3.5 Broader applications and considerations
The methods we present are relevant and applicable to temporary lentic
habitats in a wide range of regions, particularly where logistical
challenges constrain the data available for hydroperiod monitoring. For
example, temperature sensor-derived hydroperiod inference may be
particularly useful for ponds or wetlands that can have high canopy
cover (e.g., some Carolina bays (Sharitz, 2003) or vernal pools (Brooks,
2004)) or other considerations that may make remote sensing difficult,
particularly across multiple sites. Temperature sensors may also be
helpful in regions where drone activity is discouraged or prohibited,
thus limiting targeted, fine-scale aerial data acquisition. This
includes national parks, wildlife sanctuaries, or areas where drone
flight is otherwise prohibited (for example, drone operation is not
logistically feasible in our study region due to restrictions by the
United States Border Patrol). Our proposed methods are relatively
low-cost and low-maintenance, making them accessible for even
small-scale research grants. The long battery life of the sensors and
high durability of the design make them ideal for deploying in remote
areas. However, we suggest that users visit deployment sites at least
once a year, particularly before major seasonal inundation events.
Some scenarios may necessitate modifications to the current design,
including components and deployment. For example, complex bathymetry of
wetlands may call for the use of more than one temperature sensor to
detect hydroperiod inundation, particularly when distinct areas of the
temporary habitat have meaningful ecological differences (Chandler,
2017). If longer battery life is desired, the temporal resolution of
measurements could also be adjusted to capture temperature data in less
frequent intervals. Additionally, users may consider alternative sensor
designs. For example, conductivity sensors offer an alternative to
temperature loggers. However, custom modifications required to create
conductivity sensors can be time-consuming or, if outsourced, may result
in units that are >2 times the cost of temperature loggers.
Additionally, conductivity sensors may suffer from the same issues
related to poor or imprecise detection of drying patterns due to water
trapped in sediments. Temperature measurements offer data that are
biologically meaningful (temperature as well as presence/absence of
water) and that may address multiple needs depending on the objectives
of a study. Pressure transducers would likely capture drying dynamics
more accurately and are available for as low as ~$300
per sensor (e.g., Onset HOBO Water Level Data Logger, U20L-01). However,
the physical dimensions of pressure transducers would require
modifications to the current rugged housing unit design, and the
additional cost would result in approximately a four-fold reduction in
the number of sensors obtained for the same budget. An additional
consideration is the ability of sensors to withstand extreme
temperatures. The temperature sensors in our design have a range of -20
to 50°C in water; anticipated temperatures outside this range would
likely necessitate a different sensor model and may be an important
consideration for high-latitude study regions. Finally, deployment
methods for the housing unit and sensor may need to be modified
depending upon the substrate of the habitat. For example, mud or other
soft sediment may require a T-post or similar support structure rather
than buried concrete ties depending upon the depth of the soft
substrate.