The Role of Surface Topography in Temporal Stability of Field-Scale Patterns of Soil Water Content
Abstract
Analysis of temporal stability (TS) of soil water (SWC) is commonly used to select monitoring locations in the field that reliably represent field-averaged SWC. TS is known to be affected by soil properties, vegetation, and surface and subsurface hydrology, which in turn are affected by topography. The effects of individual factors are well documented, however the effect of topography, which includes interaction of all individual factors on TS, is less studied. Objectives were: (i) to study the temporal patterns of soil water content at different topographical positions; (ii) to test whether these patterns persist for seasons with different vegetation and weather conditions; (iii) to test the association of TS SWC with soil properties, vegetation, and topographical position. The experimental field under corn-soybean rotation with cover crops (rye) was located in Mason, Michigan (US). Soil water content was monitored for the duration of five seasons between 2014 and 2016 at four topographical positions: summit (SU), slope (SL), dry depression (DD), and flooded depression (DF). Soil texture varied across 3 textural classes (lS, sL, and scL) in 20 monitoring locations. The regression tree technique was used to evaluate the importance of topographical position, season, vegetation, and S/C ratio on the standard deviation of the mean relative difference of SWC measured in individual locations from field averaged SWC for each time moment (SDRD). The S/C ratio was the most important predictor of SDRD at 20 cm depth, followed by season, crops, and topography, indicating the importance of soil hydraulic properties on TC of SWC in the top soil layer. At 40 cm depth the importance of factors decreased in the order season - crops - topography - S/C ratio, while for 60-cm depth the order was topography - season - S/C ratio - crops. The importance of topography for TS of SWC in our study increased with the depth, indicating that temporal instability of SWC patterns in the top soil layers is mostly due to high variability in S/C ratio, which affects soil hydraulic properties and non-uniform patterns of water influxes into the soil due to overland water flow. The deeper soil layers were less affected by the overland fluxes and infiltration, and thus more temporally stable in terms of SWC patterns.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H21K1819F
- Keywords:
-
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0438 Diel;
- seasonal;
- and annual cycles;
- BIOGEOSCIENCESDE: 1807 Climate impacts;
- HYDROLOGYDE: 1836 Hydrological cycles and budgets;
- HYDROLOGY