Search

Herbicides are commonly used in forestry to enhance conifer tree growth by reducing the abundance of competitive, undesired, early successional species. Reducing the abundance of understory species could also lead to changes in community composition that need to be documented to aid the understanding of any downstream ecosystem changes. We examined the effects of glyphosate-based herbicides on the abundance, diversity, and community composition of the understory vegetation community of forests located in the temperate-boreal transition zone. We sampled 37 blocks in two ecoregions of the Acadian Forest in eastern Canada that were harvested over the last 15 years. Species richness, Shannon's diversity, or evenness did not differ among blocks with different herbicide history. However, community composition differed between the non-herbicide and herbicide blocks in both ecoregions. Overall, 26.5% of the plant community variation was explained by the factors herbicide use (10.6%), Biomass Growth Index/site quality (8.6%), time since harvest (3.6%), and ecoregion (1.7%). We found 16 indicator species that differentiated the non-herbicide (9 species) and herbicide blocks (7 species). Indicator species for non-herbicide blocks included two blueberry species, three shrubs (two flowering), and two ferns, whereas indicator species for herbicide blocks were largely perennial forbs. Together, our results indicate that herbicide use does not alter species richness but does reduce shrub abundance, a change that persists throughout the 10 years post-herbicide application captured in our study. The reduced shrub layer likely leads to other changes in the plant community. Herbicide use is associated with subtle changes to the understory plant community, and these changes are missed when only alpha diversity is used to examine the effects of herbicides use on community composition. [ABSTRACT FROM AUTHOR]

Pesticides have been used in Canada since 1945 as part of large‐scale aerial spray applications to control insect pests on forested lands. Some of the pesticides used historically were efficacious, nonselective, persistent, and have led to serious impacts on the environment. A well known, and extensively documented example is the large‐scale aerial spray programs in New Brunswick, Canada. From 1952 to 1993, 97% of the 6.2 million ha of the forested lands of New Brunswick were treated with at least one application of one insecticide, the majority of which were applied to control outbreaks of eastern spruce budworm (Choristoneura fumiferana). The most well known insecticide was dichlorodiphenyltrichloroethane (DDT), applied from 1952 to 1968, which still persists in treated soils and adjacent water bodies, and caused the individual and cumulative ecosystem effects that can still be measured today. The insecticides that replaced DDT were nonpersistent and unlikely to be found today. However, during the years of application some of the insecticides were likely to have impacted local ecosystems to some degree. To aid future studies on the efficacy and environmental impact of these insecticides we created a digital spatial data set of known pesticide application in New Brunswick forestry from 1952 to 1993. The data set includes active ingredient, formulation, application rate, tank mix, aircraft type, and other ancillary information. The current version of the data is available on the New Brunswick Department of Natural Resources and Energy Development, GIS Open Data Page and in the supplemental material. Use of the data set for academic and educational purposes is encouraged, provided that both this data paper and the data source are properly cited; the Government of New Brunswick should be acknowledged as the data source (Open Government License http://www.snb.ca/e/2000/data-E.html). [ABSTRACT FROM AUTHOR]