Roadside Revegetation

PLANNING PHASE TWO: ASSESS SITE
are not inadvertently wasted. The more that local resources are used, the more
cost-effective, efficient, and effective the revegetation efforts may be. Physical
resources to inventory include topsoil, duff, litter, parent materials, woody
materials, logs, plant materials (seeds, seedlings, and cuttings), large rocks, and
water (seeps, springs, creeks). Intangibles should also be considered, such as
community cooperation and the local knowledge base.
5.11.1 TOPSOIL
One of the most important site resources for revegetation is topsoil. If considered
early in the planning process, topsoil can be salvaged and reapplied to disturbed
sites after construction. This is one of the best ways of increasing productivity
on a disturbed site (see Section 10.1.4, Topsoil).
Topsoil is inventoried early in the planning process to evaluate topsoil quality
and quantity, costs, and the feasibility of removal and storage. Topsoil recovery is an expensive
operation requiring knowledge of basic soil attributes. For this reason, it is a good idea to
conduct a soil survey or assessment of those locations that will be disturbed. An example of
soil and site information commonly collected for topsoil recovery is shown in Table 5-4. The
road in this example is planned through undisturbed forested lands. Soils data is collected
every 50 meters (at road stations) due to the high variability of the soils in this area. Where
soils are very uniform, distances between plots can be increased. Soil texture, rock fragments,
and depth of the topsoil are measured in the field. At selected intervals, or on different soil
types, a sample is collected for lab analysis.
During topsoil survey, other site attributes that could affect the quality of topsoil should be
noted, especially the locations of all noxious weeds. These weeds can be treated or removed
prior to topsoil salvage or the weed-infested areas can be avoided to prevent the spread these
weeds across the project area.
The outcome of the topsoil survey is a short report and map in the revegetation plan showing
the areas and depth to salvage topsoil. The report should discuss the fertility of the topsoil,
how it should be stored, and whether the duff and litter are removed and stored separately.
Areas should also be identified where topsoil should not be collected, such as areas of noxious
weeds or high rock. The volume of topsoil can be calculated based on soil depth and area of
the road prism.
Figure 5-73 | Creating
shredded wood for mulch
Woody material from road clearing can
be ground up into shredded wood and
used as a mulch or soil amendment.
5.11.2 DUFF AND LITTER
Duff and litter are the dead plant materials that have accumulated on the surface of the soil.
The level of decomposition differentiates litter from duff. Litter is the layer of recently fallen,
undecomposed leaves, needles, and branches; duff (which occurs immediately below the litter
layer) is litter that is decomposed beyond recognition. The duff layer is a dark, light-weight
organic layer. It is a large reserve of nutrients and carbon, and has a high water-hold capacity.
Litter and duff layers protect the soil from erosion by absorbing the energy of rainfall impact
and reducing overland flow. Combined, the litter and duff layers can be very thick, ranging
from 1 to 4 inches depending on the productivity and climate of the site.
Litter layers typically have viable seeds originating from the overstory vegetation. Under the
right conditions, these seeds will germinate. If collected, stored and reapplied correctly, this
natural seed bank can be used as a seed source. See Section 10.1.3.11, Litter and Duff, for a
discussion of methods for collection and application.
Litter and duff layers can be assessed at the same time that topsoil surveys are conducted by
measuring the depths at collection intervals using a ruler.
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
134