Relationship between Climatic Factors and Soil Erosion
Abstract
Climatic factors and soil erosion in  different regions of the world, particularly the general circulation model (GCM), cumulative erosion potential  (CEP) model. However, these models  proved that it is difficult to determine future soil erosion rates due that not  all elements are factored into the model, but they can provide possible outcomes  of soil erosion in a region of the earth. Depending on the intensity of the climatic factor, different results can occur in the model.
Introduction
Different climatic factors can affect the rate of soil erosion in an  area, such as wind, precipitation, temperature, carbon dioxide, soil content,  land use and vegetation. Depending on the climate, soil content, soil stability, soil roughness,  soil steepness, precipitation and land use have been considered to be a stronger  determinants of erosion rate than climate change (Favis-Mortlock and Guerra, 1999; Romkens et al., 2001; Mulligan, 1998; Imeson and Lavee, 1998;  Favis-Mortlock and Boardman, 1995). For an example, dry soils  are more susceptible to water erosion than moist soils are. Meaning that when it rains on a dry  soil, there is a good chance of water erosion  than on a moist soil (Sauerborn  et al., 1999; Imeson and Lavee, 1998). Each climate has its own variable range of climatic factors.  Large amounts of land use allows the soil type to be more susceptible to erosion when  comparing it to soil have does not have large amounts of land use, which can not  be determined through models (Favis-Mortlock and Guerra, 1999).In order, for soil erosion to take place, the climatic factors, such as rainfall, have to be acting on each  other. For instance, rainfall to  has to occur when the soils surface is insufficiently protected (Favis-Mortlock and Guerra, 1999).
A place that represents extreme usage of agriculture is at Sorriso, Mato Grosso State, Brazil (Favis-Mortlock and Guerra, 1999). Naturally, there are rocks (limestone,  sandstone, and other sedimentary rocks) that tend to produce erodible soils (Favis-Mortlock and Guerra, 1999). The vegetation can decrease the organic matter, which can cause the soils  to erode easily.  In agricultural use, the heavy machinery can cause the soils to erode quite easily and they are  prone to crusting (Favis-Mortlock and Guerra, 1999). Soil erosion can also depend on how  stable the system is.  If the  stability of the soil is not very good then, then there is a good chance that  the soils will erode easily (Mart�nez-Mena et al., 1998). The hypothesis is that several different  climatic factors can have effects on the soil erosion rate.
Materials/Methods
In order to get an accurate measurement of soil erosion with relation to  climatic factors, models are used (Romkens et al., 2001), which can be  difficult due to the temporal time scales (Imeson and Lavee, 1998). There are several models  that can be used including plot-scale models, slope scale models, catchment  scale models, cumulative erosion potential (CEP), global scale models, and  general circulation models (GCM) (Kirkby and Cox, 1995; Sauerborn et al., 1999; Favis-Mortlock and Boardman, 1995). Plot-scale models are used to represent physical processes and they are  for small areas and short periods of time. Slope scale models are used when considering patterns of erosion and  deposition along a slope.  Catchment scale models are used to generalize the mirco-topography of an area.Global scale models are used  to generalize the common factors that influence erosion to occur (Kirkby and  Cox, 1995). The calculation  for CEP is CEP = 2 Noro2 exp (- h/ro), where No and ro represent the effects of  the daily rainfall, and ho is the significant soil hydraulic  parameter (Kirkby and Cox, 1995).  The CEP model can be modified in several ways such as it can be calculated for a given storage capacity and linkage of the vegetation cover in  an area (Kirkby and Cox, 1995).
Analysis
In terms of the different types of models, several factors can play a  significant role in determining the erosion rate in an area, such as the amount  of evapotranspiration from plants and added organic material from leaf fall (Kirkby and Cox, 1995) and these two elements in soil erosion rate are difficult  to determine in the models. However, these elements served to determine the biomass and temperature in the region.In the models, the rainfall served as a way to determine the evapotranspiration in the  region.Also, the variability of  each type of climate had to be taken in account in the various models, such as  seasonally temperatures and precipitation.
When using the general circulation models (GCM), it showed that it is  difficult to determine what future climates would be like and as a result, it is  difficult to determine what future erosion rates would be. So, when the models are used, the results are merely estimates of erosion rates and circumstances would be, only 60% of the models have been used (Favis-Mortlock and Guerra, 1999; Favis-Mortlock and Boardman, 1995).
In terms of results, some of them have been noted to be left-skewed in  South Downs in United Kingdom.  The general circulation models from South Downs, United Kingdom showed  the relationship between the amount of rainfall and erosion rate, which shows a  nonlinear relationship.  According  to the data, erosion decreased during low rainfall scenarios and increased in  all scenarios, especially during wet scenarios. This relationship exhibited a nonlinear positive feedback, in which erosion rates during the wet years  increase when comparing it to dry years (Favis-Mortlock and Boardman, 1995).  According to Favis-Mortlock and Boardman, changes in mean annual rainfall can be expressed as a percentage.  For instance, if the mean annual rainfall increased by 7% in South Downs, United Kingdom, then the soil erosion has the potential of increasing by 25% (1995).
Interpretation
In terms of the models when concerning Sorriso, Mato Grosso State, Brazil, there are indications  that the erosion rates will continue due to the heavy agricultural use in  Brazil. The three parameters are placed in the WEPP, a physically based, modeling system and the current rate of soil erosion. From the models, it is determined that  the future sediment yield would be either at the current rate or exceeding it, depending on the future agricultural use in Brazil (Favis-Mortlock and Guerra, 1999).
In terms of the characteristics of rainfall is that when it is uniform,  it can cause the sedimentation to be heterogeneous and a nonrandom pattern, and this depends on the type of climate that the soil system, which results in a  nonlinear system (Imeson and Lavee, 1998).
The future erosion rates depend on several parameters, rainfall, climate,  land use, and soil content, however, there is an extreme of uncertainties about  the data from the various types of models. There is no way of determining how much land use or annual precipitation would be in the future.  According to Favis-Mortlock and Guerra,  if there is an decrease in productivity in Brazil, there could be increased soil erosion rates due to how much agricultural use was done in the past (1999). The reason for this is that increased biomass production has the potential of reducing the soil erosion rates in a region of the world (Sauerborn et al., 1999) due that the biomass gives  stability to the soil content (Imeson and Lavee,1998; Mart�nez-Mena et al.,  1998).
In terms of soil stability, areas that have dry soil in the footslope zone tended to erode more easily than wetter soils (Mart�nez-Mena et al., 1998). This is due to that there is a good possibility dry soils could erode from the wind. In addition, if the soil's stability was not good, especially in semi-arid regions, then there is a  good chance that soil could erode (Mart�nez-Mena et al., 1998).
The topography of the land surface can have effects on the soil erosion rate in the region. For an example, smooth surfaces can have large amounts of soil erosion, whereas, rough surfaces  have smaller soil erosion rates, which is caused by the resistance in the slope  and the amount of soil detachment (Romkens et al., 2001). The soil detachment can also affect the soil water pressure, if the water pressure would increase, and then the soil erosion rate would increase (Romkens et al., 2001).
Conclusion
By using models to determine current and future soil erosion rates in  different parts of the world is definitely a good way of doing it, so that there  is no harm to the test site.  However, models that are more accurate need to be developed so there are no uncertainties in the modeling system and results. The modeling  systems that are currently being used to provide good data for estimating on how climatic factors affects soil erosion rates around the world.
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