/ Effectiveness of Hand-Pulling the Invasive Mossy Stonecrop (Sedum Acre L.) From Alvar Pavements
ï~~2000 THE MICHIGAN BOTANIST 43 EFFECTIVENESS OF HAND-PULLING THE INVASIVE MOSSY STONECROP (SEDUM ACRE L.) FROM ALVAR PAVEMENTS Judith Jones Winter Spider Eco-Consulting, R.R. #1, Sheguiandah, Ontario POP 1WO (705) 368-0734 <j2@j2.nu> ABSTRACT The Eurasian weed mossy stonecrop (Sedum acre L.), a tiny succulent plant of the Crassulaceae, is present on some alvar pavements on Manitoulin Island, Ontario. This study examined the rate of spread of mossy stonecrop on alvar pavement, and tested whether hand removal of stonecrop would eradicate the weed or possibly cause an increase in regrowth of it or other weeds. The study also looked at regrowth of mossy stonecrop in situ from fragments. Nine 1 x 1 m plots were given three different treatments: no pulling; careless pulling leaving fragments; very careful pulling leaving no fragments. Plots were observed for three growing seasons after treatment. Results show stonecrop is capable of rapid, aggressive growth, but that this does not always occur. Stonecrops do regrow from fragments or possibly from root remnants. Careful pulling techniques resulted in almost no stonecrop regrowth after three growing seasons. No regrowth of other weed species occurred. INTRODUCTION Mossy stonecrop (Sedum acre L.), a common Eurasian weed, is a fibrousrooted, much-branched perennial with stems 5-10 cm long and succulent leaves of 2-5 mm (Cronquist 1991). The plants are mat-forming in habit, with a few centimeters at the tip of each creeping stem becoming upright and fleshy (Figure 1). The upright stems support terminal, small, yellow flowers and eventually dry capsular fruits. The plant has been cultivated in many forms and is widely naturalized throughout North America (Voss 1985). On Manitoulin Island, Ontario, mossy stonecrop is a common weed of pastures and open areas of shallow soil over flat limestone bedrock. In fact, the plant is able to grow on the surface of bare limestone in small patches of soil less than 1 cm deep (personal observation). Because it can tolerate such conditions, mossy stonecrop finds suitable habitat in rare alvar communities. Alvars are open, treeless ecosystems based on horizontal limestone bedrock. The vegetation is usually dominated by graminoid herbs or dwarf shrubs. Soil cover is shallow and sporadic, making these ecosystems fragile end easily disturbed by soil displacement. Recent work has brought attention to the rarity of different alvar community types as well as to the high incidence of rare species present on alvars (Brownell & Riley 2000; Reschke et al. 1999; Catling 1995; Catling & Brownell 1995). Efforts to protect high quality examples of alvar require long-term management strategies that include plans to cope with threats. Thus, questions have been
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