Continuous soil temperature, specific conductance, and volumetric water content measurements from the Wormherder Creek Active Layer Monitoring Station (ALMS02), McMurdo Dry Valleys, Antarctica (2014-2021, ongoing)

Abstract:

As part of the McMurdo Dry Valleys Long Term Ecological Research (LTER) project, five Active Layer Monitoring Stations (ALMSs) were established throughout Taylor Valley, Antarctica to support new research foci around the thermal-moisture dynamics of soils that may control habitat conditions and faunal responses to seasonal and annual freezing cycles in this ecosystem. Two ALMSs were established adjacent to streams (Green Creek, Von Guerard Stream), with sensors installed through the active layer from the thalweg out to the shoreline and dry soil beyond. Two ALMSs were similarly established adjacent to water tracks (Wormherder Creek, Water Track B) that are zero-order drainages of snow and ice melt that rarely have surface flow. The remaining station was established in dry soil (F6) to serve as an ambient control. ALMSs measure soil temperature, soil moisture (as volumetric water content; VWC), and specific conductance (as electrical conductivity; EC) through the active layer (soil surface down to the frost table) at several locations from the water’s edge to dry soils. This data package contains measurements from the Active Layer Monitoring Station at Wormherder Creek (ALMS02).

LTER Core Areas:

disturbance

Dataset ID:

4021

Associated Personnel:

1177

1178

1179

Short name:

ALMS02_WHC

Data sources:

ALMS02_WHC_EC

ALMS02_WHC_TEMP

ALMS02_WHC_VWC

Methods:

Active Layer Monitoring Stations (ALMSs) are designed to measure soil temperature, soil moisture (as volumetric water content; VWC), and specific conductance (as electrical conductivity; EC) of active layer soils at various depths. At each station, sensors are deployed at 4-5 sites (A-E) in a 1-dimensional vertical orientation. For example, at Green Creek, sites A and B are located near the thalweg, site C is located at the wetted margin, and sites D and E are located in distal soils further from the channel of the stream.

Decagon 5TE sensors are used to measure soil temperature, volumetric water content, and pore water electrical conductivity at specific depths in the soil profile. Each 5TE sensor is wired into a Campbell Scientific AM16/32B 16-Channel Relay Multiplexer, which is connected to a CR1000 Measurement and Control Datalogger. In very dry soils, specific conductance measurements may be unreliable. Furthermore, specific conductance observations in frozen soils are also unreliable. To interpret these data, we suggest looking at coincidentally observed temperature and soil moisture observations. Pore water specific electrical conductivity is measured with an accuracy of 10% and resolution of 0.01 dS/m. Notably, VWC is not calibrated for each sensor so relative changes should only be considered and care should be taken when comparing values between sensors.

K-Type, Duplex Insulated Omega® Thermocouple Wire was cut and insulated at one end to measure soil temperature at several additional depths within each site at each station to complement temperature data recorded by the 5TE sensors. Thermocouples are wired into a Campbell Scientific AM25T 25-Channel Solid-State Thermocouple Multiplexer, connected to a CR1000 Datalogger. Thermocouples measure temperature within a range of -250 to +250°C, at an accuracy of 2% below freezing and 0.75% above freezing, and a precision of 0.001 °C.

Quality Assurance:

These data have not been QA/QC'd, so erroneous values exist, especially in the EC and VWC datasets. These data have not been gap filled so there are missing measurements for particular sensors (indicated by blank cells) as well as missing timestamp values (these entire rows do not exist).

Additional information:

Funding for this project was provided by several grants from the US National Science Foundation for Long Term Ecological Research, most recently under award #OPP-1637708.