Response of the Understory to Low Intensity Prescribed Burning or Mechanical and Herbicide Treatment in a Northern Mesic Eastern White Pine (Pinus Strobus L.) Forest in the Menominee Nation, Wisconsin

Abstract

This study describes understory effects four and five growing seasons following four low intensity prescribed burns and three mechanical and herbicide treatments. Two, 150 year old northern mesic eastern white pine (Pinus strobus L.) dominated stands were sampled to compare effects of mechanical and herbicide (M+H) treatments that occurred in late 2002 and low intensity prescribed burns that occurred in 2003. Vegetation was sampled in spring and summer of the fourth and fifth growing seasons after the treatments. Density and composition of saplings; average cover, richness and diversity of understory vegetation; and density and composition of arboreal seedlings were calculated in treated units and controls. The propagule bank of the burn units was also sampled in the fourth growing season following the burns. Comparisons were made with pre-treatment data collected using the same methods pre-treatment and for three growing seasons post treatment. The control treatment had significantly greater density of saplings per hectare than burn and M+H treatments (p =0.01). Understory richness, diversity and average cover were greatest on prescribed burn treatments. There were not significant effects on richness or cover in different burn intensities. Propagule bank richness and density were not significantly affected by the burn, although composition was altered. Arboreal seedling density was greater on M+H treatments but 77% of the regeneration was red maple (Acer rubrum L.) at the end of the study period. The M+H treatments were more severe than prescribed burns, but did not result in the most desirable regeneration. Results of this study show that there are important differences in disturbance effects on the understory and propagule bank for at least five growing seasons following prescribed burning and herbicide and mechanical treatment.