1. Building 006, BARC-W, Beltsville, Maryland 20705 (A.A.B., A.M., D.L.K.)
2. Department of Natural Resource Science and Landscape Architecture, University of Maryland, College Park, Maryland 20742 (A.A.B.)
3. Botanisches Institut der Universität, Menzinger Strasse 67, D-80638 Munich, Germany (A.M., J.E.)
4. USDA-ARS, Eastern Regional Research Center, Wyndmoor, Pennsylvania 19038 (P.E.P., A.H.)
5. Universität Bayreuth, D-95447 Bayreuth, Germany (C.K., N.S.)