Deforestation effects on soil erosion rates and soil physicochemical properties in Iran: a case study of using fallout radionuclides in a Chernobyl contaminated area

Abstract

Abstract. Deforestation for farming and grazing purposes has become a global challenge. To study the impact of deforestation on soil erosion rates and soil physicochemical properties, Zarivar Lake watershed, Kurdestan Province, Iran, was selected. Converting the steep hillslopes naturally under oak forest to rainfed vineyards has been one of the most common land-use changes in the area. We used 137Cs and 210Pbex radionuclides and quantified the Chernobyl-derived 137Cs fallout with 239+240Pu. The soil samples were collected from two adjacent and similar hillslopes, one of which is under natural forest, while the other is under rainfed vineyard. Using 137Cs/239+240Pu rates and a simple unmixing of the 137Cs sources indicated that 50.2 ± 10.0 % of 137Cs was Chernobyl-derived. The mean reference inventory values of 137Cs, 210Pbex, and 239+240Pu were estimated to be at 6152 ± 1266, 6079 ± 1511, and 135 ± 31 Bq m−2, respectively. At the forested hillslope, net soil erosion rates based on 137Cs, and 210Pbex, techniques were estimated to be at 5.0 and 5.9 Mg ha−1 yr−1, respectively, resulting in Sediment Delivery Ratios (SDRs) of 96 and 70 %. However, at the vineyard hillslope, the net soil redistribution rates were at 25.9 and 32.5 Mg ha−1 yr−1 for 137Cs and 210Pbex, respectively, resulting in respective SDRs of around 95 and 92 %. Both 137Cs and 210Pbex indicated that as a result of deforestation, soil erosion has increased by approximately five times. Percolation Stabilities (PS) in forest and vineyard topsoil are about 309 and 160 gr H2O 600 s−1 classified as rapid and moderate PSs, respectively. Rapid PS in forest soil implies high aggregate stability, whereas moderate PS in vineyard soils indicates that they are generally weakly-structured. All in all, the results of the present study revealed that deforestation and converting natural vegetation to cropland prompted soil loss and deteriorated physicochemical properties of the soil.

Soil and water conservation measures to adapt cropping systems to climate change facilitated water stresses in Africa

“…Deforestation and land clearing uncovers the soil and increases the erodibility of the soil, especially on steep slopes. Clearing the forest on steep-sloped lands can increase soil erosion by 5 to 20 times that of flat terrains (Khodadali et al, 2021). Soil compaction increases soil bulk density while decreasing porosity (Chakraborty and Mistri, 2017).…”

Efficacy of Adaptation of Smallholder Maize Production to Climate Variability in Selected Countries of Kenya

“…Increasing maize farm size is associated with the loss of land area covered with trees which leads to an increase in maize yield in the short run and a decrease in the long run (Epule and Bryant, 2015). This is because deforested areas escalate the adverse impact of climate change on maize production when such areas become vulnerable to soil erosion and compromise nutrient storage (Khodadadi et al, 2021).…”

First application of plutonium in soil erosion research on terraces

“…239+240 Pu and 137 Cs in the environment are rapidly and strongly adsorbed by fine soil particles and redistributed within the soil itself [21,22,23]. Thus, soil erosion can be traced using the inventories and distribution characteristics of 239+240 Pu and 137 Cs in the soil [21,24,25,26,27,28,29].…”

“…Although 137 Cs has been extensively applied to soil erosion in past decades [1,24,25,30,31,32], 70% of the total 137 Cs deposited by atmospheric nuclear tests in the environment has decayed away so far, which has significantly reduced the sensitivity of 137 Cs as a tracer of soil and sediment transport in the future. 239+240 Pu is an ideal replacement for 137 Cs due to its longer lifetime and the same origin and strong association with soil particles as 137 Cs.…”

“…239+240 Pu is an ideal replacement for 137 Cs due to its longer lifetime and the same origin and strong association with soil particles as 137 Cs. In recent years, plutonium has been successfully applied to soil erosion studies in the hilly landscape north of Munich, Germany [33,34]; the Alpine grasslands of Switzerland [27]; the lower Cotter catchment of the Australian Capital Territory [35]; the hillslopes of the Zarivar Lake watershed, Kurdistan Province, Iran [24]; the coastal area of Liaodong Bay in Northeast China [4,21,28]; and the hilly gully region of the Loess Plateau in China [36]. However, the study areas are mostly limited to grasslands, woodlands, hillslopes, and commonly sloping cultivated land.…”