Soil microbial community functioning as indicators of alpine soil health in the northern Maloti–Drakensberg, South Africa

Abstract

The alpine soils of the northern Maloti–Drakensberg site are fundamental to carbon (C) sequestration, biodiversity conservation, and water provisioning, yet remain vulnerable to degradation from grazing and tourism pressures. Soil microbial activity is central to alpine soil functionality through its influence on nutrient cycling, organic matter (OM) turnover and structural stability, but microbial community patterns in the alpine zones of southern Africa remain poorly understood. This study provides the first coordinated quantitative characterisation of soil microbial and physicochemical properties on the Amphitheatre summit of the uThukela catchment, thereby establishing a baseline for long-term soil health monitoring. Thirty topsoil samples were analysed for monitoring their physical (texture, bulk density, aggregate stability), chemical (pH, soil organic carbon or soil organic carbon [SOC], total C, total N and active C) and biological (microbial activity and community-level physiological profiling) attributes. The soils were uniformly acidic (pH 4.9), sandy loam in texture, and exhibited relatively low bulk density (1.01 g cm−3) but high SOC (9.8%). Soil organic carbon, active C, total N and microbial activity showed strong correlation, indicating consistent links between organic matter pools and microbial functioning. Community-level profiling further distinguished three microbial functional groups, primarily driven by variation in SOC, active C and microbial activity, rather than by soil forms or physical properties. The study indicated that SOC and total N are the most informative soil indicators for evaluating microbial functionality in alpine soils of the northern Maloti-Drakensberg. Conservation implications: The baseline generated in this study enables the future detection of soil changes in response to land use or climate pressures in the northern Maloti–Drakensberg. Soil organic carbon and total N emerged as key indicators of microbial community functioning, underscoring the importance of maintaining soil organic matter through sustainable grazing and tourism management to enhance the resilience of high-altitude ecosystems.