| 1. |
- Henneron, Ludovic
(författare)
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Habitat diversity associated to island size and environmental filtering control the species richness of rock-savanna plants in neotropical inselbergs
- 2019
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 42, s. 1536-1547
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Tidskriftsartikel (refereegranskat)abstract
- Disentangling the multiple factors controlling species diversity is a major challenge in ecology. Island biogeography and environmental filtering are two influential theories emphasizing respectively island size and isolation, and the abiotic environment, as key drivers of species richness. However, few attempts have been made to quantify their relative importance and investigate their mechanistic basis. Here, we applied structural equation modelling, a powerful method allowing test of complex hypotheses involving multiple and indirect effects, on an island-like system of 22 French Guianan neotropical inselbergs covered with rock-savanna. We separated the effects of size (rock-savanna area), isolation (density of surrounding inselbergs), environmental filtering (rainfall, altitude) and dispersal filtering (forest-matrix openness) on the species richness of all plants and of various ecological groups (terrestrial versus epiphytic, small-scale versus large-scale dispersal species). We showed that the species richness of all plants and terrestrial species was mainly explained by the size of rock-savanna vegetation patches, with increasing richness associated with higher rock-savanna area, while inselberg isolation and forest-matrix openness had no measurable effect. This size effect was mediated by an increase in terrestrial-habitat diversity, even after accounting for increased sampling effort. The richness of epiphytic species was mainly explained by environmental filtering, with a positive effect of rainfall and altitude, but also by a positive size effect mediated by enhanced woody-plant species richness. Inselberg size and environmental filtering both explained the richness of small-scale and large-scale dispersal species, but these ecological groups responded in opposite directions to altitude and rainfall, that is positively for large-scale and negatively for small-scale dispersal species. Our study revealed both habitat diversity associated with island size and environmental filtering as major drivers of neotropical inselberg plant diversity and showed the importance of plant species growth form and dispersal ability to explain the relative importance of each driver.
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| 2. |
- Henneron, Ludovic
(författare)
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Plant economic strategies of grassland species control soil carbon dynamics through rhizodeposition
- 2020
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 108, s. 528-545
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Tidskriftsartikel (refereegranskat)abstract
- 1. The plant economics spectrum is increasingly recognized as a major determinant of plant species effects on terrestrial ecosystem functioning related to carbon cycling. However, the role of plant economic strategies in the effects of living root activity on soil organic carbon (SOC) dynamics through rhizodeposition remains unexplored, despite SOC being the largest terrestrial carbon pool.2. Using a continuous C-13-labelling method allowing partitioning of plant and soil sources to carbon fluxes and pools, we studied here the linkages between plant economic strategies and SOC cycling processes in a 'common garden' greenhouse experiment. It includes a panel of 12 grassland species selected along a gradient of economic traits and belonging to three functionnal groups (C3 grasses, forbs and legumes).3. All species induced an acceleration of native SOC mineralization but this rhizosphere priming effect (RPE) substantially differed across species and varied elevenfold by the end of the experiment (from +26% to +295% relative to unplanted soil). Interspecific variation in RPE was primarily linked to plant photosynthetic activity associated to species economic strategies of light and CO2 resource acquisition and processing. Fast-growing acquisitive species, such as legumes, featured large RPE, in relation with their high canopy photosynthesis coupled to high leaf photosynthetic capacity and large net primary productivity allocated above-ground. This large RPE was further associated with high root metabolic activity, rhizodeposition and soil microbial activity. In contrast, fine-root growth and economic traits related to soil resource foraging ability were poor predictors of RPE.4. The formation of new root-derived SOC varied nine-fold across species and was similarly positively related to the net primary productivity allocated above-ground. Fast-growing acquisitive species with a high photosynthetic activity induced a disproportionately large RPE relative to SOC formation.5. Synthesis. Overall, our study demonstrates that rhizodeposition is a major mechanism through which plant economic strategies of grassland species control soil carbon dynamics. Acquisitive versus conservative species were associated with high versus low rates of photosynthesis and rhizodeposition, in turn leading to fast versus slow SOC turnover. This emphasizes the importance of considering rhizosphere processes for understanding plant species effects on soil biogeochemistry.
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| 3. |
- Henneron, Ludovic
(författare)
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Plasticity in leaf litter traits partly mitigates the impact of thinning on forest floor carbon cycling
- 2018
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 32, s. 2777-2789
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Tidskriftsartikel (refereegranskat)abstract
- Reducing stand density by thinning intensification has been emphasized as an efficient strategy of forest adaptation to climate change as it improves stand resistance to drought. Yet, it is still unclear how it could affect litter carbon (C) cycling processes. Recent evidence indicates that the plasticity of an oak tree species can lead to a decline in its leaf litter quality and decomposability following thinning. The consequences for litter decomposition and forest floor C storage at the ecosystem scale remain largely unexplored. In this study, we took advantage of a regional-scale, multi-site network of long-term thinning experiments in temperate oak (Quercus petraea) forests to address this issue. We measured ecosystem properties related to forest floor C cycling in 19 plots across eight experimental sites covering a large gradient of stand density and age. Though we expected thinning to affect in situ litter decomposition by altering oak leaf litter quality, we conducted complementary experiments exploring additional mechanisms, that is alterations of microenvironmental conditions and soil faunal activity. Thinning intensification induced a strong decline in tree canopy leaf area index, above-ground tree litter production and forest floor decomposition rate in early "aggradation" stage of forest development. This slower litter decomposition was mainly driven by plasticity of oak trees that produced leaf litter of poorer quality and decomposability following thinning, for example, litter richer in secondary metabolites such as condensed tannins. Change in microenvironmental conditions also contributed to the slowdown of litter decomposition, likely as a result of the less buffered microclimate associated with larger tree canopy opening. No change in soil faunal effect induced by thinning was observed. Thinning intensification resulted in a limited decrease in forest floor C stock. Indeed, the slower litter decomposition offset nearly half of the forest floor C loss associated to the reduced litterfall in "aggradation" stage. Our study demonstrated that phenotypic plasticity in leaf litter traits of a dominant tree species can strongly affect ecosystem functioning by slowing forest floor decomposition following thinning intensification, in turn partly mitigating the negative effect of thinning on forest floor C storage.
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| 4. |
- Henneron, Ludovic
(författare)
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Relative importance of tree species richness, tree functional type, and microenvironment for soil macrofauna communities in European forests
- 2021
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 196, s. 455-468
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Tidskriftsartikel (refereegranskat)abstract
- Soil fauna communities are major drivers of many forest ecosystem processes. Tree species diversity and composition shape soil fauna communities, but their relationships are poorly understood, notably whether or not soil fauna diversity depends on tree species diversity. Here, we characterized soil macrofauna communities from forests composed of either one or three tree species, located in four different climate zones and growing on different soil types. Using multivariate analysis and model averaging we investigated the relative importance of tree species richness, tree functional type (deciduous vs. evergreen), litter quality, microhabitat and microclimatic characteristics as drivers of soil macrofauna community composition and structure. We found that macrofauna communities in mixed forest stands were represented by a higher number of broad taxonomic groups that were more diverse and more evenly represented. We also observed a switch from earthworm-dominated to predator-dominated communities with increasing evergreen proportion in forest stands, which we interpreted as a result of a lower litter quality and a higher forest floor mass. Finally, canopy openness was positively related to detritivore abundance and biomass, leading to higher predator species richness and diversity probably through trophic cascade effects. Interestingly, considering different levels of taxonomic resolution in the analyses highlighted different facets of macrofauna response to tree species richness, likely a result of both different ecological niche range and methodological constraints. Overall, our study supports the positive effects of tree species richness on macrofauna diversity and abundance through multiple changes in resource quality and availability, microhabitat, and microclimate modifications.
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| 5. |
- Henneron, Ludovic, et al.
(författare)
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Rhizosphere control of soil nitrogen cycling: a key component of plant economic strategies
- 2020
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 228, s. 1269-1282
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how plant species influence soil nutrient cycling is a major theme in terrestrial ecosystem ecology. However, the prevailing paradigm has mostly focused on litter decomposition, while rhizosphere effects on soil organic matter (SOM) decomposition have attracted little attention. Using a dual(13)C/N-15 labeling approach in a 'common garden' glasshouse experiment, we investigated how the economic strategies of 12 grassland plant species (graminoids, forbs and legumes) drive soil nitrogen (N) cycling via rhizosphere processes, and how this in turn affects plant N acquisition and growth. Acquisitive species with higher photosynthesis, carbon rhizodeposition and N uptake than conservative species induced a stronger acceleration of soil N cycling through rhizosphere priming of SOM decomposition. This allowed them to take up larger amounts of N and allocate it above ground to promote photosynthesis, thereby sustaining their faster growth. The N-2-fixation ability of legumes enhanced rhizosphere priming by promoting photosynthesis and rhizodeposition. Our study demonstrates that the economic strategies of plant species regulate a plant-soil carbon-nitrogen feedback operating through the rhizosphere. These findings provide novel mechanistic insights into how plant species with contrasting economic strategies sustain their nutrition and growth through regulating the cycling of nutrients by soil microbes in their rhizosphere.
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