PARENT SESSION
Poster Session # 16: Invasive Species.

Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Rubus discolor vigor under varying photic and edaphic conditions in western Oregon.

Caplan, J.^*,1, Yeakley, J.¹, ¹ Environmental Science, Portland, OR, USA

ABSTRACT- Rubus discolor (Himalayan blackberry) is a major plant invader of anthropogenically disturbed habitats in the Pacific Northwest. This study used an elevation gradient from the Willamette Valley to the western Cascade Range in Oregon to assess R. discolor vigor in a wide range of photic and edaphic conditions. We measured two indicators of patch vigor, mean floricane cane length and patch height, at 41 R. discolor patches along the gradient. We measured canopy cover, slope, aspect, as well as soil particle size distribution, color, moisture, organic matter, pH, Eh, and NO₃+NO₂-N. Linear regression revealed patch height varied most strongly with canopy cover (R²=0.37, p<0.01). Cane lengths were longer at sites with the highest organic matter and soil moisture content, but shorter at sites with the highest Hurst color rating. Patches were taller at sites with the least canopy cover, slope, sand content, and elevation, but shorter at sites with the highest silt content. We attribute superior vigor in patches with low canopy coverage to increased light availability at those sites, while we attribute diminished vigor in sites with low organic matter, silt, or soil moisture, and high gravel, sand, and Hurst color to limitation from moisture availability and low soil fertility. The growth response to increased light availability suggests light is the predominant limiting resource to R. discolor vigor in anthropogenically disturbed habitats.

Key words: human impacts, terrestrial ecology, disturbance, invasive plants