Linkage between SIF and GPP in a seasonally-dormant high-elevation subalpine forest
Abstract
Temperate and boreal conifer forests are dormant for many months during the cold season, during which they continue to absorb sunlight. As a result they exhibit seasonality in light-use efficiency (LUE) of photosynthesis, challenging our ability to monitor gross primary productivity (GPP) from remote sensing platforms. We have been studying the factors controlling the seasonality of photosynthesis of a high-elevation subalpine forest in Colorado (the Niwot Ridge AmeriFlux core site). Ongoing research includes examination of leaf-level chlorophyll fluorescence emission combined with measurement of canopy-level spectral reflectance and solar-induced fluorescence (SIF) at high spatio-temporal resolution using a custom tower-based PhotoSpec scanning spectrometer system. We found that GPP shutdown in winter was coincident with sustained leaf-scale non-photochemical quenching, caused by increased xanthophyll cycle pool size and conversion to facilitate thermal energy dissipation, leading to changes in LUE. There was no change in chlorophyll content across a full annual period, and minimal seasonal variation in absorbed sunlight or greenness. The relation between SIF and GPP was highly linear year-round at the daily, weekly, and monthly time scales, and the seasonal patterns of both were very similar. However, fluorescence in winter continued at both the leaf and canopy scales. The magnitude of canopy SIF in winter was 20% as large as summer peak, including when GPP was absent. These results highlight the utility of using SIF as a metric for GPP.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B31N2676B
- 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