Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Documenting year-to-year variations in carbon storage potential in terrestrial ecosystems is crucial for the determination of carbon dioxide (CO<span class="inline-formula"><sub>2</sub></span>) emissions. However, the magnitude, pattern, and inner biomass partitioning of carbon storage potential and the effect of the changes in climate and CO<span class="inline-formula"><sub>2</sub></span> on inner carbon stocks remain poorly quantified. Herein, we use a spatially explicit individual-based dynamic global vegetation model to investigate the influences of the changes in climate and CO<span class="inline-formula"><sub>2</sub></span> on the enhanced carbon storage potential of vegetation. The modelling included a series of factorial simulations using the Climatic Research Unit (CRU) dataset from 1916 to 2015. The results show that CO<span class="inline-formula"><sub>2</sub></span> predominantly leads to a persistent and widespread increase in light-gathering vegetation biomass carbon stocks (LVBC) and water-gathering vegetation biomass carbon stocks (WVBC). Climate change appears to play a secondary role in carbon storage potential. Importantly, with the intensification of water stress, the magnitude of the light- and water-gathering responses in vegetation carbon stocks gradually decreases. Plants adjust carbon allocation to decrease the ratio between LVBC and WVBC for capturing more water. Changes in the pattern of vegetation carbon storage were linked to zonal limitations in water, which directly weaken and indirectly regulate the response of potential vegetation carbon stocks to a changing environment. Our findings differ from previous modelling evaluations of vegetation that ignored inner carbon dynamics and demonstrate that the long-term trend in increased vegetation biomass carbon stocks is driven by CO<span class="inline-formula"><sub>2</sub></span> fertilization and temperature effects that are controlled by water limitations.

Highlights

  • As a result of the changes in climate and atmospheric carbon dioxide (CO2), the terrestrial ecosystem carbon cycle exhibits remarkable trends in interannual variations, which induce uncertainty in estimated carbon budgets (Erb et al, 2018; Keenan et al, 2017)

  • We obtained the dataset from the Ecosystem Model-Data Intercomparison (EMDI) working group, and compared their data with modelled multiyear average net primary production (NPP) in the period of 1916-1999

  • The determined coefficient (R2) between EMDI observed and estimated multiyear average NPP of 669 in-situ observations is 0.54, which is significant at the p=0.01 level

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Summary

Introduction

As a result of the changes in climate and atmospheric carbon dioxide (CO2), the terrestrial ecosystem carbon cycle exhibits remarkable trends in interannual variations, which induce uncertainty in estimated carbon budgets (Erb et al, 2018; Keenan et al, 2017). Warming has a negative effect on the percentage of roots in dry regions and increases the ratio of above- versus belowground biomass in wet regions (Ma et al., 2021) This is apparent in tropical regions, where variations in water availability can result in different responses in the processes involved in the carbon cycle (Liu et al, 2017). We use a spatially explicit individual-based dynamic global vegetation model (SEIB-DGVM), along with the root-shoot ratio method (R/S) to (1) systematically determine the long-term variability of carbon-sequestration potential and understand its response mechanisms, and (2) estimate trends in partitioning of potential biomass carbon-stocks of vegetation biomass. 2.2), the representation of biomass carbon-stock partitioning in the SEIB-DGVM (Sect. 2.3), an overview of the experimental scheme used in the model simulations (Sect. 2.4), and the validation of model results (Sect. 2.5)

Forcing Data
Overview of modelling concept in SEIB-DGVM
Parameterization of daily allocation
Carbon-stock partitioning method
Setup of model runs
Factorial simulation scheme
Non-parametric test methods
Distinguishing hydrological regions
Evaluation of SEIB-DGVM
Enhanced carbon-stocks and its fractions
Spatial variability in estimated AVBC and BVBC trends
Responses of AVBC and BVBC to environmental drivers
Constraints imposed by water limitations
Conclusions and discussions
Code and data availability statement
Full Text
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