Distributed Temperature Profiling (DTP): development and application for dense spatiotemporal investigation of how landscape position, vegetation and snow modulate soil thermal and hydrological regimes

Abstract:

Quantifying ecosystem soil thermal parameters and regimes, and their links with energy and water fluxes as a function of landscape position is particularly challenging yet critical for predicting the storage and flux of carbon and water in a changing climate. This is particularly so for Arctic and mountainous regions. To address this challenge, we developed a novel approach called Distributed Temperature Profiling (DTP) for large scale acquisition of soil and/or snow temperature data with unprecedented spatial density and simplicity in data management and processing. The DTP system, which involves a network of vertically-resolved temperature probes (>10 sensors/probe) and accompanying ultra-low-power data acquisition systems, enables low production and assembly cost, high measurement accuracy and flexibility for deployment in various environments. In addition, we performed numerical and in-situ assessments of the system performance, and developed numerical methods to estimate snow thickness and soil thermal properties from the temperature time series. We deployed the system at about 100 locations in an Arctic watershed located in a transitional landscape on the Seward Peninsula (Alaska), and along two hillslopes in the mountainous upper East River watershed in Colorado.

We found that the DTP systems enabled improvements in quantifying and disentangling the influence of various land surface properties on soil thermal regimes, as well as in estimating soil constituents influencing thermal properties. Results indicate significant spatial variability in the soil freeze-thaw timing and amplitude, which was primarily driven by landscape characteristics (including slope, aspect and vegetation) influencing the ground surface energy balance and the snowpack properties, and by pre-winter soil moisture conditions. Temperature time series also enabled the identification of significant and heterogeneous soil thermal-hydrological responses to snowmelt and intense rainfall events, and the significant link between landscape position and soil physical characteristics. The obtained information is expected to be useful for improving predictions of soil hydro-biogeochemical dynamics.