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Journal of Environmental Science and Health, Part B: Pesticides, Food Contaminants, and Agricultural Wastes Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/lesb20
Structural changes in soil communities after triclopyr application in soils invaded by Acacia dealbata Link a
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Pablo Souza-Alonso , Alejandra Guisande & Luís González
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Department of Plant Biology and Soil Science, University of Vigo, Vigo, Spain Published online: 20 Jan 2015.
Click for updates To cite this article: Pablo Souza-Alonso, Alejandra Guisande & Luís González (2015) Structural changes in soil communities after triclopyr application in soils invaded by Acacia dealbata Link, Journal of Environmental Science and Health, Part B: Pesticides, Food Contaminants, and Agricultural Wastes, 50:3, 184-189, DOI: 10.1080/03601234.2015.982419 To link to this article: http://dx.doi.org/10.1080/03601234.2015.982419
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Journal of Environmental Science and Health, Part B (2015) 50, 184–189 Copyright © Taylor & Francis Group, LLC ISSN: 0360-1234 (Print); 1532-4109 (Online) DOI: 10.1080/03601234.2015.982419
Structural changes in soil communities after triclopyr application in soils invaded by Acacia dealbata Link PABLO SOUZA-ALONSO, ALEJANDRA GUISANDE and LUIS GONZALEZ
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Department of Plant Biology and Soil Science, University of Vigo, Vigo, Spain
Triclopyr is a commonly used herbicide in the control of woody plants and can exhibit toxic effects to soil microorganisms. However, the impact on soils invaded by plant exotics has not yet been addressed. Here, we present the results of an 18-month field study conducted to evaluate the impact of triclopyr on the structure of fungal and bacterial communities in soils invaded by Acacia dealbata Link, through the use of denature gradient gel electrophoresis. After triclopyr application, analyses of bacterial fingerprints suggested a change in the structure of the soil bacterial community, whereas the structure of the soil fungal community remained unaltered. Bacterial density and F:B ratio values changed across the year but were not altered due to herbicide spraying. On the contrary, fungal diversity was increased in plots sprayed with triclopyr 5 months after the first application. Richness and diversity (H´) of both bacteria and fungi were not modified after triclopyr application. Keywords: Soil microbes, herbicide, plant invasion, community structure, DGGE.
Introduction Triclopyr is a pyridine-based herbicide frequently used for the control of woody plants and annual and perennial broadleaf weeds.[1] In the United States and Europe, within the main synthetic herbicides used to manage noxious weeds, pyridine-based herbicides such as triclopyr is commonly used, but the use of picloram or clopyralid is also noticeable. Effective and commonly used since 1960s, it is mainly during the last 5 years that several works have been carried out successfully applying triclopyr at foliar level,[2–4] directly applied at barks[5] or in combination.[6] Despite the effectiveness of triclopyr in managing exotics, the impact produced by its application on soil community structure has rarely been addressed[7] and therefore, its effects on non-target microorganisms are still unclear. Moreover, to our knowledge, the effect of triclopyr in the structure of soil communities under invasive processes has not yet been described. Due to their extraordinary importance, disturbances of microbial communities ensure several key ecological processes in soil, such as organic matter degradation and nutrient cycling, which could harmfully alter soil fertility and sustainable agricultural productivity.[8]
Address correspondence to Pablo Souza-Alonso, Department of Plant Biology and Soil Science, University of Vigo, Vigo 36310, Spain; E-mail:
[email protected] Received August 13, 2014.
Herbicide triclopyr has been effectively employed to manage even Acacia dealbata L. invasions.[9,10] Native from Australia, this aggressive invader is currently threatening many areas of the world.[11–13] Moreover, the entrance of A. dealbata in a new ecosystem entails differences in soil community structure and functionality at different levels.[14,15] However, as far as we know, the function of soil microbial community is not affected when triclopyr is applied solely at recommended doses.[10] Therefore, the aim of this study was to assess the shortterm and long-term responses of the structure of bacterial and fungal community exposed to triclopyr in soils invaded by A. dealbata. The assessment of microbial community structure was carried out through the use of denaturing gradient gel electrophoresis (DGGE), a very useful technique in ecotoxicology to analyze the variation of microbial community structures at a much higher resolution in comparison to conventional isolation techniques.[16]
Material and methods Study site and experimental design The study was carried out between April 2010 and September 2011. The site location, soil type, climate conditions, and plant composition are properly described in SouzaAlonso et al.[10] Experimental assay comprised of three different patches invaded by A. dealbata, separated at least 100 m from each other. At each invaded patch, three plots
Structural changes in soil communities after triclopyr application in soils invaded by Acacia dealbata Link 185
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(1 £ 1 m2) in which triclopyr would be sprayed and three untreated plots (control plots) were disposed. Plots with similar plant density, orientation, and adequately distanced (>1 m apart) were randomly placed in each A. dealbata patch. Triclopyr was applied in the TRIDENT formulation (Fig. 1). Prior to the field application, triclopyr was diluted (1%) and sprayed twice: in spring (April 2010) and in early autumn (Sept 2010), coinciding with the active growth periods of A. dealbata at this latitude.[11] Microbial community structure was monitored immediately before herbicide spraying and 3 weeks after triclopyr spraying, during the active period of herbicide (May 2010 and Oct 2010). To explore possible long-term effects of triclopyr, community structure was also monitored 1 year after the final herbicide application (Sept 2011).
Microbial community structure At each plot, a minimum of 10 soil sub-samples were collected to form a composite sample. The same soil collection was repeated for the different sampling dates. Samples were maintained at 4 C and once in the laboratory were freshly sieved (
