Abstract
AbstractProductivity throughout the North American Great Plains grasslands is generally considered to be water limited, with the strength of this limitation increasing as precipitation decreases. We hypothesize that cumulative actual evapotranspiration water loss (AET) from April to July is the precipitation‐related variable most correlated to aboveground net primary production (ANPP) in the U.S. Great Plains (GP). We tested this by evaluating the relationship ofANPPtoAET, precipitation, and plant transpiration (Tr). We used multi‐yearANPPdata from five sites ranging from semiarid grasslands in Colorado and Wyoming to mesic grasslands in Nebraska and Kansas, mean annualNRCS ANPP, and satellite‐derived normalized difference vegetation index (NDVI) data. Results from the five sites showed that cumulative April‐to‐JulyAET, precipitation, and Tr were well correlated (R2: 0.54–0.70) to annual changes inANPPfor all but the wettest site.AETand Tr were better correlated to annual changes inANPPcompared to precipitation for the drier sites, and precipitation in August and September had little impact on productivity in drier sites. April‐to‐July cumulative precipitation was best correlated (R2 = 0.63) with interannual variability inANPPin the most mesic site, whileAETand Tr were poorly correlated withANPPat this site. Cumulative growing season (May‐to‐September)NDVI(iNDVI) was strongly correlated with annualANPPat the five sites (R2 = 0.90). UsingiNDVIas a surrogate forANPP, we found that county‐level cumulative April–JulyAETwas more strongly correlated toANPPthan precipitation for more than 80% of theGPcounties, with precipitation tending to perform better in the eastern more mesic portion of theGP. Including the ratio ofAETto potential evapotranspiration (PET) improved the correlation ofAETto bothiNDVIand mean county‐levelNRCS ANPP. Accounting for how different precipitation‐related variables controlANPP(AETin drier portion, precipitation in wetter portion) provides opportunity to develop spatially explicit forecasting ofANPPacross theGPfor enhancing decision‐making by land managers and use of grasslandANPPfor biofuels.
Highlights
Grassland and savanna ecosystems make up > 30% of the global land surface (Asner et al 2004, Li et al 2017)
The absolute amount of water loss from transpiration increased with increasing annual precipitation, while the bare soil evaporation and plant interception water loss were similar for all of the sites with the fraction of water loss from evaporation decreasing with increasing precipitation and decreasing aridity index (43% [32.8 + 10.5%] for Central Plains Experimental Range (CPER) vs. 23% [16.8 + 6.0%] for Konza Prairie (KNZ))
Tr had higher correlations to aboveground net primary production (ANPP), but correlations were similar for actual evapotranspiration (AET) and precipitation, and there was a gradual drop-off in the correlations of all the variables to ANPP for time periods greater than April to August as observed for the dry High Plains Grasslands Research Station (HPGRS) and CPER sites
Summary
Grassland and savanna ecosystems make up > 30% of the global land surface (Asner et al 2004, Li et al 2017). Numerous studies (Lauenroth 1979, Sala et al 1988, Del Grosso et al 2008) have shown that mean annual precipitation (MAP) is the major factor determining grassland aboveground net primary production (ANPP) with ANPP increasing linearly with increasing MAP at the site, regional, and global scales. Lauenroth and Sala (1992) have shown that ANPP increases linearly with increasing MAP at the site and regional levels for Great Plains (GP) grasslands; the slope of the change in annual ANPP with increasing precipitation at the site level is much lower than the slope for regional changes in mean ANPP with increasing MAP. Sites with lower MAP tend to have steeper slopes than more mesic sites, suggesting that water limitations are strongest in drier grasslands
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
