Impacts of oak deforestation and rainfed cultivation on soil redistribution processes across hillslopes using 137Cs techniques

Abstract

Background As one of the main components of land-use change, deforestation is considered the greatest threat to global environmental diversity with possible irreversible environmental consequences. Specifically, one example could be the impacts of land-use changes from oak forests into agricultural ecosystems, which may have detrimental impacts on soil mobilization across hillslopes. However, to date, scarce studies are assessing these impacts at different slope positions and soil depths, shedding light on key geomorphological processes. Methods In this research, the Caesium-137 (137Cs) technique was applied to evaluate soil redistribution and soil erosion rates due to the effects of these above-mentioned land-use changes. To achieve this goal, we select a representative area in the Lordegan district, central Iran. 137Cs depth distribution profiles were established in four different hillslope positions after converting natural oak forests to rainfed farming. In each hillslope, soil samples from three depths (0–10, 10–20, and 20–50 cm) and in four different slope positions (summit, shoulder, backslope, and footslope) were taken in three transects of about 20 m away from each other. The activity of 137Cs was determined in all the soil samples (72 soil samples) by a gamma spectrometer. In addition, some physicochemical properties and the magnetic susceptibility (MS) of soil samples were measured. Results Erosion rates reached 51.1 t·ha− 1·yr− 1 in rainfed farming, whereas in the natural forest, the erosion rate was 9.3 t·ha− 1·yr− 1. Magnetic susceptibility was considerably lower in the cultivated land (χhf = 43.5 × 10− 8 m3·kg− 1) than in the natural forest (χhf = 55.1 × 10− 8 m3·kg− 1). The lower soil erosion rate in the natural forest land indicated significantly higher MS in all landform positions except at the summit one, compared to that in the rainfed farming land. The shoulder and summit positions were the most erodible hillslope positions in the natural forest and rainfed farming, respectively. Conclusions We concluded that land-use change and hillslope positions played a key role in eroding the surface soils in this area. Moreover, land management can influence soil erosion intensity and may both mitigate and amplify soil loss.

Limited role of soil texture in mediating natural vegetation response to rainfall anomalies

“…In addition to soil textural effects, other geomorphic and biochemical processes (e.g. topography, physical and chemical weathering, biological activity, water flow patterns) may affect crop response at a specific location in the landscape (Hallema et al 2016, Ayoubi et al 2021. The variation (spatial and temporal) in such physical and chemical processes is often considered during crop placement at the field scale (Thelemann et al 2010).…”

Variation of winter wheat grain yield and its quality in fields with different soil cover

“…Yield was not significantly affected by drought, as all soil types had a high available water capacity. Other researchers also highlighted that differences in soil texture and topography influenced yield variability at the field spatial scale (Manoli et al, 2015;Hallema et al, 2016;Fang, Su, 2019;Neupane, Guo, 2019;Ayoubi et al, 2021), especially during dry years, when water reserves and water available to the plants were strongly influenced by a local soil texture. For example, Fang and Su (2019) reported that in dryland farming, sandy loam soils showed a more significant decrease in crop productivity and an increase in N leaching losses compared to loamy soils.…”

Role of transportation infrastructures on the alteration of hillslope and fluvial geomorphology

“…While SLs have generally increased the fluvial connectivity by transporting large amounts of sediment and runoff from hillslope to the valley bottom after generating within the lanes and/or collecting from surroundings (Boardman, 2013). Measuring disconnectivity in the process of sediment flux (Ondráčková and Máčka, 2019; Poeppl et al, 2020), hydrological and geochemical transfers (Fuller and Death, 2018; Lemm et al, 2021), multidimensional coupling on hillslopes (Ayoubi et al, 2021) is an emerging field of research in the anthropo-geomorphological investigation. However, most of these studies have overlooked the role of TIs on the alteration of such geomorphic processes, although roads and railways are ubiquitous features in all landscapes.…”