Do natural disturbances or the forestry practices that follow them convert forests to early‐successional communities?

Abstract

Stand-replacing natural disturbances in mature forests are traditionally seen as events that cause forests to revert to early stages of succession and maintain species diversity. In some cases, however, such transitions could be an artifact of salvage logging and may increase biotic homogenization. We present initial (two-year) results of a study of the effects of tornado damage and the combined effects of tornado damage and salvage logging on environmental conditions and ground cover plant communities in mixed oak-pine forests in north central Mississippi. Plots were established in salvage-logged areas, adjacent to plots established before the storm in unlogged areas, spanning a gradient of storm damage intensity. Vegetation change directly attributable to tornado damage was driven primarily by a reduction in canopy cover but was not consistent with a transition to an early stage of succession. Although we observed post-storm increases of several disturbance indicators (ruderals), we also observed significant increases in the abundance of a few species indicative of upland forests. Increases in flowering were just as likely to occur in species indicative of forests as in species indicative of open woodlands. Few species declined as a result of the tornado, resulting in a net increase in species richness. Ruderals were very abundant in salvage-logged areas, which contained significantly higher amounts of bare ground and greater variance in soil penetrability than did damaged areas that were not logged. In contrast to unlogged areas severely damaged by the tornado, most upland forest indicators were not abundant in logged areas. Several of the forest and open-woodland indicators that showed increased flowering in damaged areas were absent or sparse in logged areas. Species richness was lower in salvage-logged areas than in adjacent damaged areas but similar to that in undamaged areas. These results suggest that salvage logging prevented positive responses of several forest and open-woodland species to tornado damage. Anthropogenic disturbances such as salvage logging appear to differ fundamentally from stand-level canopy-reducing disturbances in their effects on ground cover vegetation in the forests studied here and are perhaps more appropriately viewed as contributing to biotic homogenization than as events that maintain diversity.

Assessing the ecological impacts of biomass harvesting along a disturbance severity gradient

“…Future studies should confirm whether integrated, continuous DSI applies similarly between natural and managed disturbances, particularly in terms of indicator species or functional traits that may be more critically influenced by disturbance type than broad community structure (Brewer et al. ). Not all studies will have the luxury of the predisturbance data afforded by planned experiments, such as those used in this study, but the use of reconstructions of living biomass from damaged stems may provide alternative proxies for levels of disturbance severity in a given area where such collections do not exist (cf.…”

“…Few studies have applied a continuous approach to quantifying multi‐dimensional forest disturbances (Roberts , Peterson and Leach , Brewer et al. , Royo et al. ).…”

Effects of Management Intervention on Post-Disturbance Community Composition: An Experimental Analysis Using Bayesian Hierarchical Models

“…Our results suggest that a carefully monitored harvest prescription can reduce potential fuel loads [5] in beetle-killed forests without changing avian species richness or reducing occupancy rates of individual species. We suspect that our results arise from the comparatively less severe effects on habitat structure of both the beetle outbreak and the pay-as-cut salvage logging, as opposed to clearcut salvage logging following other disturbance types [6], [51], [52]. For example, the beetle outbreak affected live trees and did little damage to other habitat features, such as understory shrubs.…”

Response of the Invasive Grass Imperata cylindrica to Disturbance in the Southeastern Forests, USA

“…However, several examples demonstrate that I. cylindrica control is a problem in areas where the overstory has been removed [22]. Other studies of exotic grass invasion indicate that overstory removal, particularly salvage logging following disturbance, can increase abundance of exotic species [23][24][25].…”