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Theses

Interactions between oak and cervids during the process of forest regeneration - the case study of plain temperate oak stands (Quercus robur et Q. petraea)

Abstract : The abundance and spatial distribution of cervids have drastically increased in France, and more generally in the Northern hemisphere over the last decades. These species play a crucial part in the functioning of forest ecosystems, but the current level of their populations compromises the process of forest regeneration for many tree species of crucial importance such as pedunculate and sessile oak (Quercus robur et Q. petraea). The objectives of this thesis are to quantify and unravel the mechanisms underlying the constraint exerted by cervids on oak regeneration through the consumption of acorns, of oak saplings and of admixed understory species, and (ii) to identify how specific forest management operations (i.e. fencing, felling, and clearing) can limit or enhance this constraint. The analysis of a long-term dataset of red and roe deer rumen content sampled in the study site of La Petite Pierre (Northeastern France) showed that acorns represented a significant resource in the diet of these two species, but that their acorn consumption saturated years of high fructification. Using experimental approaches, we showed that simulated deer browsing on the apical shoot systematically reduced oak sapling height growth both in situ and ex situ, and this was explained by a relatively poor plasticity in resource allocation following browsing to compensate for the loss of tissues. The analysis of a network of fenced-unfenced plots located in several sites in France and in Sweden showed that felling to increase canopy openness enhanced the negative effect of cervids on oak sapling growth and survival through a higher frequentation of cervids under open canopies. Lastly, after implementing the process of herbivory in a forest dynamic model (i.e. Regeneration library of CAPSIS modelling tool), I conducted simulations that suggested that under a high browsing pressure, less frequent clearing operations maintaining highly palatable sapling species such as hornbeam could reduce the negative influence of cervids on oak regeneration. To conclude, this thesis results confirm that cervids exert a significant constraint on the process of oak regeneration, but also suggest that adapted management of the understory vegetation could reduce this constraint and contribute to restore a balance between wildlife and silvicultural activities.
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Submitted on : Thursday, June 23, 2022 - 10:40:39 AM
Last modification on : Friday, June 24, 2022 - 3:56:24 AM

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DDOC_T_2021_0285_BARRERE.pdf
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  • HAL Id : tel-03702537, version 1

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Julien Barrere. Interactions between oak and cervids during the process of forest regeneration - the case study of plain temperate oak stands (Quercus robur et Q. petraea). Ecology, environment. Université de Lorraine, 2021. English. ⟨NNT : 2021LORR0285⟩. ⟨tel-03702537⟩

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