Semiarid grasslands of the Nebraska Sandhills provide critical ecosystem services and are an important forage resource for the local cattle industry. Over the past decades, warming and climate-related extremes have affected grassland production worldwide, which promotes the initiation of numerous grassland monitoring projects. Despite this, production trends for plant functional groups in the Sandhills regions in recent years have remained unknown. In this study, we analyzed plant biomass production of the Sandhills grasslands with a dataset collected over 15 yr from 2007 to 2021. Ungrazed total biomass and biomass of individual plant functional groups were assessed in grazing exclosures twice a year, in mid-June (for early season) and mid-August (for late season). This first paper reports our findings on total biomass and compositional changes of the three major plant functional groups, as well as trends in precipitation and temperature during the study period. A significant increasing trend ( < 0.05) was observed in temperature over time during the early season (April to mid-June), with a weak monotonic increasing trend ( = 0.07) during the full season (April to mid-August), whereas no significant pattern was reported for precipitation during the study, although it displayed complex within- and across-season patterns. The proportion of C-grass biomass in total biomass increased ( < 0.05), while the proportion of C-grass biomass decreased ( < 0.01). We did not observe any significant trends for forbs; however, the drought of 2012 resulted in up to a fivefold increase in the proportion of forb biomass the following year. These findings enhance our understanding of current patterns in grassland production and contribute to regional evidence on the response of plant functional groups to variability and extremes in intra-annual weather variables, which can improve our capability to perform adaptive grazing management in a similar semiarid grassland ecosystem.

中文翻译：

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半干旱内布拉斯加州沙丘草原 15 年生物质生产：第 1 部分 - 植物功能组分析

内布拉斯加州沙丘的半干旱草原提供了重要的生态系统服务，也是当地养牛业的重要饲料资源。过去几十年来，变暖和与气候相关的极端事件影响了全世界的草地生产，这促使众多草地监测项目的启动。尽管如此，近年来沙丘地区植物功能群的生产趋势仍然未知。在这项研究中，我们利用 2007 年至 2021 年 15 年间收集的数据集分析了 Sandhills 草原的植物生物量生产。每年两次在 6 月中旬（对于早季）和八月中旬（晚季）。第一篇论文报告了我们对三个主要植物功能群的总生物量和组成变化的发现，以及研究期间降水和温度的趋势。早季（4月至6月中旬）气温随时间变化呈显着上升趋势（<0.05），全季（4月至8月中旬）呈弱单调上升趋势（=0.07），而无研究期间报告了降水的显着模式，尽管它显示出复杂的季节内和跨季节模式。丙草生物量占总生物量的比例增加（ < 0.05），而丙草生物量比例下降（ < 0.01）。我们没有观察到福布的任何显着趋势；然而，2012年的干旱导致次年的禾本科生物量比例增加了五倍。这些发现增强了我们对当前草原生产模式的理解，并为植物功能群对年内天气变量的变异性和极端性的响应提供了区域证据，这可以提高我们在类似的半干旱草原生态系统中进行适应性放牧管理的能力。