Litter depth changes seasonally, so acoustic measurements must record sampling date.

Evidence

Site 8, maple saplings: Unlike the others, this site was examined late in the fall and the 5 cm thick loose ground cover consisted of this year’s leaves that had dropped since the summer acoustic measurements had been conducted. There was a 2.5 cm thick packed ground cover below and these loose layers with the highly organic layer made up a well-matted spongy layer. The next 15 cm of dark silty soil contained some roots and gravelly material. — Donald G. Albert, Michelle E. Swearingen, Frank E. Perron, and David L. Carbee, Low Frequency Acoustic Pulse…, 118

Categorization

• QUESTION: Were the summer acoustic measurements systematically biased by leaf-on versus leaf-off ground conditions at this site versus the others?
• XREF: Connects to the broader field-methods problem of measuring a dynamic medium at a single snapshot in time, as in forest soil or snowpack surveys.