Effects of Vegetation Cover on Runoff and Soil Erosion

This literature review explores the impact of land surface processes on the environment and how vegetation cover can help reduce soil erosion and runoff. The effectiveness of different types of vegetation cover is discussed, including aboveground vegetation cover, surface litter layer, and underground roots. The article emphasizes the importance of choosing the most effective vegetation cover for a particular environment to prevent soil loss and runoff.

Running Head: LAND SURFACE PROCESSES
Land Surface Processes
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Institutional Affiliation
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Land surface processes 1
Introduction
According to Otil et al (2007), land surface refers to the layer that comprises of the bottom part
of the atmospheric layer, the environment above the soil by a few meters, the continental
biosphere and surface water bodies. Otil et al (2007) states that land surface processes refers to
the processes that lead to the exchanges of mass and energy in that region found between the
atmosphere and land. These exchanges are normally governed by the soil hydrological processes
in the surface and the behavior of the continental biosphere coupled by molecular motions in the
atmosphere. In today’s world, land surface processes have had adverse negative effects on the
entire global climate. This has led to the change in climatic conditions of different places across
the world as seasons are affected which in turn affect the small scale farmers who even do not
realize the cause. Also global warming has rised as a result of these processes and the effects can
be felt all over the world already. This has been caused mainly by industrial pollution, especially
in developed countries. However there are certain mitigation processes that have been put in
place to ensure that the environment is not destroyed and in the cases where it has been
destroyed try and rescue it. Some of the negative outcomes of the land surface processes are
massive and sudden landslides. Thus this literature review will be based on the effects that
different types of vegetation found in different climatic regions has on runoff and soil erosion
The term vegetation in this context refers to the plant species that provide ground cover in a
particular region of the earth. This is so because the earth has different vegetation covers around
the globe and the vegetation is mainly dictated by climate of that place. Surface runoff refers to
the process of water running over the earth surface and is caused mainly by heavy rain pour or

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precipitation. It is considered the number one agent of soil erosion. Soil erosion on the other
hand refers to the process that leads to the displacement of earth’s most upper layer of soil and
this is caused mainly by human activities, animals, ice and mostly by water. The processes of
runoff and soil loss cause enormous on-site and offsite negative outcomes that include the
decline of a land’s agricultural production capacity, emergence of flash flooding in areas it was
never experienced, soil degradation and the transfer of soil nutrients, chemicals and also the
pesticides used from one region to other regions. It also causes natural disasters such as
landslides and debris which pose grave dangers to humans and animals alike as buildings and
other structures are prone to collapse. This results in adverse ecological problems and also socio-
economic ones more so in the regions that fall under arid and semi-arid climatic conditions.
(Zhou, 2008).
Around the globe the use of vegetation has proved to be one of the most effective and biological
ways of reducing if not eradicating soil loss completely. The effects that vegetation has on soil
erosion and runoff are usually influenced mainly by the structure and function of the vegetation
present in that particular area. There are various vegetation structures that aid in the controlling
soil erosion and runoff. Hence to effectively make use of vegetation as cover and a controller for
soil loss and runoff, one must know the most effective vegetation cover of a particular place they
want to use vegetation cover on. Below is a breakdown of how different vegetation covers aid in
the controlling and minimizing if not eradicating occurrence of runoff and soil erosion.
Aboveground vegetation cover
This type of vegetation cover is so far considered to be the most effective method of minimizing
the occurrence of soil erosion and runoff. This is because vegetation in this case redistributes

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how rainfall finally reaches the ground and thus weakens rainfall and consequently reducing the
runoff and soil erosion. There are various ways in which vegetation intercepts rainfall and this
include the stem flow, through fall and canopy interception. Under the category of above
vegetation cover there are two factors that affect the rate of runoff and soil loss and this two are
the vegetation type and coverage rate.
Vegetation type
Vegetation occurs in different types and thus they have different plant morphologies and
vegetation structures thus bringing about different rainfall interception and thus affect the splash
erosion effect. Shrubs are considered the most effective in the reduction of the rate at which
runoff and soil erosion occur. (Okin 2007) They are followed closely by herbaceous plant types.
This however is greatly dependent on environmental factors and thus greatly varies from one
region to another. For instance in Gansu province of the Republic of China forest is considered
to be the best and most effective vegetation cover as compared to pasture. In Portugal however,
pastures are the most effective in reducing soil loss and runoff with the total coverage of forests
standing at 12% as compared to the pasture total coverage of 75%.
Vegetation coverage
Vegetation coverage plays an equally major role just as the vegetation type. Vegetation coverage
helps by ensuring a reduction in the amount of runoff and soil erosion in a place with its
effectiveness increasing with an increase in a region. However on reaching the optimum
coverage point, the effectiveness of vegetation in reducing runoff and soil loss remains stable but
in case the coverage is increased beyond the optimum: The effectiveness of the coverage reduces

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significantly all together.(Zhou, 2008). There are certain threshold values that are essential in the
reduction of runoff and soil erosion. The threshold values of coverage rates are divided into two
parts; the lower threshold that is between 10%- 30%. In this case vegetation effectively reduces
runoff as long as the coverage rates do not supersede the threshold values. The second threshold
is the upper one which lies between 50%-60%. In this category effectiveness of the coverage is
not increased even when the coverage goes past the threshold values.
The effects of the vegetation type and coverage are almost identical in terms of effectiveness in
the quest of reducing runoff and soil erosion. The level of effectiveness of various mitigation
methods are depended mostly with the regions; for instance in the forest environment, shoots are
the most effective in the reduction of soil erosion and runoff as compared to the open grasslands.
In the open grasslands roots are much more effective than the shoots as compared to the forest.
SURFACE LITTER LAYER
Surface litter layer refers mostly to the leaves that cover that the ground and that usually falls
from the vegetation above the ground. They function by protecting of the soil from raindrops by
intercepting of rainfall thus increasing infiltration, also interfering with the evaporation rate and
mainly holding the top layer soil thus reducing runoff and soil loss. Litter layers depend on the
biomass in it to effectively reduce soil erosion and runoff but this still varies from one litter type
to another. This means that the effectiveness of the surface litter layers to reduce run off and soil
loss reduces significantly with the reduction of biomass levels in the litter. Litter layers of
different vegetation types perform differently in reducing of soil loss and runoff through
intercepting of raindrops. For example in Northern China broadleaf and needle forest litter
reduce runoff by 28% and 30% respectively. Generally presence of litter covers reduces the rate

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of soil loss and runoff significantly. Inorganic surface litter on the other hand does the opposite
of what surface litter made of leaves does and this is to increase the rate of runoff and soil loss.
This type of litter is mostly made up of plastics, woolen clothes, aluminum cans and plates,
polythene paper bags and other non degradable materials used by humans. Thus we can safely
say that runoffs and soil rate loss are far much lower in areas that have surface litter as opposed
to land environment that are bare or have little surface cover.
UNDERGROUND ROOTS
It is the most effective soil erosion and runoff prevention method as compared to the above
ground method and surface litter layer. This is because it holds the soil beneath the ground
together thus addressing the thorny rill and gully erosion processes. However, just like the above
the ground vegetation cover the contribution of roots to effectively curb runoff and soil loss
reduction varies with the vegetation types. Its aid in the reducing of soil erosion and runoff is
greater compared to that of shoots in the forest environment but have almost similar effects
under grassland environment.
Roots are known to conserve water and soil through two major means which are first by directly
protecting soil detachment and increase infiltration in the process thus leading to the reduction of
soil erosion and runoff. The second way according to Zhou et al (2007) is by improving soil
properties found in a particular type of soil and this done through the increasing of soil organic
matter levels, also by enhancing quantity of soil stable aggregates by adding of natural manures
and stabilizing the soil layer structures all of which subsequently led to the reduction the soil
detachment rate.

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Roots reinforce soil hence consequently lead to the reduction of soil loss and runoff in two
direction which are Horizontal and vertical directions. The downward penetration of roots
strengthens soil stability through their interactions. The horizontal movement of roots enhances
soil stability through their tensile strength. Roots underground form networks thus binding soil
particles and in the process ensuring soil cohesion.
Roots generally aid in the binding of soil particles and consequently reduce the runoff and soil
erosion. In China, roots that are found between the depth of 0-30cm in the shrub lands and
grasslands and at between 0-60 cm in the forest environment affect greatly the rate at which loss
of soil and runoff occurs.
Water and wind are both agents of soil erosion and runoff. They act by destabilizing plant hence
eventually exposing the roots and leading to their fall. This results to leaving the soil bare,
exposed and vulnerable. Thus plants with dense fibrous root systems are the most effective in
holding together of soil. For example, grasses have fibrous roots systems that enable them to
keep the soil around them firm and in place. Plants with taproots also are advantageous due to
their deep roots that ensure they are firm and cannot be blown over by wind or washed away by
water. This is mostly significant when it come to shifting soils especially in the sandy beaches.
Regardless of the type of vegetation cover used, as long as it is effective the end result is always
the same; to prevent soil loss and run off. As stated by Zhou et al (2007) one ought to choose the
most effective vegetation cover for their environment so as to ensure they effectively curb the
runoff and soil erosion which usually wash away the soil nutrients leaving the soil impoverished
and poor.

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Conclusion
Land surface processes do greatly affect the environment and in some extreme cases lead to the
adverse changes in climate in the world. Most of these effects are as a result of industrial
pollution and mostly from the developed countries. Despite the world’s superpowers coming
together to forge their way forward on how to address this thorny issue, it still remains a thorny
issue as the effects of this pollutions are felt even thousands of miles from where the polluting
industries are located and the greatest sufferers of this are the poor third world country citizens.
Thus mitigation processes have been devised to reduce the effects of climate change. Among the
numerous methods that have been devised, the use of vegetation cover is the most effective
method in the control and reduction of soil erosion and runoff. This calls for the aggressive
indulgence in environment conservation through a forestation, encouraging crop rotation and
also through discouraging of deforestation. Governments across the world should come up with
policies and legislations that ensure environment is protected at all cost for future generations as
if they do not, soil loss and runoff may lead to degradation of our environment.
Vegetation type and vegetation coverage interact to produce a seamless process of ensuring that
soil is conserved and the degradation of the environment reduced or even halted all together. The
various vegetation types do assist in ensuring that soil loss and runoff do not lead to the adverse
effects that can lead to the unreversable effects on the environment and also in reducing possible

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occurrence of catastrophic natural disasters. It should thus be the most advocated for method of
arresting soil erosion and runoffs as it is purely hundred percent organic.
Reference
Zhou, P., Luukkanen, O., Tokola, T., &Nieminen, J. (2008). Effect of vegetation cover on soil
erosion in a mountainous watershed. Catena, 75(3), 319-325.
Li, J., Okin, G. S., Alvarez, L., & Epstein, H. (2007). Quantitative effects of vegetation cover on
wind erosion and soil nutrient loss in a desert grassland of southern New Mexico, USA.
Biogeochemistry, 85(3), 317-332.

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