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- Title
Importance du réseau trophique du sol dans la stabilité du fonctionnement des écosystèmes forestiers méditerranéens soumis au changement climatique.
- Authors
AUPIC-SAMAIN, Adriane
- Abstract
Soil food web plays a key role in nutrient cycles and energetic fluxes essential for ecosystem functioning. Despite the relative importance of these organisms in plant litter decomposition, only few studies have focused on soil food webs in Mediterranean forests. However, Mediterranean plant species, adapted to drought and high temperature conditions, exhibit distinct litter physico-chemical characteristics likely to strongly control soil food web. In addition, among terrestrial biomes, Mediterranean ecosystems appear as the most sensitive to climate change. More intense water stress could directly affect soil organisms but also indirectly through shifts in litter quality. In order to understand how climate change could alter the structure and functions of soil food web in Mediterranean forest, we used three forested equipped sites: deciduous Quercus pubescens Willd. forest (O3HP), evergreen Quercus ilex L. forest (Puéchabon) and Pinus halepensis Mill. forest (Font-Blanche), experimentally subjected to an aggravated drought predicted by climatic models in the Mediterranean thanks to a rain exclusion device (--30% of annual precipitation). Firstly, results of a field experiment evidenced that Q. ilex exhibits lower abundance and biomass of arthropod communities as well as reduced energy fluxes between trophic groups compared to the two other forests. These results suggest that differences in physico-chemical soil properties among forests lead to strong bottom-up control on the structure and energetic architecture of soil food webs. While abundance and biomass of detritivores and omnivores are reduced with amplified drought, energy fluxes are similar between the precipitation treatments suggesting a strong stability of soil food webs in Mediterranean forest. Secondly, a litterbag transplant experiment was performed to understand the direct and indirect (via shifts in litter quality) drought effects on microbial and mesofaunal communities associated with the litter of the three tree species in the three forests. After two years of decomposition, microbial biomasses and mesofaunal abundances are higher with Q. pubescens litter compared to Q. ilex and P. halepensis litters highlighting the importance of some litter traits for soil organisms. Amplified drought induces shifts in litter quality, but no change is reported for soil organisms. In addition, microbial and mesofaunal parameters differently respond to the direct drought effect according to the forest type. These results suggest that in a same Mediterranean region, climate change could distinctly modify soil organisms and their contribution to the decomposition process. In a laboratory experiment, we evidenced that litter quality and especially its physical structure (leaf vs. needle) controls soil food web organisms (fungi-Collembola-predatory Acari). À second mesocosm experiment aimed to evaluate the interactive effects of the increasing temperature and reducing soil moisture on a Collembola community, with or without predatory Acari. As provided by the in-situ experiment, laboratory results evidenced that drought differentially affects Collembola species but reduces collembolan community abundance i) by suppressing the positive effect of increasing temperature and ii) by strengthened the predatory control on collembolan abundance. Finally, this thesis highlights the importance of soil and litter physico-chemical characteristics acting as bottom-up driver and of the water availability on the soil food web structure in Mediterranean forests.
- Subjects
MEDITERRANEAN Region; PLANT species; FOOD chains; CLIMATE change; DECIDUOUS plants
- Publication
Ecologia Mediterranea, 2020, Vol 46, Issue 2, p107
- ISSN
0153-8756
- Publication type
Article