Geoscience Reference
In-Depth Information
times.
30
Paleolithic hunters, using
re for hunting, unintentionally in
uenced soil
ecosystems via vegetation. Human-induced ampli
cation of erosion has accom-
panied human life ever since the advent of a sedentary life-style.
Important origins of agriculture lay in the semi-arid south-west corner of Asia,
the Levant and Fertile Crescent east of the Mediterranean where water scarcity was
a limiting factor. Hence, irrigation techniques, next to the hoe or ard, were the main
early interventions into soils. Short-term and long-term interventions can be dis-
cerned. Dams, irrigation networks and terraces are among the longer-lasting.
Mechanical (such as hoeing, plowing and harrowing), chemical (fertilization and
soil amendments) and biological (weeding, mulching, and irrigating) cultivation
techniques in
uence soils on a shorter term. Salinization due to irrigation under arid
conditions was a problem for the early civilizations in the Indus and Euphrates/
Tigris valleys: soils there are still impacted. Archaeological excavations have
produced evidence for manuring for Bronze Age European settlements in areas as
far apart as Estonia, the Netherlands and Switzerland. The practice seems to have
been widespread.
31
From the early civilizations onwards, aside from their main use in agriculture,
soils were the basis of infrastructure. Roads and buildings sealed soils; cisterns,
cellars, sewers and waste pits all needed and changed soils.
32
Figure
3.3
shows major types of interaction between humans and soils and their
impact on soil processes. Again, parent material, climate, vegetation and relief are
the natural factors determining which kind of soil is available. Human in
uences
differ with soil use: grazing animals on rangelands have in
uences different from
those on either cropland or forest. Infrastructural use leads to a fourth, apparently
different impact. Grazing can lead to changes in micro-relief and to compaction; it
also leads to nutrient input through animal feces. Humans using
re on pastures to
prevent perennial growth exert an in
uence on plant species, and hence, on soils.
Grazing animals likewise have an effect on vegetation, leaving poisonous or thorny
plants to grow. The impact on soils is widespread, as grazing areas are usually
large. Its details depend on the animal species and grazing patterns and density, but
the overall impact is relatively small. Human in
uence on the soils of croplands is
much more pronounced. Cultivation techniques such as hoeing, plowing and har-
rowing change the physical characteristics of soils. Fallowing, leaving soils to rest
from cultivation, was a time of intensive plowing at least in Roman antiquity. Wild
plant species growing on the land during fallow periods also in
uence the soil. Soils
were and are changed also by crop selection (the most striking example are
legumes, with their nitrogen-
xating abilities), by residue management (e.g. by
burning or plowing stubble) and, most importantly, by nutrient inputs through
fertilizing agents. Monoculture of any kind does change soils. Water management
plays a decisive role in irrigation agriculture. Some slow-growing crops leave land
30
gerer (
2005
).
31
Bakels (
1997
), Reintam and Lang (
1999
).
32
Einw
รถ
This summary is based on Winiwarter (
2006a
).
