Results
Our surveys resulted in the identification of 52 and 57 species in 2019
and 2020, respectively. Seven grass species and five forb species
present in the seed mix were found in both 2019 and 2020. Both ripping,
seeding mixture, and a ripping/seeding interaction showed a significant
effect on species richness in 2019 (p< 0.10) (Figure 1).
Species richness ranged between an average of 18 and 9 species in 2019,
and 16 and 9 species in 2020. However, only seeding mixture influenced
species richness in 2020 (p< 0.10) (Figure 2).
Treatments planted to G/F had significantly more species in both years,
while treatments reclaimed with TSR had significantly more species only
in 2019. Simpson diversity showed a wider range of values between
treatments in 2019 compared to 2020 with values ranging from 0.75-0.47
and 0.84-0.75, respectively (Figure 3 and 4). Trends show that
treatments reclaimed with TSR and treatments planted with G/F have the
largest average diversity values in 2019 and 2020, respectively. Mulch
did not have any significant impact on either species richness or
diversity.
Year (p=0.001) (Figure 5) and two
of the main effects, seeding (p=0.002) and ripping (p=0.006), impacted
plant community composition, when both years were assessed collectively.
Additionally, year and seeding (p= 0.037) and ripping and seeding
(p=0.022) interactions influenced species composition and abundance.
Consequently, subsequent analyses were separated by year to evaluate how
the main effects impacted the plant community. We used functional groups
to explain primary drivers of plant composition.
Both seeding and ripping, and a seeding/ripping (p=0.056) interaction
had a significant effect on the plant community composition in 2019
(p< 0.10) (Figure 6). The primary functional groups
driving the 2019 plant community composition were native, perennial, C3
grasses on NMDS axis 1, short-lived perennials on NMDS axis 2, and
annual/biennials and C3 forbs on NMDS axis 3 (p< 0.10)
(Table 2). Additionally, percent volumetric soil moisture at 30 and 40
cm depth ranges, around the topsoil/subsoil interface were primary
drivers of plant composition on the NMDS 2 and NMDS 1, respectively
(Table 2).
Seeding and ripping were significant main effects in 2020
(p< 0.10), and additional analysis revealed a
significant seeding/ripping interaction (p=0.016) (Figure 7). Species
composition in 2020 was primarily driven by C4 species, and annuals on
NMDS axis 1, long and short-lived perennials and native species on NMDS
axis 2, and all C3 species on NMDS axis 3 (p< 0.10)
(Table 2). Both 30 and 40 cm depth ranges for percent volumetric soil
moisture were also a primary drivers of species composition on NMDS axis
2 (Table 2).
Year influenced Kentucky bluegrass abundance (p=0.029) with percent
cover increasing by 76% between 2019 and 2020 (Figure 8). Seeding
mixture (p=0.017) and ripping (p=0.004) influenced the abundance of KBG
when both years were assessed collectively (Figure 7). Treatments
planted with G and reclaimed with SSR (plus mulch) had significantly
less KBG compared to the site planted to G/F and reclaimed with TSR
(Figure 8).
Early trends indicate that treatments reclaimed with SSR and planted
with G (plus mulch) have the highest PR values with means of 35.9
(37.1), 44.9 (50.2), and 45.7 (48.7) J/m; respective, to treatment(s)
and depths. Furthermore, those treatments planted with G/F and reclaimed
with TSR consistently have the lowest PR values with means of 25.6,
28.1, and 33.2 J/m; respective by depth. The treatments with the highest
mean PR readings are significantly different than treatments with lowest
mean PR readings, at all three depths (p< 0.10) (Figure
9). G, SSR, plus mulch treatments at the 15-30 cm depth bin were
statistically different from all other treatments other than the G and
SSR treatment. Additional differences between treatments exist at depths
of 15-30 and 30-100, but differences in means appear to be between those
with the same seeding mixture or the same ripping technique. There was
no indication that standard reclamation procedures (i.e., the control)
resulted in significantly different penetration resistance readings at
any depth, at this time (Figure 9).
Treatments planted with G, SSR,
plus mulch were significantly different to treatments planted with G,
TSR, plus mulch and treatments planted with G/F and TSR
(p< 0.10), at the 20, 30, and 40 depth intervals.
Additionally, trends reveal there are significant differences between
treatments with the same seed mixtures and/or ripping techniques at both
30 and 40 cm depth intervals. Treatments planted with G/F and reclaimed
with TSR (plus mulch) were most frequently different to those treatments
across both seeding mixtures and ripping techniques (Figure 9).
Standard reclamation procedures (i.e., reference site) had significantly
greater (p< 0.10) volumetric soil moisture at the 40 cm
depth than those treatments planted with G/F and reclaimed with TSR.
Volumetric soil moisture readings at the 10 and 60 cm depths showed no
differences between treatments (p>0.10) (Figure 10). We did
not assess the 100 cm depth interval because it likely has no influence
over plant community dynamics this early in the reclamation phase. At
the 20, 30, and 40 depth intervals mean percent values of those
treatments planted with G, SSR, plus mulch (22.3, 23.7, 26.0, respective
of depth) had significantly greater volumetric soil moisture compared to
treatments planted with G, TSR, plus mulch (16.7, 18.8, 19.4, respective
of depth) and treatments planted with G/F and TSR (17.2, 17.9, 15.7,
respective of depth). The number of treatments showing significant
differences increased with depth with the greatest variability being
observed at both the 30 and 40 cm depth intervals. Significant
differences between combinations exist between treatments with the same
ripping techniques and same seeding mixture (p< 0.10)
(Figure 10). Treatments planted with G/F and reclaimed with TSR (plus
mulch) were most frequently different to those treatments across both
seeding mixtures and ripping techniques (Figure 10). Standard
reclamation procedures (i.e., the reference site) had significantly
greater volumetric soil moisture at the 40 cm depth than those
treatments planted with G/F and reclaimed with TSR
(p< 0.10). Volumetric soil moisture readings at the 10
and 60 cm depths showed no differences between treatments
(p>0.10) (Figure 10).