scholarly journals Evaluation of modeled global carbon dynamics: analysis based on global carbon flux and above-ground biomass data

2016 ◽  
Author(s):  
Bao-Lin Xue ◽  
Qinghua Guo ◽  
Tianyu Hu ◽  
Yongcai Wang ◽  
Shengli Tao ◽  
...  
Keyword(s):  
Spatial Patterns ◽  
Carbon Flux ◽  
Large Scale ◽  
Gross Primary Production ◽  
Carbon Dynamics ◽  
Global Scale ◽  
Above Ground Biomass ◽  
Carbon Cycles ◽  
Ground Biomass ◽  
Global Carbon

Abstract. Dynamic global vegetation models are useful tools for the simulation of carbon dynamics on regional and global scales. However, even the most validated models are usually hampered by the poor availability of global biomass data in the model validation, especially on regional/global scales. Here, taking the integrated biosphere simulator model (IBIS) as an example, we evaluated the modeled carbon dynamics, including gross primary production (GPP) and potential above-ground biomass (AGB), on the global scale. The IBIS model was constrained by both in situ GPP and plot-level AGB data collected from the literature. Independent validation showed that IBIS could reproduce GPP and evapotranspiration with acceptable accuracy at site and global levels. On the global scale, the IBIS-simulated total AGB was similar to those obtained in other studies. However, discrepancies were observed between the model-derived and observed spatial patterns of AGB for Amazonian forests. The differences among the AGB spatial patterns were mainly caused by the single-parameter set of the model used. This study showed that different meteorological inputs can also introduce substantial differences in AGB on the global scale. Further analysis showed that this difference is small compared with parameter-induced differences. The conclusions of our research highlight the necessity of considering the heterogeneity of key model physiological parameters in modeling global AGB. The research also shows that to simulate large-scale carbon dynamics, both carbon flux and AGB data are necessary to constrain the model. The main conclusions of our research will help to improve model simulations of global carbon cycles.

scholarly journals Evaluation of the Sensitivity of SMOS L-VOD to Forest Above-Ground Biomass at Global Scale

2020 ◽  
Vol 12 (9) ◽  
pp. 1450
Author(s):  
Arnaud Mialon ◽  
Nemesio J. Rodríguez-Fernández ◽  
Maurizio Santoro ◽  
Sassan Saatchi ◽  
Stéphane Mermoz ◽  
...  
Keyword(s):  
Large Scale ◽  
Correlation Coefficients ◽  
Global Scale ◽  
Above Ground Biomass ◽  
Ground Biomass ◽  
Northern Latitudes ◽  
Ocean Salinity ◽  
Good Proxy ◽  
Using Data ◽  
The Tropics

The present study evaluates the L band Vegetation Optical Depth (L-VOD) derived from the Soil Moisture and Ocean Salinity (SMOS) satellite to monitor Above Ground Biomass (AGB) at a global scale. Although SMOS L-VOD has been shown to be a good proxy for AGB in Africa and Tropics, little is known about this relationship at large scale. In this study, we further examine this relationship at a global scale using the latest AGB maps from Saatchi et al. and GlobBiomass computed using data acquired during the SMOS period. We show that at a global scale the L-VOD from SMOS is well-correlated with the AGB estimates from Saatchi et al. and GlobBiomass with the Pearson’s correlation coefficients (R) of 0.91 and 0.94 respectively. Although AGB estimates in Africa and the Tropics are well-captured by SMOS L-VOD (R > 0.9), the relationship is less straightforward for the dense forests over the northern latitudes (R = 0.32 and 0.69 with Saatchi et al. and GlobBiomass respectively). This paper gives strong evidence in support of the sensitivity of SMOS L-VOD to AGB estimates at a globale scale, providing an interesting alternative and complement to exisiting sensors for monitoring biomass evolution. These findings can further facilitate research on biomass now that SMOS is providing more than 10 years of data.

scholarly journals Spatial Structure of Above-Ground Biomass Limits Accuracy of Carbon Mapping in Rainforest but Large Scale Forest Inventories Can Help to Overcome

PLoS ONE ◽  
2015 ◽  
Vol 10 (9) ◽  
pp. e0138456 ◽  
Author(s):  
Stéphane Guitet ◽  
Bruno Hérault ◽  
Quentin Molto ◽  
Olivier Brunaux ◽  
Pierre Couteron
Keyword(s):  
Spatial Structure ◽  
Large Scale ◽  
Above Ground Biomass ◽  
Ground Biomass ◽  
Forest Inventories ◽  
Carbon Mapping

scholarly journals The importance of micrometeorological variations for photosynthesis and transpiration in a boreal coniferous forest

2014 ◽  
Vol 11 (8) ◽  
pp. 12441-12485
Author(s):  
G. Schurgers ◽  
F. Lagergren ◽  
M. Mölder ◽  
A. Lindroth
Keyword(s):  
Large Scale ◽  
Gross Primary Production ◽  
Coniferous Forest ◽  
Co2 Concentration ◽  
Early Morning ◽  
Global Scale ◽  
Canopy Exchange ◽  
Exchange Processes ◽  
Vertical Heterogeneity ◽  
Stable Conditions

Abstract. Plant canopies affect the canopy micrometeorology, and thereby alter canopy exchange processes. For the simulation of these exchange processes on a regional or global scale, large-scale vegetation models often assume homogeneous environmental conditions within the canopy. In this study, we address the importance of vertical variations in light, temperature, CO2 concentration and humidity within the canopy for photosynthesis and transpiration of a boreal coniferous forest in central Sweden. A leaf-level photosynthesis-stomatal conductance model was used for aggregating these processes to canopy level while applying the within-canopy distributions of these driving variables. The simulation model showed good agreement with eddy covariance-derived gross primary production (GPP) estimates on daily and annual timescales, and showed a reasonable agreement between transpiration and observed H2O fluxes, where discrepancies are largely attributable to a lack of forest floor evaporation in the model. Simulations in which vertical heterogeneity was artificially suppressed revealed that the vertical distribution of light is the driver of vertical heterogeneity. Despite large differences between above-canopy and within canopy humidity, and despite large gradients in CO2 concentration during early morning hours after nights with stable conditions, neither humidity nor CO2 played an important role for vertical heterogeneity of photosynthesis and transpiration.

scholarly journals Experimental warming does not enhance gross primary production and above-ground biomass in the alpine meadow of Tibet

2013 ◽  
Vol 7 (1) ◽  
pp. 073505 ◽  
Author(s):  
Gang Fu ◽  
Xianzhou Zhang ◽  
Yangjian Zhang ◽  
Peili Shi ◽  
Yunlong Li ◽  
...  
Keyword(s):  
Primary Production ◽  
Alpine Meadow ◽  
Gross Primary Production ◽  
Experimental Warming ◽  
Above Ground Biomass ◽  
Ground Biomass

scholarly journals Global variability of belowground autotrophic respiration in terrestrial ecosystems

2019 ◽  
Author(s):  
Xiaolu Tang ◽  
Shaohui Fan ◽  
Wenjie Zhang ◽  
Sicong Gao ◽  
Guo Chen ◽  
...  
Keyword(s):  
Climate Change ◽  
Carbon Flux ◽  
Terrestrial Ecosystems ◽  
Global Scale ◽  
Future Climate ◽  
Future Climate Change ◽  
Autotrophic Respiration ◽  
Climate Zones ◽  
Global Land ◽  
Global Carbon

Abstract. Belowground autotrophic respiration (RA) is one of the largest, but highly uncertain carbon flux components in terrestrial ecosystems. It has not been explored globally before and still acted as a “black box” in global carbon cycling. Such progress and uncertainty motivate a development of global RA dataset and understand its spatial and temporal pattern, causes and responses to future climate change. This study used Random Forest to study RA's spatial and temporal pattern at the global scale by linking the updated field observations from Global Soil Respiration Database (v4) with global grid temperature, precipitation and other environmental variables. Globally, mean RA was 43.8 ± 0.4 Pg C a−1 with a temporally increasing trend of 0.025 ± 0.006 Pg C a−1 over 1980–2012. Such increment trend was widely spread with 58 % global land areas. For each 1 °C increase in annual mean temperature, global RA increased by 0.85 ± 0.13 Pg C a−1, and it was 0.17 ± 0.03 Pg C a−1 for 10 mm increase in annual mean precipitation, indicating a positive feedback of RA to future climate change. At a global scale, precipitation was the main dominant climatic drivers of the spatial pattern of RA, accounting for 56 % of global land areas with widely spread globally, particularly in dry or semi-arid areas, followed by shortwave radiation (25 %) and temperature (19 %). Different temporal patterns for varying climate zones and biomes indicated uneven response of RA to future climate change, challenging the perspective that the parameters of global carbon stimulation independent on climate zones and biomes. The developed RA database, the missing carbon flux component that is not constrained and validated in terrestrial ecosystem models and earth system models, will provide insights into understanding mechanisms underlying the spatial and temporal variability of belowground carbon dynamics. RA database also has great potentials to serve as a benchmark for future data-model comparisons. The RA product is freely available at https://doi.org/10.6084/m9.figshare.7636193.

scholarly journals The Role of Time-Series L-Band SAR and GEDI in Mapping Sub-Tropical Above-Ground Biomass

2021 ◽  
Vol 9 ◽  
Author(s):  
Unmesh Khati ◽  
Marco Lavalle ◽  
Gulab Singh
Keyword(s):  
Time Series ◽  
Soil Moisture ◽  
Field Data ◽  
Large Scale ◽  
Test Site ◽  
Above Ground Biomass ◽  
Retrieval Accuracy ◽  
Ground Biomass ◽  
L Band ◽  
Field Plots

Physics-based algorithms estimating large-scale forest above-ground biomass (AGB) from synthetic aperture radar (SAR) data generally use airborne laser scanning (ALS) or grid of national forest inventory (NFI) to reduce uncertainties in the model calibration. This study assesses the potential of multitemporal L-band ALOS-2/PALSAR-2 data to improve forest AGB estimation using the three-parameter water cloud model (WCM) trained with field data from relatively small (0.1 ha) plots. The major objective is to assess the impact of the high uncertainties in field inventory data due to relatively smaller plot size and temporal gap between acquisitions and ground truth on the AGB estimation. This study analyzes a time series of twenty-three ALOS-2 dual-polarized images spanning 5 years acquired under different weather and soil moisture conditions over a subtropical forest test site in India. The WCM model is trained and validated on individual acquisitions to retrieve forest AGB. The accuracy of the generated AGB products is quantified using the root mean square error (RMSE). Further, we use a multitemporal AGB retrieval approach to improve the accuracy of the estimated AGB. Changes in precipitation and soil moisture affect the AGB retrieval accuracy from individual acquisitions; however, using multitemporal data, these effects are mitigated. Using a multitemporal AGB retrieval strategy, the accuracy improves by 15% (55 Mg/ha RMSE) for all field plots and by 21% (39 Mg/ha RMSE) for forests with AGB less than 100 Mg/ha. The analysis shows that any ten multitemporal acquisitions spanning 5 years are sufficient for improving AGB retrieval accuracy over the considered test site. Furthermore, we use allometry from colocated field plots and Global Ecosystem Dynamics Investigation (GEDI) L2A height metrics to produce GEDI-derived AGB estimates. Despite the limited co-location of GEDI and field data over our study area, within the period of interest, the preliminary analysis shows the potential of jointly using the GEDI-derived AGB and multi-temporal ALOS-2 data for large-scale AGB retrieval.

scholarly journals The importance of micrometeorological variations for photosynthesis and transpiration in a boreal coniferous forest

2015 ◽  
Vol 12 (1) ◽  
pp. 237-256 ◽  
Author(s):  
G. Schurgers ◽  
F. Lagergren ◽  
M. Mölder ◽  
A. Lindroth
Keyword(s):  
Large Scale ◽  
Gross Primary Production ◽  
Coniferous Forest ◽  
Co2 Concentration ◽  
Early Morning ◽  
Global Scale ◽  
Canopy Exchange ◽  
Exchange Processes ◽  
Vertical Heterogeneity ◽  
Stable Conditions

Abstract. Plant canopies affect the canopy micrometeorology, and thereby alter canopy exchange processes. For the simulation of these exchange processes on a regional or global scale, large-scale vegetation models often assume homogeneous environmental conditions within the canopy. In this study, we address the importance of vertical variations in light, temperature, CO2 concentration and humidity within the canopy for fluxes of photosynthesis and transpiration of a boreal coniferous forest in central Sweden. A leaf-level photosynthesis-stomatal conductance model was used for aggregating these processes to canopy level while applying the within-canopy distributions of these driving variables. The simulation model showed good agreement with eddy covariance-derived gross primary production (GPP) estimates on daily and annual timescales, and showed a reasonable agreement between transpiration and observed H2O fluxes, where discrepancies are largely attributable to a lack of forest floor evaporation in the model. Simulations in which vertical heterogeneity was artificially suppressed revealed that the vertical distribution of light is the driver of vertical heterogeneity. Despite large differences between above-canopy and within-canopy humidity, and despite large gradients in CO2 concentration during early morning hours after nights with stable conditions, neither humidity nor CO2 played an important role for vertical heterogeneity of photosynthesis and transpiration.

Studies on Acacia mangium in Kemasul Forest, Malaysia. I. Biomass and productivity

1988 ◽  
Vol 4 (3) ◽  
pp. 293-302 ◽  
Author(s):  
Lim Meng Tsai
Keyword(s):  
Leaf Litter ◽  
Large Scale ◽  
Acacia Mangium ◽  
Litter Production ◽  
Above Ground Biomass ◽  
Annual Increment ◽  
High Turnover ◽  
Litter Accumulation ◽  
Ground Biomass ◽  
The Mean

ABSTRACTMalaysia is establishing large-scale plantations for reforestation and the production of wood for pulp and paper as well as for light construction. The main species used currently is the exotic legume Acacia mangium. The above-ground biomass, litter production and litter accumulation in a four-year-old stand in Peninsular Malaysia were studied. The mean diameter at breast height (dbh) was 12 cm. The mean annual increment (MAI) in dbh of individual trees ranged from 0.9 to 5.1 cm while MAI in height of sample trees ranged from 2.9 to 5.5 m. The total above-ground biomass of the stand was 90.4 t ha−1, consisting of 57.6 t stem, 14.1 t branch and 5.4 t leaf. Litter production averaged 10.23 t ha−1 yr−1 with leaf litter making up 87.4% of the total. Leaf litter accumulation amounted to 6.64 t ha−1 and the turnover constant of leaf litter was estimated at 1.35. The high productivity is discussed in relation to the high turnover of foliage and the low turnover of litter.

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