Climate Change Impacts on Net Ecosystem Productivity in a Subtropical Shrubland of Northwestern México

• Published in: Journal of geophysical research. Biogeosciences 2018-02, Vol.123 (2), p.688-711
• Main Authors: Verduzco, Vivian S., Vivoni, Enrique R., Yépez, Enrico A., Rodríguez, Julio C., Watts, Christopher J., Tarin, Tonantzin, Garatuza‐Payán, Jaime, Robles‐Morua, Agustin, Ivanov, Valeriy Y.
• Format: Article
• Language: English
• Subjects: Air temperature; Biological fertilization; Carbon; Carbon dioxide; carbon fluxes; Climate change; Computer simulation; Covariance; Data processing; Ecohydrology; Ecosystems; eddy covariance; Environmental assessment; Environmental impact; Fertilization; Fluxes; Mathematical models; modeling; North American monsoon; Precipitation; Primary production; Productivity; Rain; Rainfall; Shrublands; Soil; Summer; Vortices; Water use; Water use efficiency
• ISSN: 2169-8953; 2169-8961
• DOI: 10.1002/2017JG004361

The sensitivity of semiarid ecosystems to climate change is not well understood due to competing effects of soil and plant‐mediated carbon fluxes. Limited observations of net ecosystem productivity (NEP) under rising air temperature and CO2 and altered precipitation regimes also hinder climate change assessments. A promising avenue for addressing this challenge is through the application of numerical models. In this work, we combine a mechanistic ecohydrological model and a soil carbon model to simulate soil and plant processes in a subtropical shrubland of northwest México. Due to the influence of the North American monsoon, the site exhibits net carbon losses early in the summer and net carbon gains during the photosynthetically active season. After building confidence in the simulations through comparisons with eddy covariance flux data, we conduct a series of climate change experiments for near‐future (2030–2045) scenarios that test the impact of meteorological changes and CO2 fertilization relative to historical conditions (1990–2005). Results indicate that reductions in NEP arising from warmer conditions are effectively offset by gains in NEP due to the impact of higher CO2 on water use efficiency. For cases with higher summer rainfall and CO2 fertilization, climate change impacts lead to an increase of ~25% in NEP relative to historical conditions (mean of 66 g C m−2). Net primary production and soil respiration derived from decomposition are shown to be important processes that interact to control NEP and, given the role of semiarid ecosystems in the global carbon budget, deserve attention in future simulation efforts of ecosystem fluxes. Key Points Model simulation accurately captured the seasonality of vegetation activity Net ecosystem productivity decreased under reduced summer rainfall and increased temperature scenarios Elevated CO2 scenarios offset the negative impacts of meteorological conditions