M. Francesca Catrufo Jill Baron Katherine S. Rocci 2023 <div id="Abs1-section" class="c-article-section"><div id="Abs1-content" class="c-article-section__content"><p>Vehicles are an important source for N deposition that may negatively impact roadside ecosystems. While elevated roadside N deposition has been found in many locations, it is not yet known if vehicle emissions cause measurable increases of N deposition in complex, mountainous terrain adjacent to roads. To address this, this study investigated the effect of vehicle N emissions on throughfall (through trees) and open N deposition in a high traffic corridor in mountainous terrain of Rocky Mountain National Park, Colorado, USA. We measured bulk (wet + dry) atmospheric N deposition in throughfall and open samplers along two transects of 750 (throughfall) and 225 (open) m moving away from the road using ion exchange resin (IER) collectors. Contrary to most studies of roadside N deposition, we found no influence of road proximity on inorganic N deposition in throughfall or open sites, possibly due to terrain complexity. Interactions with vegetation modified regional N deposition; throughfall sites had 69% higher nitrate (NO₃⁻) deposition&nbsp;than open sites and larger trees were associated with higher ammonium (NH₄⁺) deposition&nbsp;as compared to smaller trees. When comparing to regional sites that are&nbsp;part of national monitoring networks, we confirmed that our estimates were unaffected by vehicle emissions as our throughfall IER collectors had similar total inorganic N deposition as wet + dry deposition from regional sites (8.64–13.56 vs 10.72–12.14&nbsp;g N ha⁻¹&nbsp;day⁻¹, respectively). These findings do not negate vehicles as a local source of N emissions but suggest elevated N deposition adjacent to busy roads cannot be assumed for complex terrains.&nbsp;Instead, environmental variables may be more important drivers than proximity to roads in topographically complex ecosystems.</p></div></div> application/pdf 10.1007/s11270-023-06762-2 en Springer Proximity to roads does not modify inorganic nitrogen deposition in a topographically complex, high traffic, subalpine forest article