Using willow microcuttings for ecological restoration: An alternative method for establishing dense plantations

This experimental study presents an innovative method for establishing a willow (Salix spp.) shrub vegetation cover on disturbed sites in North America. Willow microcuttings of Salix miyabeana ‘SX61’, S. eriocephala ‘S25’ and S. purpurea ‘Fish Creek’ were selected to test the potential of shortened willow cuttings. We evaluated the effect of three factors related to microcutting assemblages (monoculture and polyculture), the presence or absence of a companion herbaceous plant and two types of substrate (same soil, but one with compost and one without). The objectives were to assess 1) the potential growth of willow microcuttings in open site conditions, 2) the influence of soil amendments on the establishment of willow microcuttings and 3) the influence of diversity on biotic resistance. The results showed a greater establishment rate, stem height and number of shoots per microcutting without the presence of an herbaceous plant. The plots planted without compost showed better establishment rates, especially those in the polyculture plots. The presence of compost increased the production of number of shoots per microcutting and tended to increase stem height. The presence of an herbaceous plant was related to higher plant cover, but no relationship with biotic resistance was observed. Although willow cover did not significantly affect relative growth of undesirable tree species seedlings (Betula populifolia and Acer rubrum), we observed that plant cover tended to reduce the relative growth rate. Consequently, this preliminary test of using microcuttings as an alternative approach to establishing a dense shrub cover showed good potential to restore disturbed sites and limit tree encroachment in open sites, reducing environmental and economic costs.