@article {KNZ001944,
	title = {Assessing precipitation, evapotranspiration, and NDVI as controls of U.S. Great Plains plant production},
	journal = {Ecosphere},
	volume = {10},
	year = {2019},
	pages = {e02889},
	abstract = {<p>Productivity 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 of ANPP to AET, precipitation, and plant transpiration (Tr). We used multi-year ANPP data from five sites ranging from semiarid grasslands in Colorado and Wyoming to mesic grasslands in Nebraska and Kansas, mean annual NRCS ANPP, and satellite-derived normalized difference vegetation index (NDVI) data. Results from the five sites showed that cumulative April-to-July AET, precipitation, and Tr were well correlated (R2: 0.54\&ndash;0.70) to annual changes in ANPP for all but the wettest site. AET and Tr were better correlated to annual changes in ANPP compared 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 in ANPP in the most mesic site, while AET and Tr were poorly correlated with ANPP at this site. Cumulative growing season (May-to-September) NDVI (iNDVI) was strongly correlated with annual ANPP at the five sites (R2 = 0.90). Using iNDVI as a surrogate for ANPP, we found that county-level cumulative April\&ndash;July AET was more strongly correlated to ANPP than precipitation for more than 80\% of the GP counties, with precipitation tending to perform better in the eastern more mesic portion of the GP. Including the ratio of AET to potential evapotranspiration (PET) improved the correlation of AET to both iNDVI and mean county-level NRCS ANPP. Accounting for how different precipitation-related variables control ANPP (AET in drier portion, precipitation in wetter portion) provides opportunity to develop spatially explicit forecasting of ANPP across the GP for enhancing decision-making by land managers and use of grassland ANPP for biofuels.</p>},
	keywords = {LTER-KNZ},
	doi = {10.1002/ecs2.2889},
	url = {https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecs2.2889},
	author = {Chen, Maosi and Parton, William J. and Hartman, Melannie D. and Del Grosso, Stephen J. and Smith, William K. and Alan K. Knapp and Lutz, Susan and Derner, Justin D. and Tucker, Compton J. and Ojima, Dennis S. and Volesky, Jerry D. and Stephenson, Mitchell B. and Schacht, Walter H. and Gao, Wei}
}
@article {KNZ001884,
	title = {Regional grassland productivity responses to precipitation during multiyear above- and below-average rainfall periods},
	journal = {Global Change Biology},
	volume = {24},
	year = {2018},
	pages = {1935 - 1951},
	abstract = {<p>There is considerable uncertainty in the magnitude and direction of changes in precipitation associated with climate change, and ecosystem responses are also uncertain. Multiyear periods of above- and below-average rainfall may foretell consequences of changes in rainfall regime. We compiled long-term aboveground net primary productivity (ANPP) and precipitation (PPT) data for eight North American grasslands, and quantified relationships between ANPP and PPT at each site, and in 1-3\&nbsp;year periods of above- and below-average rainfall for mesic, semiarid cool, and semiarid warm grassland types. Our objective was to improve understanding of ANPP dynamics associated with changing climatic conditions by contrasting PPT-ANPP relationships in above- and below-average PPT years to those that occurred during sequences of multiple above- and below-average years. We found differences in PPT-ANPP relationships in above- and below-average years compared to long-term site averages, and variation in ANPP not explained by PPT totals that likely are attributed to legacy effects. The correlation between ANPP and current- and prior-year conditions changed from year to year throughout multiyear periods, with some legacy effects declining, and new responses emerging. Thus, ANPP in a given year was influenced by sequences of conditions that varied across grassland types and climates. Most importantly, the influence of prior-year ANPP often increased with the length of multiyear periods, whereas the influence of the amount of current-year PPT declined. Although the mechanisms by which a directional change in the frequency of above- and below-average years imposes a persistent change in grassland ANPP require further investigation, our results emphasize the importance of legacy effects on productivity for sequences of above- vs. below-average years, and illustrate the utility of long-term data to examine these patterns.</p>},
	keywords = {LTER-KNZ},
	doi = {10.1111/gcb.2018.24.issue-510.1111/gcb.14024},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/29265568},
	author = {Petrie, Matthew D. and Peters, Debra P. C. and Yao, Jin and John M. Blair and Burruss, Nathan D. and Scott. L. Collins and Derner, Justin D. and Gherardi, Laureano A. and Hendrickson, John R. and Sala, Osvaldo E. and Starks, Patrick J. and Steiner, Jean L.}
}
