Water relations advantages for invasive Rubus armeniacus over two native ruderal congeners

Abstract

Despite species in the Rubus fruticosus complex (wild blackberry) being among the most invasive plants globally in regions with large annual fluctuations in water availability, little is known about their water relations. We compared water relations of a prominent member of the complex, R. armeniacus (Himalayan blackberry), with species native to the Pacific Northwest of North America (PNW), R. spectabilis (salmonberry) and R. parviflorus (thimbleberry). In eight stands of each species located near Portland, Oregon, USA, we measured mid-day hydraulic resistance (R plant ), and daily time series of stomatal conductance (g s ), leaf water potential (W lf ), and environmental conditions at four time periods spanning the 2007 growing season. Although all species maintained W lf above -0.5 MPa in spring, R. armeniacus maintained less negative W lf (C-1.0 MPa) than the natives in summer, a factor attributable to advantages in both its root and shoot systems. R plant of R. armeniacus was B0.1 MPa mmol -1 m 2 s for the duration of the study, and approximately 25-50% of R plant for the native species in summer. R. armeniacus had higher g s compared to the native species throughout the spring and summer, with approximately twice their rates in summer. Our R plant and g s results show that R. armeniacus has access to more water during PNW summers than congeneric natives, allowing it to maintain high water-use, and potentially helping it achieve higher growth and reproductive rates. Water relations may therefore be a critical component of the competitive and invasive success of R. armeniacus and other R. fruticosus species worldwide.

The Biology of Canadian Weeds. 154. Himalayan blackberry

“…The moisture regime of western British Columbia characteristically oscillates seasonally, with moist winter and spring conditions oscillating with dry summers. This is consistent with other Mediterranean climates invaded by the R. fruticosus L. aggregate such as the Pacific Northwest of North America, eastern Australia, Chile, northern Africa, and much of Europe (Jennings 1988;Amor et al 1998;Caplan and Yeakley 2010).…”

“…(1 m 2 s), a less negative water potential ( ](1.0 MPa) and a higher stomatal conductance at both high and low moisture conditions (Caplan and Yeakley 2010). Furthermore, when water supply was not limited, Himalayan blackberry showed higher growth rates than congeneric species in Oregon (Caplan and Yeakley 2013).…”

“…The excessive root system helps this species access moisture that other shrubs cannot; its large shoot system also enables it to store more water Yeakley 2010, 2013). These characteristics contribute to its rapid growth, giving it a competitive advantage (Caplan and Yeakley 2010). Himalayan blackberry bears fastgrowing thorny canes, which make its removal difficult and painful.…”

“…They can fix significantly more carbon than native congeners R. spectabilis and R. parviflorus especially in full sunlight, due to a higher light saturation point for photosynthesis (Barber 1976). Similarly, Himalayan blackberry can take up water and transpire it more rapidly than either R. spectabilis or R. parviflorus (Caplan and Yeakley 2010). The tolerance of Himalayan blackberry to dry and low nutrient status of soil is because it experiences less stress induced trade-offs than other plants Yeakley 2006, 2010).…”

Concealed diversity : taxonomical, phytogeographical and phytosociological notes on brambles (Rubus L. subgen. Rubus) in north-west Europe

“…This species is indigenous in the Caucasus and introduced in central Europe around 1800 . Rubus armeniacus (sometimes referred to as R. praecox, which is a different species) is worldwide considered an invasive species, threatening natural ecosystems in several temperate regions (Caplan & Yeakley 2006;Pfeiffer & Ortiz 2007;Astley 2010;Caplan & Yeakley 2010;Richardson & Rejmánek 2011;Clark et al 2013). Figure 8.3 shows the distribution of this species in the Netherlands in the map grid cells where other Rubus species are lacking.…”