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

Abstract

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.

Urban land cover type determines the sensitivity of carbon dioxide fluxes to precipitation in Phoenix, Arizona

“…In contrast, the parking lot at PL exhibited a very small increase in CO 2 emissions (higher FC) after rainfall events during the early summer that was Carbon dioxide fluxes in Phoenix, Arizona also noted at REF ( Fig 10B), but not at a significant level (mm byt m = 0.33). This suggests that additional water from precipitation during a period of high temperatures in May and June promotes CO 2 efflux, mainly by increasing soil respiration in bare soil areas, in a similar fashion as noted in natural ecosystems of the region [90,91,99,100]. During other times of the year, the site with ample outdoor water use (ML) does not respond to precipitation (FC remains the same), suggesting that a decoupling occurs between CO 2 fluxes and storm inputs as commonly found in mesic regions.…”

Climate and human water use diminish wetland networks supporting continental waterbird migration

“…While groundwater connections are unknown, it was clear that monsoon rainfall patterns were an important driver of wetland area in monsoonal watersheds. Analysis of future climate in the Mexican Highlands predicts precipitation from 2030 to 2045 to be variable, but remains similar to patterns of recent decades (Verduzco et al, 2018). Although Cook and Seager (2013) similarly found that by 2080-2099 total precipitation would remain approximately the same, the timing of peak monsoon rainfall would shift from June-July to September-October.…”

Evapotranspiration flux partitioning at a multi-species shrubland with stable isotopes of soil, plant, and atmosphere water pools

“…The study site is a subtropical shrubland near the town of Rayón, Sonora at coordinates 110.53º W and 29.74º N at ~630 m asl., and is part of the MexFlux network (Vargas et al, 2013;Villareal et al, 2016). The climate of the region is semi-arid, BSh according to Köppen's Classification (Verduzco et al 2018). (Watts et al, 2007), which brings about 60% of the annual precipitation.…”

“…For this reason, most of the species at the site lose their leaves in the dry season (from October to June) and recover their greenness in late June or early July. Several hydrological and eco-hydrological studies have been conducted in this site (Tarin et al, 2014;Vivoni et al, 2010;Mendez-Barrozo et al, 2014;Verduzco et al, 2018).…”