Revegetation Guidelines for Western Montana - Global Restoration ...

layer of topsoil, spread to this thickness, was sufficient for the establishment and continued
productivity of vegetation at a northwest Colorado mine site. Deeper topsoil depths (12, 18, and 24
inches) were found to be associated with a plant community that was dominated by grasses, while
the shallow topsoil depths supported plant communities that were more diverse and had significantly
greater forb production and shrub density.
A topsoil salvage operation is recommended, along with integrated roadside vegetation
management, for long-term roadside revegetation success (See Appendix B). Biologically inactive
and nutrient-poor construction fill materials predicate topsoil addition to serve as a source of
nutrients and mycorrhizal inoculum to ensure long-term revegetation success.
Step 5 – Site preparation
Soil compacted sites
Soil is comprised of organic material, air spaces, and different sized clumps and particles of sand, silt,
and clay. A loss of soil structure, such as from compaction, excessive
tillage, or tillage when soil is too wet, negatively affects soil processes.
Soil compaction reduces the ability of water to percolate through the
soil and reduces the movement of soil air exchange between plant
roots and the air spaces within the soil.
Broadcast seed will sit on
top of compacted soil and
be vulnerable to wind,
water, heat, and predation
To improve soil structure and prepare a proper seedbed for adequate seed safe sites, seriously
compacted sites should be scarified or plowed. (When invasive weeds are present, avoid deep
tillage as this action releases nutrients favorable to weed colonization). Scarification is a form of
ripping and consists of breaking up the topsoil aggregates by raking the soil surface with ripper
shanks, typically pulled behind a tractor, grader, or bulldozer. In sites where the topsoil has been
removed, ripping subsoils to a depth of 6 to 12 inches prior to providing topsoil is recommended.
Seedbed preparation
The necessity of seedbed preparation depends on the seeding method (Step 9 – Determine Seeding
Method), influenced by site accessibility and terrain and seedbed characteristics. Seedbed
preparation is usually not necessary when drill seeding, but is strongly recommended when
broadcast seeding or hay mulch seeding. Generally, an ideal seedbed is firm enough so the seed
will be in contact with the soil, and the soil will not be easily washed or blown away and loose
enough for the seed to sprout and penetrate the soil. A seedbed can be produced through shallow
plowing, harrowing, or dragging small chains. Ash following a fire can also provide an excellent
seedbed. An ideal seedbed includes adequate seed safe sites.
Plowing loosens the upper layer of soil, increasing the number of seed safe sites and facilitating
seedling germination and root extension. Plowing should be carefully considered as it will
permanently damage any desired vegetation and can facilitate erosion when performed on slopes or
fine textured soils. Always avoid deep plowing on sites with invasive weeds to avoid nitrogen
release that favors heavy weed growth. If plowing is absolutely necessary, shallow plowing the
upper 2 inches of soil is recommended. Disc plows are often harmful to soil structure and should
not be used as a means of mitigating compaction unless coarse clods, produced when the soil was
worked when wet, dominate the site.
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