Abstract
The study aims to clarify the relationship between soil organic carbon (SOC) and human activity under arid conditions, in the east area of the Nile Delta, Egypt. SOC is one of the critical factors in food production and plays an important role in the climate change because it affects the physio-chemical soil characteristics, plant growth, and contributes to sustainable development on global levels. For the purpose of our investigations, 120 soil samples (0–30 cm) were collected throughout different land uses and soil types of the study area. Multiple linear regressions (MLR) were used to investigate the spatiotemporal relationship of SOC, soil characteristics, and environmental factors. Remote sensing data acquired from Landsat 5 TM in July 1995 and operational land imager (OLI) in July 2018 were used to model SOC pool. The results revealed significant variations of soil organic carbon pool (SOCP) among different soil textures and land-uses. Soil with high clay content revealed an increase in the percentage of soil organic carbon, and had mean SOCP of 6.08 ± 1.91 Mg C ha−1, followed by clay loams and loamy soils. The higher values of SOCP were observed in the northern regions of the study area. The phenomenon is associated with the expansion of the human activity of initiating fish ponds that reflected higher values of SOC that were related to the organic additions used as nutrients for fish. Nevertheless, the SOC values decreased in southeast of the study area with the decrease of soil moisture contents and the increase in the heavy texture profiles. As a whole, our findings pointed out that the human factor has had a significant impact on the variation of soil organic carbon values in the Eastern Nile Delta from 1995 to 2018. As land use changes from agricultural activity to fish ponds, the SOCP significantly increased. The agriculture land-use revealed higher SOCP with 60.77 Mg C ha−1 in clay soils followed by fish ponds with 53.43 Mg C ha−1. The results also showed a decrease in SOCP values due to an increasing in land surface temperature (LST) thus highlighting that influence of temperature and ambient soil conditions linked to land-use changes have a marked impact on surface SOCP and C sequestration.
Highlights
Soil contains the largest stock of organic carbon compared to vegetation and the atmosphere
The results of the change detection from 1995 to 2018, with overall accuracy 93.7% and Kappa Coefficient 0.87, show that along with an increasing agricultural activities in the study area, there was observed an increasing in urban areas of around 18,585 hectares during the 23 years between 1995 and 2018 (Table 1)
The decrease of soil organic carbon pool (SOCP) predominantly refers to an increase of land degradation processes in the east of Nile Delta, and corresponds to the effects of management practices in terms of the use of heavy engines for tillage affecting the soil physical properties such structure and soil porosity in the northern Nile Delta [59,60,61] in the study area reflected by the decomposition of organic material and SOCP (Table 2)
Summary
Soil contains the largest stock of organic carbon compared to vegetation and the atmosphere. In arid and semi-arid regions, low precipitation with strong seasonality is one of the most important controlling factors of the decay and transformation of soil organic matter In these arid conditions, to increase agricultural production (according to the economic and social situations of the settlers), irrigation and mineral additive practices are commonly used, producing as a consequence a reduction of carbon stocks in the soil layers [8]. The use of satellite technologies today can suitably support the decision makers and the development plan processes providing suitable free of charge tools useful for multi-temporal analysis based on the past and the current conditions capturing changes at diverse temporal and spatial scales from a global down to a local level. Geomorphological characteristics and surface features were described based on remote sensing and topographic 1: 10,000 map
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