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The flora of high mountain areas is one of the least known and one of the most threatened by climate change. In addition, the phytogeographic delimitation of the mountains is difficult and not accurate enough. In this work we describe the flora of the Altoandina province in the Southern Cone of South America based on the geographical distribution of taxa exclusive to this province, we characterize the subdivisions at a regional level and generate a map of the identified districts. The results show that 883 taxa are exclusive of this province, of which 151 are only present in Chile, 220 in Argentina, and 512 are shared by both countries or are also present in Bolivia or other Andean countries. Asteraceae, Poaceae, Fabaceae, and Violaceae are the richest families in the province, while Senecio, Viola and Nototriche are the richest genera. Through a network-based analysis, we confirm the presence of three Districts in the Altoandina province: Quechua, Cuyano-Pikumche, and Nothoandino. This work aims to contribute to the knowledge on geographical patterns of the High Andean flora and its conservation. [ABSTRACT FROM AUTHOR]

Biological invasions are one of five direct drivers of global change that act synergistically threatening biodiversity and the provision of ecosystem services globally. In this work we compile the list of exotic woody species that have been introduced in Argentina, we characterize them according to their geographical origin, use, foliage phenology, reproduction, dispersal, and we analyse their geographical distribution within Argentina. Based on the bibliography, we identify those species that are currently or potentially problematic for Argentina. Most of the species are native to Eurasia and the main reason for their introduction was their ornamental use. They are mostly monoecious, with deciduous leaves, without vegetative reproduction, with fleshy fruits and dispersed by animals. The area corresponding to the Yungas, the Paranaense Forest and the Humid Chaco presents the largest number of exotic species; the area corresponding to the Espinal and Dry Chaco has the largest number of currently problematic species and, together with the Pampeana area, the largest number of potentially problematic species. Finally, we propose actual problematic species in areas without native trees and potentially problematic species with broad distribution in Argentina should be monitored and probably managed among the studied species. [ABSTRACT FROM AUTHOR]

Plants are expected to face novel challenges as consequence of human-driven global change. Outbreaks of pests and higher incidence of contaminants are increasing. Plants can improve tolerance to stress factors through associations with symbiotic microorganisms. Certain grasses establish persistent and asymptomatic symbioses with Epichloë fungal endophytes, which are known to confer protection against Herbivores and improve plant tolerance to abiotic stress factors. Nonetheless, accumulating evidence suggests the symbiosis outcome is context-dependent. We evaluated the capacity of the endophyte fungus E. occultans in protecting the annual grass Lolium multiflorum against a spontaneous larva attack of the generalist herbivore Agrotis ipsilon under episodic exposure of plants to ozone. Symbiotic and non-symbiotic plants were individually grown outdoors and exposed to ozone at different stages resulting in four treatments: control (plant never exposed to ozone), plant exposed to ozone at vegetative stage, plant exposed to ozone at reproductive stage, and plant exposed to ozone at both stages. After the last exposure, there was an outbreak of A. ipsilon larvae. We evaluated herbivore damage, seed production per plant, and endophyte transmission to the seeds. Frequency of attacked plants was irrespective of both the endophyte and ozone exposure. However, the damage level per plant was only reduced by the endophyte. Seed production was slightly lower in endophyte-symbiotic plants and not affected by ozone. Interestingly, herbivore damaged and undamaged endophyte-symbiotic plants contributed equally to seed production. However, in plants exposed to ozone once at vegetative or reproductive stage, endophyte-free undamaged plants had higher seed production than endophyte-free damaged plants. Ozone treatments did not affect the transmission efficiency of endophytes to the seeds. Mean endophyte transmission efficiency per plant was 95%. Medium doses of ozone seem to have undetectable effects on grass-endophyte symbiosis, not affecting the defensive mutualism nor the persistence of the symbiont across generations. [ABSTRACT FROM AUTHOR]

Background and aims: It is essential to know the conservation status of the species, in order to prioritize intervention and management of the most threatened species populations. Usually available information is not enough for a definitive evaluation; therefore, it is important to develop rapid assessment methods of conservation status. In this work we performed a preliminary assessment of the conservation status for the Patagonian orchid genus Gavilea (Orchidaceae, Chloraeinae), and we compared our results with that obtained by experts. M&M: We compiled a database with location and collection date of herbarium specimens of the 17 species of Gavilea. We apply an adaptation of the criteria proposed by Krupnik et al., (2009) related to the geographical and temporal distribution of the collections. We compare the classification obtained with those published by experts. Results: We categorize the 17 species, with 1 Potentially Extinct species, 6 Potentially Threatened species and the remaining 10 Potentially Not Threatened species. In addition, we found that 15 of the 17 species coincide in their classification with the evaluation of experts; only for G. platyantha, our categorization was more optimistic than that of experts. Conclusions: The method allowed to categorize all the species and determine the priorities for future studies or interventions. In most cases, the categorization coincided with that carried out by experts. In general, we consider that the method is a good tool to generate an assessment of the preliminary conservation status of plant species. [ABSTRACT FROM AUTHOR]

Grasses are ancestrally tropical understory species whose current dominance in warm open habitats is linked to the evolution of C4 photosynthesis. C4 grasses maintain high rates of photosynthesis in warm and water stressed environments, and the syndrome is considered to induce niche shifts into these habitats while adaptation to cold ones may be compromised. Global biogeographic analyses of C4 grasses have, however, concentrated on diversity patterns, while paying little attention to distributional limits. Using phylogenetic contrast analyses, we compared macro-climatic distribution limits among ~1300 grasses from the subfamily Panicoideae, which includes 4/5 of the known photosynthetic transitions in grasses. We explored whether evolution of C4 photosynthesis correlates with niche expansions, niche changes, or stasis at subfamily level and within the two tribes Paniceae and Paspaleae. We compared the climatic extremes of growing season temperatures, aridity, and mean temperatures of the coldest months. We found support for all the known biogeographic distribution patterns of C4 species, these patterns were, however, formed both by niche expansion and niche changes. The only ubiquitous response to a change in the photosynthetic pathway within Panicoideae was a niche expansion of the C4 species into regions with higher growing season temperatures, but without a withdrawal from the inherited climate niche. Other patterns varied among the tribes, as macro-climatic niche evolution in the American tribe Paspaleae differed from the pattern supported in the globally distributed tribe Paniceae and at family level. [ABSTRACT FROM AUTHOR]

Annual productivity of croplands can be increased by intensifying cropping sequences and fine-tuning agronomic management, improving the ratio between seasonal grain yield and annual available resources. The aims of this study were to evaluate, for different crop sequences and agronomic practices, (i) grain yield (GY), and energy of GY (EY) on annual basis; (ii) the relative contribution of each crop to the annual GY and EY of the crop sequences; and (iii) the maximum attainable annual EY. In a five-year field experiment at the central Rolling Pampa of Argentina, three crop sequences: soybean mono-cropping (Sy), a two-year rotation alternating maize and soybean (Mz-Sy), and a three-year rotation including wheat/soybean, maize, and soybean (Wt/Sy-Mz-Sy) were evaluated under the presence of either fallow (F) or cover crops (CC) during winter, and under two agronomic systems: conventional (CM) and intensified management (IM). For EY, Mz-Sy and Wt/Sy-Mz-Sy sequences greatly surpassed (P < 0.01) Sy (78% and 86% higher) across all years. The CC negatively affected (P < 0.001) the annual GY of the sequences by mostly affecting maize GY (−14% than under F), but this effect varied with the experimental year (rainfall levels) and CC composition (grass/legume proportion). The annual GY of the Mz-Sy (6.47 Mg ha−1) and Wt/Sy-Mz-Sy (6.69 Mg ha−1) sequences increased (P < 0.001) in the IM system compared to CM (5.33 and 5.64 Mg ha−1). In addition, under IM the penalty of CC on the annual GY of the crop sequences was lower (−7%) than under CM (−14%). From the combination of crop sequences and agronomic systems, the highest annual EY corresponded to the more intensified Wt/Sy-Mz-Sy sequence under IM (176 GJ ha−1), doubling the lowest EY obtained by soybean mono-cropping under CM (87 GJ ha−1). This result highlights the opportunity for intensification of cropping sequence and agronomic management to increase the annual productivity of the existing cropping area. • More diverse crop sequences surpassed soybean mono-cropping in annual grain yield. • Cover crops negatively affected grain yield of crop sequences by mostly affecting maize yields. • Intensified management system increased annual grain yield of crop sequences. • Intensified management system minimized cover crop penalties on annual grain yield of the sequences. • Wheat/soybean-maize-soybean rotation under the intensified management had the highest annual grain yield. [ABSTRACT FROM AUTHOR]

• Effects of warm nights on FHB were studied in cereal crops under field conditions. • Warm nights were more favourable to F. graminearum than F. poae. • Warm nights and FHB affected grain quality parameters. • Warm nights significantly increased mycotoxins (DON and 3-ADON) concentration. • Increases in night temperature can modify plant-pathogen interaction. The disease known as Fusarium Head Blight (FHB) is one of the most devastating cereal diseases, among which Fusarium graminearum and Fusarium poae have been isolated to be the main etiological agents in cereal crops such as barley and wheat. Currently, global climate change is one of the major concerns worldwide, and temperature is likely to be one of the most affected variables in the future. However, it is unknown how these changes will affect fungal diseases such as FHB. The present research aimed to study the F. graminearum / F. poae -barley/wheat pathosystem under future climatic conditions. The effects of the increase in night temperatures (3 °C) on disease variables, grain quality, and mycotoxin contamination were evaluated under field conditions over three years (2016, 2017, and 2018). For both crops, the results showed that warm nights favoured F. graminearum development over F. poae , reducing grain quality parameters and increasing the mycotoxin concentration significantly. The results obtained along the present work provide a better understanding of the F. graminearum/F. poae -barley/wheat pathosystem and the basis for potential future research related to climate change studies under field conditions directly impacting food quality and safety. [Display omitted] [ABSTRACT FROM AUTHOR]

Analysis of Poaceae biodiversity in austral South America. The Poaceae is one of the best represented families in austral South America with a total of 206 genera comprising 1523 species arranged in 10 different subfamilies. Here we analyzed the distribution of these taxa in Argentina, southern Brazil (Paraná, Rio Grande do Sul and Santa Catarina), Chile, Paraguay, and Uruguay; we discuss the species richness of the different subfamilies, tribes and genera, its distribution, endemics, annual and perennial species as well as Kranz and non Kranz taxa, its geographical distribution in relation to temperature and rainfall, disjunct genera, and proportion of taxa in relation to the different ecoregions in the area. [ABSTRACT FROM AUTHOR]

Abstract: We reconstructed the invasion history and modelled the potential distribution of the invasive grass Bromus tectorum in southern South America. On the base of herbarium data, we described two aspects of B. tectorum's range expansion over time: area of occupancy and extent of occurrence. A maximum entropy model was used to identify both climatic variables associated with B. tectorum's current distribution and potentially invasible areas. The area-of-occupancy curve showed a steady increase of the occupied area since the first collection in 1937, with no obvious asymptote. However, the extent-of-occurrence curve indicated that range expansion was not homogeneous through time, but faster between 1965 and 1980. Most invasible areas were arid and semiarid with markedly Mediterranean precipitation regime. Within this susceptible region, there were large areas containing only a few known records of B. tectorum. Our results indicate that B. tectorum has successfully expanded over much of southern South America. In addition, there seems to be room for further local invasion (i.e. an increase of its area of occupancy) over large susceptible areas within the invaded region. Overall, our results confirm the suitability of southern South America's arid environments to B. tectorum invasion, and stress the importance of long-distance dispersal in accelerating its expansion across the region. [Copyright &y& Elsevier]

Plants have evolved mechanisms to survive herbivory. One such mechanism is the induction of defences upon attack that can operate intergenerationally. Cool-season grasses (sub-family Pooideae) obtain defences via symbiosis with vertically transmitted fungal endophytes (genus Epichloë) and can also show inducible responses. However, it is unknown whether these herbivore-induced responses can have intergenerational effects. We hypothesized that herbivory by aphids on maternal plants induces the intergenerational accumulation of endophyte-derived defensive alkaloids and resistance intensification in the progeny. We subjected mother plants symbiotic or not with Epichloë occultans, a species known for its production of anti-insect alkaloids known as lolines, to the aphid Rhopalosiphum padi. Then, we evaluated the progeny of these plants in terms of loline alkaloid concentration, resistance level (through herbivore performance), and shoot biomass. Herbivory on mother plants did not increase the concentration of lolines in seeds but it tended to affect loline concentration in progeny plants. There was an overall herbivore-induced intergenerational effect increasing the endophyte-conferred defence and resistance. Symbiotic plants were more resistant to aphids and had higher shoot biomass than their non-symbiotic counterparts. Since maternal herbivory did not affect the loline concentrations in seeds, the greater resistance of the progeny could have resulted from an inherited mechanism of epigenetic regulation. It would be interesting to elucidate the origin of this regulation since it could come from the host or the fungal symbiont. Thus, endophyte-driven differential fitness between symbiotic and non-symbiotic plants might be higher as generations pass on in presence of herbivores. [ABSTRACT FROM AUTHOR]

Peperomia nitida and P. armondii (Piperaceae, subgen. Rhyncophorum) are recorded for the first time for the Argentinean flora in the province of Misiones. The species are described and illustrated, and their geographical distributions are updated. A key to distinguish the Argentinean species of subgen. Rhyncophorum is included, and P. elongata is excluded from the Argentinean Flora. [ABSTRACT FROM AUTHOR]

We examined spatial patterns of fire-caused mortality and after-fire establishment of two dominant shrub species, Baccharis dracunculifolia and Eupatorium buniifolium in a humid temperate South American savannah. Our objective was to determine whether fires mediate in interactions between these two species. After a natural fire burned a large tract of savannah, we established two plots (respectively 550 and 500 m2) within which we mapped all surviving and dead shrubs as well as all individuals of shrub species that recruited in the following year. We used techniques of point-pattern analysis to test specific null hypotheses about spatial associations in the distribution, mortality, and establishment of shrubs. Results support the notions that fire mediates interactions between these two species. Fire-caused death of E. buniifolium tended to occur selectively in the vicinities of Baccharis individuals, and recruitment of B. dracunculifolia tended to be concentrated in the places of dead shrubs. These responses, however, were contingent on local abundances of shrubs which depend in part from the recent fire history. Anthropogenic perturbation of the natural fire regime would have therefore distorted the role of fire mediated interactions as drivers of the dynamics of the vegetation of this temperate savannah. [ABSTRACT FROM AUTHOR]

The Teyú Cuaré Provincial Park is located in the department of San Ignacio, Misiones, Argentina (27º 16′ S, 55º 33′ W) and is 78 ha in area. The studied area has a total of 659 species of vascular plants, 384 genera and 110 families, 15 of which are Pteridophytes, 18 Monocotyledons and 77 Dicotyledons. Four of these species are endemic to the park and other 19 are restricted to Argentina, in the area included by this work. The families with the largest number of species are Poaceae, Fabaceae and Asteraceae; the richest genera are Paspalum and Panicum. Only 14 species are adventive. Our results show the great richness of species and the singularity of the flora of the park. [ABSTRACT FROM AUTHOR]

Background and Aims In the subfamily Poöideae (Poaceae), certain grass species possess anti-herbivore alkaloids synthesized by fungal endophytes that belong to the genus Epichloë (Clavicipitaceae). The protective role of these symbiotic endophytes can vary, depending on alkaloid concentrations within specific plant–endophyte associations and plant parts. Methods We conducted a literature review to identify articles containing alkaloid concentration data for various plant parts in six important pasture species, Lolium arundinaceum , Lolium perenne , Lolium pratense , Lolium multiflorum | Lolium rigidum and Festuca rubra , associated with their common endophytes. We considered the alkaloids lolines (1-aminopyrrolizidines), peramine (pyrrolopyrazines), ergovaline (ergot alkaloids) and lolitrem B (indole-diterpenes). While all these alkaloids have shown bioactivity against insect herbivores, ergovaline and lolitrem B are harmful for mammals. Key Results Loline alkaloid levels were higher in the perennial grasses L. pratense and L. arundinaceum compared to the annual species L. multiflorum and L. rigidum , and higher in reproductive tissues than in vegetative structures. This is probably due to the greater biomass accumulation in perennial species that can result in higher endophyte mycelial biomass. Peramine concentrations were higher in L. perenne than in L. arundinaceum and not affected by plant part. This can be attributed to the high within-plant mobility of peramine. Ergovaline and lolitrem B, both hydrophobic compounds, were associated with plant parts where fungal mycelium is usually present, and their concentrations were higher in plant reproductive tissues. Only loline alkaloid data were sufficient for below-ground tissue analyses and concentrations were lower than in above-ground parts. Conclusions Our study provides a comprehensive synthesis of fungal alkaloid variation across host grasses and plant parts, essential for understanding the endophyte-conferred defence extent. The patterns can be understood by considering endophyte growth within the plant and alkaloid mobility. Our study identifies research gaps, including the limited documentation of alkaloid presence in roots and the need to investigate the influence of different environmental conditions. [ABSTRACT FROM AUTHOR]

Question: Is domestic cattle an appropriate surrogate for fire in a protected humid temperate savanna? Study area: El Palmar Grande de Colón (31°52' S, 58°17' W), Argentina. Methods: We surveyed dense Butia yatay palm savannas in two neighboring protected areas, El Palmar National Park (EPNP), under cattle exclusion since 1970 with sporadic burning; and La Aurora Wildlife Refuge (LAWR), under moderate cattle density, and not burnt since 1997. In each area, we randomly selected ten dense savanna stands, established 500 m? plots and undertook floristic survey in spring and summer to produce exhaustive plant-species lists. We statistically compared the two samples in terms of: local and global diversities; compositional heterogeneity among stands; mean similarity to a historical record from the area; overall species composition; and abundance and numbers of species with different growth habits and origins. Results: Differences between our samples are clear-cut. Savannas at EPNP have significantly increased local and global species richness and exhibit decreased similarities with the historical record. They have a novel understory, with significantly increased abundances and species numbers of fire-resistant grassland shrubs and fire-sensitive trees, and a groundcover with significantly increased richness of subshrub and perennial graminoid species. Savannas at LAWR have virtually no woody understory, and exhibit a groundcover dominated by an impoverished suite of perennial grasses, with significantly increased abundances and numbers of annual and of exotic species. Conclusions: Our results suggest that large-scale, long-term cattle exclusion and sporadic fires have resulted in changes in the structure and composition of the savanna vegetation leading to increased plant species diversity. Apparently, conservation of these humid savannas in protected areas requires periodic fire, while domestic cattle are a poor alternative for maintaining their plant species diversity. [ABSTRACT FROM AUTHOR]

The diversity of pollen rain monthly collected during two years (2011-2013) from the atmosphere in Tauber traps located at three sites in El Palmar National Park (Entre Ríos Province) is used to characterize the source vegetation. Site 1 is a mixed area composed of grassland, palm savanna, and wetland communities, site 2 is a grassland area and site 3 is a dense palm savanna. A total of 71 pollen-grain types grouped in 43 families coming from local, regional and extra- regional areas are identified. Of them, sixteen pollen types with more than 1% of Annual Pollen Influx in at least two samples were used in this analysis. Different factors involved in quali-quantitave changes of taxa during the observation interval (e.g. pollination affinity, origin of pollen grains, canopy effect, meteorological variables) are further considered. The floral composition of each site compared to their palynoassemblages revealed that site 2 is characterized by a high abundance of Asteraeceae-Asteroideae, with an increase in the value of Vernonia (Asteraceae Cichoroidea) and Lamiaceae during the second year. Palynological composition in Sites 1 (mixed vegetation) and 3 (dense palm savanna) was dominated by Asteraeceae-Asteroideae, Myrtaceae, Blepharocalyx salicifolius, and Poaceae, with percentage fluctuations between years. Site 3 is differentiated from the other two ones by the record of Butia yatay in low frequency that showed similar percentages in both years, whereas Adiantopsis chlorophylla and Microgramma mortoniana increased during the second year. [ABSTRACT FROM AUTHOR]

Seed germination of the kiwifruit (Actinidia deliciosa A. Chev. C.F. Liang and A.R. Ferguson), a deciduous, perennial vine, is low because of seed dormancy. The main purpose of this study was to characterize kiwifruit seed dormancy and germination in response to environmental factors such as temperature and light. Dormancy of hydrated seeds is alleviated by the perception of a period at low temperatures (stratification) of at least 3 weeks at 2 or 5°C. Alleviation of dormancy is accomplished by incubation at fluctuating temperatures (20/30°C). A red light pulse did not affect germination, whereas a far-red light pulse strongly inhibited germination. This inhibition was readily reverted by a second pulse of red light, indicating that phytochromes are also involved in dormancy alleviation. Although seed germination was inhibited by the fruit pulp, the latter prevented neither perception of low temperature nor changes in the light sensitivity of the seeds. Therefore, it can be advanced that kiwifruit seeds will only germinate after dispersal if the time–temperature requirement for dormancy alleviation and fluctuating temperatures for dormancy termination are fulfilled. Perception of a closed canopy might interfere with dormancy termination. [ABSTRACT FROM PUBLISHER]

Since 1965, El Palmar National Park, Entre Ríos, protects the largest remnant of Butia yatay palm savanna, a species-rich ecosystem threatened by human activity. To study the functioning of this ecosystem and to manage its preservation, it is necessary to have an adequate picture of its vegetation heterogeneity. In this paper, we present a phytosociological classification of the plant communities of this savanna, describe their structure, species composition and richness, and provide their distribution in the landscape. To stratify our data acquisition, we first mapped the major geomorphic units in this landscape. In the spring of 1999 and the following summer, we conducted complete inventories of plant species in 73 savanna stands with different fire histories distributed throughout the different geomorphic units. We used multivariate analysis and numerical classification techniques to group inventories in plant community types and species in floristic groups. Finally, we summarized the compositional differences among community types as a metric multidimensional scaling ordination. We defined seven community types, recognizable by combinations of 20 floristic groups. The pattern of similarities among these community types suggests that floristic heterogeneity is organized along two gradients, one associated with soil texture differences, and the other with differences in water input. Three of the community types, closely related to each other, are distributed on elevated fluvial terraces and interfluves, in correspondence with gradual differences in topography and soil. These community types undergo successional change due to woody encroachment triggered by cattle exclusion and maintained by scarcity of natural fires. The remaining four community types are strictly associated with rocky outcrops, sand deposits, or runoff pathways that interrupt the landscape matrix, with no apparent woody encroachment. [ABSTRACT FROM AUTHOR]

BACKGROUND Barley is one of the most sown crops in the world, with multiple uses such as human consumption, animal feed and for the malting industry. This crop is affected by different diseases, such as Fusarium Head Blight (FHB), that causes losses in yield and quality. In the last years F. graminearum and F. poae were two of the most frequently isolated species in barley grains, so the aim of this study was to evaluate the interaction between these Fusarium species and the effects on disease parameters, grain quality and mycotoxin contamination on five barley genotypes under field conditions. RESULTS: Statistical differences between Fusarium treatments for some parameters depending mainly on the year/genotype were found. The results showed that the germination process was affected by both Fusarium species. As to grain quality and the different hordein fractions, it was observed that F. graminearum affects preferentially D and C‐hordeins. Different concentrations of nivalenol, deoxynivalenol and their acetylated derivatives (3‐acetyl deoxynivalenol (3‐ADON), 15‐acetyl deoxynivalenol (15‐ADON)) were detected. CONCLUSIONS: In the present work, no evidence of synergism between F. graminearum and F. poae were found regarding disease parameters and mycotoxin contamination. However, at least in the years with favorable climatic conditions to FHB development and depending on the barley genotype, a continuous monitoring is deemed necessary to prevent the negative impact on protein composition and germinative parameters © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND: Wheat is the most important winter crop in the world, being affected by the presence of fungal, mainly those belonging to the Fusarium genus. Fusarium head blight (FHB) is a serious disease that causes important economic damage and quantitative/qualitative losses, with Fusarium graminearum and Fusarium poae being two of the most isolated species worldwide. The present study aimed to evaluate the interaction between F. graminearum and F. poae and the effects on disease parameters, grain quality and mycotoxin contamination on five wheat genotypes under field conditions during three growing seasons. RESULTS: Statistical differences between Fusarium treatments were found for disease parameters, grain quality and mycotoxin contamination during the 2014/2015 growing season. High values of incidence (58.00 ± 8.00%), severity (6.28 ± 1.51%) and FHB index (4.72 ± 1.35) were observed for F. graminearum + F. poae treatment. Regarding grain quality, the results showed that the degradation of different protein fractions depends on each Fusarium species: glutenins were degraded preferably by F. graminearum (−70.82%), gliadins were degraded preferably by F. poae (−29.42%), whereas both protein fractions were degraded when both Fusarium species were present (−60.91% and −16.51%, respectively). Significant differences were observed for mycotoxin contamination between genotypes, with Proteo being the most affected (DON = 12.01 ± 3.67 μg g−1). In addition, we report that 3‐ADON predominated over 15‐ADON in the three seasons evaluated. CONCLUSION: Variations in plant–pathogen interaction (Fusarium–wheat pathosystem) should be considered at least in years with favorable climatic conditions for FHB development, as a result of the potential impact of this disease on grain quality and mycotoxin contamination. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The design of sustainable, high-yielding continuous cropping systems requires to maintain, or even restore, critical ecosystem properties, such as soil functioning. In the rolling Pampa (Argentina), total soil organic carbon decreased by 15–40% due to continuous agriculture. Therefore, soils are far from their potential carbon saturation. The most promising strategies to increase yield and restore carbon rely on the sustainable intensification of the current cropping systems based on no-tillage practices. Such strategies also involve increasing resource use through cover crops, increasing cropping intensity, and performing accurate and flexible fertilization and crop protection schemes. This study evaluated the effects of different cropping systems on soil organic carbon stocks in the uppermost 20 cm of the soil profile. We performed a 5-year experiment combining five cropping systems with different cash crop sequence (soybean mono-cropping and two different rotations) and agronomic technology (genotypes, fertilization, and crop protection), which in turn were evaluated under both fallow and cover cropping. Five years after the beginning of the experiment, all systems had a net positive balance of soil carbon accumulation, which averaged 2.25 t C.ha-1.yr-1. On average, 41% of plant carbon inputs remained within the first 20 cm of the soil profile. Cover crops increased plant carbon inputs, with larger effects as the cash crops occupied a shorter period in the field. Therefore, compared to fallow, cover crop doubled carbon input in soybean mono-cropping, had intermediate increments in the maize-soybean sequence, and had the lowest increments in the wheat/soybean-maize-soybean sequence. Under fallow, both rotations outperformed the plant carbon inputs of soybean mono-cropping. Management intensification, only evaluated for rotations, increased plant carbon inputs and soil carbon accumulation in a synergistic interaction with cover crop. Our results indicate that increasing carbon inputs through crop rotation, cover cropping and better agronomic technology is an opportunity to revert the long trend of soil carbon deficit of these agricultural lands. • Approximately 41% of plant carbon inputs remained in soil. • Intensified management and cover cropping acted synergically. • Crop rotations with more frequency of maize accumulated more soil carbon. • Cover cropping doubled annual carbon inputs of soybean mono-cropping. [ABSTRACT FROM AUTHOR]

There are numerous maps of the spontaneous vegetation of Argentina. However, a country-level map with enough detail to discriminate vegetation units within the phytogeographic provinces described by Cabrera (1976) is lacking. We analyzed vegetation descriptions published in recent decades, with special attention to those that produced physiognomic-floristic maps. As a result of this analysis, here we present a physiognomic-floristic map of spontaneous vegetation of Argentina that shows the heterogeneity within phytogeographic provinces. The map has 50 vegetation units as subdivisions of the phytogeographic ecotone and provinces early described, and a brief physiognomic-floristic description of each ecotone, province and vegetation unit. We propose a nomenclature of each vegetation unit based on dominant type of spontaneous vegetation and characteristic species and present digital cartographic material. [ABSTRACT FROM AUTHOR]

In recent decades, large forested areas in southern Mexico have been degraded and even eliminated, often due to conversion of these areas to pastures for cattle grazing. Silvopastoral systems combine livestock raising with tree use, favor conservation of biological diversity, and provide a variety of services to the environment and to farmers. In this study, we evaluated tree regeneration in cattle pastures in the Tulijá River Valley of Chiapas, Mexico. We argue that density of seedlings/saplings in the pastures studied is associated with the density of adult trees, with the type of dominant grass (induced or introduced), and with the practice of weeding around seedlings and saplings. We sampled trees in pastures according to categories of size, as well as herbaceous vegetation in 35 cattle pastures, and interviewed farmers with respect to their practices of weeding around seedlings and saplings. We evaluated specieś capacity for regeneration, and classified species as having adequate or limited natural regeneration capacity (ANR and LNR, respectively). Furthermore, we constructed a generalized least squares model to identify whether density of adult trees, type of grass cover (induced vs. introduced), and farmerś practice of weeding affect the density of seedlings and saplings of tree species. Finally, we identified dispersal agents of each tree species recorded and then compared the relative abundance of seedlings/saplings with adult trees for each dispersal agent, using chi-square goodness-of-fit test. In the 35 cattle pastures, we found 17 species (28%) with ANR capacity, 90% of which belonged to secondary vegetation, and 44 species (72%) with LNR capacity; most of these belonged to late successional tree species. Density of seedlings/saplings was positively associated with density of adult trees and the practice of manual weeding. The greatest abundance of seedlings/saplings corresponded to species dispersed by cattle, followed by those dispersed by wind. For adult trees, the most common type of dispersal was by wind, followed by cattle. These results suggest that native tree species are principally dispersed by cattle and wind, and cattle have a positive effect on the regeneration capacity of the most abundant tree species in the pastures studied. We conclude that Chol Mayan silvopastoral management practices in the study communities in Chiapas, Mexico allow for and promote regeneration of native tree species, most of which belong to secondary vegetation, although some belong to late successional species. These simple management practices allow for harvesting some trees in the pasture while also maintaining the regeneration process. [ABSTRACT FROM AUTHOR]

The replacement of native vegetation by pastures or tree plantations is increasing worldwide. Contradictory effects of these land use transitions on the direction of changes in soil organic carbon ( SOC) stocks, quality, and vertical distribution have been reported, which could be explained by the characteristics of the new or prior vegetation, time since vegetation replacement, and environmental conditions. We used a series of paired-field experiments and a literature synthesis to evaluate how these factors affect SOC contents in transitions between tree- and grass-dominated (grazed) ecosystems in South America. Both our field and literature approaches showed that SOC changes (0-20 cm of depth) were independent of the initial native vegetation (forest, grassland, or savanna) but strongly dependent on the characteristics of the new vegetation (tree plantations or pastures), its age, and precipitation. Pasture establishment increased SOC contents across all our precipitation gradient and C gains were greater as pastures aged. In contrast, tree plantations increased SOC stocks in arid sites but decreased them in humid ones. However, SOC losses in humid sites were counterbalanced by the effect of plantation age, as plantations increased their SOC stocks as plantations aged. A multiple regression model including age and precipitation explained more than 50% ( p < 0.01) of SOC changes observed after sowing pastures or planting trees. The only clear shift observed in the vertical distribution of SOC occurred when pastures replaced native forests, with SOC gains in the surface soil but losses at greater depths. The changes in SOC stocks occurred mainly in the silt+clay soil size fraction ( MAOM), while SOC stocks in labile ( POM) fraction remained relatively constant. Our results can be considered in designing strategies to increase SOC storage and soil fertility and highlight the importance of precipitation, soil depth, and age in determining SOC changes across a range of environments and land-use transitions. [ABSTRACT FROM AUTHOR]