Background： Understory plants represents the largest component of biodiversity in most forest ecosystems and plays a key role in forest functioning.Despite their importance, the influence of overstory-layer compositi...Background： Understory plants represents the largest component of biodiversity in most forest ecosystems and plays a key role in forest functioning.Despite their importance, the influence of overstory-layer composition on understory plant diversity is relatively poorly understood within deciduous-evergreen broadleaved mixed forests.The aim of this work was to evaluate how tree overstory-layer composition influences on understory-layer diversity in three forest types（monospecific deciduous Nothofagus pumilio（Np）, monospecific evergreen Nothofagus betuloides（Nb）, and mixed N.pumilio-N.betuloides（M） forests）, comparing also between two geographical locations（coast and mountain） to estimate differences at landscape level.Results： We recorded 46 plant species： 4 ferns, 12 monocots, and 30 dicots.Canopy-layer composition influences the herb-layer structure and diversity in two different ways： while mixed forests have greater similarity to evergreen forests in the understory structural features, deciduous and mixed were similar in terms of the specific composition of plant assemblage.Deciduous pure stands were the most diverse, meanwhile evergreen stands were least diverse.Lack of exclusive species of mixed forest could represent a transition where evergreen and deciduous communities meet and integrate.Moreover, landscape has a major influence on the structure, diversity and richness of understory vegetation of pure and mixed forests likely associated to the magnitude and frequency of natural disturbances, where mountain forest not only had highest herb-layer diversity but also more exclusive species.Conclusions： Our study suggests that mixed Nothofagus forest supports coexistence of both pure deciduous and pure evergreen understory plant species and different assemblages in coastal and mountain sites.Maintaining the mixture of canopy patch types within mixed stands will be important for conserving the natural patterns of understory plant composition in southern beech mixed forests.展开更多
Evolutionary genetics of invasive species has been unexplored in Argentina. Invasive alien species (IAS) have a wide geographical distribution, characteristic life cycles and great ability to adapt, establish and spre...Evolutionary genetics of invasive species has been unexplored in Argentina. Invasive alien species (IAS) have a wide geographical distribution, characteristic life cycles and great ability to adapt, establish and spread in a new environment. Recent advances in novel molecular technologies, the use of higher resolution genetic markers, and the research development on genetic variation of invasive species consolidated the importance of genetic aspects in the invasion process. Undoubtedly, the growing concern for the disturbances generated by invasive species on biodiversity and functioning of ecosystems was also determinant for the inclusion of the Invasion Biology within the broad field of Evolutionary Biology including relevant examples that address the evolutionary genetic aspects of biological invasions. Recent studies suggest that the invasion success of many species depends on their ability to respond to natural selection. Although the number of invasive species registered in Argentina far exceeds 600, little research has been done on invasive mammal species and only five of them were hitherto genetically analyzed. Presuming that invasion genetics is incorporated into the agenda of control and management organizations, it would allow integrating the ecological, genetic, and evolutionary biology aspects for knowledge of invasive species widely distributed in Argentina. The objective of this article is to highlight the importance of evaluating the genetic structure of invasive species for their management and to inform about the invasive species of mammals that were introduced in Argentina and have been or are being analyzed genetically.展开更多
Under the present changing climate conditions and the observed temperature increase,it is of high importance to understand its effects on aquatic microbial life,and organisms’adaptations at the biochemical level.To a...Under the present changing climate conditions and the observed temperature increase,it is of high importance to understand its effects on aquatic microbial life,and organisms’adaptations at the biochemical level.To adjust to temperature or salinity stress and avoid cell damage,organisms alter their degree of fatty acids(FAs)saturation.Thus,temperature is expected to have strong effects on both the quantity and quality of FAs in aquatic microorganisms.Here we review some recent findings about FAs sensitivity to climate change in contrasting environments.Overall,heat waves may induce changes in the relative abundance of polyunsaturated FAs(PUFA).However,the impact of the exposure to warming waters is different in temperate and polar environments.In cold marine waters,high concentration of omega-3(ω3)FAs such as eicosapentaenoic acid(EPA)is promoted due to the activation of the desaturase enzyme.In this way,cells have enough energy to produce or activate antioxidant protection mechanisms and avoid oxidative stress due to heat waves.Contrastingly,under high irradiance and heat wave conditions in temperate environments,photosystems’protection is achieved by decreasing EPA concentration due to desaturase sensitivity.Essential FAs are transferred in aquatic food webs.Therefore,any alteration in the production of essential FAs by phytoplankton(the main source ofω3)due to climate warming can be transferred to higher trophic levels,with cascading effects for the entire aquatic ecosystem.展开更多
The Quaternary infilling of a circular structure located in Bajada del Diablo,Chubut Province,Argentina has been proposed as a crater strewn field in previous studies.Here we report the finding of about 65 microspheru...The Quaternary infilling of a circular structure located in Bajada del Diablo,Chubut Province,Argentina has been proposed as a crater strewn field in previous studies.Here we report the finding of about 65 microspherules collected in a trench excavated in the center of the structure.The majority of handpicked specimens are single,but some of them exhibit compound forms.The single specimens are spherical with a mean size of 137 nm,whereas the more complex samples show peduncles and drop shapes.Dendritic crystal growth is recognized in the internal structure of some broken microspherules.Preliminary chemical composition from the surface and center of microspherules was determined by energy dispersive spectrometry employing EDS.Quantitative EMPA and XRD analysis indicate that the microspherules are mainly composed of Fe and O with magnetite,Fe0with subordinate wiistite.Following consideration of possible anthropogenic and volcanic origins,these spherulites are ascribed to an extraterrestrial input.An accumulation rate of 47 microspherules per m2/yr is estimated for the studied sediments.This value is two orders of magnitude higher than the reference flux for cosmic dust estimated for the last 1 Ma in the Transantarctic Mountains.The microspherules might have been generated as a byproduct of asteroid entry in the atmosphere.展开更多
Background Ushuaia City has experienced much population growth and still lacks secondary treatment for its wastewater.As a result,most of the discharge is directed into the lotic ecosystems that cross the urban enviro...Background Ushuaia City has experienced much population growth and still lacks secondary treatment for its wastewater.As a result,most of the discharge is directed into the lotic ecosystems that cross the urban environment.This paper assesses the relationship between riparian areas and water quality along an urbanization gradient in the city's main watersheds:Pipo River,Buena Esperanza Stream and Arroyo Grande River.Results The Riparian Forest Quality Index adapted for Patagonia showed a positive correlation with the Fuegian Water Quality Index(r=0.83,p<0.05).Differences in the riparian index along the urban gradient were detected in all the studied watersheds.In general,non-urbanized sites in the upper zones showed very good or good quality while urbanized sites showed worse riparian conditions.Furthermore,in relation to the Fuegian Water Quality Index,this work showed spatial and temporal variations.The Pipo River watershed showed no statistically significant differences among sampling sites,although water quality decreased over time at the urbanized site near the outlet of the river(in March 2018 the Fuegian Water Quality Index was 88 and in March 2022 it was 38).In the Buena Esperanza Stream,significant differences were detected among sampling sites;water quality at the non-urbanized zones in the upper section and upper-middle section was higher than at the urbanized sites.In the Arroyo Grande River,despite the lower ranges of the Fuegian Water Quality Index observed at the urban site near the outlet,no significant differences were identified between study sites.Conclusion The relationship of both indices supports the relevance of the environmental surroundings of the watercourses and how their ecological integrity affects water quality in urban lotic ecosystems.The watersheds studied here are strongly linked to the complex dynamics of a growing city which was reflected by the Fuegian Water Quality.Our findings provide a scientific foundation for sustainable environmental management.We recommend integrated water resources management that not only ceases the direct discharge of wastewater into watercourses but also implements measures to protect and restore the riparian environment as a fundamental measure for the conservation of urban lotic ecosystems.展开更多
Introduction:Variation in reproductive phenology among species is an important mechanism for maintaining species coexistence.In mixed forests,the impact of limiting(biotic and abiotic)factors on tree reproductive succ...Introduction:Variation in reproductive phenology among species is an important mechanism for maintaining species coexistence.In mixed forests,the impact of limiting(biotic and abiotic)factors on tree reproductive success regulates the maintenance of species in balanced proportions or the conversion towards monospecific forests.This study offer a significant first approach to the reproductive phenology of mixed forests,assessing flowering,seeding and loss factors on reproductive success in three forest types(pure deciduous Nothofagus pumilio(Np),evergreen Nothofagus betuloides(Nb)and mixed(M)forests),comparing also between two geographical locations(coast and mountain),during one growing season.Results:Flowering falling started early in Np.Seed fall occurred first and more concentrated in Np,while in Nb,it was progressive during autumn.Phenology in M combined both patterns,but with better reproductive performance of both species.Seed production was greater in Nb(42,900,000 ha^(−1))than in Np(710,000 ha^(−1)),while M presented intermediate values(31,900,000 ha^(−1)).Abortion was greatest in Np(19% of female flowers and 10% of immature fruits),while fruit predation was low(7-9%)in all forest types.Empty seed was the main loss factor,but with low net values for each species in M.Regarding geographical location,sea proximity generated a quick starting of the growing season in coast compared to mountain sites.However,we detected forest types×location interactions in flowering and seeding patterns(e.g.in male flower production and in empty and viable seeds),with differences in species response according to location.Conclusions:Both deciduous and evergreen species have reproductive advantages in mixed compared to pure forests.However,mixed were more similar to pure evergreen forests in their reproductive traits and the incidence of the limiting factors.The study of only one growing season does not allow us to conclude whether mixed forests are stable communities,but we contribute to understand the roles of reproductive phenology in mixed forest dynamics.展开更多
Aims Forest canopy openings modify the natural environment,producing changes in light quality and intensity,precipitation and temperature.In turn,these changes promote the acclimation of understory species.However,lit...Aims Forest canopy openings modify the natural environment,producing changes in light quality and intensity,precipitation and temperature.In turn,these changes promote the acclimation of understory species.However,little work has been done on underground responses to those environmental changes.The objective of this work was to determine how Osmorhiza depauperata,Phleum alpinum and Poa pratensis change its root length density and root colonization by mycorrhiza as a function of light availability in a Nothofagus pumilio(i.e.lenga)forest harvested following the variable retention prescription.Methods We selected three microenvironments in an old growth forest harvested by the variable retention prescription:aggregated retention,dispersed retention with influence of aggregated retention and dispersed retention.A non-harvested primary forest(PF),similar to the harvested one,was used as a control.Every 2 months,from October 2008 to April 2009,we took soil cores from randomly selected plants.From these soil cores,root length density and colonization percentage(CP)by arbuscular mycorrhizae were estimated.Important Findings Light availability changed significantly among the microenvironments.In general,root length density was significantly greater in P.pratensis than in P.alpinum and both species greater than in O.depauperata.Light availability increased root length density in all species,although the magnitude of these increases difference among species.Root length density was 187%greater in P.pratensis,101%in P.alpinum and 94%in O.depauperata in the disperse retention system than in the PF.Mycorrhiza CP was higher in O.depauperata than in P.alpinum and P.pratensis.Also,it was lower in the PF than in the harvested microenvironments.CPs were very low.展开更多
基金Project APN-1236 supported this research during 2013-2014
文摘Background： Understory plants represents the largest component of biodiversity in most forest ecosystems and plays a key role in forest functioning.Despite their importance, the influence of overstory-layer composition on understory plant diversity is relatively poorly understood within deciduous-evergreen broadleaved mixed forests.The aim of this work was to evaluate how tree overstory-layer composition influences on understory-layer diversity in three forest types（monospecific deciduous Nothofagus pumilio（Np）, monospecific evergreen Nothofagus betuloides（Nb）, and mixed N.pumilio-N.betuloides（M） forests）, comparing also between two geographical locations（coast and mountain） to estimate differences at landscape level.Results： We recorded 46 plant species： 4 ferns, 12 monocots, and 30 dicots.Canopy-layer composition influences the herb-layer structure and diversity in two different ways： while mixed forests have greater similarity to evergreen forests in the understory structural features, deciduous and mixed were similar in terms of the specific composition of plant assemblage.Deciduous pure stands were the most diverse, meanwhile evergreen stands were least diverse.Lack of exclusive species of mixed forest could represent a transition where evergreen and deciduous communities meet and integrate.Moreover, landscape has a major influence on the structure, diversity and richness of understory vegetation of pure and mixed forests likely associated to the magnitude and frequency of natural disturbances, where mountain forest not only had highest herb-layer diversity but also more exclusive species.Conclusions： Our study suggests that mixed Nothofagus forest supports coexistence of both pure deciduous and pure evergreen understory plant species and different assemblages in coastal and mountain sites.Maintaining the mixture of canopy patch types within mixed stands will be important for conserving the natural patterns of understory plant composition in southern beech mixed forests.
文摘Evolutionary genetics of invasive species has been unexplored in Argentina. Invasive alien species (IAS) have a wide geographical distribution, characteristic life cycles and great ability to adapt, establish and spread in a new environment. Recent advances in novel molecular technologies, the use of higher resolution genetic markers, and the research development on genetic variation of invasive species consolidated the importance of genetic aspects in the invasion process. Undoubtedly, the growing concern for the disturbances generated by invasive species on biodiversity and functioning of ecosystems was also determinant for the inclusion of the Invasion Biology within the broad field of Evolutionary Biology including relevant examples that address the evolutionary genetic aspects of biological invasions. Recent studies suggest that the invasion success of many species depends on their ability to respond to natural selection. Although the number of invasive species registered in Argentina far exceeds 600, little research has been done on invasive mammal species and only five of them were hitherto genetically analyzed. Presuming that invasion genetics is incorporated into the agenda of control and management organizations, it would allow integrating the ecological, genetic, and evolutionary biology aspects for knowledge of invasive species widely distributed in Argentina. The objective of this article is to highlight the importance of evaluating the genetic structure of invasive species for their management and to inform about the invasive species of mammals that were introduced in Argentina and have been or are being analyzed genetically.
基金The research leading to these results further received funding grants ANPCYT PICT 2011-130 Raíces of the Agencia Nacional de Promociones Científicas of Argentina to IRS and MPH,and from the European Union’s Horizon 2020 research and innovation program under grant agreement No.730984,ASSEMBLEPLUS2019359 Project awarded to FDIt is further a contribution to CoastCarb(Funding ID 872609,H2020,MSCA-RISE-2019,Research and Innovation Staff Exchange).
文摘Under the present changing climate conditions and the observed temperature increase,it is of high importance to understand its effects on aquatic microbial life,and organisms’adaptations at the biochemical level.To adjust to temperature or salinity stress and avoid cell damage,organisms alter their degree of fatty acids(FAs)saturation.Thus,temperature is expected to have strong effects on both the quantity and quality of FAs in aquatic microorganisms.Here we review some recent findings about FAs sensitivity to climate change in contrasting environments.Overall,heat waves may induce changes in the relative abundance of polyunsaturated FAs(PUFA).However,the impact of the exposure to warming waters is different in temperate and polar environments.In cold marine waters,high concentration of omega-3(ω3)FAs such as eicosapentaenoic acid(EPA)is promoted due to the activation of the desaturase enzyme.In this way,cells have enough energy to produce or activate antioxidant protection mechanisms and avoid oxidative stress due to heat waves.Contrastingly,under high irradiance and heat wave conditions in temperate environments,photosystems’protection is achieved by decreasing EPA concentration due to desaturase sensitivity.Essential FAs are transferred in aquatic food webs.Therefore,any alteration in the production of essential FAs by phytoplankton(the main source ofω3)due to climate warming can be transferred to higher trophic levels,with cascading effects for the entire aquatic ecosystem.
基金carried out under Project UBACyT 20020130100146/14X236PIP 00416/11PICT 2013-1950
文摘The Quaternary infilling of a circular structure located in Bajada del Diablo,Chubut Province,Argentina has been proposed as a crater strewn field in previous studies.Here we report the finding of about 65 microspherules collected in a trench excavated in the center of the structure.The majority of handpicked specimens are single,but some of them exhibit compound forms.The single specimens are spherical with a mean size of 137 nm,whereas the more complex samples show peduncles and drop shapes.Dendritic crystal growth is recognized in the internal structure of some broken microspherules.Preliminary chemical composition from the surface and center of microspherules was determined by energy dispersive spectrometry employing EDS.Quantitative EMPA and XRD analysis indicate that the microspherules are mainly composed of Fe and O with magnetite,Fe0with subordinate wiistite.Following consideration of possible anthropogenic and volcanic origins,these spherulites are ascribed to an extraterrestrial input.An accumulation rate of 47 microspherules per m2/yr is estimated for the studied sediments.This value is two orders of magnitude higher than the reference flux for cosmic dust estimated for the last 1 Ma in the Transantarctic Mountains.The microspherules might have been generated as a byproduct of asteroid entry in the atmosphere.
基金funding from Agencia Nacional de Promoción Científica y Tecnológica(ANPCy T PICT 20151152)University of Tierra del Fuego(PIDUNTd F)and PUE 2016 to CADIC(CONICET)Agencia Nacional de Promoción Científica y Tecnológica,PICT 20151152,Patricia Rodriguez
文摘Background Ushuaia City has experienced much population growth and still lacks secondary treatment for its wastewater.As a result,most of the discharge is directed into the lotic ecosystems that cross the urban environment.This paper assesses the relationship between riparian areas and water quality along an urbanization gradient in the city's main watersheds:Pipo River,Buena Esperanza Stream and Arroyo Grande River.Results The Riparian Forest Quality Index adapted for Patagonia showed a positive correlation with the Fuegian Water Quality Index(r=0.83,p<0.05).Differences in the riparian index along the urban gradient were detected in all the studied watersheds.In general,non-urbanized sites in the upper zones showed very good or good quality while urbanized sites showed worse riparian conditions.Furthermore,in relation to the Fuegian Water Quality Index,this work showed spatial and temporal variations.The Pipo River watershed showed no statistically significant differences among sampling sites,although water quality decreased over time at the urbanized site near the outlet of the river(in March 2018 the Fuegian Water Quality Index was 88 and in March 2022 it was 38).In the Buena Esperanza Stream,significant differences were detected among sampling sites;water quality at the non-urbanized zones in the upper section and upper-middle section was higher than at the urbanized sites.In the Arroyo Grande River,despite the lower ranges of the Fuegian Water Quality Index observed at the urban site near the outlet,no significant differences were identified between study sites.Conclusion The relationship of both indices supports the relevance of the environmental surroundings of the watercourses and how their ecological integrity affects water quality in urban lotic ecosystems.The watersheds studied here are strongly linked to the complex dynamics of a growing city which was reflected by the Fuegian Water Quality.Our findings provide a scientific foundation for sustainable environmental management.We recommend integrated water resources management that not only ceases the direct discharge of wastewater into watercourses but also implements measures to protect and restore the riparian environment as a fundamental measure for the conservation of urban lotic ecosystems.
文摘Introduction:Variation in reproductive phenology among species is an important mechanism for maintaining species coexistence.In mixed forests,the impact of limiting(biotic and abiotic)factors on tree reproductive success regulates the maintenance of species in balanced proportions or the conversion towards monospecific forests.This study offer a significant first approach to the reproductive phenology of mixed forests,assessing flowering,seeding and loss factors on reproductive success in three forest types(pure deciduous Nothofagus pumilio(Np),evergreen Nothofagus betuloides(Nb)and mixed(M)forests),comparing also between two geographical locations(coast and mountain),during one growing season.Results:Flowering falling started early in Np.Seed fall occurred first and more concentrated in Np,while in Nb,it was progressive during autumn.Phenology in M combined both patterns,but with better reproductive performance of both species.Seed production was greater in Nb(42,900,000 ha^(−1))than in Np(710,000 ha^(−1)),while M presented intermediate values(31,900,000 ha^(−1)).Abortion was greatest in Np(19% of female flowers and 10% of immature fruits),while fruit predation was low(7-9%)in all forest types.Empty seed was the main loss factor,but with low net values for each species in M.Regarding geographical location,sea proximity generated a quick starting of the growing season in coast compared to mountain sites.However,we detected forest types×location interactions in flowering and seeding patterns(e.g.in male flower production and in empty and viable seeds),with differences in species response according to location.Conclusions:Both deciduous and evergreen species have reproductive advantages in mixed compared to pure forests.However,mixed were more similar to pure evergreen forests in their reproductive traits and the incidence of the limiting factors.The study of only one growing season does not allow us to conclude whether mixed forests are stable communities,but we contribute to understand the roles of reproductive phenology in mixed forest dynamics.
基金Agencia Nacional de Promoción Científica y Tecnológica(PAV2004-22428).L.J.Selzer was recipient of a doctoral scholarship by CONICET.
文摘Aims Forest canopy openings modify the natural environment,producing changes in light quality and intensity,precipitation and temperature.In turn,these changes promote the acclimation of understory species.However,little work has been done on underground responses to those environmental changes.The objective of this work was to determine how Osmorhiza depauperata,Phleum alpinum and Poa pratensis change its root length density and root colonization by mycorrhiza as a function of light availability in a Nothofagus pumilio(i.e.lenga)forest harvested following the variable retention prescription.Methods We selected three microenvironments in an old growth forest harvested by the variable retention prescription:aggregated retention,dispersed retention with influence of aggregated retention and dispersed retention.A non-harvested primary forest(PF),similar to the harvested one,was used as a control.Every 2 months,from October 2008 to April 2009,we took soil cores from randomly selected plants.From these soil cores,root length density and colonization percentage(CP)by arbuscular mycorrhizae were estimated.Important Findings Light availability changed significantly among the microenvironments.In general,root length density was significantly greater in P.pratensis than in P.alpinum and both species greater than in O.depauperata.Light availability increased root length density in all species,although the magnitude of these increases difference among species.Root length density was 187%greater in P.pratensis,101%in P.alpinum and 94%in O.depauperata in the disperse retention system than in the PF.Mycorrhiza CP was higher in O.depauperata than in P.alpinum and P.pratensis.Also,it was lower in the PF than in the harvested microenvironments.CPs were very low.
