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Aim Forest carbon storage is the result of a multitude of interactions among biotic and abiotic factors. Our aim was to use an integrative approach to elucidate mechanistic relationships of carbon storage with biotic and abiotic factors in the natural forests of temperate Australia, a region that has been overlooked in global analyses of carbon‐biodiversity relations. Location South‐eastern Australia. Time period 2010–2015. Major taxa studied Forest trees in 732 plots. Methods We used the most comprehensive forest inventory database available for south‐eastern Australia and structural equation models to assess carbon‐storage relationships with biotic factors (species or functional diversity, community‐weighted mean (CWM) trait values, structural diversity) and abiotic factors (climate, soil, fire history). To assess the consistency of relationships at different environmental scales, our analyses involved three levels of data aggregation: six forest types, two forest groups (representing different growth environments), and all forests combined. Results Structural diversity was consistently the strongest independent predictor of carbon storage at all levels of data aggregation, whereas relationships with species‐ and functional‐diversity indices were comparatively weak. CWMs of maximum height and wood density were also significant independent predictors of carbon storage in most cases. In comparison, climate, soil, and fire history had only minor and mainly indirect effects via biotic factors on carbon storage. Main conclusions Our results indicate that carbon storage in our temperate forests was underpinned by tree structural diversity (representing efficient utilisation of space) and by CWM trait values (representing selection effects) more so than by tree species richness or functional diversity. Abiotic effects were comparatively weak and mostly indirect via biotic factors irrespective of the environmental range. Our study highlights the importance of managing forests for functionally important species and to maintain and enhance their structural complexity in order to support carbon storage.

1. Forest recovery following management interventions is important to maintain ecosystem functioning and the provision of ecosystem services. It remains, however, largely unclear how above-ground biomass (AGB) recovery of species-rich tropical forests is affected by disturbance intensity and post-disturbance (remaining) tree-community attributes, following logging and thinning interventions. 2. We investigated whether annual AGB increment (AAGB) decreases with management-related disturbance intensity (disturbance hypothesis), and increases with the diversity (niche-complementarity hypothesis) and the community-weighted mean (CWM) of acquisitive traits of dominant species (biomass-ratio hypothesis) in the remaining tree community. 3. We analysed data from a long-term forest-management experiment in the Brazilian Amazon over two recovery periods: post-logging (1983-1989) and post-thinning (1995-2012). We computed the ΔAGB of surviving trees, recruit trees and of the total tree community. Disturbance intensity was quantified as basal area reduction and basal area remaining. Remaining diversity (taxonomic, functional and structural) and CWM of five functional traits linked to biomass productivity (specific leaf area, leaf nitrogen and phosphorous concentration, leaf toughness and wood density) were calculated for the post-intervention inventories. Predictors were related to response variables using multiple linear regressions and structural equation modelling. 4. We found support for the disturbance hypothesis in both recovery periods. AGB increment of survivors and of the total tree community increased with basal area remaining, indicating the importance of remaining growing stock for biomass recovery. Conversely, AGB increment of recruit trees increased with basal area reduction because changes in forest structure increased resource availability for young trees. We did not find consistent support for the niche-complementarity and biomass-ratio hypotheses, possibly because of a high redundancy in these extremely species-rich forests. 5. Synthesis and applications. The intensity of disturbance through management, expressed as basal area reduction and basal area remaining, was consistently more important for explaining forest biomass recovery following harvesting and thinning than remaining diversity or trait composition. This points to the importance of controlling logging and thinning intensity in forests of the eastern Amazon. Given the high intervention intensities applied in this experiment, it is likely that low to moderate harvesting intensities permitted by the current legislation for the Brazilian Amazon (30 m³/ha) will not impair biomass recovery in these forests.

Litter decomposition is a key process of nutrient and carbon cycling in terrestrial ecosystems. The decomposition process will likely be altered under ongoing climate change, both through direct effects on decomposer activity and through indirect effects caused by changes in litter quality. We studied how hydrological change indirectly affects decomposition via plant functional community restructuring caused by changes in plant species’ relative abundances (community‐weighted mean (CWM) traits and functional diversity). We further assessed how those indirect litter quality effects compare to direct effects. We set up a mesocosm experiment, in which sown grassland communities and natural turf pieces were subjected to different hydrological conditions (dryness and waterlogging) for two growing seasons. Species‐level mean traits were obtained from trait databases and combined with species’ relative abundances to assess functional community restructuring. We studied decomposition of mixed litter from these communities in a common “litterbed.” These indirect effects were compared to effects of different hydrological conditions on soil respiration and on decomposition of standard litter (direct effects). Dryness reduced biomass production in sown communities and natural turf pieces, while waterlogging only reduced biomass in sown communities. Hydrological stress caused profound shifts in species’ abundances and consequently in plant functional community composition. Hydrologically stressed communities had higher CMW leaf dry matter content, lower CMW leaf nitrogen content, and lower functional diversity. Lower CWM leaf N content and functional diversity were strongly related to slower decomposition. These indirect effects paralleled direct effects, but were larger and longer‐lasting. Species mean traits from trait databases had therefore considerable predictive power for decomposition. Our results show that stressful soil moisture conditions, that are likely to occur more frequently in the future, quickly shift species’ abundances. The resulting functional community restructuring will decelerate decomposition under hydrological stress. We show for the first time not only that community‐weighted mean functional traits and functional diversity rapidly change under hydrological stress (dryness and waterlogging), but also that these shifts strongly decelerate litter decomposition. These indirect effects on litter decomposition via changes in litter quality parallel direct effects on decomposer activity, but are even larger in magnitude and last longer. To our knowledge, this is the first study showing a link between effects of hydrological conditions on functional community structure with consequences for an ecosystem process, such as litter decomposition.

Background and aims Hostile soil conditions have a global impact on crop production. While root traits of individual plant species adapted to specific hostile soils are well studied, a comprehensive synthesis of how to use diversified cropping systems with complementary root growth strategies to adapt to and remediate hostile soils is lacking. Scope We begin by providing definitions, categorizations, and global distribution of hostile soils, followed by a synthesis of recent advances in below-ground niche complementarity or facilitative root interactions among crop species in diverse cropping systems across various hostile soils. Lastly, we highlight the significance of cultivating a robust understanding of root adaptations for crop diversification in hostile soils for future research. Conclusion Diversified cropping systems that incorporate complementary root growth strategies can efficiently utilize nutrients and mitigate abiotic stress in hostile soils, such as nutrient deficiency, aridity, and waterlogging conditions. Furthermore, intercropping hyperaccumulator plants or halophytes with crops is effective in reducing metal or salt accumulation in target crops grown in contaminated or saline-alkali soils, respectively. Cover crops could create biopores for succeeding crop roots in compacted soils, while diversified cropping systems aid in preventing additional soil erosion in eroded areas. Leveraging diverse root traits can also contribute to the suppression of soil‑borne diseases and pests within intercropping setups. Enhancing diversified cropping systems necessitates the application of novel methods and technologies for root studies. This multifaceted approach is crucial for sustaining yield under the challenges posed by multiple hostile soil conditions, especially within the context of climate change.

Plant invasions have consistently been shown to cause significant reductions in the diversity of recipient plant communities; an effect that can cascade through ecosystems to impact the stocks and flows of nutrients and energy as well as the diversity of higher trophic levels. However, the manner in which invasive plants alter ecosystem functioning and trophic interactions is highly variable can occur through the direct effects of the invader's abundance and its indirect effects via changes in community diversity. Understanding the nature of these interactions between plant invasion, community diversity and ecosystem functioning can provide insight for ecosystem managers. We evaluated whether plant invasion alters the relationship between biodiversity and ecosystem function (BEF) by comparing BEF models that either include or subtract the diversity and function values associated with the invasive vine, Vincetoxicum rossicum. To do this, we (1) characterize V. rossicum within the functional trait space of the regional species pool, (2) assess how different components of plant biodiversity vary along a V. rossicum invasion gradient, and (3) examine how V. rossicum invasion affects BEF relationships and trophic interactions, both at the plot-scale and incrementally along a site-level invasion gradient. In general, we found that V. rossicum invasion was associated with significant declines in plant community diversity across a suite of biodiversity measures; a consequence of V. rossicum's functional trait structure (height and specific leaf area). We also found that V. rossicum invasion resulted in significantly greater productivity (i.e., dominance effects in the inclusion model), but also that the diversity of the remaining resident community was positively associated with productivity (i.e., niche complementarity in the subtraction model). Further, we observed that while the relationship between flower cover and pollinator diversity was positive for both the inclusion and subtraction models, this relationship was stronger in the absence of V. rossicum. Our findings suggest that while plant invasion can result in enhanced productivity via dominance effects, this comes at the cost of significant declines in diversity. However, it is also the case that remaining resident diversity can exhibit positive effects on multiple functions and support for higher trophic levels.

1. There is increasing evidence that species diversity enhances the temporal stability (TS) of community productivity in different ecosystems, although its effect at the population and tree levels seems to be negative or neutral. Asynchrony in species responses to environmental conditions was found to be one of the main drivers of this stabilizing process. However, the effect of species mixing on the stability of productivity, and the relative importance of the associated mechanisms, remain poorly understood in forest communities. 2. We investigated the way mixing species influenced the TS of productivity in Pinus sylvestris L. and Fagus sylvatica L. forests, and attempted to determine the main drivers among overyielding, asynchrony between species annual growth responses to environmental conditions, and temporal shifts in species interactions. We used a network of 93 experimental plots distributed across Europe to compare the TS of basal area growth over a 15-year period (1999-2013) in mixed and monospecific forest stands at different organizational levels, namely the community, population and individual tree levels. 3. Mixed stands showed a higher TS of basal area growth than monospecific stands at the community level, but not at the population or individual tree levels. The TS at the community level was related to asynchrony between species growth in mixtures, but not to overyielding nor to asynchrony between species growth in monospecific stands. Temporal shifts in species interactions were also related to asynchrony and to the mixing effect on the TS. 4. Synthesis. Our findings confirm that species mixing can stabilize productivity at the community level, whereas there is a neutral or negative effect on stability at the population and individual tree levels. The contrasting findings regarding the relationships between the temporal stability and asynchrony in species growth in mixed and monospecific stands suggest that the main driver in the stabilizing process may be the temporal niche complementarity between species rather than differences in species' intrinsic responses to environmental conditions.

Background Soils harbour a remarkable diversity of interacting fungi, bacteria, and other microbes: together these perform a wide variety of ecological roles from nutrient cycling and organic matter breakdown, to pathogenic and symbiotic interactions with plants. Many studies demonstrate the role of microbes in plant-soil feedbacks and their interactions with plants. However, interactions among microbes are seldom addressed, and there is no consensus regarding the nature and outcomes of interactions among microbial functional guilds. Scope Here, we critically review what is known about microbe-microbe interactions among functional guilds within the plant-soil system, with the aim to initiate a path to disentangling the “microbe black-box”. Our review confirms that the nature of microbial interactions among major functional guilds is explained by niche theory. This means that, among microbes, a competitive relationship is likely when their benefits to plants, source of carbon and nutrients, or nutrient scavenging mechanisms overlap, while a neutral-to-facilitative relationship is likely when these microbial traits differ or complement each other. Conclusions We highlight the numerous knowledge gaps and provide a framework to characterise microbe-microbe interactions that offers insight into the contributions of microbes to key ecosystem functions such as carbon sequestration and nutrient cycling.

Phosphorus (P), iron (Fe) and zinc (Zn) are essential elements for plant growth and development, but their availability in soil is often limited. Intercropping contributes to increased P, Fe and Zn uptake and thereby increases yield and improves grain nutritional quality and ultimately human health. A better understanding of how intercropping leads to increased plant P, Fe and Zn availability will help to improve P-fertilizer-use efficiency and agronomic Fe and Zn biofortification. This review synthesizes the literature on how intercropping of legumes with cereals increases acquisition of P, Fe and Zn from soil and recapitulates what is known about root-to-shoot nutrient translocation, plant-internal nutrient remobilization and allocation to grains. Direct interspecific facilitation in intercropping involves below-ground processes in which cereals increase Fe and Zn bioavailability while companion legumes benefit. This has been demonstrated and verified using isotopic nutrient tracing and molecular analysis. The same methodological approaches and field studies should be used to explore direct interspecific P facilitation. Both niche complementarity and interspecific facilitation contribute to increased P acquisition in intercropping. Niche complementarity may also contribute to increased Fe and Zn acquisition, an aspect poorly understood. Interspecific mobilization and uptake facilitation of sparingly soluble P, Fe and Zn from soil, however, are not the only determinants of the concentrations of P, Fe and Zn in grains. Grain yield and nutrient translocation from roots to shoots further influence the concentrations of these nutrients in grains.

Tropical forests are globally important, but it is not clear whether biodiversity enhances carbon storage and sequestration in them. We tested this relationship focusing on components of functional trait biodiversity as predictors. Data are presented for three rain forests in Bolivia, Brazil and Costa Rica. Initial above‐ground biomass and biomass increments of survivors, recruits and survivors + recruits (total) were estimated for trees ≥10 cm d.b.h. in 62 and 21 1.0‐ha plots, respectively. We determined relationships of biomass increments to initial standing biomass (AGBᵢ), biomass‐weighted community mean values (CWM) of eight functional traits and four functional trait variety indices (functional richness, functional evenness, functional diversity and functional dispersion). The forest continuum sampled ranged from ‘slow’ stands dominated by trees with tough tissues and high AGBᵢ, to ‘fast’ stands dominated by trees with soft, nutrient‐rich leaves, lighter woods and lower AGBᵢ. We tested whether AGBᵢand biomass increments were related to the CWM trait values of the dominant species in the system (the biomass ratio hypothesis), to the variety of functional trait values (the niche complementarity hypothesis), or in the case of biomass increments, simply to initial standing biomass (the green soup hypothesis). CWMs were reasonable bivariate predictors of AGBᵢand biomass increments, with CWM specific leaf area SLA, CWM leaf nitrogen content, CWM force to tear the leaf, CWM maximum adult height Hₘₐₓand CWM wood specific gravity the most important. AGBᵢwas also a reasonable predictor of the three measures of biomass increment. In best‐fit multiple regression models, CWMHₘₐₓwas the most important predictor of initial standing biomass AGBᵢ. Only leaf traits were selected in the best models for biomass increment; CWM SLA was the most important predictor, with the expected positive relationship. There were no relationships of functional variety indices to biomass increments, and AGBᵢwas the only predictor for biomass increments from recruits. Synthesis. We found no support for the niche complementarity hypothesis and support for the green soup hypothesis only for biomass increments of recruits. We have strong support for the biomass ratio hypothesis. CWMHₘₐₓis a strong driver of ecosystem biomass and carbon storage and CWM SLA, and other CWM leaf traits are especially important for biomass increments and carbon sequestration.

Pollination is a key ecological function of most terrestrial ecosystems. Decades of research on single-trophic-level communities, particularly plant communities, have helped to build the foundation of diversity–function theory. Yet as it stands, this theory appears to be less useful for intertrophic-level functions such as pollination, as evidenced by empirical findings that are often inconsistent with theoretical expectations. In this review, we evaluate how canonical diversity–function theory has been applied to pollination function, focusing on empirical studies of the mechanisms that drive pollinator diversity–function relationships. We first identified key features of pollination function that have hampered reconciliation with current theory. We then examined terminology for mechanisms used to discuss the findings from pollinator diversity–function studies that are sometimes inconsistent with established ecological concepts. We propose a revised diversity–function framework and describe two noncanonical diversity–function mechanisms that are particularly applicable to pollination. The first, “interactive functional complementarity,” was identified previously but remains overlooked. The second, a new diversity–function mechanism, “functional enhancement,” occurs when pollinator diversity increases within-niche activity. Finally, we discuss experimental approaches necessary to detect diversity–function effects in pollination.