High Nutrient Conditions Research Articles

Invasive plant species support each other's growth in low-nutrient conditions but compete when nutrients are abundant.

Globally, numerous ecosystems have been co-invaded by multiple exotic plant species that can have competitive or facilitative interactions with each other and with native plants. Invaded ecosystems often exhibit spatial heterogeneity in soil moisture and nutrient levels, with some habitats having more nutrient-rich and moist soils than others. The stress-gradient hypothesis predicts that plants are likely to engage in facilitative interactions when growing in stressful environments, such as nutrient-deficient or water-deficient soils. In contrast, when resources are abundant, competitive interactions between plants should prevail. The invasional meltdown hypothesis proposes that facilitative interactions between invasive species can enhance their establishment and amplify their ecological impact. Considering both hypotheses can offer insights into the complex interactions among invasive and native plants across environmental gradients. However, experimental tests of the effects of soil moisture and nutrient co-limitation on interactions between invasive and native plants at both interspecific and intraspecific levels in light of these hypotheses are lacking. We performed a greenhouse pot experiment in which we cultivated individual focal plants from five congeneric pairs of invasive and native species. Each focal plant was subjected to one of three levels of plant-plant interactions: (1) intraspecific, in which the focal plant was grown with another individual of the same species; (2) interspecific, involving a native and an invasive plant; and (3) interspecific, involving two native or invasive individuals. These plant-plant interaction treatments were fully crossed with two levels of water availability (drought vs. well-watered) and two levels of nutrient supply (low vs. high). Consistent with the stress-gradient and invasional meltdown hypotheses, our findings show that under low-nutrient conditions, the biomass production of invasive focal plants was facilitated by invasive interspecific neighbors. However, under high-nutrient conditions, the biomass production of invasive focal plants was suppressed by invasive interspecific neighbors. When competing with native interspecific neighbors, high-nutrient conditions similarly enhanced the biomass production of both invasive and native focal plants. Invasive and native focal plants were neither competitively suppressed nor facilitated by conspecific neighbors. Taken together, these results suggest that co-occurring invasive exotic plant species may facilitate each other in low-nutrient habitats but compete in high-nutrient habitats.

Digest: Large-effect loci involved in maturation timing affect the early survival of Atlantic salmon.

How might variation in genomic regions that impact many traits modulate fitness across different life stages? Aykanat et al. (2024) show that two large-effect loci associated with age at maturity, six6 and vgll3, impact the survival of wild Atlantic salmon (Salmo salar) through nutrient-dependent, indirect genetic effects. Specifically, the late maturation allele in parental vgll3, and the early maturation allele in maternal six6, increase survival in early life under high nutrient conditions.

It is time to reconsider the use of naturally-occurring endotoxins in endotoxin recovery studies: Part 2 of a BioPhorum harmonized endotoxin recovery study

The evaluation of Naturally Occurring Endotoxins (NOEs) for Low Endotoxin Recovery (LER) studies has been a topic in the industry and regulatory agencies have been hesitant to endorse NOE use in LER studies over purified Lipopolysaccharide (LPS) standards such as Control Standard Endotoxin (CSE) or Reference Standard Endotoxin (RSE). In a recent study involving 11 BioPhorum member companies across 13 sites, NOEs prepared in high and low nutrient conditions were evaluated in two common monoclonal antibody buffer formulations: 10 mM Sodium Citrate, 0.05 % Polysorbate 80, pH 6.0 and 20 mM Histidine, 0.05 % Polysorbate 80, pH 6.0. 12 g-negative bacterial isolates were used to prepare NOE analytes, which were spiked into the formulation buffers. Additionally, the NOEs were spiked into Limulus Amebocyte Lysate (LAL) reagent water as controls and purified LPS into the citrate/polysorbate buffer as the LER control. Results showed the average of three runs per organism was >50 % recovery, at the conclusion of the 7-day period, regardless of nutrient culture preparation conditions. Furthermore, purified LPS controls became undetectable (<50 % recovery) in the citrate/polysorbate buffer, highlighting the presence of LER. These findings highlight the potential value of using NOEs from relevant manufacturing facilities to assess overall risk when purified LPS recovery is insufficient.

Chlorophyll fluorescence characteristics and H2O2 contents of Chinese tallow tree are dependent on population origin, nutrients and salinity.

Plants from invasive populations often have higher growth rates than conspecifics from native populations due to better environmental adaptability. However, the roles of improved chlorophyll fluorescence or antioxidant defenses in helping them to grow better under adverse situations are insufficient, even though this is a key physiological question for elucidating mechanisms of plant invasion. Here, we conducted experiments with eight native (China) and eight introduced (USA) populations of Chinese tallow tree (Triadica sebifera). We tested how salinity, nutrients (overall amount or N:P in two separate experiments) and their interaction affected T. sebifera aboveground biomass, leaf area, chlorophyll fluorescence and antioxidant defenses. Plants from introduced populations were larger than those from native populations, but salinity and nutrient shortage (low nutrients or high N:P) reduced this advantage, possibly reflecting differences in chlorophyll fluorescence based on their higher PSII maximum photochemical efficiency (F v/F m) and PSI maximum photo-oxidizable P700 in higher nutrient conditions. Native population plants had lower F v/F m with saline. Except in high nutrients/N:P with salinity, introduced population plants had lower electron transfer rate and photochemical quantum yield. There were no differences in antioxidant defenses between introduced and native populations except accumulation of hydrogen peroxide (H2O2), which was lower for introduced populations. Low nutrients and higher N:P or salinity increased total antioxidant capacity and H2O2. Our results indicate that nutrients and salinity induce differences in H2O2 contents and chlorophyll fluorescence characteristics between introduced and native populations of an invasive plant, illuminating adaptive mechanisms using photosynthetic physiological descriptors in order to predict invasions.

Greater capacity for division of labor brings greater benefits to an invasive clonal plant than its native partners

The majority of problematic invasive plants exhibit clonal growth, and the clonal traits are widely recognized as critical determinants contributing to their invasiveness. Division of labor represents a crucial advantage associated with clonal growth; therefore, it is reasonable to anticipate that this particular trait may confer a growth advantage upon invasive clonal species in comparison to native ones. To test this hypothesis, we conducted a comparative experiment in the greenhouse involving the highly invasive plant Alternanthera philoxeroides, its native congener A. sessilis, and its native co-occurring Jussiaea repens. We grew clonal fragments of these three stoloniferous plants under negative spatial covariance of light and soil nutrients while either preventing or allowing division of labor through severing or keeping intact their stolon connections. The results showed that stolon connection significantly increased the root mass to shoot mass ratio of basal ramets under low light and high soil nutrient conditions, but greatly decreased it in the apical ramets under high light and low soil nutrient conditions, suggesting induced division of labor in all studied plants. Moreover, the invasive plant A. philoxeroides demonstrated a greater capacity for division of labor than its co-genus and co-occurring native partners, which conferred it with greater growth performance at the whole clonal fragment level. Given that the commonly observed competitive superiority of invasive clonal plants over co-occurring native species due to their high intrinsic growth rates, these findings suggest that the division of labor may confer a competitive advantage upon some invasive clonal plants, thereby facilitating their successful invasion in heterogeneous habitats characterized by a strong negative correlation between light availability and soil nutrient levels.

The genomic basis of nitrogen utilization efficiency and trait plasticity to improve nutrient stress tolerance in cultivated sunflower.

Maintaining crop productivity is challenging as population growth, climate change, and increasing fertilizer costs necessitate expanding crop production to poorer lands whilst reducing inputs. Enhancing crops' nutrient use efficiency is thus an important goal, but requires a better understanding of related traits and their genetic basis. We investigated variation in low nutrient stress tolerance in a diverse panel of cultivated sunflower genotypes grown under high and low nutrient conditions, assessing relative growth rate (RGR) as performance. We assessed variation in traits related to nitrogen utilization efficiency (NUtE), mass allocation, and leaf elemental content. Across genotypes, nutrient limitation generally reduced RGR. Moreover, there was a negative correlation between vigor (RGR in control) and decline in RGR in response to stress. Given this trade-off, we focused on nutrient stress tolerance independent of vigor. This tolerance metric correlated with the change in NUtE, plasticity for a suite of morphological traits, and leaf element content. Genome-wide associations revealed regions associated with variation and plasticity in multiple traits, including two regions with seemingly additive effects on NUtE change. Our results demonstrate potential avenues for improving sunflower nutrient stress tolerance independent of vigor, and highlight specific traits and genomic regions that could play a role in enhancing tolerance.

Influence of light, nutrients, and soil moisture on the growth and resource allocation of Arundo donax

AbstractUnderstanding how invasive species respond to changes in abiotic factors and what influences their ability to colonise newly disturbed areas is necessary to predict species expansion, prioritise management efforts, and develop ecological models. We conducted a fully factorial greenhouse experiment using rhizome fragments to examine the effects of four nutrients levels, three soil moisture levels, and two light levels (with five replicates, n = 120) on the growth and resource allocation patterns of Arundo donax, a large‐statured invasive wetland species. We predicted that A. donax's performance‐related traits—traits that directly influence the functionality and fitness of an individual—such as aboveground biomass (AGB), belowground biomass (BGB), net photosynthesis, and average stem height, would be highest under high light, high soil moisture and high nutrient conditions due to the ability of aggressive invasive species to capitalise on greater resource availability. Analyses using general linear mixed‐effects models revealed significant interactions between soil moisture and light. Plants grown in saturated, high light conditions exhibited the highest values for performance‐related traits. However, contrary to predictions, nutrients did not significantly influence these traits. Multivariate analysis of variance demonstrated that nutrients did influence biomass allocation patterns, with plants grown with added nitrogen and phosphorus displaying higher AGB:BGB and stem:leaf ratios. This research highlights A. donax's unique response to nutrient addition and the plasticity of biomass allocation patterns. By understanding how invasive species respond to common abiotic factors, we can better predict their expansion and prioritise management efforts, such as focusing on areas of low overstory shading, while also providing crucial information for ecological model development.

Aboveground antagonists mitigate belowground plant–antagonist interactions but not affect plant–mutualist interactions

Species interactions exert important influences on biodiversity and ecosystem stability. In complex natural communities, species interactions have gone beyond pairwise mechanisms, as interactions between two species can be regulated by one or more other species (higher-order species interactions). However, few studies consider higher-order interactions among organisms that are indirectly contacted, particularly under high soil nutrient conditions. Here, we performed a common garden experiment to investigate how natural herbivory (aboveground weevil) and simulated herbivory (leaf clipping) affect plant (Triadica sebifera) interactions with soil antagonists (root-knot nematodes) and mutualists (arbuscular mycorrhizal fungi; AMF) under nitrogen and phosphorus addition. We also tested the effects of nitrogen, phosphorus, and herbivory-stimuli on T. sebifera leaf extrafloral nectary (EFN) production. We found that T. sebifera can compensate for biomass loss caused by clipping or weevil feeding, moreover, high nitrogen availability caused plant biomass to outpace herbivory-stimuli. Plant–antagonist (root-knot nematodes) interactions were not affected by clipping or weevil feeding under ambient nitrogen condition but were reduced by clipping or weevil feeding under high nitrogen supply, however, we did not find the same pattern under phosphorus addition. Aboveground herbivory-stimuli did not affect plant–mutualist (AMF) interactions, whether fertilized or not. In addition, nitrogen addition stimulated plants to secrete more EFN against clipping but did not increase EFN production against weevil feeding. Clipping and weevil feeding exhibited consistent effects on both plant–antagonist (root-knot nematodes) interactions and plant–mutualist (AMF) interactions. These results suggest that aboveground antagonists mainly mitigate belowground plant–antagonist interactions but not affect plant–mutualist interactions, and higher-order species interactions depend on nitrogen addition but not phosphorus addition.

More is not always better: Impact of nutrient-addition on floral traits important for buzz pollination

Nutrient addition can affect plant fitness by altering resource allocation to reproduction or modifying floral traits. Alterations in floral attributes, particularly in species that exhibit specialization in specific ecological niches, can disrupt or augment the dynamics of interactions between plants and their pollinators. However, very little is known about how soil enrichment affects the floral characteristics and pollen release dynamics of buzz pollinated plants. Our study analyzed the effects of nutrient enrichment on the reproductive traits of a buzz pollinated plant species. Under greenhouse conditions, we established a phosphorus-rich nutrient gradient to investigate the impact of such enrichment on tomato plants (Solanum lycopersicum). Our study focused on: i) flowering patterns, ii) flower morphology, iii) pollen release from anthers, and iv) pollen quantity and quality (protein concentration). Plants were grown in low, intermediate, and high nutrient conditions, and various functional traits that are essential for buzz pollination were examined. Adding nutrients improved the display of flowers. Morphometric traits important for pollinator attraction and interaction, such as floral diameter, anther-tube width, and petal width, showed an increase in the high nutrient condition. The pollen quality and quantity were found to be unaltered; however, flowers originating from intermediate and high nutrient conditions exhibited reduced pollen release upon buzzing despite possessing ample pollen reserves. Our findings suggest that the positive effects of nutrient addition on floral traits are limited to a narrow range of concentrations. Higher concentrations can diminish these effects and impact the accessibility of pollen, as well as the reproductive performance of plants. In conclusion, based on our results, we predict that changing land use scenarios leading to nutrient accumulation may have significant consequences for plant-pollinator interactions.

Periphyton enzymatic activities in the water column along internal low-phosphorus nutrient gradients in the Everglades Stormwater Treatment Areas

The Everglades Stormwater Treatment Areas (STAs), important components in the Everglades Restoration efforts, were built to remove excess phosphorus (P) from stormwater runoff before it enters the Everglades Protection Area. The STAs operate within the low phosphorus domain of constructed wetlands and are mandated to achieve ultra-low P outflow concentrations to protect the receiving water bodies. Microbial processing by periphyton enzymatic activity under these low-P conditions may be critical for achieving nutrient reduction, particularly in the lower reaches of the STA treatment cells where nutrients are primarily in the dissolved organic and particulate forms. Enzymes are produced by periphyton to liberate required nitrogen (N), carbon (C), and P from dissolved organic matter under nutrient limiting conditions. Enzyme activity had not been measured within the STA treatment cells and this study was conducted to evaluate if enzyme activity occurs along the nutrient transect from inflow to outflow in well-performing treatment cells and if this activity differs within the dominant vegetation communities (i.e., emergent or submerged aquatic vegetation, EAV and SAV, respectively). The STAs receive variable hydraulic and nutrient loadings and the potential influence of these conditions on enzyme activity was evaluated under a range of loadings. The periphyton response in three different well-performing STA treatment cells (STA-2 Cells 1 and 3 and STA-3/4 Cell 3B) was evaluated using periphyton that accrued in the water column over a 7-d period. Because nutrient cycling is interrelated, a suite of enzyme activity associated with nutrient acquisition from dissolved organic material was measured. Enzymes associate with P-acquisition (phosphatase; alkaline phosphatase and bis-phosphodiesterase), C-acquisition (β-glucosidase), and N-acquisition (leucine aminopeptidase) were measured along internal transects from inflow to outflow.We found that enzyme activity occurs in the STA treatment cells and the most reactive enzymes were the phosphatase and N-acquisition enzymes; there was little activity and variability measured in the C-acquisition enzyme. Phosphatase activity increased along the nutrient gradient and the rates became more variable at the midflow and outflow transect locations. When dissolved organic P (DOP) in the surface water was above 10 μg/L, the phosphatase rates were reduced, an expected response since enzyme production occurs only during nutrient limiting conditions. When DOP concentrations were <10 μg/L, greatly increased rates were observed but there were still also times when the rates were reduced that did not appear to be influenced by surface water organic P or N concentrations or water depths. The activity for N-acquisition enzyme was also found to be variable, but this variability was between each treatment cell rather than along the transect as observed for phosphatase activity. The proportional change of each enzyme activity to the other was used to evaluate nutrient limiting conditions in the periphyton. Along the transect, both N- and P-limiting conditions were found in the periphyton at the inflow and midflow sites and solely P-limiting conditions at the outflows in all treatment cells. This implies that the mineralization processes can be disrupted under higher nutrient conditions, impacting cycling of the organic material. There were also indications that nutrient cycling may differ between periphyton from the EAV and SAV communities under low-P conditions, suggesting there may be a complementary enzymatic response within a mixed marsh configuration that may enhance nutrient cycling.

Contrasting effects of river inflow and seawater intrusion on zooplankton community structure in Jiaozhou bay, the Yellow Sea

Environmental changes associated with river inflow and seawater intrusion are known to affect zooplankton communities in coastal systems, but how zooplankton respond to these environmental changes remains unclear at present. Here we explored the effects of river inflow and seawater intrusion on zooplankton community structure in Jiaozhou Bay. The results showed that the river inflow and seawater intrusion are key in driving zooplankton dynamics, but with contrasting effects. According to the distinct hydrographic conditions, the sampling area could be geographically divided into the river inflow area with low-salinity and high-nutrient conditions (i.e., EIZ) and the seawater intrusion zone with high-salinity and low-nutrient conditions (i.e., SIZ). There were significant differences in zooplankton communities (e.g., abundance and species composition) between the two regions with seasonal changes. For example, the zooplankton abundance was significantly higher in the SIZ than in the EIZ during spring, whereas an opposite pattern was observed for the summer season. In contrast, the species richness was higher in the EIZ than in the SIZ in spring, while an opposite variation trend was observed during summer. These results together suggested that the river inflow and seawater intrusion had contrasting effects on zooplankton community structure in different seasons. According to the canonical correspondence analysis, we observed that the zooplankton community structure was mainly driven by temperature, chlorophyll a (Chl a), and nutrients in the EIZ, but it was largely affected by salinity in the SIZ. The implication is that changes in temperature, Chl a, and nutrients as a result of river inflow and changes in salinity as a consequence of seawater intrusion are key in driving the dynamics of zooplankton communities in Jiaozhou Bay.

Planktonic foraminifera fluxes and their response to the Asian Monsoon: insights from the Maldives, Indian Ocean

This study describes seasonal changes in the fluxes of planktonic foraminifera in response to changes in environmental conditions during the Asian Monsoon. Sediment trap systems were deployed for a period of 1 year at two locations in the Maldives: Kardiva Channel and Inner Sea. Twenty-six (26) planktonic foraminifera were recognized, of which six species (Trilobatus sacculifer, Globorotalia menardii, Globigerinoides ruber, Globigerina siphonifera, Neogloboquadrina dutertrei, and G. bulloides) dominated the assemblage (82%–84%) in both sites. Planktonic foraminifera fluxes and chlorophyll-a concentrations are higher in the Inner Sea. Total planktonic foraminifera fluxes show preference to high nutrient conditions during monsoon periods. Planktonic foraminifera fluxes generally follow the trend of carbonate fluxes except during October-November 2014. Species flux generally reached maximum during the NE monsoon as a response to increase in nutrient concentration brought by the movement of the North Equatorial Current over the trap sites. The expansion of nutrient-rich surface waters, occurring eastward during the SW monsoon and westward during the NE monsoon, led to an increase in the population of species dwelling in both shallow (T. sacculifer and G. ruber) and deep waters (N. dutertrei and G. bulloides). Dominance of shallow-dwelling species T. sacculifer and G. ruber throughout the sampling period suggests stable stratification of the water column. This supports the idea of wind-mixing rather than local upwelling as the driving force for enrichment of nutrients and subsequent increase in planktonic foraminifera fluxes. Lateral advection and resuspension in settling of particles to the traps is evident based on the presence of benthic foraminifera in the Inner Sea samples. These processes, however, did not significantly mask climate and surface ocean signals since there remains a clear correlation between planktonic foraminifera fluxes and environmental conditions.

Zonation of The Waters of Spermonde Archipelago Base on Nutrient Concentration and Its Impact to Coral Reef Ecosystem

The Spermonde Archipelago is divided into four zones, the division of zones is based on the distribution of coral reefs, distance from the mainland, and water depth, but this condition tends to change as a result of high anthropogenic activity in the Spermonde Islands. Based on this, it is very necessary to re-zoning the Spermonde Archipelago Waters based on the condition of nutrient distribution. The research method uses the integration of remote sensing data analysis, field surveys, and secondary data which are then analyzed using the Boleean method for re-zoning. The results showed that the nutrient, in this case, chlorophyll-a, was concentrated in the deep zone (near the mainland) and the concentration was higher during the rainy season, this condition affected the coral reef cover in the Spermonde Islands. Based on these conditions, the Spermonde Islands waters are divided into three zones, namely the inner zone with high nutrient conditions with a benthic cover dominated by fleshy macroalgae, the middle zone with low nutrient conditions with crustose coralline dominance, and the outer zone with low nutrient conditions with algal turf dominance turf alga/corals.

"Resistance Is Futile": Weaker Selection for Resistance by Abundant Parasites Increases Prevalence and Depresses Host Density.

AbstractTheory often predicts that host populations should evolve greater resistance when parasites become abundant. Furthermore, that evolutionary response could ameliorate declines in host populations during epidemics. Here, we argue for an update: when all host genotypes become sufficiently infected, higher parasite abundance can select for lower resistance because its cost exceeds its benefit. We illustrate such a "resistance is futile" outcome with mathematical and empirical approaches. First, we analyzed an eco-evolutionary model of parasites, hosts, and hosts' resources. We determined eco-evolutionary outcomes for prevalence, host density, and resistance (mathematically, "transmission rate") along ecological and trait gradients that alter parasite abundance. With high enough parasite abundance, hosts evolve lower resistance, amplifying infection prevalence and decreasing host density. In support of these results, a higher supply of nutrients drove larger epidemics of survival-reducing fungal parasites in a mesocosm experiment. In two-genotype treatments, zooplankton hosts evolved less resistance under high-nutrient conditions than under low-nutrient conditions. Less resistance, in turn, was associated with higher infection prevalence and lower host density. Finally, in an analysis of naturally occurring epidemics, we found a broad, bimodal distribution of epidemic sizes consistent with the resistance is futile prediction of the eco-evolutionary model. Together, the model and experiment, supplemented by the field pattern, support predictions that drivers of high parasite abundance can lead to the evolution of lower resistance. Hence, under certain conditions, the most fit strategy for individual hosts exacerbates prevalence and depresses host populations.

Effects of arbuscular mycorrhizal fungi on plant growth and herbivore infestation depend on availability of soil water and nutrients.

Fitness of plants is affected by their symbiotic interactions with arbuscular mycorrhizal fungi (AMF), and such effects are highly dependent on the environmental context. In the current study, we inoculated the nursery shrub species Artemisia ordosica with AMF species Funneliformis mosseae under contrasting levels of soil water and nutrients (diammonium phosphate fertilization), to assess their effects on plant growth, physiology and natural infestation by herbivores. Overall, plant biomass was synergistically enhanced by increasing soil water and soil nutrient levels. However, plant height was surprisingly repressed by AMF inoculation, but only under low water conditions. Similarly, plant biomass was also reduced by AMF but only under low water and nutrient conditions. Furthermore, AMF significantly reduced leaf phosphorus levels, that were strongly enhanced under high nutrient conditions, but had only minor effects on leaf chlorophyll and proline levels. Under low water and nutrient conditions, specific root length was enhanced, but average root diameter was decreased by AMF inoculation. The negative effects of AMF on plant growth at low water and nutrient levels may indicate that under these conditions AMF inoculation does not strongly contribute to nutrient and water acquisition. On the contrary, the AMF might have suppressed the direct pathway of water and nutrient absorption by the plant roots themselves despite low levels of mycorrhizal colonization. AMF inoculation reduced the abundance of the foliar herbivore Chrysolina aeruginosa on plants that had been grown on the low nutrient soil, but not on high nutrient soil. Fertilization enhanced the abundance of this herbivore but only in plants that had received the high water treatment. The lower abundance of the herbivore on AMF plants could be related to their decreased leaf P content. In conclusion, our results indicate that AMF negatively affect the growth of Artemisia ordosica but makes them less attractive to a dominant herbivore. Our study highlights that plant responses to AMF depend not only on the environmental context, but that the direction of the responses can differ for different components of plant performance (growth vs. defense).

Fine-scale diversity of microbial communities due to satellite niches in boom and bust environments.

Recent observations have revealed that closely related strains of the same microbial species can stably coexist in natural and laboratory settings subject to boom and bust dynamics and serial dilutions, respectively. However, the possible mechanisms enabling the coexistence of only a handful of strains, but not more, have thus far remained unknown. Here, using a consumer-resource model of microbial ecosystems, we propose that by differentiating along Monod parameters characterizing microbial growth rates in high and low nutrient conditions, strains can coexist in patterns similar to those observed. In our model, boom and bust environments create satellite niches due to resource concentrations varying in time. These satellite niches can be occupied by closely related strains, thereby enabling their coexistence. We demonstrate that this result is valid even in complex environments consisting of multiple resources and species. In these complex communities, each species partitions resources differently and creates separate sets of satellite niches for their own strains. While there is no theoretical limit to the number of coexisting strains, in our simulations, we always find between 1 and 3 strains coexisting, consistent with known experiments and observations.

Nutrients and not temperature are the key drivers for cyanobacterial biomass in the Americas

Cyanobacterial blooms imperil the use of freshwater around the globe and present challenges for water management. Studies have suggested that blooms are trigged by high temperatures and nutrient concentrations. While the roles of nitrogen and phosphorus have long been debated, cyanobacterial dominance in phytoplankton has widely been associated with climate warming. However, studies at large geographical scales, covering diverse climate regions and lake depths, are still needed to clarify the drivers of cyanobacterial success. Here, we analyzed data from 464 lakes covering a 14,000 km north-south gradient in the Americas and three lake depth categories. We show that there were no clear trends in cyanobacterial biomass (as biovolume) along latitude or climate gradients, with the exception of lower biomass in polar climates. Phosphorus was the primary resource explaining cyanobacterial biomass in the Americas, while nitrogen was also significant but particularly relevant in very shallow lakes (< 3 m depth). Despite the assessed climatic gradient water temperature was only weakly related to cyanobacterial biomass, suggesting it is overemphasized in current discussions. Depth was critical for predicting cyanobacterial biomass, and shallow lakes proved more vulnerable to eutrophication. Among other variables analyzed, only pH was significantly related to cyanobacteria biomass, likely due to a biologically mediated positive feedback under high nutrient conditions. Solutions toward managing harmful cyanobacteria should thus consider lake morphometric characteristics and emphasize nutrient control, independently of temperature gradients, since local factors are more critical – and more amenable to controls – than global external forces.

Effects of clonal integration on characteristics of free-floating and submerged plant communities under different nutrient conditions

Individual-level effects of clonal integration have been extensively studied, but community-level effects remain poorly understood. We grew the free-floating or submerged plant communities with three speices dominated by free-floating Salvinia natans or submerged Vallisneria natans, respectively. The stolons of S. natans and V. natans were periodically severed, with not severed plant communities as control. The effects of clonal integration on the characteristics of different life-form plant communities under low versus high nutrient levels were examined. Results showed that clonal integration significantly increased the number of ramets in submerged plant communities but not in free-floating plant communities under two nutrient conditions. Clonal integration greatly decreased the growth of free-floating plant communities, changed their species composition, and increased their species diversity and evenness under high nutrient conditions but not under low nutrient conditions. In submerged plant communities, clonal integration and nutrient affected species composition independently but did not affect species diversity. The growth of submerged plant communities was only affected by nutrient. Our findings highlight the importance of nutrient and plant life form in the effects of clonal integration on aquatic plant community characteristics. Studies on the effects of clonal integration at the community level could provide references for the effective management of aquatic plant communities with different life forms and contribute to a better understanding of the importance of clonal integration in the field.

Plant host domestication and soil nutrient availability determine positive plant microbial response across the Solanum genus.

Domestication of crops has changed how crops shape their associated microbial communities compared with their progenitors. However, studies testing how crop domestication-driven differences in rhizosphere microbial communities affect plant health are limited mostly to specific symbiont pairings. By conducting a soil manipulation greenhouse study, we examined plant growth and yield in response to differences in microbial communities and nutrient availability across a variety of wild, landrace, and commercially available 'Modern' potatoes. Coupled with this, we conducted 16S and internal transcribed spacer (ITS) amplicon sequencing to examine plant host- and soil treatment-driven differences in microbial community composition on potato plant roots. We found that the plant response to microbes (PRM) was context dependent. In low nutrient conditions, landraces responded positively to the presence of live soil microbial inocula. Conversely, modern potato varieties responded positively only in high nutrient conditions. Amplicon sequencing found differences in bacterial communities due to environmental and temporal factors. However, potato clade (e.g. Andigenum, Chiletanum, Solanum berthaultii, and 'Modern') alone did not lead to differences in microbial communities that accounted for PRM differences. Differences in PRM between landraces and modern potatoes, and the correlation of PRM to microbial diversity, suggest that domestication and subsequent breeding have altered the S. tuberosum response to rhizosphere microbiomes between Andigenum, Chiletanum, and North American potato varieties.

Intercrop overyielding weakened by high inputs: Global meta-analysis with experimental validation

The relative intensity of facilitative effect among coexisting plant species is frequently affected by soil water and nutrient availability, such as nitrogen (N), phosphorus (P), potassium (K), and organic fertilizer. However, to date, the general pattern of nutrient gradient effects on plant–plant interactions remains inconsistent or even opposite in the intercropping systems. To address this issue, we performed a global meta-analysis and three experiments to investigate the production efficiency of intercropping along fertilizer input gradient (low vs. high) by assessing the land equivalent ratio (LER). Trial 1 included five P gradient in the maize–grass pea intercropping system. Trial 2 consisted of two N gradient in the maize–wheat, maize–soybean and wheat–soybean intercropping systems. Trial 3 contained two water and three P gradients in the same intercropping systems as Trial 1. The meta-analysis result indicated that the average LER for yield (LERY), biomass (LERB), N uptake (LERN), and P uptake (LERP) were 1.49, 1.25, 1.35, and 1.66, respectively. It implied that intercropping would save 49 %, 25 %, 35 % and 66 % lands to achieve the same yield, biomass, N and P uptake amount as monoculture, respectively. Also, high fertilizer inputs significantly decreased the relative productivity and nutrient uptake. Average effect sizes of high inputs on LERY, LERB, LERN, and LERP were up to − 0.0505 (−0.0550 to −0.0461), − 0.0267 (−0.0303 to −0.0230), − 0.0321 (−0.0395 to −0.0247) and − 0.0237 (−0.0370 to −0.0103), respectively. These negative values demonstrated that the LER markedly declined under the high-nutrient conditions. On the other hand, the results of Trial 1 confirmed that the LERY, LERB, LERN, and LERP tended to decrease significantly with increasing P addition. In Trial 2, the LERY of intercropping systems tended to significantly decrease with increasing N application. In Trial 3, the LERY, LERB, LERN, and LERP also displayed a descending trend with increasing P addition and soil water availability. Collectively, the three trials confirmed the reliability and universality of the meta-analysis conclusions. This study provided a broad support for the hypothesis of the nutrient-dependent relative benefits in intercropping systems.