Knowledge of climatic and management influences on large herbivore production (LHP, kg/ha) are needed for semiarid grasslands to address potential consequences of both increasing climate variability and the need to increase animal protein 70% by 2050. Here, we present an 80-yr data set (1939-2018) on LHP from the shortgrass steppe, aiming to answer 1) whether LHP is related to sea-surface temperature (SST) anomalies, Pacific Decadal Oscillation (PDO) and El Nio Southern Oscillation (ENSO), which are key drivers of annual net primary productivity at our study area; and 2) whether grazing intensity modulates the sensitivity of LHP to climatic determinants. Grazing season (mid-May to October) weight gains have been recorded since 1939 at the USDA-Agricultural Research Service’s Central Plains Experimental Range, a Long-Term Agroecosystem Research (LTAR) site. Hypotheses evaluated were: 1) does phase of PDO influence LHP, 2) how does ENSO influence LHP within PDO phase, and 3) does grazing intensity increase sensitivity to the SST anomalies? Hereafter, PDO (+) and PDO (-) refer to warm and cold PDO phases, respectively, whereas ENSO (+) and ENSO (-) indicate La Niña and El Niño events.
Results/Conclusions
Greater mean LHP and inter-annual variation in LHP occurred in cold PDO phases (mean and coefficient of variation:= 15.0 kg/ha, cv = 39.3), while LHP was high and more stable during warm PDO phases (= 16.2 kg/ha, cv = 36.6). Inter-annual variation of LHP under heavy and moderate grazing intensity was greater and mean LHP lower in cold PDO phases (heavy = 18.7.2, cv = 36.0; moderate = 14.9, cv = 29.8) than warm PDO phases (heavy = 20.2, cv = 30.5; moderate = 16.0, cv = 28.0), while LHP under light grazing appeared to be less sensitive to PDO phase (cold = 11.4, cv = 31.2; warm =12.1, cv = 31.7). When compared to warm PDOs (+) and warm ENSO (+) periods (31% higher LHP variance for heavy than moderate grazing intensity), variance of LHP under heavy grazing intensity was up to two times greater than moderate grazing intensity for PDO (+), ENSO (-): 66%; PDO (-), (ENSO (+): 61%; and PDO (-), ENSO (-): 50% periods. With knowledge of PDO phases and ENSO events, which are publicly available with a 1-3 month lag time via NOAA, managers can use this data on mean responses and associated variance to help with strategic and tactical decisions.