Make, Model and/or Version of Sensors or Models and Any Applicable URLs:
The High Intensity Terrestrial Network is comprised of eight sensor sites located in locations throughout New Hampshire ranging from the seacoast to the White Mountains. The sites are comprised of six to eight sensor nodes to account for spatial heterogeneity within the soil environment. Each node contains an automatic chamber used to determine the flux of carbon dioxide (CO2) from the soil due to soil microbial respiration. Paired with each chamber we have three soil sensors installed at the soil surface and 15 and 30 cm below the soil surface, collecting continuous data for soil temperature, volumetric water content (VWC), and electrical conductivity (EC). Other aboveground sensors collect air temperature, barometric pressure, wind speed, wind direction, snow depth, and at some locations precipitation data. We also have soil CO2 probes installed at three nodes per site that can detect the amount of CO2 being produced at depth in the soil profile at15 and 30 cm. These can sample year round even when the ground is covered with snow. Once winter time comes we must shut down the operation of our autochambers and make the switch over to a snow tower. This snow tower can detect the CO2 flux out of the snow pack. By understanding how extreme weather events affect soil properties and processes as well as stream chemistry, we can predict the likely effects of climate change on soils and water quality in the coming decades.
Campbell Scientific CR1000 Datalogger: The soil sensor system is fairly complex and built from many different pieces, requiring a large amount of fabrication work. The main control unit in the system is called a Campbell Scientific CR1000 datalogger. Dataloggers measure sensors that accurately convert environmental change into measurable electrical responses. There is one datalogger per Terrestrial Senor Network Site.
Modem: To transfer data from each individual sensor station we use an Airlink RavenXTV modem. It uses machine to machine data transfer much like a text message to send data over the Verizon cell phone network back to a server at the University of New Hampshire. The data can then be put through a series of quality control checks to ensure the accuracy of the data.
Multiplexers: are used to increase the number of sensors that can be controlled by the datalogger. We use the Campbell Scientific AM16/32B. There are two multiplexers per Terrestrial Sensor Network Site.
Connected to the multiplexer are two different soils sensors used both at the soil surface and within the soil profile.
Autochambers: Soil respiration chambers are custom made by a private contractor called Fin-Landis Techniker. They are aluminum boxes that automatically open and shut to sample CO2 flux using a pneumatic arm powered by a compressor. Once the chamber shuts to sample the soil, a pump pulls the sample into an infrared gas analyzer to quantify the concentration of CO2 being respired by soil microbes from the soil. Each chamber has a temperature sensor inside of it used to help calculate CO2 flux.
Infrared Gas Analyzer (Li-840A): The system samples CO2 flux from soil respiration chambers and snow towers by using two independent control subsystems relying on many different parts to direct flow. One subsystem is pneumatic using a compressor to pressurize a device used to open and shut the chambers. The other uses a pump which pulls samples from the chambers to an analyzer to quantify soil CO2 flux. The analyzer used to quantify the CO2 flux is called an Infrared gas analyzer (IRGA), and the model we use is the Li-840A.
The device used to control the sampling of chambers is a Campbell Scientific SDM-CD16AC Relay Controller. It allows the datalogger to automatically turn valves on and off using a program.
In-situ CO2 Transmitter Probes: To sample the CO2 in the soil profile we have probes installed at three nodes per site, at two depths per node at 15 and 30 cm.
Snow Tower: Is coupled with the snow depth sensor and is used to quantify the CO2 diffusion through the snowpack. It has sampling ports every 10 cm from the soil surface up to 150 cm. It utilizes the existing sampling system of the autochambers when they are shut down for the wintertime. Thermocouple temperature sensors are installed on each sampling level used to help calculate the CO2 flux. This tower and the thermocouples are made in house.
Snow Depth Sensor: Sonar sensor that determines the depth of the snowpack used to determine the CO2 flux from the snowpack in conjunction with the snow tower. To determine the snowpack depth, the sensor uses an ultrasonic sonar beam to determine the distance to the ground. An air temperature sensor is used to increase the accuracy of the depth measurement.
Wind Monitor: Used to determine wind speed and direction which is required to calculate more accurate CO2 diffusion from the ground which is quantified using the in-situ CO2 probes.