Data from: Evaluation of mowing frequency on right-of-way plant communities in Mississippi

Abstract: Native grasses and native wildflowers are declining, especially along roadside right-of-ways due to intensive mowing and herbicide management practices. Roadside right-of-ways undergo regular disturbances such as mowing, maintenance, and road developments that affect soils, groundwater, surface hydrology, and vegetation composition. We investigated species richness and percent coverage within plant communities along highway right-of-ways to determine if reduced mowing increased native plant coverage. The study was conducted using 10 research plots situated along Highway 25 in Oktibbeha and Winston counties, Mississippi. Each research plots consisted of three different treatments as follows: one that included greater than four mowings per year, one mowing only in fall, and one mowing only in fall with a supplemental native wildflower seeding. Using line transect sampling, we detected 277 plant species, which included native and non-native forbs, legumes, grasses, rushes, sedges, and woody perennials (vines, shrubs, and trees). Total percent coverage of native and non-native plants within different growth form categories did not differ among treatments (F2, 96 = 0.45, P = 0.83). However, coverage differed between uplands and lowlands (F1, 96 = 18.22, P {less than or equal to} 0.001), between years (F1, 96 = 14.54, P {less than or equal to} 0.001), between fall and spring seasons (F1, 96 = 16.25, P {less than or equal to} 0.001), and interacted between years and seasons (F1, 96 = 24.08, P {less than or equal to} 0.001) and seasons and elevations (F1, 96 = 5.00, P {less than or equal to} 0.001). Non-native agronomic grasses exhibited the greatest coverage ({greater than or equal to}90%) in all treatments. Percent coverage of each plant growth form was greatest in lowlands. Our research showed an increase of native grasses and wildflower species along roadsides with a reduced mowing regimen. We concluded that the timing and intensity of mowing for the duration of our study had little effect on the species composition of plant communities. However, one mowing per year retained agronomic plant coverage for erosion control and soil stabilization during roadside maintenance. Specific proactive management implementations can include native plantings, selective herbicide use to decrease non-native grasses, continual mowing from roadside edge to 10 meters (m), and only one mowing in late fall, but with an extension of the boundary to reach beyond 10 m from the roadside edge to suppress the invasion of woody plants, which could lead to lower long-term maintenance costs.摘要：原生草本与原生野生花卉种群正面临衰退，其中尤以因频繁刈割与除草剂管理措施影响的道路路域（roadside right-of-ways）最为显著。道路路域常受到各类常规干扰，包括刈割、养护作业与道路建设等，这些活动会对土壤、地下水、地表水文及植被组成造成影响。本研究针对高速公路路域的植物群落展开调查，统计其物种丰富度与盖度百分比，旨在探究降低刈割频率是否能提升原生植物的盖度。研究于美国密西西比州奥克蒂比哈县（Oktibbeha County）与温斯顿县（Winston County）的25号高速公路沿线设置10个样地开展，每个样地均设置3种不同的处理方式，具体如下：年刈割次数大于4次的处理、仅秋季刈割的处理，以及仅秋季刈割并辅以原生野生花卉补播的处理。本研究采用样线抽样法，共记录到277种植物，包括本土与外来的非禾本草本植物、豆科植物、草本植物、灯心草、莎草以及木本多年生植物（藤本、灌木与乔木）。不同生长型的本土与外来植物总盖度在各处理组间无显著差异（F₂,₉₆=0.45，P=0.83）。但植物盖度在高地与低地间（F₁,₉₆=18.22，P≤0.001）、不同年份间（F₁,₉₆=14.54，P≤0.001）、秋季与春季间（F₁,₉₆=16.25，P≤0.001）存在显著差异，且盖度在年份与季节的交互作用（F₁,₉₆=24.08，P≤0.001）以及季节与海拔的交互作用（F₁,₉₆=5.00，P≤0.001）下均表现出显著差异。在所有处理组中，外来农用草本植物的盖度最高，可达90%及以上。各类植物生长型的盖度均在低地达到最高值。本研究结果表明，通过降低刈割频率，道路沿线的原生草本与野生花卉种群数量有所提升。本研究得出结论：在研究周期内，刈割的时间与强度对植物群落的物种组成影响极小。但每年仅进行一次刈割，可在道路养护期间维持农用草本植物的盖度，从而起到水土保持与土壤固持的作用。具体的主动管理措施可包括：原生植物种植、选择性施用除草剂以减少外来草本植物、从道路边缘向10米范围内持续刈割，以及仅在晚秋进行一次刈割但将刈割边界延伸至道路边缘10米以外，以抑制木本植物的入侵，此举可降低长期养护成本。