Abstract

Cardamine diphylla (Crinkleroot) is a common wintergreen found in scattered colonies across mesic forests of North America. It is known for high levels of glucosinolates, which are important anti-herbivore compounds characteristic of Brassicaceae. Crinkleroot displays varying color morphotypes of green and purple on the abaxial and adaxial sides of the basal leaves. Unlike many forest floor herbs, C. diphylla grows both under Rhododendron (Rhododendron maximum L.) thickets and on the open forest floor. The aim of this study was to investigate whether Rhododendron affects soils and foliar characteristics of C. diphylla. Our study was conducted in a rich cove forest in Pisgah National Forest near Barnardsville, NC. Twenty patches of C. diphylla growing under Rhododendron were compared with twenty patches in the open forest. The frequency of green or purple abaxial color on the basal leaves was recorded, and leaf and soil samples were collected for analysis. Foliar samples were analyzed for nitrogen and sulfur content, and soil samples were analyzed for total nitrogen, pH, humic matter, and cation exchange capacity. Cardamine diphylla growing under Rhododendron displayed significantly higher nitrogen and sulfur content, lower biomass, and were more likely to have green abaxial surfaces compared to C. diphylla growing in the open forest. Soils under Rhododendron had significantly lower nitrogen and humic matter. These results indicate that Rhododendron does impact soils and the foliar characteristics of this wintergreen perennial. Transplant studies would offer insight on how C. diphylla is able to tolerate varying overstory environments.

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