Observed water and light limitation across global ecosystems
<p>With a changing climate, it is becoming increasingly critical to understand vegetation responses to limiting environmental factors. Here, we investigate the spatial and temporal patterns of light and water limitation on photosynthesis using an observational framework. Our study is unique in...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-12-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/19/5575/2022/bg-19-5575-2022.pdf |
| Summary: | <p>With a changing climate, it is becoming increasingly critical to
understand vegetation responses to limiting environmental factors. Here, we
investigate the spatial and temporal patterns of light and water limitation
on photosynthesis using an observational framework. Our study is unique in
characterizing the nonlinear relationships between photosynthesis and water
and light, acknowledging approximately two regime behaviours (no limitation
and varying degrees of limitation). It is also unique in using an
observational framework instead of using model-derived photosynthesis
properties. We combine data from three different satellite sensors, i.e.,
sun-induced chlorophyll fluorescence (SIF) from the TROPOspheric Monitoring Instrument (TROPOMI), surface soil
moisture from the Soil Moisture Active Passive (SMAP) microwave radiometer, and vegetation greenness from the Moderate
Resolution Imaging Spectroradiometer (MODIS). We find both
single-regime and two-regime models describe SIF sensitivity to soil
moisture and photosynthetically active radiation (PAR) across the globe. The
distribution and strength of soil moisture limitation on SIF are mapped in
the water-limited environments, while the distribution and strength of PAR
limitations are mapped in the energy-limited environments. A two-regime
behaviour is detected in 73 % of the cases for water limitation on
photosynthesis, while two-regime detection is much lower at 41 % for light limitation on photosynthesis. SIF sensitivity to PAR strongly increases
along moisture gradients, reflecting mesic vegetation's adaptation to making
rapid usage of incoming light availability on the weekly timescales. The
transition point detected between the two regimes is connected to soil type
and mean annual precipitation for the SIF–soil moisture relationship and for
the SIF–PAR relationship. These thresholds therefore have an explicit
relation to properties of the landscape, although they may also be related
to finer details of the vegetation and soil interactions not resolved by the
spatial scales here. The simple functions and thresholds are emergent
behaviours capturing the interaction of many processes. The observational
thresholds and strength of coupling can be used as benchmark information for
Earth system models, especially those that characterize gross primary
production mechanisms and vegetation dynamics.</p> |
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| ISSN: | 1726-4170 1726-4189 |