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In situ disdrometer calibration using multiple DSD moments

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Lane J. E. , Kasparis T. , Metzger P. T. , Jones W. L.

tom Vol. 62, no. 6

1450--1477

In situ calibration is a proposed strategy for continuous as well as initial calibration of an impact disdrometer. In previous work, a collocated tipping bucket had been utilized to provide a rainfall rate based ~11/3 moment reference to an impact disdrometer’s signal processing system for implementation of adaptive calibration. Using rainfall rate only, transformation of impulse amplitude to a drop volume based on a simple power law was used to define an error surface in the model’s parameter space. By incorporating optical extinction second moment measurements with rainfall rate data, an improved in situ disdrometer calibration algorithm results due to utilization of multiple (two or more) independent moments of the drop size distribution in the error function definition. The resulting improvement in calibration performance can be quantified by detailed examination of the parameter space error surface using simulation as well as real data.

Cavity roost site availability and habitat use by bats in different aged riparian cottonwood stands

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Swystun M. B. , Lane J. E. , Brigham R. M.

nr 1

Riparian forests provide important roosting habitat, abundant prey and access to drinking water for many bat species but to date there has been little research on the differential quality of habitats within riparian areas. We quantified the density of potential roost cavities in three age classes (i.e., young: ca. 20 years, mature: ca. 60 years, and old: ca. 100 years) of riparian cottonwood (Populus deltoides) forest stands. Bat activity was also sampled using acoustic detectors in one representative stand of each age class. Stands were situated along an 80 km stretch of the Missouri River in southeastern South Dakota and northwestern Iowa, USA. We predicted the highest density of potential roosts and the highest activity of bats to occur in the oldest age class. Contrary to our predictions, and previous work in aspen dominated upland sites, we found that the density of potential roosts was not significantly different between mature and old stands. However, there were no potential roosts in young stands. Data from guano traps verified the use of a number of cavities in both mature and old stands. Both commuting and foraging activities were highest in the mature, relative to the old and young stand. In total, our data indicate that mature and old stands represent high quality roosting habitat, with the mature being used preferentially for commuting and foraging. Trees in the oldest stands, however, are nearing the end of their lifespan and falling. Younger cohorts must therefore be retained for future recruitment of natural cavities.