Structural diversity consistently mediates species richness effects on aboveground carbon along altitudinal gradients in northern Ethiopian grazing exclosures

Grazing exclosures have been promoted as an effective and low-cost land management strategy to recover vegetation and associated functions in degraded landscapes in the tropics. While grazing exclosures can be important reservoirs of biodiversity and carbon, their potential in playing a dual role of conservation of biodiversity and mitigation of climate change effects is not yet established. To address this gap, we assessed the effect of diversity on aboveground carbon (AGC) and the relative importance of the driving biotic (functional diversity, functional composition and structural diversity) and abiotic (climate, topography and soil) mechanisms. We used a dataset from 133 inventory plots across three altitudinal zones, i.e., highland, midland and lowland, in northern Ethiopia, which allowed local- (within altitudinal zone) and broad- (across altitudinal zones) environmental scale analysis of diversity-AGC relationships. We found that species richness-AGC relationship shifted from neutral in highlands to positive in mid- and lowlands as well as across the altitudinal zones. Structural diversity was consistently the strongest mediator of the positive effects of species richness on AGC within and across altitudinal zones, whereas functional composition linked species richness to AGC at the broad environmental scale only. Abiotic factors had direct and indirect effects via biotic factors on AGC, but their relative importance varied with altitudinal zones. Our results indicate that the effect of species diversity on AGC was altitude-dependent and operated more strongly through structural diversity (representing niche complementarity effect) than functional composition (representing selection effect). Our study suggests that maintaining high structural diversity and managing functionally important species while promoting favourable climatic and soil conditions can enhance carbon storage in grazing exclosures.

Rare prokaryotic sub-communities dominate the complexity of ecological networks and soil multinutrient cycling during long-term secondary succession in China's Loess Plateau

Unraveling the succession of microbial communities is a core ecological research topic. Yet few studies have focused on how long-term secondary succession affects the functional profiles and ecological processes of abundant and rare microbial subcommunities. Here, we used amplicon sequencing and GeoChip analysis to explore the ecological functions of abundant and rare biospheres and their correlation with soil multinutrient cycling. Samples for this study were collected from a well-established secondary succession chronosequence that spans >30 years of dryland ecosystem development on the Loess Plateau of China. Although both abundant and rare subcommunities shifted with succession, the changing of beta-diversity of the microbial communities was primarily driven by species replacement of the rare biosphere. Phylogenetic changes of abundant and rare taxa were associated with their functional traits, which dominated the diversity-related selection along all succession ages. Neutral theory analysis indicated that the assemblage of abundant taxa over all successional ages was regulated by dispersal homogenizing and ecological drift. The null model revealed that homogeneous and variable selection were the dominant assembly processes for rare subcommunities compared with abundant species. pH and nitrogen content were the paramount drivers determining the assembly of microbial communities and functional genes, consistent with the importance of environmental filtering. Furthermore, the rare biosphere had a paramount role in the entire ecological network and was the major driver for most soil processes such as C, N, and S cycling. Nonetheless, a significant portion of soil P cycling was regulated by abundant taxa. Collectively, our study provides insight into the mechanisms underlying microbial community assembly and soil microbe-driven functional changes in biogeochemical processes during secondary succession.

Species and functional diversity - A better understanding of the impact of urbanization on bee communities

We examined site patterns in bee species for diversity and functional diversity in urban, suburban and rural areas. We sampled bees from all three habitat types and compiled a database of functional traits for each species. While species diversity decreased with urbanization, as expected, components of functional diversity showed differences between urban and suburban habitats. Functional dispersion (FDis) increased significantly in suburban areas as compared to urban sites, while functional divergence (FDiv) and functional redundancy (Fred) were higher in urban areas. Functional richness (FRic) and evenness (FEven) were not affected by urbanization. Moreover, assemblages in highly urbanized environments have a substantially different functional composition. Solitary species, cleptoparasites, soil nesters, bees with trophic specialization, and those with a short flight period turned out to be more sensitive to urbanization changes. This study highlights the importance of examining functional diversity in assessing human-induced biodiversity loss and its impacts on ecosystem functioning in urbanized areas. These results have significant implications for improving our understanding of the mechanisms of suburban community ecology and conserving bees in urban habitats.

Plant-plant co-occurrences under a complex land-use gradient in a temperate forest

Land-use generates multiple stress factors, and we need to understand their effects on plant-plant interactions to predict the consequences of land-use intensification. The stress-gradient hypothesis predicts that the relative strength of positive and negative interactions changes inversely under increasing environmental stress. However, the outcome of interactions also depends on stress factor's complexity, the scale of analysis, and the role of functional traits in structuring the community. We evaluated plant-plant co-occurrences in a temperate forest, aiming to identify changes in pairwise and network metrics under increasing silvopastoral use intensity. Proportionally, positive co-occurrences were more frequent under high than low use, while negative co-occurrences were more frequent under low than high. Networks of negative co-occurrences showed higher centralization under low use, while networks of positive co-occurrences showed lower modularity and higher centralization under high use. We found a partial relationship between co-occurrences and key functional traits expected to mediate facilitation and competition processes. Our results shows that the stress-gradient hypothesis predicts changes in spatial co-occurrences even when two stress factors interact in a complex way. Networks of negative co-occurrences showed a hierarchical effect of dominant species under low use intensity. But positive co-occurrence network structure partially presented the characteristics expected if the facilitation was an important mechanism characterizing the community under high disturbance intensity. The partial relationship between functional traits and co-occurrences may indicate that other factors besides biotic interactions may be structuring the observed negative spatial associations in temperate Patagonian forests.

Modelling selection, drift, dispersal and their interactions in the community assembly of Amazonian soil mites

Three processes can explain contemporary community assembly: natural selection, ecological drift and dispersal. However, quantifying their effects has been complicated by confusion between different processes and neglect of expected interactions among them. One possible solution is to simultaneously model the expected effects of each process within species, across communities and across species, thus providing more integrative tests of ecological theory. Here, we used generalized linear mixed models to assess the effects of selection, drift and dispersal on the occurrence probability of 135 soil oribatid mite species across 55 sites over an Amazonian rainforest landscape (64 km²). We tested for interactions between process-related factors and partitioned the explained variation among them. We found that occurrence probability (1) responded to soil P content and litter mass depending on body size and reproductive mode (sexual or parthenogenetic), respectively (selection); (2) increased with community size (drift); and (3) decreased with distance to the nearest source population, and more so in rare species (dispersal limitation). Processes did not interact significantly, and our best model explained 67% of the overall variation in species occurrence probability. However, most of the variation was attributable to dispersal limitation (55%). Our results challenge the seldom-tested theoretical prediction that ecological processes should interact. Rather, they suggest that dispersal limitation overrides the signatures of drift and selection at the landscape level, thus rendering soil microarthropod species ecologically equivalent and possibly contributing to the maintenance of metacommunity diversity.

The entangled multi-level responses of Mytilus galloprovincialis (Lamarck, 1819) to environmental stressors as detected by an integrated approach

Anthropogenic pressure adds up and interacts with the effects of climate change with a varying magnitude and potential changes depend on species' Life History (LH) traits, local environmental conditions and co-occurrence of several stressors. Stressors exert negative effects on marine biota when acting as a single factor, but the effects may be amplified when more than one stressor work in combination, producing interacting effects on biodiversity and ecosystem functioning. The impairment of individual functional traits (FT) leads to strong rebounds on LH traits and this may have ecological consequences. No studies actually relate FT and antioxidant enzymes to multiple environmental stressors. In this paper we investigate the effects of food concentration, temperature and hypoxia on metabolic traits as expressed by a proxy such as respiration rate and feeding behaviour and on antioxidant enzymes (Catalase, Superoxide dismutase, Glutathione S-Transferase, Glutathione peroxidase) for the bivalve Mytilus galloprovincialis. Mussels were exposed to three temperatures (12, 20 and 28 °C) under normoxic (8 mg O₂ l^-1) and hypoxic (~2 mg O₂ l^-1) conditions, with varying food concentrations ranging from 0.9 to 3.5 μg of chlorophyll l^-1. The results show that FTs and antioxidant enzymes were affected by temperature, hypoxia and food availability, and outcome allowed us to emphasise that a multi-scalar integrated approach is suitable to detect and monitor effects of anthropogenic disturbance on ecosystem functioning.

Response of macrobenthic communities to heavy metal pollution in Laoshan Bay, China: A trait-based method

The effects of multiple natural and anthropogenic stressors on the functional trait composition and diversity of marine macrobenthic communities in Laoshan Bay were investigated using biological trait analysis (BTA). Seven traits, including 27 trait modalities and four functional diversity indices (functional richness, functional evenness, functional divergence, and Rao's quadratic entropy), were considered. The results of RLQ (environmental variables (R), species taxa (L), and traits (Q)) and variance partitioning analysis (VPA) showed that the trait compositions and functional diversity of macrobenthic communities were influenced by a combination of stressors, among which heavy metals were the major factors. At the sites with high heavy metal pollution, the prevalent traits were infauna, burrower, and deposit feeder, whereas epifauna, carnivores and crawlers were dominant at the sites of low heavy metal contamination. The impact of natural environmental gradients on macrobenthic communities is also worthy of attention.

How soil ion stress and type influence the flooding adaptive strategies of Phragmites australis and Bolboschoenus planiculmis in temperate saline-alkaline wetlands?

Soil saline-alkaline stress and flooding extremes have been projected to be the main factors influencing the degradation of marsh plants in wetlands worldwide, which would affect their ecological functions (i.e. food source for migrating birds). Plants cope with flooding either by escaping from below water through shoot elongation or by remaining quiescent until water subsides. However, little is known about the adaptive strategies of Phragmites australis and Bolboschoenus planiculmis to flooding combined with salinity-alkalinity, which are the key environmental filters in Western Songnen Plain, China. Accordingly, this study investigated the adaptive strategies of P. australis and B. planiculmis subjected to the interacting effects of flooding and soil ion stress under field and greenhouse conditions. Results showed that the two species adopted different strategies to survive flooding. P. australis exhibited an escape strategy because of leaf and shoot elongation with increasing flooding depth whereas B. planiculmis became quiescent with no or deceased leaf and shoot elongation and biomass accumulation. High soil ion stress changed the flooding adaptive strategy of P. australis to a quiescence strategy, whereas B. planiculmis remained quiescent with increasing flooding depth at each soil ion content. The strategies of the two species were changed by alkaline ion stress but not by saline ion stress, and they exhibited different adaptive responses. High alkaline ion stress induced P. australis to remain quiescent with increasing flooding depth, whereas low alkaline ion stress promoted B. planicumis to escape from below water, probably due to the buffer effect of low alkaline ion contents outside the roots probably. Hence, P. australis and B. planicumis might adopt the quiescence strategy with increasing degree of soil salinization and alkalization under high greenhouse gas emissions scenarios in Western Songnen Plain, which may lead to severe degradation of the two kinds of marshes in the future.

Associations between the breeding values of Holstein-Friesian bulls and longevity and culling reasons of their daughters

Taking into account functional traits in the breeding practice should lead to a longer productive life of cows. However, despite the increased contribution of these traits in bull selection indices, their daughters are frequently culled as early as the 2nd or 3rd lactation. The problem is whether and to what extent the genetic potential of animals is realized in the production practice. Therefore, the purpose of this study was to determine the associations between the breeding value (BV) of bulls and their daughters for cow longevity and culling reasons in the Holstein-Friesian cattle population in Poland. Data for 532 062 cows culled in 2012, 2015, and 2018 were analyzed. A majority of 5 045 cow sires originated from Poland, Germany, France, the Netherlands, and the United States. The highest variation in the contribution of culling reasons was for the cows culled at the age of 2-4 years. The contribution of the culling reasons, analyzed in relation to the cow culling age, remained similar and the only exception was culling because of old age, for which a significant increase was observed only for the culling age of at least 9 years (13.8%), which was reached by only 7.3% of the cows. The sires were characterized by generally high BV for conformation and reproductive traits. However, they had, at most, the average genetic potential for functional longevity. There were a number of beneficial associations found between the BV of bulls and the distribution of culling reasons in their daughters. For example, it concerns relations between the somatic cell score in milk and culling due to udder diseases and low milk yield, between the interval from calving to first insemination and low milk yield, between the protein yield and old age, or between the BV for certain conformation traits (size, udder) and cow culling due to age. In these cases, as the BV increased for a given trait, the contribution of the corresponding cow culling reason tended to decrease. Our study showed that it seems reasonable to consider Holstein-Friesian cows aged at least 9 years at culling to be long-living animals. This is primarily evidenced by the rapid increase in the culling due to old age in relation to younger cows. Nowadays the above age limit can be suggested as a criterion of longevity for Holstein-Friesian cows but the criterion should be updated to the relation genotype-environment-economy that tends to change over time.

Duration of water flow interruption drives the structure and functional diversity of stream benthic diatoms

Flow cessation affects river ecosystems submitted to low precipitation and increased water demand, and creates unfavourable conditions to aquatic biological communities. Diatoms are amongst the most sensitive biological groups to hydric stress, making them good indicators of preceding hydrological conditions. We here analyse the response of diatom assemblages to the duration and frequency of non-flow periods in 23 Mediterranean temporary streams. All of them experienced a strong decrease in water flow during summer, leading to a period of flow cessation. In addition, other ten permanent streams (zero dry days during the study period) were included in the study for comparative purposes. Temporary and permanent streams showed similar diatom species richness, evenness, and alpha diversity. However, beta diversity was higher in temporary than permanent streams, regardless rare taxa (<1% occurrence) had similar numbers in the two types of streams. Alpha diversity, richness, and evenness of diatom assemblages in the temporary streams changed with the duration of the non-flow period. Durations of 50-100 days were associated to higher alpha diversity, richness, and evenness, but longer non-flow periods caused their decrease. Diatoms thriving under the most extreme conditions were mostly aerophilic, pioneer, and motile taxa. The proportion of aerophilic diatom taxa increased beyond 100 dry days, particularly in those sites receiving more intense solar radiation. Overall, the taxonomical and functional composition of diatom assemblages mostly responded to the duration of the non-flow period, irrespectively of these being consecutive or not. This study shows that diatom assemblages from temporary streams contain taxa adapted to non-flow conditions, but remain vulnerable to further reductions of water flow associated to climate or global change. 'Unimpacted' watercourses in the Mediterranean region, independently of their flow regime, should be urgently protected and used as taxonomical and functional early indicators of climate change.

Do presence of gray shrimp Crangon crangon larvae influence meiobenthic features? Assessment with a focus on traits of nematodes

In this study, a microcosm experiment was conducted for 30 days to assess the impact of the presence of juvenile gray shrimp Crangon crangon on meiofauna. The results suggested that juvenile shrimp had a significant negative impact on the abundance of nematodes and copepods, but no effect on polychaetes. Moreover, nematodes showed a significant decline in individual weight. The collected nematodes were taxonomically identified and assigned to five functional traits: shapes of the tail and amphid, life history, feeding types, and adult length. The nematode traits were affected by the number of shrimp introduced, and descriptors followed normal or inversed bell-shaped curves. When no shrimp were present, the nematofauna had a higher species richness compared with treatments of 4, 8, and 12 shrimp. Bell-shaped curve patterns were common in relation to the two phases of feeding for C. crangon. During the first phase, C. crangon consumed the nematode species Oncholaimus campylocercoides; thereafter, shrimp fed mostly on the nematode Anticoma eberthi and copepods.

Nematode traits after separate and simultaneous exposure to Polycyclic Aromatic Hydrocarbons (anthracene, pyrene and benzo[a]pyrene) in closed and open microcosms

The majority of experimental studies carried out to date, regarding the effects of pollutants on meiofauna have been conducted by means of closed systems, and rarely using open ones. The current work explored the impact of three Polycyclic Aromatic Hydrocarbons (PAHs), anthracene, pyrene and benzo[a]pyrene, applied alone or combined, on meiobenthic nematodes using both systems. The results revealed that single PAHs impacted the nematofauna similarly in closed or open systems with a higher toxicity observed for benzo[a]pyrene. However, the closed microcosms contaminated with PAHs became organically enriched, resulting in more non-selective deposit feeders and omnivores-carnivores. Taxonomic and functional effects related to combinations of PAHs were close to those of individual treatments in closed systems, however, for open ones, the outcomes were different. The caudal morphology influenced the response of taxa during their avoidance/endurance of hydrocarbons in open systems where the effects of PAHs mixtures appeared not only additive but also synergetic. Based on the results of the study, the use of open systems is preferred to closed ones as the research outcomes were more accurate and representing better conditions prevailing in nature.

Hydrological intermittency drives diversity decline and functional homogenization in benthic diatom communities

Over the last decades, the combined effects of global climate changes and severe land use modifications have been exacerbating river hydrological alterations and habitat fragmentation in many Mediterranean rivers. This trend is predicted to intensify, with expected significant impacts on taxonomic and functional diversity of benthic communities in the next future. By comparing perennial and intermittent reaches, the present research aims at investigating the role of flow intermittency, driven by the combined effects of climatic variables and land use changes, on benthic diatom communities in Mediterranean streams (NW Italy), by analysing data collected over 11 years. In order to avoid potential confounding effects related to water quality, sites characterized by "poor" or "bad" water quality were excluded a priori. We observed significant differences between permanent and intermittent sections in terms of both climatic variables and land use: higher temperatures and lower precipitations, coupled with an extensive anthropic land use, intensify the natural flow intermittency in intermittent sites. This led to a significant decline in diatom species diversity, at both local and regional scales, and to changes to life history traits. In particular, communities of intermittent reaches were taxonomically and functionally different and less heterogeneous than assemblages characterizing perennial ones, showing higher percentages of small, mainly stalked and pioneer taxa belonging to the low profile guild. Conversely taxa colonizing permanent reaches were bigger, belonging to the high profile guild and able to produce colonies, thus indicating high environmental stability. Our results highlighted how hydrological alterations are profoundly threatening Mediterranean streams and the diatom communities inhabiting them, therefore representing an important benchmark in view of the improvement of biological indices for the assessment of intermittent rivers.

Climate regulates the functional traits - aboveground biomass relationships at a community-level in forests: A global meta-analysis

The relationships between plant functional traits and aboveground biomass (AGB) stock have been explored across forest biomes. Yet, meta-analyses synthesizing our understanding regarding the influences of climate and soil on the functional traits - AGB relationships at a community-level in global forests are still unavailable. Here, we evaluated the latitudinal gradient in the functional traits -AGB relationships in forests, including functional trait diversity (FTD) - AGB (FTD-AGB), community-weighted mean (CWM) of conservative traits (CWMCT-AGB), CWM of acquisitive traits (CWMAT-AGB), and CWM of plant maximum height or diameter (FunDom-AGB), and then answer the question whether climate and soil conditions modulate the functional traits - AGB relationships in global forests. To do so, we selected those studies which reported the relationships of FTD and CWM with AGB stock (i.e. in Mg ha^-1) rather with AGB productivity or growth (i.e. Mg ha^-1 yr^-1) at a community-level (i.e. forest plot). By using piecewise structural equation meta-modeling, we found that: (1) functional traits - AGB relationships at a community-level were driven by mean annual temperature (MAT), aridity and soil fertility. (2) Higher MAT and low aridity promoted FTD-AGB relationships but the opposite trend was true for CWMCT-AGB, whereas higher MAT promoted CWMAT-AGB and FunDom-AGB at high aridity levels. (3) The FunDom-AGB relationship increased with increasing the number of forest plots but other relationships declined. (4) The negligible or negative FTD-AGB relationships but the positive AGB-FunDom relationships were conspicuous across global forests, indicating the mass ratio effect in terms of functional dominance. Our meta-analysis suggests that functional dominance and conservative species' strategy in relation to favorable abiotic conditions should be promoted to increase AGB stock under global environmental changes.

Tropical land-use change alters trait-based community assembly rules for dung beetles and birds

Tropical rainforest disturbance and conversion are critical drivers of biodiversity loss. A key knowledge gap is understanding the impacts of habitat modification on mechanisms of community assembly, which are predicted to respond differently between taxa and across spatial scales. We use a null model approach to detect trait assembly of species at local- and landscape-scales, and then subdivide communities with different habitat associations and foraging guilds to investigate whether the detection of assembly mechanisms varies between groups. We focus on two indicator taxa, dung beetles and birds, across a disturbance gradient of primary rainforest, selectively logged rainforest, and oil palm plantations in Borneo, Southeast Asia. Random community assembly was predominant for dung beetles across habitats, whereas trait convergence, indicative of environmental filtering, occurred across the disturbance gradient for birds. Assembly patterns at the two spatial scales were similar. Subdividing for habitat association and foraging guild revealed patterns hidden when focusing on the overall community. Dung beetle forest specialists and habitat generalists showed opposing assembly mechanisms in primary forest, community assembly of habitat generalists for both taxa differed with disturbance intensity, and insectivorous birds strongly influenced overall community assembly relative to other guilds. Our study reveals the sensitivity of community assembly mechanisms to anthropogenic disturbance via a shift in the relative contribution of stochastic and deterministic processes. This highlights the need for greater understanding of how habitat modification alters species interactions and the importance of incorporating species' traits within assessments.

Context-dependency of tree species diversity, trait composition and stand structural attributes regulate temperate forest multifunctionality

High species diversity is generally thought to be a requirement for sustaining forest multifunctionality. However, the degree to which the relationship between species-, structural-, and trait-diversity of forests and multifunctionality depend on the context (such as stand age or abiotic conditions) is not well studied. Here, we hypothesized that context-dependency of tree species diversity, functional trait composition and stand structural attributes promote temperate forest multifunctionality including above- and below-ground multiple and single functions. To do so, we used repeated forest inventory data, from temperate mixed forests of northeast China, to quantify two above-ground (i.e. coarse woody productivity and wild edible plant biomass), five below-ground (i.e. soil organic carbon, total soil nitrogen, potassium, phosphorus and sulfur) functions, tree species diversity, individual tree size variation (CV_DBH) and functional trait composition of specific leaf area (CWM_SLA) as well as stand age and abiotic conditions. We found that tree species diversity increased forest multifunctionality and most of the single functions. Below-ground single and multifunctionality were better explained by tree species diversity. In contrast, above-ground single and multifunctionality were better explained by CV_DBH. However, CWM_SLA was also an additional important driver for maintaining above- and below-ground forest multifunctionality through opposing plant functional strategies. Stand age markedly reduced forest multifunctionality, tree species diversity and CWM_SLA but substantially increased CV_DBH. Below-ground forest multifunctionality and tree species diversity decreased while above-ground forest multifunctionality increased on steep slopes. These results highlight that context-dependency of forest diversity attributes might regulate forest multifunctionality but may not have a consistent effect on above-ground and below-ground forest multifunctionality due to the fact that those functions were driven by varied functional strategies of different plant species. We argue that maximizing forest complexity could act as a viable strategy to maximizing forest multifunctionality, while also promoting biodiversity conservation to mitigate climate change effects.

Tree-ring δ18O climate signals vary among tree functional types in South Asian tropical moist forests

We present the first annually resolved and statistically reliable tree-ring δ¹⁸O (δ¹⁸O_T) chronologies for the three South Asian tropical moist forest tree species (Chukrasia tabularis A. Juss., Toona ciliata M. Roem., and Lagerstroemia speciosa Roxb.) which differ in their shade tolerance and resistance to water stress. We found significantly higher mean δ¹⁸O_T values in light-demanding T. ciliata than in intermediate shade tolerant C. tabularis and shade tolerant L. speciosa (p < 0.001). δ¹⁸O_T in C. tabularis was mainly influenced by pre-monsoon vapor pressure deficit (VPD; r = -0.54, p < 0.01) and post monsoon maximum temperature (T_max) (r = 0.52, p < 0.01). δ¹⁸O_T in T. ciliata was strongly negatively correlated with a dry season drought index PDSI (r = -0.65, p < 0.001) and VPD (r = -0.58, p < 0.001). Pre-monsoon T_max was strongly positively linked with δ¹⁸O_T in L. speciosa (r = 0.65, p < 0.001), indicating that climatic influences on δ¹⁸O_T are species-specific and vary among tree functional types. Although there was a week correlation between local precipitation and δ¹⁸O_T in our studied species, we found a strong correlation between δ¹⁸O_T and precipitation at a larger spatial scale. Linear mixed effect models revealed that multiple factors improved model performance only in C. tabularis, yielding the best model, which combined VPD and T_max. The top models in T. ciliata and L. speciosa included only the single factors PDSI and T_max, highlighting that the way C. tabularis interacts with climate is more complex when compared with other two species. Our analyses suggest that stable oxygen isotope composition in tree rings of South Asian tropical moist forest trees are a suitable proxy of local and regional climate variability and are an important tool for understanding the physiological mechanisms associated with the global hydrological cycle.

Effects of mixing two legume species at seedling stage under different environmental conditions

While intercropping is known to have positive effects on crop productivity, it is unclear whether the effects of mixing species start at the early plant stage, that is, during germination. We tested whether the germination of two legume species, alsike clover and black medic, characterized by a contrasting response to water availability and temperature is affected by mixing. We set up four experiments in each of which we compared a 1:1 mixture against the two monocultures, and combined this with various other experimental factors. These additional factors were (i) varied seed densities (50%, 100% and 150% of a reference density) in two field trials in 2016 and 2017, (ii) varied seed densities (high and low) and water availability (six levels, between 25% and 100% of water holding capacity (WHC)) in a greenhouse pot trial, (iii) varied seed spacing in a climate chamber, and (iv) varied temperatures (12 °C, 20 °C and 28 °C) and water availability (four levels between 25% and 100% of WHC) in a climate chamber. Across all experiments, the absolute mixture effects (AME) on germination ranged between −9% and +11%, with a median of +1.3%. Within experiments, significant mixture effects were observed, but the direction of these effects was inconsistent. In the field, AME on germination was significantly negative at some of the tested seed densities. A positive AME was observed in the climate chamber at 12 °C, and the mean AME decreased with increasing temperature. Higher density was associated with decreased germination in the field, indicating negative interaction through competition or allelopathy, among seedlings. Our findings indicate that interaction among seeds in species mixtures may be ongoing during germination, but that the direction of the mixture effect is affected by complex interactions with abiotic and biotic factors.

Effects of fertilization and irrigation on vascular plant species richness, functional composition and yield in mountain grasslands

Land-use intensification is a major threat to biodiversity in agricultural grasslands and fertilization is one of the main drivers. The effects of fertilization on biodiversity and plant functional composition (community-weighted mean traits and mean ecological indicator values) are well studied in lowland regions, but have received less attention in mountain grasslands. Moreover, in inner-alpine dry valleys, fertilizer is often applied in combination with irrigation, and irrigation effects are less well known. We experimentally tested the effects of fertilization and irrigation on vascular plant species richness and the functional composition of mountain grasslands in the Swiss Alps. After five years, fertilization increased yield but the relationship was quadratic with maximum yield reached at intermediate fertilizer levels (58 kg N ha^-1year^-1). The species richness of all vascular plants and forbs decreased, on average, by 6 and 5 species respectively, per 50 kg N of extra fertilizer (ha^-1 year^-1) applied. Fertilization also favored fast-growing plants (increased mean specific leaf area) and plants typically found in productive environments (increased mean indicator values for soil productivity and moisture). In contrast, we found no effects of irrigation on plant community composition, which suggests that irrigation does not affect vascular plant diversity to the same extent as fertilization in these mesic mountain hay meadows, at least in the mid-term. Our finding that maximum yield can be achieved at intermediate fertilizer levels is very important from an applied, agronomical and conservation point of view. It suggests that without loss of yield, farming costs and at the same time environmental pollution and negative effects on biodiversity can be reduced by applying less fertilizer. We therefore recommend maintaining non-intensive land use and keeping fertilizer inputs as low as possible to maintain the high plant diversity of mountain grasslands.

Timber and non-timber forest products in the northernmost Neotropical rainforest: Ecological factors unravel their landscape distribution

The benefits provided by tropical rainforests are unevenly distributed throughout the landscape and are shaped by abiotic and biotic components that influence the spatial distribution and functional traits of the species involved. We tested whether environmental stratification of the rainforest in biophysical Landscape Units (LU), defined by topography and soil, is related to the spatial distribution of diversity, abundance and productivity (standing biomass) of tree assemblages that provide potential forest products (PFP). Considering that different PFP are associated with specific plant traits, we also tested whether a phylogenetic signal exists among the species that comprise specific use categories. Non-metric multidimensional scaling ordinations and permutational analysis of variance were based on the frequency, abundance and productivity of 129 species, the PFP of which were classified as fodder, food, fuelwood, medicinal, melliferous, ornamental, plywood and timber in 15 plots of 0.5 ha each. We constructed a phylogenetic tree of the studied species and analyzed the phylogenetic signal strength (D-statistic) among them. The spatial distribution of diversity and abundance of useful species changes among the LU. Specific PFP can be provided in contrasting habitat conditions, but generally not by the same species. The PFP categories that presented a phylogenetic signal were associated with wood characteristics (fuelwood and plywood) and the palatability of the leaves and reproductive structures (fodder). The Moraceae family was significantly related to fodder and plywood, whereas Meliaceae, Myrtaceae and Sapotaceae were mostly used for fuelwood. The medicinal species presented convergent traits distributed throughout the phylogeny. However, since our study included a broad variety of plant structures, it is possible that phylogenetic dispersion can change if we consider the specific uses within each category. Our findings show that the assemblages of PFP suppliers can be clustered through biophysical units based on soil and topography, and specific categories of PFP are often supplied by phylogenetically related species. This knowledge is fundamental in order to incorporate the high diversity of tree species and their potential uses into productive reforestation and agroforestry programs.

A research framework for projecting ecosystem change in highly diverse tropical mountain ecosystems

Tropical mountain ecosystems are threatened by climate and land-use changes. Their diversity and complexity make projections how they respond to environmental changes challenging. A suitable way are trait-based approaches, by distinguishing between response traits that determine the resistance of species to environmental changes and effect traits that are relevant for species' interactions, biotic processes, and ecosystem functions. The combination of those approaches with land surface models (LSM) linking the functional community composition to ecosystem functions provides new ways to project the response of ecosystems to environmental changes. With the interdisciplinary project RESPECT, we propose a research framework that uses a trait-based response-effect-framework (REF) to quantify relationships between abiotic conditions, the diversity of functional traits in communities, and associated biotic processes, informing a biodiversity-LSM. We apply the framework to a megadiverse tropical mountain forest. We use a plot design along an elevation and a land-use gradient to collect data on abiotic drivers, functional traits, and biotic processes. We integrate these data to build the biodiversity-LSM and illustrate how to test the model. REF results show that aboveground biomass production is not directly related to changing climatic conditions, but indirectly through associated changes in functional traits. Herbivory is directly related to changing abiotic conditions. The biodiversity-LSM informed by local functional trait and soil data improved the simulation of biomass production substantially. We conclude that local data, also derived from previous projects (platform Ecuador), are key elements of the research framework. We specify essential datasets to apply this framework to other mountain ecosystems.

Molecular phylogeny and trait evolution in an ancient terrestrial arthropod lineage: Systematic revision and implications for ecological divergence (Collembola, Tomocerinae)

Phylogenetic assessments of functional traits are important for mechanistically understanding the interactions between organisms and environments, but such practices are strongly limited by the availability of phylogenetic frameworks. The tomocerin springtails are an ancient, widespread and ecologically important group of terrestrial arthropods, whereas their phylogeny and trait evolution remained unaddressed. In the present study, we conducted the first comprehensive phylogenetic reconstruction of Tomocerinae, based on a multi-loci molecular dataset covering all major lineages within the subfamily, using Bayesian inference (BI), maximum-likelihood (ML) and maximum-parsimony (MP) approaches. Divergence time was estimated and ancestral character state reconstruction (ACSR) was performed to trace the evolutionary history of five ecomorphological traits correlated with sensory and locomotory functions. Our results support the monophyly of Tomocerinae, and indicate that current classification of Tomocerinae only partially reflects evolutionary relationships, notably the commonest and speciose genus Tomocerus is polyphyletic. The subfamily probably originated in Early Cretaceous and diversified in two Cretaceous and one Eocene radiation events. As indicated by the evolutionary patterns of functional traits, multiple ecological divergences took place during the diversification of Tomocerinae. The study suggests a potential underestimation of ecological divergence and functional diversity in terrestrial arthropods, calls for an update of present trait databases, and demonstrates the value of macroevolutionary knowledge for improving the trait-based ecology. In addition, Tomocerus, Tomocerina and Tritomurus are redefined, a new genus Yoshiicerusgen. n. and new subgenera Coloratomurussubgen. n., Ciliatomurussubgen. n., Striatomurussubgen. n. and Ocreatomurussubgen. n. are described in the appendix.

Streamflow regulation effects in the Mediterranean rivers: How far and to what extent are aquatic and riparian communities affected?

Dam-induced disruption of the natural continuum of rivers has manifold consequences on fluvial ecosystems, but how distinct plant groups and plant adaptive strategies can mediate the regulation effects is largely unexplored. In this work, we focused on how different plant groups (macrophytes, bryophytes, and riparian woody vegetation) respond to hydrological alterations along the river and across the riparian zone downstream of dams. We specifically aimed to determine the degree of regulation [DOR] and distance from dam [DFD], where river regulation no longer significantly affects plant communities in two case studies - a run-of-river dam and a reservoir in Portugal. We collected data on plant species cover in 7 unregulated and 24 regulated sites in June-July 2019. We performed a cluster and ordination analysis to derive guilds using flow-responsive traits and applied linear models to predict guild alterations along the gradient of DOR and DFD. We established three macrophytes, six bryophytes, and five riparian guilds. Our results showed that the vegetation response to regulation was plant group-reliant and guild-specific. Overall, plant responses were expressed by changes in plant cover, and not by guilds' loss. We observed (1) an increase of the guild cover of macrophytes and a decrease in bryophytes cover with increasing regulation gradient and diverse responses for riparian guilds; (2) an encroachment of riparian vegetation guilds into the channel downstream of the storage reservoir and expansion outwards downstream of the run-of-river dam; (3) a higher number of significant alterations for reservoir sites compared with run-of-river sites. Finally, for particular guilds, we determined specific DOR and DFD from which guild covers became significantly indistinct from respective guild cover in unregulated circumstances. Understanding the communities' responses to diverse regulation types and the extent that different plant adaptations may counter regulation effects can be vital for optimizing river restoration projects.

Diversity and functional groups of copepods as a tool for interpreting trophic relationships and ecosystem functioning in estuaries

We examined trophic relationships in estuarine planktonic food webs by focusing on the assemblages and functional groups of copepods and their effects on prey and predator. We also studied the relationship between biodiversity and ecosystem functioning in estuaries using different taxonomic and functional diversity indices of copepod assemblages and copepod biomass as a proxy of ecosystem functioning. We collected samples every 2 months over a 2-year period in four Brazilian estuaries. Taxonomic diversity indices showed a positive and negative relationship with chaetognath densities and ecosystem functioning, respectively. The functional indices were negatively related to the effect of predator diversity on prey. Different functional groups of copepods were positively correlated with chaetognath density, consistent with their generalist feeding habits. Thus, multifaceted approaches that use different indices and functional groups are recommended to provide a more realistic view of the trophic relationships and ecosystem functioning in estuaries.