Analysing the capacity of two Mediterranean semiarid ecosystems located in the southeast Spain as methane sinks

Abstract

For the last decade there has been a continuous increase in atmospheric methane. Methane (CH4) is the second most important greenhouse gas (after carbon dioxide, CO2). However, despite the recent international effort to quantify global CH4 fluxes, such information is still limited, with a significant source of uncertainty (from 51% to 82%) mainly attributed to emissions from wetlands and other inland waters. On the other hand, some research in arid ecosystems (drylands) has shown that they play an important role in the CH4 cycle as CH4 sinks. These uncertainties in quantifying potential methane sinks highlight the need to increase our understanding of this effect of dryland ecosystems.In this study we have quantified the capacity of two Mediterranean ecosystems as methane sinks. A lowland site located at 200 m.a.s.l and 6 km from the coast, in Cabo de Gata Natural Park (Almería, Spain; N36°56′26.0″, W2°01′58.8). This lowland is dominated by Stipa tenacissima at 60 % cover. And a subalpine site located at 1,600 m.a.s.l. and 25 km from the coast, in Sierra de Gádor (Almería; 36º55′41.7″N; 2º45′ 1.7″W). This site is a shrubland plateau derived from an open forest and its climate is Mediterranean with hot summers. Both study sites are included in the international network FLUXNET (https://fluxnet.org/about/).For this purpose, two techniques have been used, the Eddy covariance technique to measure CH4 fluxes at the ecosystem scale and a standardized camera system composed by an infrared gas analyser (LI-7810, Li-Cor, Lincoln, NE, USA) connected to a Smart Chamber (8200-01S, Li-Cor, Lincoln, NE, USA), to measure soil CH4 fluxes in intensive campaigns. The Eddy covariance technique was applied for several weeks during the dry season, while the camera system was used to measure fluxes during the rainy season and in the middle of the growing season. Thanks to this study we will be able to establish an approximate range of CH4 assimilation by these ecosystems, comparing this value with those obtained in other studies; additionally, we will analyse the effect of the different soil conditions (humidity, temperature, porosity, texture...) on CH4 fluxes in these "drylands".This work was supported by the projects P20_00016 (BAGAMET) and LifeWatch-2019-10-UGR-01, co-funded by the MICINN through the FEDER funds.