چكيده لاتين :
1- Introduction
The land-use change is one of the critical worldwide issues that has caused a problem in natural
resource sustainability. The dynamics of land-use and land-cover change (LULC) affected by the
anthropogenic activities and climate change in arid areas, were caused environmental degradation of
these areas. This process has the negative effects on soil physicochemical properties. Soil degradation is
the key component of land degradation that affected by land-use changes. So that it causes organic
waste carbon, decreases the soil aggregate stability and structure and, consequently the raises of soil
erodibility. So to understand the impacts related to these changes in land-use (LU), assessment of the
effects of these changes on soil characteristics is important. Therefore, the current study aim was to
investigate the effect of land-use change on physico-chemical characteristics of soil and erosion in
Sistan area.
2- Methodology
This research has done in Sistan area. This area laid southeastern border Iran and Afghanistan. The
Sistan region forms a part of the Dasht-e-Lut and hence an exhibits extreme arid climatic regime. The
region is nearly flat and featureless arid plain with an average height of 465–500m ASL in its eastern
parts. In this study, at first spatial land-use changes in Sistan area determined. To achieve this purpose,
used satellite images. By using the Landsat satellite images related to the years 2001 and 2019, the land
use maps prepared, and by comparison approach in Idrisi Selva software, the map of land-use change
was extraction. After that, the areas that converted from rangeland to flood-agri and bare land
determined and that accuracy were assessed. Infield operation, 60 soil samples were collected from tow
depths 0-25 and 25-50 cm in different land-use such as rangeland, flood-agri, and bare land. The
Samples were collected in a completely randomized block design. To study the physical properties of
soil, by hydrometer method, by the soil texture, and by measuring the mean weight diameter (MWD),
the geometric mean diameter (GMD) and dry stable aggregates (DSA), the aggregate stability was
determined. Also, the soil moisture and bulk density were measured. To investigate the chemical
characteristics, the soil properties such as organic carbon, acidity (PH), electrical conductivity (EC),
sodium absorption ratio (SAR), CaCO3, Na, and available K and P measured in the soil laboratory. The
soil erodibility index calculated five characteristics, including sand, silt with fine sand, organic matter,
soil structure class, and the infiltration rate class of the soil profile. To analysis the mean of parameters
among different land uses were used the Duncan test.
3- Results
The result of the study of physical properties showed that the percentages of sand, silt, and clay
particles among the land-use that under study were significantly different. So that by the land-use
change from rangeland to flood-agri and bare land, the distribution of soil particle size differently, that
consequently the soil texture has changed from loam-silt-clay class in rangeland to lighter class loamsilt and loam-sand in flood-agri and bare land respectively. According to this change, the aggregate
stability of soil inland converted from rangeland to flood-agri, and bare land 34 and 45 percent have
decreased. Also by land-use change, the soil moisture 18% and 43 % has decreased respectively. The
results also showed that the bulk density of soil, acidity, electrical conductivity, Na, CaCO3 and
absorption ratio (SAR), increased in converted land-use whereas, the organic carbon and available K
soil, have decreased significantly. In addition, after land-use change, the erodibility index has increased
significantly (P < 0.05). So that the amount of this index in flood-agri and bare land compared to the
rangeland land-use, more than equal 4 and 7 respectively.
4- Discussion & Conclusions
In this study, for the first time, has investigated the physico-chemistry characteristics of soil and
erodibility in land converted from rangeland in Sistan area. The results revealed that the conversion of
natural rangeland to flood-agri and bare land had negative effects on the measured soil properties. So
that the percent of sand has increased, that changed the distribution of soil particle size, and according
to that, the soil texture has changed also. This caused the aggregate stability soil to reduce. In addition,
by decreasing the soil moisture, the plant growth has limited in this lands and given the high
evaporation potential in Sistan area, the evaporation from land surface increased and according to that
the electrical conductivity, acidity, Na and absorption ratio (SAR) in converted lands have increased,
whereas, the organic carbon and available K soil, have decreased. This process has caused the Soil
degradation, that affected by land-use changing. Therefore, the land-use change by destroying the soil
structure and land-cover in converted lands, cause increases the potential of erodibility, that given exist
environmental crises in Sistan area, has required the suitable planning to principle productivity of lands
in Sistan area.
