Roadside Revegetation

IMPLEMENTATION GUIDES
Table 10.11 | Nitrogen- fixing bacteria and their plants
Host Plants
Nitrogen-Fixing Bacteria
Family
Subfamily
% Nitrogen Fixing Plants Common Plant Species
Rhizobium spp. Legume Caesalpinioideae 23 Redbud, honeylocust
Legume Mimosoideae 90 Mesquite, acacia
Legume Papilionoideae 97 Lupine, milkvetch, black
locust, clover
Family
Common Plant Species
Frankia spp. Birch Alder, birch
Oleaster
Myrtle
Buckthorn
Rose
Silverberry, buffaloberry
Myrtle
Cascara, snowbrush, deerbrush
Mountain mahogany, cliffrose, bitterbrush
Uses for Nitrogen-Fixing Plants in Revegetation
Only a fraction of native species are nitrogen-fixing host plants. In the western United States,
the most common are the lupines, vetch, bitterbrush, ceanothus, alder, and wax myrtle (Table
10-11). On nitrogen-poor sites, sowing or planting a higher proportion of these species can
help a site to recover nitrogen fertility and organic matter (Figure 10-40A). The amount of
nitrogen that will be fixed on a site is related to the area of vegetative cover in nitrogen fixing
host plants, the productivity of the plants, and factors such as temperature and moisture. If
percent cover of nitrogen fixing host plants is low, then the amount of nitrogen supplied to
the site will be correspondingly low (Figure 10-40B). Likewise, dry or cold conditions tend to
result in slower accumulation of nitrogen. While many native and introduced nitrogen fixing
plants are attractive to pollinators, they are also attractive forage for large herbivours. This
should be considered during the design of roadside plant communities.
A
Nitrogen Fixed (lbs/ac/yr)
B
20
15
C. velutinus
10
P. tridentata
5
0
0 20 40 60
Canopy Cover (%)
Figure 10-40 | Amount of
nitrogen is related to the cover
of nitrogen-fixing plants
The accumulation of nitrogen by N-fixating
bacteria is directly related to the cover of
nitrogen-fixing host plants on a site. The
large plants shown in this photograph are
lupines, which are nitrogen-fixing (A). The
nitrogen-fixing potential of 15-year-old stands
of Ceanothus velutinus and Purshia tridentata
was directly proportional to plant cover (B)
(adapted after Busse 2000).
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
275