The rapid increase of Poa pratensis L. (Kentucky bluegrass) on North Dakota grasslands during the past 30 yr has negatively impacted ecological services. Kentucky bluegrass grows earlier in the spring than many native grasses, which provides an opportunity to use targeted grazing to reduce Kentucky bluegrass and increase native grasses. A 5 year replicated study used 10 cow-calf pairs or pregnant cows to graze 3-ha paddocks in early to mid-May, early spring, (EARLY) until 30% of the native species were grazed. After 1 June, late spring−early summer, five cow-calf pairs were grazed on 3-ha paddocks (LATE) for twice as long as the EARLY treatment. Biomass was clipped inside and outside of cages after each grazing event and outside cages in the fall. In each paddock, a hundred 10-point frames were taken to determine percent native grass, Kentucky bluegrass, Bromus inermis Leyss. (smooth bromegrass), native forbs, and introduced forbs. After 5 yr, native grass abundance in the EARLY paddocks was 26% greater than in the LATE paddocks. Kentucky bluegrass abundance only differed the second year of the study when the EARLY paddocks had 32% less Kentucky bluegrass than the LATE paddocks. Total biomass was greater in the EARLY paddocks than LATE paddocks in year 2 of the study (886 ± 74 g m⁻² vs. 608 ± 28 g m⁻² for EARLY and LATE, respectively). Targeted grazing by cattle in early spring can increase native grass abundance and, depending on the year, decrease abundance of Kentucky bluegrass. Early spring targeted grazing should be used as a tool in adaptive management programs focusing on reduction of Kentucky bluegrass.

草地早熟禾的迅速增加在过去的30年中，北达科他州草原上的L.（肯塔基州蓝草）对生态服务产生了负面影响。春季肯德基草的生长要比许多本地草早，这提供了使用定向放牧减少肯塔基兰草和增加本地草的机会。一项为期5年的重复研究使用5对牛犊或怀孕的母牛在5月初至初春（早期）放牧了3公顷的牧场，直到30％的本地物种被放牧。6月1日（春末至初夏）后，在3公顷的牧场上放牧了5对小牛犊，放牧时间是早期处理的两倍。每次放牧事件发生后，生物质都会被夹在笼子的内部和外部，秋季则被固定在笼子的外部。在每个围场中，拍摄了100个10点帧，以确定原生草，肯塔基州早熟禾，无花布鲁姆氏菌。（光滑的无烟草），原生草和已引入的草。5年后，早期牧场的原生草丰度比LATE牧场高26％。肯塔基草丛的丰度仅与研究的第二年有所不同，当早期牧场的肯塔基草丛比LATE牧场少32％。在该研究的第二年中，EARLY牧场的总生物量大于LATE牧场（EARLY和LATE分别为886±74 g m ^-2 和608±28 gm ^-2）。早春有针对性地放牧牛群可以增加原生草的丰度，并视年份而定，降低肯塔基州早熟禾的丰度。在适应性管理计划中，应以早春为目标的放牧作为重点减少肯塔基草的适应性管理计划的工具。