Cutting diameter on early growth performance of purple willow (Salix purpurea L.)

Abstract

Cuttings are a common soil and water bioengineering technique used for slope stabilization and erosion control along rivers. Above- and belowground growth of cuttings, especially immediately after installation, have a strong impact on the protective performance. To assess the effects of diameter on the early growth performance of purple willow (Salix purpurea L.), freshly harvested (nondormant) cuttings of different diameters (5 to 24 mm) were planted as part of an outdoor raised-bed experiment from March to October of 2010. The aim of this study was to investigate the growth performance of purple willow cuttings and to gain deeper insight into the plant's development during the first growth stage (six months). After two months of growth, 99% of the cuttings sprouted, and the diameter had no statistically significant impact on the sprouting performance of the cuttings. During the first four months, aboveground biomass production (M_ag) was 5.7 and 4.4 (after two and four months, respectively) times higher than belowground biomass (M_bg). However, after six months, M_ag and M_bg were balanced. The diameter of the cuttings had a significant impact on biomass development at all of the time steps. The cuttings of the diameter class C (15 to 19 mm) produced the most M_ag and M_bg, with 33% and 34% of total M_ag and M_bg of all diameter classes after six months. Four months after planting, at least 80%, and after six months at least 90%, of the M_bg was allocated in the lowermost third of the cuttings. The observations showed high M_ag production for the entire period; M_bg production was relatively low during the first four months, which resulted in a diminished protective function of the roots until this specific point of development.