Mapping spatial variability of hydric soil properties to delineate Khalong-la-lithunya wetlands

Abstract

Spatial variability in wetland soils provide insight into underlying ecosystem processes and may itself give an indication of wetland condition. The study was conducted to characterise and delineate soil variability of wetlands of Khalong-la-Lithunya from hydric soil properties. Sampling was carried on three sub catchments within Khalong-la-Lithunya catchment. In each sub catchment soil samples were dug at 100m interval along three transects that were 200m apart. Detailed soil profile description of 36 pits was done following USDA-NRCS (2010) manual. Soil samples were collected to the depth of 90 cm at 15 cm interval and analyzed for soil organic carbon (SOC), Base Cations (Ca2+, Mg2+, Na+, K+) and Cation Exchange Capacity (CEC), available Phosphorus (Av-P), available Nitrogen (Av-N), Soil pH, percentage sand, clay and silt. Mean soil properties were 3.5 mg/kg Av-p, 3.0 mg/kg Av-N, 28.3 % SOC, 5.1 pH, Bulk density 0.7 g/cm3 and the texture is sandy. The means base cations were 2.8, 1.8, 7.9 and 2.3 cmol/ kg for Na, K, Ca and Mg, respectively and CEC 82.5 cmol/kg. Av-P was the most variable property with CV ranging from 115 and 162 % in different soil depths while pH was the least variable with CV ranging from 6 and 12 %. The Nugget/Sill ratios were less than 56 %, indicating random heterogeneity. The semivariograms indicated moderate spatial dependence (25 < DSD ≤ 75%) for soil properties including SOC, Av-P, Av-N, pH and sand. Most properties indicate moderate spatial dependence and hence easily managed. Chemical properties were more variable than physical properties.