Abstract
Outbreaks of forest pests increase with climate change, and thereby may affect microbial communities and ecosystem functioning. We investigated the structure of phyllosphere and soil microbial communities during defoliation by the nun moth (Lymantria monacha L.) (80% defoliation) and the pine tree lappet (Dendrolimus pini L.) (50% defoliation) in Scots pine forests (Pinus sylvestris L.) in Germany. Ribosomal RNA genes of fungi and bacteria were amplified by polymerase chain reaction (PCR), separated by denaturing gradient gel electrophoresis (DGGE), and subsequently sequenced for taxonomic assignments. Defoliation by both pests changed the structure of the dominant fungal (but not bacterial) taxa of the phyllosphere and the soil. The highly abundant ectomycorrhizal fungal taxon (Russula sp.) in soils declined, which may be attributed to insufficient carbohydrate supply by the host trees and increased root mortality. In contrast, potentially pathogenic fungal taxa in the phyllosphere increased during pest outbreaks. Our results suggest that defoliation of pines by insect pest, change the structure of fungal communities, and thereby indirectly may be contributing to aggravation of tree health.
Highlights
Over the last decades, biotic disturbances like insect outbreaks increased dramatically worldwide [1]
Ordination analysis as well as manual reviewing of denaturing gradient gel electrophoresis (DGGE) profiles revealed no significant differences between infested and control plots in samples under insect outbreaks at any sampling date
The fungal community of the phyllosphere showed well separated clustering between infested and uninfested control forest plots during the main period of defoliation in late May compared to early May and October 2014 and 2015 (Figure 1)
Summary
Biotic disturbances like insect outbreaks increased dramatically worldwide [1]. There is evidence that increasing intensity, frequency, duration, and extent of insect outbreaks are closely related to climate and global change [1,2]. Pest insects like the nun moth (Lymantria monacha L.) can benefit from these changing environmental conditions [3]. The impacts of forest pest outbreaks on microbial community are not well understood. Our knowledge of the composition, diversity, and function of phyllosphere microbial communities expanded by the use of culture-independent methods like denaturing gradient gel electrophoresis (DGGE) [8]. DGGE enables the monitoring of dominant taxa in a large number of Forests 2017, 8, 316; doi:10.3390/f8090316 www.mdpi.com/journal/forests
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