"Growing
Soil":
Establishing
sustainable native plant growth on drastically disturbed soils
in harsh environments
by
Peter McRae, Mir-M. Seyedbagheri, John Steinbacher
Abstract:
A
two-pronged approach is vital to reclamation success: (1)
growing soil; and (2) eliminating the "weak link" factor.
A focus upon "growing soil" as a strategy for establishing
sustainable native plant growth on drastically disturbed (sterile)
soils is proving to be both successful and consistent in its
results. The strategy recognizes that the key to establishing
native plant growth is to re-build sterile soils into vibrant
organic matter, rich in living organisms. The objective is
to fire up the natural cycling processes of the soil's "biological
engine". Rather than merely growing plants per se, this strategy
amounts to setting the stage for the natural re-establishment
of mycorrhizal fungi, soil bacteria and other beneficial
soil
organisms necessary to grow early seral stage plants -- pioneer
species that act as soil builders. This is accomplished through
the incorporation of certain organic complexes of enzymes
and bacteria, and protein-rich organic fiber nutrients into
the seed bed. We are growing soil organisms first and foremost,
in order to sustain vegetative cover on site through the
stages
of plant succession in our efforts to ultimately re-establish
climax native plant species.
The
rationale for pursuing the re-establishment of soil microbes
is predicated upon the recognition that grass, forb and
shrub species indigenous to the semiarid West are dependent
upon mycorrhizal fungi associations to exist. The host
plants
supply the mycorrhizal fungi with simple carbohydrates
(sugars) from photosynthesis. In return, the fungi, using
energy
derived from the host plant, extend hyphal strands (feeding
tubes) far into the soil, increasing the surface area
of
roots to improve water and nutrient absorption for its
host. This mutual symbiosis between the root systems
of native
plants and site specific fungi is behind what makes established
native plants so "hardy" (so tolerant to low nutrient
levels, drought, high soil temperatures, heavy metals,
soil salinity,
soil toxins, fungal and bacterial root pathogens, and parasitic
nematodes), and yet so difficult to grow and keep growing.
Despite
the existence of winning techniques and formulated materials
to implement such "growing soil" efforts in harsh environments,
true native plant establishment on sterile soils continues
to be elusive owing to Nature's intolerance of, and the
reclamation industry's tolerance of the "weak link" factor.
The "weak link" factor is simply that one's level of plant
establishment success will correspond to the weakest link
in the process of design, supply, and field implementation.
For a variety of reasons, the sabotaging influence of the
weak link factor pervades the industry and is largely responsible
for the industry's high level (80% +) of total seeding efforts
that are ultimately judged "disappointing".
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