Early Stages Of Establishment Research Articles

Evaluation of critical weed-free period for three sweetpotato (Ipomoea batatas) cultivars

Abstract Sweetpotato [Ipomoea batatas (L.) Lam.] is a staple crop that provides nutritional benefits to humans globally, but it is subject to yield loss when competing with weeds, especially during the early stage of establishment. Yield loss can vary widely based on the cultivar, production environment, weed species, and management techniques. To address this challenge, we conducted field research at the Samuel G. Meigs Horticulture Research Farm, Lafayette, IN, and at the Southwest Purdue Agricultural Center, Vincennes, IN, in 2022 to determine the effect of sweetpotato cultivar on the critical weed-free period. The experiment was a split-plot design, with weed-free interval treatments as the main plot factor and cultivar as the subplot factor. The three cultivars used were ‘Covington’, ‘Monaco’, and ‘Murasaki’. Weeds were removed by hand and allowed to establish and compete with the crop beginning at 0, 14, 21, 28, 35, or 42 d after transplanting (DAP). As the weed-free interval increased from 0 to 42 DAP, predicted total yield increased from 19 kg ha−1 to 20,540 kg ha−1 for Covington, 3 kg ha−1 to 11,407 kg ha−1 for Monaco, and 125 kg ha−1 to 13,460 kg ha−1 for Murasaki at the Lafayette location. At Vincennes, as the weed-free interval increased from 0 to 42 DAP, predicted total yield increased from 14,664 kg ha−1 to 33,905 kg ha−1 for Covington, 4,817 kg ha−1 to 18,059 kg ha−1 for Monaco, and 12,735 kg ha−1 to 21,105 kg ha−1 for Murasaki. A threshold of ≤10% total yield reduction was achieved by maintaining sweetpotatoes weed-free 24 DAP for Covington, 20 DAP for Murasaki, and 33 DAP for Monaco.

Establishment of warm‐season turfgrasses in a Mediterranean transition zone under simulated waterlogging

AbstractThe Mediterranean region is expected to experience increased extreme precipitation events with the risk of inland flooding because of climate change. This may adversely affect the establishment of warm‐season turf species, usually selected for low water consumption. A simulated waterlogging experiment was conducted at the University of Padua in northeastern Italy during the summers of 2017 and 2018. Four bermudagrass (Cynodon spp.) cultivars (La Paloma, Transcontinental, SR 9554, and Jackpot), ‘Pure Dynasty’ seashore paspalum (Paspalum vaginatum Swartz), and ‘SWI 2000’ buffalograss [Buchloë dactyloides (Nutt.) Engelm.] were compared under waterlogging conditions. The response of the three warm‐season species to four waterlogging events during establishment at two different seeding rates was investigated. The number of seedlings, percentage green coverage, and NDVI were measured. At the end of the experimental periods, the dry weights of the above‐ground biomass and roots were also determined. All the cultivars tested demonstrated high tolerance to waterlogging in the early stages of establishment. Moreover, they produced a significantly higher number of seedlings per unit area when sown at the higher seeding rate.

Bats are sentinels for invasive pest surveillance based on DNA metabarcoding

Loss of crop yield due to non-native invasive pests is a global phenomenon with profound population, biodiversity, ecosystem, and economic impacts. The polyphagous and migratory fall armyworm (FAW) Spodoptera frugiperda (Lepidoptera, Noctuidae) has become a major invasive pest around the globe in the past decade, posing a great threat to global food security. Early warning and timely detection of this pest and its associated agricultural risks are essential for preventing, intervening, controlling, and mitigating invasion threats, which could reduce crop losses and economic damage. However, one key challenge is how to effectively and accurately monitor pest invasion as soon as possible prior to their establishment. Here, we aimed to determine the effectiveness of four different methods for identifying the presence of FAW, namely DNA metabarcoding, field survey, light trap, and sex pheromone trap. We collected fecal samples of six bat species in the FAW colonization area, including Rhinolophus pearsonii, Rhinolophus rex, Ia io, Myotis altarium, Myotis pilosus, and Myotis chinensis. We then utilized bat fecal samples to monitor FAW through DNA metabarcoding during its early establishment stages and compared this approach to three traditional surveillance methods. The results revealed interspecific differences in the occurrence frequency of FAW in different bat species. Furthermore, bat fecal DNA metabarcoding successfully monitored the occurrence of this pest nearly one month in advance compared with traditional approaches, which coincides with the adult migration time of larval counterparts found in the field based on effective accumulated temperature calculations. Our results showed that DNA metabarcoding dietary analysis of generalist insectivorous bats can be an effective, noninvasive, and economically viable tool for invasion pests monitoring to inform management decisions.

Native species can reduce the establishment of invasive alien species if sown in high density and using competitive species

Invasion of alien species is one of the main drivers of land degradation threatening both natural and managed ecosystems. Ecological restoration is crucial in controlling invasion to improve biotic resistance and avoid further land degradation. We investigated the possibility of controlling the establishment of invasive alien species (IAS) by native seed addition. We tested if trait similarity or increased propagule pressure of native species results in the suppression of IAS at the early stage of development. We set up a sowing experiment with three widespread IAS in Hungary of different life forms and functional groups (Asclepias syriaca, Conyza canadensis, Tragus racemosus) and four Pannonic sand grassland species (Festuca vaginata, Galium verum, Gypsophila paniculata, Saponaria officinalis). We found no significant differences in germination ability and seedling emergence between native species and IAS, despite the differences in thousand‐seed weight. Using univariate general linear models, we found that the seedling establishment of IAS can be reduced by adding native species at high densities but also depending on the species identity. Instead of species of similar traits, the seeding of a competitor perennial grass of sand grasslands (F. vaginata) reduced the seedling emergence of all studied IAS the most. Our results confirm that IAS can be effectively controlled by native seed addition in the early establishment stage, especially applying higher densities and competitive species. We conclude that invasion‐resistant restoration can be achieved by the combination of several factors, including high‐density sowing of native species that match IAS in the early stage of development.

Ladybird communities in rural woodlands: Does an invader dominate?

The invasive alien species Harmonia axyridis (Coleoptera: Coccinellidae) was first observed in the UK in 2004. Previous studies have demonstrated the adverse effects on other species of H. axyridis during its early stages of establishment. However, habitat factors are important in determining distribution and population trends of ladybirds. Whilst the abundance of H. axyridis is well known in the UK within urban and other managed habitats, much less is known about its abundance in the wider countryside. Here we present the results of surveys from rural woodland habitats to assess whether or not H. axyridis dominates coccinellid communities in these rural habitats. Additionally, we explored the relationship between coccinellid and aphid abundance within these habitats. All field sites were in Cambridgeshire or Suffolk, East Anglia, UK and were surveyed between May and October 2016 and 2017. Three deciduous sites and three coniferous sites were included in the study. Surveys were conducted using a standardised approach involving sweep-netting within grass margins and tree beating to sample ladybirds from trees. Three distinct vegetation structures or layers were surveyed within both the coniferous and deciduous sites; tree, shrub and herb layer. All captured coccinellids were identified to species-level. Seventeen species of coccinellid and over 1300 individuals were recorded during the study period from two distinct site types (deciduous, coniferous). Species richness was lower at deciduous sites (n = 12) in comparison to coniferous (n = 16) sites. The coccinellid community also did not appear to be dominated by H. axyridis at rural sites, in contrast to urban areas. Deciduous woodland appeared to be a lesser preferred habitat of H. axyridis than coniferous woodland. Additionally, there was a distinct difference in the coccinellid community in relation to vegetation structure (across the tree, shrub and herb layers) between coniferous and deciduous sites. Our results indicate that there appear to be distinct native coccinellid communities at deciduous and coniferous sites. We discuss the way in which rural woodlands could act as a refuge for some native coccinellids.

Local and non‐local atmospheric effects of abnormal soil moisture over Indochina during May and June

AbstractIndochina is one of the key areas affecting the East Asian summer monsoon and its thermal condition can modulate the prevailing wind and water vapour transport, especially in the early stages of establishment of the summer monsoon. Previous studies emphasized the climatic effect of the seasonal‐averaged soil moisture (SM), but the subseasonal effects of land surface processes over Indochina are not clear yet. This study investigated the subseasonal effect of SM in Indochina on precipitation in southern China (SC) during May and June together with its relevant mechanism based on both statistical analysis and numerical experiments. Results show that increased SM in Indochina in May is closely associated with increased local (Indochina) precipitation and suppressed non‐local (SC) precipitation in June. The positive SM anomaly over Indochina can persist from May to June, cooling the atmosphere and increasing the specific humidity in the lower troposphere. Meanwhile, the potentially unstable lower troposphere and the ascending motion over Indochina result in strengthened upward moisture advection and condensational heating, which are conducive to forming an abnormal cyclonic circulation and increased precipitation over Indochina. To the northeast, an easterly wind anomaly appears in SC, leading to weakened moisture transport and decreased precipitation. When the SM decreases over Indochina, the opposite results are obtained. Moreover, through increasing and decreasing SM in Indochina in May, numerical experiments showed similar results to those of reanalysis data and further indicated that the moist and thermal processes of the SM anomaly over Indochina play distinct roles in affecting the atmosphere and regional precipitation. The moisture process mainly influences local precipitation, whereas the thermal process can change the precipitation non‐locally. This study highlights the significant local and non‐local impacts of SM in Indochina and could contribute to understanding the physical mechanisms of SM effects.

Development of a Temperate Climate-Adapted indica Multi-stress Tolerant Rice Variety by Pyramiding Quantitative Trait Loci

Successful cultivation of rice (Oryza sativa L.) in many Asian countries requires submergence stress tolerance at the germination and early establishment stages. Two quantitative trait loci, Sub1 (conferring submergence tolerance) and AG1 (conferring anaerobic germination), were recently pyramided into a single genetic background, without compromising any desirable agronomic traits, leading to the development of Ciherang-Sub1 + AG1 (CSA). However, little research has been conducted to enhance plant tolerance to abiotic stress (submergence) and biotic stress (rice blast), which occur in a damp climate following flooding. The BC2F5 breeding line was phenotypically characterized using the AvrPi9 isolate. The biotic and abiotic stress tolerance of selected lines was tested under submergence stress and anaerobic germination conditions, and lines tolerant to each stress condition were identified through phenotypic and gene expression analyses. The Ciherang-Sub1 + AG1 + Pi9 (CSA-Pi9) line showed similar agronomic performance to its recurrent parent, CSA, but had significantly reduced chalkiness in field trials conducted in temperate regions. Unexpectedly, the CSA-Pi9 line also showed salinity tolerance. Thus, the breeding line newly developed in this study, CSA-Pi9, functioned under stress conditions, in which Sub1, AG1, and Pi9 play a role and had superior grain quality traits compared to its recurrent parent in temperate regions. We speculate that CSA-Pi9 will enable the establishment of climate-resilient rice cropping systems, particularly in East Asia.

Impacts of Shade Trees on the Adjacent Cacao Rhizosphere in a Young Diversified Agroforestry System

Cacao agroforestry systems offer the potential to diversify farmer income sources, enhance biodiversity, sequester carbon, and deliver other important ecosystem services. To date, however, studies have emphasized field- and system-scale outcomes of shade tree integration, and potential impacts on the rhizosphere of adjacent cacao trees have not been fully characterized. Interactions at the root–soil interface are closely linked to plant health and productivity, making it important to understand how diverse shade tree species may affect soil fertility and microbial communities in the cacao rhizosphere. We assessed the impacts of neighboring shade tree presence and identity on cacao yields and physical, chemical, and biological components of the cacao rhizosphere in a recently established diversified agroforestry system in South Sulawesi, Indonesia. Stepwise regression revealed surprising and strong impacts of microbial diversity and community composition on cacao yields and pod infection rates. The presence of neighboring shade trees increased nitrogen, phosphorus, and pH in the rhizosphere of nearby cacao trees without yield losses. Over a longer time horizon, these increases in rhizosphere soil fertility will likely increase cacao productivity and shape microbial communities, as regression models showed nitrogen and phosphorus in particular to be important predictors of cacao yields and microbiome diversity and composition. However, neither presence nor identity of shade trees directly affected microbial diversity, community composition, or field-scale distance-decay relationships at this early stage of establishment. These results highlight locally specific benefits of shade trees in this agroecological context and emphasize the rhizosphere as a key link in indirect impacts of shade trees on cacao health and productivity in diversified systems.

Spatial distribution of spore banks of ectomycorrhizal fungus, Rhizopogon togasawarius, at Pseudotsuga japonica forest boundaries

ABSTRACT Ectomycorrhizal (EcM) fungal spore banks can facilitate seedling establishment where compatible host tree species are absent. Although Rhizopogon togasawarius spore banks play an important role in the early establishment stage of endangered Japanese Douglas-fir (Pseudotsuga japonica) seedlings, the dispersal ecology of this EcM fungus is poorly understood. The objective of this study was to clarify the spatial distribution and dispersal distance of R. togasawarius spore banks that extend inside and outside extant P. japonica forests. We evaluated R. togasawarius spore banks in five remnant forests and neighboring arbuscular mycorrhizal artificial plantations using Douglas-fir (P. menziesii) seedling bioassays. Forty-five to ninety-five surface soils were collected along lines of increasing distance from P. japonica forests to neighboring plantations. In each forest, 60%–84% of the soils collected inside or within 50 m of forest boundaries of P. japonica forests harbored R. togasawarius spore banks. The occurrence of R. togasawarius decreased significantly with increasing distance from the forest boundaries. Moreover, R. togasawarius was detected in samples several hundred meters away from forest boundaries. These results suggest that R. togasawarius has a dispersal capacity to extend the range of the spore banks outside the forest of host trees.

The formation of basic approaches of anthropological theater and theatrical anthropology

This article reveals the basic techniques and approaches formed at the dawn of two important and relevant vector of interaction between theater and cultural anthropology in modern theater art, anthropological theater and theatrical anthropology. The goal of this research lies in the analysis of basic techniques and terms that emerged at the early stages of establishment of practical and theoretical approaches towards studying the ritual and theatrical forms. P. Brook's expeditions raised the question of the key elements of theatrical art. For achieving the result, the English the director and screenwriter used bodily techniques and work with space and objects existing in ritual forms. E.Barba, while working in Amazon jungle, resorted to the tactics of participant observer B. Malinowski. The technique of cultural exchange, which appeared in 1970s, is used by K. Kazimierzczuk and modern Polish anthropological theater. The methods of cultural anthropology underlies the formation and development of new ways of interaction and communication between the actors and audience. The experimental works of Peter Brook and Eugenio Barba of the 1970s are analyzed from the perspective of using the methods of cultural anthropology by stage directors. Anthropological theater and theatrical anthropology reveal to modern practitioners and theorists of theatrical art a wide variety of unique methods of work with corporeal nature of the actor, and become the foothold for the development of new relations between the actor-performer and viewer-copartner in performative practices and multicultural phenomena.

Comparative phylogeographic analysis of Cuscuta campestris and Cuscuta reflexa in Kenya: Implications for management of highly invasive vines

Societal Impact StatementEastern Africa is currently infested with dodders—highly invasive vines that threaten agriculture and biodiversity. We describe historical and ecological factors that have potentially shaped dodder invasion in this region. Our results reveal high levels of genetic diversity within dodder populations, which could enhance their ability to colonize new niches. Further, we identify two main population clusters in eastern and western Kenya, a pattern that is mirrored in an established invader (Cuscuta campestris) and a recent introduction (C. reflexa). Immediate control strategies are needed to limit deliberate or inadvertent seed/vine dispersal, eradicate existing populations, and monitor influx of propagules.Summary Invasion by dodder (Cuscuta spp.), holo‐parasitic plants of the Convolvulaceae family, has recently surged in Eastern Africa. Particularly, colonization by two species, Cuscuta campestris and Cuscuta reflexa that have a broad host range and rapid invasiveness, has escalated. We examined the first assessment of genetic diversity of these invasive species in Kenya to inform subsequent management practices. A comparative phylogeographic analysis, based on chloroplast and nuclear ribosomal DNA, was performed to determine genetic diversities, population structure, and isolation of C. campestris and C. reflexa in Kenya. Results reveal high genetic variation in both species within populations across localities. C. campestris had more haplotypes and higher gene diversity (P = .0001) and heterozygosity (P = .004) than C. reflexa. Both species were geographically separated, evidenced by two distinct lineages that mostly corresponded to localities east and west of Kenya. Correlation between genetic and geographic distances revealed evidence of isolation by distance (IBD). We attribute these genetic variation patterns to establishment via similar invasion routes for the studied Cuscuta spp. and suggest that Cuscuta invasion in Kenya is in the early stages of establishment. Rapid eradication is urgently needed to prevent shifts to economically important hosts, which would have devastating impacts. We recommend (i) development of targeted efforts to curb new introductions to limit the potential for genetic variability and adaptation, (ii) prevention of seed and vine dispersal from current incursions, and (iii) complete eradication of existing populations where this is feasible.

Early growth of Cotton is affected by increasing concentration of fresh leaves extract of Calotropis procera

An experiment was conducted to explore the effects of C. procera fresh leaves extract on cotton growth and vigor during seedling and early establishment stage. The trial was carried out in randomized complete block designed (RCBD) with 3 replications and 4 treatments viz., distilled water, 15%, 30% and 45% solution of Calotropis procera fresh leaves extracts. Data regarding the cotton seedling vigor and growth was collected and mean value of each trait were statistically compared through HSD Tukey’s test (P ≤ 0.05). The highest shoot length seedling-1 (252.25 mm), root length seedling-1 (98.33 mm), stem diameter seedling-1 (0.35 mm) and dry weight of the shoot seedling-1 (0.85 g) was noticed in distilled water treatment. Leaf extract treatments caused significant reduction in seedling vigor and growth. The highest reduction was noticed when treated with 45% aqueous extract of C. procera. The above-mentioned treatment caused significant reduction in various seedling traits, which may hinder early establishment of cotton crop. Therefore, the farmers should remove the dense population of C. procera around cotton fields to avoid allelopathic effects of weed and to reduce damaging effects on early growing cotton plants.

Soil biotic effects and competition; What are the mechanisms behind being a successful invader?

The global threat of plant invasions to native ecosystems mandates an understanding of the mechanisms that determine invasion success. While some exotic species establish, spread and impact native ecosystems, others establish with little or no measurable impact. Competitive ability has been highlighted as a key mechanism influencing invasion success and impact, but there is growing evidence that interactions between plants and soil biota may also be important. In particular, escape from natural enemies during the early stages of establishment may give exotic species an advantage over native species subject to their own natural enemies in the soil. Here, we evaluated whether the invasion success and impact of exotic grass species could be explained by competitive superiority over resident native species, advantages gained from the positive effects of native soil communities, or both. We assessed the competitive abilities of six grass species that vary in their invasion success relative to three widespread native grasses, quantified the effects of native soil microbial communities on the performance of both native and exotic grass species, and determined whether there was an interaction between competitive and soil effects. Overall, we found that exotic species were stronger competitors than natives and that native soil effects were weak and did not predict invasiveness. Differences in species relative competitive abilities also did not correlate with invasiveness but demonstrate how some exotic species could outcompete natives and suppress their growth during the invasion process.

Constitutive expression of transcription factor SirZ blocks pathogenicity in Leptosphaeria maculans independently of sirodesmin production.

Sirodesmin, the major secondary metabolite produced by the plant pathogenic fungus Leptosphaeria maculans in vitro, has been linked to disease on Brassica species since the 1970s, and yet its role has remained ambiguous. Re-examination of gene expression data revealed that all previously described genes and two newly identified genes within the sir gene cluster in the genome are down-regulated during the crucial early establishment stages of blackleg disease on Brassica napus. To test if this is a strategy employed by the fungus to avoid damage to and then detection by the host plant during the L. maculans asymptomatic biotrophic phase, sirodesmin was produced constitutively by overexpressing the sirZ gene encoding the transcription factor that coordinates the regulation of the other genes in the sir cluster. The sirZ over-expression strains had a major reduction in pathogenicity. Mutation of the over-expression construct restored pathogenicity. However, mutation of two genes, sirP and sirG, required for specific steps in the sirodesmin biosynthesis pathway, in the sirZ over-expression background resulted in strains that were unable to synthesize sirodesmin, yet were still non-pathogenic. Elucidating the basis for this pathogenicity defect or finding ways to overexpress sirZ during disease may provide new strategies for the control of blackleg disease.

Predicting the potential for spread of emerald ash borer (Agrilus planipennis) in Great Britain: What can we learn from other affected areas?

Societal Impact StatementEmerald ash borer (EAB) is thought to have arrived in North America and European Russia at least 10 years prior to detection. Despite heightened awareness that EAB could invade Great Britain (GB), detection in the early stages of establishment is difficult, and initial symptoms might be mistaken for Chalara ash dieback. Our results suggest that if partial resistance to EAB in Fraxinus excelsior does not significantly dampen EAB population dynamics, then EAB could establish and spread across large parts of southern England within a relatively short time period; however, further northern spread may be limited by the relatively cool climate.Summary The accidental introduction of emerald ash borer (EAB) to North America and European Russia in the 1990s has resulted in an ongoing crisis with millions of ash trees damaged and killed at immense economic and social cost. Improving our understanding of how rapidly the pest might spread should it enter Great Britain (GB) plays an essential part in planning for a potential outbreak. Two metrics are used to investigate the potential dynamics of EAB in GB: the observed rate of spread in the North American and Russian regions; and the relationship between degree days and emergence that may determine environmental suitability and whether the life cycle is univoltine or semivoltine. The pest is still spreading in North America and European Russia with an overall average rate of spread between 2002 and 2018 of approximately 50 km a year. Early detection of the pest is difficult, but a similar delay in detection to that in North America would result in a costly and hard to control outbreak. Comparison of degree days between regions suggests that a semivoltine life cycle is most likely in most areas of GB but spread maybe limited by the relatively cool climate in parts of GB. There are several potentially important differences in the biophysical environment in GB compared with North America and European Russia. However, the speed with which it has invaded these areas highlights the need for early surveillance and mitigations to minimise human‐mediated spread of this highly destructive pest.

Policies to Promote Angel Investment in Startups in Some Countries in Southeast Asia

 Angel investor plays an important role in the startup ecosystem, and is a factor that fills the capital gap for startups and also brings many benefits to startups when they can accompany and support expertise, management and consulting for startups. In the early stage of establishment and development of the startup ecosystem, the role of governments was important in issuing policies and providing solutions to promote angel investment. For Vietnam, encouraging angel investors to invest in startups is an important policy in developing the startup ecosystem. With research on policies to promote angel investment in startups in some countries in Southeast Asia including: Singapore, Thailand and Malaysia, the article summarizes some experiences to promote angel investment in startups in Vietnam.
 Keyword:
 Angel investor, startup.
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Soil Temperature Mediated Seedling Emergence and Field Establishment in Bentgrass Species and Cultivars during Spring in the Northeastern United States

Reestablishment of damaged golf greens and fairways planted to creeping bentgrass (Agrostis stolonifera), colonial bentgrass (A. capillaris), and velvet bentgrass (A. canina) is a common practice following winter injuries. Identifying bentgrass species (Agrostis sp.) and cultivars with the potential to establish under low soil temperatures would be beneficial to achieving more mature stands earlier in the spring. Twelve bentgrass cultivars, including seven cultivars of creeping bentgrass (007, 13-M, Declaration, L-93, Memorial, Penncross, and T-1), two colonial bentgrass cultivars (Capri and Tiger II), and three velvet bentgrass cultivars (Greenwich, SR-7200, and Villa), along with ‘Barbeta’ perennial ryegrass (Lolium perenne) were evaluated for grass cover in the field during early spring. Bentgrass species and cultivars were seeded in the field at the same seed count per unit area. Soil temperatures were monitored in unseeded check plots from initial planting date on 8 Apr. to termination on 29 May 2013. Soil temperatures increased linearly during the 52-day experimental period from 4.7 to 23.5 °C. All species and cultivars emerged at ≈10 °C soil temperature. Bentgrass species and cultivars varied only 2 to 3 days in their initial seedling emergence, while days varied among bentgrasses from 5.5 days (to 10% cover) to 8.6 days (to 90% cover). All velvet bentgrass cultivars required higher soil temperatures (13.6 °C) and more time (26 days) following initial seedling emergence to establish to 90% cover in the early spring. Creeping bentgrass cultivars 007, 13-M, and Memorial, along with colonial bentgrass cultivars Capri and Tiger II, were statistically equal to ‘Barbeta’ perennial ryegrass in their capacity after seedling emergence to achieve faster cover at lower soil temperatures. Heavier (larger) bentgrass seed was associated with faster cover during the early stages of establishment, but seed size was uncorrelated with establishment during later stages from 50% to 90% cover.

Impact of Ambient and Elevated [CO2] in Low Light Levels on Growth, Physiology and Nutrient Uptake of Tropical Perennial Legume Cover Crops.

At early stages of establishment of tropical plantation crops, inclusion of legume cover crops could reduce soil degradation due to erosion and nutrient leaching. As understory plants these cover crops receive limited irradiance and can be subjected to elevated CO2 at ground level. A glasshouse experiment was undertaken to assess the effects of ambient (450 µmol mol−1) and elevated (700 µmol mol−1) levels of [CO2] on growth, physiological changes and nutrient uptake of six perennial legume cover crops (Perennial Peanut, Ea-Ea, Mucuna, Pigeon pea, Lab lab, Cowpea) under low levels of photosynthetic photon flux density (PPFD; 100, 200, and 400 µmol m−2 s−1). Overall, total and root dry biomass, total root length, specific leaf area, and relative growth rates were significantly influenced by levels of [CO2] and PPFD and cover crop species. With few exceptions, all the cover crops showed significant effects of [CO2], PPFD, and species on net photosynthesis (PN) and its components, such as stomatal conductance (gs) internal CO2 conc. (Ci), and transpiration (E). Increasing [CO2], from 450 to 700 μmol mol−1 and increasing PPFD from 100 to 400 μmol ּm−2 ּs−1 increased PN. Overall, the levels of [CO2], PPFD and species significantly affected total water use efficiency (WUETOTAL), instantaneous water use efficiency (WUEINST) and intrinsic water use efficiency (WUEINTR). With some exceptions, increasing levels of [CO2] and PPFD increased all the WUE parameters. Interspecific differences were observed with respect to macro-micro nutrient uptake and use efficiency. With a few exceptions, increasing levels of [CO2] from 450 to 700 μmol mol−1 and PPFD from 100 to 400 μmol m−2 s−1 increased nutrient use efficiency (NUE) of all nutrients by cover crop species.

WHAT DRIVES INTERNATIONAL ENTREPRENEURIAL FIRMS TO EXPAND OVERSEAS: A CASE STUDY APPROACH

Despite the lack of resources, entrepreneurial firms are able to expand internationally from an early stage of establishment. This study aims to explore and identify the drives of expansion for international entrepreneurial firms. This study employed a multi-case analysis approach through in-depth interviews to identify the drivers of international expansion of such firms. Based on our findings we propose a model to enrich the current understanding on the factors that drive young entrepreneurial firms’ expansion to international markets.
 
 JEL: L10; L20; M16; F22
 
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Environmental DNA revealed the fish community of Hokkaido Island, Japan, after invasion by rainbow trout.

In freshwater ecosystems, invasive salmonid fishes can have a significant impact on native fish species. Detecting the invasion and its negative effects is critical for the conservation of native fish communities. We examined the species composition and seasonal changes in the freshwater fish community, including salmonids, on the Kamikawa Plain, Hokkaido Island, Japan, using environmental DNA (eDNA) metabarcoding. We detected 23 fish species in 176 samples collected from 16 sites over 12 months (October 2018 – August 2019). Between 11 and 20 species were detected at each site, including five native salmonids (Oncorhynchus masou, Oncorhynchus keta, Parahucho perryi, Salvelinus leucomaenis leucomaenis and Salvelinus malma krascheninnikova). The invasive alien rainbow trout Oncorhynchus mykiss was detected at all 16 sites and it was the most commonly detected salmonid. Although we found no obvious competitive exclusion of native salmonids by rainbow trout in the study area, the invasive species occurred more often and at more sites than any of the natives. We also determined the occurrence and seasonal changes in the fish community, classified as native salmonids, invasive rainbow trout, Cypriniformes and other benthic fishes. There were fewer species overall in winter, but the sites with higher species richness in winter were on the lower reaches of the river. In addition, we detected domestic invaders, such as the topmouth gudgeon, Pseudorasbora parva, although they were less prevalent than rainbow trout. These results show the effectiveness of eDNA metabarcoding, which can be used for surveying species richness at an ecosystem scale. In particular, the detection of the early stages of establishment and spread of invasive species can be achieved by eDNA monitoring.