Effects of Rock Climbing on Cliff Goldenrod (Solidago sciaphila Steele) in Northwest Illinois

Abstract

-Solidago sciaphila is an endemic goldenrod, restricted to dolomite or sandstone cliffs in and near the driftless region of the upper Midwest. A demographic study of 544 genets on currently climbed, previously climbed and unclimbed dolomitic cliffs in NW Illinois indicated that position on the cliff face was the most significant factor affecting growth. Seventy percent of all plants grew within 3 m of the cliff top, an area that comprised only 18% of the cliff face. Within the upper cliff zone, rock climbing significantly reduced Solidago density. Cliffs that were actively climbed had few genets in the upper 3 m, averaging 3.2/M2, while unclimbed cliffs and cliffs not climbed for 2 yr supported 14.2/M2 and 12.0/ i2, respectively. Basal area/M2 and flowering ramet production/m2 were significantly lower, and inflorescence length nonsignificantly lower, on currently climbed cliffs, due to the lower genet density. In the lower cliff zone (>3 m from the top) genet density was low (0.2-2.1/ m2) on all cliffs, regardless of climbing intensity. On climbed cliffs > 50% of flowering ramets were broken, significantly more than the 15% broken on unclimbed cliffs. Broken flowering ramets produced 22% of total inflorescence length on the currently climbed cliffs (compared to <5% on unclimbed and previously climbed cliffs), resulting in total inflorescence production statistically similar to, but lower than, that on unclimbed and previously climbed cliffs. Two years after cessation of climbing, Solidago in the upper zone of the previously climbed cliffs had similarly high density, basal area, ramet production and inflorescence production as on unclimbed cliffs. Climbing appeared to skew the population structure, favoring survival of large flowering genets and inhibiting survival of smaller nonflowering genets. This difference largely disappeared on cliffs unclimbed for 2 yr. To protect Solidago sciaphila, it is necessary to protect the entire cliff face, with highest priority given to the upper 3 m.