Insect Defoliation and Nitrogen Cycling in Forests

Lovett, Gary M.; Christenson, Lynn M.; Groffman, Peter M.; Jones, Clive G.; Hart, Julie E.; Mitchell, Myron J.

doi:10.1641/0006-3568(2002)052[0335:idanci]2.0.co;2

Cited by 229 publications

(179 citation statements)

References 29 publications

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“…With respect to the direct annual uptake of 4 kg Nha −1 by gaseous N-species in form of NH 3 and NO 2 (Kreutzer et al 2009), canopies seem to play a more important role than supposed by acting as a N sink and transformer of inorganic N (NO 3 -N, NH 4 -N) into organic N-species through microbial N immobilization, transformation and release. Hence, the enhanced growth and likely accelerated turn-over of phyllosphere microbial biomass promoted by easily available C and inorganic N under herbivore infestation (Lovett et al 2002), likely contribute to the intensified release of "residual-N" (DON and NH 4 -N) and of POC and PNb (>0.45 μm) as well. Hence, beside a direct quantitative alteration in organic matter fluxes, the insect-induced frass activity also creates qualitative changes from inorganic to more organic N dominated matter fluxes.…”

Section: Discussionmentioning

confidence: 99%

Insect herbivory, organic matter deposition and effects on belowground organic matter fluxes in a central European oak forest

2011

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Apart from the forest floor, the canopy of forested ecosystems functions as the second most important source for dissolved and particulate fractions of organic and inorganic C and N compounds. However, under mass outbreak situations of insect herbivores this flux path of organic matter is considerably intensified clearly exceeding C and N fluxes from the forest floor. In this paper we report on herbivore-altered C and N fluxes from the canopy to the forest floor and effects on forest floor nutrient fluxes during severe defoliating herbivory of the winter moth (Operophtera brumata) and the mottled umber moth (Eranis defoliaria) in an oak forest in Germany. Over the course of 6.5 months we followed the C and N fluxes with bulk deposition, throughfall solution, insect frass deposits (green-fall together with insect faeces) and with forest floor solution in an 117-yr-old oak (Quercus petraea) forest. Compared to the control, herbivore defoliation significantly enhanced throughfall inputs of total and dissolved organic carbon and nitrogen by a factor of 3 and 2.5 (for TOC and DOC), and by 1.4 and 1.3 times (for TNb and DNb), respectively. Frass plus green-fall C and N fluxes peaked in May with 592 kg Cha −1 and 33.5 kg N ha −1 representing 79.6% (for C) and 78.3% (for N) of the total C and N input over 2.5 months. The quantitative and qualitative C and N input via faeces and litter deposition significantly differ between the insect affected and non-affected site. However, the C and N fluxes with throughfall did not significantly correlate with forest floor leachates. In this context, forest floor fluxes of TOC, DOC and NO 3 -N were significantly lower at the infested site compared to the control, whereas fluxes of NH 4 -N together with DON were significantly higher. The study demonstrates the importance of linking the population and associated frass dynamics of herbivorous insects with the cycling of nutrients and organic matter in forest ecosystems, highlighting the remarkable alterations in the timing, amounts and nature of organic matter dynamics on the ecosystem level. Consequently, the ecology of phytophagous insects allows partly to explain temporal-spatial alterations in nutrient cycling and thus ecosystem functioning.

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Section: Discussionmentioning

confidence: 99%

Insect herbivory, organic matter deposition and effects on belowground organic matter fluxes in a central European oak forest

2011

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“…Invasive animals can directly alter ecosystem processes (Strayer et al 1999, Lovett et al 2002, Hall et al 2003, Simon et al 2004. Despite an altered trophic structure in Yellowstone Lake (Tronstad et al 2010), excretion fluxes from cutthroat trout were small under three (0.45% of animal excretion) and four trophic levels (0.23% of animal excretion).…”

Section: Invasive Lake Trout Disrupted Excretion Fluxes From Native Cmentioning

confidence: 99%

Introduced lake trout alter nitrogen cycling beyond Yellowstone Lake

2015

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Citation: Tronstad, L. M., R. O. Hall Jr., and T. M. Koel. 2015. Introduced lake trout alter nitrogen cycling beyond Yellowstone Lake. Ecosphere 6(11):224. http://dx.doi.org/10.1890/ES14-00544.1Abstract. Introduced predators can have large effects on the ecosystem in which they were introduced, but how much these effects extend to other ecosystems beyond the invaded one is less known. We compared how lake trout (Salvelinus namaycush) affected nutrient cycling in an invaded and adjacent ecosystem in Yellowstone National Park, Wyoming, USA. Introduced lake trout in Yellowstone Lake caused the native Yellowstone cutthroat trout (Oncoryhynchus clarkii bouvieri ) population to decline. Native cutthroat trout are a dominant animal in the lake and may alter nutrient cycling in both Yellowstone Lake where they reside and in tributary streams used for spawning. We estimated changes in nutrient transport and nutrient uptake in both Yellowstone Lake and Clear Creek, a spawning stream, before and after the invasion of lake trout. Annual area-specific excretion fluxes from cutthroat trout were nine times higher in Clear Creek compared to Yellowstone Lake when cutthroat trout were abundant. However, fluxes within the lake and stream were similar after cutthroat trout declined. In Yellowstone Lake, zooplankton excretion supplied 86% of ammonium (NH 4 þ ) that was taken up, but cutthroat trout only supplied ,0.3% after the introduction of lake trout. Conversely, NH 4 þ excreted by cutthroat trout was likely a major flux in ClearCreek, because NH 4 þ fluxes from cutthroat trout exceeded watershed export of NH 4 þ in years when .3000 cutthroat trout spawned. Furthermore, NH 4 þ excretion fluxes from spawning cutthroat trout in ClearCreek supplied up to 6.1% of the NH 4 þ demanded by microbes after the introduction of lake trout.However, based on modeled past NH 4 þ uptake, we estimated that up to 60% of NH 4 þ excreted by spawning cutthroat trout may have been taken up by stream microbes when cutthroat trout were abundant. Therefore, transported NH 4 þ from spawning cutthroat trout was likely an integral part of N cycling in tributary streams in the past. By comparing the effects of declining cutthroat trout on two ecosystems, we show that lake trout had a larger effect on N cycling within an adjacent stream ecosystem than the invaded lake ecosystem itself, because the migratory behavior of cutthroat trout concentrated them in spawning streams increasing their effect.

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“…The nitrogen pulse comes from the insect feces, dead caterpillars, unconsumed green foliage and increased leaching of nitrogen from dame foliage. Most of this N is immobilized by soil microorganisms (Lovett et al, , 2006 or incorporated into soil organic matter Lovett et al, 2002). Although increases in nitrate leaching have been frequently reported after insect defoliation (Swank et al, 1981;Webb et al, 1995;Eshelman et al, 1998;Reynolds et al, 2000;Tokuchi et al, 2004;Hubber, 2005;Lewis and Likens, 2007) this did not happen in our case, probably because it was rapidly taken up by regrowing plants Frost and Hunter, 2004) which expanded very fast at the same time that eucalypts decline.…”

Section: Discussionmentioning

confidence: 51%

“…Absence of response in nutrient concentration after insect defoliations was also reported by Bormann and Likens (1979) and Christenson et al (2002) in watersheds covered by other tree species different from E. globulus. The insect defoliation may cause an increase of nitrogen and labile carbon to the forest floor (Rinker et al, 2001;Lovett et al, 2002;Frost and Hunter, 2008). The nitrogen pulse comes from the insect feces, dead caterpillars, unconsumed green foliage and increased leaching of nitrogen from dame foliage.…”

Section: Discussionmentioning

confidence: 99%

“…Insect defoliation effects in the ecosystem include the disturbances directly associated to the action of the pest, which cause tree defoliation, loss of vigor or death and other indirect consequences such as temporary reduction in productivity and evapotranspiration, increased leaching of nutrients, stimulation of decomposition, and changes in microclimatic conditions in the forest (Webb et al, 1995;Lovett et al, 2002). Foliar herbivory may also affect soil faunal population structure and N acquisition (Bradford et al, 2008).…”

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confidence: 99%

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Absence of effects on nutrient budgets after insect defoliation

Fernández¹,

Vega²,

Fontúrbel³

et al. 2011

For. syst.

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Nutrient export via streamflow after the defoliation by Gonipterus scutellatus Gill. in a Eucalyptus globulus Labill. watershed in Galicia (NW Spain) was monitored from 1999 to 2006. The effects of such defoliation on nutrients balance had not been previously evaluated. Insect defoliation caused no significant changes in streamflow nutrient concentrations during the period of study compared with the pre-perturbation period and nutrient exports in streamflow were compensated via precipitation in all cases. The results presented here show that in spite of the reduction in E.globulus growth caused by the defoliation, nutrient balances were positive, suggesting a minor impact in the soil-plant system nutrient budget.

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Insect Defoliation and Nitrogen Cycling in Forests

Cited by 229 publications

References 29 publications

Insect herbivory, organic matter deposition and effects on belowground organic matter fluxes in a central European oak forest

Insect herbivory, organic matter deposition and effects on belowground organic matter fluxes in a central European oak forest

Introduced lake trout alter nitrogen cycling beyond Yellowstone Lake

Absence of effects on nutrient budgets after insect defoliation

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