Chemistry Reference
In-Depth Information
Slope gradient and rainfall are the significant influencers on soil erosion,
with the 'Grain for Green Project' driving changes in vegetation cover as a
method to control erosion on steep slopes. Alternative strategies employed
have been the terracing of hillsides to enable arable production on slopes
previously deemed too steep to cultivate. Not only is soil erosion minimised
but soil properties critical for increased yield are improved. Terracing increases
soil moisture characteristics, within 1 year of being built increasing moisture
content by 8.9-14.45% when compared to sloping land. Soil fertility also
increases in terraces, when compared to a 15u slope, with organic matter
increasing by 26%, total N 8%, total P 4%, fast-acting N 12% and fast-acting P
by 20%. As a result of improvements in soil quality, yield has been shown to
increase by 3.6% in the first year after terrace construction and 27.1%, 35.3%
and 52.8% after 3, 5 and 7 years, respectively.
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Key to understanding the long term-effects of vegetation restoration is having
evidence of longer term impacts on soil properties. The Ziwuling Forest within
the Loess Plateau covers an area of approximately 23 000 km
2
and contains
several areas which have been abandoned for differing lengths of time. Such sites
are key in allowing long-term changes in soil properties to be assessed through
successional changes over periods of 150 years by natural vegetation.
Successional changes were assessed through changes from arable production,
to grass, shrubs and finally forest.
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Soil was densest in the farmland plots (1.29
Mg m
23
) and lowest in forested soils (0.99 Mg m
23
). Macropore spaces in soil
increased over successional changes, implying greater hydraulic conductivity
and water-holding capacity. After 14 years of abandonment soil physical
properties improved, with an increase in hydraulic conductivity attributable to
shrub and tree roots loosening and improving soil structure.
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Once soils have become severely eroded a return to a fertile and healthy soil will
only occur over extended periods of time. Evidence from the Loess Plateau has
shown that one restoration method does not fit all. Stabilisation strategies will
help minimise further degradation; however, the methods employed must be
chosen with a realistic expectation of the likely outcomes. Arable production of
crops from sloping land is clearly unsustainable in environments with historically
high erosion rates. In such situations forestry may be better suited, but sustainable
management strategies must be applied to ensure soil is protected year-on-year
without secondary effects such as water deficits caused by overuse of water by
vegetation. Research has demonstrated that several remediation strategies are
available and these should be applied relevant to the issue being addressed.
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6 Case Study 2 - Recultivated Mine Soils, Eastern
Germany (Lusatia)
Germany is the leading lignite producer in the world.
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Coal mining in
Germany is distributed over the three main areas of Rhineland in the west,
central Germany and Lusatia in eastern Germany. This chapter concentrates
on Lusatia. Germany, with its relatively dense population, needs to reclaim
