Environmental Engineering Reference
In-Depth Information
Suter 2003; Seiwa et al. 2008). However, microbial associations can contribute to the establishment
and survival of willows in challenging environments. Species of
Salix
are among the few genera
that can form mycorrhizal associations with ectomycorrhizal and endomycorrhizal species (van
der Heijden 2001). There is also recent and exciting evidence of willow stem endophytes that may
contribute to phytoremediation and/or nitrogen assimilation through nitrogen fixation (Doty 2008;
Doty et al. 2009).
Members of the genus
Salix
are important for riparian ecology, providing habitat and forage for
numerous species. In North America, willows are a particularly important food source for native
beaver, elk, and moose, among others (Peinetti 2002, Peinetti et al. 2001; Baker et al. 2005; Veraart
et al. 2006). Shrub habitat tends to be underrepresented in the northern tier of the United States
because much shrub land has been developed or converted to agricultural use. Expanded cultivation
of shrub willows as a bioenergy crop would increase the proportion of shrub land on the landscape
and provide additional habitat for migratory song birds (Dhondt et al. 2007). On occasion, willow
plantings have been used to provide fodder for grazing cattle, sheep, and goats, providing some
notable nutritional benefits, especially during dry periods when pasture is not available (Moore
et al. 2003; McWilliam et al. 2005; Pitta et al. 2007; Lira et al. 2008).
28.3 hIstorIcal cultIvatIon oF WIlloW
Willows have a long history of utility to society in a wide range of applications. Willow bark was the
original source of the nonsteroidal anti-inflammatory drug, aspirin (acetylsalicylic acid) (Levesque
and Lafont 2000). Historically, willow was used for medicinal purposes by indigenous cultures and
immigrants to North American before the development of modern medicines. Even today, among
the diversity of the genus
Salix
there is great potential to identify other secondary compounds
with pharmaceutical activity (Hostanska et al. 2007; Nahrstedt et al. 2007). In Europe especially,
willows have been used extensively for making woven baskets, furniture, and decorative structures.
This craft was brought to North America, together with planting stock of European basket willow
varieties, by immigrants in the mid- to late-1800s. The industrial production of willow baskets was
considerable in the late nineteenth and early twentieth century in upstate New York, centered in
Liverpool, where hundreds of thousands of baskets were woven in the early twentieth century. The
commercial production and trade in willow baskets declined with the development and distribution
of wicker and other cheaper materials, but the craft persists to produce baskets largely for decorative
use, particularly in the United Kingdom and in the city of Chimbarongo in Chilé. White willow
(
S. alba
) provides the wood used to make cricket bats. Willow has great religious significance as
one of the species used in the Jewish holiday of Sukkot and in the Polish and Polish-American
celebration of Dyngus Day on the Monday after Easter.
Willows have enjoyed widespread cultivation in landscaping and ornamental settings. Weeping
willow (
S. babylonica
) and white willow (
S. alba
) have been particularly popular as an attractive
landscaping and shade tree that can tolerate a wide range of climates and especially wet soils
(Newsholme 1992). In recent years, a variegated variety of the shrub willow species,
S. integra
,
named “Hakuro Nishiki” has become popular in landscaping applications in the northeastern
United States. Shrub willow species have been planted and woven to form hedges or living fences,
sometimes called fedges. This practice has been further adapted to produce living sound barriers
along highways, called “living walls” (Figure 28.2). Many of these have been planted using
S. viminalis
and
S. miyabeana
along highways in and around Montréal in the province of Québec,
Canada. A few rows of shrub willow planted adjacent to roads and highways also serve well in
trapping blowing and drifting snow, functioning as living snow fences.
More recently, willow has been applied in systems for environmental or ecological engineering.
Willow plantations have been successfully implemented for the uptake and control of nutrient
effluents, particularly nitrogen and phosphorus, from wastewater treatment systems, from non-
point-source agricultural nutrient runoff, or from landfill leachate (Pulford et al. 2002; Adegbidi
