FEATURE
tests. The Solvita®C test gives an indi-
cation of the microbial soil respiration
and the Biolog test provide measure of
the microbial diversity in the soil. The
soil seedbank test was repeated in May
2018 and the soil biology tests in Sep-
tember 2018, after the removal of the
initial crop.
A non-metric multidimensional scaling
(NMDS) based on Bray-Curtis distances
(log-transformed data) and a permuta-
tion multivariate analysis of variance
(PERMANOVA) were used to analyse
differences in the seedbank composi-
tion, and a principal component analy-
sis (PCA) was performed on the Bi-
ologEcoplateTM test data, for each site
and year. A one-way ANOVA was done
on the Solvita®C data.
Due to low rainfall received during the
study period, only a few plants from
the initial crop established and it did
not affect soil P levels. The addition of
the initial crop did have a slight positive
impact on initiating nutrient cycling.
The microbial soil respiration increased
significantly (Redelinghuys: p = 0.0023;
Elands Bay: p = 0.015; Sandberg: p =
0.012) over time, although respiration
levels are still very low (<5) to low (<12)
(Figure 2). The microbial functional di-
versity was higher in the second year
(Figure 3). This could in the long-term
assist in the overall improvement of the
degraded area.
There were no clear differences in soil
seedbank composition between the
cultivated and control sites (p = 0.398) in
either years. The overall seedbank com-
position on the other hand changed
Figure 2: The microbial soil respiration
at the different sites (B = Redelinghuys;
N = Elands Bay; and S = Sandberg) for
May 2017 (before cultivation) and Sep-
tember 2018 (after harvesting).
Figure 4: A NMDS plot of seedbank
composition differences in 2017 and
2018 among sites (B, N, S) that were
cultivated (R) or undisturbed (C). B =
Redelinghuys; N = Elands Bay; S =
Sandberg.
the abundance of others (Figure 4). The
changes in the seedbank might be due
to the low rainfall in 2017, with seeds
germinating after the first rains, but
not surviving until seed set, resulting in
fewer species and abundance in 2018.
These results could indicate that rain-
fall remains the deciding factor on the
success of any restoration/rehabilitation
project in these arid regions.
Figure 3: A Principal Component
Analysis of the Biolog functional groups
at the three different sites in 2017 and
2018 (Eigenvalues: Axis 1 = 0.758; Axis 2
= 0.114). B = Redelinghuys; N = Elands
Bay; S = Sandberg. AMINACID = Amino
acids; CARB = Carbohydrates; CAR-
BACID = Carboxylic acids; PHOSP =
Phosphorilated.
significantly from 2017 to 2018 (p =
0.002) because of the disappearance of
some species and a marked decline in
The next step in this rehabilitation pro-
cess is to plant species that are indig-
enous to the area that are adapted to
higher soil P levels. The absence of in-
digenous perennial species in the soil
seedbank emphasises the need to add
seeds of these species to the aban-
doned land. It is hoped that the soil
microbial activity that seemed to have
increased by the initial crop will assist
in the establishment and survival of the
indigenous species, together with suf-
ficient rain.
References
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Grassroots
Vol 20
No 1
March 2020
08