Multifaceted functional diversity for multifaceted crop yield: Towards ecological assembly rules for varietal mixtures

Contrasted reaction norms of wheat yield in pure vs mixed stands explained by tillering plasticities and shade avoidance

Switchgrass (Panicum virgatum L.) is an important emerging biofuel crop. In breeding nurseries, plants are typically widely spaced; however, production is in densely planted swards. This disconnect may hinder cultivar improvement. This study measured the efficiency of low‐density, spaced‐plant selection on improving biomass and ethanol yield in a high‐density, simulated sward. Fifty‐six full‐sib families were clonally replicated in two adjacent nurseries in Knoxville, TN. The spaced‐plant nursery consisted of single plants on 1‐m centers. The simulated‐sward nursery was created by planting four by seven plants on 0.33‐m centers with 1‐m alleys. In 2013 and 2014, biomass yield, ethanol yield, and morphological traits were evaluated. Trait means, correlations, and efficiency of indirect selection (E) were calculated. Significant interaction (p < 0.05) between year and nursery was observed for all traits except ethanol yield. The identified high‐yielding ideotype differed between biomass and ethanol yield and between spaced‐plant and simulated‐sward nurseries. Selection under spaced‐plant conditions for simulated‐sward performance was efficient for ethanol yield (E = 0.96) but highly inefficient for biomass yield (E = −0.31). Several morphological traits evaluated under spaced‐plant conditions were identified as efficient indirect selectors for simulated‐sward biomass or ethanol yield. Results suggest selections for sward biomass yield may be more appropriate under sward‐like conditions, but that spaced‐plant nurseries are efficient for selection of ethanol yield performance under sward‐like conditions and for indirect selection of sward yield traits using morphological traits.

SummaryThe roles that functional traits and/or evolutionary history of species from co‐occurring trophic groups have in determining community recovery following disturbance are poorly understood. Functional traits help determine how species interact with their environment, thus functional traits are likely to change with time since logging. However, traits of species may also be phylogenetically constrained depending on their evolutionary history. Because beetles are trophically diverse, the effects of phylogenetic and functional aspects of community recovery can be compared between co‐occurring trophic groups.Using a chronosequence of forest ages following logging, we applied a novel combination of functional trait and phylogenetic approaches to assess the extent to which taxonomic, functional and phylogenetic composition recovered after logging, and if these dimensions of composition approached those characteristic of mature forests, for both predators and decomposers/primary consumers. We also examined to what extent functional traits of both trophic groups were phylogenetically conserved.Predator functional composition had recovered ∼45 years after logging, and this recovery preceded taxonomic recovery. Neither taxonomic nor functional composition had recovered for the decomposer/primary consumer communities by this time.In contrast to decomposers/primary consumers, predator community recovery had no distinct phylogenetic signature, yet predator functional traits were more phylogenetically conserved than decomposers/primary consumer functional traits.Trait syndromes that characterise forest recovery stages are identified and provide a basis for future work on community re‐assembly following disturbance.We demonstrate differential recovery of co‐occurring beetle trophic groups following disturbance. We show that functional and phylogenetic composition may be disconnected from taxonomic composition; highlighting the advantages of integrating understanding of these three potentially independent components of ecological diversity to enable deeper understanding of animal community composition.

Functional composition is an important driver of aboveground biomass (AGB) variation in the tropical forest and has been demonstrated through the mass ratio hypotheses (MRH) that explain how dominant species and their functional traits have an important role in the AGB increase. We hypothesized that AGB stock of tree species is promoted by the simultaneous effects of restoration treatments and Technosol quality through functional trait composition. We tested the main effects of taxonomic, stand structural, functional attributes and abiotic factors undergoing different restoration methods (planting of nursery‐grown seedlings, seeding, and natural regeneration) and the effect of Technosol fertilization on AGB using different linear models. The functional traits were based on the community‐weighted mean of the community of values of functional traits related to MRH. Stems and biomass distribution were categorized into the following functional groups: successional strategy, dispersal syndrome, nitrogen fixation, wood density (WD). As expected, during early restoration stage, the pioneer and anemochoric species were dominants mainly represented by naturally regenerated stems. However, the autochoric dispersal and nitrogen‐fixing tree species were biomass dominant groups in active restoration, driven mostly bySenna alatawhich had high abundance and WD. We found that high WD and active restoration methods determine higher AGB stock on mining tailings where natural regeneration is limited. We conclude that functional composition reverses the effects of species richness and abundance on AGB tenting the MRH. Therefore, the effects of functional composition and restoration methods are key predictors on ecosystem functioning during forest restoration.

Grain yield increase in cereal variety mixtures: A meta-analysis of field trials

Indicators of biomass and methane yields in vegetated buffer strips

Functional trait composition of plant communities has been proposed as a helpful key for understanding the mechanisms of biodiversity effects on ecosystem functioning. In this study, we applied a step-wise modeling procedure to test the relative effects of taxonomic diversity, functional identity, and functional diversity on macrophytes community productivity along water depth gradient. We sampled 42 plots and 1513 individual plants and measured 16 functional traits and abundance of 17 macrophyte species. Results showed that there was a significant decrease in taxonomic diversity, functional identity (i.e., stem dry mass content, leaf [C] and leaf [N]), and functional diversity (i.e., floating leaf, mean Julian flowering date and rooting depth) with increasing water depth. For the multiple-trait functional diversity (FD) indices, functional richness decreased, while functional divergence increased with water depth gradient. Macrophyte community productivity was strongly determined by functional trait composition within community, but not significantly affected by taxonomic diversity. Community-weighted means (CWM) showed a two times higher explanatory power relative to FD indices in determining variations in community productivity. For nine of sixteen traits, CWM and FD showed significant correlations with community productivity, although the strength and direction of those relations depended on selected trait. Furthermore, functional composition in a community affected productivity through either additive or opposite effects of CWM and FD, depending on the particular traits being considered. Our results suggested both mechanisms of mass ratio and niche complementarity can operate simultaneously on variations in community productivity, and considering both CWM and FD would lead to a more profound understanding of traits–productivity relationships.

Crop yield decline, primarily caused by soil erosion, is a major challenge in rain‐fed agriculture. Massive soil and water conservation (SWC) practices are conducted each year in the country of Ethiopia, including the study sites, to tackle the problems, but there is not enough information about the impacts those practices on crop yields in the study area. The impacts of different soil conservation practices on finger millet yield ( Eleusine coracana (L.) Gaertn.) were evaluated on conserved and non‐conserved croplands during the 2021/2022 cropping season. The experimental fields were blocked based on slope classes to account for topographic variation. A total of 27 plots having 3.2 × 3 m size were established. The highest plant height (73.24 cm), biomass yield (2.50 t ha − 1 ), and grain yield (1.57 t ha − 1 ) were recorded from soil bunds stabilized with grass. The interaction of conservation practices and slope gradient positively influenced plant height, biomass, and grain yield. Biological soil conservation practices + foot slope yielded the highest plant height (79.71 cm), biomass (3.08 t ha − 1 ), and grain yield (1.57 t ha − 1 ). The result showed that there was a significant difference of millet yield and yield components in conserved and non‐conserved fields ( p < 0.05). This study implies that implementing suitable soil conservation techniques based on slope characteristics is the best solution to improve finger millet yield in northwestern Ethiopia. It is recommended that farmers adopt slope‐specific SWC measures, such as soil and grass‐stabilized bunds, to reduce erosion and improve soil fertility and finger millet yield.

Processed corn ( Zea mays L.) stover (PCS), defined as finely ground stover with or without additions, could be a potential alternative to peat in greenhouse mixes. However, this option has not yet been examined. We performed two split-plot experiments (1 and 2) with tomatoes ( Solanum lycopersicum L.) and marigolds ( Tagetes patula L.) as main plots. Expt. 1 involved five stover rates (0%, 25%, 50%, 75%, and 100% by volume) mixed with peat as subplots. Expt. 2 involved 0% stover mixed with peat, 25% distillers grain, and 50% quick compost (mechanically processed to accelerate compost process) stover with and without CaO, and 75% quick compost stover without CaO, as subplots. We measured growth parameters (height, dry weight, and flower number) and properties of the mixes. During Expt. 1, across both species, the addition of stover at rates >50% reduced relative greenness by 40%, vegetative biomass yield by 74%, and reproductive biomass yield by 73% compared to mixes with 0% and 25% stover. As the stover rate increased, available water content in the mixes decreased ( r = −0.34; P < 0.001). Mixes with 0% and 25% stover had 34% more available water than mixes with 100% stover, which probably reduced plant growth in the 100% stover treatment. As the stover rate increased, plant tissue N and P concentrations decreased. Mixes with 0% stover generally had greater N and P concentrations than mixes with stover. During Expt. 2, for marigolds, the addition of 50% quick compost stover+CaO and 75% quick compost stover-CaO reduced relative greenness by 19% and vegetative biomass by 66% compared to mixes with 25% distillers grain or 0% stover. For tomatoes, the addition of 50% quick compost stover+CaO and 75% quick compost stover-CaO reduced biomass yield by 64%, which may be due to the higher pH and electrical conductivity (EC) of both treatments. Plant tissue N and P concentrations were greater in the mix with 25% distillers grain compared to most treatments, but N and P concentrations in the other mixes varied. Overall, the 25% distillers grain (3 peat: 1 distiller grain: 4 perlite) and 25% stover (3 peat: 1 stover: 4 perlite) treatments showed the most promise as additives in a peat-based mix.

Waterbirds have a major functional role in wetlands, and understanding how functional traits of waterbirds depend on environmental characteristics can facilitate management of ecosystems and their services. We investigate how the waterbird community in a Neotropical river-floodplain system responds to environmental gradients, identifying how they affect waterbird species richness, functional diversity (measured as functional dispersion) and functional composition (specific functional traits). We sampled 22 lakes in the Upper Paraná floodplain system in southern Brazil, and modelled avian functional diversity and species richness as a function of environmental variables. Then we used a unified RLQ and fourth-corner analysis to evaluate environment-trait relationships. Waterbird species richness and functional diversity varied according to different environmental variables. Lake area and diversity of aquatic vegetation were associated with avian species richness, while relative abundance of grass and emergent macrophytes and mean and variation of depth were related to functional diversity. Furthermore, changes in functional diversity seemed to be mainly driven by presence of species that depend on perches for foraging (e.g. kingfishers, cormorants, and kites), whose presence was mainly associated with deep water and emergent macrophytes. Nevertheless, changes in functional diversity and functional composition did not depend on exactly the same set of environmental variables, suggesting that trait combinations (e.g. below surface feeders who feed on fish), not only specific traits, are important drivers of the variation in functional diversity between lakes. Given the observed differences in responses of species richness and functional diversity, both these diversity metrics should be used as complementary tools in ecosystem management. Furthermore, our results show that functional diversity and composition are partially coupled, suggesting that although functional diversity is influenced by the environmental filtering of particular traits, it also reflects other ecological mechanisms (e.g. competitive interactions among species).

AimThe so‐called regime shifts in North Sea plankton communities provide an important historical case study to understand marine regime shifts. Previous studies characterized regime shifts using a variety of community metrics (e.g., indicator species abundances, taxonomic composition and chlorophyll biomass) but left the functional traits of plankton unassessed. Here, we explicitly re‐assess the historically recognized North Sea regime shifts through the lens of plankton functional traits to gain a better understanding of these events.LocationThe North Sea (NW European shelf).Time period1958–2018, focusing on the 1980s and 1996–2003 regime shifts.Major taxa studiedMarine phyto‐ and zooplankton.MethodsWe compute trait spaces for both phyto‐ and zooplankton of the North Sea using traits from the literature and a Gower's distance‐based method. Using abundance data from the Continuous Plankton Recorder Survey, we then compute monthly time series of the centroids of the communities, an indicator of functional composition. We then use principal component analysis on the centroids to assess the main temporal changes in plankton functional composition associated with the 1980s and 1996–2003 regime shifts.ResultsLittle change in plankton functional composition was associated with the 1980s regime shift. In contrast, the functional composition of plankton communities changed markedly after the 1996–2003 regime shift, with an increase in the summer relative abundance of non‐motile autotrophs (i.e., diatoms) and the spring relative abundance of meroplankton.Main conclusionsThe North Sea regime shifts were not associated systematically with changes in functional composition, calling into question the definition of regime shifts and illustrating the importance of taking different metrics into account to interpret ecological events accurately. Taking into account functional composition, we interpret the 1980s so‐called regime shift as a latitudinal shift in communities that was insufficient to impact functional composition and the 1996–2003 so‐called regime shift as a period of change in bentho‐pelagic coupling.

Competition between plants can lead to a tragedy of the commons (TOC), where excessive investment in resource-harvesting organs reduces collective performance. Mixing crop varieties could resolve such TOCs through niche complementarity—if varieties differ in resource use—or selection effects, where competitive varieties benefit from weaker neighbours. While most studies on varietal mixtures focus on above-ground traits, below-ground interactions remain poorly understood. We grew 36 durum wheat (Triticum turgidum ssp. durum) varieties in pure stands and 54 binary mixtures using a high-throughput root phenotyping platform, under both non-limiting (R+) and limiting (R–) water and nutrient conditions, to assess early-stage root competition. In R–, mixtures produced less biomass than expected based on pure stands, largely due to a negative complementarity effect. This was mostly explained by the average projected root area of the two varieties. Rather than indicating a negative interaction, the effect reflected a relaxation of competition: varieties with larger root systems benefited from having weaker competitors, disengaging from the arms race for biomass accumulation. These findings suggest that root area is a promising breeding target for mitigating intra-specific competition and a critical trait for assembling optimal varietal mixtures.

BackgroundDisturbances are crucial in determining forest biodiversity, dynamics, and ecosystem functions. Surface fire is a significant disturbance in tropical forests, but research on the effect of surface fire on structuring species and functional composition in a community through time remains scarce. Using a 20-year dataset of tree demography in a seasonal evergreen tropical forest in Thailand, we specifically addressed two essential questions: (1) What is the pattern of temporal turnover in species and functional composition in a community with frequent fire disturbance? (2) How did the temporal turnover vary with tree size?MethodsWe analyzed species compositional and functional temporal turnovers in four different tree size classes among five tree censuses. We quantified species turnover by calculating Bray-Curtis dissimilarity, and investigated its underlying mechanisms by comparing pairwise dissimilarity of functional traits with simulations from null models. If fire disturbances contribute more to a stochastic process, the functional composition would display a random pattern. However, if they contribute more towards a deterministic process, the functional composition should reveal a non-random pattern.ResultsOver 20 years (1994–2014), we observed changes in species composition, whereas functional composition remained relatively stable. The temporal turnover patterns of species and functional compositions varied with tree sizes. In particular, temporal functional turnover shifted very little for large trees, suggesting that changes in species composition of larger trees are contributed by species with similar functional traits through time. The temporal functional composition turnovers of smaller trees (DBH ≤ 5 cm) were mostly at random. We detected a higher functional turnover than expected by null models in some quadrats throughout the 50-ha study plot, and their observed turnover varied with diameter classes.ConclusionsSpecies compositional changes were caused by changes in the abundance of species with similar functional traits through time. Temporal functional turnover in small trees was random in most quadrats, suggesting that the recruits came from the equal proportions of surviving trees and new individuals of fast-growing species, which increased rapidly after fires. On the other hand, functional composition in big trees was more likely determined by surviving trees which maintained higher functional similarities than small trees through time. Fire disturbance is important for ecosystem functions, as changing forest fire frequency may alter forest turnover, particularly in functional composition in the new recruits of this forest.

Yield and yield components of maize and soil physical properties as affected by tillage practices and organic mulching

Effect of bioslurry and chemical fertilizer on the agronomic performances of maize