A single drought event of 100‐year recurrence enhances subsequent carbon uptake and changes carbon allocation in experimental grassland communities

Abstract

Evidence suggests that the expected increase in frequency and magnitude of extreme weather events during climate change will alter plant productivity. Therefore, extreme weather events might also be capable of changing C sequestration and allocation. Here, experimental grassland communities of two species compositions, differing in their diversity, were exposed either to a simulated single drought or to a heavy-rainfall event. The magnitude of these manipulations imitated the local 100-year weather extreme according to extreme-value statistics. Effects on Net Ecosystem CO 2 Exchange (NEE in lmol m -2 s -1 ) as well as aboveground biomass production and leaf-area index (LAI) were recorded from prior to the manipulations until two months after the manipulations ended. Initial light utilization efficiency and maximum NEE increased after the drought. No change in the respiration was detected and maximum uptake capacity (GPP max ) was 15% higher for the drought-manipulated plots compared to controls, which indicates an enhanced CO 2 uptake into the systems. The level of diversity was also found to alter the lightresponse curves, increasing respiration and maximum NEE to a higher degree than drought in the more diverse compared to the less diverse community. This resulted in an increase of GPP max by 55%. No significant interactions between species composition and weather manipulations were detected. Interestingly, aboveground biomass production was not significantly affected by weather manipulations, even though LAI increased due to drought. This increase was caused by a decrease in the ratio between reproductive and vegetative growth. The heavyrainfall manipulation resulted in no significant effects. Our data suggest that C sequestration can be enhanced by a single weather event. However the importance, long-term duration, and thresholds or turning points of such effects need to be investigated further as intensification of weather extremes is currently emerging as one of the most important facets of climate change.

Remote sensing of annual terrestrial gross primary productivity from MODIS: an assessment using the FLUXNET La Thuile data set

“…In GRA, correlations between anomalies in mean EVI (and NDVI) and anomalies in GPP suggest that interannual variability in GPP in grasslands is tightly coupled to leaf area and supports the hypothesis that grasslands use LAI regulation to avoid moisture stress (Jenerette et al, 2009). Our results suggest that mean EVI and NDVI successfully capture the effect of moisture variability on GPP at GRA and SSMF sites, including moderate drought conditions when GPP can actually increase because of increases in LAI (Nagy et al, 2007;Mirzaei et al, 2008;Aires et al, 2008).…”

Lasting effects of climate disturbance on perennial grassland above‐ground biomass production under two cutting frequencies

“…), as previously measured on artificial grassland (Zavalloni et al ., ). Recovery of green tissue may be associated with compensatory growth (Oesterheld & McNaughton, ), although this is not a general rule, as several authors have stressed (Mirzaei et al ., ; Hartmann & Niklaus, ). Here, the higher autumn biomass production by the plant community and grasses in Cut− compared to the C treatment (Fig.…”

Ecotypes of European grass species respond differently to warming and extreme drought

“…2008). Furthermore, Mirzaei et al. (2008) found that temporally limited but extreme drought events may cause strong repercussions in the carbon cycling of grassland communities.…”