Complementarity Effects Research Articles

ESL classroom interactions in a translanguaging space

Abstract There has been a recent proliferation of studies pertaining to translanguaging. This impetus is largely driven by the increasing acknowledgement of daily communications as translingual practice. In fact, the closely related construct of plurilingualism has been incorporated into the development of the companion volume of the Common European Framework of Reference for Languages (Council of Europe. 2020. Common European framework of reference for languages: Learning, teaching, assessment – Companion volume. Strasbourg: Council of Europe Publishing. Available at: www.coe.int/lang-cefr). Despite the rising awareness towards translanguaging and plurilingualism in European and Northern American contexts (cf. Vallejo, Claudia & Melinda Dooly. 2020. Plurilingualism and translanguaging: Emergent approaches and shared concerns. Introduction to the special issue. International Journal of Bilingual Education and Bilingualism 23(1). 1–16), scepticism remains, especially in classroom settings. Through detailed analyses of extracts taken from 27 h of recordings of UK university ESL classroom interactions among Taiwanese L1 Mandarin students transcribed based on Jefferson (Jefferson, Gail. 2004. Glossary of transcript symbols with an introduction. In Gene Lerner (ed.), Conversation analysis: Studies from the first generation, 14–31. Philadelphia: John Benjamins) and supplemented by Matsumoto (Matsumoto, Yumi. 2019. Material moments: Teacher and student use of materials in multilingual writing classroom interactions. The Modern Language Journal 103(1). 179–204) and Zhu et al. (Zhu, Hua, Wei Li & Agnieszka Lyons. 2017b. Polish shop(ping) as translanguaging space. Social Semiotics 27(4). 411–433), we aim to demonstrate the complementarity effect of various multimodal resources in progressing classroom instructions. Our analyses reveal that the different linguistic and non-linguistic resources deployed contribute to scaffolding and the development of a layered understanding of the concept in discussion (e.g. phrasal verbs). We argue that the translanguaging space enables students to engage in deeper learning. Students are empowered to break down the rigid power structure and actively participate in knowledge co-construction. We end our paper by calling for research that bridges current understanding of translanguaging and policy and assessment strategies development.

Online and in-store shopping interactions for non-essential experience goods

The online and in-store shopping landscape underwent transformative shifts due to the Covid-19 pandemic, potentially leading to novel hybrid shopping behaviors following the availability of Covid-19 vaccines. However, these new dynamics, especially for non-essential experience goods which were heavily impacted by lockdowns, remain relatively unexplored. Moreover, variations in such dynamics within the same product class are not well understood. This study investigates the interactions between online and in-store shopping behaviors across four categories of non-essential experience goods: clothing, shoes, watches, and jewelry (CSWJ); beauty and health products (BH); toys, kids, and baby supplies (TKB); and home, garden, and tools (HGT). Data from over 2,000 Florida residents collected in early 2021, encompassing purchase frequencies, attitudes, and socio-demographic attributes, were analyzed using separate bidirectional structural equation models. Findings indicate that the relationship between online and in-store shopping for CSWJ and TKB exhibited reciprocal complementarity effects. In contrast, BH and HGT displayed an asymmetric reciprocal relationship, with in-store shopping showing no significant influence on online shopping. Results on the mediating influence of attitudes on shopping behaviors showed that a pro-online shopping attitude and preference for alternative travel modes positively influenced online shopping frequency, while the joy of shopping and data privacy/security concerns emerged as drivers of in-store shopping across all product categories. In sum, this study underscores the presence of product-specific heterogeneity even within the experience goods class, contributing to the complex interactions between online and in-store shopping behaviors.

Complementarity between product and process innovation in small and micro-enterprises in Johannesburg, South Africa

ABSTRACT Innovation is important to firms’ productivity, competitiveness, agility, resilience and growth. The success of a firm’s innovation strategy depends in part on how it combines and absorbs different innovation activities. Using the Crépon-Duguet-Mairesse (CDM) structural model, this paper analyses complementarity between product and process innovation for the case of small and micro manufacturing firms in Johannesburg, South Africa. The empirical analysis utilises rich new firm-level survey data that, unlike most firm surveys, includes micro-sized firms as well as informal enterprises. Our results show strong evidence of complementarity between product and process innovations in their effects on firm performance. The results suggest that firm size, capital intensity, firm age, innovation expenditure and financial constraints are key variables associated with complementarity. We extend the specifications used in previous studies to take account of the contextual setting, with split samples by firm formality, ownership and size. We find evidence of complementarity in formal firms only. Our results also show stronger effects of complementarity in micro-firms and foreign-owned firms. The findings have relevance for promoting innovation and for enhancing the effects of innovation on firm performance among micro- and small enterprises (MSEs) in a developing country context.

Interactions between Online Shopping, In-Store Shopping and Weekly Travel Behavior: An Analysis Before and in the Aftermath of COVID-19 in Lisbon, Portugal

The standard framework for evaluating the impact of online shopping on travel and shopping behavior considers the possibility of complementarity, substitution, neutrality, or modification effects. Complementarity (online shopping complementing physical purchases, or vice versa) and substitution (online shopping replacing trips to physical stores and eventually the stores altogether) have generally received more attention in research, particularly the latter, since substitution may substantially impact travel and street life within cities. This paper analyzes data from a two-wave seven-day shopping and travel survey implemented in Lisbon before the COVID-19 pandemic (January–February 2020) and in its aftermath (April–May 2022) using a structural equation model and multigroup analysis. The results show that, in 2022, variables such as education or income, often used to characterize online shoppers, have lost significance as predictors, suggesting a broader engagement with online shopping. Moreover, the complementarity effect found in 2020 has given place to substitution, which also supports that the physical–online shopping balance might have tipped toward a more generalized adoption of online shopping in the aftermath of the pandemic.

Functional trait composition of carabid beetle communities predicts prey suppression through both mass ratio and niche complementarity mechanisms.

Several components of predator functional diversity have been hypothesized to influence prey suppression through either niche complementarity or mass ratio effects. Nevertheless, most studies have used a functional group approach when assessing the role of these predators in ecosystem functioning. By adopting a trait-based approach, we evaluated the relative contributions of carabid diversity components in predicting prey suppression. Our results highlight the importance of both taxonomic and functional diversity components of carabids as key drivers of prey suppression. Prey suppression was best predicted by carabid densities, with the dominance of Poecilus cupreus potentially driving the positive effect of community total abundance through the mass ratio effect. Prey suppression increased with increasing the density of large carabids. In addition, carabid eye diameter and antennal length were key functional traits for predicting prey suppression. Furthermore, prey suppression increased with increasing carabid functional richness following the niche complementarity effect. In contrast to functional richness, functional evenness and functional divergence of carabid communities were weakly correlated with prey suppression. By identifying which diversity components of carabid communities contribute the most to increase prey suppression, our results can guide efforts aiming to predict the relationship between diversity of these predators and ecosystem functioning.

A Donation-With-Purchase at a Restaurant: Perceived Authenticity in a Cause-related Marketing

Cause-related marketing has gained momentum in the business world. Socially responsible practices can be viable solutions to food waste and excessive alcohol consumption for hospitality businesses. Drawing on attribution and cognitive dissonance theory, the study examined the effect of complementary fit on perceived authenticity and purchase intention by product type and message appeal. A 2 (product type: utilitarian/hedonic) x 2 (message appeal: absence/presence) between-subjects experimental design was conducted. The findings reveal that promoting hedonic products can increase the effect of complementary fit on the perception of authenticity toward the campaign and land purchase intention with a positive impact. Particularly, this effect is contingent on message appeal. The positive effect of complementarity on purchase intention through perceived authenticity is more significant when a message is present. This study leverages attribute theory and cognitive dissonance theory to examine the effects of complementary fit between product and cause, product type, and message appeal on customers’ perceptions of authenticity and behaviors in the restaurant context. These insights not only contribute to academic knowledge but also help practitioners to navigate the dynamics of cause-related marketing to drive successful campaign outcomes.

Water-limited environments affect the association between functional diversity and forest productivity.

The link between biodiversity and ecosystem function can depend on environmental conditions. This contingency can impede our ability to predict how biodiversity-ecosystem function (BEF) relationships will respond to future environmental change, causing a clear need to explore the processes underlying shifts in BEF relationships across large spatial scales and broad environmental gradients. We compiled a dataset on five functional traits (maximum height, wood density, specific leaf area [SLA], seed size, and xylem vulnerability to embolism [P50]), covering 78%-90% of the tree species in the National Forest Inventory from Italy, to test (i) how a water limitation gradient shapes the functional composition and diversity of forests, (ii) how functional composition and diversity of trees relate to forest annual increment via mass ratio and complementarity effects, and (iii) how the relationship between functional diversity and annual increment varies between Mediterranean and temperate climate regions. Functional composition varied with water limitation; tree communities tended to have more conservative traits in sites with higher levels of water limitation. The response of functional diversity differed among traits and climatic regions but among temperate forest plots, we found a consistent increase of functional diversity with water limitation. Tree diversity was positively associated with annual increment of Italian forests through a combination of mass ratio and niche complementarity effects, but the relative importance of these effects depended on the trait and range of climate considered. Specifically, niche complementarity effects were more strongly associated with annual increment in the Mediterranean compared to temperate forests. Synthesis: Overall, our results suggest that biodiversity mediates forest annual increment under water-limited conditions by promoting beneficial interactions between species and complementarity in resource use. Our work highlights the importance of conserving functional diversity for future forest management to maintain forest annual increment under the expected increase in intensity and frequency of drought.

Crop cultivar mixtures stabilize productivity, partly via facilitation, when conditions are less benign

Context of problemCrop cultivar mixtures can increase and stabilize productivity; however, their effects on year-to-year temporal stability are positive in some cases, and neutral or negative in others. This inconsistency is not understood, in part because the mechanisms underlying the effects of diversity on stability are not clear, and in part because we do not understand the role of the abiotic environment on the functioning of crop mixtures. Objective of research questionTo test whether maize cultivar mixtures increase maize productivity and temporal yield stability compared to monocultures, in benign vs. less benign conditions, our objective was to explore the role of facilitation in the overall effect of crop diversity. MethodsWe performed two field experiments comparing mixtures of up to eight cultivars to monocultures over five years at Zhangye with irrigated conditions and with higher organic matter, total nitrogen, available phosphorus and available potassium, and over four years at Lishu with rainfed conditions without irrigation, and with lower soil fertility. Water supply at Zhangye was 18.5% higher than at Lishu and the water supply at Lishu was dependent on precipitation with greater year-to-year variation. ResultsAt the Lishu site, productivity was 18.3% lower than at the Zhangye site, and the temporal stability of aboveground biomass for cultivar mixtures was 31.5% higher than that of monocultures. This increase in temporal stability in mixtures corresponded to 6.9% greater productivity overall and 48.1% less variation in productivity than in monocultures at the Lishu site. Complementarity effects were positive and facilitation was much more important at the Lishu site. Temporal stability of aboveground biomass was also positively correlated with complementarity effects (P < 0.05) and facilitation (P < 0.01). There was no evidence of enhanced stability or facilitation at the Zhangye site. ConclusionsOur findings emphasize that cultivar mixtures enhance ecosystem functioning under less benign conditions with lower productivity, in part via facilitation, but not under more productive benign conditions. Implications or significanceOur study highlights that increasing crop cultivar diversity may better respond to more abiotically stressful and fluctuating conditions, and provides insight into why crop cultivar mixtures vary in their effects on stability.

Legacy of the Czar: Complementarity between education and work in Russia

ABSTRACT Vocational school graduates enjoy a higher employment probability than other types of graduates across industrial economies. This may result from either the signaling effects of vocational school degrees or skill complementarity between vocational schooling and work experience. Regarding wage regressions, signaling effects should make the coefficient of the interaction term between years of schooling and work experience negative, whereas complementarity between education and work experience should increase this coefficient because the cross-derivative of output with respect to schooling and work experience is positive. Thus, the negativity of the interaction term between years of schooling and work experience decreases as schooling becomes more complementary to work. We find that the negativity of the interaction term is smaller for vocational track graduates than for general track graduates in Russia. This result is arguably because the Russian vocational track emphasizes complementarity between education and work to a greater degree than its general track.

Impact of breed, body score and animal category on the pregnancy rate of bovine females under IATF management

This study evaluate the impact of the reuse of the intravaginal progesterone implant (DIP), the body condition score and the racial composition on the pregnancy rate of Nelore and Angus heifers (F1) and Nelore cows of different categories submitted to different protocols of TAI, from a database of 3,093 females submitted to the same hormonal induction protocol and from the mating season of a commercial farm in the north of Minas Gerais. The racial com- position influenced the pregnancy rate of heifers, with rates of 55.11% for Nellore heifers and 64.36% for ½ Angus, showing that the ½ Angus breed has 1.55 times more chances of successful gestation compared to the breed Nellore. There is no effect of the progesterone implant until the third use on the pregnancy rate of the heifers evaluated. The increase of one unit in the body condition score on the scale of 1 to 5 implies 1.9109 or 91.09% times more success in pregnancy. The category of calving cows did not significantly affect the pregnancy rate in the evaluated herd, with pregnancy rates of 58.1%, 62.8%, 77.7% and 62.9% for primiparous, early primiparous, secondary and multiparous, respectively. The introduction of ½ Angus heifers to explore the effects of heterosis and complementarity between breeds is a viable alternative. Cows, when well managed in the postpartum period, obtain pregnancy rates higher than that observed in the national average.

A novel proxy to examine interspecific phosphorus facilitation between plant species.

Resource complementarity can contribute to enhanced ecosystem functioning in diverse plant communities, but the role of facilitation in the enhanced complementarity is poorly understood. Here, we use leaf manganese concentration ([Mn]) as a proxy for rhizosheath carboxylate concentration to explore novel mechanisms of complementarity mediated by phosphorus (P) facilitation. In pot experiments, we showed that mixtures involving Carex korshinskyi, an efficient P-mobilizing species, exhibited greater biomass and relative complementarity effect than combinations without C. korshinskyi on P-deficient soils. Compared with monocultures, leaf [Mn] and [P] of species that are inefficient at P mobilization increased by 27% and 21% when grown with C. korshinskyi (i.e. interspecific P facilitation via carboxylates) rather than next to another inefficient P-mobilizing species. This experimental result was supported by a meta-analysis including a range of efficient P-mobilizing species. Phosphorus facilitation enhanced the relative complementarity effect in low-P environments, related to a greater change in several facilitated species of their root morphological traits relative to those in monoculture. Using leaf [Mn] as a proxy, we highlight a vital mechanism of interspecific P facilitation via belowground processes and provide evidence for the pivotal role of P facilitation mediated by the plasticity of root traits in biodiversity research.

Landscape heterogeneity increases the stability of wild ungulate populations facing climatic variability in Mediterranean ecosystems

Mediterranean environments are characterized by strong intra- and inter-annual fluctuations in plant primary production, which are likely to regulate the carrying capacity and density-dependent responses of ungulate populations. These effects may, however, vary across spatial and temporal scales. Habitat heterogeneity, particularly when associated to differentiated phenological responses, may allow wild ungulates to mitigate temporal fluctuations in plant production by using different resources along the year. In this work, we use a 15-years dataset (including remote-sensing data on vegetation distribution, phenology and production, as well as ungulate population counts) to assess how temporal variability in plant primary production and livestock abundance influence the population dynamics of two wild ungulates: native red deer, Cervus elaphus, and introduced fallow deer, Dama dama. Results show that temporal alternation in the phenological cycles of the four different vegetation types increased plant production, thus food availability for ungulates, within each year. Furthermore, complementarity in the responses of different vegetation types to variations in the amount and timing of rainfall increased the predictability of food availability across different years. This complementarity effect was further increased by the contrasting responses of ungulate populations to variation in the production of different vegetation types. Furthermore, domestic ungulates had positive effects on wild ungulate density at low to intermediate abundances, but high livestock densities decreased ungulate density and constrained the stability of the plant-ungulate system in response to the impact of climatic variation, particularly under climate change. Our findings deepen the knowledge on vegetation-ungulate interactions in Mediterranean areas, potentially contributing to develop better management strategies of ungulate populations and adapt them to ongoing climate change.

Disentangling multiple relationships of species diversity, functional diversity, diatom community biomass and environmental variables in a mountainous watershed

Biodiversity and ecosystem functioning (BEF) relationships are important research issues in the context of biodiversity loss. However, most studies only explored BEF relationships using species richness as a proxy for biodiversity without considering the effects of species evenness and importance of functional diversity on ecosystem functioning. In the present study, we explored multiple relationships among in-stream environmental variables, species diversity (species richness and species evenness), functional diversity (functional richness, functional evenness and Rao’s quadratic entropy index) and biomass of benthic diatom communities from a Chinese mountainous river network. We tested two hypotheses: (1) species richness and evenness affect community biomass independently, and (2) species diversity directly affects community biomass and also indirectly affects community biomass by influencing functional diversity. We found that benthic diatom diversity and biomass were influenced by wetted width, conductivity, and pH. Species richness and evenness had positive and negative effects on community biomass, respectively; while, the effect of richness (with a pathway coefficient of 0.39) was stronger than that of evenness (−0.28). However, we have not found an interaction pathway between species richness and species evenness in structural equation models, indicating that the two effects on community biomass were independent of each other. Both functional richness and Rao’s quadratic entropy index had positive effects on community biomass, although effects of other variables blurred the relationship between functional richness and community biomass in structural equation modeling. Besides direct effects, species diversity also indirectly affected community biomass through influencing Rao’s quadratic entropy index, with direct effects (0.27) were more than twice stronger than indirect effects (0.12). Our findings imply that the selection effect played a dominant role in the relationship between diatom diversity and biomass, indicated by the negative species evenness and biomass relationship; meanwhile, the complementarity effect was also important. The inclusion of more diversity indices to explore the biodiversity-biomass relationship would help to provide a deeper and more comprehensive understanding of this relationship and its driving mechanisms. We suggest carrying out more studies on BEF relationships in streams and rivers to support protection practices for sustaining biodiversity and their ecosystem functions in natural lotic ecosystems.

Assessing the national synergy potential of onshore and offshore renewable energy from the perspective of resources dynamic and complementarity

Intermittent renewable energy sources have been transformed from supplementary energy to dominant incremental alternative energy sources in the context of carbon neutrality target worldwide. For coastal countries, it is urgent to integrate abundant offshore energy into regional onshore renewable power sources economically and reliably considering the scarcity of land resources and negative environmental impacts. However, limited knowledge on the complex spatiotemporally synergy relationships between energy potential (onshore and offshore) is a barrier in making reasonable policies to promote collaborative development of onshore and offshore energies. This study presents a spatiotemporally explicit modelling framework for assessing the synergy potential characteristics of onshore and offshore renewable energy sources. The framework firstly estimates the technical potential of solar PV and wind energy across the country by using 40 years of hourly meteorological reanalysis data (1980–2020), and then investigates the long-term changes trend, stability, and complementarity of solar-wind energy potential spatiotemporally at both onshore and offshore sub-regions. We find that a considerable amount of solar PV and wind energy sources could be harnessed in China, and onshore potential across the country (178 PWh/yr) is approximate 20 times higher than offshore energy potential (8.9 PWh/yr). Overall, onshore solar-wind energy potentials exhibit statistically insignificant but slightly increasing trend over the past 40 years, while offshore wind potentials observe an opposite change trend for solar PV and wind energy production. Complementarity assessment showed the northeast and offshore parts of China present high complementarity effects for hourly and daily power production of solar-wind systems. Furthermore, inter-regional combination between offshore and onshore northwest regions also exhibits promising synergy effect for renewable energy power output. The results on resources dynamic and complementarity highlight the advantage of interregional resources cooperative configuration and electric power grid interconnections. The analysis performed in this paper could provide a global picture for the integration planning and collaborative development strategies formulation of on-/offshore renewable energy across the country.

Half Empty and Half Full? Biased Perceptions of Compassionate Love and Effects of Dyadic Complementarity.

The prevailing theory on relationship judgments for interaction attributes suggests individuals tend to underestimate a romantic partner's expressions of compassionate love and that such underestimation is beneficial for the relationship. Yet, limited research has incorporated dyadic perspectives to assess how biased perceptions are associated with both partners' outcomes. In two daily studies of couples, we used distinct analytical approaches (Truth and Bias Model; Dyadic Response Surface Analysis) to inform perspectives on how biased perceptions are interrelated and predict relationship satisfaction. Consistent with prior research, people demonstrated an underestimation bias. However, there were differential effects of biased perceptions for actors versus partners: Underestimation predicted lower actor satisfaction but generally higher satisfaction for partners. Furthermore, we find evidence for complementarity effects: partners' directional biases were inversely related, and couples were more satisfied when partners had opposing patterns of directional bias. Findings help integrate theoretical perspectives on the adaptive role of biased relationship perceptions.

Migration, exports and capital: what is the impact of ghettos on local firms?

ABSTRACT This paper investigates the effects of migration on the export and production techniques of agri-industrial firms in the proximity of clusters of migrants. The analysis draws on an original dataset built through interviews conducted with agri-food firms in the Foggia province (southern Italy). Over the past two decades, this area has experienced a strong influx of migrants, who have concentrated in ghettos. The results do not support a pro-trade effect, but provide evidence for both a substitution and a complementarity effect of migrants on capital endowment, depending on the type of machinery used by the firm.

Few functionally acquisitive big-sized trees restrict but soil nutrients promote soil organic carbon storage in temperate deciduous forests

Soil organic carbon (SOC) storage plays a crucial role in mitigating global climate change while maintaining forests and sustaining environmental conditions. Recent studies have shown that plant species diversity increases SOC storage in experimental grasslands and natural forests. Here, we aim to show how an integrating tree-size and trait-based ecological approach leads to mechanistic insights into SOC storage that may be overlooked in previous studies. We hypothesized that tree functional diversity effects on SOC storage would change with tree-sized-based species' functional strategies driven by soil properties in natural temperate deciduous forests. We used the forest inventory data, site-specific measured traits and soil properties from 99 temperate deciduous forest plots in northwestern Iran. We investigated the joint effects of topographic factors, soil chemical properties, and the functional attributes (multi-trait functional diversity indices and community-weighted trait mean indices) of big-sized trees (BsT; individual tree diameter ≥ 50 cm) and remaining-sized trees (RsT) on topsoil (0–30 cm) SOC storage. The multiple linear regression models showed that SOC storage increased with increasing soil available phosphorus (r = 0.36), soil exchangeable potassium (r = 0.27 to 0.31) and soil total nitrogen (r = 0.27). In contrast, SOC storage declined with increasing the community-weighted mean of specific leaf area (r = −0.38 to −0.40). The structural equation model showed that SOC storage was directly driven by the positive effect of soil nutrients (i.e. a latent variable of soil total nitrogen and available phosphorus; r = 0.42) and the negative effect of the community-weighted mean of specific leaf area (r = −0.31). The topographic factors as well as the other several functional attributes of BsT and RsT showed non-significant direct and indirect effects on SOC storage in both types of statistical modelling. Our study suggests that the mass ratio and soil fertility rather than the niche complementarity effects along with the big-sized trees effect regulates SOC storage through the acquisitive trait identity of BsT species as compared to RsT species in temperate deciduous forests. We argue that maintaining high levels of species diversity with the most efficient trait identity across tree sizes is important for biodiversity conservation and multiple forest functions such as SOC storage which should be a priority for plantation management plans or silvicultural practices in natural forests.

Soil moisture drives the shift from selection to complementarity effect in the rainfed maize/faba bean intercropping system

Soil moisture drives the shift from selection to complementarity effect in the rainfed maize/faba bean intercropping system

Robotization, employment, and income: regional asymmetries and long-run policies in the Euro area.

This work correlates the impact of robotization on employment and households' income at the regional scale with the level of investment in R&D and education policies. This kind of policy, by raising the qualitative and quantitative levels of human capital, contributes to improving the complementarity effect between humans and robots, thus mitigating the substitution effect. To this end, we compute the Adjusted Penetration of Robots (APR) (a metric used to measure the extent to which robots are being used in a particular industry or sector) at the sectoral level, combining the International Federation of Robotics database for the stock of robots, EUROSTAT Regional database, and the STructural ANalysis database on 150 NUTS-2 regions of the Euro area. We then perform a spatial stacked-panel analysis on the investment in R&D and education level. Results supports the idea that regions that invest more in R&D and have higher levels of human capital can turn the risk of robotization into an increase in both income and "quantity of work," by enhancing complementarity between robots and the labor force. On the contrary, regions investing less in R&D and having lower levels of human capital may suffer a reduction in households' disposable income.

Microalgal diversity enhances water purification efficiency in experimental microcosms

The losses of biodiversity have impaired functioning and provision of ecosystem services, and the relationship between biodiversity and ecosystem functioning has emerged as a central issue in environmental sciences. However, the majority of relevant studies are conducted in terrestrial ecosystems, and they focus predominantly on the relationship between community diversity and biomass production of terrestrial vegetation. At present, water eutrophication represents an increasingly serious problem worldwide, and the use of aquatic organisms for improving water quality represents a promising approach. However, more focus is placed on the selection of certain aquatic organisms with good performance, but neglects the effects of biodiversity in the process of water purification and the underlying mechanisms. In the present study, five microalgal species commonly found in freshwater ecosystems were used to assembly experimental microcosms with varying microalgal richness and composition. We analyzed the relationship between microalgal diversity and nitrogen removal efficiency based on mixed-effect models, and further explored the underlying mechanism of microalgal diversity in the process of water quality improvement. The results showed that with an increase in microalgal diversity, nitrogen removal efficiency of microalgal communities also increased. A further analysis of the impacts of microalgal diversity showed that the complementarity effect increased while the selection effect decreased with an increase in microalgal diversity. Meanwhile, there was a significantly positive relationship between microalgal diversity and the total abundance of microalgae. On the one hand, the present study clearly demonstrates two positive diversity-ecosystem functioning relationships. On the other hand, the present study also reveals the underlying mechanism by which microalgal diversity influences nitrogen removal efficiency, namely, high-diversity microalgal communities could use limiting nutrients such as nitrogen in a more efficient and complementary manner (e.g., stronger complementarity effect in high-diversity communities), convert them into higher aggregate community properties (e.g., higher total abundance of microalge in high-diversity communities), and thus exhibit higher purification capacity (e.g., higher nitrogen removal efficiency in high-diversity communities). Under the scenario that global ecosystems are experiencing high rates of anthropogenic nutrient inputs, the use of diverse microalgal species with proper management may help provide a promising approach for improving water quality.