Dataset Information

Forest defoliator pests alter carbon and nitrogen cycles.

ABSTRACT: Climate change may foster pest epidemics in forests, and thereby the fluxes of elements that are indicators of ecosystem functioning. We examined compounds of carbon (C) and nitrogen (N) in insect faeces, leaf litter, throughfall and analysed the soils of deciduous oak forests (Quercus petraea L.) that were heavily infested by the leaf herbivores winter moth (Operophtera brumata L.) and mottled umber (Erannis defoliaria L.). In infested forests, total net canopy-to-soil fluxes of C and N deriving from insect faeces, leaf litter and throughfall were 30- and 18-fold higher compared with uninfested oak forests, with 4333?kg?C?ha-1 and 319?kg?N?ha-1, respectively, during a pest outbreak over 3 years. In infested forests, C and N levels in soil solutions were enhanced and C/N ratios in humus layers were reduced indicating an extended canopy-to-soil element pathway compared with the non-infested forests. In a microcosm incubation experiment, soil treatments with insect faeces showed 16-fold higher fluxes of carbon dioxide and 10-fold higher fluxes of dissolved organic carbon compared with soil treatments without added insect faeces (control). Thus, the deposition of high rates of nitrogen and rapidly decomposable carbon compounds in the course of forest pest epidemics appears to stimulate soil microbial activity (i.e. heterotrophic respiration), and therefore, may represent an important mechanism by which climate change can initiate a carbon cycle feedback.

SUBMITTER: L-M-Arnold A

PROVIDER: S-EPMC5098976 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Forest defoliator pests alter carbon and nitrogen cycles.

L-M-Arnold Anne A Grüning Maren M Simon Judy J Reinhardt Annett-Barbara AB Lamersdorf Norbert N Thies Carsten C

Royal Society open science 20161026 10

Climate change may foster pest epidemics in forests, and thereby the fluxes of elements that are indicators of ecosystem functioning. We examined compounds of carbon (C) and nitrogen (N) in insect faeces, leaf litter, throughfall and analysed the soils of deciduous oak forests (Quercus petraea L.) that were heavily infested by the leaf herbivores winter moth (Operophtera brumata L.) and mottled umber (Erannis defoliaria L.). In infested forests, total net canopy-to-soil flux ...[more]

PMID: 27853551

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Project description:The impact of exotic species on heterogeneous native tropical forest requires the understanding on which temporal and spatial scales these processes take place. Functional tracers such as carbon (?13C) and nitrogen (?15N) isotopic composition in the soil-plant system might help track the alterations induced by the exotic species. Thus, we assess the effects from the removal of the exotic species eucalyptus (Corymbia cytriodora) in an Atlantic forest Reserve, and eucalyptus removal on the alteration of the nutrient dynamics (carbon and nitrogen). The hypotheses were: (1) the eucalyptus permanence time altered ?13C and ?15N in leaves, soils and litter fractions (leaves, wood, flowers + fruits, and rest); and (2) eucalyptus removal furthered decomposition process of the soil organic matter. Hence, we determined the soil granulometry, the ?13C and ?15N in leaves, in the superficial soil layer, and litter in three sites: a secondary forest in the Atlantic forest, and other two sites where eucalyptus had been removed in different times: 12 and 3 months ago (M12 and M3, respectively). Litter samples presented intermediate ?13C and ?15N values in comparison with leaves and soil. In the M3, the greater ?13C values in both litter rest fraction and soil indicate the presence, cycling and soil incorporation of C, coming from the C4 photosynthesis of grassy species (Poaceae). In the secondary forest, the soil ?15N values were twice higher, compared with the eucalyptus removal sites, revealing the negative influence from these exotic species upon the ecosystem N dynamics. In the M12, the leaves presented higher ?13C mean value and lower ?15N values, compared with those from the other sites. The difference of ?13C values in the litter fractions regarding the soil led to a greater fractioning of 13C in all sites, except the flower + fruit fractions in the secondary forest, and the rest fraction in the M3 site. We conclude that the permanence of this exotic species and the eucalyptus removal have altered the C and N isotopic and elemental compositions in the soil-plant system. Our results suggest there was organic matter decomposition in all litter fractions and in all sites. However, a greater organic matter decomposition process was observed in the M3 soil, possibly because of a more intense recent input of vegetal material, as well as the presence of grassy, easily-decomposing herbaceous species, only in this site. Therefore, the dual-isotope approach generated a more integrated picture of the impact on the ecosystem after removing eucalyptus in this secondary Atlantic forest, and could be regarded as an option for future eucalyptus removal studies.

Dataset Information

Forest defoliator pests alter carbon and nitrogen cycles.

Publications

Forest defoliator pests alter carbon and nitrogen cycles.

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