ISHS Acta Horticulturae 630: XXVI International Horticultural Congress: Nursery Crops; Development, Evaluation, Production and Use
ADAPTATION EVALUATED: CASE STUDIES OF UNDERUSED TREES AND SHRUBS |
| Author: | W.R. Graves |
| Keywords: | drought, flooding, salinity, cold hardiness, nitrogen fixation |
| Abstract:
Many promising woody plants have not been evaluated for their capacity to thrive in managed landscapes, where environmental conditions restrict diversity to a limited number of adapted taxa. My colleagues and I assess the horticultural potential of obscure or rare taxa native to habitats that require resistance to stressors common in managed landscapes. Research related to several taxa will be considered with a primary focus on our evaluation of Alnus maritima [Marsh.] Nutt. (seaside alder). This rare species occurs in only three small, disjunct provenances (part of the Delmarva Peninsula, one swamp in northwestern Georgia, and two counties in southern Oklahoma) in USDA hardiness zone 7. Plants in all provenances grow exclusively in saturated soils, and some individuals on the Delmarva Peninsula occur in estuaries and in wetlands near salt water. While its ecological niche indicates seaside alder would perform well in flood-prone managed landscapes where winters are relatively mild, we questioned how drought, low temperatures, and salt would affect the species and whether provenance differences in resistance to these stressors exist. Results under greenhouse and field conditions demonstrated drought tolerance; although gas exchange was affected, all leaves were sustained without apparent damage as plants recovered from water deficits that caused severe wilting. Twigs sampled at five-week intervals between late September and late April from plants of all provenances in native habitats and in a plantation near the border of USDA zones 4b and 5a were far more hardy than necessary for a species restricted to USDA zone 7. Field trials confirmed whole plants survive winters in Iowa and Minnesota. Resistance to root-zone salt was intermediate to that of other woody species and was similar among provenances. These data provide an example of how adaptation to multiple environmental stressors can be evaluated as part of a coordinated program to conserve and commercialize a rare species. | |
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