American graffiti: Spatial distribution and ecological consequences of aspen arborglyphs

• Aspen with arborglyphs had 19% greater diameter growth relative to unmarked aspen. • 75% of arborglyphs were within 20 m of the trail. • Aspen with arborglyphs had twice as large diameter as unmarked aspen. • There was no increased risk of 10-year mortality in aspen with arborglyphs. • Arborglyphs are preferentially carved on large, fast-growing aspen. Aspen ( Populus tremuloides Michaux) is perhaps the most iconic tree species of the American West. The thin, white bark of aspen has long been a canvas for aspiring artists and those seeking to leave a mark on the wilderness. However, a question arises as to whether these carvings – or “arborglyphs” – damage aspen and either reduce growth or increase mortality. Here we leveraged a long-term, spatially mapped forest demography plot in Utah, USA, to investigate the spatial distribution of aspen arborglyphs in proximity to a trail and to assess differences in survival and growth between marked and unmarked trees. Arborglyphs overwhelmingly (77%) consisted of names, initials, and dates, with the oldest arborglyph dating from 1887. We found that 75% of arborglyphs were within 20 m of the trail, primarily occurring on aspen of ≥ 20 cm diameter at breast height. Surprisingly, aspen with arborglyphs had 24% higher annual basal area increment and had no evidence of increased ten-year mortality rates, relative to aspen without arborglyphs. Cumulatively, our results suggest that individuals carving arborglyphs seek aspen canvases that are near the trail, have large diameter, and appear vigorous, which may explain why marked aspen had greater growth than unmarked aspen. Though we found no evidence in our study for a negative impact of arborglyphs on aspen, we caution that the creation of new arborglyphs likely poses a risk of injury and mortality to aspen over longer timescales.