Biology subjects

Bradler, P. M.

Publications and source records attributed to Bradler, P. M..

7 recordsLinked to original sources

bioRxiv2025

Microclimatic heterogeneity is associated with forest structural complexity and biodiversity

Forest microclimates, their dependence on forest structure, and their impact on biodiversity are crucial for future forest management under climate change. However, standard approaches for measuring forest microclimates do not capture within-plot heterogeneity, which, according to the habitat heterogeneity hypothesis, is a key driver of local biodiversity. We quantified horizontal and vertical microclimatic heterogeneity within 30 broad-leaved forest plots in Central Europe using a three-dimensional design with high spatial resolution. Moreover, we examined whether microclimatic heterogeneity differs among silvicultural treatments and whether it can be predicted using forest structure indices derived from laser scanning. Additionally, we explored the relationship between microclimatic heterogeneity and biodiversity. In the understory of canopy gaps, warm and cold habitats co-existed in close proximity, leading to a high horizontal microclimatic heterogeneity. In closed stands with high structural complexity, we found steep gradients of increasing temperature and vapor pressure deficit from the ground to the canopy during mid-day. Canopy cover and forest structural complexity were strong indicators of microclimatic heterogeneity. We found positive relationships between herb layer temperature heterogeneity and the diversity of plants, Hymenoptera, and Diptera. Our results demonstrate that single-point measurements fail to capture the substantial microclimatic heterogeneity within plots, potentially misrepresenting the conditions experienced by forest species. However, laser scanning provides reliable indicators for within- plot microclimatic heterogeneity. With canopy gaps featuring high horizontal microclimatic heterogeneity and promoting the biodiversity of several taxonomic groups, we argue that managing forests for maximized temperature buffering should not be the only strategy to conserve forest biodiversity. HighlightsO_LIHigh small-scale horizontal microclimatic heterogeneity in canopy gaps C_LIO_LISteep vertical microclimatic gradients in closed-canopy forests C_LIO_LICanopy cover and structural complexity: indicators for microclimatic heterogeneity C_LIO_LIPositive relationship between herb layer temperature heterogeneity and biodiversity C_LI

ecology↗

bioRxiv2025

Old growth attributes by chain saw: how between-patch heterogeneity changes the metacommunities of beetles in temperate forests

Metacommunity theory has expanded our understanding of how spatial dynamics and local interactions influence species communities. Different assembly archetypes, reflecting different roles of species differences, habitat differences, and dispersal have been described, but we lack empirical studies specifically in terrestrial habitats testing which archetype is most important. In a replicated design we experimentally enhanced structural between-patch heterogeneity in homogeneous production forests and developed a statistical framework controlling for sample incompleteness to detect different metacommunity processes. Meta-analyses on >100K individuals of >1.3K beetle species showed an increase of [~]60 species in heterogenized forests at {gamma}-level promoted by increasing -diversity consistent with the mass-effect and an increase of {beta}-diversity by [~]10% supporting species-sorting. Additionally, we tested {beta}-deviations from random assembly as a proxy of neutral processes. Findings indicate that enhancing structural heterogeneity can shift forests from patch-dynamics dominance towards mass-effect and species-sorting, offering a promising pathway to restore biodiversity in managed landscapes.

ecology↗

bioRxiv2025

Enhanced forest heterogeneity drives stronger functional than taxonomic shifts in soil nematodes

Production forests are often managed primarily for timber production, leading to biotic homogenization and reduced biodiversity. To explore strategies that promote biodiversity while maintaining timber yields, we conducted a large-scale experiment in eight German forests. We manipulated structural {beta}-complexity, i.e., the heterogeneity of structural elements across forest patches, by experimentally introducing variation in canopy gaps and different types of deadwood across 156 plots of 50 x 50 m each, to investigate its effects on forest biodiversity. We analyzed soil nematode communities, which are important bioindicators and contributors to ecosystem processes, by assessing taxonomic and functional diversity across patch (), site ({gamma}), and between-patch ({beta}) scales using Hill-Chao numbers. Additionally, we tested whether environmental variables explain nematode diversity responses. Our results show that functional diversity is more responsive than taxonomic diversity, with increased {beta}-diversity of common and frequent taxa alongside simultaneous declines in - and {gamma}-diversity. This pattern suggests a shift toward more specialized nematode communities in response to the intervention. Moreover, we found that site-specific conditions, such as sand content and understory biomass, modulated these effects. Overall, our findings reveal complex, scale-dependent responses of nematode diversity to aboveground forest structural changes, emphasizing the need to consider environmental context in forest biodiversity management. This study represents an important first step toward understanding and enhancing soil biodiversity at management-relevant spatial scales.

ecology↗

bioRxiv2025

Enhancing structural heterogeneity in managed forest landscapes promotes gamma but not beta diversity in understorey plant communities

O_LIAlthough habitat heterogeneity is known to enhance local species diversity, the effects of management-driven structural heterogeneity on understorey plant communities across spatial scales remain poorly understood, despite their crucial role for forest biodiversity and ecosystem functioning. C_LIO_LITo analyse how forest understorey plant communities respond to an enhancement of structural heterogeneity in managed forests, we established 11 experimental sites consisting of two paired forest landscapes, an untreated homogenous control and a treatment district (ESBC). In treatment districts, structural heterogeneity was enhanced through different combinations of local patch-scale manipulations of light and deadwood features, leading to greater between-patch heterogeneity at the landscape scale. We performed a meta-analysis across these 11 sites using a Hill-Chao number and sample coverage standardisation framework. C_LIO_LIGamma diversity increased across taxonomic, functional and phylogenetic facets in structurally heterogeneous forests (ESBC districts) via higher alpha diversity. This effect was positively associated with heterogeneity in light availability between forest patches, but not with their mean light availability. In contrast, we found no support that species turnover among patches (i.e., beta diversity) significantly contributes on average to the observed increase in gamma diversity. However, both the direction and magnitude of beta diversity responses varied substantially among landscapes. C_LIO_LIOn average, structurally heterogeneous forests supported higher species richness for both open and closed forest habitat species. C_LIO_LISynthesis and applications: Our findings highlight the benefits of enhancing structural heterogeneity for understorey plant diversity in managed forest landscapes. Specifically, management strategies that create a spatial mosaic of interventions, such as combining single-tree removal with group felling, can increase the variety of light niches among forest patches, thereby supporting the conservation of a wide range of understorey plant species, including forest specialists. C_LI

ecology↗

bioRxiv2025

Enhancing experimentally the structural heterogeneity of forests increase soil fungal diversity but functional lifestyles in contrasting ways

Fungal communities in soils are highly diverse both in species and functions forming a major backbone of forest ecosystems. Recent observational high-throughput-sequencing studies have shown that fungal diversity is correlated with resource availability and climate across different spatial scales. However, the underlying mechanisms remain poorly understood. Across Germany, we experimentally manipulated 11 typically homogeneous, broadleaf production forests to increase their between-patch-heterogeneity (ESBC) and compared them with a control forest. In specific, we enhanced light availability via canopy openness and deadwood resources in the ESBC treatments. Fungal communities were determined by metabarcoding at 234 patches and analysed using a novel meta-analytical approach for pairwise comparisons of taxonomic and phylogenetic diversity along Hill numbers. We hypothesized that {gamma}-diversity is primarily driven by {beta}-diversity increasing with canopy mediated microclimate variability and secondarily by -diversity increasing with resource availability. Furthermore, we expected an increase in {gamma}-diversity by unique phylogenetic lineages supporting the insurance hypothesis. Our results showed a significant increase in {gamma}-diversity in ESBC forests, first by - and second by {beta}-diversity, both of which were influenced mainly by microclimate and not resource availability. The increase of phylogenetic diversity with ESBC was weak indicating functional similarity of species. Analysis of symbiotic, saprotrophic and parasitic fungal assemblages revealed contrasting effects of resource availability and microclimate across the scales. As in the UN Decade of Ecosystem Restoration many forest managers aim to increase the heterogeneity of forests and are simultaneously face rising tree mortality, our study provides first robust empirical evidence for the varying effects of forest gaps and deadwood on fungal diversity across -, {beta}-, {gamma}-scales for this major kingdom.

ecology↗

bioRxiv2025

Inconsistent short-term effects of enhanced structural complexity on soil microbial properties across German forests

Structural and biotic homogenization can result from forestry practices that lack promotion of canopy gaps and deadwood. This can lead to biodiversity loss and impaired ecosystem functions. Enhancing structural complexity (ESC) has been proposed to counteract these effects, but its impact on soil properties remains insufficiently understood. Overall, we hypothesize that ESC enhances soil abiotic properties, their spatial variability, and microbial functioning, with effects modulated by environmental context and increasing over time. Data were collected from 148 patches (50 x 50 m) in eight beech forests across Germany. In half of the patches, structural complexity was enhanced by felling 30% of the basal area of living trees through two spatial patterns--aggregated (one large gap) and distributed (small gaps)--combined with leaving or removing deadwood (stumps, logs, and snags). The other half served as controls, representing typically managed, homogeneous production forests. Soil C:N, C%, and N% increased near deadwood. Soil microbial biomass and activity were significantly affected in three of eight forest sites, with effects ranging from -30% to +62%. Higher soil water content was associated with increased microbial biomass, and greater understorey biomass correlated with a lower microbial respiratory quotient. No temporal trends were observed over five years. Although soil properties showed resistance to structural interventions, site-specific effects underline the importance of soil moisture and the understorey vegetation for microbial functioning. Further research building on our results is needed to develop practical forest management strategies to clarify how structural complexity may support soil functioning and ecosystem resilience. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/664741v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@10790f2org.highwire.dtl.DTLVardef@1bd2f95org.highwire.dtl.DTLVardef@17eed6dorg.highwire.dtl.DTLVardef@15a049_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights- Deadwood addition increases soil C%, N%, and the soil C:N ratio - Enhanced structural complexity alters soil microbial properties in site-specific ways - Soil water content changes are linked to shifts in microbial biomass - Understorey biomass changes are linked to shifts in the respiratory quotient

ecology↗

bioRxiv2024

Diversity-enhanced canopy space occupation and leaf functional diversity jointly promote overyielding in tropical tree communities

Understanding the mechanisms that drive biodiversity-productivity relationships is critical for guiding forest restoration. Although complementarity among trees in the canopy space has been suggested as a key mechanism for greater productivity in mixed-species tree communities, empirical evidence remains limited. Here, we used data from a tropical tree diversity experiment to disentangle the effects of tree species richness and community functional characteristics (community-weighted mean and functional diversity of leaf traits) on canopy space filling, and how these effects are related to overyielding. We found that canopy space filling was largely explained by species identity effects rather than tree diversity effects. Communities with a high abundance of species with conservative leaf traits were those with most densely packed canopies. Overall, a higher canopy space filling translated into an enhanced wood productivity, with communities associated with a high taxonomic and functional diversity being the most productive. Importantly, most communities (83%) produced more wood volume than the average of their constituent species in monoculture (i.e. most communities overyielded). Our results show that overyielding increased with leaf functional diversity and positive net biodiversity effects on canopy space filling, which mainly arose due to a high taxonomic diversity. These findings suggest that both taxonomic diversity-enhanced canopy space filling and canopy leaf diversity are important drivers for overyielding in mixed-species forests. Consequently, restoration initiatives should promote stands with functionally diverse canopies by selecting tree species with large interspecific differences in leaf nutrition, as well as leaf and branch morphology to optimize carbon capture in young forest stands.

ecology↗