Soil ecosystem function loss under traditional gold mining landscapes in Tigray, Ethiopia: A function‐based soil quality indices approach

Abstract

Abstract Traditional gold mining (TGM) contributes to land degradation, yet its impacts on key soil ecosystem functions remain poorly understood. This study investigated soil degradation caused by TGM in Tigray, Ethiopia, to identify sensitive soil quality indicators and develop function‐based soil quality indices (SQIs), compare soil quality scoring functions, and assess the extent of soil degradation caused by TGM across different slopes and depths. A total of 192 (96 disturbed and 96 undisturbed) soil samples were collected across three slope positions, two depths, and mined and unmined counterparts from three TGM‐affected locations. Out of 30 potential indicators, 11 were selected through principal component analysis to represent buffering and detoxification, nutrient cycling, structural stability and erosion resistance, and water–air–solute movement soil functions. SQIs showed significant declines in soil function due to TGM, especially on upper slopes and deeper layers. Over 52% of mined soils are classified as very low SQIs grades, with degradation indices reaching up to 80% in upper slopes. Significant impacts included heavy metal buildup (Hg, Cu, Fe), nutrient loss (cation exchange capacity, Mg 2 + , P), and poor soil structure and erosion tolerance, explained by low mean weight diameter and soil organic carbon, along with imbalanced water‐solute‐air movement caused by high soil compaction, low moisture content, and dominant coarse texture in the mined soils. The threshold‐based nonlinear scoring function proved more sensitive (sensitivity: 16.03) than the mean‐based approach (5.07), preferably identifying degradation patterns. These findings confirm that function‐based SQIs are significant for monitoring TGM‐related soil impacts and the importance of slope‐specific post‐mining restoration strategies.