Rubus armeniacus (Himalayan blackberry) Occurrence and Growth in Relation to Soil and Light Conditions in Western Oregon

Abstract

Rubus armeniacus (Himalayan blackberry) is an invasive plant in disturbed habitats in the Pacific Northwest. At 41 sites domi - nated by R. armeniacus, we measured stand height, mean floricane length, canopy cover, slope, aspect, and soil properties (color, NO 3 +NO 2 -N, organic matter, particle size distribution, and pH). For several soil properties we compared our data to National Resource Conservation Service soil survey data for the soils near our sites. R. armeniacus occurred in soils that contained more sand (by 25.6%, P < 0.001), less silt (by �.4%, P = 0.03) and less clay (by 13.4%, P < 0.001) than this non-biased, random sample of western Oregon soils. Ln(stand height) was significantly related to canopy cover (R 2 = 0.44, P < 0.001) and floricane length was significantly related to gravel (R 2 = 0.11, P = 0.03). Our results suggest that shade was a primary environmental determinant of R. armeniacus occurrence and growth. Our results further suggest that R. armeniacus is tolerant of a wide range of soil conditions, notably coarse texture. An ability to withstand soils with low water content or low nutrient availability with only a small reduction in growth may explain R. armeniacus occurrence on more coarse-textured substrates than are typical for western Oregon soils. In combination with its adaptation to high light availability conditions, this factor may help explain the frequent occurrence of R. armeniacus in anthropogenically disturbed habitats.