Agriculture Reference
In-Depth Information
Table 5.4.4.
Mean ratios of carbon indices (0-10 cm depth) in undisturbed (UD) and restored (R)
soils.
C
mic
:C
org
(mg C g
−
1
C)
C
resp
:C
mic
(mg CO
2
-C g
−
1
C h
−
1
)
C
resp
:C
org
(mg CO
2
-C g
−
1
C h
−
1
)
Sites
UD grass
35.8
14.1
0.086
UD wood
28.8
22.8
0.112
R21 grass
19.0
20.3
0.096
R21 wood
27.1
28.2
0.193
R9 grass
27.3
19.8
0.180
R9 wood
26.7
28.9
0.279
LSD 5%
3.81
5.62
0.034
C
resp
:C
org
ratios, perhaps reflecting their particularly low aggregation
levels. There was no consistent management difference for the C
mic
:C
org
ratio, but woodland soils had markedly higher C
resp
:C
mic
and C
resp
:C
org
ratios irrespective of land type. These latter differences may be linked to
lower
woodland
soil
aggregation
levels
and
earthworm
populations
(Scullion, 1994).
Conclusions
Whilst total organic matter levels had recovered 21 years after soil
restoration, differences from undisturbed soils in organic composition and
dynamics remained. Variations in the degree of physical protection of labile
organic fractions in stable aggregates offer one explanation for these differ-
ences. Earthworms influenced both aggregate and organic stabilization
processes. A common feature of restored soils was the higher than expected
respiration at any given microbial biomass or organic matter content. This
feature may arise because of the limited physical protection offered to
organic matter and may explain the low carbohydrate contents of restored
soils. Increased inputs did not always promote soil recovery. Land use
differences were confounded with tree age. Nevertheless, restored and
undisturbed soils showed, for the most part, similar differences in carbon
indices between grassland and woodland.
Acknowledgements
The authors wish to acknowledge the support of the former British Coal
Opencast Executive. The second author held a Pakistan Government
Studentship during his studies.
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