Figure 5

Time course of half-hourly soil moisture at 0.05 m and 0.15 m depths and at two locations (center and near the edge) under a slash pile during the April 2004 experimental burn at Manitou Experimental Forest. These data were obtained using a specially designed high-temperature TDR (Zostrich Geotechnical; Pullman, Washington, USA). The design of this particular probe is fairly standard, but the material used to house the steel needles and the connectors attaching them to the coaxial (data/signal) cables had a much higher melting temperature than normal. Additionally, those external portions of the coaxial cables that were likely to be exposed to high temperatures were wrapped in silicon tape. The data gaps at the center location result from eliminating some extremely noisy data during the burn. The cause of this noise is not known, but we speculate that it could have resulted from (1) sensor damage, which was confirmed for at least one probe (at 0.15 m) during laboratory tests performed several months after it had been retrieved from the field, or (2) change in the internal impedance of the TDR probes due to sensor warming in the presence of soil moisture. Note that these data include an empirical correction for temperature effects on the TDR measurements (see Appendix). Consequently, some of the variability in the measured soil moisture during the burn is a result of inaccuracies of the corrections.