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Argentina is the country with the highest proportion of arid and semi-arid ecosystems in Latin America. In the rangelands of Southwestern Buenos Aires (Patagones Department), there is a clear advancement of the agricultural frontier to the detriment of the native forest in this region. Due to rainfall variation and seed acquisition, Thinopyrum ponticum is cultivated as a forage perennial crop in this region. Our objective was to evaluate the performance of T. ponticum as a facilitating crop for the medium-term rehabilitation of natural grasslands in semi-arid areas. The working hypotheses were that: 1) native perennial grass cover increases over the years and 2) diversity and specific richness of the vegetation are enhanced by the duration of Tall Wheatgrass implantation. Data were collected from commercial plots where T. ponticum was shown: recent implantation (5–8 years, RI); medium implantation (13–15 years, MI); and old implantation (20–22 years, OI). Thirty-four species were identified and classified into seven functional groups: Annual grasses, annual herbs, perennial herbs, exotic perennial herbs, perennial forage grasses, exotic perennial forage grasses, perennial forage exotic grasses, and non-forage perennial grasses. Thinopyrum ponticum 's total cover was between RI and OI. Total cover, species richness, and Shannon-Weaver diversity index showed no differences among treatments. Perennial forage grasses exhibited higher cover values in sites with greater implantation age and annual grasses showed the opposite response. Our results indicated that T. ponticum does not invade the sampled plots and enhances the colonization of the planted plots by perennial forage native species. However, even though the herbaceous cover had been recovered, the woody layer which could provide environmental services and specific values for conservation was not. [ABSTRACT FROM AUTHOR]

Premise of research. Dichanthelium extends from Canada to Argentina and is most species rich in eastern North America. These C3 panicoid grasses, which are mixed mating and flower two or three times per year, displaying different vegetative growth forms over that time, are renowned for their taxonomic complexity. Thus, there are drastically differing taxonomic treatments; however, no well-sampled phylogenetic perspective is yet available to further explore relationships among species or species complexes. Methodology. We developed the first broadly sampled phylogeny of Dichanthelium , covering the entire range of the genus, but with a focus on the species-rich eastern North American distribution. We sampled 72 taxa (290 accessions), including all currently recognized taxa in the recent Flora of North America treatment. Our dataset consisted of the plastid locus rpl32-trnL and the nuclear loci internal transcribed spacer (ITS) and granule-bound starch synthase I (GBSSI) and was analyzed using maximum likelihood. We calibrated our phylogeny to test the divergence time of the North American clade and likewise used ITS data to explore putative hybridization. Pivotal results. South American species of Dichanthelium formed a grade of successive sisters to the North American clade, which we recovered as originating in the late Miocene–early Pliocene. We recovered 27 subclades, most of these representing species complexes or morphologically similar species. Numerous taxa were resolved outside of their putative species groups and are apparently morphologically cryptic species. We show several cases of putative hybridization in eastern North American and Hawaiian species. Conclusions. Our phylogeny provides a foundation for understanding this taxonomically complicated group of grasses, which will need detailed future studies into species complexes to provide greater taxonomic resolution and understanding of biological processes driving the evolution and diversification of the clade. This should include further study of autogamy and its evolutionary consequences in North American taxa. We propose an adjusted taxonomic treatment of specific members of the genus based mostly on our phylogenetic results. [ABSTRACT FROM AUTHOR]

Question: Do shrubs negatively affect the germination of perennial grass species in regeneration microsites? We experimentally analyzed the effect of soils from plant patches dominated by two shrub species (Larrea divaricata and Schinus johnstonii) and their propagules on the germination of three co‐dominant herbivore‐preferred perennial grass species (Poa ligularis, Nassella tenuis and Pappostipa speciosa). Location: Patagonian Monte, Chubut Province, Argentina (42°07′ S, 64°59′ W; 43°06′ S, 65°43′ W; 42°29′ S, 66°34′ W). Methods: We conducted two simultaneous microcosm experiments. In the first experiment, we sowed perennial grass propagules of the three species alone and combined with non‐scarified shrub propagules in Petri dishes with three substrate types (filter paper, inert soil and soil from shrub patches). In the second experiment, we sowed perennial grass propagules of each species combined with scarified and non‐scarified propagules of both shrub species in Petri dishes with soil taken from plant patches dominated by L. divaricata and by S. johnstonii. Both experiments lasted 3 months. We calculated the germination proportion and mean germination time (MGT) of propagules for each perennial grass species in each treatment. Results: Propagules from neighboring shrubs had a clearer negative effect on grass germination compared with shrub soils. Shrub propagules negatively affected the germination proportion of P. ligularis and N. tenuis, and induced longer MGT in the three perennial grass species. The combination of S. johnstonii soil and propagules negatively affected P. ligularis and P. speciosa germination. The combination of L. divaricata soil and scarified propagules completely inhibited P. speciosa germination. Conclusions: Our results highlighted the complexity of interactions between shrubs with high phenolic contents (soils and propagules) and the germination of perennial grass species in arid environments. Schinus johnstonii soil and propagules had stronger effects on perennial grass germination than L. divaricata soil and propagules. The negative effects of shrubs on microsite quality and germination processes depended on the specific shrub/grass interaction. [ABSTRACT FROM AUTHOR]

Question: Livestock grazing affects plant communities in drylands worldwide. However, our current understanding of the Patagonian drylands has primarily been derived from comparing exclosures with grazing conditions or from single‐site grazing gradients. The pending question is: do impacts of grazing intensification on Patagonian plant communities change along aridity gradients? Location: Patagonia, Argentina. Methods: We surveyed vegetation cover of perennial species in paddocks with different sheep‐grazing pressure (ungrazed, lightly, moderately, and intensively grazed, based on long‐term stocking rates), in three plant communities located along a regional aridity gradient: a semi‐desert (arid), a shrub–grass steppe (semi‐arid), and a grass steppe (dry sub‐humid). In these communities, we analyzed the effects of grazing pressure on the total cover of vegetation, the cover of dominant plant life‐forms (grasses and shrubs), the plant species diversity, and the traits of dominant plant species. Results: Intensification of sheep grazing significantly decreased total vegetation cover in the semi‐desert, but not in the steppes. Although grazing decreased the cover of grasses (particularly of the highly preferred ones) in all communities, in the shrub–grass and grass steppes this reduction was offset by an increase in the cover and size of shrubs. Plant diversity was not consistently affected by grazing pressure in these communities. Traits of dominant plant species partially explained community responses to grazing intensification. Conclusions: Livestock grazing intensification reduces the forage quantity and quality of Patagonian plant communities, but the severity depends on plant community types. In semi‐deserts (the most arid), grasses were drastically affected, while in the steppes, the grazing effects on grasses were low and partially compensated by an increase in the cover and size of shrubs, which fulfill critical roles other than forage provision. It is fundamental that grazing pressure be adapted to forage resource availability for each community type to achieve sustainable management in the context of climate change. [ABSTRACT FROM AUTHOR]

Copyright of Tropical Grasslands / Forrajes Tropicales is the property of International Centre for Tropical Agriculture - CIAT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Questions: What is the role of native and domestic herbivores in native–alien vegetation changes in sub‐Antarctic forests? Does herbivory suppression increase native while reducing alien species diversity? Location: Central–eastern Tierra del Fuego Island, Argentina. Methods: In four sites, we set up three different treatments: excluded grazing by livestock (cattle), by livestock and native (guanaco) herbivores, and grazed control plots in Nothofagus antarctica forests. We then monitored the dynamics of understorey native and alien plants (species richness, abundance) of dicots, monocots, and ferns over 6 years. Generalized Linear Mixed Models were used to determine the effects of herbivore exclusion and time on species richness and abundance. In addition, we calculated the abundance rate of change to quantify temporal dynamics. Results: Overall species richness did not change in the exclusion plots, but native and alien abundances were affected by herbivory and time since exclusion. The abundance of native monocots changed after herbivore exclusion, increasing its dominance significantly inside exclusion plots. However, the cessation of herbivory did not reduce alien species in general. Only alien dicots significantly declined in the livestock exclusion treatment. Further, we found that the two dominant alien grass species (Holcus lanatus and Poa pratensis) respond differently to grazing exclusion, and their response was modulated by forest basal area. Conclusions: Our results indicate that cattle and guanaco grazing had variable effects on native and alien plants, and that herbivore exclusion has a substantially positive effect on native grasses. However, the magnitude of temporal changes was more significant for vegetation richness and abundance than the effect of exclusion treatments. Herbivore exclusions can initiate a rapid recovery of compositional attributes of native vegetation in N. antarctica forests grazed by livestock. [ABSTRACT FROM AUTHOR]

Background and aims: The invasion of natural ecosystems by alien species represents a major concern in the context of global conservation. In the fields of Teyú Cuaré, in the department of San Ignacio, Misiones, there is a high level of endemism with at least eight species of microendemic vascular plants. These grasslands are considered the only Cerrado fragments present in Argentina and are being invaded by Melinis minutiflora (Poaceae). The aim of this work was to evaluate how this adventitious grass affects the composition and diversity of the vegetation, and to determine the progress in the period 2015-2017. M&M: To measure the impact, the vegetation was sampled using 25 random plots of 1x1m in areas with and without invasion. Phytosociological parameters and diversity indices were calculated. For the measurement of progress, perimeter walks were carried out with GPS. Results: We found that areas free of this exotic grass had a higher total number of species (81), and a higher number of species exclusively present only in these sites (51). The area analysis showed an increase from approximately 9,744 m² to 23,396 m². Conclusions: Our results indicate that the advance of M. minutiflora populations is vertiginous and that it exerts a significant pressure on grassland structure and diversity by occupying the ecological niche of native herbs and subshrubs. [ABSTRACT FROM AUTHOR]

Context: ​Defoliation management targets applied to forages under the full sun have not yet been properly evaluated for shaded environments such as occur in integrated crop–livestock systems with the presence of trees. Aims: This study aimed to determine defoliation targets under full sun and shaded environments for the shade-tolerant perennial summer grass hybrid Axonopus catharinensis (giant missionary grass), widely used in pasture systems of South Brazil and Argentina. Methods: Four pre-defoliation canopy heights (15, 25, 35 and 45 cm) and four defoliation severities (20%, 40%, 60% and 80% reduction in pre-defoliation canopy height) were evaluated. Plants were grown in 0.15 m3 wooden boxes filled with sand/vermiculite substrate (1:1 v/v) and irrigated with a complete nutrient solution. An artificial shade structure was made with wooden slats, reducing light intensity by 50% for shaded plants. Key results: Herbage accumulation decreased by 54% in shaded plants compared with those under full sun. Regardless of the light environment, the lowest crude protein content (<150 g/kg dry matter) and the highest neutral detergent fibre content (>650 g/kg dry matter) were observed when the defoliation target height was >35 cm. Both shaded and full sun environments showed decreases in tiller density when defoliation severity was >60% of pre-defoliation canopy heights. Conclusions: Pre-defoliation canopy heights >35 cm and defoliation severity >60% of pre-defoliation canopy height should be avoided when managing A. catharinensis , regardless of the light environment. Implications: Recommended targets may be easily implemented by livestock producers and are similar for full sun and shade environments. The advantages of integrated crop–livestock systems with the presence of trees mean that defoliation targets are needed to manage pasture in shaded environments. We assessed different pre- and post-defoliation targets for Axonopus catharinensis and found that this forage can be managed similarly in full sun and shade environments. Because the defoliation targets were based on canopy height and canopy defoliation proportion, recommendations for this species (<35 cm height, <60% defoliation) may be easily implemented by livestock producers. [ABSTRACT FROM AUTHOR]

Copyright of Annals of the Missouri Botanical Garden is the property of Missouri Botanical Garden Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Agriscientia is the property of Revista AgriScientia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The false Rhodes grasses [Leptochloa crinita (Lag.) P.M. Peterson and N.W. Snow and Leptochloa pluriflora (E. Fourn.) P.M. Peterson and N.W. Snow] are considered valuable native forage resources for arid and semiarid rangelands in Argentina and the United States. Effectively using plant materials as forage under aridity conditions requires understanding their resource allocation under those conditions. In the present study, plant functional traits were evaluated in six populations of each false Rhodes grass species from different geographic origin in a humid and an arid region. The evaluation was focused on seed weight, due to the key role of this trait in plant survival. The implication of seed weight in germination under osmotic stress and trade-off relationships between functional traits were also analysed. A fixed ontogenetic variation was found in both species, since populations maintained a stable seed weight across environments. The tolerance to osmotic stress at germination stage was more related to seed weight than to population origin or maternal environment of seeds; heavier-seeded populations produced heavier seedlings instead of a higher number of germinated seeds or higher germination rates. Some traits varied between environments but other traits exhibited a fixed response. Variation patterns among populations were similar within environments and in some cases even for populations from the same geographic origin, revealing a fixed ontogenetic variation; this phenomenon was clearer in L. crinita than in L. pluriflora. Moreover, several different trade-off strategies were detected in both species. These results reinforce the knowledge about the key role of seed weight in survival and performance of seedlings at initial growth stages under arid conditions; however, at advanced stages, other traits would have an important function in growth and development of false Rhodes grasses. [ABSTRACT FROM AUTHOR]

The objective of this study was to analyze the root distribution of grasses and shrubs, at different soil depths, in two ecological sites (ES): highland (forest) and lowland (grassland). The root density (RD) estimation was used as a proxy to test the two-layer hypothesis. Three trenches were dug in both ES and the number of roots m−2 was registered at different depth classes. The roots were classified in categories: (a) life forms (LF), grasses and shrubs and (b) root size (diameter): fine (<0.1 cm), small (0.11–0.5 cm); medium (0.51–1.5 cm) and large (>1.51 cm). Soil bulk density (Bd) was assessed by gravimetric method and its relation with RD was determined by regression analysis. RD was analyzed by using ANOVA with the factors: ES, LF, depth and root size. There were no significant differences in RD between the ES but RD significantly decreased with depth in both ES. In the upper horizons of the forest, there was higher shrubs RD (764 roots m2) than grass RD (128 roots m2) (p < 0.0001). In grassland, grass RD was registered in all the depths. Mean fine root density was greater than the mean of other root size categories. The relationship between RD and Bd was negative and only significant in the forest (p = 0.009). The distribution of roots of both LF in the soil profile of both ES did not respond completely to the two-layer hypothesis since in upper horizons an overlap was observed. [ABSTRACT FROM AUTHOR]

The Chaco wetland is among the most biologically diverse regions in Argentina. In collections of fungi from asymptomatic native grasses (Poaceae) from the wetlands, we identified isolates of Fusarium that were morphologically similar to F. armeniacum, but distinct from it by their production of abundant microconidia. All the isolates had identical, or nearly identical, partial sequences of TEF1 and RPB2. But they were distinct from reference sequences from F. armeniacum and Fusarium species closely related to it. Phylogenetic analysis of 34 full-length housekeeping gene sequences retrieved from whole genome sequences of three Chaco wetland isolates, 29 genes resolved the isolates as an exclusive clade within the F. sambucinum species complex. Based on results of the morphological and phylogenetic analysis, we concluded that the Chaco wetland isolates are a distinct and novel species, herein described as Fusarium chaquense, sp. nov., which is closely related to F. armeniacum. F. chaquense in culture can produce the trichothecenes T-2 and HT-2 toxin, neosolaniol, diacetoxyscirpenol, and monoacetoxyscirpenol, as well as beauvericin and the pigment aurofusarin. Genome sequence analysis also revealed the presence of three previously described loci required for trichothecene biosynthesis. This research represents the first study of Fusarium in a natural ecosystem in Argentina. [ABSTRACT FROM AUTHOR]

Copyright of Tropical Grasslands / Forrajes Tropicales is the property of International Centre for Tropical Agriculture - CIAT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Annals of the Missouri Botanical Garden is the property of Missouri Botanical Garden Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this work was to study the fungal diversity in Paspalum notatum, in order to determine the potential biological control of disease-causing pathogens and their effects on growth promotion. Two isolates of Cercospora dianellicola were identified from asymptomatic P. notatum leaves, as an endophytic species. The possible benefits for the host plant remain to be analyzed. [ABSTRACT FROM AUTHOR]

Land use has changed the original composition of the natural grasslands in the dry pampas of central Argentina, to the detriment of palatable perennial grasses (PPG). Long-term elimination of anthropogenic disturbances has not been enough to effectively recover the PPG, which suggests that availability of seeds and/or habitats may be limiting their recruitment. Therefore, our objectives in a degraded grassland site were to assess: (1) the germinable soil seed bank and (2) changes in botanical composition after addition of PPG seed following canopy disturbance. In autumn 2015, we randomly selected 10-paired plots, measured the aboveground biomass and took soil samples to assess the germinable soil seed bank. Afterwards, we disturbed the resident vegetation in each paired plot and either added PPG seeds or left the plot without any seed addition as a control. We quantified the seedling density of seeded and spontaneous species in the spring of 2015 and 2016, and the aboveground biomass at the end of 2017. Annual grasses and forbs (AGFS) dominated the soil seed bank, while PPG and unpalatable perennial grasses (UPG) occurred at low seed density and richness. Addition of PPG seeds resulted in the successful establishment of one key seeded PPG (Poa ligularis). In the spring 2017, the aerial biomass of PPG was highest in the seeded plots, where P. ligularis accounted for 94%. Our results showed that PPG were poorly represented in the soil seed bank of the degraded grassland and that disturbance of the resident vegetation combined with PPG seed addition enabled successful recruitment of a key PPG. So, enhancement of the pastoral value of degraded dry pampas grasslands would be possible through disturbance of the resident vegetation and addition of PPG seed. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is the main limiting factor for forage production in grasslands. It is important to determine levels of available P in soil that optimise production with minimum impact on arbuscular mycorrhizal (AM) symbiosis. We investigated the effects of increasing P availability on biomass production, root morphology, AM symbiosis and P acquisition of a forage legume (Lotus tenuis), a C3 grass (Schedonorus arundinaceus) and a C4 grass (Panicum coloratum) growing on a P-deficient soil in pots with P applied at rates of 0–160 mg kg–1 dry soil. The three forage species responded strongly to addition of P, with 90% of maximum shoot growth reached at available P levels of 24.3 mg kg–1 for L. tenuis , 14.4 mg kg–1 for P. coloratum and 11.2 mg kg–1 for S. arundinaceus. Lotus tenuis and P. coloratum produced higher yields of shoot biomass than S. arundinaceus. Root dry weight was higher in the legume than in the grasses, with the root-mass fraction being lowest in P. coloratum. AM colonisation was higher in L. tenuis roots than in grass roots, and decreased with increased soil P availability, especially in grasses. Low to moderate additions of P did not affect, and could even improve, AM colonisation in L. tenuis roots. For L. tenuis , it is possible to increase forage yield while maintaining high values of AM colonisation at 10–20 mg kg–1 of available P, but for grasses, especially S. arundinaceus , it is difficult to achieve both objectives. The presence of L. tenuis in grasslands or pastures may contribute to maintaining the native AM inoculum under a wide range of soil P availability in regions such as the Salado River basin of Argentina. Phosphorus (P) fertilisation is necessary to increase forage yield; however, levels of available P in soil ideally should optimise forage production while having minimum impact on arbuscular mycorrhizal (AM) symbiosis. In this study, low to moderate P doses improved forage growth of a legume and two grasses in a P-deficient soil, and could improve AM colonisation in Lotus tenuis roots. Availability of P should be accurately determined in a range of soils to improve the forage production and to maintain AM symbiosis. [ABSTRACT FROM AUTHOR]

In this study, we made an attempt to reveal how competition intensity from established plants impacts on palatable and unpalatable grass seedlings recruitment, in a natural mesic grassland of central Argentina. Our objective was to assess the seedling recruitment of a palatable species (Chascolytrum subaristatum) and an unpalatable species (Nassella trichotoma) in microsites differing in competition intensity from established plants. Identity (C. subaristatum and N. trichotoma) and defoliation severity were used as surrogate for competition intensity. In March 2017, we permanently marked established individuals of N. trichotoma and C. subaristatum and placed two circular plots adjacent to each individual. In one plot we added seeds of N. trichotoma and in the other seeds of C. subaristatum. After seeding, established plants were randomly assigned to one of three level of defoliation: without defoliation, low defoliation severity and high defoliation severity. From April to November 2017 (i.e. over a complete annual growing cycle), we measured seedling density, recruitment and growth. Our results supported the hypothesis that seedlings of palatable grasses are more competitive than seedlings of unpalatable grasses. Seedling of the palatable grass C. subaristatum recruited successfully regardless the intensity of competition from established plants, whereas seedlings of the unpalatable grass N. trichotoma recruited better under low competitive pressure from established plants. Our results suggest that the availability of microsites with low competitive pressure from the established vegetation, created by selective grazing of palatable grasses, promotes the recruitment of unpalatable grass seedlings. This mechanism may contribute to the species replacement process commonly observed in heavy grazed grasslands. [ABSTRACT FROM AUTHOR]

This report provides new data about the geographical distribution of some native species from nothern Argentina as Colletia spinosissima (Rhamnaceae), Pterocaulon balansae (Asteraceae) and Saccharum trinii (Poaceae). Based on the analysis of collection records, bibliographic records and on-line databases, the orographic System of Tandilia (also called "Sierras Septentrionales de Buenos Aires") is established as the southern limit of their range. We propose some possible causes of the presence of peripheral populations of these three species in this hilly system, such us climate change, anthropogenic factors and methodological absences. [ABSTRACT FROM AUTHOR]

Poa schizantha is a dioecious, psammophilous grass endemic to Atlantic coastal dunes in Argentina. We quantified the distribution area of this rare endemic species and characterized its habitat in the southern Pampas region. Convex hull and α-hull methods were used to estimate and map its overall geographical range. Ecological characterization was based on location, environmental variables, floristic composition and vegetation cover. In total, 117 quadrats were sampled in spring. The convex hull (7553 ha) was split, after excluding discontinuities, into two polygons: area 1 (968 ha; a novel area for the species) and area 2 (449 ha) separated by 36 km, indicating two geographically distinct population groups. In active coastal dune fields, P. schizantha occurs mainly in interdune slacks, associated with herbaceous, short, grassland-type vegetation and moist sandy soils with low vegetation cover, suggesting high habitat specificity. Based on TWINSPAN classification and ordination analysis, P. schizantha is related to two main vegetation groups with 100% constancy and c. 30% relative importance: subgroups E (dominated by pioneer dune species) and F (associated with hygrophilous and ubiquitous species). Given the extent of occurrence (restricted to < 100 km2) and the severely fragmented habitat condition, we propose the species be categorized as Critically Endangered, following IUCN criteria. Actions aimed towards the survival of this species must prioritize population monitoring and conservation of its dune habitat. [ABSTRACT FROM AUTHOR]

Woody species can exert positive, neutral or negative influence on the growth of neighbouring grass species. The objective of this work was to assess the impact of woody species (Prosopis caldenia and Larrea divaricata) on aboveground biomass production and quality of perennial grasses (Piptochaetium napostaense and Nassella clarazii). Overall, aboveground biomass production of P. napostaense was higher in the area of influence of L. divaricata while that of N. clarazii was higher in the area of influence of P. caldenia. In general, P. napostaense showed higher, while N. clarazii showed lower, values of aboveground biomass production when beneath the canopy of each woody species. At the end of the vegetative growing period, crude protein content (CP) of grass species was lower beneath the canopy of woody species than in open areas; the only exception being N. clarazii in the area of influence of P. caldenia where no differences were found. No differences were found in CP content between any of the experimental locations at the end of the reproductive growing period. In general, in vitro digestibility was lower within the area of influence of P. caldenia than of L. divaricata for both growing periods. The results of the present study suggest that the impact of woody species on aboveground biomass production and quality are species-specific in semi-arid rangelands of central Argentina and highlight the need of further research in order to prescribe sound and generalized shrub management policies. [ABSTRACT FROM AUTHOR]

Festuca is a genus of the Poaceae family with about 140 species in South America. Little information is available about Festuca species growing in the Eastern Sierras Pampeanas in Argentina, a region with a significant degree of endemism. The taxonomic delimitation of some species of this region is imprecise. One such taxon is Festuca lilloi, which has not only been recognized as a native species of the Peruvian Andes or endemic to the Western Sierras Pampeanas (northern Argentina), but also as a dominant floristic element in the Eastern Sierras Pampeanas (central Argentina). In spite of its ubiquity, there is very little information on variation in its morphology, anatomy and ecology across the Sierras Pampeanas and in adjacent areas. Recent fieldwork has resulted in the finding of a new species of Festuca that was erroneously assigned to Festuca lilloi. Morphological and anatomical differences between F. lilloi and the close species are evaluated, as are the species' ecological preferences. The delimitation of the new species, named here as Festuca giraldoi, follows the morphological species concept. A detailed description of the morphology, leaf anatomy and epidermal micromorphology (leaf and lemma) is provided for the new species. [ABSTRACT FROM AUTHOR]

Bahiagrass (Paspalum notatum Flüggé) is the base of cow‐calf operations in Florida. Nitrogen is usually the most limiting mineral in pasture‐based systems. Various bahiagrass cultivars have been released over the years; however, an evaluation of their performance under no N fertilization has not been reported. There is some evidence that bahiagrass can associate with free‐living bacteria and fix atmospheric N2. This study investigated the performance and potential biological N2 fixation (BNF) of six bahiagrass cultivars ('Argentine', 'AU Sand Mountain', 'Pensacola', 'TifQuik', 'Tifton‐9', and 'UF‐Riata') under no N fertilization during the growing seasons of 2014, 2015, and 2016. Results showed no differences among cultivars for total herbage accumulation (2835 kg dry matter ha−1), total N aboveground (28 kg N ha−1 yr−1), and BNF (9 kg N ha−1 yr−1). Pensacola had greater crude protein than Tifton‐9 (84 vs. 78 g kg−1, respectively), whereas AU Sand Mountain had greater in vitro digestible organic matter (494 g kg−1) than other cultivars, except for Argentine. Argentine had greater root‐rhizome mass (24,914 kg organic matter ha−1) than UF‐Riata and TifQuik (15,367 and 14,682 kg organic matter ha−1, respectively). Carbon and N stocks in belowground biomass were greater in Argentine (8575 and 155 kg ha−1, respectively) than UF‐Riata (4514 and 85 kg ha−1, respectively). Root‐rhizome/shoot ratio averaged 37 across cultivars. Managing bahiagrass cultivars under no N fertilization inhibits the cultivar herbage potential; however, cultivar differences in nutritive value and root‐rhizome responses can still be detected. [ABSTRACT FROM AUTHOR]

Aims: Silicophytoliths contribute to the pool of amorphous silica that is incorporated into the soils acting as intermediary in the biogeochemical cycle of silicon. Most studies focus their attention in the production of aerial parts of plants but not in roots. In order to advance into the knowledge about the relevance of root amorphous silica in soil Si cycle, we studied the silicophytolith content of roots from grasses and crops, and from soil's roots of different sites from Pampean region, Argentina, one of the most fertile and used for agricultural practices. Methods: Roots from three crops and seven grasses and from soils under three different uses were studied. Silicophytoliths were extracted by a calcination technique. Results: All the species produced silicophytoliths derived from vascular and/or endodermal tissues. Silicophytolith content was higher in Pampean grasses (6.34–15.38%) than in crops (0.01–1.58%). Root silicophytolith content in the pasture was 10 times higher than in the other sites. Conclusions: The potential input of root silica to soils is related to the type and cover of vegetation, the amount of roots in soils and the silicophytoliths accumulated in roots. Results suggested that root silicophytoliths should be consider in future studies of biogeochemical cycle of Si. [ABSTRACT FROM AUTHOR]

Steppes and grasslands of semiarid environments in the Central Andes are poorly understood in fossil records due to the lack of modern pollen–vegetation studies. This paper is focused on a systematic analysis of the modern pollen–vegetation relationship in three protected areas of the Puna in Jujuy, northwestern Argentina. Vegetation assemblages were described on the basis of their floristic composition in 32 plots. Different multivariate methods, indices of association and simple linear regression models were applied in order to investigate the degree to which the different vegetation assemblages can be distinguished by their pollen spectra. Five plant assemblages were described, which were partially represented by their pollen spectra: mixed and shrubby steppes, scrubland, grassland with shrubs and high Andean grassland. The pollen spectra reflected both altitudinal variations and environmental conditions. In the Puna belt, at 3600 m, shrubs were present in great abundance and their highest pollen percentages were recorded. Both the abundance of Poaceae herbs and their pollen type increased with increasing altitude up to 4220 m, indicating the transition towards the Altoandean belt. Pollen assemblages evidenced the following environmental conditions: (1) the temperature decrease is characterized by taxa adapted to either cold air (<7 °C) or cold soil (Aridisols-Cryids/Inceptisols-Ustepts type) including Poaceae, Frankenia triandra, Apiaceae, Hoffmansegia glauca, Ephedra, Caryophyllaceae; (2) moisture availability in the soil can be discernible by assemblages indicating dry soil (Aridisols-Durids type), such as Baccharis, Fabiana densa, Maihuniopsis boliviana, Fabaceae, Tetraglochin cristatum and Nassauvia axilaris, from those indicating humid soil (Entisols-Psaments type), such as Parastrephia, Astragalus garbancillo and Gentianaceae. Four taxa exhibited both a good association and a significant correlation and could be considered indicative of the steppe (Baccharis and M. boliviana), scrublands (Parastrephia) and grassland (Poaceae) in a fossil record. This work has important implications for interpreting the dynamics of vegetation during the Holocene in the Puna. [ABSTRACT FROM AUTHOR]

Sudangrass, Sorghum sudanense (Piper) Stapf, is a vigorous forage crop that has also been used for biogas, paper, and electricity production. Due to the large biomass yields achieved by sudangrass and the large area of potential growth in Argentina seven sudangrass accessions from a collection of S. sudanense were analyzed to evaluate their potential as feedstocks for lignocellulosic bioethanol production, and to assess whether there is an association between the response to biotic and abiotic stresses and the composition of the biomass. The biomass composition was analyzed for major cell wall polymers, monosaccharides, and elemental composition. On average, 68% of stem lignocellulosic biomass was comprised of matrix polysaccharides and crystalline cellulose, representing a potential source of sugars for bioethanol production. Xylose was the predominant matrix polysaccharide monosaccharide comprising, on average, 45% of the total sugars, followed by arabinose, glucose, galactose, galacturonic acid, mannose, glucuronic acid, and fucose. Rhamnose was not detected in any of the biomasses analyzed. Silica was the most abundant element in sudangrass stem, followed by chloride, calcium, phosphorus and sulfur. We performed saccharification analyses after pretreatments. Alkaline pretreatment was more effective than water pretreatment. Sodium hydroxide pretreatment exposed different levels of recalcitrance among sudangrass accessions, whereas the water pretreatment did not. Phenological traits were also evaluated, showing significant variability among accessions. The comparison of major cell wall polymers and monosaccharide composition between tolerant and susceptible accessions to abiotic and biotic stresses suggests an association between the composition of the biomass and the response to stress. [ABSTRACT FROM AUTHOR]

In Patagonia, arid and semiarid lands are being affected both by inappropriate management practices, which are leading to degradation, and by volcanic activity, whose effects are still unclear. This study aimed to test whether superficial deposition of volcanic tephra could benefit two of the most prominent Patagonian forage grass species (Poa ligularisandPappostipa speciosa var. speciosa). Pots withP. ligularisandP. speciosawere kept under wet (W) and dry (D) conditions in the presence (T+) or absence (T−) of tephra for 105 days, and then were all well-watered. We determined the effects of tephra on soil water retention and conservation, soil moisture content (% v/v), plant growth, stomatal conductance (gs), andgsrecovery capacity. The water regime significantly affected both species performance andgs. The presence of tephra increased soil water conservation, soil moisture content in wet conditions, andP. ligularis gsin wet conditions, and decreased senescence in dry conditions (9% inP. ligularisand 16% inP. speciosa). The presence of tephra allowed roots to grow in 8/10 and 2/10 pots inWconditions forP. ligularisandP. speciosa, respectively, and in only 1/10 pots inDconditions, only forP. ligularis. Tephra was also associated withgsrecovery after dry conditions.Poa ligulariswas more positively affected by tephra thanP. speciosa, probably becauseP. ligularishas higher phenotypic plasticity. The positive effects of tephra may increase the resilience and resistance ofP. speciosaandP. ligularisto periods of water shortage. [ABSTRACT FROM AUTHOR]

The article is an obituary in memory of Dr. Carlos María Ferri, who passed away in June 2021 in Santa Rosa, La Pampa, Argentina. Dr. Ferri was an outstanding professional and individual in the academic community of the Faculty of Agronomy at the National University of La Pampa. He was born in Realicó, La Pampa, and obtained his degree as an Agricultural Engineer from UNLPam. He conducted research on the forage evaluation of perennial summer grasses and was recognized for his academic excellence and commitment to teaching. Additionally, he held important management positions in the faculty and left an indelible mark as a dedicated and studious person. [Extracted from the article]

The aim of this study was to evaluate the occurrence of several fungal metabolites, including mycotoxins in natural grasses (Poaceae) intended for grazing cattle. A total number of 72 and 77 different metabolites were detected on 106 and 69 grass samples collected during 2011 and 2014, respectively. A total of 60 metabolites were found across both years. Among the few mycotoxins considered toxic for ruminants, no samples of natural grasses were contaminated with aflatoxins, ochratoxin A, ergot alkaloids, and gliotoxin, among others. However, we were able to detect important metabolites (toxic to ruminants) such as type A trichothecenes, mainly T-2 toxin and HT-2 toxin (up to 5000 µg/kg each), and zearalenone (up to 2000 µg/kg), all at very high frequencies and levels. Other fungal metabolites that were found to be prevalent were other Fusarium metabolites like beauvericin, equisetin and aurofusarin, metabolites produced by Alternaria spp., sterigmatocystin and its precursors and anthrachinone derivatives. It is important to point out that the profile of common metabolites was shared during both years of sampling, and also that the occurrence of important metabolites is not a sporadic event. Considering that this area of temperate grassland is used for grazing cattle all year long due to the richness in palatable grasses (Poaceae), the present work represents a starting point for further studies on the occurrence of multi-mycotoxins in natural grasses in order to have a complete picture of the extent of cattle exposure. Also, the present study shows that the presence of zeranol in urine of beef cattle may not be a consequence of illegal use of this banned substance, but the product of the natural occurrence of zearalenone and a-zearalenol in natural grasses intended for cattle feeding. [ABSTRACT FROM AUTHOR]

Aculodes Keifer (Eriophyidae) mites are often associated with grasses (Poaceae) and so far all species in this genus were described from the Northern hemisphere. During surveys of eriophyid mites from grasses conducted in Argentina aiming to determine the host range of the wheat curl mite, a new Aculodes species was collected from the feather grass, Stipa sp. The first Aculodes species is described from the Southern hemisphere. In addition to the traditional morphological description, DNA sequences of two genomic regions – the ITS rDNA and the 16S region mtDNA– were obtained and deposited in public databases; genetic distances of the new taxon with eriophyid species/genera associated with grasses are presented. In order to contribute to Aculodes taxonomy, a list for world grasses-associated species is provided and information on its morphological traits is summarized. [ABSTRACT FROM AUTHOR]

Sporobolus phleoides is an endemic grass of Argentina considered an important genetic resource for saline environments due to its salinity tolerance. Basic information about its reproductive biology is needed to adequately preserve its genetic variability. Hence, we studied its breeding system through phenology, embryological analysis, and self-pollination versus open-pollination treatments in six populations collected from four provinces of Argentina. The results indicated that S. phleoides is mainly autogamous with a high fertility rate. Cleistogamous and chasmogamous spikelets are isomorphic and occur simultaneously on the inflorescence, with higher percentages of cleistogamy found in the basal region of the panicle. The average percentage of cleistogamy during the study period was 23 % for all populations evaluated. The development of the embryo sac follows the typical pattern of grasses and indicates normal sexual reproduction. This study provides the basis for programming genotype collections for gene banks and future plans of domestication. [ABSTRACT FROM AUTHOR]

The article presents research on the discovery of new genus Morronea. Topics covered include the segregation of the genus from Panicum, number of species in the genus and proliferation in Mexico and Argentina. Also mentioned are the length of its spikelet, description of palea and absence of lower flowers.

In the region of "Espinal", Calden Distrct in the province of San Luis there is a strong agriculturization process with the consequent loss of native forest remnants, conserving endangered native species and invasion of exotic species. The aim of this study was to evaluate the effect of the stripe clearing on 6 species of caldenal (4 grasses and 2 broadleaves). The study was conducted in a field 15 km to the north of the city of Villa Mercedes (San Luis), subjected to a strip-clearing for agricultural use, in the year 2003. On 5 sites into native forest remnants stripes and 5 into without clearing native forest, 39 m long transects were laid, N-S direction, and along the same were recorded the presente species in 14 sampling units of 1 m². Data were analyzed by IBM SPSS Statistics 19, through nonparametric methods, Mann-Whitney U. Statistical analysis showed significant differences (p <0.05) in Digitaria californica, Pappophorum pappiferum, Salsola kali and Cestrum parqui. The study showed that the cultivation of native forest between stripes was a change in the frequency of native grasses and broadleaves. [ABSTRACT FROM AUTHOR]

Grasses morphological knowledge, in space and time, is important in agronomic management actions. Bothriochloa laguroides is a key species in the grasslands of the hills region by higher prevalence of high forage value. The objective was to establish management guidelines to define more precisely the grazing intensity for that species. In a area of 95 ha, grazed breeding farm, were placed randomly distributed 4 closures. In every closing we selected 5 individuals of that species and every 7 days was measured total plant height (AT) and the height of the peduncle of the inflorescence visible (APVI) in both vegetative and reproductive stage. According to the results obtained showed that the growing period was maintained until mid-January. The start, peak and end of flowering occurred in mid- January, late February - early March and late April respectively. On the other hand, there was a significant positive correlation (R = 0.8, α = 0.05) between AT and APVI. As a result, it could be recommend that grazing in the vegetative stage is of low intensity to favor the formation of bunches. From mid-January, when starts the reproductive stage, grazing may be of greater intensity until early March which should remove the animals. This management would have a large supply of biomass to ensure the perpetuity of the species in time. [ABSTRACT FROM AUTHOR]

Abstract: Shallow-rooted grasses and deep-rooted shrubs dominate arid ecosystems where nitrogen is concentrated in the upper layers of the soil and water is distributed throughout. Analysis of mineral nitrogen and absorption patterns using a tracer indicated that shrubs in Patagonia absorbed nutrients from the lower, relatively nutrient-poor layers of the soil. Are they, consequently, at a competitive disadvantage with grasses that have the opposite pattern? Studies of nitrogen economy indicated that shrub and grass species have similar N-use efficiency but that they achieve it through opposite mechanisms. Shrubs have a conservative N economy absorbing annually only small fraction of their N content, whereas grasses have a more open N economy. This study about N-capture strategies in conjunction with previous studies about water-use by shrubs and grasses in the Patagonian Steppe suggest a coupling of N and water-capture strategies. Our findings have implications for the response of arid and semiarid ecosystems to global warming, nitrogen deposition, and biodiversity change. For example, climate change scenarios predict, for most arid regions, decreases in moisture availability that will result in a reduction in deep water, which in turn will reduce shrub density and result in a less conservative nitrogen economy. [Copyright &y& Elsevier]

Guadua tagoara subsp. tagoara is reported for the first time in Argentina, it is described and illustrated. A map showing its geographical distribution in South America and a key to the species and subspecies in Argentina are also provided. A lectotype for Bambusa distorta is here designated. [ABSTRACT FROM AUTHOR]

Abstract: Grazing by domestic exotic herbivores on native vegetation in Patagonian steppes has led to the deterioration of forage resources, where grasses are replaced by shrubs, and preferred grasses by non-preferred ones. Therefore, attempts at breeding and regeneration should start by identifying species with potential forage capability. Two perennial high-preferred species are the focus of this paper: Hordeum comosum and Koeleria vurilochensis. For the first time, we studied their morphological traits, dormancy level, and their temperature and water germination requirements, through thermal- and hydrotime models. H. comosum seeds were solid, large and heavy, while K. vurilochensis seeds were soft, small and light. Neither light-quality nor alternating temperature affected the dormancy level in seeds of both species. Seeds of H. comosum and K. vurilochensis required, respectively, 768.74 °Ch and 2217.89 °Ch to germinate; alternatively, base temperature was higher for H. comosum than for K. vurilochensis. The hydrotime required by H. comosum was 26 MPah and 110 Mpah for K. vurilochensis but, base water potential was −0.99 MPa and −1.45 MPa, respectively. For all the conditions, H. comosum displayed a higher germination rate compared to K. vurilochensis seeds. Deeper knowledge on the morphological and germination traits of seeds is a key step toward breeding and restoration of forage potential species. [Copyright &y& Elsevier]

Abstract: The understanding of modern pollen is a critical component of palaeoecological research. The pollen assemblages reflect general patterns in vegetation distribution; however, pollen representation is biased by several factors such as differences in pollen production, dispersal and preservation. Therefore, this relationship cannot be applied directly in pollen records of the past. The aim is to study the relationship between modern pollen and vegetation and to apply this new information on the interpretation of Holocene pollen records. Classification of the vegetation into groups corresponding to different geomorphological units was carried out by cluster analysis. Discriminant analysis was applied on the surface samples to test if different vegetation types could be distinguished by their pollen assemblages. To evaluate the relationship between pollen assemblages and vegetation types, association (A), under-representation (U) and over-representation (O) indexes were calculated for all present taxa in both plant and pollen dataset. The main vegetation types are reflected in pollen assemblages but with greater differences in the proportions of Poaceae, Hyalis argentea, Chenopodiaceae, Asteraceae subf. Asteroideae and Larrea divaricata. Association and representation indexes provided information related to the production rate and pollen dispersal. This study helps to interpret Holocene vegetation and environmental changes from fossil pollen records of the study area. [Copyright &y& Elsevier]

Abstract: We analyzed the structural differences associated with grazing exclusion on vegetation by studying 24 grazed–ungrazed paired sites in Patagonia (Argentina). Our objectives were to evaluate the effect of grazing on plant species composition, plant diversity, the relative abundance of plant functional types, and the vertical and horizontal structure of the plant community. This study across the shrub-grass steppes of Patagonia highlights some important characteristics of the vegetation response to a major disturbance factor we show that shrub encroachment is not a generalized response of the steppe to grazing. Grazed areas presented lower richness and diversity than exclosures. Physiognomic changes (as describe by relative abundance of plant functional types) were less important than those observed at the species level. These results shown that the status of the shrub-grass steppes of the Occidental district of Patagonia can not be characterized in terms of contrasting physiognomic states as in the case of the grass steppes of the Subandean district. Forbs and a few mesophytic and xerophytic grasses are the key elements to identify the condition of the steppe. Monitoring programs should focus on the relative abundance of these components. [Copyright &y& Elsevier]

The article presents a study that provides description and illustration of a new species of Merostachys from the Bolivian Yungas, Merostachys yungasensis. It offers comparison of merostachys yungasesis with other taxa distributed in Argentina, Bolivia, Paraguay, and Peru. It recognizes two new synonyms for M. claussenii and is found to be from Paraguay.

The species in the Sporobolus indicus complex are analyzed for Argentina. Sporobolus indicus var. indicus and S. indicus var. andinus are recognized for Argentina based on significant value differences in culms height and inflorescence length, and the altitude of collection area. The var. andinus is a new record for the Argentinean flora and it is here illustrated. Sporobolus jacquemontii is excluded from Argentina and S. minor is considered as a synonymy of S. indicus var. indicus. [ABSTRACT FROM AUTHOR]

During the revision of the Stipeae (Poaceae) for the Argentinean flora and in accordance to the latest phylogenetic studies in the tribe, it became necessary to transfer some recently described taxa from the genus Stipa to Nassella, Jarava or Pappostipa. As a result, 12 new combinations are here proposed: Jarava ichu var. pungens, Nassella brachyglumis, N. macrotricha, Pappostipa arenicola, P. choconensis, P. colloncurensis, P. frigida var. longifolia, P. jucunda, P. kieslingii, P. mapuche, P. marqueziana and P. zulmae. A key to identify the genera of Stipeae in Argentina is also included. [ABSTRACT FROM AUTHOR]

In grasslands composed of C3 and C4 plants, a different pattern of response by the two photosynthetic types to fertilizer may change the floristic composition of the community. In this study, we evaluated the effects of an application of nitrogen (N) and phosphorus (P) fertilizer at two dates in the spring on the aerial growth of C3 and C4 grasses. Danthonia montevidensis and Stipa neesiana (C3), and Setaria geniculata and Sporobolus indicus (C4), were selected from a native grassland of the Flooding Pampa, Argentina. Two consecutive experiments (early and late spring) were conducted in pots filled with the local soil. The C3 grasses showed no response in aerial biomass, and only minor responses in aerial concentrations of N and P, numbers of leaves and tillers, and nutrient use efficiency to an application of P or N fertilizer. In contrast, their C4 counterparts showed a consistent positive response. C4 species performance was considerably influenced by date of fertilizer application in the spring. There was on average a 1·8 and a 2·5 increase in aerial biomass in early and late spring, respectively, to fertilizer application. The later date in spring was associated with higher ambient temperatures and it appeared that temperature rather than fertilizer application was the main limiting factor for C3 species. It was concluded that the positive response in C4 species to an application of P and N fertilizer indicates that the differences between C3 and C4 species were related to a higher demand to sustain greater growth rates in C4 species. [ABSTRACT FROM AUTHOR]

According to Article 53 of the ICBN Code, the epithets marcocarpum and macrocarpon must be considered mandatory homonyms. Sisyrinchium macrocarpum Hieron was published in 1881, S. macrocarpon E.E Bicknell in 1901. The latter is therefore illegitimate by virtue of the rule of priority. It may be found as a recognised epithet in current botanical science, and so is replaced here by the new name, S. magnicapsulare. [ABSTRACT FROM AUTHOR]

Abstract: In arid environments, soil fertility exhibits a high degree of spatial and temporal heterogeneity, which results from high climatic variability seasonally and heterogeneous plant distribution. However, because most desert areas have been altered by human activities, heterogeneous fertility would originate from grazing or logging activities. We evaluated spatial and temporal heterogeneity of soil fertility in cattle-excluded sites under and outside woody plant cover (Prosopis flexuosa and Larrea divaricata), and in sites disturbed by tree removal during wet and dry season in Ñacuñán Biosphere Reserve (Central Monte desert of Argentina). Soil organic matter, fulvic acids, bioavailable organic matter, and nitrate were lower outside plant canopy (8.9mgg−1, 0.03mgg−1, 8.2mgg−1, and 4.17mgkg−1, respectively). Total N, humic acids, and abundance of microbial functional groups did not show differences among sites. Most parameters differed between seasons, tending to be higher in the wet season. Overall soils of Ñacuñán Reserve are characterized by: a) more homogenous spatial pattern than expected from woody plant presence; b) very heterogeneous temporal pattern; and c) after two years, tree removal does not seem to induce infertile soil formation. [Copyright &y& Elsevier]

The article assesses the impact of major stresses on grass and shrub responses in Argentina. Major environmental impacts in the phytogeographical region known as Caldena include the replacement of palatable grasses and the conversion of extensive areas dominated by grasses to a shrubland. Particular focus is given on major concerns about desertification in the region and the implication of vegetation reduction on animals. It was concluded that the introduced livestock selected diets to meet their nutrient needs by grazing a variety of plants.

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Seed germination and seedling emergence are key processes for population recruitment. Flooding and grazing are disturbances forming gaps that may strongly influence recruitment patterns in space and time, but their combined effects and action mechanisms have rarely been addressed. In this study we analysed the effects of microhabitat conditions associated with winter flooding and spring-summer defoliation on seed germination and seedling establishment of Paspalum dilatatum, a dominant perennial C4 grass in native grasslands of the Flooding Pampa, Argentina. The dynamics of seedling emergence from natural seed banks and buried seeds was studied in a factorial experiment with flooding and defoliation treatments applied to soil monoliths (mesocosms) collected from natural grassland. Additional laboratory experiments were applied to investigate seed germination under different combinations of temperature, light quality and simulated flooding. Seed germination and seedling emergence of P. dilatatum were promoted by flooding and high intensity defoliation. Gaps generated by flooding were maintained by high intensity defoliation exercising a synergistic effect on survival seedlings. Flooding resulted in the breaking of seed dormancy and higher germination rates associated with alternating temperature and the activation of the phytochrome system. Our results indicate that microhabitat conditions associated with the disturbances forming gaps, such as flooding and heavy grazing, synergistically promote the recruitment process of this dominant grass species. [ABSTRACT FROM AUTHOR]