a useful predictor for sustained NPQ. Although light intensity was not an important factor for this analysis, it should be considered before applying the sustained NPQ and SIF to other cold climate evergreen biomes. More leaf‐level fluorescence measurements are necessary to better understand the seasonal relationship between sustained and reversible components of NPQ and to what extent that influences SIF.