Antiherbivore chemicals in emerging and previous-year foliage of balsam fir saplings responding to prior simulated browsing

Warbrick, Montana L; Kroeker, Allyson; Nosko, Peter

doi:10.1007/s11258-020-01027-y

Cited by 2 publications

(3 citation statements)

References 67 publications

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“…Third, it is possible that high herbivore densities tend to have a stronger effect on the quantity, rather than quality, of food available to moose. In support of that idea, experiments suggest that browsing had no effect on concentrations of condensed tannins in balsam fir saplings; and there is conflicting evidence about whether browsing influenced phenol concentrations (Nosko et al 2020, Warbrick et al 2020). Therefore, if nutritional condition and investment in detoxification are primarily influenced by the nutritional quality of food consumed, then it may explain why moose density was not a useful predictor of UN:C or GA:C.…”

Section: Discussionmentioning

confidence: 99%

“…concentrations of crude protein and PSMs) can vary substantially among plants of the same species and among parts of the same plant (Terra‐Berns 1993, Frye et al 2013, Ulappa et al 2014). For example, PSM profiles can vary among plants of the same species due to differences in tree height, the age of foliage, light availability and soil pH (Nosko et al 2020, Warbrick et al 2020). Therefore, even if herbivores consume a similar quantity of a given forage species, the amount of PSMs or protein that they consume may differ depending on which particular trees or parts of the trees they browsed.…”

Section: Discussionmentioning

confidence: 99%

“…The extent that concentrations of PSM vary spatially and temporally in this system is not known, but one potentially important difference is that the protein content of balsam fir tends to be greater in the western region (Supporting information). Such differences in protein content are likely to be important because balsam fir and some other forage species contain condensed tannins (Sauvé and Côté 2007, Nosko et al 2020, Warbrick et al 2020) that bind with protein (Barbehenn and Constabel 2011). Additionally, when herbivores consume high concentrations of PSMs whilst on low-protein diets it can cause a negative nitrogen balance (Au et al 2013).…”

Section: Regional Differencesmentioning

confidence: 99%

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The nutritional condition of moose co‐varies with climate, but not with density, predation risk or diet composition

Hoy

Forbey

Melody

et al. 2021

Oikos

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A fundamental question about the ecology of herbivore populations pertains to the relative influence of biotic and abiotic processes on nutritional condition. Nutritional condition is influenced in important, yet poorly understood, ways by plant secondary metabolites (PSMs) which can adversely affect a herbivore's physiology and energetics.Here we assess the relative influence of various abiotic (weather) and biotic (intraspecific competition, predation risk and diet composition) factors on indicators of nutritional condition and the energetic costs of detoxifying PSMs for the moose population in Isle Royale National Park (USA). Specifically, we observed interannual variation in the ratio of urea nitrogen to creatinine (UN:C), an indicator of nutritional restriction, over 29 years and the ratio of glucuronic acid to creatinine (GA:C), an indicator of energetic investment in detoxifying PSMs, over 19-years. Both UN:C and GA:C were measured in samples of urine-soaked snow. Most importantly, climatic factors explained 66% of the interannual variation in UN:C, with moose being more nutritionally stressed during winters with deep snow and during winters that followed warm summers. None of the biotic factors (density, predation, diet composition) were useful predictors of UN:C or GA:C. The absence of a relationship between diet composition and either UN:C or GA:C suggests that the nutritional ecology of wild herbivores is probably complicated by fine-scale variation in protein content and concentrations of PSMs amongst plants of the same species. UN:C increased with GA:C at both the individual and population-level. That result is consistent with detoxification being energetically costly, such that it impairs nutritional condition and also highlights how spatio-temporal variation in the intake and detoxification of PSMs may influence population dynamics. Lastly, because we observed interannual variation in nutritional condition over three decades and detoxification over two decades these findings are relevant to concerns about how herbivore populations respond to climate change.

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Section: Discussionmentioning

confidence: 99%