Competition Ratio Research Articles

Effect of Maize (Zeal mays) and Soybean (Glycine max) Intercropping on Yield and Root Development in Xinjiang, China

Intercropping is a breakthrough in land-use optimization. This work aimed to study the effects of intercropping patterns on the growth, yield, root morphological characteristics, and interspecific competition of maize and soybean, as well as provide a reference for the development of intercropping patterns of maize and soybean in Northwest China. Three different cropping patterns were designed: monocropping maize, monocropping soybean, and maize-soybean intercropping. Agronomic traits, intercropping indicators such as land equivalent ratio (LER), aggressivity (A), competition ratio (CR), and actual yield loss (AYL), as well as root morphological characteristics were assessed. The results showed that, compared with monocropping, the intercropping maize plant height increased by 6.07–8.40%, and the intercropping soybean plant height increased by 35.27–38.94%; the root length density (RLD) of intercropping maize was higher than that of monocropping maize, the RLD of intercropping soybean was lower than that of monocropping soybean, in the 0–40 cm soil layer the intercropping increased maize RLD by 1.79–7.44% while the soybean RLD was reduced by 3.06–9.46%; the aggressivity of maize was greater than 0 and the competition ratio was greater than 1, which was the dominant species; the maize/soybean land equivalent ratio was 1.18–1.26, which improved the land utilization rate. Therefore, the effect of increasing yield can be achieved by changing the maize and soybean planting method, which is beneficial to the ecological strategy of sustainable development in the northwest region.

Mating competition and adult sex ratio in wild Trinidadian guppies

AbstractMost experimental tests of mating systems theory have been conducted in the laboratory, using operational sex ratios (ratio of ready-to-mate male to ready-to-mate female) that are often not representative of natural conditions. Here, we first measured the range of adult sex ratio (proportion of adult males to adult females; ASR) in two populations of Trinidadian guppies (Poecilia reticulata) differing in ambient predation risk (high vs. low). We then explored, under semi-wild conditions, the effect of ASR (i.e., 0.17, 0.50, 0.83) on mating competition patterns in these populations. ASR in the wild was female-biased and did not significantly differ between the two populations. The range of ASR in our experiment was representative of natural ASRs. As expected, we observed an increase in intrasexual aggression rates in both sexes as the relative abundance of competitors increased. In support of the risky competition hypothesis, all measured behaviors had lower rates in a high versus low predation-risk population, likely due to the costs of predation. In terms of mating tactics, a male-biased ASR did not lead males to favor forced mating over courtship, indicating that males did not compensate for the cost of competition by switching to a less costly alternative mating tactic. Overall, this study highlights the need for field experiments using natural ranges of ASRs to test the validity of mating systems theory in a more complex, ecologically relevant context.

Evaluate the sustainable marketing strategy to optimal online leasing of new energy vehicles under the background big data economy

PurposeUnder the big data background, there are many influencing factors for investors of new energy vehicles (NEV), and government subsidies promote the sustainable development of the new energy vehicle industry. Therefore, the purpose of the study is to provide solutions for the sustainable development of NEV.Design/methodology/approachThe sustainable marketing strategy of NEV in China is put forward. This paper first analyzes the subsidy policy effect of NEV under the background of big data. It then establishes the online optimal leasing strategy under multiple strategy choices and the online leasing strategy of multiple vehicles under the inflation market.FindingsWith the fixed cost of NEV in each lease period, the optimal competition ratio of online decision-makers will continue to decrease with the increase of the difference between prepaid funds and government subsidies. In the decision-making of renting and purchasing multiple vehicles, the general strategy competition ratio is 2.922, while the optimal competition ratio of the online renting and purchasing strategy proposed by the research is 2.723.Research limitations/implicationsThe research is limited by the limited data and information collected, so the optimal decision-making model has some limitations. The authors need to find more representative data to optimize the model.Practical implicationsAs an emerging industry, NEV have developed rapidly in recent years. Based on the online algorithm and competitive ratio theory, this paper solves the decision-making problem of operators and gives the optimal strategy to promote the green development of the new energy vehicle industry.Originality/valueThis paper proposes the optimal strategy for online investors of new energy vehicle operators by combining online algorithm and competitive ratio theory. The numerical analysis results of the optimal online model under multi strategy selection show that with the same difference between prepaid funds and government subsidies, the time point will be delayed and the time point will be advanced as the cost of leasing NEV in each period increases.

Evaluation of Yield and Competition Indices for Intercropped Indigofera (Indigofera zollingeriana) and Brahum (Brachiaria humidicola) Underneath Mature Coconuts

Blended societies can increment plant development and surrender through proficient utilize of assets. The reason of this consider was to decide the range comparable proportion of the secured crops leguminosae Indigofera zollingeriana (Iz) and the tropical grass Brachiaria humicola (Bh) in coconut ranches. The reason of this think about was to survey the arrive comparable proportion of this secured edit based on abdicate and bearing capacity on the coconut ranch. This test was performed employing a completely randomized plan with a combination of four medications of planted region as takes after: Iz planted range with 1.0 m x1.0 m and 1.0 m x1.5 m, and Bh planted zone with 0.5 m x 0.25 m, 0.5 m x 0.5 m. We analyzed the information utilizing ANOVA and HSD test. The factors measured were the potential surrender, carrying capacity and competition records based on dry matter surrender. The comes about appeared that the medicines contrasted essentially (P <0.01) with regard to the potential surrender, carrying capacity, land equivalent ratio and competition ratio. It can be concluded that Iz covered crops with a planted area of 1.0 m x 1.5 m and Bh with a planting area of 0.5 m x 0.25 m have the most appropriate yield and competitive indices.

Evaluation of pigeon-pea based intercropping systems under irrigated conditions in coastal Odisha

The field experiment conducted for over two years (2016-17 and 2017-18) at the Centre for Pulses Research (OUAT), Berhampur-761001, under irrigated rabi conditions in coastal Odisha testing six intercropping combinations of pigeon pea (cv. manak) with three vegetables (yam bean (safed hyb. sakalu), french bean (falguni latika) and cowpea (kashi kanchan) in two proportions (1:1; 2:2) and 4 sole crops, revealed that intercropping combinations recorded higher pigeon pea seed equivalent yield than the respective sole crops. Performance of paired row sowing was found superior with 38.24 g ha-1 of pigeon pea seed equivalent yield than with single row intercropping (32.71 q ha-1). Among the three intercrops, the french bean system was found most remunerative with 41.13 q ha-1 pigeon pea seed equivalent yield followed by yam bean (37.84 q ha-1), but superior to cowpea systems (27.46 q ha-1). Maximum pigeon pea seed equivalent yield (44.09 q ha-1), net return (Rs. 2,31,473/-) and B:C ratio (3.99) were recorded with pigeon pea: french bean =2:2 proportion. This system also registered maximum land equivalent ratio (1.62), monetary advantage index (Rs. 74,176 ha-1) and system relative crowding coefficient (9.86). Aggressivity and competition ratio indicated that french bean and cowpea were dominant on pigeon pea.

Engineered dissipation induced entanglement transition in quantum spin chains: From logarithmic growth to area law

Recent theoretical work has shown that the competition between coherent unitary dynamics and stochastic measurements, performed by the environment, along wavefunction trajectories can give rise to transitions in the entanglement scaling. In this work, complementary to these previous studies, we analyze a situation where the role of Hamiltonian and dissipative dynamics is reversed. We consider an engineered dissipation, which stabilizes an entangled phase of a quantum spin$-1/2$ chain, while competing single-particle or interacting Hamiltonian dynamics induce a disentangled phase. Focusing on the single-particle unitary dynamics, we find that the system undergoes an entanglement transition from a logarithmic growth to an area law when the competition ratio between the unitary evolution and the non-unitary dynamics increases. We evidence that the transition manifests itself in state-dependent observables at a finite competition ratio for Hamiltonian and measurement dynamics. On the other hand, it is absent in trajectory-averaged steady-state dynamics, governed by a Lindblad master equation: although purely dissipative dynamics stabilizes an entangled state, for any non-vanishing Hamiltonian contribution the system ends up irremediably in a disordered phase. In addition, a single trajectory analysis reveals that the distribution of the entanglement entropy constitutes an efficient indicator of the transition. Complementarily, we explore the competition of the dissipation with coherent dynamics generated by an interacting Hamiltonian, and demonstrate that the entanglement transition also occurs in this second model. Our results suggest that this type of transition takes place for a broader class of Hamiltonians, underlining its robustness in monitored open quantum many-body systems.

Performance of Different Groundnut (Arachis hypogaea L.) based Intercropping Systems with Millets under Rainfed Condition of Odisha

Background: Groundnut as a sole crop is affected by adverse weather conditions coupled with damage by insect, pest and disease, results in economic losses and in extreme cases complete failure of the crop. Intercropping is one of the important cropping systems recommended to mitigate the aberrant climatic conditions with an aim to increase total productivity per unit area. The present study was done to assess the effect of different millet based intercropping system on growth and yield of groundnut under rainfed condition. Methods: A field experiment was conducted during kharif 2018 and 2019 at Agricultural Research Farm of All India Coordinated Research Project on Groundnut, OUAT, Bhubaneswar on mixed red and black medium soil. The experiment was laid out in randomized complete block design and replicated thrice. It consisted of ten treatments comprising of groundnut with three millets viz., finger millet, little millet and foxtail millet. Millets were intercropped with groundnut in the replacement series of 4:2 and 2:1 row proportion along with mono-cropped millets and groundnut. Result: Significantly higher no. branches/plant (5.2), leaflet/no. plant (79.33) and dry matter accumulation (25.77g/plant) was recorded in groundnut + finger millet (2:1) whereas, sole groundnut incurred significantly higher pod no/plant (16.5), 100 kernel weight (37.2g), shelling% (77.8), pod yield (1736 kg/ha) and haulm yield (3613 kg/ha) over all other intercropping systems. Further, groundnut pod equivalent yield (GPEY), land equivalent ratio (LER), area time equivalent ratio (ATER) and economics were higher in 2:1 row ratio of groundnut + finger millet compared to any of the sole and intercropping systems. The competition ratio and aggressivity of little millet was greater than that of other millets. So, it was most dominant crop over groundnut compared to other millets in the intercropping systems.

SP2.1.17Prognostic significance of competition ratios in surgical specialty training selection

Abstract Aims A Competition Ratio (CR) indicates the ratio of total applications for a training post when compared with numbers of specialty posts available. This study aimed to evaluate CRs’ influence on National Training Number (NTN) selection in a single UK Statutory Education Body. Methods Consecutive Core Surgical Trainees numbering 154 (median years since graduation: four, 105 male, 49 female) were studied over a six-year period. Annual specialty specific CRs were obtained from Health Education England’s website, and primary outcome measure was UK National Training Number (NTN) appointment. Results Overall NTN appointment was 45.5%. Median CR was 2.36; range OMFS 0.70 (2020) to Neurosurgery 22.0 (2020). Multivariable analysis revealed that NTN success was associated with: CR (OR 0.46, p = 0.003), a single scientific publication (OR 6.25, p = 0.001), cohort year (2019, OR 12.65, p = 0.003), and Universal ARCP Outcome 1 (OR 45.24, p < 0.001). CRs predicted NTN appointment with a Youden index defined critical ratio of 4.42; 28.6% (n = 8) vs. 49.2% (n = 62), p = 0.018. Conclusions CRs displayed 30-fold variation, with CRs below 4.42 associated with two-fold better NTN promotion, but strong clinical competence and academic reach again emerged as the principal drivers of career advancement.

TP8.2.13 Impact of peer-delivered tuition/feedback on appointment to UK Higher Surgical Training

Abstract Aims In the UK, Core Surgical Trainees (or equivalent) undergo a rigorous National Selection (NS) process to secure a ST3 Training Post in General/Vascular Surgery. Despite decrease in competition ratio from 3:1 in 2012 to 1.48:1 in 2017, many applicants were unable to secure ST3 Training Posts. We hypothesise this is due to applicant performance anxiety rather than lack of clinical experience. We designed a 2-day structured course to address the applicant’s confidence levels in preparing for NS. Methods This is a prospective observational study following 27 delegates who completed a 2-day course delivered by surgical consultants and trainees; consisting of didactic lectures and interactive practice with a 1:1 faculty:delegate ratio. A specific mentor was nominated to oversee the delegate’s progress throughout and post course. Personalised feedback was given by the entire faculty throughout the course. Delegates were asked to complete evaluation forms to track their perceived confidence levels of success at NS at different timeframes, measured by a visual analogue scale. Paired t -test was performed to compare the mean confidence level pre- and post- course. Results Evaluation forms were received from all (n = 27) delegates. Self-reported confidence increased significantly for all domains except Professional Communication. 23 (85%) participants were successful at interviews post course. There was no statistically significant difference between UK and non-UK graduates, first time and not-first-time applicants. Conclusions Peer-delivered teaching, practice and feedback as a structured interview practice course significantly improves applicants’ confidence levels which translates to higher success rate at National Selection.

Effects of interspecific competition on crop yield and nitrogen utilisation in maize-soybean intercropping system

Intercropping system plays a crucial role in improving crop yield, nitrogen utilisation efficiency (NUE) and economic benefit. The difference in crop yield and interspecific relationship under different bandwidth and row ratio allocation patterns are still unclear. A field experiment was carried out to explore change regularities between crop yield and interspecific relationships under maize soybean intercropping with different bandwidths and row ratios. The results showed that the yield of intercropped crops was lower than that of the sole crop. The nitrogen accumulation (NA), NUE and nitrogen competition ratio was the highest under the intercropping mode with a bandwidth of 2.0 m, which indicated that this mode was more conducive to the N uptake and utilisation in crops. In all intercropping systems, nitrogen equivalent ratio (NER) and land equivalent ratio (LER) were all greater than one, indicating that intercropping systems were conducive to improving land utilisation efficiency and NUE. Under the same bandwidth pattern, expanding the maize soybean row ratio from 2 : 4 to 3 : 4 was beneficial to the improvement of LER, NER, NUE, crop group yield. In conclusion, it was preferable in the NA, NUE, crop group yield under the system of bandwidth 2.0 m and row ratio 2 : 2, which could be a reference for maize soybean intercropping system.

Prognostic significance of competition ratios in surgical specialty training selection

BackgroundA competition ratio (CR) indicates the ratio of total applications for a training post when compared with numbers of specialty posts available. This study aimed to evaluate CRs’ influence on...

Invasive plant benefits a native plant through plant-soil feedback but remains the superior competitor

Plant soil feedback (PSF) occurs when a plant modifies soil biotic properties and those changes in turn influence plant growth, survival or reproduction. These feedback effects are not well understood as mechanisms for invasive plant species. Eragrostis lehmanniana is an invasive species that has extensively colonized the southwest US. To address how PSFs may affect E. lehmanniana invasion and native Bouteloua gracilis growth, soil inoculant from four sites of known invasion age at the Appleton-Whittell Audubon Research Ranch in Sonoita, AZ were used in a PSF greenhouse study, incorporating a replacement series design. The purpose of this research was to evaluate PSF conspecific and heterospecific effects and competition outcomes between the invasive E. lehmanniana and a native forage grass, Bouteloua gracilis. Eragrostis lehmannianaPSFs were beneficial to B. gracilis if developed in previously invaded soil. Plant-soil feedback contributed to competitive suppression of B. gracilis only in the highest ratio of E. lehmanniana to B. gracilis. Plant-soil feedback did not provide an advantage to E. lehmanniana in competitive interactions with B. gracilis at low competition levels but were advantageous to E. lehmanniana at the highest competition ratio, indicating a possible density-dependent effect. Despite being beneficial to B. gracilis under many conditions, E. lehmanniana was the superior competitor.

Influence of irrigation regimes on competition indexes of winter and summer intercropping system under semi-arid regions of Pakistan

An assessment of the competitive indexes in intercropping of different winter and summer based intercropping systems were studied, with the aim of increasing the productivity of these crops. Four winter crops, wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), fababean (Vicia faba) and rapeseed (Brassica napus) and four summer crops, sorghum (Sorghum bicolor L.), pearl millet (Pennisetum typhoidum L.), pigeonpea (Cajanus cajan L.) and mungbean (Vigna radiate L.) were grown under two irrigation regimes with the pattern of two crops in each intercropping system, at Agronomy Research Farm, The University of Agriculture, Peshawar, Pakistan in both winter and summer season during 2015–16 to 2016–17. The results showed that higher grain yield (kg ha−1) were recorded under sole cropping than intercropping. Higher grain yield was recorded in sole cropping, for all four crops. All crops grown in intercropping produced comparatively higher grains head−1 and seeds pod−1 than sole crop except pigeonpea. Intercropping systems were performed different in term of competition indexes which determined land utilization efficiency. Competition indexes revealed that in winter season wheat intercropped with fababean showed highest advantages of intercropping in term of land equivalent ratio (30%), relative crowding co-efficient (60%), actual yield loss (60%), area time equivalent ratio (27%), land utilization efficiency (83%), intercropping advantages (1060), monetary advantage index (Pakistani rupees (PKR) 46456) and system productivity index (3684) while in summer sorghum/pearl millet intercropped with pigeonpea was the most dominant intercropping systems in term of relative crowding co-Efficient (40%), actual yield loss (50%), land utilization efficiency (60%) intercropping advantages (1150) and system productivity index (1914). Aggressivity and competition ratio showed that cereals especially barley in winter and sorghum in summer season was highly competitive crops in the intercropping system. Most of the competition indexes values were higher for winter crops under limited irrigated condition while in case of summer crops intercropping indexes were higher under full irrigated condition. It was concluded that wheat intercropped with fababean, and sorghum/millet intercropped with mung bean was the most successful intercropping systems in winter and summer seasons, respectively under both irrigation regimes, for the semiarid region of Pakistan.

Common vetch cultivars improve yield of oat row intercropping on the Qinghai-Tibetan plateau by optimizing photosynthetic performance

Sustainable development of livestock production is challenged by the shortage of forage resources on the Qinghai-Tibetan plateau (QTP). Common vetch-oat intercropping is used on the QTP and in other alpine regions to obtain substantial forage yield, but few common vetch cultivars have been evaluated in intercropping systems. A three-year field experiment in the eastern QTP was carried out to compare plant growth, photosynthetic rate (Pn), radiation use efficiency (RUE), aboveground biomass, land equivalent ratio (LER), and competition ratio of oat row intercropping with three new common vetch cultivars (Lanjian No. 1, Lanjian No. 2, Lanjian No. 3) under low-input conditions. Compared to sole cropping at seed densities of 141 and 667 plants m–2, for common vetches and oats, respectively, alternate row intercropping with each species at half these densities significantly increased the Pn (by 15–19%) of oat, and reduced the Pn (by 12–26%) of common vetch. Moreover, row intercropping significantly increased intercepted photosynthetically active radiation and RUE (by 44%) for oat but significantly decreased these for common vetch (by 34%). Among common vetch cultivars, at both flowering and maturity stages, Lanjian No. 2 (1.21, 1.15) and Lanjian No. 3 (1.27, 1.21) had greater LER than the later-maturing Lanjian No. 1 (1.07, 1.01) when intercropped. Oat row intercropping with Lanjian No. 2 and Lanjian No. 3 increased forage production compared to sole cropping oat or common vetch on the QTP. These findings provide scientific support for common vetch-oat intercropping as a sustainable approach to increasing forage production from cropland in alpine regions.

Sexual size dimorphism and sexual selection in primates

Abstract In most animals, females are larger than males. Paradoxically, sexual size dimorphism is biased towards males in most mammalian species. An accepted explanation is that sexual dimorphism in mammals evolved by intramale sexual selection. I tested this hypothesis in primates, by relating sexual size dimorphism to seven proxies of sexual selection intensity: operational sex ratio, mating system, intermale competition, group sex ratio, group size, maximum mating percentage (percentage of observed copulations involving the most successful male), and total paternity (a genetic estimate of the percentage of young sired by the most successful male). I fitted phylogenetic generalised least squares models using sexual size dimorphism as the dependent variable and each of the seven measures of intensity of sexual selection as independent variables. I conducted this comparative analysis with data from 50 extant species of primates, including Homo sapiens, Pan troglodytes, and Gorilla spp. Sexual dimorphism was positively related to the four measures of female monopolisation (operational sex ratio, mating system, intermale competition, and group sex ratio) and in some cases to group size, but was not associated with maximum mating percentage or total paternity. Additional regression analyses indicated that maximum mating percentage and total paternity were negatively associated with group size. These results are predicted by reproductive skew theory: in large groups, males can lose control of the sexual behaviour of the other members of the group or can concede reproductive opportunities to others. The results are also consistent with the evolution of sexual size dimorphism before polygyny, due to the effects of natural, rather than sexual, selection. In birds, the study of molecular paternity showed that variance in male reproductive success is much higher than expected by behaviour. In mammals, recent studies have begun to show the opposite trend, i.e. that intensity of sexual selection is lower than expected by polygyny. Results of this comparative analysis of sexual size dimorphism and sexual selection intensity in primates suggest that the use of intramale sexual selection theory to explain the evolution of polygyny and sexual dimorphism in mammals should be reviewed, and that natural selection should be considered alongside sexual selection as an evolutionary driver of sexual size dimorphism and polygyny in mammals.

Optimum strip width increases dry matter, nutrient accumulation, and seed yield of intercrops under the relay intercropping system

AbstractStrip width management is a critical factor for producing higher crop yields in relay intercropping systems. A 2‐year field experiment was carried out during 2012 and 2013 to evaluate the effects of different strip width treatments on dry‐matter production, major‐nutrient (nitrogen, phosphorus, and potassium) uptake, and competition parameters of soybean and maize in relay intercropping system. The strip width (SW) treatments were 0.40, 0.40, and 0.40 m (SW1); 0.40, 0.40, and 0.50 m (SW2); 0.40, 0.40, and 0.60 m (SW3); and 0.40, 0.40, and 0.70 m (SW4) for soybean row spacing, maize row spacing, and spacing between soybean and maize rows, respectively. As compared to sole maize (SM) and sole soybean (SS), relay‐intercropped maize and soybean accumulated lower quantities of nitrogen, phosphorus, and potassium in all treatments. However, maize in SW1 accumulated higher nitrogen, phosphorus, and potassium than SW4 (9%, 9%, and 8% for nitrogen, phosphorus, and potassium, respectively). Soybean in SW3 accumulated 25% higher nitrogen, 33% higher phosphorus, and 24% higher potassium than in SW1. The improved nutrient accumulation in SW3 significantly increased the soybean dry matter by 19%, but slightly decreased the maize dry matter by 6% compared to SW1. Similarly, SW3 increased the competition ratio value of soybean (by 151%), but it reduced the competition ratio value of maize (by 171%) compared to SW1. On average, in SW3, relay‐cropped soybean produced 84% of SS seed yield and maize produced 98% of SM seed yield and achieved the land equivalent ratio of 1.8, demonstrating the highest level in the world. Overall, these results suggested that by selecting the appropriate strip width (SW3; 0.40 m for soybean row spacing, 0.40 m maize row spacing, and 0.60 m spacing between soybean and maize rows), we can increase the nutrient uptake (especially nitrogen, phosphorus, and potassium), dry‐matter accumulation, and seed yields of relay‐intercrop species under relay intercropping systems.

Assessment of competitive indices in intercropping system of brinjal and palak

An assessment of the competitive indices in intercropping between brinjal and palak was carried out with the aim of increasing the productivity of these crops as well as to achieve the optimum utilization of all the available resources. For this purpose, an experiment consisting of 11 treatments with three replications in a Randomized Block Design (RBD) was conducted at Research Farm of the Department of Vegetable Science, CCS Haryana Agricultural University, Hisar during autumn-winter season of 2016-17. Intercropping systems were assessed by land equivalent ratio (LER), areatime equivalent ratio (ATER), relative crowding coefficient (K), aggressivity (A), competition ratio (CR), actual yield loss (AYL) and intercropping advantage (IA). Competition indices like CEY, LER, ATER and K were found to be superior for the paired row brinjal + palak (two rows). Although, the treatment brinjal + palak (three rows) was found better in terms of indices like A, CR, AYL and IA. This might be due to the interspecific and intraspecific competition between brinjal and palak for space, nutrients, light and availabl resources. LER, ATER and K values were greater than 1 for all the intercropping treatments. These findings showed a advantage of intercropping for exploiting the resources of the environment optimally.

Enhancement of nutrient absorption and interspecific nitrogen transfer in a Eucalyptus urophylla × eucalyptus grandis and Dalbergia odorifera mixed plantation

There is substantial evidence that legume-derived nitrogen (N) is transferred to neighboring nonlegumes in herbaceous mixtures and intercropping systems. However, considering that woody species are key sources and major consumers N, information regarding whether N transfer from leguminous to nonleguminous woody species in mixed plantations was detected. To detect N transfer in a Eucalyptus urophylla × Eucalyptus (E.) grandis and Dalbergia odorifera mixed system, two pot experiments were set up, one with 15N dilution and the other with 15N leaf labeling of Dalbergia odorifera. Seedlings were fertilized with CO (15NH2)2 urea, and the effects on interspecific N transfer and biological N fixation (BNF) efficiency were observed. Results showed that: (1) The values of competition ratio of Eucalyptus urophylla × E. grandis to Dalbergia odorifera (CRED) greater than one indicate that Eucalyptus urophylla × E. grandis was a stronger competitor and had the absolute advantage over Dalbergia odorifera, N application significantly increased the competition ratio of Eucalyptus urophylla × E. grandis to Dalbergia odorifera. An increase in the dry matter yields of Eucalyptus urophylla × E. grandis was observed in the NB treatment (20.36–33.16%), but the dry matter yields of Dalbergia odorifera decreased by 10.02–19.57%. (2) N was transferred from Dalbergia odorifera to Eucalyptus urophylla × E. grandis at rates of 9.60% and 6.50% in the 3 and 6 g pot−1 urea treatments with isotope dilution markers, respectively. N transfer rates of 13.66% and 7.88% were observed in the NB and MB treatments with 15N leaf labeling. (3) Interspecific root interaction increased N use efficiency and increased N2 fixation by Dalbergia odorifera; N fixation increased by 8.51% and 4.34% at the N1 and N2 levels under the NB treatment. The biomass and N use efficiency of Eucalyptus urophylla × E. grandis and Dalbergia odorifera has grown together were effectively improved compared to those of monocultures. The mechanism for our results may depend on interspecific N transfer, i.e., N transfer from Dalbergia odorifera to Eucalyptus urophylla × E. grandis, the stimulation of Dalbergia odorifera BNF and its increased use of atmospheric N sources may improve the exploitation of mixed plantations.

Narrow‐wide‐row planting pattern increases the radiation use efficiency and seed yield of intercrop species in relay‐intercropping system

AbstractPlanting arrangements affect radiation use efficiency (RUE) and competitiveness of intercrop species in intercropping systems. Here, we reveal that narrow‐wide‐row planting arrangement in maize‐soybean relay‐intercropping system increases the dry matter and competitiveness of soybean, increased the RUE of maize and soybean, and compensates the yield loss of maize by substantially increasing the yield of soybean. In this field study, maize was planted with soybean in different planting arrangements (P1, 20:180, P2, 40:160; P3, 60:140, and P4, 80:120) of relay intercropping, all the relay‐intercropping treatments were compared with sole crops of maize (SM) and soybean (SS). Results showed that P1 improved the total RUE 3.26 g/MJ (maize RUE + soybean RUE) of maize and soybean in relay‐intercropping system. Compared to P4, treatment P1 increased the soybean competition ratio (CR) values (by 55%) but reduced the maize CR values (by 29%), which in turn significantly improved the yield of soybean by maintaining the maize yield. Generally, in P1, soybean produced 82% of SS yield, and maize produced 88% of SM yield, and it achieved the land equivalent ratio of 1.7. These results suggest that by maintaining the appropriate planting distances between maize and soybean we can improve the competitiveness and yield of intercrop species in relay‐intercropping system.

How self-regulation, the storage effect, and their interaction contribute to coexistence in stochastic and seasonal environments

Explaining coexistence in species-rich communities of primary producers remains a challenge for ecologists because of their likely competition for shared resources. Following Hutchinson's seminal suggestion, many theoreticians have tried to create diversity through a fluctuating environment, which impairs or slows down competitive exclusion. However, fluctuating-environment models often only produce a dozen of coexisting species at best. Here, we investigate how to create richer communities in fluctuating environments, using an empirically parameterized model. Building on the forced Lotka-Volterra model of Scranton and Vasseur (Theor Ecol 9(3):353-363, 2016), inspired by phytoplankton communities, we have investigated the effect of two coexistence mechanisms, namely the storage effect and higher intra- than interspecific competition strengths (i.e., strong self-regulation). We tuned the intra/inter competition ratio based on empirical analyses, in which self-regulation dominates interspecific interactions. Although a strong self-regulation maintained more species (50%) than the storage effect (25%), we show that none of the two coexistence mechanisms considered could ensure the coexistence of all species alone. Realistic seasonal environments only aggravated that picture, as they decreased persistence relative to a random environment. However, strong self-regulation and the storage effect combined superadditively so that all species could persist with both mechanisms at work. Our results suggest that combining different coexistence mechanisms into community models might be more fruitful than trying to find which mechanism best explains diversity. We additionally highlight that while biomass-trait distributions provide some clues regarding coexistence mechanisms, they cannot indicate unequivocally which mechanisms are at play.