Seasonal changes in surface bulk density and saturated hydraulic conductivity of natural landscapes

Abstract

Soil surface bulk density ( ρ b ) and saturated hydraulic conductivity ( K s) control many land‐surface processes such as water flow, chemical transport and soil erosion. The objective of this study was to examine seasonal changes in surface ρ b and K s in natural landscapes with few human activities. Measurements of ρ b and K s were made on undisturbed soil samples taken from the soil surface (0–0.05 m) five times from October 2007 to March 2009 along four natural transects in a small watershed on the Chinese Loess Plateau. The transects represented four landscapes with different vegetation and soil typical in this region. Results showed that ρ b and K s varied seasonally. Temporal changes in K s generally followed the temporal patterns of ρ b . According to the mean values of all landscapes, bulk density decreased by 1.6 and 1.1% and log 10 ‐transformed K s (Log 10 K s) increased by 11.0 and 5.8% from October 2007 to March 2008 and from October 2008 to March 2009, respectively; bulk density increased by 2.1% and Log 10 K s decreased by 4.9% from March to June in 2007; from June to October in 2007, bulk density decreased by 1.3% while a slight increase (1.4%) in Log 10 K s was observed. Both landscape and time significantly influenced ρ b and K s, and K s was more susceptible to temporal change than ρ b . Spatial patterns of ρ b and K s did not change significantly with time. Saturated hydraulic conductivity measurements taken in different seasons can affect runoff simulation results, and K s data measured in spring may result in underestimation of runoff in a rainy season.