Understory structure by season following uneven-aged reproduction cutting:A comparison of selected measures 2 and 6 years after treatment

Rudis, V.A., Thill, R.E., Gramann, J.H., Picone, J., Kalidindi, N. and Tapp e, P.A. 1999. Understory structure by season following uneven-aged reproduc tion cutting: a comparison of selected measures 2 and 6 years after treatme nt. For. Ecol. Manage. 1998. Deciding among cutting practices requires know ledge of forest structure, understory vegetation change, rates of recovery, and resource impacts. We used two field devices (a screenometer and a dens ity board) and digital images of 35 mm photographs to compare measures and document the change in understory vegetation structure in forests following reproduction cutting disturbances. The study area, mostly 70-year old seco nd-growth shortleaf pine-oak (Pinus echinata-Quercus spp.), had an average basal area of 26 m(2)/ha. Treatments retained 13.8 m2/ha in pine and three levels of hardwood basal area. The 21 m(2)/ha treatment retained 33% hardwo od basal area in a scattered condition. One 17 m(2)/ha treatment retained 2 0% hardwoods in a clustered or grouped pattern, and another treatment retai ned 20% hardwoods scattered throughout. A fourth treatment retained no hard wood basal area. When compared with untreated (control) plots, vegetative s creening increased on treated plots relative to untreated plots by degree o f initial cutting disturbance. Both the screenometer and the density board readings distinguished between control and treated plots, but significant d ifferences occurred by season, year, and height above ground. Digital infor mation from scanned images yielded promising results by detecting significa nt differences in the amount of blue color intensity and the proportion of line objects. Color intensities were significantly different by season and year after treatment, that is, lowest in summer and highest in spring, and greater 2 years after treatment rather than 6 years after treatment. Result s indicated that detection of disturbed conditions and recovery following d isturbance varied with the scale and type of measurement. Each device estim ated different structural dimensions. We concluded that assessment and mode ling of understory structure, change, and recovery depended strongly on the cell size of the device used. (C) 1999 Elsevier Science B.V. All rights re served.