scholarly journals Divergent historical GPP trends among state-of-the-art multi-model simulations and satellite-based products

2021 ◽  
Author(s):  
Ruqi Yang ◽  
Jun Wang ◽  
Ning Zeng ◽  
Stephen Sitch ◽  
Wenhan Tang ◽  
...  
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Spatial Correlation ◽  
Correlation Coefficients ◽  
Full Time ◽  
Co2 Fertilization ◽  
Fertilization Effect ◽  
Co2 Fertilization Effect ◽  
The Tropics ◽  
Global Carbon

Abstract. Understanding historical changes in gross primary productivity (GPP) is essential for better predicting the future global carbon cycle. However, the historical trends of terrestrial GPP, owing to the CO2 fertilization effect, climate, and land-use change, remain largely uncertain. Using long-term satellite-based near-infrared radiance of vegetation (NIRv), a proxy for GPP, and multiple GPP datasets derived from satellite-based products, Dynamic Global Vegetation Model (DGVM) simulations, and machine learning techniques, here we comprehensively investigated their trends and analyzed the causes for any discrepancies during 1982–2015. Although spatial patterns of climatological annual GPP from all products and NIRv are highly correlated (r  > 0.84), the spatial correlation coefficients of trends between DGVM GPP and NIRv significantly decreased (with the ensemble mean of r = 0.49) and even the spatial correlation coefficients of trends between other GPP products and NIRv became negative. By separating the global land into the tropics plus extra-tropical southern hemisphere (Trop+SH) and extra-tropical northern hemisphere (NH), we found that, during 1982–2015, simulated GPP from most of the models showed a stronger increasing trend over Trop+SH than NH. In contrast, the satellite-based GPP products indicated a substantial increase over NH. Mechanistically, model sensitivity experiments indicated that the increase of annual GPP was dominated by the CO2 fertilization effect (Global: 83.9 %), albeit a large uncertainty in magnitude among individual simulations. However, the spatial distribution of inter-model spreads of GPP trends resulted mainly from climate and land-use change rather than CO2 fertilization effect. Trends after 2000 were different from the full time-series, showing that satellite-based GPP products suggested weakened rising trends over NH and even significantly decreasing trends over Trop+SH, while the trends from DGVMs kept increasing. The inconsistencies are very likely caused by the contrasting performances between satellite-derived and DGVM simulated vegetation structure parameter (leaf area index, LAI). Therefore, the uncertainty in satellite-based GPP products induced by highly uncertain LAI data in the tropics undermines their roles in assessing the performance of DGVM simulations and understanding the changes of global carbon sinks.

The Local Biophysical Response to Land-Use Change in HadGEM2-ES

2019 ◽  
Vol 32 (22) ◽  
pp. 7611-7627 ◽  
Author(s):  
E. Robertson
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Latent Heat ◽  
Temperature Response ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Available Energy ◽  
Turbulent Heat Fluxes ◽  
The Tropics

Abstract The biophysical response to a local change in land use is calculated using the HadGEM2-ES Earth system model. The biophysical temperature response is found to be a small residual of three large opposing flux responses: available energy, sensible heat, and latent heat. Deforestation reduces available energy, which is balanced by a reduction in heat lost via turbulent fluxes. However, the changes in turbulent heat fluxes are not simply a response to the reduction in available energy; rather, they are a direct response to land-use change, caused by reduced roughness length and, in the tropics, an increase in the Bowen ratio. Evaluation against satellite-derived observational datasets shows that in response to deforestation, the model has too much albedo-driven cooling and too little latent-heat-driven warming, leading to a large cooling bias.

scholarly journals A theoretical framework for the net land-to-atmosphere CO<sub>2</sub> flux and its implications in the definition of "emissions from land-use change"

2013 ◽  
Vol 4 (1) ◽  
pp. 179-217 ◽  
Author(s):  
T. Gasser ◽  
P. Ciais
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Co2 Flux ◽  
Theoretical Framework ◽  
Elevated Atmospheric Co2 ◽  
Mathematical Expressions ◽  
Terrestrial Carbon Cycle ◽  
Definition Of ◽  
Mathematical Definitions ◽  
Global Carbon

Abstract. We develop a theoretical framework and analysis of the net land-to-atmosphere CO2 flux in order to discuss possible definitions of "emissions from land-use change". The terrestrial biosphere is affected by two perturbations: the perturbation of the global Carbon-Climate-Nitrogen system (CCN) with elevated atmospheric CO2, climate change and nitrogen deposition; and the Land-Use Change perturbation (LUC). Here, we progressively establish mathematical definitions of four generic components of the net land-to-atmosphere CO2 flux. The two first components are the fluxes that would be observed if only one perturbation occurred. The two other components are due to the coupling of the CCN and LUC perturbations, which shows the non-linear response of the terrestrial carbon cycle. Thanks to these four components, we introduce three possible definitions of "emissions from land-use change", that are indeed used in the scientific literature, often without clear distinctions, and we draw conclusions as for their absolute and relative behaviors. Thanks to the OSCAR v2 model, we provide quantitative estimates of the differences between the three definitions, and we find that comparing results from studies that do not use the same definition can lead to a bias of up to 20% between estimates of those emissions. After discussion of the limitations of the framework, we conclude on the three major points of this study that should help the community to reconcile modeling and observation of emissions from land-use change. The Appendix mainly provides more detailed mathematical expressions of the four components of the net land-to-atmosphere CO2 flux.

scholarly journals First evidence for an Amazonian insect migration in the butterfly Panacea prola (Lepidoptera: Nymphalidae)

2020 ◽  
Author(s):  
Geoffrey Gallice ◽  
Riccardo Mattea ◽  
Allison Stoiser
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Global Climate ◽  
Insect Species ◽  
Forest Loss ◽  
Environmental Cues ◽  
Mass Movements ◽  
Insect Migration ◽  
Nymphalid Butterfly ◽  
The Tropics

ABSTRACTInsect migrations rival those of vertebrates in terms of numbers of migrating individuals and even biomass, although instances of the former are comparatively poorly documented. This is especially true in the world’s tropics, which harbor the vast majority of Earth’s insect species. Understanding these mass movements is of critical and increasing importance as global climate and land use change accelerate and interact to alter the environmental cues that underlie migration, particularly in the tropics. Here, we provide the first evidence for an insect migration for the nymphalid butterfly Panacea prola in the Amazon, the world’s largest and most biodiverse rainforest that is experiencing a shifting climate and rapid forest loss.

scholarly journals Mediterranean irrigation under climate change: more efficient irrigation needed to compensate increases in irrigation water requirements

2015 ◽  
Vol 12 (8) ◽  
pp. 8459-8504 ◽  
Author(s):  
M. Fader ◽  
S. Shi ◽  
W. von Bloh ◽  
A. Bondeau ◽  
W. Cramer
Keyword(s):  
Climate Change ◽  
Irrigation Water ◽  
Mediterranean Region ◽  
Eastern Mediterranean ◽  
Water Requirements ◽  
Co2 Fertilization ◽  
Fertilization Effect ◽  
Co2 Fertilization Effect ◽  
The Mediterranean ◽  
Irrigation Requirements

Abstract. Irrigation in the Mediterranean is of vital importance for food security, employment and economic development. This study systematically assesses how climate change and increases in atmospheric CO2 concentrations may affect irrigation requirements in the Mediterranean region by 2080–2090. Future demographic change and technological improvements in irrigation systems are accounted for, as is the spread of climate forcing, warming levels and potential realization of the CO2-fertilization effect. Vegetation growth, phenology, agricultural production and irrigation water requirements and withdrawal were simulated with the process-based ecohydrological and agro-ecosystem model LPJmL after a large development that comprised the improved representation of Mediterranean crops. At present the Mediterranean region could save 35 % of water by implementing more efficient irrigation and conveyance systems. Some countries like Syria, Egypt and Turkey have higher saving potentials than others. Currently some crops, especially sugar cane and agricultural trees, consume in average more irrigation water per hectare than annual crops. Different crops show different magnitude of changes in net irrigation requirements due to climate change, being the increases most pronounced in agricultural trees. The Mediterranean area as a whole might face an increase in gross irrigation requirements between 4 and 18 % from climate change alone if irrigation systems and conveyance are not improved (2 °C global warming combined with full CO2-fertilization effect, and 5 °C global warming combined with no CO2-fertilization effect, respectively). Population growth increases these numbers to 22 and 74 %, respectively, affecting mainly the Southern and Eastern Mediterranean. However, improved irrigation technologies and conveyance systems have large water saving potentials, especially in the Eastern Mediterranean, and may be able to compensate to some degree the increases due to climate change and population growth. Both subregions would need around 35 % more water than today if they could afford some degree of modernization of irrigation and conveyance systems and benefit from the CO2-fertilization effect. Nevertheless, water scarcity might pose further challenges to the agricultural sector: Algeria, Libya, Israel, Jordan, Lebanon, Syria, Serbia, Morocco, Tunisia and Spain have a high risk of not being able to sustainably meet future irrigation water requirements in some scenarios. The results presented in this study point to the necessity of performing further research on climate-friendly agro-ecosystems in order to assess, on the one side, their degree of resilience to climate shocks, and on the other side, their adaptation potential when confronted with higher temperatures and changes in water availability.

scholarly journals Reviews and syntheses: Soil N<sub>2</sub>O and NO emissions from land use and land-use change in the tropics and subtropics: a meta-analysis

2015 ◽  
Vol 12 (23) ◽  
pp. 7299-7313 ◽  
Author(s):  
J. van Lent ◽  
K. Hergoualc'h ◽  
L. V. Verchot
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Nitrogen Availability ◽  
Meta Analysis ◽  
Forest Conversion ◽  
N2o Emissions ◽  
Emission Rates ◽  
Soil N ◽  
The Tropics ◽  
No Emissions

Abstract. Deforestation and forest degradation in the tropics may substantially alter soil N-oxide emissions. It is particularly relevant to accurately quantify those changes to properly account for them in a REDD+ climate change mitigation scheme that provides financial incentives to reduce the emissions. With this study we provide updated land use (LU)-based emission rates (104 studies, 392 N2O and 111 NO case studies), we determine the trend and magnitude of flux changes with land-use change (LUC) using a meta-analysis approach (44 studies, 135 N2O and 37 NO cases) and evaluate biophysical drivers of N2O and NO emissions and emission changes for the tropics. The average N2O and NO emissions in intact upland tropical forest amounted to 2.0 ± 0.2 (n = 90) and 1.7 ± 0.5 (n = 36) kg N ha−1 yr−1, respectively. In agricultural soils annual N2O emissions were exponentially related to N fertilization rates and average water-filled pore space (WFPS) whereas in non-agricultural sites a Gaussian response to WFPS fit better with the observed NO and N2O emissions. The sum of soil N2O and NO fluxes and the ratio of N2O to NO increased exponentially and significantly with increasing nitrogen availability (expressed as NO3− / [NO3−+NH4+]) and WFPS, respectively; following the conceptual Hole-In-the-Pipe model. Nitrous and nitric oxide fluxes did not increase significantly overall as a result of LUC (Hedges's d of 0.11 ± 0.11 and 0.16 ± 0.19, respectively), however individual LUC trajectories or practices did. Nitrous oxide fluxes increased significantly after intact upland forest conversion to croplands (Hedges's d = 0.78 ± 0.24) and NO increased significantly following the conversion of low forest cover (secondary forest younger than 30 years, woodlands, shrublands) (Hedges's d of 0.44 ± 0.13). Forest conversion to fertilized systems significantly and highly raised both N2O and NO emission rates (Hedges's d of 1.03 ± 0.23 and 0.52 ± 0.09, respectively). Changes in nitrogen availability and WFPS were the main factors explaining changes in N2O emissions following LUC, therefore it is important that experimental designs monitor their spatio-temporal variation. Gaps in the literature on N oxide fluxes included geographical gaps (Africa, Oceania) and LU gaps (degraded forest, wetland (notably peat) forest, oil palm plantation and soy cultivation).

scholarly journals Modelling the seasonal contribution of a CO2 fertilization effect of the terrestrial vegetation to the amplitude increase in atmospheric CO2 at Mauna Loa Observatory

Tellus B ◽  
1989 ◽  
Vol 41 (5) ◽  
pp. 487-510 ◽  
Author(s):  
Gundolf H. Kohlmaier ◽  
Ernst-Olof Siré ◽  
Alex Janecek ◽  
Charles D. Keeling ◽  
Stephen C. Piper ◽  
...  
Keyword(s):  
Atmospheric Co2 ◽  
Terrestrial Vegetation ◽  
Co2 Fertilization ◽  
Mauna Loa ◽  
Amplitude Increase ◽  
Fertilization Effect ◽  
Co2 Fertilization Effect

scholarly journals Identifying Land Use Change Trajectories in Brazil’s Agricultural Frontier

Land ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 506
Author(s):  
Adeline M. Maciel ◽  
Michelle C. A. Picoli ◽  
Lubia Vinhas ◽  
Gilberto Camara
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Agricultural Practices ◽  
Climate Mitigation ◽  
Change Trajectories ◽  
Mato Grosso ◽  
Double Cropping ◽  
Trajectories Of Change ◽  
The Tropics ◽  
Temporal Trajectory

Many of the world’s agricultural frontiers are located in the tropics. Crop and cattle expansion in these regions has a strong environmental impact. This paper examines land use and land cover transformations in Brazil, where large swaths of natural vegetation are being removed to make way for agricultural production. In Brazil, the land use dynamics are of great interest regarding the country’s sustainable development and climate mitigation actions, leading to the formulation and implantation of public policies and supply chain interventions to reduce deforestation. This paper uses temporal trajectory analysis to discuss the patterns of agricultural practices change in the different biomes of Mato Grosso State, one of Brazil’s agricultural frontiers. Taking yearly land use and cover classified images from 2001 to 2017, we identified, quantified, and spatialized areas of stability, intensification, reduction, interchange, and expansion of single and double cropping. The LUC Calculus was used as a tool to extract information about trajectories and trajectories of change. Over two decades, the land use change trajectories uncover the interplay between forest removal, cattle raising, grain production, and secondary vegetation regrowth. We observed a direct relationship between the conversion of forest areas to pasture and of pasture to agriculture areas in the Amazon portion of the Mato Grosso State in different periods. Our results enable a better understanding of trends in agricultural practices.

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