Levels Of Nutrient Availability Research Articles

A review on bacterial enriched vermicompost and its applications

Generation of the massive quantity of solid waste around the globe is a major ecological and technical problem. Vermicomposting may be the viable option to handle solid waste in an environmentally friendly way. Vermicompost have higher level of available nutrients like carbon, nitrogen, phosphorous and potassium, calcium and magnesium which are derived from the wastes. Many researchers have attempted to evaluate for development of efficiency vermicompost by using varieties of earthworms. The use of earthworms in the degradation of different types of wastes is continuing from the past so many years. These wastes include industrial, agricultural of plant debris and domestic waste papers and cattle dung. Fixed nitrogen is a limiting nutrient in most environments, with the main reserve of nitrogen in the biosphere being molecular nitrogen from the atmosphere. Molecular nitrogen cannot be directly assimilated by plants, but it becomes obtainable through the biological nitrogen fixation process that only prokaryotic cells have developed. Vermicompost is an effective carrier for bacterial growth so that the symbiotic bacterial species such as Mycorrhiza and Dyaztotor of helps in the rapid growth of plant while Azotobactor, Rhizobium involves in the fixation and storing of nitrogen for plants. This review focus on the vermicomposting and microbial enrichment of vermicompost for the exceed crop production.

Phytoplankton composition in Mediterranean confined coastal lagoons: testing the use of ecosystem metabolism for the quantification of community-related variables

Estimations of ecosystem metabolism have rarely been used to quantify productivity in structural reductionist approaches for the description of phytoplankton composition. However, estimations of ecosystem metabolism could contribute to a better understanding of the relationship between phytoplankton composition and ecosystem functioning. To examine this, we investigated the community structure of phytoplankton in a set of Mediterranean coastal lagoons (natural and artificial) during a hydrological cycle to identify the most important environmental variables determining phytoplankton species composition. The focus of the study was on the quantification of productivity-related variables using estimations of ecosystem metabolism, such as different proxies for the estimation of the production-to-biomass ratio and of the relative importance of K- and r-strategies, which are commonly used conceptually but not quantified. Our results demonstrated differences in phytoplankton composition between seasons, due to the dominant hydrological pattern of flooding confinement in the salt marsh, and between lagoons that were caused by different levels of nutrient availability. Moreover, there was a notable decrease in the production/biomass ratio and a prevalence of K-strategists with seasonal succession, as predicted by Margalef’s mandala. Thus, the results showed that estimations of ecosystem metabolism are useful for the higher frequency quantification of important ecological variables, and contribute to a better understanding of planktonic assemblages, and physical and chemical changes, in these fluctuating ecosystems.

Phloem Sap and Wood Carbon Isotope Abundance (δ13C) Varies with Growth and Wood Density of Eucalyptus globulus under Nutrient Deficit and Inform Supplemental Nutrient Application

Eucalyptus globulus, commonly known as blue gum or southern blue gum, is a tall, evergreen tree endemic to southeastern Australia. E. globulus is grown extensively in plantations to improve the sustainability of timber and fibre production across Australia. Sustainable forest management practices necessitate the consideration of ‘off-site’ carbon and ecological footprints. Pursuing optimal supplemental nutrient application and maximum growth rates is therefore critical to the establishment of a sustainable timber and fibre production industry. Biological indicators that can predict growth responses are therefore of extreme value. We investigated the carbon isotope abundance of wood cellulose (δ13Ccel) in E. globulus to determine potential relationships with the carbon isotope abundance of phloem sap (δ13Cphl) where the trees were subjected to different level of nutrient availability. This study also sought to determine the effect of nutrient additions on the growth of the E. globulus and to quantify the relationship between the volumetric growth of wood and δ13Ccel. Phloem sap and wood cores were collected from trees within study plots which were subjected to seven nutrient treatments over a two-year period in a monoculture E. globulus plantation in South Australia. Phloem sap was collected using the razor blade technique and wood cores were collected using a stem borer. The carbon isotope abundance (δ13C) of phloem sap and wood grown in the radial direction of the stem were determined. The basic and dry densities of wood were determined, and their relationships with phloem and wood δ13C were established. The δ13Cphl was significantly correlated with δ13Ccel. The relationship between δ13Ccel and the wood density of the respective wood sections was significant but did not consistently show the same pattern. There was no significant variation in basic density observed along the radial direction of the stem wood of the short-rotation E. globulus trees. A positive correlation was observed between δ13Ccel and the wood basic density, but the relationship was not consistent along the radial direction of the stem. However, positive correlations were observed between δ13Ccel and the air-dry density of respective wood sections. The relationship between phloem and wood δ13C and the relationship between δ13C and wood density along the radial direction of the stem needs to be considered while monitoring forest growth under nutrient- and water-limited conditions.

Unperforated film-covered planting contributes to improved film recovery rates and foxtail millet grain yields in sandy soils

Plastic film mulching improves the soil water content and temperature and, thus, contributes to enhanced grain yield in arid and semi-arid areas, such as Northwest China. However, in traditional film-covering methods, plastic films are difficult to recycle, causing environmental issues. Therefore, developing cultivation methods with enhanced film recovery rates is important for sustainable agricultural development. Here, we evaluated how the planting method affected the soil temperature, water content, film recovery rate, and grain yield by applying the following three planting patterns to the traditional crop, foxtail millet, in 2021–2022: no plastic film mulching (NP), plastic film mulching (MP), and planting on the film edge (PFE); in the latter, holes were not punched in the film and crops were planted approximately 5 cm from the film edge. The results for 2021 showed that the biomass ranged from 27.69 g to 33.76 g per plant, and the biomass was increased by 21.9% and 3.2% in PFE compared with NP and MP, respectively. However, in 2022, the biomass increased in PFE by 52.5% and 17.7% compared with NP and MP, respectively. In 2021, the highest grain yield was observed in PFE (2480 kg/hm2), followed by MP (2470 kg/hm2) and NP (2343 kg/hm2); in 2022, a significantly higher grain yield was observed in PFE than that in MP and NP. Although the soil temperature increased in PFE, it was not as high as in MP. The relatively higher soil temperature increased the root growth process, stimulated the production of root exudates (acetic acid and citric acid), and increased the soil enzyme (sucrase and urease) activity. Increases in organic acids and soil enzymes assisted in the decomposition of soil organic matter and induced relatively higher levels of available nutrients, such as nitrogen and phosphorus, and the higher root reuse rates contributed to higher grain yields. In addition, fewer holes were punched in the film of the PFE model, which improved film recovery, and the recovery rate of PFE was higher than that of MP. These results indicate that the proposed unperforated film-covered planting pattern is suitable for millet production in sandy soil.

Soil nutrient limitation and natural enemies promote the establishment of alien species in native communities.

The invasion of alien plant species threatens the composition and diversity of native communities. However, the invasiveness of alien plants and the resilience of native communities are dependent on the interactions between biotic and abiotic factors, such as natural enemies and nutrient availability. In our study, we simulated the invasion of nine invasive plant species into native plant communities using two levels of nutrient availability and suppression of natural enemies. We evaluated the effect of biotic and abiotic factors on the response of alien target species and the resistance of native communities to invasion. The results showed that the presence of enemies (enemy release) increased the biomass proportion of alien plants while decreasing that of native communities in the absence of nutrient addition. Furthermore, we also found that the negative effect of enemy suppression on the evenness of the native community and the root-to-shoot ratio of alien target species was greatest under nutrient addition. Therefore, nutrient-poor and natural enemies might promote the invasive success of alien species in native communities, whereas nutrient addition and enemy suppression can better enhance the resistance of native plant communities to invasion.

Using participatory geographic information systems (PGIS) mapping to describe household food access in Buffalo, New York

ABSTRACT Despite existing only blocks apart, neighborhoods in Buffalo, NY can have very different levels of food availability and access due to their local food environment. This study uses participatory geographic information systems (PGIS) mapping and qualitative interviewing to describe these food environments based on the lived experiences of Buffalo residents. PGIS mapping interviews were conducted with residents of the city who regularly used food pantries and focused on access to and availability of both free food resources (such as soup kitchens and food pantries) and purchased food resources (such as grocery stores). Participants were also asked about food access in their own neighborhood, their perceptions of food access in the city, and what develops they thought would contribute to greater food security for their neighborhoods. Results show cost of living and transportation were important barriers to food access for many participants. Findings suggest that residents of historically marginalized neighborhoods in Buffalo continue to have lower access to affordable healthy foods.

Fertilization benefits the facultative parasitic plant Rhamphicarpa fistulosa while gains by the infected host Oryza sativa are marginalized.

Rhamphicarpa fistulosa (Hochst.) Benth. is an annual facultative parasitic plant adapted to hydromorphic soils. In sub-Saharan Africa it causes high crop losses as a weed in rainfed lowland rice (Oryza sativa L.). Fertilizers are often proposed as a control measure against hemiparasitic weeds, but an understanding of the nutrient effects on R. fistulosa is currently still elusive. In two greenhouse pot experiments, conducted in 2016 in the Netherlands and in 2019 in the UK, host plants (O. sativa, cv IR64) and parasitic plants (R. fistulosa) were grown alone or combined and were subjected to different levels of nutrient availability. Biomass measurements were used to assess whether and how effects of nutrient availability are expressed in the host and parasite. Compared with parasite-free host plants, the biomass of parasite-infested plants was severely reduced, and nutrient effects on host plant biomass were less pronounced. Conversely, increased nutrient availability did not have an effect on parasitic plants when grown alone, but when grown with a host the parasitic plant biomass increased proportionally. Grown together, the combined biomass of host plant and parasite was substantially lower than that of the host plant grown alone. The ratio of biomass between host plant and parasite was unaffected by nutrient availability. Fertilization benefits to rice plants are severely reduced but not completely nullified by R. fistulosa infection. The benefits to production and reproduction accrued by the parasite from increased nutrient availability are restricted to conditions in the presence of a host plant. Host presence and nutrient effects are thus observed to be synergetic; R. fistulosa plants parasitizing a suitable host respond strongly to increasing levels of nutrients. This is associated with an increased root biomass of the parasitic plant itself, but is more likely to result from exploitation of the nutrient uptake capacity of the host plant it parasitizes.

Individuals of a group-living shorebird show smaller home range overlap when food availability is low

BackgroundGroup living animals, such as shorebirds foraging on intertidal mudflats, may use social information about where to find hidden food items. However, flocking also increases intraspecific competition for resources, which may be exacerbated by food scarcity. Therefore, although aggregation may bring benefits, it may also increase the intensity of intraspecific competition.MethodsWe examined this trade-off in adult great knots Calidris tenuirostris, a molluscivorous long-distance migrating shorebird species, using interannual variation based on 2 years with different levels of food availability during their northward migratory staging in the northern Yellow Sea, China. We estimated individual home ranges and the extent of spatial overlap of home ranges of individually tagged birds in 2012 and 2015, whilst discounting for possible differences in body size, body mass, sex and migration schedule between years.ResultsWe found that home range size was not associated with body mass, arrival date, body size, or sex of the individual. Despite a significant difference in food availability between the two study years, there was no significant change in the 50% and 95% home range size of great knots in the contrasting situations. However, there was a significantly smaller spatial overlap between individuals in the year when food was less available, suggesting that great knots operated more independently when food was scarce than when it was abundant.ConclusionsThese results suggest that minimizing intraspecific competition became more important when food was scarce. Where it is impossible to monitor all habitats en route, monitoring the local movements of shorebirds may offer a way to detect changes in habitat quality in real time.

Effects of nutrients and light in aquatic habitat on the growth of Hydrocotyle vulgaris when expanded from terrestrial to aquatic habitat

Many amphibious clonal plants in aquatic-terrestrial ecotones commonly expand from terrestrial to aquatic habitats. Nutrient availability and light intensity are both key factors affecting plant growth in aquatic habitats, but little is known about the role of nutrient availability and light intensity in aquatic habitats during the expansion of amphibious clonal plants from terrestrial to aquatic habitats, when clonal integration is maintained. We conducted a greenhouse experiment to simulate expansion from terrestrial to aquatic habitats of the amphibious clonal plant Hydrocotyle vulgaris. We grew basal portions of clonal fragments in soil and connected the apical portions of the same fragments to water which subjected to three levels of nutrient availability under a low or a high light condition. High nutrient level and light condition increased the growth of the apical portions of H. vulgaris and thus increased the performance of the whole clones. Meanwhile, root-shoot mass ratio of the apical portions and the basal portions were higher at the high light condition and the low nutrient level. Results suggest that the relatively high levels of nutrients and light condition in aquatic habitats can improve the expansion of apical portions from terrestrial to aquatic habitats. Our results also suggest that maintaining clonal integration may benefit the expansion of H. vulgaris via the trade-off of biomass allocation which can optimize the utilization of resources. These results may provide theoretical basis for community dynamics prediction and vegetation restoration in the ecotones such as wetlands.

Imports and Food Security

The Food and Agriculture Organization considers imports crucial to food security (FS) based on their inclusion in the FS definition. Given the broadening of the definition of FS to more than just food availability, the real impact of imports on FS is questionable. This article analyzes the effect of imports on FS in 56 lower-middle income countries from 2011 to 2016. Adopting the generalized method of moments technique, the estimation results point to the negative effects of imports on FS. The breakdown analysis for each dimension indicates that the level of food availability tends to be higher with imports. This could be why imports are considered part of FS measurement. However, the remaining three dimensions, level of food accessibility, utilization, and stability, do against imports. This could explain why the negative impacts of imports outweigh the positive ones in the net. This study indicates that the inclusion of imports in FS can help to secure stable food supplies and meet shortfalls in local production through a better import regulation system. JEL Classification O11, Q00

Induction of resistance, enzyme activity, and phytochemicals in canola plants treated with abscisic acid elevated based on nutrient availability: a case study on Brevicoryne brassicae L. (Hemiptera: Aphididae).

The cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae), is one of the important pests of cruciferous plants throughout the world including Iran. In the present study, we grew cultivated canola plants under different fertilizers or distilled water and sprayed them with 100 µM abscisic acid (ABA) or a control solution (NaOH dissolved in water) to study (i) the antibiosis parameters of B. brassicae on these plants; (ii) the antixenosis of B. brassicae adults on these plants; (iii) the plant's peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) activity; and (iv) the plant's total phenolic and glucosinolate content. The results of antibiosis experiments showed that ABA and fertilizers have a profound and negative effect on the performance of B. brassicae. In the antixenosis experiment, control plants attracted a significantly higher number of adult females in comparison to treated plants. Also, B. brassicae had lower performance and preference when they were reared on the ABA-treated fertilized plants with higher levels of phenolic and glucosinolate content. These results prompted us to hypothesize that fertilizers enable canola plants to trigger a higher level of secondary metabolites. Our findings reveal that the type and level of nutrient availability may have different impacts on how the plant regulates its defense mechanisms.

Role of Nutrients in Plants, Its Deficiency and Management

Plants like all living beings need energy source. The energy needed by the plants are uptaken in the form of 17 essential elements. Among which Carbon, hydrogen, and oxygen are derived from surrounding. The remaining 14 essential necessary elements are supplied either from rhizosphere and soil organic matter or by important organic or inorganic fertilizers or value added soil amendments. Plants start showing nutrient deficiency when they do not get the necessary nutrients. More nutrient use can also show poor growth because of toxic chemicals in soil. So, required amount of use and the placement of nutrients is necessary. Soil and plant tissue tests have been developed to assess their’ nutrient content. By analysis, plant scientists determined the nutrient need of plant in a given soil. In addition to the levels of available nutrients, soil pH shows its role in nutrient availability and elemental toxicity in soil. In the majority, disease effect in crop plants has been reduced by fertilizer application. This is due to the host plant tolerance or resistance mechanisms involve these nutrients. When the plants were deficient, the application of nutrients significantly reduced disease.

Plant–soil feedbacks in a diverse grassland: Soil remembers, but not too much

Abstract Plant–soil feedbacks (PSFs) are one of the major drivers of species coexistence in highly dynamic and low‐diversity communities, such as early successional stands or agricultural systems. However, in stable and species‐rich communities, PSFs are much more complex because of numerous species interactions. In this study, we aimed to reveal if PSFs of a dominant species can be detected within a diverse plant community and to what extent they can be influenced by the effects of co‐occurring species. We investigated PSFs between a dominant grass, Festuca rubra, and three other species from a species‐rich mountain grassland, taking advantage of the 18‐year field removal experiment. We tested whether such a long‐term presence/absence of Festuca can shape the feedback of the grassland community and whether these effects prevail in the lower soil layer, where Festuca roots are relatively more abundant, compared to the upper soil layer. We evaluated how experimentally induced soil legacies of Festuca in a pot experiment are modified by subsequently grown plants, both at the level of plant responses and changes in abiotic and biotic soil properties. At the level of the entire community, the soil legacies of the dominant Festuca were not detectable. However, the responses of the plants differed between the soil samples from the upper and lower soil layer. The pot experiment showed that the soil legacies of subsequently growing plants interact, influencing soil properties as well as plant responses to these altered soils. Generally, we found a stronger signal of the most recent conditioning, although the effect of the first conditioning plant was still detectable in many of the measured variables. Plant biomass in the feedback phase was mainly linked to the levels of plant‐available soil nitrogen, although it was also affected by the composition of microbial communities. Synthesis. We showed that plant‐induced soil legacies can be altered by legacies of co‐occurring species, complicating plant–soil feedbacks in diverse communities. Despite the detectable legacy effects on final plant biomass, in the short term, plant growth responds more strongly to the levels of available nutrients. We also highlight the vertical distribution of plant–soil feedbacks.

Effects of fragmentation, cadmium, and nutrients on the growth of a wetland invasive plant Alternanthera philoxeroides

AbstractFragmentation caused by disturbance is frequent in wetlands and usually co‐occurs with increases in cadmium and nutrient availability. However, whether fragmentation can interact with nutrients and heavy metals to affect wetland invasive plants has been little studied. We conducted a greenhouse experiment to test the effects of fragmentation (initial fragment was non‐severed, was severed into two fragments, and three fragments), cadmium (low, medium, and high), and nutrient availability level (high and low) on the growth of a widespread, invasive clonal plant Alternanthera philoxeroides (Mart.) Griseb. Clonal fragmentation reduced the total mass, stolon mass, root mass, and total stolon length of A. philoxeroides and altered the biomass allocation. Increases in cadmium adversely affected the growth of A. philoxeroides. The high level of cadmium increased leaf mass ratio but decreased stolon mass ratio. Response of leaf mass ratio to fragmentation varied at different cadmium or nutrient availability levels. Fragmentation, cadmium, and nutrients had a significant interaction on leaf mass ratio. Our results suggest that fragmentation can adversely affect the growth of A. philoxeroides. The adverse effect of fragmentation was greater at high nutrient levels and high cadmium levels (0.4 and 2 mg L−1).

Adaptation of VegSyst-DSS for macronutrient recommendations of fertigated, soil-grown, greenhouse vegetable crops

VegSyst model v3 was calibrated and validated to simulate daily and seasonal P, K, Ca and Mg uptake of soil-grown sweet pepper and muskmelon crops in greenhouses in SE Spain. The model adequately simulated P, K and Mg uptake in three validation crops of sweet pepper, and Ca uptake in one crop. P, K, Ca and Mg uptake were accurately simulated in one validation muskmelon crop. The decision support system VegSyst-DSS v2 was developed by adding a component for recommendations of P, K, Ca and Mg for pepper and muskmelon to VegSyst-DSS v1. The new DSS component, which combines with VegSyst model v3, calculates: (i) daily P, K, Ca and Mg requirement (in kg ha−1) and (ii) nutrient concentration recommendations for fertigation nutrient solution, considering soil available/exchangeable content and simulated crop uptake. Recommended concentrations of P, K, Ca and Mg (in mmol L−1) are calculated from simulated uptake of each nutrient and crop evapotranspiration (ETc). Scenario analyses were conducted for nutrient recommendations of representative cropping cycles of pepper and melon with hypothetical soils of relatively low, medium and high P, K, Ca and Mg availability, obtained from a local soil database. The scenario analyses showed most soils had ample available soil P, and required minimal applications of P. For soils with relatively high levels of available nutrients, DSS recommendations were much lower (20–60%) than farming practice. For soils with a medium supply of available nutrients, the DSS recommendations were generally approximately 60% of farmer practice, except for K in pepper and Ca in muskmelon. For soils that were relatively low in available nutrients, the recommendations were generally similar to or slightly less than farming practice. The crop and greenhouse specific recommendations of VegSyst-DSS v2 can appreciably reduce the application of P, K, Ca and Mg while meeting crop requirements.

Bacillus benefits the competitive growth of Ambrosia artemisiifolia by increasing available nutrient levels.

Bacillus can help plants to acquire nutrients either directly or indirectly. However, the role of Bacillus community on the competitive growth of invasive Ambrosia artemisiifolia is poorly understood. Native Setaria viridis is often found in areas that have been invaded by A. artemisiifolia. We sought to determine whether the quantitative and/or qualitative differences in the Bacillus community present on the invasive A. artemisiifolia and native S.viridis provide a competitive advantage to the invasive over native species. A field experiment was established to imitate the invasion of A. artemisiifolia. The 16S rRNA gene was commercially sequenced to identify the bacilli isolated from the rhizosphere soil of field-grown A. artemisiifolia and S. viridis. The Bacillus communities in their rhizosphere were compared, and their effects on the competitive growth of A. artemisiifolia and S. viridis were tested in the pot experiments. Bacillus in the rhizosphere soil of A. artemisiifolia significantly enhanced its intra-specific competitive ability. The relative abundance of B. megaterium in the rhizosphere soil of A. artemisiifolia was significantly higher than that of S. viridis. Inoculation with B. megaterium that was isolated from the rhizosphere soil of both A. artemisiifolia and S. viridis significantly enhanced the relative competitiveness of A. artemisiifolia and inhibited that of S. viridis. The higher abundance of B. megaterium in the rhizosphere of A. artemisiifolia creates higher levels of available nutrients than that in the native S. viridis, which enhance the competitive growth of A. artemisiifolia. The result helps to discover the mechanism of Bacillus community in the invasion of A. artemisiifolia.

Klasterisasi Wilayah Kabupaten Jember Berdasarkan Tingkat Ketahanan Pangan

Food security is a condition of food proclamation based on the availability of sufficient food to be able to live a healthy, active and productive life in a sustainable manner. Based on data from the Global Food Security Index (GFSI), Indonesia is ranked 69th with a level of food availability with a value of 63.7% and a level of ability or food needs of 74.9%. Jember Regency as one of the regencies in East Java Province based on TP2AK food security data in 2020 is in good condition (very resistant). However, in the same year Jember Regency experienced natural disasters with a total of 92 incidents The World Food Program in 2009 explained that one of the indicators of food security is vulnerability to food insecurity which is influenced by natural disasters. Based on the disaster conditions experienced by Jember Regency, the research carried out is to group food security areas in the Jember Regency area based on transient indicators using the KMeans method. The results of the analysis of the optimal SSE cluster formed in K4 (4 clusters) with an SSE value of 24,809. Each of the 4 clusters formed has a food security category of very resistant, resistant, moderately resistant, and somewhat vulnerable.

Pollinator-Mediated Selection on Floral Traits of Primula tibetica Differs Between Sites With Different Soil Water Contents and Among Different Levels of Nutrient Availability

Abiotic environmental factors are predicted to affect plant traits and the intensity of plant-pollinator interactions. However, knowledge of their potential effects on pollinator-mediated selection on floral traits is still limited. We separately estimated the effects of soil water (two sites with different soil water contents) and N-P-K nutrient availability (different levels of nutrient addition) on pollinator-mediated selection on floral traits of Primula tibetica (an insect-pollinated perennial herbaceous species). Our results demonstrated that floral traits, plant reproductive success and pollinator-mediated selection on floral traits varied between sites with different soil water contents and among different levels of nutrient addition. The strength of pollinator-mediated selection was stronger at the site with low soil water content than at the site with high soil water content, and first decreased and then increased with increasing N-P-K nutrient addition. Our results support the hypothesis that abiotic environmental factors influence the importance of pollinators in shaping floral evolution.

Herbivory may mediate the effects of nutrients on the dominance of alien plants

Abstract Numerous studies have highlighted the roles of nutrient availability and fluctuations therein for invasion success of alien plants. Many others also highlighted the role of herbivores in invasion success. However, how herbivory and the level and fluctuations in nutrient availability interact in driving alien plant invasion into native communities remains largely unexplored. We grew eight invasive alien species as target species in pot‐mesocosms with five different synthetic native communities in a three‐factorial design with two levels of nutrient availability (low vs. high), two levels of nutrient fluctuation (constant vs. pulsed) and two levels of above‐ground insect herbivory (with vs. without herbivores). As natural communities have both specialist and generalist herbivores, we simulated this using both a generalist and a specialist herbivorous grasshopper. The relative biomass production of the alien target plants to the total biomass production (i.e. alien biomass/total biomass) decreased in response to an increase in nutrient availability, but increased in response to the presence of herbivores. Furthermore, we found indications that the dominance of the alien target species may depend on interactions of herbivory with changes in nutrient availability and nutrient fluctuations, although these interactions were only marginally significant. Our multi‐trophic multi‐species experiment suggests that herbivory could mediate the interactive effect of nutrient enrichment and variability in nutrient supply on invasion of alien plants into native communities. Therefore, we recommend that studies testing the effects of resources on plant invasion should also consider interactive effects of other trophic levels. Read the free Plain Language Summary for this article on the Journal blog.

The effects of differing nutritional levels and body condition score on scrotal circumference, motility, and morphology of bovine sperm.

Bulls often experience various levels of nutrient availability throughout the year. Nutritional management is a critical factor on overall ejaculate composition and the ability to get females pregnant. We hypothesized that differing nutritional levels and body condition score (BCS) affect reproductive fertility parameters in bulls. Mature Angus bulls (n = 11) were individually housed and randomly assigned to one of two dietary regimens: 1) over-fed (n = 5) or 2) restricted (n = 6). Bulls were fed the same ration at different volumes to achieve desired effects resulting in eight individual treatments: gain to an over-fed body condition score ([BCS]; GO), gain after nutrient restriction (GR), loss after an over-fed BCS (LO), loss from nutrient restriction (LR), maintenance at ideal adiposity (BCS = 6) after overfeeding (IMO), maintenance at ideal adiposity after nutrient restriction (IMR), maintenance at an over-fed BCS (BCS = 8; MO), and maintenance at a restricted BCS (BCS = 4; MR). Body weight (BW) and BCS were recorded every 2 wk to monitor bull weight and BCS changes. Scrotal circumference was measured every 28 d. Body fat and sperm motility and morphology were evaluated every 84 d. Scrotal circumference, motility, and morphology were normalized to the initial value of each bull. Thus, allowing the individual bull to serve as a control. Statistical analyses were conducted with PROC GLIMMIX of SAS as a complete randomized design to determine if treatment influenced BW, BCS, scrotal circumference, motility, morphology, and adipose thickness. Scrotal circumference (P < 0.001) had the least amount of deviation from initial during the LR (0.29 ± 0.44) treatment and the greatest during the MO (3.06 ± 0.44), LO (2.28 ± 0.44), MR (2.43 ± 0.44), GR (3.03 ± 0.44), and IMR (2.91 ± 0.44) treatments. Sperm motility was not affected by nutritional treatments (P = 0.55). Both head and total defects of sperm differed (P = 0.02) due to nutritional treatments. Increased head abnormalities occurred during the LO (37.60 ± 8.61) treatment, with no differences between the other treatments. Total defects increased during the LO (43.80 ± 9.55) treatment with similar increases in bulls during the GR (29.40 ± 9.55) and IMR (35.60 ± 9.55) treatments. In conclusion, male fertility was impacted when a deviation from a BCS of 6 occurred which could be detrimental to reproductive and beef production efficiency.