Driving mechanisms of overstorey–understorey diversity relationships in European forests

Ampoorter, Evy; Selvi, Federico; Auge, Harald; Baeten, Lander; Sigrid, Berger; Carrari, Elisa; Coppi, Andrea; Fotelli, Mariangela N.; Radoglou, Kalliopi; Setiawan, Nuri Nurlaila; Vanhellemont, Margot; Verheyen, Kris

doi:10.1016/j.ppees.2016.02.001

Cited by 43 publications

(18 citation statements)

References 46 publications

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“…Furthermore, several studies have reported that high diversity in the overstorey canopy has beneficial effects for understorey abundance and diversity [60], as a consequence of the light variability in the understorey layer that is created through the complementarity and overlapping of overstorey crowns [63][64][65]. As such, the abundance and diversity of understorey vegetation are positively affected by light heterogeneity [47,55,66], as predicted by the resource heterogeneity hypothesis.…”

Section: Lightmentioning

confidence: 95%

“…Mixed overstorey canopies tend to support more abundant and diverse understorey vegetation than do pure broadleaf and coniferous canopies, as a consequence of resource heterogeneity caused by overstorey diversity [10,14,49,55]. This diversity reduces interspecific competition in the understorey and enables species with different resource requirements to co-exist [19].…”

Section: Overstorey Composition and Diversitymentioning

confidence: 99%

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Forest Understorey Vegetation: Colonization and the Availability and Heterogeneity of Resources

Wang

Huang

et al. 2019

Forests

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Understorey vegetation comprises a major portion of plant diversity and contributes greatly to nutrient cycling and energy flow. This review examines the mechanisms involved in the response of understorey vegetation to stand development and the overstorey canopy following disturbances. The overall abundance and diversity of the understorey is enhanced with the availability and heterogeneity of light, soil nutrients, soil moisture, and substrates. Vascular plants are positively impacted by the availability and heterogeneity of light and soil nutrients, whereas non-vascular vegetation is more strongly influenced by colonization time, soil moisture, and substrates, and is decreased with a higher proportion of broadleaf overstorey. The availability of resources is a prominent driver toward the abundance and diversity of understorey vegetation, from the stand initiation to stem exclusion stage under a single-species dominated overstorey. However, resource heterogeneity dominates at the later stages of succession under a mixed overstorey. Climate and site conditions modify resource availability and heterogeneity in the understorey layer, but the extent of their influences requires more investigation. Forest management practices (clearcutting and partial harvesting) tend to increase light availability and heterogeneity, which facilitates the abundance and diversity of understorey vascular plants; however, these factors reduce the occurrence of non-vascular plants. Nevertheless, in the landscape context, anthropogenic disturbances homogenize environmental conditions and reduce beta-diversity, as well, the long-term effects of anthropogenic disturbances on understorey vegetation remain unclear, particularly compared with those in primary forests.

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Section: Lightmentioning

confidence: 95%

Section: Overstorey Composition and Diversitymentioning

confidence: 99%

Forest Understorey Vegetation: Colonization and the Availability and Heterogeneity of Resources

Wang

Huang

et al. 2019

Forests

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“…A positive decoupling of PD from USR along the OSR gradient would have occurred if the species that "enter" in the understorey of 3-or 4-species mixtures plots added a proportionally greater amount of evolutionary diversity than those growing in pure stands or 2species mixtures. Our non-significant result was likely due to incorrect prediction that more distantly related species are more able to use different niches, and/or to the inconsistency of the environmental heterogeneity hypothesis as already suggested in other studies on overstoreyunderstorey diversity relationships in temperate forests (Barbier et al 2008;Ampoorter et al 2016).…”

Section: Discussionmentioning

confidence: 58%

“…2 2 2 2 2 SR = 2 (N = 9) 1 1 1 1 variations were unavoidable due to the complex geomorphology of our hilly region and the long-lasting anthropic activities in the forests. Understorey data collection followed the protocol described in Ampoorter et al (2016): in each plot, three 5 m × 5 m sampling quadrats were placed in three distinct subplots at a regular distance along a diagonal from the lower left corner to the upper right corner, respectively (Fig. 1); this design allowed to minimize the edge effect and to sufficiently account for the heterogeneity of micro-topographic conditions inside the plot.…”

Section: Study Site Sampling Design and Data Collectionmentioning

confidence: 99%

“…Several studies have investigated the mechanisms and factors that determine the diversity and composition of the understorey community, mostly in the forests of the central and northern countries (e.g. Mölder et al 2008;Barbier et al 2009;Vockenhuber et al 2011;Verstraeten et al 2013;Ampoorter et al 2014Ampoorter et al , 2015Ampoorter et al , 2016. Vertical structure and species composition of the overstorey can have major effects on the herb layer, because canopy trees have a species-specific influence on the quality and availability of resources, especially water, nutrients and light, as well as on the physical properties of the litter and soil (Barbier et al 2008).…”

Section: Introductionmentioning

confidence: 99%

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Understorey phylogenetic diversity in thermophilous deciduous forests: overstorey species identity can matter more than species richness

et al. 2019

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Background: Understorey vegetation is a key biodiversity component of forest ecosystems. Previous studies examined its relations with the overstorey mainly in terms of taxonomic diversity, composition or productivity. So far, none focused on the phylogenetic aspect, which represents the deepest component of diversity in a community. Here, we explored the relations between overstorey species richness and identity and the phylogenetic structure of the understorey vegetation. As a model system we used a network of 36 plots in thermophilous deciduous forests of central Italy that are part of a European project on forest biodiversity and functions. The plots, characterized by similar site conditions, represent a gradient of overstorey richness from 1 to 4-species mixtures, with variable composition. After surveying the understorey in each plot, measures of phylogenetic diversity and structure (Phylogenetic Diversity, PD; Net Relatedness Index, NRI; and Nearest Taxon Index, NTI) were calculated from a fully resolved seed-plant phylogeny obtained from a ITS-5.8S nrDNA dataset including original sequences from local plant material. Results: The resulting understorey phylogenetic tree allowed reliable estimation of PD, NRTI and NTI. Phylogenetic diversity was dependent on species richness and the strength of this relationship did not change along the gradient of overstorey tree species richness. Net Relatedness and Nearest Taxon indices were both mostly positive but nonsignificant, indicating random phylogenetic structure of the understorey. The presence of Quercus petraea, usually found in more favorable site conditions, was associated with a significant phylogenetic clustering at the species level. Conclusions: Overstorey species richness was not related to understorey phylogenetic structure, while species identity (Q. petraea) was associated with an increase in evolutionary relatedness in this forest layer, possibly due to competitive exclusion in favorable site conditions. Further studies should examine whether and how understory phylogenetic structure is affected by variables such as small scale variations in site conditions and presence of a shrub layer, both present but not accounted for in our model system. A better understanding of the role of these variables and their interaction may contribute to fill the current gap between the theoretical field of phylogenetic ecology and forest management.

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How tree species identity and diversity affect light transmittance to the understory in mature temperate forests

Sercu

Baeten

Coillie

et al. 2017

Ecology and Evolution

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Light is a key resource for plant growth and is of particular importance in forest ecosystems, because of the strong vertical structure leading to successive light interception from canopy to forest floor. Tree species differ in the quantity and heterogeneity of light they transmit. We expect decreases in both the quantity and spatial heterogeneity of light transmittance in mixed stands relative to monocultures, due to complementarity effects and niche filling. We tested the degree to which tree species identity and diversity affected, via differences in tree and shrub cover, the spatiotemporal variation in light availability before, during, and after leaf expansion. Plots with different combinations of three tree species with contrasting light transmittance were selected to obtain a diversity gradient from monocultures to three species mixtures. Light transmittance to the forest floor was measured with hemispherical photography. Increased tree diversity led to increased canopy packing and decreased spatial light heterogeneity at the forest floor in all of the time periods. During leaf expansion, light transmittance did differ between the different tree species and timing of leaf expansion might thus be an important source of variation in light regimes for understory plant species. Although light transmittance at the canopy level after leaf expansion was not measured directly, it most likely differed between tree species and decreased in mixtures due to canopy packing. A complementary shrub layer led, however, to similar light levels at the forest floor in all species combinations in our plots. Synthesis. We find that a complementary shrub layer exploits the higher light availability in particular tree species combinations. Resources at the forest floor are thus ultimately determined by the combined effect of the tree and shrub layer. Mixing species led to less heterogeneity in the amount of light, reducing abiotic niche variability.

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Driving mechanisms of overstorey–understorey diversity relationships in European forests

Cited by 43 publications

References 46 publications

Forest Understorey Vegetation: Colonization and the Availability and Heterogeneity of Resources

Forest Understorey Vegetation: Colonization and the Availability and Heterogeneity of Resources

Understorey phylogenetic diversity in thermophilous deciduous forests: overstorey species identity can matter more than species richness

How tree species identity and diversity affect light transmittance to the understory in mature temperate forests

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