Spatial inhomogeneity of SIF in natural and agricultural canopies and its impact on the interpretation of spatially averaged ground observations
Abstract
Spatially averaged Solar-Induced Chlorophyll Fluorescence (SIF) observations are increasingly used in the study of the carbon cycle in various environments. Leaf-level chlorophyll fluorescence measurements have shown the dependence of photosynthesis on the radiative environment at the leaf-scale. To bridge the gap between leaf-level and canopy average SIF observations we developed and deployed our new PhotoSpec instrument to measure red and far-red SIF and canopy reflectance at different field sites. A two-dimensional scanner with a narrow field-of-view (0.7°) telescope allows the observation of the long-term spatial distribution of SIF and various vegetation indices (VI) in complex canopies. PhotoSpec also includes a PAR sensor operated at 1-second time resolution to quantify the variation of solar radiation during the canopy observations.
Here we present the spatial scanning strategies and resulting distributions of SIF and various VIs (NDVI, EVI, PRI) at four different field sites: the tropical rain forest of Costa Rica; soy-bean and corn fields in Iowa, U.S.; and the subalpine forest at Niwot Ridge, Colorado, U.S. We discuss strategies to classify the radiative environment in the canopy from individual PhotoSpec reflectance observations, i.e. direct vs diffuse solar irradiance, sun vs. shade, etc. The statistical analysis of this data and its relation to SIF and VIs provides unique information on the contribution of different canopy locations to an overall spatial average of SIF and VI in a canopy. In addition, the classification of SIF yield by the radiative conditions at the leaf-scale gives insight into the variability of photosynthesis in complex canopies.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B34C..02S
- Keywords:
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- 0315 Biosphere/atmosphere interactions;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0480 Remote sensing;
- BIOGEOSCIENCESDE: 1631 Land/atmosphere interactions;
- GLOBAL CHANGE