Physiological Responses of Himalayan Blackberry (Rubus armeniacus Focke) to Flooding and Implications for Wetland Restoration in the Pacific Northwest

Abstract

Himalayan blackberry (Rubus armeniacus Focke) is a common invader of anthropogenically disturbed wetlands in the Pacific Northwest. Understanding of the plant's physiological response to inundation and associated anoxic conditions is necessary to correctly restore and direct R. armeniacus-infested wetlands towards autogenic repair. In a greenhouse experiment, R. armeniacus was subjected to partial and complete inundation, as well as treatments involving shading and/or clipping of above-ground biomass. Results indicate that R. armeniacus is highly tolerant of anoxic conditions and can induce morphological changes in its roots and stems to tolerate long periods of anaerobic respiration or facilitate gas exchange. Flooding was the most powerful influence on plant health, with cutting treatments increasing mortality rates. In some treatment combinations, shade improved plant health, but the harshest combination of shade, cutting, and flooding proved most stressful. Fully submerged plants were able to survive more than 40 days underwater in laboratory conditions, and initiated rapid shoot growth after two weeks of submergence. This information will better inform restorers as to what kinds of site planning or pre-treatments are required before restoring R. armeniacus-infested wetlands.