Climatic conditions, not above- and belowground resource availability and uptake capacity, mediate tree diversity effects on productivity and stability

Increasing evidence now exists for a tight connection between tree diversity and carbon storage capacity. As part of the Paris Agreement (COP21), forests play a critical and prominent role to reach the ambitious goal of net-zero emissions in the second half of this century. Besides reducing emissions from deforestation and forest degradation (also known as REDD), maintaining and enriching tree assemblages could thus help mitigating climate change via increased abundance and more efficient resource use.However, recent evidence questions this widespread idea of positive diversity effects on forest carbon storage. Specifically, tree diversity may not always be a causal mechanism but rather a consequence of tree abundance and productivity (following the &#8216;more individuals hypothesis&#8217;). To test these contrasting hypotheses, this contribution analyses the most plausible causal pathways and their stability along global climatic gradients in the diversity-abundance relationship across the World&#8217;s main forest biomes, using a dataset comprising more than 2,500 forest plots and 83,800 trees sampled in pristine forest landscapes in all continents (except Antarctica).We demonstrate that causal relations can be reconciled along global climate gradients, with diversity effects prevailing in the most productive environments, and abundance effects becoming dominant towards the most limiting conditions. These findings have major implications on climate change mitigation strategies aimed at carbon sequestration: we find that future nature-based mitigation solutions focused on fostering biodiversity will only be cost-effective in productive forest landscapes. In less productive environments, by contrast, mitigation measures should promote the abundance of locally adapted functional strategies. Conservation of species diversity in equatorial and tropical areas is thus a priority, not only to preserve the inherent value of biodiversity but also to achieve the global goals on atmospheric decarbonization. In less productive lands on Earth, the conservation of abundance through productivity should be posed, next to diversity, as a major element in environmental policies and land management.&#160;

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Tree diversity effects on leaf insect damage on pedunculate oak: The role of landscape context and forest stratum

Forest Ecology and Management ◽

10.1016/j.foreco.2018.11.014 ◽

2019 ◽

Vol 433 ◽

pp. 287-294 ◽

Cited By ~ 10

Author(s):

Bastien Castagneyrol ◽

Brice Giffard ◽

Elena Valdés-Correcher ◽

Arndt Hampe

Keyword(s):

Tree Diversity ◽

Landscape Context ◽

Insect Damage ◽

Pedunculate Oak ◽

Diversity Effects

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Functional trait variability and identity determine the extent of tree diversity effects on productivity: A global meta-analysis

Authorea ◽

10.22541/au.157592563.31029938 ◽

2019 ◽

Author(s):

Liting Zheng ◽

Han Y H Chen ◽

Shekhar Biswas ◽

Difeng Bao ◽

Xiaochen Fang ◽

...

Keyword(s):

Meta Analysis ◽

Functional Trait ◽

Tree Diversity ◽

Diversity Effects ◽

Trait Variability

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Tree diversity effects on ecosystem functioning – Introduction

Basic and Applied Ecology ◽

10.1016/j.baae.2021.06.004 ◽

2021 ◽

Author(s):

Stefan Trogisch ◽

Xiaojuan Liu ◽

Gemma Rutten ◽

Helge Bruelheide

Keyword(s):

Ecosystem Functioning ◽

Tree Diversity ◽

Diversity Effects

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Tree diversity increases robustness of multi-trophic interactions

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.2399 ◽

2019 ◽

Vol 286 (1898) ◽

pp. 20182399 ◽

Cited By ~ 11

Author(s):

Felix Fornoff ◽

Alexandra-Maria Klein ◽

Nico Blüthgen ◽

Michael Staab

Keyword(s):

Trophic Interactions ◽

Experimental Manipulation ◽

Tree Diversity ◽

Trophic Levels ◽

Community Diversity ◽

Ecosystem Functions ◽

Network Analyses ◽

Biodiversity Change ◽

Ant Diversity ◽

Diversity Effects

Multi-trophic interactions maintain critical ecosystem functions. Biodiversity is declining globally, while responses of trophic interactions to biodiversity change are largely unclear. Thus, studying responses of multi-trophic interaction robustness to biodiversity change is crucial for understanding ecosystem functioning and persistence. We investigate plant–Hemiptera (antagonism) and Hemiptera–ant (mutualism) interaction networks in response to experimental manipulation of tree diversity. We show increased diversity at both higher trophic levels (Hemiptera and ants) and increased robustness through redundancy of lower level species of multi-trophic interactions when tree diversity increased. Hemiptera and ant diversity increased with tree diversity through non-additive diversity effects. Network analyses identified that tree diversity also increased the number of tree and Hemiptera species used by Hemiptera and ant species, and decreased the specialization on lower trophic level species in both mutualistic and antagonist interactions. Our results demonstrate that bottom-up effects of tree diversity ascend through trophic levels regardless of interaction type. Thus, local tree diversity is a key driver of multi-trophic community diversity and interaction robustness in forests.

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Moose browsing alters tree diversity effects on birch growth and insect herbivory

Functional Ecology ◽

10.1111/1365-2435.12407 ◽

2015 ◽

Vol 29 (5) ◽

pp. 724-735 ◽

Cited By ~ 23

Author(s):

Evalyne W. Muiruri ◽

Harriet T. Milligan ◽

Simon Morath ◽

Julia Koricheva

Keyword(s):

Insect Herbivory ◽

Tree Diversity ◽

Diversity Effects ◽

Moose Browsing

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Tree diversity effects on forest productivity increase through time because of spatial partitioning

Forest Ecosystems ◽

10.1186/s40663-020-00238-z ◽

2020 ◽

Vol 7 (1) ◽

Cited By ~ 1

Author(s):

Shinichi Tatsumi

Keyword(s):

Forest Productivity ◽

Tree Diversity ◽

Spatial Partitioning ◽

Productivity Increase ◽

Diversity Effects

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Meta-analysis of tree diversity effects on the abundance, diversity and activity of herbivores' enemies

10.1101/2021.07.05.451117 ◽

2021 ◽

Author(s):

Alex Stemmelen ◽

Hervé Jactel ◽

Eckehard Brockerhoff ◽

Bastien Castagneyrol

Keyword(s):

Natural Enemies ◽

Natural Enemy ◽

Meta Analysis ◽

Mixed Forest ◽

Forest Tree ◽

Tree Diversity ◽

Enemies Hypothesis ◽

Natural Enemies Hypothesis ◽

Abundance And Diversity ◽

Diversity Effects

The natural enemies hypothesis predicts that the abundance and diversity of antagonists such as predators and parasitoids of herbivores increases with the diversity of plants, which can lead to more effective top-down control of insect herbivores. However, although the hypothesis has received large support in agricultural systems, fewer studies have been conducted in forest ecosystems and a comprehensive synthesis of previous research is still lacking. We conducted a meta-analysis of 65 publications comparing the diversity, abundance or activity of various groups of natural enemies (including birds, bats, spiders and insect parasitoids) in pure vs. mixed forest stands. We tested the effects of forest biome, natural enemy taxon and type of study (managed vs experimental forest). We found a significant positive effect of forest tree diversity on natural enemy abundance and diversity but not on their activity. The effect of tree diversity on natural enemies was stronger towards lower latitudes but was not contingent on the natural enemy taxon. Overall, our study contributes substantially toward a better understanding of the natural enemies hypothesis in forest systems and provides new insights about the mechanisms involved. Furthermore, we outline potential avenues for strengthening forest resistance to the growing threat of herbivorous insects.

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Contrasting Leaf Trait Responses of Conifer and Broadleaved Seedlings to Altered Resource Availability Are Linked to Resource Strategies

Plants ◽

10.3390/plants9050621 ◽

2020 ◽

Vol 9 (5) ◽

pp. 621

Author(s):

Yan-Li Zhang ◽

Barbara Moser ◽

Mai-He Li ◽

Thomas Wohlgemuth ◽

Jing-Pin Lei ◽

...

Keyword(s):

Environmental Change ◽

Nutrient Availability ◽

Resource Availability ◽

Soluble Sugars ◽

Light Availability ◽

Climatic Conditions ◽

Tree Seedling ◽

Leaf Trait ◽

Foliar Traits ◽

Resource Strategy

(1) Understanding tree seedling responses to water, nutrient, and light availability is crucial to precisely predict potential shifts in composition and structure of forest communities under future climatic conditions. (2) We exposed seedlings of widespread Central European tree species with contrasting leaf habit, deciduous broadleaves (DB) and evergreen conifers (EC), to factorial combinations of manipulated precipitation (100% and 50% of ambient), shade (40% and 60% of full sunlight), and nutrient availability (low and high NPK), and measured specific leaf area, C/N ratio, soluble sugars, starch and non-structural carbohydrate concentration, and δ13C of the leaves. (3) We found contrasting effects of water and nutrient availability on foliar traits of the two species groups: EC exhibited higher tolerance to low resource availability but also less plasticity in foliar traits, which is congruent with a “slow” resource strategy. In contrast, foliage of DB reacted particularly to altered nutrient availability, corresponding to a “fast” resource strategy with high foliar plasticity and rapid adjustments to resource fluctuations, commonly adopted by species with high growth rates. (4) We conclude that DB will respond to environmental change with foliar acclimation, while EC will either tolerate, to some extent, or shift their distribution range in response to environmental change.

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