15-Yr Biomass Production in Semiarid Nebraska Sandhills Grassland: Part 2-Response to Seasonal Precipitation and Temperature

Aboveground plant biomass production can exhibit varied responses to within- and across-season weather variability. Using a long-term data set (2007–2021) collected annually from grazing exclosures in a Sandhills grassland in Nebraska, USA, our part-1 paper reported 15 yr of changes in grassland plant production. In this paper, we modeled seasonal weather impacts on total plant biomass and biomass of three plant functional groups using stepwise (forward) linear regression. Biomass data were measured for the following three periods each year: early season (April to midJune), late season (midJune to midAugust), and full season (April to midAugust). Weather variables, derived from precipitation and temperature, were categorized into amount, index, and pattern variables. The temporal variability of each weather variable was quantified across four time periods: three within-season conditions (early season, late-season, and full-season periods of the current year) and an across-season condition (the full-season period of the previous year). The results indicated that plant production responses varied among functional groups and across time periods. Late-season C 4 -grass production significantly increased under wetter summer conditions ( P < 0.05). A dry growing season in the previous year tended to decrease subsequent-year early season C 3 -grass production ( P < 0.05), and a warmer growing season in the previous year was likely to enhance subsequent-year forb production ( P < 0.001). Total plant production exhibited more complex seasonal patterns, primarily driven by the differences in individual plant functional groups during specific growing periods. This complexity reflects the collective responses of mixed plant functional groups to weather variability. Understanding these complex relationships is fundamental to predicting grassland plant production as well as developing and implementing appropriate grazing strategies that adapt to changing climate variability. This study will ultimately support the enhancement of ecological sustainability and resilience of the Sandhills semiarid grassland ecosystem.