Effects Of Plant Species Diversity Research Articles

Effects of plant species diversity and density of Acorus calamus and Reineckea carnea on nitrogen removal and plant growth in constructed wetlands during the cold season

Effects of plant species diversity and density of Acorus calamus and Reineckea carnea on nitrogen removal and plant growth in constructed wetlands during the cold season

Positive effects of plant species diversity on organic carbon accumulation in soil aggregates driven by mineral protection in a subtropical forest in southwest China

Positive effects of plant species diversity on organic carbon accumulation in soil aggregates driven by mineral protection in a subtropical forest in southwest China

Shrub expansion raises both aboveground and underground multifunctionality on a subtropical plateau grassland: coupling multitrophic community assembly to multifunctionality and functional trade-off.

Shrubs have expanded into grasslands globally. However, the relative importance of aboveground and underground diversity and the relative importance of underground community assembly and diversity in shaping multifunctionality and functional trade-offs over shrub expansion remains unknown. In this study, aboveground and underground multitrophic communities (abundant and rare archaea, bacteria, fungi, nematodes, and protists) and 208 aboveground and underground ecosystem properties or indicators were measured at three stages (Grass, Mosaic, Shrub) of shrub expansion on the Guizhou subtropical plateau grassland to study multifunctionality and functional trade-offs. The results showed that shrub expansion significantly enhanced aboveground, underground, and entire ecosystem multifunctionality. The functional trade-off intensities of the aboveground, underground, and entire ecosystems showed significant V-shaped changes with shrub expansion. Shrub expansion improved plant species richness and changed the assembly process and species richness of soil abundant and rare subcommunities. Plant species diversity had a greater impact on multifunctionality than soil microbial diversity by more than 16%. The effect of plant species diversity on functional trade-offs was only one-fifth of the effect of soil microbial diversity. The soil microbial species richness did not affect multifunctionality, however, the assembly process of soil microbial communities did. Rather than the assembly process of soil microbial communities, the soil microbial species richness affected functional trade-offs. Our study is the first to couple multitrophic community assemblies to multifunctionality and functional trade-offs. Our results would boost the understanding of the role of aboveground and underground diversity in multifunctionality and functional trade-offs.

Adding Corbicula fluminea altered the effect of plant species diversity on greenhouse gas emissions and nitrogen removal from constructed wetlands in the low-temperature season

Plant species diversity is crucial in greenhouse gas emissions and nitrogen removal from constructed wetlands (CWs). However, previous studies have overlooked the impact of benthos on cumulative greenhouse gas emissions during the low-temperature season in CWs. In this study, we established 66 vertical flow CWs with three levels of species richness (1, 2, and 4 species) and eleven species compositions. The Corbicula fluminea was added or not added at each diversity level and monitored greenhouse gas emissions and effluent nitrogen concentration. Our findings indicated that (1) in microcosms without C. fluminea, high species richness significantly increased effluent nitrogen concentrations (NO3−-N, NH4+-N, and TIN), but plant species richness did not affect cumulative CH4, N2O, and CO2 emissions. The presence of Hemerocallis fulva significantly increased cumulative CO2 emissions, while the presence of Iris tectorum significantly increased effluent nitrogen (NO3−-N and TIN) concentrations and cumulative N2O emissions; (2) in microcosms with C. fluminea, the lowest cumulative CH4 emissions occurred when there were two species, but plant species richness did not affect cumulative CO2 and N2O emissions. The presence of H. fulva significantly increased cumulative CH4 emissions, while the presence of Reineckea carnea significantly increased effluent nitrogen (NO3−-N, NH4+- N, TIN) concentrations; (3) at the same diversity level, the addition of C. fluminea significantly increased cumulative CH4 and N2O emissions, as well as effluent nitrogen concentrations. These results demonstrate that C. fluminea alters the effect of plant species diversity on cumulative greenhouse gas emissions and nitrogen removal from CWs during the low-temperature season. We recommend using a two-species mixture to reduce greenhouse gas emissions. However, we caution against using plant compositions with H. fulva or I. tectorum for effective wastewater treatment and greenhouse gas reduction in CWs.

Increasing plant species diversity enhances microbial necromass carbon content but does not alter its contribution to soil organic carbon pool in a subtropical forest

Increasing plant species diversity benefits soil organic carbon (SOC) accumulation in forest ecosystems, but how microbial necromass contributes to SOC accumulation in response to plant species diversity and the underlying mechanisms have not been well explored. In the present study, 45 plots covering a natural gradient of plant species diversity as indexed by Shannon's diversity index from 0.15 to 3.57 were selected in a typical subtropical forest with calcareous soil. Soil microbial necromass C including fungal necromass C and bacterial necromass C was estimated using amino sugars, with multiple soil biotic and abiotic variables being determined to explore the mechanisms underlying the effects of plant species diversity on microbial necromass C. Total microbial necromass C contents ranged from 4.28 to 85.7 g kg−1 soil with an average of 36.3 ± 17.6 g kg−1 soil, and accounted for 54.2% ± 22.2% of the SOC pool across the 45 plots. Fungal necromass C had a greater contribution to SOC than bacterial necromass C. Increasing plant species diversity was significantly and positively correlated with microbial necromass C content, but was not significantly related to the contribution of microbial necromass C to the SOC pool. Though increasing plant species diversity enhanced microbial biomass via stimulating C use efficiency and substrate availability, microbial biomass was not significantly linked to microbial necromass C accumulation. Instead, increasing plant species diversity benefited microbial necromass C accumulation via enhancing the mineral protection due to its positive effect on soil exchangeable calcium. Due to the proportionate increase of microbial necromass C and SOC, and the unaltered soil C:N ratio and C:N imbalance between soil organic matter and microbial biomass, the contribution of microbial necromass C to the SOC pool was not affected by plant species diversity. Our study highlights the key role of mineral protection in soil microbial necromass C accumulation, and provides a microbe-dependent linkage between plant species diversity and SOC accumulation.

Drivers of soil organic carbon stock during tropical forest succession

Abstract Soil organic matter contributes to productivity in terrestrial ecosystems and contains more carbon than is found in the atmosphere. Yet, there is little understanding of soil organic carbon (SOC) sequestration processes during tropical forest succession, particularly after land abandonment from agriculture practices. Here, we used vegetation and environmental data from two large‐scale surveys covering a total landscape area of 20,000 ha in Southeast Asia to investigate the effects of plant species diversity, functional trait diversity, phylogenetic diversity, above‐ground biomass and environmental factors on SOC sequestration during forest succession. We found that functional trait diversity plays an important role in determining SOC sequestration across successional trajectories. Increases in SOC carbon storage were associated with indirect positive effects of species diversity and succession age via functional trait diversity, but phylogenetic diversity and above‐ground biomass showed no significant relationship with SOC stock. Furthermore, the effects of soil properties and functional trait diversity on SOC carbon storage shift across elevation. Synthesis. Our results suggest that reforestation and restoration management practices that implement a trait‐based approach by combining long‐lived and short‐lived species (conservative and acquisitive traits) to increase plant functional diversity could enhance SOC sequestration for climate change mitigation and adaptation efforts, as well as accelerate recovery of healthy soils.

Effects of plant species diversity, dominant species importance, and soil properties on glomalin-related soil protein

Effects of plant species diversity, dominant species importance, and soil properties on glomalin-related soil protein

Plant diversity with species drilled in the same or alternate rows enhanced pasture yield and quality over 4 years

This paper reports on the effects of plant species diversity and sowing method on pasture yield and quality. Nineteen seed mixtures of perennial ryegrass (PR), plantain (Pl), white clover (WC) and red clover (RC) were sown on 26 March 2015 at Lincoln University. Four mixtures of PR, Pl and WC were repeated with species separated in alternate drill rows. Plots were grazed by sheep and irrigated. After 4 years, a mixture with 25% of each species based on seed count – equivalent to 7.5 kg PR, 5.6 kg Pl, 1.9 kg WC and 4.4 kg RC (19.4 kg total seed)/ha – produced an optimal balance of increased total yield (17.44 t DM/ha/yr), weed suppression (0% of total yield), metabolisable energy (11.4 MJ/kg DM) and crude protein (19% of DM). Sowing method had no effect. Plant diversity enhanced pasture production through positive interactions and identity effects among the legumes (WC and RC) and non-legumes (PR and Pl). The strength of interactions between species depended on the identity and relative abundances of the species involved. The diversity effects occurred alongside shifts in species relative abundances over time. This study demonstrated an experimental basis for the evaluation of multi-species pasture mixtures.

Soil microbes drive the effect of plant species and genotypic diversity interaction on productivity.

PurposeThe effect of plant species and genotypic diversity on productivity has been well documented but little is known about the contribution of the interaction between species and genotypic diversity. Since the influence of soil microorganisms on the plant diversity-productivity relationship is increasingly recognized, we investigated potential interactions between plant species diversity, plant genotypic diversity and soil microbes. We hypothesized that the non-additive effects of plant species and genotypic diversity on productivity could be microbe-driven.MethodsWe set up pea and wheat monocultures and mixtures in a growth chamber, varying for their levels of genotypic diversity under three different soil microbial contexts. We assessed plant shoot and root biomass production, soil mineral nitrogen content and described the soil bacterial communities.ResultsWe found that shoot biomass in mixtures involving both species and genotypic diversity was higher than expected considering the additive effects of plant species diversity and genotypic diversity. Rather than a synergy between two positive effects of species and genotypic diversity, we observed that species mixture compensated the negative effect of genotypic diversity. Regarding microbial influence, we found that the effect of plant species diversity, plant genotypic diversity and their interaction on productivity were all driven by the soil microbial community as no effect was observed in a pre-sterilised soil.ConclusionOur study suggests that the plant diversity-productivity relationship could be shaped by a three-way interaction between plant species diversity, plant genotypic diversity and soil microbes. Thus, plant-microbe and plant-plant interactions could be a determinant of the plant diversity-productivity relationship.

Effects of plant species diversity on nematode community composition and diversity in a long-term biodiversity experiment

Diversity loss has been shown to change the soil community; however, little is known about long-term consequences and underlying mechanisms. Here, we investigated how nematode communities are affected by plant species richness and whether this is driven by resource quantity or quality in 15-year-old plant communities of a long-term grassland biodiversity experiment. We extracted nematodes from 93 experimental plots differing in plant species richness, and measured above- and belowground plant biomass production and soil organic carbon concentrations (Corg) as proxies for resource quantity, as well as C/Nleaf ratio and specific root length (SRL) as proxies for resource quality. We found that nematode community composition and diversity significantly differed among plant species richness levels. This was mostly due to positive plant diversity effects on the abundance and genus richness of bacterial-feeding, omnivorous, and predatory nematodes, which benefited from higher shoot mass and soil Corg in species-rich plant communities, suggesting control via resource quantity. In contrast, plant-feeding nematodes were negatively influenced by shoot mass, probably due to higher top–down control by predators, and were positively related to SRL and C/Nleaf, indicating control via resource quality. The decrease of the grazing pressure ratio (plant feeders per root mass) with plant species richness indicated a higher accumulation of plant-feeding nematodes in species-poor plant communities. Our results, therefore, support the hypothesis that soil-borne pathogens accumulate in low-diversity communities over time, while soil mutualists (bacterial-feeding, omnivorous, predatory nematodes) increase in abundance and richness in high-diversity plant communities, which may contribute to the widely-observed positive plant diversity–productivity relationship.

Interpreting the effects of plant species diversity and genotypic diversity within a dominant species on above- and belowground overyielding

Biodiversity loss, either intraspecific or interspecific level, could alter community processes and ecosystem functioning. Exploring the mechanisms by which biodiversity at different levels influences ecosystem functioning is a major challenge in the field of ecology. In this study, by constructing plant communities with different diversity levels of both dominant species (Stipa grandis) genotype and common species in a mesocosm experiment, we analyzed the relative importance of dominant genotype diversity and common species diversity on biomass production through Fox's tripartite partition, and the relationships between community functional diversity and biomass production. For common species mixtures (G0S5), a significant positive net diversity effect on belowground biomass was found, and the net effect was contributed by a significant positive dominance effect and a significant negative trait-independent complementarity effect. For genotype mixtures of S. grandis (G5S0), a significant positive net diversity effect on aboveground biomass and a non-significant positive net diversity effect on belowground biomass were found, and both the effects were driven by positive trait-independent complementarity effects. The increases in both dominant genotype and common species diversity (G5S5) led to remarkable positive net diversity effects, with a significant positive trait-independent complementarity effect on belowground biomass and all the three biodiversity effect components on aboveground biomass being significantly positive. Only a small proportion (3/22) of relationships between community functional diversity and biomass were linear by a first order polynomial estimation. The significant positive trait-independent complementarity effect in G5S0 and trait-dependent complementarity effect in G5S5 could not be explained by the smaller intraspecific trait variation. These findings highlight the underestimated and overlooked roles of dominant genotypic diversity for ecosystem functioning, and are very important for grassland protection and management, especially in the semi-arid typical steppe.

Effects of Plant Diversity and Plant Density on Ecosystem Functions in Floating Constructed Wetlands

Plant species diversity could enhance plant productivity and pollutant removal efficiency in constructed wetlands (CWs). However, the potential importance of plant density for ecosystem functioning has largely been neglected. In this study, we conducted a factorial experiment in which three common plant species were planted in a gradient of species richness (one, two, and three) and seven species compositions at two densities (six and twelve individuals per microcosm). Plant total biomass and total organic carbon (TOC) and total inorganic nitrogen (TIN) removal efficiency were measured to explore the effect of plant species diversity and density on the ecosystem functioning of CWs. Results showed that (1) plant species richness had no significant effect on plant total biomass and TOC and TIN removal efficiency under high and low plant density. (2) There were significant differences in TIN removal efficiency among seven species compositions under low plant density; especially, the presence of Canna indica reduced the TIN removal efficiency. In contrast, species composition and species identity had no significant effect on ecosystem functioning under high plant density. (3) High plant density increased plant total biomass of C. indica monocultures, and also enhanced TIN removal efficiency in mixtures of two species. These results indicated C. indica alone may not be an ideal species for enhancing pollutant removal in constructed wetlands but planting at high density could mitigate its negative effect on ecosystem functioning.

Global synthesis of effects of plant species diversity on trophic groups and interactions.

Numerous studies have demonstrated that plant species diversity enhances ecosystem functioning in terrestrial ecosystems, including diversity effects on insects (herbivores, predators and parasitoids) and plants. However, the effects of increased plant diversity across trophic levels in different ecosystems and biomes have not yet been explored on a global scale. Through a global meta-analysis of 2,914 observations from 351 studies, we found that increased plant species richness reduced herbivore abundance and damage but increased predator and parasitoid abundance, predation, parasitism and overall plant performance. Moreover, increased predator/parasitoid performance was correlated with reduced herbivore abundance and enhanced plant performance. We conclude that increasing plant species diversity promotes beneficial trophic interactions between insects and plants, ultimately contributing to increased ecosystem services.

Impact of willow-based grassland alley cropping in relation to its plant species diversity on soil ecology of former arable land

Effects of silvo-arable alley cropping systems (ACS) on soil functions have frequently been investigated, however, less is known about the effects of silvo-grassland ACS. Conversion of arable land to grassland ACS may have a high capability to rebuild soil fertility, while increased grassland plant diversity may further foster improvements. The objective of the study was to assess the impact of willows (Salix spp.) and grassland plant species diversity on soil ecology of an ACS established on former arable land. Thus, soil quality indices, like soil organic carbon (SOC), microbial biomass C and N, fungal abundance and microbial functional diversity, were quantified in formerly ploughed Eutric (Stagnic) Cambisols in two soil depths (0–5, 5–20 cm) of a temperate grassland ACS (Lower Saxony, Germany). To evaluate potential tree effects on alleyways, distance transects were analysed by repeated measures mixed effects models, considering abiotic factor (pH, clay content) variability. Possible changes of soil quality indices within the former ploughed soil layer were deduced by a comparison of both soil depths at each distance. Linear contrasts were calculated for comparisons of grassland diversity levels. Results showed significantly higher SOC contents (16.2–16.9 mg g−1) and soil microbial properties (e.g. MBC: 453-462 μg g−1, ergosterol: 4.3-4.4 μg g−1) in upper topsoils under trees and grassland compared with lower topsoil layers (11.6–12.0 mg g−1, 262-277 μg g−1 and 1.7-1.8 μg g−1 for SOC, MBC and ergosterol, respectively). No effects of plant species diversity on microbial properties have been detected to date. Similar levels of soil quality indices in upper topsoils under trees and grassland are ascribed to the cessation of tillage and a permanent vegetation cover ongoing for 5 years, as aboveground tree litter inputs into the alleyways were minor. Hence, irrespective of the diversity level of grassland vegetation, grassland ACS may have a high potential to increase soil quality for matching the requirement of sustainability of agroecosystems. However, as solely topsoils have been investigated, henceforth, the consideration of subsoils is vital to assess the effect of deep tree roots in grassland ACS.

Temporal stability of aboveground biomass is governed by species asynchrony in temperate forests.

Understanding the effects of plant species diversity and trait composition on aboveground biomass is a central focus of ecology and has important implications for biodiversity conservation. However, the simultaneous direct and indirect effects of soil nutrients, species asynchrony, functional trait diversity, and trait composition for explaining the community temporal stability of aboveground biomass remain underrepresented in natural forests. Here, we hypothesized that species asynchrony relative to soil nutrients, functional trait diversity, and trait composition plays a central role in stabilizing the community temporal stability of natural forests. We tested this hypothesis using a structural equation model based on 10-year continuous monitoring data (i.e., three-time repeated forest inventories) in both second-growth and old-growth temperate forests in northeast China. Our results showed that the community temporal stability of aboveground biomass was driven by a strong direct positive effect of species asynchrony in both second-growth and old-growth temperate forests, whereas functional trait diversity and composition (i.e. community-weighted mean of leaf nitrogen content) were of additional importance in an old-growth forest only. Functional trait diversity decreased community-weighted mean of leaf nitrogen content in an old-growth forest, whereas this relationship was non-significant in a second-growth forest. Soil nutrients had non-significant effects on the community temporal stability of both second-growth and old-growth forests. Species asynchrony was the direct determinant of the community temporal stability of aboveground biomass in temperate forests. The direct effect of species asynchrony increased with forest succession, implying that temporal niche differentiation and facilitation increase over time. This study suggests that managing forests with mixtures of both early and late successional species or shade intolerant and tolerant species, not only species diversity, is important for maintaining forest stability in a changing environment. We argue that the species asynchrony effect is crucial to understand the underlying ecological mechanisms for a diversity-biomass relationship in natural forests.

Effects of plant diversity on greenhouse gas emissions in microcosms simulating vertical constructed wetlands with high ammonium loading

Wastewater with relatively high nitrogen concentrations is a major source of nitrous oxide (N2O) and methane (CH4) emissions and exerts multiple stresses on the environment. Studies have shown that plant diversity plays an important role in ecosystem functioning. However, the effects of plant species diversity on CH4 and N2O emissions under high ammonium (NH4+-N) loading rates remain unclear. In this study, a microcosm experiment simulating vertical constructed wetlands supplied with high NH4+-N water levels was established. The treatments included four species richness levels (1, 2, 3, 4) and 15 species compositions. There was no significant relationship between species richness and N2O emissions. However, N2O emissions were significantly reduced by specific plant species composition. Notably, the communities with the presence of Rumex japonicus L. reduced N2O emissions by 62% compared to communities without this species. This reduction in N2O emissions may have been a result of decreased N concentrations and increased plant biomass. CH4 emissions did not respond to plant species richness or species identity. Overall, plant species identity surpassed species richness in lowering N2O emissions from constructed wetlands with high NH4+-N water. The results also suggest that communities with R. japonicus could achieve higher N removal and lower greenhouse gas emissions than other wetland species.

Unravelling the effects of plant species diversity and aboveground litter input on soil bacterial communities

In order to differentiate the effects of root functioning and aboveground litter inputs on soil bacterial communities, a pot experiment was designed using different combinations of three plant species with contrasting chemical characteristics (0, 1, 2 or 3 species per plot) grown with or without aboveground litter inputs from the same plant species (no litter, litter from 1 of the species, or litter from the 3 species). Bacterial community structure (ITS diversity-ARISA), as well as total bacteria and denitrifier abundances (qPCR targeting the 16S rDNA and nirK or nirS genes) and denitrifying enzyme activity (DEA) were determined. No clear effects of the plant and litter identities were revealed over the incubation time. Moreover, differences in litter C:N values did not influence the bacteria or denitrifier abundances nor DEA. Interestingly, litter diversity modified the bacterial community structure, while plant richness altered the total bacteria and denitrifier abundances as well as DEA. Soil moisture appeared to be the major driver of plant and litter richness effects in our experiment.

Plant species diversity reduces N2O but not CH4 emissions from constructed wetlands under high nitrogen levels.

Constructed wetlands (CWs) have been widely used for treating wastewater. CWs also are the sources of greenhouse gas (GHG) due to high pollutant load. It has been reported that plant species diversity can enhance nitrogen (N) removal efficiency in CWs for treating wastewater. However, the influence of plant species diversity on GHG emissions from CWs in habitats with high N levels still lack research. This study established four species richness levels (1, 2, 3, 4) and 15 species compositions by using 75 simulated vertical flow CWs microcosms to investigate the effects of plant species diversity on the GHG emissions and N removal efficiency of CWs with a high N level. Results showed plant species richness reduced nitrous oxide (N2O) emission and N (NO3--N, NH4+-N, and TIN) concentrations in wastewater, but had no effect on methane (CH4) emission. Especially, among the 15 compositions of plant species, the four-species mixture emitted the lowest N2O and had under-depletion of N (DminTIN<0). The presence of Oenanthe javanica had a significantly negative effect on the N2O emission but had no effect on N removal efficiency. The presence of Rumex japonicus significantly reduced the N (NO3--N and TIN) concentrations in wastewater but had no effect on the N2O and CH4 emissions. The N concentrations and GHG emissions in the community of R. japonicus × Phalaris arundinacea were as low as those in the four-species mixture. Assembling plant communities with relatively high species richness (four-species mixture) or particular composition (R. japonicus × P. arundinacea) could enhance the N removal efficiency and reduce the GHG emissions from CWs for treating wastewater with a high N level.

Effects of species diversity on fine root productivity in diverse ecosystems: a global meta‐analysis

AbstractAimPositive relationships between plant species diversity and above‐ground productivity have been observed across a wide range of terrestrial ecosystems. Despite a critical contribution of below‐ground productivity to overall terrestrial productivity, no consensus exists about the nature of the relationship between species diversity and below‐ground productivity.LocationGlobal.MethodsWe collected data from published studies conducted in natural and planted forests and experimental grassland, crop and pot systems that were purposely implemented to isolate the effects of plant species diversity from other factors, such as soil conditions and topographic features. We conducted meta‐analyses of 170 observations for root biomass and 23 observations for root production, derived from 48 published studies, using weighted linear modelling with bootstrap procedures to reconcile the effects of diversity on fine root productivity.ResultsWe found that species mixtures had, on average 28.4% higher fine root biomass and 44.8% higher annual production than monocultures. Higher fine root biomass in species mixtures than in monocultures was consistent across natural forests, planted grasslands, croplands and pot systems, except for young planted forests. Transgressive overyielding was only evident for planted grasslands. The log response ratio of fine root biomass in species mixtures to that in respective monocultures increased with species richness across all ecosystem types, and also increased with experiment age in grasslands.Main conclusionsOur meta‐analysis reveals positive effects of species diversity on below‐ground productivity. Despite profound differences in environments among terrestrial ecosystems, our analysis demonstrated that below‐ground productivity responds similarly to variations in species richness. Furthermore, our study also reveals shifts in the effects of diversity over time in both forests and grasslands. Future efforts are needed to further understand below‐ground productivity–diversity relationships.

Inter-varietal interactions among plants in genotypically diverse mixtures tend to decrease herbivore performance.

Much research has explored the effects of plant species diversity on herbivore populations, but far less has considered effects of plant genotypic diversity, or how abiotic stressors, like drought, can modify effects. Mechanisms by which plant genotypic diversity affects herbivore populations remain largely unresolved. We used greenhouse studies with a model system of wheat (Triticum aestivum L.) and bird cherry-oat aphid (Rhopalosiphum padi L.) to determine whether the genotypic diversity of a plant's neighborhood influences performance and fitness of herbivores on a focal plant and if drought changes the influence of neighborhood diversity. Taken across all varieties we tested, plant-plant interactions in diverse neighborhoods reduced aphid performance and generated associational resistance, although effects on aphids depended on variety identity. In diverse mixtures, drought stress greatly diminished the genotypic diversity-driven reduction in aphid performance. Neighborhood diversity influenced mother aphid size, and appeared to partially explain how plant-plant interactions reduced the number of offspring produced in mixtures. Plant size did not mediate effects on aphid performance, although neighborhood diversity reduced plant mass across varieties and watering treatments. Our results suggest inter-varietal interactions in genotypic mixtures can affect herbivore performance in the absence of herbivore movement and that abiotic stress may diminish any effects. Accounting for how neighborhood diversity influences resistance of an individual plant to herbivores will help aid development of mixtures of varieties for managing insect pests and clarify the role of plant genotypic diversity in ecosystems.