02388nas a2200205 4500008004100000022001400041245010800055210006900163300001400232490000800246520170300254100003001957700002801987700002202015700002602037700002402063700001602087700002002103856005902123 2018 eng d a1385-023700aLegacy effects of a regional drought on aboveground net primary production in six central US grasslands0 aLegacy effects of a regional drought on aboveground net primary  a505 - 5150 v2193 a

Global climate models predict increases in the frequency and severity of drought worldwide, directly affecting most ecosystem types. Consequently, drought legacy effects (drought-induced alterations in ecosystem function postdrought) are expected to become more common in ecosystems varying from deserts to grasslands to forests. Drought legacies in grasslands are usually negative and reduce ecosystem function, particularly after extended drought. Moreover, ecosystems that respond strongly to drought (high sensitivity) might be expected to exhibit the largest legacy effects the next year, but this relationship has not been established. We quantified legacy effects of a severe regional drought in 2012 on postdrought (2013) aboveground net primary productivity (ANPP) in six central US grasslands. We predicted that (1) the magnitude of drought legacy effects measured in 2013 would be positively related to the sensitivity of ANPP to the 2012 drought, and (2) drought legacy effects would be negative (reducing 2013 ANPP relative to that expected given normal precipitation amounts). The magnitude of legacy effects measured in 2013 was strongly related (r2 = 0.88) to the sensitivity of ANPP to the 2012 drought across these six grasslands. However, contrary to expectations, positive legacy effects (greater than expected ANPP) were more commonly observed than negative legacy effects. Thus, while the sensitivity of ANPP to drought may be a useful predictor of the magnitude of legacy effects, short-term (1-year) severe droughts may cause legacy effects that are more variable than those observed after multiyear droughts.

1 aGriffin-Nolan, Robert, J.1 aCarroll, Charles, J. W.1 aDenton, Elsie, M.1 aJohnston, Melissa, K.1 aCollins, Scott., L.1 aSmith, M.D.1 aKnapp, Alan, K. uhttp://link.springer.com/10.1007/s11258-018-0813-7.pdf02073nas a2200157 4500008004100000245009900041210006900140300001400209490000800223520153700231100002201768700002301790700001601813700002001829856006601849 2017 eng d00aDrought timing differentially affects above- and belowground productivity in a mesic grassland0 aDrought timing differentially affects above and belowground prod a317 - 3280 v2183 a

Climate models forecast an intensification of the global hydrological cycle with droughts becoming more frequent and severe, and shifting to times when they have been historically uncommon. Droughts, or prolonged periods of precipitation deficiency, are characteristic of most temperate grasslands, yet few experiments have explored how variation in the seasonal timing of drought may impact ecosystem function. We investigated the response of above- and belowground net primary production (ANPP & BNPP) to altered drought timing in a mesic grassland in NE Kansas. Moderate drought treatments (25% reduction from the mean growing season precipitation [GSP]) were imposed by erecting rainout shelters in late spring (LSP), early summer (ESM), and mid-summer (MSM, n = 10 plots/treatment). These treatments were compared to two controls (long-term average GSP [LTA] and ambient GSP [AMB]) and a wet treatment (+30% of the long-term average GSP [WET]). We found that LSP drought did not significantly reduce ANPP relative to control plots while the ESM and MSM drought did despite equivalent reductions in soil moisture. In contrast, the WET treatment did not affect ANPP. Neither the WET nor the drought treatments altered BNPP as compared to the controls. Our results suggest that forecasts of ecosystem responses to climate change will be improved if both the seasonal timing of alterations in precipitation as well as differential responses of above- and belowground productivity to drought are incorporated into models.

1 aDenton, Elsie, M.1 aDietrich, John, D.1 aSmith, M.D.1 aKnapp, Alan, K. uhttps://link.springer.com/article/10.1007%2Fs11258-016-0690-x