We used long-term observations of grassland aboveground net plant production (ANPP, 19392016), growing seasonal advanced very-high-resolution radiometer remote sensing normalized difference vegetation index (NDVI) data (1982-2016), and simulations of actual evapotranspiration (1912-2016) to evaluate the impact of Pacific Decadal Oscillation (PDO) and El Nino-Southern Oscillation (ENSO) sea surface temperature (SST) anomalies on a semiarid grassland in northeastern Colorado. Because ANPP was well correlated (R-2 = 0.58) to cumulative April to July actual evapotranspiration (iAET) and cumulative growing season NDVI (iNDVI) was well correlated to iAET and ANPP (R-2 = 0.62 [quadratic model] and 0.59, respectively), we were able to quantify interactions between the long-duration (15-30 yr) PDO temperature cycles and annual-duration ENSO SST phases on ANPP. We found that during cold-phase PDOs, mean ANPP and iNDVI were lower, and the frequency of low ANPP years (drought years) was much higher, compared to warm-phase PDO years. In addition, ANPP, iNDVI, and iAET were highly variable during the cold-phase PDOs. When NINO-3 (ENSO index) values were negative, there was a higher frequency of droughts and lower frequency of wet years regardless of the PDO phase. PDO and NINO-3 anomalies reinforced each other resulting in a high frequency of above-normal iAET (52%) and low frequency of drought (20%) when both PDO and NINO-3 values were positive and the opposite pattern when both PDO and NINO-3 values were negative (24% frequency of above normal and 48% frequency of drought). Precipitation variability and subsequent ANPP dynamics in this grassland were dampened when PDO and NINO-3 SSTs had opposing signs. Thus, primary signatures of these SSTs in this semiarid grassland are (1) increased interannual variability in ANPP during cold-phase PDOs, (2) drought with low ANPP occurring in almost half of those years with negative values of PDO and NINO-3, and (3) high precipitation and ANPP common in years with positive PDO and NINO-3 values.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/626547 |
| Date | 12 1900 |
| Creators | Chen, Maosi, Parton, William J., Del Grosso, Stephen J., Hartman, Melannie D., Day, Ken A., Tucker, Compton J., Derner, Justin D., Knapp, Alan K., Smith, William K., Ojima, Dennis S., Gao, Wei |
| Contributors | Univ Arizona, Sch Nat Resources & Environm, United States Department of Agriculture UV-B Monitoring and Research Program; Natural Resource Ecology Laboratory; Colorado State University; Fort Collins Colorado 80521 USA, Natural Resource Ecology Laboratory; Colorado State University; Fort Collins Colorado 80523 USA, Natural Resource Ecology Laboratory; Colorado State University; Fort Collins Colorado 80523 USA, United States Department of Agriculture UV-B Monitoring and Research Program; Natural Resource Ecology Laboratory; Colorado State University; Fort Collins Colorado 80521 USA, Climate Variability Unit; Science Division; Department of Science, Information Technology and Innovation; Brisbane Queensland 4001 Australia, Earth Resources Branch; NASA/Goddard Space Flight Center; Greenbelt Maryland 20771 USA, United States Department of Agriculture; Agricultural Research Service (USDA-ARS); Rangeland Resources and Systems Research Unit; Cheyenne Wyoming 82009 USA, Department of Biology and Graduate Degree Program in Ecology; Colorado State University; Fort Collins Colorado 80523-1878 USA, School of Natural Resources and the Environment; University of Arizona; Tucson Arizona 85721 USA, Natural Resource Ecology Laboratory; Colorado State University; Fort Collins Colorado 80523 USA, United States Department of Agriculture UV-B Monitoring and Research Program; Natural Resource Ecology Laboratory; Colorado State University; Fort Collins Colorado 80521 USA |
| Publisher | WILEY |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | Article |
| Rights | © 2017 Chen et al. This is an open access article under the terms of the Creative Commons Attribution License. |
| Relation | http://doi.wiley.com/10.1002/ecs2.2069 |
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