Numerous studies have documented positive biodiversity–productivity relationships in both observational and experimental forest biodiversity studies. The horizontal distribution and vertical stratification of tree crowns can affect light interception and tree growth, thus driving forest productivity and carbon storage. However, the role of canopy structural complexity (CSC) in modulating biodiversity–productivity relationships and their change over time have rarely been quantified.
In this talk, I will present my project using 4-year consecutive UAV-borne LiDAR and ground-based growth field measurements of 38,088 trees growing in 482 plots containing 1, 2, 4, 8, 16, or 24 tree species, 11 to 15 years after planting, within a large-scale forest biodiversity experiment in southeast China (BEF-China). We found significant positive effects of tree species richness on multidimensional CSC indices (i.e., canopy cover, foliage height diversity, and box dimension)—encompassing horizontal, vertical, and holistic 3D canopy structures—across a broad diversity gradient over the 4 years. And community aboveground biomass significantly increased with all CSC indices. Additionally, the positive effect of tree species richness on community aboveground biomass was mediated by multifaceted CSC in all years studied, from 2021 to 2024. Furthermore, our results revealed significant positive relationships between the three CSC indices and net biodiversity effects or complementarity effects across the 4 years, but not with selection effects. And the positive relationships between the three CSC indices and complementarity effects strengthened from year to year.
In summary, our study experimentally demonstrates how tree species richness increases CSC and how CSC relates to increased community aboveground biomass and biodiversity complementarity effects. These findings reveal the key role of complementary use of aboveground space in a tree biodiversity experiment. Our study emphasizes the need to consider CSC and its role in mediating biodiversity complementarity effects to promote biomass production, carbon storage, and thus contribute to climate change mitigation in long-term afforestation projects.
How to cite: Deng, X. and Liu, X.: Diverse forests make complementary use of canopy space and produce more biomass, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-337, https://doi.org/10.5194/wbf2026-337, 2026.
Temperate forests are increasingly exposed to drought stress, leading to elevated risks of tree mortality, canopy die-off and forest carbon sink decline. Forest adaptation and resistance to drought stress largely rely on hydraulic diversity – the variety and range of hydraulic traits that regulate water use under drought conditions. Yet, how hydraulic diversity emerges within temperate forests and links to forest growth remains poorly resolved. To fill these gaps, we use eight hydraulic traits relating to stomatal closure, structural demand management, water storage, hydraulic resistance and rooting depth to quantify hydraulic diversity within forests, explore how it varies across temperate regions and explore its relationship with forest stem growth using the USA forest inventory data. A total of 31,304 forest plots were aggregated at a 1° grid-cell resolution and hydraulic diversity (721 metacommunities; those with fewer than three tree species are excluded) was quantified as the hypervolume size along the first two axes of principal component analysis (PCA). We found that higher diversity values were observed in the regions of the eastern USA while lower diversity values were found in the western and central USA and boreal regions. The variation in strategy diversity in temperate forests aligns mostly with changes along the acquisitive – conservative axis, spatial hydraulic diversity within temperate forest metacommunities indicates summer precipitation is more crucial than other climate variables. Interestingly, forests with low diversity are widely distributed across the full range of summer precipitation, suggesting that factors beyond water availability – such as temperature – may play an important role, particularly in the Pacific coast of Northern America. Moreover, we observed there is a positive relationship between hydraulic diversity and stem growth across the USA forest metacommunities. Our results provide a foundation for understanding forest hydraulic diversity and improving the accuracy in predicting forest carbon sink potential under a warmer and drier conditions.
How to cite: Liu, D., Pugh, T., Wang, S., and Essl, F.: Hydraulic diversity strengthens stem growth in temperate forests, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-860, https://doi.org/10.5194/wbf2026-860, 2026.
Changes in climate and land use are posing challenges for organisms at the edges of their geographic ranges. Plant diversity and community composition can alter microenvironments, potentially mitigating novel stressors associated with climate change. However, the mechanisms by which plants support the survival and growth of neighbors are still being uncovered. To conserve biodiversity and ecosystem functionality, it is essential to find ways to support vulnerable species in this rapidly changing world. In this study, we show that tree diversity and community composition can benefit the growth and survival of slower-growing tree species through mechanisms of facilitation and complementarity. We selected four slower-growing species with varying levels of shade tolerance to study in a tree diversity experiment: Quercus alba, Quercus rubra, Acer rubrum and Tilia americana. Throughout the growing season, surveys of phenology, herbivory, and disease along with physiological measurements were taken on these species in three diversity treatments: monocultures, angiosperm-gymnosperm bi-cultures, and diverse 12-species mixtures. The angiosperm-gymnosperm bi-cultures and 12-species mixtures facilitated the survival of slower-growing, shade-tolerant species by generating shade, thereby reducing light-induced stress. Complementarity of soil water usage in the diverse 12-species forests likely contributed to the maintenance of soil water availability that could support higher rates of photosynthesis and growth in the shade-tolerant species. We further found that diverse mixtures of trees created unique conditions that influenced species-specific dynamics of disease and herbivory, which can influence growth and survival. We observed patterns that support the concept of a tradeoff between resource investments in growth and survival in the four slower-growing tree species, but especially in the shade-tolerant T. americana. In facing the challenges of climate change and habitat degradation, we present a mechanistic basis for how tree diversity can increase the growth and survival of slower-growing species by facilitating the reduction in light-stress and contributing to complementarity of local resource usage.
How to cite: Park, M., Guzmán Q., J. A., Scott, A., Clark, I., and Cavender-Bares, J.: Physiological mechanisms of facilitation and complementarity that contribute to overyielding in experimental forests, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-505, https://doi.org/10.5194/wbf2026-505, 2026.
Forest biodiversity plays a critical role in ecosystem functioning, yet it is undergoing rapid and often severe declines worldwide. Understanding how biodiversity loss alters ecosystem processes requires spatially and temporally explicit data on species composition, productivity, and physiological functioning. Because repeated field sampling is costly and logistically challenging, remotely sensed data have become an increasingly valuable tool for monitoring biodiversity and forest functioning at large scales. However, uncertainties remain about how well remotely sensed spectral and thermal traits capture ecological processes at the scale of individual forest plots.
In this study, we used the BIOTREE-Kaltenborn and Bechstedt tree diversity experiments in Germany—where species richness and species composition are known and controlled—to evaluate how biodiversity and species identity shape remotely sensed measures of canopy functioning. We collected airborne imaging spectroscopy, thermal data and sun-induced fluorescence (SIF) at 1-m resolution, and assessed the relationships of these remotely sensed canopy traits with ecosystem functioning, particularly tree productivity measured as cumulative basal area.
Canopy temperature tended to increase with higher tree species richness, and some species consistently exhibited warmer canopies than others. Species identity also played an important role in shaping the relationships between productivity and spectral traits. Overall, SIF was often positively associated with productivity, although this pattern varied among species. In contrast, common greenness indices (NDVI, EVI, CIre) did not always show the expected positive relationships with productivity, suggesting that additional structural or physiological factors may influence these signals. Other indices, such as the indicator for canopy water content, NDWI, or the Chlorophyll Carotenoid Index (CCI), showed mixed or weak associations, depending on the species considered.
Across species, SIF generally decreased with increasing canopy temperatures, which suggests reduced photosynthetic efficiency under warmer conditions. Greenness-related indices were generally positively related to SIF, with some indices showing stronger associations than others.
Our results demonstrate that species identity and functional traits mediate remotely sensed signals of forest functioning. These findings highlight the importance of considering species-specific spectral responses when using remote sensing to monitor biodiversity-driven variation in forest ecosystem functioning.
How to cite: van Moorsel, S., Niederberger, M., Schmid, B., Damm, A., and Schuman, M.: Using a planted tree biodiversity experiment to assess remotely sensed biodiversity-ecosystem functioning relationships, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-317, https://doi.org/10.5194/wbf2026-317, 2026.
Forest expansion through vegetation succession or tree planting is central to global nature-based climate solutions, yet its consequences for biodiversity remain uncertain. Although vegetation densification increases above-ground carbon storage, the associated canopy closure reduces sub-canopy light availability and constrains light-demanding species. Here, we used an integrated modelling framework—combining species distribution models, dynamic vegetation models, and species-specific light-niche filters—to examine how vegetation structure governs carbon storage, light regimes, and the set of plant species that can be supported. We explore this framework under a pan-European scenario of complete land-use retreat to exclude socioeconomic and management variation and isolate these structural dynamics.
Our simulations reveal a fundamental structural constraint in the biodiversity–climate nexus. Vegetation darkening following land-use retreat occurs far faster than carbon accumulation, producing a pronounced early reduction in the proportion of Europe’s flora whose light niches can be satisfied (“supportable plant richness”). This temporal asymmetry yields a strong, initially steep carbon–biodiversity trade-off of modest early carbon gains in exchange for disproportionally large declines in supportable plant richness, a trend that was broadly consistent across Europe’s environmental zones. To test mitigation potential, we ran disturbance-oriented sensitivity scenarios by adjusting mortality processes targeting different demographic stages. Reducing establishment or increasing early-stage mortality partly, though not entirely, reduced the severity of carbon-biodiversity trade-offs by slowing canopy closure and maintaining more light-rich, heterogeneous vegetation while still allowing continued carbon accumulation.
Because many disturbance-mediated biomes worldwide—such as savannas, temperate woodlands and alpine mosaics—harbour species pools dominated by light-demanding taxa, comparable structural dynamics are expected in such regions whenver land-use retreat or reforestation leads to rapid canopy closure. These results highlight that climate-focused forest expansion or land-use retreat can inadvertently reduce the space available for light-demanding biodiversity unless structural heterogeneity, through disturbance or other means, is explicitly considered. Recognizing this structural constraint is essential to reconcile nature-based climate solutions with biodiversity conservation. By linking mechanistic modelling to systemic trade-off analysis, this work advances nexus thinking from concept to quantification, offering a framework for integrated land-use strategies that align carbon storage, disturbance, and biodiversity outcomes.
How to cite: Pang, S., Buitenwerf, R., Zhong, H., Eckes-Shephard, A., Wittenbrink, M., Otryakhin, D., Belda, D., Olin, S., Pugh, T., and Svenning, J.-C.: A structural constraint drives carbon-biodiversity trade-offs under land-use retreat, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-498, https://doi.org/10.5194/wbf2026-498, 2026.
Urban trees play a critical role in supporting biodiversity and enhancing climate resilience, yet these benefits are rarely assessed together. Urbanisation has fragmented habitats and isolated biological communities, making it increasingly important to understand how green infrastructure can deliver multiple benefits simultaneously. Integrating biodiversity and ecosystem service assessments is essential for identifying strategies that support both ecological and community goals. While ecosystem service models, such as i-Tree Eco, provide valuable insights into the benefits of urban trees, they do not account for biodiversity. Combining these models with biodiversity data across multiple taxa can offer a more comprehensive understanding of how nature-based solutions can deliver co-benefits for people and wildlife.
This research investigates how urban trees support birds, bats, invertebrates and vegetation in Coventry, United Kingdom. Using a combination of Passive Acoustic Monitoring, tree beat sampling and quadrat surveys across sites that vary in tree species richness, structure and levels of urbanisation, this study integrates biodiversity data with ecosystem service metrics derived from i-Tree Eco. This approach makes it possible to examine how tree species richness and composition shape biodiversity patterns and ecosystem services, and how these relationships contribute to ecological resilience in urban environments.
Bird surveys indicate a significant positive relationship between bird species richness and tree species richness, highlighting the role of tree diversity in supporting avian communities. Bird species richness was higher at semi-natural sites than at urban sites, though this difference was not statistically significant. Trait data demonstrated that urban bird assemblages were also more functionally homogeneous, suggesting reduced ecological diversity in more built-up environments. Results for bats, invertebrates and vegetation will also contribute to a broader understanding of how urban tree diversity influences multi-taxa biodiversity and ecosystem service provision.
Together, these findings emphasise the importance of tree diversity in sustaining urban biodiversity and supporting ecological resilience. This work contributes to a growing evidence base demonstrating how nature-based solutions can simultaneously address biodiversity loss and climate challenges, providing practical evidence to guide urban planning, tree planting and greenspace management for greener, more resilient cities.
How to cite: Bedford, M., Dehnen-Schmutz, K., Trenchard, L., and Newell, S.: Urban Tree Diversity as a Driver of Biodiversity and Ecosystem Services in Coventry, UK, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-18, https://doi.org/10.5194/wbf2026-18, 2026.
Biodiversity–ecosystem function (BEF) relationships are generally positive and have been documented across nearly all ecosystem types, including marine, freshwater, grassland, and forest systems. Understanding the mechanisms that regulate these relationships offers great potential to guide ecosystem restoration and design productive, resilient ecosystems.
Although agroforestry systems are inherently based on species mixtures and are widely recognized for their capacity to meet growing global food demands while providing multiple ecosystem services - such as carbon sequestration, soil protection, and biodiversity conservation - the study of BEF relationships within agroforestry remains largely underexplored. Only a limited number of biodiversity-manipulation experiments have been established globally in this sector.
To address this gap, a large-scale agroforestry BEF experiment has been established at the experimental farm of the University of Sassari, managed by the Centro Biodiversità Vegetale and Innovative Agriculture units (Surigheddu, Sardinia) and funded by the National BIodiversity Future Center (NextGenerationEU). The experimental site covers approximately 10 hectares and is organized into three blocks, each consisting of 30 plots (35 m × 35 m). One of the main objectives of the experiment is to identify successful species mixtures for restoring productivity and ecosystem functioning in Mediterranean marginal lands.
Nine species representing three life forms—trees, shrubs, and annuals—typical of Mediterranean drought-resistant vegetation were selected: Prunus amygdalus, Ceratonia siliqua, Olea europaea, Ficus carica, Quercus ilex (inoculated with Tuber aestivum), Punica granatum, Pistacia lentiscus, Myrtus communis, and one annual species that changes each year.
All nine species are planted both as monocultures and in two-, three-, and four-species mixtures. The mixtures were designed based on either traditional associations (e.g., olive and fig) or hypothesized positive functional interactions, such as pairing deep- and shallow-rooted species to enhance resource complementarity and system resilience.
This experimental device constitutes a unique Living Lab within the NBFC framework and a core node of the BEF-Italy network, providing an open platform to investigate biodiversity–functioning linkages, promote nature-based solutions, and co-design climate-resilient agroforestry systems for Mediterranean landscapes.
How to cite: Brundu, G., Mereu, S., Sirca, C., Mulas, M., Tiloca, M. T., Deidda, A., Lozano, V., Chahine, T., Gambella, F., Porceddu, A., Muys, B., and Spano, D.: Biodiversity Manipulation Experiment in Agroforestry: a New Permanent Site in Sardinia (Italy), World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-790, https://doi.org/10.5194/wbf2026-790, 2026.
The structure of tropical forests has been identified as one of the key determinants of the effects of diversity loss on productivity, carbon storage, and the long-term stability of restored tropical forest stands. However, the emergence of complex structure in mixed-species stands relative to the structural conditions of mature natural forests depends on how species interact with each other and with the abiotic components, which vary across environmental conditions. Yet we still lack a clear understanding of how the relationship between tree diversity and forest structural complexity is shaped by biotic and abiotic factors that exert regional control, as well as the mechanisms underlying these influences.
Using high-resolution three-dimensional models of forest structure generated from terrestrial laser scanning across species-diversity gradients in ten biodiversity experiments, we assessed how diversity influences structural integrity relative to natural forests. We also quantified how changes in tree diversity affect structural complexity within and across tropical regions. The experiments spanned 5 climate zones and 10 soil types with distinct taxonomic compositions and a diverse range of tree species richness, providing a robust range of conditions to support generalizable inferences.
We found that increasing species diversity in mixtures led to greater stand structural complexity, but the strength of the diversity effect differed markedly across regions, with greater variability between than within climate zones. Increasing species diversity also contributed to greater structural integrity, and this pattern was linked primarily to increased vertical stratification of tree crowns. We found no clear evidence that the impact of tree species on structural complexity is significantly related to regional context, but our results showed that the overall diversity effect varied in magnitude and importance depending on region-specific differences in water availability and stand age. These findings provide further evidence of the value of stand structure in determining the consequences of biodiversity loss, which is relevant for designing restoration strategies in the tropical region.
How to cite: Onyiriagwu, M. and Zemp, D. C.: Optimizing Forest Structural Integrity through Tree Diversity: Evidence from Tropical Diversity Experiments, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-796, https://doi.org/10.5194/wbf2026-796, 2026.
