Department of Geography and the Environment, University of North Texas, Denton, Texas, United States of America.
Department of Biology, University of Texas Arlington, Arlington, Texas, United States of America.
PLoS One. 2021 May 6;16(5):e0251089. doi: 10.1371/journal.pone.0251089. eCollection 2021.
Remnants of native tallgrass prairie experience elevated atmospheric nitrogen (N) deposition in urban areas, with potential effects on species traits that are important for N cycling and species composition. We quantified bulk (primarily wet) inorganic N (NH4+-N + NO3--N) deposition at six sites along an urban development gradient (6-64% urban) in the Dallas-Fort Worth metropolitan area from April 2014 to October 2015. In addition, we conducted a phytometer experiment with two common native prairie bunchgrass species--one well studied (Schizachyrium scoparium) and one little studied (Nasella leucotricha)--to investigate ambient N deposition effects on plant biomass and tissue quality. Bulk inorganic N deposition ranged from 6.1-9.9 kg ha-1 yr-1, peaked in spring, and did not vary consistently with proportion of urban land within 10 km of the sites. Total (wet + dry) inorganic N deposition estimated using bulk deposition measured in this study and modeled dry deposition was 12.9-18.2 kg ha-1 yr-1. Although the two plant species studied differ in photosynthetic pathway, biomass, and tissue N, they exhibited a maximum 2-3-fold and 2-4-fold increase in total biomass and total plant N, respectively, with 1.6-fold higher bulk N deposition. In addition, our findings indicate that while native prairie grasses may exhibit a positive biomass response to increased N deposition up to ~18 kg ha-1 yr-1, total inorganic N deposition is well above the estimated critical load for herbaceous plant species richness in the tallgrass prairie of the Great Plains ecoregion and thus may negatively affect these plant communities.
残余的本地高草草原在城市地区经历了升高的大气氮 (N) 沉积，这可能对氮循环和物种组成很重要的物种特征产生影响。我们在达拉斯-沃斯堡大都市区沿城市发展梯度 (6-64%城市) 的六个地点从 2014 年 4 月到 2015 年 10 月量化了批量 (主要是湿) 无机 N (NH4+-N + NO3--N) 沉积。此外，我们进行了一项与两种常见的本地草原丛生草种的植物指示剂实验——一种研究较多的 (Schizachyrium scoparium) 和一种研究较少的 (Nasella leucotricha)——以研究环境 N 沉积对植物生物量和组织质量的影响。批量无机 N 沉积范围为 6.1-9.9 kg ha-1 yr-1，在春季达到峰值，并且与距离站点 10 公里范围内的城市土地比例不一致。使用本研究中测量的批量沉积和模型化的干沉积估计的总 (湿+干) 无机 N 沉积为 12.9-18.2 kg ha-1 yr-1。尽管所研究的两种植物物种在光合作用途径、生物量和组织 N 方面存在差异，但它们的总生物量和总植物 N 分别增加了 2-3 倍和 2-4 倍，批量 N 沉积增加了 1.6 倍。此外，我们的研究结果表明，虽然本地草原草可能对增加的 N 沉积表现出正向的生物量响应，高达约 18 kg ha-1 yr-1，但总无机 N 沉积远远超过了大平原生态区高草草原草本植物物种丰富度的估计临界负荷，因此可能对这些植物群落产生负面影响。
