Seasonal Dynamics of Physical, Hydraulic, and Physico-Chemical Attributes of the Soil across Altitudinal Gradients in the Alpine Wetlands of Lesotho

Seasonal fluctuations significantly influenced soil physical, hydraulic, and physico-chemical properties in Lesotho’s alpine wetlands, yet these ecosystems remain largely understudied. This study evaluated composite seasonal index and examined soil variation and seasonal changes in soil attributes across altitudes (2500–3155 m a.s.l.), equivalent to wetlands from three sub-catchments (blocks): Khorong and Tenesolo (Senqunyane), Khamoqana and Khalong-la-Lichelete (Sani), and Lets’eng-la-Likhama and Koting-Sa-ha Ramosetsana (Khubelu), during the standard (spring, September 2024) and peak (summer, February 2025) wet seasons. The soil samples were collected in September 2024 (standard) and February 2025 (peak) wet seasons and analyzed for bulk density (BD), saturated hydraulic conductivity (Ksat), infiltration rate (IR), water holding capacity (WHC), texture, pH, electrical conductivity (EC), cation exchange capacity (CEC) and soil organic carbon (SOC) following standard procedures. Soil texture exhibited clear altitudinal trends: sand decreased from 64.97% at lower elevations to 39.79% upslope, whereas silt and clay increased, resulting in sandy-loam at lower and loam at higher sites. Seasonal variations, though subtle, were measurable: sand (± 0.2%), silt (± 1%), clay (± 1.3%), BD (6.8%), Ksat (13%), IR (5.1%), and WHC (2.6%). SOC rose slightly (~ 0.4%) in summer, peaking at Koting-Sa-ha Ramosetsana. Correlation analysis indicated strong negative relationships between sand and both clay and silt, while BD inversely related to IR. Positive associations were observed between WHC and Ksat, and IR correlated closely with SOC. Overall, these results underscore that seasonal hydrological dynamics and elevation jointly shape soil structure, water movement, and carbon storage in Lesotho’s alpine-wetlands, emphasizing their ecological sensitivity and need for targeted conservation.