Regeneration Success and Plant Species Diversity of Allegheny Hardwood Stands After Roundup Application and Shelterwood Cutting

Abstract

Abstract The presence of desirable regeneration and plant species diversity was studied in five Allegheny hardwood stands before and for 7 yr after application of Roundup herbicide and shelterwood cutting to remove interfering understories of hayscented and New York fern, striped maple, and beech and to establish desirable hardwood regeneration. In each of five 20 ac stands, 10 ac were sprayed with 1 lb ai (active ingredient)/ac of Roundup in August 1979; the remaining 10 ac were unsprayed. The entire 20 ac stand received a shelterwood seed cut the following winter. On treated plots, fern was reduced from 57% stocking before treatment to 7% 1 yr after treatment; striped maple and beech stocking was reduced by 16% during the same time. By the fourth year after treatment, regeneration stocking of desirable hardwood species had doubled on treated plots but remained unchanged on untreated control plots. Species diversity was measured by species richness, three diversity indices--Berger-Parker, Margalef and Shannon, and index-free diversity ordering. Neither the herbicide treatment nor the shelterwood seed cut had a statistically significant effect on species richness of either woody species or herbaceous species groups. Nor was there a significant effect of treatments on woody species diversity as measured by the three diversity indices. Index-free diversity ordering showed. (1) a trend toward increase in less common species on Roundup-treated areas, and (2) the diversity of herbaceous species groups was higher in all 7 yr after treatment with Roundup. Values of the three diversity indices were higher for herbaceous species on Roundup-treated subplots for 2 to 7 yr after treatment. Much of this increase resulted from germination of seed bank grasses, sedges, and Rubus spp. With the qualification that long-term and current browsing by deer has impoverished the flora of the Allegheny hardwood forest, diminishing potential treatment effects, the study demonstrated that Roundup treatment aided desirable regeneration establishment, did not have a negative impact on woody species or herbaceous species group diversity, and may have increased diversity of herbaceous species. North. J. Appl. For. 11(4): 109-116.