Improving ecosystem productivity modeling through spatially explicit estimation of optimal light use efficiency

Madani, Nima; Kimball, J. S.; Affleck, David L. R.; Kattge, Jens; Graham, Jonathan M.; Bodegom, Peter M. van; Reich, Peter B.; Running, Steven W.

doi:10.1002/2014jg002709

Cited by 77 publications

(74 citation statements)

References 123 publications

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“…In this study, the optimized values were 1.839 g C MJ −1 , 1.831 g C MJ −1 , and 0.672 g C MJ −1 for forests, crops, and grass, respectively, which were in the range of 0.796–2.53 g C MJ −1 , 1.056–3.864 g C MJ −1 , and 0.199–1.8818 g C MJ −1 for forests, cropland, and grassland, respectively [ J. Chen et al ., ; Zhang et al ., ]. However, ɛ max was found to be spatially heterogeneous within biome types [ B. Chen et al ., ; Madani et al ., ]. But the observed GPP in cropland was available only from one site in this study and the optimized parameter was applied to regional scale, which would be the main reason of the overestimated NPP.…”

Section: Discussionmentioning

confidence: 99%

Decreasing net primary production due to drought and slight decreases in solar radiation in China from 2000 to 2012

Wang

Dong

et al. 2017

JGR Biogeosciences

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Terrestrial ecosystems have continued to provide the critical service of slowing the atmospheric CO2 growth rate. Terrestrial net primary productivity (NPP) is thought to be a major contributing factor to this trend. Yet our ability to estimate NPP at the regional scale remains limited due to large uncertainties in the response of NPP to multiple interacting climate factors and uncertainties in the driver data sets needed to estimate NPP. In this study, we introduced an improved NPP algorithm that used local driver data sets and parameters in China. We found that bias decreased by 30% for gross primary production (GPP) and 17% for NPP compared with the widely used global GPP and NPP products, respectively. From 2000 to 2012, a pixel‐level analysis of our improved NPP for the region of China showed an overall decreasing NPP trend of 4.65 Tg C a−1. Reductions in NPP were largest for the southern forests of China (−5.38 Tg C a−1), whereas minor increases in NPP were found for North China (0.65 Tg C a−1). Surprisingly, reductions in NPP were largely due to decreases in solar radiation (82%), rather than the more commonly expected effects of drought (18%). This was because for southern China, the interannual variability of NPP was more sensitive to solar radiation (R2 in 0.29–0.59) relative to precipitation (R2 < 0.13). These findings update our previous knowledge of carbon uptake responses to climate change in terrestrial ecosystems of China and highlight the importance of shortwave radiation in driving vegetation productivity for the region, especially for tropical forests.

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Section: Discussionmentioning

confidence: 99%

Decreasing net primary production due to drought and slight decreases in solar radiation in China from 2000 to 2012

Wang

Dong

et al. 2017

JGR Biogeosciences

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“…This LUE‐based GPP approach provides the foundation of the current MODIS GPP product (Running et al ., ). Increasing numbers of eddy‐covariance flux towers have provided valuable information to calibrate this LUE‐based GPP model, particularly the value of LUE GPP and how it varies under environmental stresses (Turner et al ., ; Hilker et al ., ; Coops et al ., ; Madani et al ., ).…”

Section: Methodsmentioning

confidence: 99%

Improving the monitoring of crop productivity using spaceborne solar‐induced fluorescence

Guan

Berry

Zhang

et al. 2015

Global Change Biology

271

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Large-scale monitoring of crop growth and yield has important value for forecasting food production and prices and ensuring regional food security. A newly emerging satellite retrieval, solar-induced fluorescence (SIF) of chlorophyll, provides for the first time a direct measurement related to plant photosynthetic activity (i.e. electron transport rate). Here, we provide a framework to link SIF retrievals and crop yield, accounting for stoichiometry, photosynthetic pathways, and respiration losses. We apply this framework to estimate United States crop productivity for 2007-2012, where we use the spaceborne SIF retrievals from the Global Ozone Monitoring Experiment-2 satellite, benchmarked with county-level crop yield statistics, and compare it with various traditional crop monitoring approaches. We find that a SIF-based approach accounting for photosynthetic pathways (i.e. C3 and C4 crops) provides the best measure of crop productivity among these approaches, despite the fact that SIF sensors are not yet optimized for terrestrial applications. We further show that SIF provides the ability to infer the impacts of environmental stresses on autotrophic respiration and carbon-use-efficiency, with a substantial sensitivity of both to high temperatures. These results indicate new opportunities for improved mechanistic understanding of crop yield responses to climate variability and change.

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“…These changes, integrated across leaves within a forest canopy, would likely result in different post-disturbance biotic and Table 1. abiotic dynamics; FASET has already shown the assumption of a fixed LUE not to be true at the stand level . Recent work has also shown that the use of a spatially variable LUE parameterization, using C flux measurements from the Fluxnet data set, can significantly improve the accuracy of modeled GPP (Madani et al, 2014). Maintenance of canopy light absorption in the FASET forest depends on a structurally heterogeneous canopy so that subdominant trees quickly increase their absorption following the girdling of canopy dominants .…”

Section: Model Mechanisms and Behaviorsmentioning

confidence: 99%

Moderate forest disturbance as a stringent test for gap and big-leaf models

et al. 2015

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Abstract. Disturbance-induced tree mortality is a key factor regulating the carbon balance of a forest, but tree mortality and its subsequent effects are poorly represented processes in terrestrial ecosystem models. It is thus unclear whether models can robustly simulate moderate (non-catastrophic) disturbances, which tend to increase biological and structural complexity and are increasingly common in aging US forests. We tested whether three forest ecosystem models -Biome-BGC (BioGeochemical Cycles), a classic big-leaf model, and the ZELIG and ED (Ecosystem Demography) gap-oriented models -could reproduce the resilience to moderate disturbance observed in an experimentally manipulated forest (the Forest Accelerated Succession Experiment in northern Michigan, USA, in which 38 % of canopy dominants were stem girdled and compared to control plots). Each model was parameterized, spun up, and disturbed following similar protocols and run for 5 years post-disturbance. The models replicated observed declines in aboveground biomass well. Biome-BGC captured the timing and rebound of observed leaf area index (LAI), while ZELIG and ED correctly estimated the magnitude of LAI decline. None of the models fully captured the observed post-disturbance C fluxes, in particular gross primary production or net primary production (NPP). Biome-BGC NPP was correctly resilient but for the wrong reasons, and could not match the absolute observational values. ZELIG and ED, in contrast, exhibited large, unobserved drops in NPP and net ecosystem production. The biological mechanisms proposed to explain the observed rapid resilience of the C cycle are typically not incorporated by these or other models. It is thus an open question whether most ecosystem models will simulate correctly the gradual and less extensive tree mortality characteristic of moderate disturbances.

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Improving ecosystem productivity modeling through spatially explicit estimation of optimal light use efficiency

Cited by 77 publications

References 123 publications

Decreasing net primary production due to drought and slight decreases in solar radiation in China from 2000 to 2012

Decreasing net primary production due to drought and slight decreases in solar radiation in China from 2000 to 2012

Improving the monitoring of crop productivity using spaceborne solar‐induced fluorescence

Moderate forest disturbance as a stringent test for gap and big-leaf models

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