Seasonal Precipitation Legacy Effects Determine the Carbon Balance of a Semiarid Grassland

Abstract

Semiarid grasslands are water-limited ecosystems where precipitation (PPT) controls the onset and duration of the growing season; however, this variable does not fully explain interannual variability of productivity at temporal scales. We examined the relationship between PPT and carbon (C) fluxes in a semiarid grassland at both seasonal and interannual scales, as well as the role of lagged effects of PPT and asymmetric sensitivities of net ecosystem carbon exchange to PPT and its components (gross ecosystem exchange [GEE] and ecosystem respiration [ER]). Six years of continuous net ecosystem C exchange data measured with the eddy covariance technique and GEE estimated with 15 years of enhanced vegetation index and the gross primary productivity of Moderate Resolution Imaging Spectroradiometer were used. The semiarid grassland was a C source and a C sink among contrasting PPT years (114 to −107 g C·m −2 ·year −1 ). At seasonal scale, PPT relationship with the 15 years of GEE derived from enhanced vegetation index and gross primary productivity was sigmoidal. Moreover, PPT legacies of the previous dry season determined the C balance of the grassland by affecting the C uptake and ecosystem respiration of the following growing season, but productivity was more sensitive to PPT changes than respiration. Models of climate change for semiarid grasslands in North America predict up to 30% reduction of winter-spring PPT and slight summer PPT decrease. Thus, our results suggest that future changes in PPT may have a strong impact on the C uptake capacity of this ecosystem due to weakened legacy effects in summer C uptake.

Drought and heatwave impacts on semi-arid ecosystems' carbon fluxes along a precipitation gradient

“…On the other hand, GPP and Reco will not follow the linear relation but will converge faster towards 0 if no water is available for longer periods. For shorter periods, legacy effects must be considered [7,33,34] as they will impact these relations. A longer dataset of these similar sites with more positive and negative precipitation extremes will surely help to better understand the processes and impacts of precipitation to the carbon cycle.…”

Variations in diurnal and seasonal net ecosystem carbon dioxide exchange in a semiarid sandy grassland ecosystem in China's Horqin Sandy Land

“…Before the summer growing season, both GPP and R ec increased with increasing temperature and precipitation (Niu et al, 2011;Rey et al, 2011). However, plants are just beginning to germinate in the spring, so the carbon sequestration capacity of the ecosystem is less than the carbon release capacity (Delpierre et al, 2010;Liu et al, 2016a;Zhang et al, 2016). Therefore, the ecosystem was a net CO 2 source.…”

Landscape Controls on Water‐Energy‐Carbon Fluxes Across Different Ecosystems During the North American Monsoon

“…At SS, grasses, shrubs, cacti, and shallow rooted trees have limited access to water below the upper soil profile (Tarín et al., 2020). Note that SS and OS are documented as part of the MexFlux network but had been discontinued prior to this effort (Delgado‐Balbuena, Arredondo, et al., 2019; Vargas et al., 2013), while RM represents a new site with riparian characteristics not captured in MexFlux. Site conditions and their representativeness in the broader domain are shown in Figure 2.…”

“…While Méndez-Barroso et al (2014) identified differences in vegetation phenology and seasonal evapotranspiration rates at two of the sites, the study was not able to distinguish sources of water nor link the plant water uptake to carbon fluxes. Thus, we deployed sensors at the subtropical scrubland and oak savanna sites that form part of the MexFlux network (Delgado-Balbuena, Arredondo, et al, 2019;Vargas et al, 2013), but which had been discontinued, and expanded observations to a third site in a riparian mesquite woodland to allow comparisons of the landscape controls described above. The new site offered the opportunity to identify how access to groundwater at a low elevation location influenced the water-energy-carbon fluxes.…”