Data from: Comparative water use by maize, perennial crops, restored prairie, and poplar trees in the US Midwest

Water use by plant communities across years of varying water availability indicates how terrestrial water balances will respond to climate change and variability as well as to land cover change. Perennial biofuel crops, likely grown mainly on marginal lands of limited water availability, provide an example of a potentially extensive future land cover conversion. We measured growing-season evapotranspiration (ET) based on daily changes in soil profile water contents in five perennial systems—switchgrass, miscanthus, native grasses, restored prairie, and hybrid poplar—and in annual maize (corn) in a temperate humid climate (Michigan, USA). Three study years (2010, 2011 and 2013) had normal growing-season rainfall (480–610 mm) whereas 2012 was a drought year (210 mm). Over all four years, mean (±SEM) growing-season ET for perennial systems did not greatly differ from corn (496 ± 21 mm), averaging 559 (±14), 458 (±31), 573 (±37), 519 (±30), and 492 (±58) mm for switchgrass, miscanthus, native grasses, prairie, and poplar, respectively. Differences in biomass production largely determined variation in water use efficiency (WUE). Miscanthus had the highest WUE in both normal and drought years (52–67 and 43 kg dry biomass ha−1 mm−1, respectively), followed by maize (40–59 and 29 kg ha−1 mm−1); the native grasses and prairie were lower and poplar was intermediate. That measured water use by perennial systems was similar to maize across normal and drought years contrasts with earlier modeling studies and suggests that rain-fed perennial biomass crops in this climate have little impact on landscape water balances, whether replacing rain-fed maize on arable lands or successional vegetation on marginal lands. Results also suggest that crop ET rates, and thus groundwater recharge, streamflow, and lake levels, may be less sensitive to climate change than has been assumed.不同降水年份下植物群落的水分利用特征，可揭示陆地水平衡如何响应气候变化、气候变异性以及土地覆盖变化。多年生生物燃料作物（多主要种植于水资源受限的边际土地）即为未来可能大规模发生的土地覆盖转换的典型案例。本研究基于土壤剖面含水量的日变化，对美国密歇根州温带湿润气候区的5种多年生种植系统——柳枝稷（switchgrass）、芒草（miscanthus）、本土草本植物、恢复草原以及杂交杨树（hybrid poplar），和一年生玉米（maize，又称corn）的生长季蒸散量（evapotranspiration, ET）进行了测定。本研究的3个年份（2010、2011和2013年）生长季降雨量处于正常水平（480–610 mm），而2012年为干旱年份（降雨量仅210 mm）。四年间，各多年生系统的生长季平均蒸散量（±标准误，standard error of the mean, SEM）与玉米（496 ± 21 mm）并无显著差异：柳枝稷、芒草、本土草本植物、恢复草原以及杂交杨树的平均蒸散量分别为559（±14）、458（±31）、573（±37）、519（±30）和492（±58）mm。生物量生产的差异在很大程度上决定了水分利用效率（water use efficiency, WUE）的变化。无论正常年份还是干旱年份，芒草的水分利用效率均为最高（分别为52–67和43 kg 干生物量·hm⁻²·mm⁻¹），其次为玉米（40–59和29 kg·hm⁻²·mm⁻¹）；本土草本植物与恢复草原的水分利用效率较低，杂交杨树则处于中等水平。与此前的模型模拟研究不同，本研究测得的多年生系统水分利用情况在正常和干旱年份均与玉米相近，这表明在该气候区，雨养多年生生物质作物无论替代耕地的雨养玉米，还是边际土地的演替植被，对景观水平衡的影响都极小。研究结果同时表明，作物蒸散速率及其关联的地下水补给、径流量与湖泊水位，可能比此前所假设的对气候变化更不敏感。