The carbon cycle in Mexico: past, present and future of C stocks and fluxes

G Murray-Tortarolo,F Murguía-Flores,S Zaehle,Y Liu,A Harper,C Koven,A Jain,B D Stocker,A Arneth,A Wiltshire,A Anav,E Kato,N Zeng,B Poulter,S Sitch,A Arvanitis,P Friedlingstein,V J Jaramillo

doi:10.5194/bg-13-223-2016

Abstract

Abstract. We modeled the carbon (C) cycle in Mexico with a process-based approach. We used different available products (satellite data, field measurements, models and flux towers) to estimate C stocks and fluxes in the country at three different time frames: present (defined as the period 2000–2005), the past century (1901–2000) and the remainder of this century (2010–2100). Our estimate of the gross primary productivity (GPP) for the country was 2137 ± 1023 TgC yr−1 and a total C stock of 34 506 ± 7483 TgC, with 20 347 ± 4622 TgC in vegetation and 14 159 ± 3861 in the soil.Contrary to other current estimates for recent decades, our results showed that Mexico was a C sink over the period 1990–2009 (+31 TgC yr−1) and that C accumulation over the last century amounted to 1210 ± 1040 TgC. We attributed this sink to the CO2 fertilization effect on GPP, which led to an increase of 3408 ± 1060 TgC, while both climate and land use reduced the country C stocks by −458 ± 1001 and −1740 ± 878 TgC, respectively. Under different future scenarios, the C sink will likely continue over the 21st century, with decreasing C uptake as the climate forcing becomes more extreme. Our work provides valuable insights on relevant driving processes of the C cycle such as the role of drought in drylands (e.g., grasslands and shrublands) and the impact of climate change on the mean residence time of soil C in tropical ecosystems.

Highlights

The global carbon (C) cycle has been altered by anthropogenic activity with the release of CO2 into the atmosphere through fossil fuel burning and land use and land cover changes since the industrial revolution
In terms of the country’s geography, we found the highest gross primary productivity (GPP) in the south and southeast with a steep decrease to the north; the lowest GPP occurred in north-central region (Fig. 2a)
There are quite recent estimates of GPP at the site and regional levels determined from flux tower measurements of tropical dry forest in the northern range of its distribution (Verduzco et al, 2015; see Fig. Simulation 1 (S1)) and from fPAR as a proxy of GPP for the Baja California Peninsula (Reimer et al, 2015)

Summary

Introduction

The global carbon (C) cycle has been altered by anthropogenic activity with the release of CO2 into the atmosphere through fossil fuel burning and land use and land cover changes since the industrial revolution About 50 % of the annual anthropogenic emissions are sequestered in the marine and terrestrial ecosystems (Le Quéré et al, 2014). In the latter, the atmospheric CO2 increase has led to greater gross primary productivity (GPP), as a result of the fertilization effect on the plants’ photosynthetic machinery, leading to higher C storage (Norby et al, 2005). GPP and the net biome productivity (NBP) display high interannual variability due to the effect of climate variability on vegetation processes (e.g., plant production and water use, growing season extension, fire, drought induced mortality; Sitch et al, 2015)

Methods

Results

Conclusion