Tree species richness attenuates the positive relationship between mutualistic ant–hemipteran interactions and leaf chewer herbivory

Interactions across trophic levels influence plant diversity effects on ecosystem functions, but the complexity of these interactions remains poorly explored. For example, the interplay between different interactions (e.g. mutualism, predation) might be an important moderator of biodiversity–ecosystem function relationships. We tested for relationships between trophobioses (facultative ant–hemipteran mutualism) and leaf chewer herbivory in a subtropical forest biodiversity experiment. We analysed trophobiosis and herbivory data of more than 10 000 trees along a tree species richness gradient. Against expectations, chewing damage was higher on trees with trophobioses. However, the net positive relationship between trophobioses and overall herbivory depended on tree species richness, being most pronounced at low richness. Our results point to indirect, positive effects of ant-tended sap suckers on leaf chewers, potentially by altering plant defences. Direct antagonistic relationships of trophobiotic ants and leaf-chewing herbivores—frequently reported to drive community-wide effects of trophobioses in other ecosystems—seemed less relevant. However, antagonistic interactions likely contributed to the attenuating effect of tree species richness, because trophobiotic ant and herbivore communities changed from monocultures to species-rich mixtures. Our findings, therefore, suggest that biodiversity loss might lead to complex changes in higher trophic level effects on ecosystem functions, mediated by both trophic and non-trophic interactions.

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Early positive effects of tree species richness on soil organic carbon accumulation in a large-scale forest biodiversity experiment

Journal of Plant Ecology ◽

10.1093/jpe/rtz026 ◽

2019 ◽

Vol 12 (5) ◽

pp. 882-893 ◽

Cited By ~ 8

Author(s):

Yin Li ◽

Helge Bruelheide ◽

Thomas Scholten ◽

Bernhard Schmid ◽

Zhenkai Sun ◽

...

Keyword(s):

Species Richness ◽

Organic Carbon ◽

Leaf Litter ◽

Tree Species ◽

Root Biomass ◽

Fine Root ◽

Soil Depth ◽

Fine Root Biomass ◽

Positive Effects ◽

Tree Species Richness

Abstract Aims Tree species richness has been reported to have positive effects on aboveground biomass and productivity, but little is known about its effects on soil organic carbon (SOC) accumulation. Methods To close this gap, we made use of a large biodiversity–ecosystem functioning experiment in subtropical China (BEF-China) and tested whether tree species richness enhanced SOC accumulation. In 2010 and 2015, vertically layered soil samples were taken to a depth of 30 cm from 57 plots ranging in tree species richness from one to eight species. Least squares-based linear models and analysis of variance were used to investigate tree diversity effects. Structural equation modeling was used to explore hypothesized indirect relationships between tree species richness, leaf-litter biomass, leaf-litter carbon content, fine-root biomass and SOC accumulation. Important Findings Overall, SOC content decreased by 5.7 and 1.1 g C kg−1 in the top 0–5 and 5–10 cm soil depth, respectively, but increased by 1.0 and 1.5 g C kg−1 in the deeper 10–20 and 20–30 cm soil depth, respectively. Converting SOC content to SOC stocks using measures of soil bulk density showed that tree species richness did enhance SOC accumulation in the different soil depths. These effects could only to some extent be explained by leaf-litter biomass and not by fine-root biomass. Our findings suggest that carbon storage in new forests in China could be increased by planting more diverse stands, with the potential to contribute to mitigation of climate warming.

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Tropical tree diversity mediates foraging and predatory effects of insectivorous birds

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.1842 ◽

2018 ◽

Vol 285 (1890) ◽

pp. 20181842 ◽

Cited By ~ 10

Author(s):

Colleen S. Nell ◽

Luis Abdala-Roberts ◽

Victor Parra-Tabla ◽

Kailen A. Mooney

Keyword(s):

Species Richness ◽

Indirect Effect ◽

Tree Species ◽

Attack Rate ◽

Tree Diversity ◽

Trophic Levels ◽

Tropical Tree ◽

Insectivorous Birds ◽

Bird Abundance ◽

Tree Species Richness

Biodiversity affects the structure of ecological communities, but little is known about the interactive effects of diversity across multiple trophic levels. We used a large-scale forest diversity experiment to investigate the effects of tropical tree species richness on insectivorous birds, and the subsequent indirect effect on predation rates by birds. Diverse plots (four tree species) had higher bird abundance (61%), phylogenetic diversity (61%), and functional diversity (55%) than predicted based on single-species monocultures, which corresponded to higher attack rates on artificial caterpillars (65%). Tree diversity effects on attack rate were driven by complementarity among tree species, with increases in attack rate observed on all tree species in polycultures. Attack rates on artificial caterpillars were higher in plots with higher bird abundance and diversity, but the indirect effect of tree species richness was mediated by bird diversity, providing evidence that diversity can interact across trophic levels with consequences tied to ecosystem services and function.

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Positive effects of tree species richness on fine-root production in a subtropical forest in SE-China

Journal of Plant Ecology ◽

10.1093/jpe/rtw094 ◽

2017 ◽

Vol 10 (1) ◽

pp. 146-157 ◽

Cited By ~ 31

Author(s):

Zhenkai Sun ◽

Xiaojuan Liu ◽

Bernhard Schmid ◽

Helge Bruelheide ◽

Wensheng Bu ◽

...

Keyword(s):

Species Richness ◽

Tree Species ◽

Fine Root ◽

Subtropical Forest ◽

Root Production ◽

Fine Root Production ◽

Positive Effects ◽

Tree Species Richness ◽

Se China

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Decoupling the Complementarity Effect and the Selection Effect on the Overyielding of Fine Root Production Along a Tree Species Richness Gradient in Subtropical Forests

Ecosystems ◽

10.1007/s10021-020-00538-z ◽

2020 ◽

Author(s):

Cong Liu ◽

Wenhua Xiang ◽

Binggeng Xie ◽

Shuai Ouyang ◽

Yelin Zeng ◽

...

Keyword(s):

Species Richness ◽

Tree Species ◽

Fine Root ◽

Selection Effect ◽

Root Production ◽

Fine Root Production ◽

Complementarity Effect ◽

Subtropical Forests ◽

Tree Species Richness ◽

Species Richness Gradient

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Drivers of understorey biomass – tree species identity is more important than richness in a young forest

Journal of Plant Ecology ◽

10.1093/jpe/rtab004 ◽

2021 ◽

Author(s):

Markus S Germany ◽

Helge Bruelheide ◽

Alexandra Erfmeier

Keyword(s):

Species Richness ◽

Tree Species ◽

Ecosystem Functioning ◽

Temporal Dynamics ◽

Light Transmittance ◽

Productivity Change ◽

Species Identity ◽

Tree Species Richness ◽

Young Forest ◽

Species Richness Gradient

Abstract Aims Positive biodiversity ecosystem functioning relationships have been widely reported, predominately from grassland ecosystems. However, this does not necessarily have to apply accordingly in more complex situations such as in forests across different vertical strata. For instance, overstorey tree species richness has been shown to be associated with a lower understorey productivity. Whether or not tree species richness effects add to understorey productivity by increasing (i.e. due to habitat heterogeneity) or reducing resource availability (i.e. through increasing competition) and whether understorey productivity is indeed being governed more strongly by tree species identity are likely to change over time. Moreover, studies also suggested that richness-productivity relationships change with the environmental context. Using an experimental forest plantation with manipulated tree species richness, this study examined these temporal and environmental dynamics across strata. Methods In the context of the Biodiversity-Ecosystem Functioning project in subtropical China (BEF-China), we made use of understorey biomass samples repeatedly collected over a time period of three years along a tree species richness gradient. The effects of tree species richness, tree species identities and time were studied across different environmental treatments for their impact on understorey biomass. Important Findings While we found significant and consistent tree layer identity effects on understorey biomass, no such effect was encountered for tree species richness. Our results also indicate that among structural layers in forests, there might not be a single, generalizable overstorey species richness- understorey productivity relationship, and that the extent as to which overstorey-related environmental factors such as light transmittance contribute to understorey productivity change with time. Overall, we demonstrate that temporal dynamics should be considered when studying relationship among structural layers in forests.

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Distinct effects of host and neighbour tree identity on arbuscular and ectomycorrhizal fungi along a tree diversity gradient

10.1101/2021.05.18.444754 ◽

2021 ◽

Author(s):

Olga Ferlian ◽

Kezia Goldmann ◽

Nico Eisenhauer ◽

Mika T. Tarkka ◽

Francois Buscot ◽

...

Keyword(s):

Species Richness ◽

Tree Species ◽

Mycorrhizal Fungi ◽

Biotic Interactions ◽

Ecosystem Functions ◽

Plant Resource ◽

Tree Species Richness ◽

Diversity Gradient ◽

Amf Communities ◽

Tree Identity

Plant diversity and plant-related ecosystem functions have been in focus in biodiversity-ecosystem functioning studies. However, in this context, biotic interactions with mycorrhizal fungi have been understudied although they are crucial for plant-resource acquisition. We investigated the effects of tree species richness, tree mycorrhizal type on arbuscular (AMF) and ectomycorrhizal fungal (EMF) communities. We aimed to understand how dissimilarities in taxa composition and beta-diversity are related to target trees and neighbours of the same/different mycorrhizal type. We sampled a tree experiment with saplings (~7 years old), where tree species richness (monocultures, 2-species, and 4-species mixtures) and mycorrhizal type were manipulated. AMF and EMF richness significantly increased with increasing tree species richness. AMF richness of mixture plots resembled that of the sum of the respective monocultures, whereas EMF richness of mixture plots was lower compared to the sum of the respective monocultures. Specialisation scores revealed significantly more specialised AMF than EMF suggesting that, in contrast to previous studies, AMF were more specialised, whereas EMF were not. We further found that AMF communities were little driven by the surrounding trees, whereas EMF communities were. Our study revealed the drivers of mycorrhizal fungal communities and further highlights the distinct strategies of AMF and EMF.

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Tree phylogenetic diversity promotes host–parasitoid interactions

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.0275 ◽

2016 ◽

Vol 283 (1834) ◽

pp. 20160275 ◽

Cited By ~ 23

Author(s):

Michael Staab ◽

Helge Bruelheide ◽

Walter Durka ◽

Stefan Michalski ◽

Oliver Purschke ◽

...

Keyword(s):

Species Richness ◽

Tree Species ◽

Phylogenetic Diversity ◽

Strong Predictor ◽

Trophic Levels ◽

Habitat Modification ◽

Parasitism Rate ◽

Tree Community ◽

Tree Species Richness ◽

Parasitism Rates

Evidence from grassland experiments suggests that a plant community's phylogenetic diversity (PD) is a strong predictor of ecosystem processes, even stronger than species richness per se . This has, however, never been extended to species-rich forests and host–parasitoid interactions. We used cavity-nesting Hymenoptera and their parasitoids collected in a subtropical forest as a model system to test whether hosts, parasitoids, and their interactions are influenced by tree PD and a comprehensive set of environmental variables, including tree species richness. Parasitism rate and parasitoid abundance were positively correlated with tree PD. All variables describing parasitoids decreased with elevation, and were, except parasitism rate, dependent on host abundance. Quantitative descriptors of host–parasitoid networks were independent of the environment. Our study indicates that host–parasitoid interactions in species-rich forests are related to the PD of the tree community, which influences parasitism rates through parasitoid abundance. We show that effects of tree community PD are much stronger than effects of tree species richness, can cascade to high trophic levels, and promote trophic interactions. As during habitat modification phylogenetic information is usually lost non-randomly, even species-rich habitats may not be able to continuously provide the ecosystem process parasitism if the evolutionarily most distinct plant lineages vanish.

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