Study of time dependency of factors affecting the spatial distribution of soil water content in a field-plot

Temporal and spatial variability of water content in soil results from a co mplex interaction of different factors such as duration and frequency of ra infall, soil layering, vegetation, and topography. The objectives of this s tudy were (i) to use a resistant median-polishing scheme to quantify the te mporal variability of a depth and a horizontal location factor in an additi ve model, and (ii) to investigate the lime stability of those two factors a t a detailed temporal scale during different infiltration and redistributio ns cycles. Time series of water content were measured at 5 depths and 12 lo cations along a transect of 6 m using Time Domain Reflectometry (TDR). Meas urements were repeated every 2-hours for 168 days under natural boundary co nditions. At each time step, the mean water content of the soil profile. 5 depth factors and 12 location factors were estimated. The time series of th ese factors were qualitatively interpreted and related to the atmospheric a nd prevailing soil conditions. It was found that micro-heterogeneity plays an important role, even at this small plot-scale. The relative contribution s of the factors were dependent on the antecedent soil moisture conditions. Also, the ratio of the deterministic variance, i.e., variance explained by the deterministic factors, of water content to the observed variance is va riable in time, (C) 2001 Elsevier Science Ltd. All rights reserved.