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Stability of Soil Moisture Patterns Retrieved at Different Temporal Resolutions in a Tropical Watershed

Luís Romero Barbosa ORCID logo , Nicholas Borges de Lira ORCID logo , Victor Hugo Rabelo Coelho ORCID logo , Alain Marie Bernard Passerat de Silans ORCID logo , André Nóbrega Gadêlha ORCID logo , Cristiano das Neves Almeida ORCID logo

19/Jun/2019

DOI: 10.1590/18069657rbcs20180236

Graphical Abstract

Graphical Abstract

Highlights

Atlantic Forest soils show specific soil moisture dynamics in tropical watersheds

Mean time-invariant parcel ruled soil moisture variability at large/short time-steps

Time-steps longer than 2 days affected the mean value of soil moisture time-variant parcel

Soil characteristics set apart up/downstream soil moisture in small-scale watershed

Stability of Soil Moisture Patterns Retrieved at Different Temporal Resolutions in a Tropical Watershed

ABSTRACT

Above and underground hydrological processes depend on soil moisture (SM) variability, driven by different environmental factors that seldom are well-monitored, leading to a misunderstanding of soil water temporal patterns. This study investigated the stability of the SM temporal dynamics to different monitoring temporal resolutions around the border between two soil types in a tropical watershed. Four locations were instrumented in a small-scale watershed (5.84 km2) within the tropical coast of Northeast Brazil, encompassing different soil types ( Espodossolo Humilúvico or Carbic Podzol, and Argissolo Vermelho-Amarelo or Haplic Acrisol), land covers (Atlantic Forest, bush vegetation, and grassland) and topographies (flat and moderate slope). The SM was monitored at a temporal resolution of one hour along the 2013-2014 hydrological year and then resampled a resolutions of 6 h, 12 h, 1 day, 2 days, 4 days, 7 days, and 15 days. Descriptive statistics, temporal variability, time-stability ranking, and hierarchical clustering revealed uneven associations among SM time components. The results show that the time-invariant component ruled SM temporal variability over the time-varying parcel, either at high or low temporal resolutions. Time-steps longer than 2 days affected the mean statistical metrics of the SM time-variant parcel. Additionally, SM at downstream and upstream sites behaved differently, suggesting that the temporal mean was regulated by steady soil properties (slope, restrictive layer, and soil texture), whereas their temporal anomalies were driven by climate (rainfall) and hydrogeological (groundwater level) factors. Therefore, it is concluded that around the border between tropical soil types, the distinct behaviour of time-variant and time-invariant components of SM time series reflects different combinations of their soil properties.

Stability of Soil Moisture Patterns Retrieved at Different Temporal Resolutions in a Tropical Watershed

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