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Fire is one of the main factors shaping vegetation characteristics around the world, with deep and complex effects on higher levels of the food web and ecosystem functioning. Specialist insects tend to be more vulnerable to fire than generalists due to their higher dependency on host plants; however, fire effects on specialist insects are still not clearly known.Our aim was to understand how fire‐induced changes in plant richness and floristic composition modulate community features of galling insects under different fire scenarios. Specifically, we address the following questions: Are changes in galling insect richness and herbivory explained by the variation in plant richness and floristic composition under different fire scenarios? Are species composition of vegetation and galling insect communities coupled under different fire scenarios?Species richness of plant and galling insect communities was higher in burned than in unburned plots, but the highest species richness was observed under different fire scenarios in both communities. Galling insect richness was better predicted by floristic composition than plant richness. Herbivory was similar under different fire scenarios and weakly related to plant richness and composition. Species composition of vegetation and galling insect communities was strongly coupled across different fire scenarios.The characteristics of galling insect communities were strongly affected by fire through vegetation changes, and were better explained by floristic composition than by plant richness. Our results highlight the importance of selecting areas under different fire scenarios to maximise biodiversity conservation. [ABSTRACT FROM AUTHOR]

Background and aims: A detailed and updated vegetation map is necessary to land use planning. Given the need for a land-use plan for the Córdoba mountains, we decided to: make a vegetation map of these mountains; describe the vegetation of the mapped classes; interpret their distribution along the elevation gradient, and discuss the implications for land use planning. M&M: We elaborated a preliminary map from satellite images and field information, where we discriminated 14 vegetation units. Then, after a field control, we performed the final map, grouping the vegetation units into seven classes. Results: In the final map we identified: native forests, exotic forests, native scrublands, grasslands, lawns, grasslands with rock and/or bare soil and rocky areas. These classes were discriminated with an overall 82.6% precision. In addition, we separated water bodies, flood areas, crops and urban areas. The scrublands were the most widespread class, covering 37% of the landscape, followed by crops, covering 23% of the territory. Native forests only occupied 5.5% of the area. Scrublands and forests decreased along the elevation gradient, while grasslands and rocky areas increased. Conclusions: We suggest that land use planning should promote the restoration of native forests to occupy 20-40% of the landscape, the control of the advance of urban areas and crops, and the management of invasive alien species to limit their expansion. [ABSTRACT FROM AUTHOR]

Background and aims: Mountains hold a large portion of global biodiversity and provide important benefits to humans. With the aim of providing a key tool for the sustainable management of Córdoba mountain ecosystems, we present an exhaustive list of vascular plants and their altitudinal ranges. M&M: We compiled 669 complete floristic surveys and 1178 partial surveys performed from 2005 to 2020. Results: We record 1069 plant species: 147 non-native, 143 endemic to Argentina, 25 endemic to Córdoba and San Luis and 19 endemic to Córdoba. Most species had their median elevation below 1000 masl. Species turnover up to 1250 masl is slow, but from this elevation onwards it begins to accelerate, and continues in a similar way up to the highest end of the gradient. Out of all recorded species, 46 % are recognized as medicinal, of which, 79 are non-natives, 36 are endemic to Argentina, two are endemic to Córdoba and San Luis and two are exclusive of Córdoba. Conclusions: The list includes 60% of the species cited for Córdoba province and 65.5% of the medicinal flora recorded for this province. The upper end of the mountains, which represents less than 10% of the area, concentrates the highest proportion and diversity of endemic species in central Argentina. Our results show the importance of these mountains for the conservation and sustainable management of Córdoba biodiversity, and represent a baseline for future studies. [ABSTRACT FROM AUTHOR]

Leaf functional traits in a plant community are the result of the effect of environmental conditions and have a direct impact on ecosystem properties and functioning. We analyzed the variations of five leaf functional traits in plant communities from central Argentina under different climatic conditions and anthropogenic use determining changes in physiognomy. Study sites were located in Córdoba province (Argentina) within four phytogeographic units categorized according to their climatic condition based on an aridity index; they were named as 'climatic units' 1, 2, 3 and 4, following a gradient from lower to higher temperature and aridity. In each climatic unit we selected six sites located in two physiognomies corresponding to different degrees of anthropogenic use: 3 sites in woodlands (less use), and 3 sites in grasslands/shrublands (more intense use). We measured five leaf traits (specific leaf area [SLA], leaf dry matter content [LDMC], leaf toughness, leaf thickness and decomposability), and we calculated the community weighted mean for each trait for each site. The variations in functional leaf traits were mainly determine by climatic conditions. The physiognomic change, because of anthropogenic use, also affected these variations, but this effect was conditioned by climate. Under colder and wetter climatic conditions, the removal of tree species result in communities dominate mainly by grasses with conservative foliar trait values (e.g., lower SLA, higher leaf toughness and lower decomposability). However, in warmer and drier climatic conditions, the removal of tree species did not imply a change in the functional strategy of the community as it resulted in an increase dominance of grasses and dicotyledonous shrub species with relatively lower foliar toughness and high decomposability. Our results show the interactive effect of climate and anthropogenic use on the variations in leaf functional traits and the complexity to predict the effects of such variations on ecosystem processes. [ABSTRACT FROM AUTHOR]

Galls are structures produced by plants in response to the activity of several types of organisms. Gall-inducing species have a close relationship with their host plant, as their habitat is largely restricted to the gall and the plant organ in which it develops. All plant organs are susceptible to gall induction by insects, the leaves being the most vulnerable. Knowledge about interactions between gall-inducing insects and plants is fragmented and incomplete in Argentina. In this study, we completed an inventory of galls induced by insects on plants in Córdoba (central Argentina) using information from field surveys and a review of the literature. We also focused on the frequency of plant-insect taxonomic associations and plant organs most commonly attacked by gall-inducing insects. Field surveys were performed systematically in 26 sites of Chaco Serrano, which were visited five times in two consecutive years, and in 17 sites of the province, which were sampled one or two times each. A comprehensive literature search of electronic and conventional databases was also conducted to complete the inventory. A total of 99 gall morphospecies on 58 plant species (21 families and 44 genera) were recorded through both field surveys and a literature review, enlarging the list of species available for the region by almost 50 %. Asteraceae and Fabaceae were the plant families most attacked by galling insects, in partial concordance with the most species-rich plant families in the region. Diptera, particularly the family Cecidomyiidae, was the most species-rich group in the community of galling insects, which is in agreement with different studies across the globe. Baccharis was the genus displaying the highest number of gall morphotypes, followed by Acacia, Condalia, Geoffroea, Prosopis and Schinus. Almost 60 % of the morphotypes were stem galls, a pattern uncommon in the literature. Fusiform and globoid-shaped galls were predominant. Our study highlights the scarce knowledge there is about the interactions between plants and gall-inducing insects in Argentina, particularly those involving species of Cecidomyiidae, with more than 30 undescribed species. Possible mechanisms involved in the predominance of stem galls in central Argentina are discussed. [ABSTRACT FROM AUTHOR]

Questions Most vegetation descriptions tacitly assume that floristic composition and physiognomy are tightly linked. However, the two vegetation properties may not respond in a similar way to environmental and disturbance gradients, leading to uninformed management planning and difficulties when attempting to restore degraded ecosystems. In this context, we addressed two main questions: (1) how close are relations between floristic and physiognomic types as defined by numerical vegetation classification in mountain ecosystems; and (2) how are floristic and physiognomic types distributed along the elevation gradient? Location Central mountains of Argentina, between 500 and 1700 m a.s.l. Methods We selected 437 sites where we performed complete floristic and physiognomic relevés. We classified eight physiognomic and eight floristic types. We tested the relationship between the two classifications through a chi square analysis. We tested the association between elevation and each physiognomic and floristic type with random permutations. Results In general, floristic types were significantly and positively associated with more than one physiognomic type and vice versa. Physiognomic and floristic types responded differently to the elevation gradient. Floristic types were restricted to different sections of the gradient, although having large overlap among them. In contrast, seven out of the eight physiognomic types did not show elevation restriction, being distributed along the complete elevation gradient. The open low woodland with shrubs was the only restricted physiognomy, significantly absent from the upper part of the gradient. Conclusions We highlight the importance of considering the two vegetation properties independently when characterizing vegetation patterns in heterogeneous systems, since they show decoupled responses to environmental gradients. We note that the assumption of a direct link between floristic composition and physiognomy may induce bias into the understanding of vegetation patterns and processes. Hence, we encourage managers and restoration practitioners to consider the complete range of possible physiognomic types under each floristic type. [ABSTRACT FROM AUTHOR]

The existence of a coordination between leaf and stem economic spectra in woody species has been postulated repeatedly in the literature, with contrasting results. Here, we postulated that this coordination is conditioned by climate factors, being stronger in stressful environments. To test this hypothesis we explored the coordination between leaf and stem economic spectra in a seasonally dry forest in central Argentina and at the global scale, we analysed if the outcome of their coordination varies along a climatic gradient. At the local scale, we characterized leaf and stem economic spectra in 37 woody species by measuring six leaf and stem functional traits related to resource acquisition and use, and two functional traits used as proxies of water transport and use capacities. At the global scale, a meta-regression was performed to analyse if the outcome of the coordination among leaf and stem traits varies along gradients of the mean precipitation of the driest quarter and of the minimum temperature of the coldest month. At the local scale, we observed a high integration among the measured leaf and stem traits, and this coordination seemed to be linked to hydraulic properties. At the global scale, we found not only that the overall weighted mean effect size of the correlation between specific leaf area and wood density was significant and negative but also that the coordination between leaf and stem traits seemed to be shaped by climate and tends to become stronger under harsh climate conditions. Furthermore, although our results seem to suggest that their coordination is context-dependent, alternative strategies could be observed under stressful conditions. [ABSTRACT FROM AUTHOR]

Geographical range and spatial structure of genetic lineages in Sophora linearifolia (Fabaceae), an endemic shrub of Central Argentina. A large number of endemic species occur in the Sierras of Córdoba and San Luis. A significant group of them shows a disjunct geographic distribution between these two mountain regions. Until the present study, there were none genetic studies that allow us to infer historical processes underlying this geographical pattern. For this purpose, we characterize the distribution area and phylogeographic patterns of Sophora linearifolia, across its geographic range which includes Sierras Chicas (SC) and Cumbres de Gaspar (CG) in Córdoba and in the southwestern area of Sierras of San Luis (SL). We compared the current with the predicted species area of distribution using ecological niche modelling analysis. We also analyzed genetic variability and spatial structure of the DNA chloroplast marker trnH-psbA, and reconstructed the genealogical relationships among the retrieved haplotypes. Current and the predicted distribution agreed in showing a climatic/topographic disjunction between Sierras of Cordoba and San Luis hills, although the current distribution presents a disjunction between SC and CG in Córdoba, not shown in the potential distribution map. We obtained eight haplotypes with restricted distribution and low levels of genetic differentiation that were grouped into four phylogroups: SC, CG and two in SL. Our results indicate that S. linearifolia presents low dispersal ability and it would have recently diversified, suggesting a neoendemic taxon. [ABSTRACT FROM AUTHOR]

Two new records of Polystichum (Dryopteridaceae) for the Argentine Flora. In this paper, two new records for the Argentina fern-flora are reported: P. subintegerrimum (Hook. & Arn.) R. Rodr. found in the Patagonian Forests and P. platylepis Fée collected in Misiones; both have been considered endemic for Chile and Brazil, respectively. The species are described and illustrated. [ABSTRACT FROM AUTHOR]

Holocene paleoclimatic variation in The Cordoba Mountains (Argentina). A contribution to climate reconstruction though silicophytolith analysis from archaeological site El Alto 3. The analysis of silicophytoliths is an increasingly used tool for paleoclimatic reconstructions. However, in Córdoba climatic reconstruction has been performed with other techniques. In this work we aimed to calculate international climatic indices through silicophytoliths, validate these indices with the current vegetation and climate distribution in the Mountains, and present the irst paleoclimatic reconstruction through silicophytoliths for the oldest archaeological site in Cordoba. The international indices were consistent with the patterns of the current vegetation and climate distribution; though the coolness index was more robust and sensitive than the aridity index. Along the analyzed proile the silicophytoliths indicated a cold and humid/wet climate, which is characteristic of a mountain site, but they showed important variation in the coolness and aridity index. The climatic reconstruction was consistent with the previous studies, since it showed a peak of aridity at the beginning of the Holocene, followed by a wetter and warmer climate than the current climate, a subsequent peak of higher aridity and warm was coincident with the presence of the Arecaceae family, and inally it showed a temperature reduction and precipitation increase until the present. [ABSTRACT FROM AUTHOR]

Post-fire forest restoration is increasingly demanded with the aim of reducing post-fire soil erosion and accelerating forest recovery. Under the hypothesis that Acacia caven, a dominant species in disturbed woodlands, is more tolerant to environmental post-fire conditions than Lithraea molleoides, a dominant species in preserved forests, we assessed the performance of seedlings outplanted to burnt and unburnt areas in three sites of the Córdoba mountains. We registered the survival and growth two years after planting. Survival varied between 24 and 92% according to treatment, without differences between species and between burnt and unburnt areas but with significant differences among sites (P<0.001). The growth was variable; in some treatments, seedlings had a mean height lower than plantation height, while in other treatments, seedlings grew up to double its initial height, without differences between burnt and unburnt areas. L. molleoides growth was higher than A. caven growth (11.4±1.4 cm and -2.3±2.0 cm, respectively) and varied among planting sites (P<0.001). Contrary to expectations, both species had similar performances in burnt and unburnt areas, while the main differences occurred among sites. To attain restoration goals we recommend planting the dominant species in preserved forest as the dominant species in disturbed woodlands is widely distributed in the region. Our results highlight the importance of studying in each site which species are most adequate to optimize restoration efforts in highly heterogeneous forest as Chaco Serrano. [ABSTRACT FROM AUTHOR]

Invasive alien trees and shrubs in Córdoba Province (Argentina): a contribution to the systematization of global bases. We present the first database of invasive alien trees and shrubs of Córdoba Province and analyze it in the context of current national and global databases. We identified 34 invasive woody alien species. Most aliens are from Europe, Asia and Middle East origin, introduced for horticulture reasons. Grasslands are the most invaded ecosystem (39%), followed by woodlands and shrublands (32%). Most of the species (59%) are dispersed by animals (birds) and wind (35%). Except for two species, most of the species has also been recorded as invaders in other areas of the world. However, only half of them are currently registered as invaders in South America. This might reflect the notably lower research on biological invasions within the continent and the subsequent bias and underestimation of its invasibility. Two species (Cupressus macrocarpa and Zanthoxylum armatum) should be incorporated as new species in the global database. We also refer to some missing information in two major national databases, hoping to contribute with their updating. Finally, we mention six species native to Argentina to be considered as native invaders of Cordoba Province ecosystems. Overall, we expect to provide useful information for the development of basic and applied studies of biological invasions. [ABSTRACT FROM AUTHOR]

In this study we assessed the water transport strategies and the abundance of alien and native tree species at a regional scale in Córdoba Mountains, Central Argentina. The aims of this study were: (i) to analyse whether alien and native tree species show divergent water transport strategies; and (ii) to explore whether species abundances of alien and natives are associated with specific trait attributes. Eight alien species and 12 native species were recorded in 50 complete vascular plant vegetation relevés. Water transport strategies were assessed through the following functional traits: minimum leaf water potential, potential water content of wood, effective leaf area, leaf area per sapwood area and wood density. Also, resource use strategies were assessed throughout the measurement of specific leaf area. We found that alien species had a higher efficiency in water transport (i.e. higher minimum leaf water potential and lower wood density values) and faster resource acquisition and use (higher specific leaf area values) than native species. We did not find evidence suggesting that the relative abundance of species was associated to water transport strategies and faster resource acquisition and use. Alien species seem to differ from natives in specific functional attributes that are absent in the resident community and might allow aliens to use more resources and at a higher rate than native species. Finally, our results show the potential of a trait-based predictive framework for alien species, and the possible effects on ecosystem functions. [ABSTRACT FROM AUTHOR]

In fire-prone landscapes, differences in post-fire regeneration by resprouting between species or sites could be far more important in explaining vegetation physiognomy and composition than seed regeneration. This is the first study exploring the relative contribution of tree resprouts and seeds to post-fire crown volume in the Chaco Serrano forest of South America. Additionally, we compare the resprouting response among species and quantify post-fire changes in tree composition among sites. We established 290 permanent plots distributed in three sites affected by wildfires in 2005. For all tree species in all plots we recorded survival of every individual 1 year after the fire; at the plot level, we recorded the above-ground tree volume before and 3 years after the fire. Resprouting from the base was the main resprouting type. Survival varied between species from 73% to 100% for native species and from 7% to 100% for non-natives. Before the fire, crown volume was similar in the three sites, and was completely lost after the fire in 92% of the plots. Three years after the fire, between 8% and 58% of crown volume was recovered. The ratio of crown recovery because of resprouts and seedlings was 1562:1. Tree composition exhibited few changes because of the high post-fire survival of most native species. We conclude that in the semiarid Chaco Serrano ecosystem tree species regenerate mainly by resprouting. This regeneration mode should be taken into account to better understand post-fire successional pathways of these forests, their management and the restoration of burnt forest areas. [ABSTRACT FROM AUTHOR]

Aim: Millennial-scale biogeographic changes are well understood in many parts of the world, but little is known about long-term vegetation dynamics in subtropical regions. Here we investigate shifts in C/C plant abundance occurred in central Argentina during the past few millennia Methods: We determined present day soil organic matter δC signatures of grasslands, shrublands and woodlands, containing different mixtures of C and C plants. We measured past changes in the relative cover of C/C plants by comparing δC values in soil profiles with present day δC signatures. We analyzed C activity in soil depths that showed major changes in vegetation. Results: Present day relative cover of C/C plants determines whole ecosystem δC signatures integrated as litter and superficial soil organic matter (R = 0.78; p < 0.01). Deeper soils show a consistent shift in δC, indicating a continuous replacement of C by C plants since 3,870 (±210) YBP. During this period, the relative abundance of C plants increased 32% (average across sites) with significant changes being observed in all studied ecosystems. Conclusions: Our results show that C species were more abundant in the past, but C species became dominant during the late Holocene. We identified increases in the relative C/C cover in grasslands, shrublands and woodlands, suggesting a physiological basis for changes in vegetation. The replacement of C by C plants coincided with changes in climate towards colder and wetter conditions and could represent a climatically driven shift in the C species optimum range. [ABSTRACT FROM AUTHOR]

In systems with seasonal rainfall, the dry season water yield (streamflow relative to the catchment area) depends on the antecedent rainfall as well as on infiltration and evapotranspiration, processes which, in turn, are affected by the landscape characteristics. Our objective was to evaluate the effect of different landscape variables on water yield and the recession rate (rate of decrease in streamflow) during the dry season in high-mountain catchments in central Argentina. We selected 33 catchments 9-61 ha and, during the last part of the 2017 dry season, we measured streamflow in the catchment output points once a week, for seven consecutive weeks. For each catchment, we calculated the average water yield (mm/month) and a recession index (dimensionless) as the normalized difference between the water yield of the latest and the first dates. The landscapes extensively occupied by a tussock grassland-rock mosaic, with intermediate steepness and roughness, had the highest water yields (>5 mm/month). Conversely, water yield was lower either in smooth and vegetated landscapes as in extremely rugged, steep and rocky landscapes. On the other hand, recession rate was slower in the most rugged landscapes and abrupt in the smooth landscapes. Possibly, in smooth and vegetated landscapes, high amounts of water are lost through evapotranspiration, while in the most rugged landscapes, large amounts of water are lost by runoff after rainfall. Intermediate landscapes covered by a mosaic of rock and vegetation would be those that optimize water storage, minimizing losses through evapotranspiration. Therefore, to sustain current water yields, these types of landscape must be conserved, preventing soil erosion, leading to an increase in rocky areas. [ABSTRACT FROM AUTHOR]

Background and aims: Biodiversity information of protected areas is essential to develop management and conservation strategies. Here we 1) evaluate the number of records of plant and vertebrate species of National Parks (NP) from Argentina based on the species richness of the province where each NP is located, 2) analyze possible explanatory variables of the number of records in each NP, and 3) describe the vegetation registered in three iconic NPs of the country. M&M: The records of vascular plants and vertebrates, the characteristics of each NP and the species richness of the province where each NP is located were obtained from open access databases. For Calilegua, Iguazú and Nahuel Huapi NPs we describe the number of plants according to family, origin, endemism, life form, IUCN categorization and invasiveness of non-native species. Results: All NPs showed great variability in their records. There were few records of non-native species. Older NPs had more non-native plants records. The list of plants of Nahuel Huapi NP showed more records than Calilegua and Iguazú. The number of plants categorized by IUCN was very low. Almost all recorded non-native plants were invasive elsewhere in the world. Conclusions: We emphasize the importance of increasing the survey of species in all NP, particularly vascular plants and in recently created NPs. Special attention must be given to non-native species in order to avoid socio-ecological problems associated with biological invasions. [ABSTRACT FROM AUTHOR]

Background: 'Megafire' is an emerging concept commonly used to describe fires that are extreme in terms of size, behaviour, and/or impacts, but the term's meaning remains ambiguous. Approach: We sought to resolve ambiguity surrounding the meaning of 'megafire' by conducting a structured review of the use and definition of the term in several languages in the peer‐reviewed scientific literature. We collated definitions and descriptions of megafire and identified criteria frequently invoked to define megafire. We recorded the size and location of megafires and mapped them to reveal global variation in the size of fires described as megafires. Results: We identified 109 studies that define the term 'megafire' or identify a megafire, with the term first appearing in the peer‐reviewed literature in 2005. Seventy‐one (~65%) of these studies attempted to describe or define the term. There was considerable variability in the criteria used to define megafire, although definitions of megafire based on fire size were most common. Megafire size thresholds varied geographically from > 100–100,000 ha, with fires > 10,000 ha the most common size threshold (41%, 18/44 studies). Definitions of megafire were most common from studies led by authors from North America (52%, 37/71). We recorded 137 instances from 84 studies where fires were reported as megafires, the vast majority (94%, 129/137) of which exceed 10,000 ha in size. Megafires occurred in a range of biomes, but were most frequently described in forested biomes (112/137, 82%), and usually described single ignition fires (59% 81/137). Conclusion: As Earth's climate and ecosystems change, it is important that scientists can communicate trends in the occurrence of larger and more extreme fires with clarity. To overcome ambiguity, we suggest a definition of megafire as fires > 10,000 ha arising from single or multiple related ignition events. We introduce two additional terms – gigafire (> 100,000 ha) and terafire (> 1,000,000 ha) – for fires of an even larger scale than megafires. [ABSTRACT FROM AUTHOR]

The transformation of forests to treeless landscapes as a result of disturbances (deforestation transitions) is an ongoing process in many regions of the world. Here we first revise the historical context of these transformations and then, we focus on its consequences for litter decomposition. We also present a case study, based on four ecosystems of central Argentina (Sub-Andean, Mountain Chaco, Espinal and Arid Chaco), evaluating how deforestation transitions can modify ecosystem decomposition by altering its main controls. Although there is evidence of consequences of deforestation transitions on the local environment for decomposition and on leaf litter quality it is not clear how those changes would impact the decomposition of natural mixed litter in the field. In our study case, we show that the deforestation transitions evaluated across four ecosystems resulted in no consistent changes in standard substrate decomposition but a consistent increase in the litter mixtures' decomposability and quality. Likely as a consequence of this pattern, the loss of trees resulted in a consistent increase in the in situ mixtures decomposition across the ecosystems studied. Beyond our particular findings, our analysis highlights how the accurate prediction of the consequences of deforestation transition on changes in carbon and nutrient cycling needs to understand the behaviour of its controls. Only through this understanding, we will be able to interpret the patterns of in situ mixtures decomposition and predict the consequences of deforestation transitions adequately on carbon (C) and nutrient cycling. Additionally, the recent literature, in coincidence with our results, gives evidence that the presence of non-leafy plant debris and local-scale variation in the local environment may play a stronger role than previously thought in C and nutrient cycling. [ABSTRACT FROM AUTHOR]

Abstract: The livestock industry is converting mountain ecosystems in central Argentina into rocky deserts. However, it helps to conserve plant biodiversity, presumably because the ecosystem has evolved under wild herbivores now locally extinct. We hypothesized that low or moderate livestock stocking rates, instead of the high stocking rates currently used for commercial production, might mimic pre-hispanic herbivore pressures. Thus, the mosaic of physiognomies necessary to maintain landscape diversity and soil integrity could be preserved. To test this hypothesis we tracked physiognomic changes in 200 plots (16m2 each) under different stocking rates, including livestock exclusion, for five years. Contrary to our expectations, we found that both low and moderate stocking rates failed to maintain landscape diversity. As observed for livestock exclusion, low to moderate stocking rates promote retraction and, finally, elimination of short grazing lawns and their replacement by tall tussock grasslands, or possibly by woody vegetation. In turn, heavy grazing pressure maintains the desired short lawn patches in the landscape, but also promotes a concomitant loss and eventual elimination of woodlands, together with an expansion of bare rock as a consequence of soil erosion. These results indicate that the present mosaic of physiognomic types is difficult to maintain and raise questions about the past stability of the ecosystem. We suggest that during the last 400 years of livestock production in the ecosystem, short lawns have been maintained by means of heavy stocking rates and anthropogenic fires ignited to eliminate tussocks. However, this relative stability of lawns has been attained concomitantly with a progressive loss of soils and woodland area. We also discuss some possible explanations for the maintenance of short lawns before the introduction of livestock, based on main climatic and floristic shifts during the late Holocene. [Copyright &y& Elsevier]

In mountain ecosystems, vegetation distribution along elevation has been traditionally interpreted in terms of the decreasing temperature from base to top, but wildfires may co-vary with the elevation gradient, also playing an important role. In the mountains of central Argentina (500-2800 m a. s. l.) wildfires are one of the main disturbances, which may have an important role in shaping vegetation dynamics along elevation. However, to date, no study described the fire pattern along the elevation gradient. We compared fire incidence among five elevation intervals using an 18-year spatially explicit fire database derived from remote sensing. For each interval, we discarded unburnable areas and calculated fire incidence per year as the percentage of burned area. Fire incidence showed a hump-shaped pattern along the elevation gradient. The highest fire incidence occurred at intermediate elevations, in the 1301-1700 m and 901-1300 m intervals, with averages of 3.2 and 2.7% of the area being burned annually, respectively. The lowest fire incidence occurred at the lowest interval (500-900 m), with 1.3% being burned annually on average. The greater fire incidence observed at intermediate elevations is consistent with a sharp increase in the cover of grasslands above 900 m a. s. l., with an associated reduction in forest occupation. Towards higher elevations, the lower fire incidence is consistent with the presence of topographic breaks, greater proportion of unburnable surfaces that work as firebreaks and moister conditions. The greater fire incidence observed at intermediate elevations may be limiting forest expansion in those areas. At higher elevations the low forest cover may be explained by a combination of fire and livestock pressure. Our study is the first to show how fire incidence varies along the complete elevation gradient, bringing an important tool to understand vegetation distribution and plan future conservation and restoration strategies. [ABSTRACT FROM AUTHOR]

Abstract: Question: What are the composition and spatial patterns of native woody plant communities in the southern Great Chaco and Espinal? Location: Córdoba Province, central Argentina, an area of ca. 161,000 km2. Methods: We collected 351 geo‐referenced relevés representative of the geographic, topographic and ecological variation of the Chaco and Espinal woody vegetation in central Argentina. The relevés were classified into vegetation types using the hierarchical ISOPAM method. Forest and shrubland types were described on the basis of diagnostic species occurrences and their distribution in relation to environmental factors. A map of the actual vegetation derived from remote‐sensed images (Landsat) and field data was used to describe the current distribution and abundance of the different vegetation types. Results: The classification of the 351 plots × 837 species matrix revealed two major clusters comprising seven woody vegetation types corresponding to Chaco lowland and mountain forests and shrublands, Espinal forests and edaphic vegetation. The most important gradients in woody vegetation types are related to elevation, temperature and rainfall variables. Conclusions: Subtropical seasonally dry woody plant communities from the southern extreme of the Great Chaco and Espinal forests were described for the first time based on complete floristic data. Our results show that lowland Chaco native forests, as well as replacement communities, are still present in its southern distribution range and are well distinguishable from other vegetation types such as the Espinal and mountain forests. Overall, extensive Espinal forests have almost disappeared while Chaco vegetation is highly fragmented and degraded. [ABSTRACT FROM AUTHOR]

On the occasion of preparing the Flora of Cordoba, new records for the Argentinean flora have been registered as a result of intensive field trips and the revision of the main herbaria collections of the country. In this paper, three new records for the native flora and 17 for the introduced flora (casual aliens and naturalized species) of Argentina are presented. Descriptions, illustrations and a lectotypification are done. Furthermore, the presence of 10 introduced species is formally documented for the first time. [ABSTRACT FROM AUTHOR]

Abstract: Exotic species can have a strong influence on ecosystem processes, especially when exotic invaders differ from natives in key morpho-functional features. We explored whether exotic species, especially those forming monospecific patches in Chaco montane woodlands, differ from natives in leaf attributes and decomposability. We then evaluated how exotic monospecific patches in that region alter litter decomposability, by weighting leaf trait values and decomposability by species abundance in the communities. In general, native and exotic species from Córdoba Chaco montane woodlands did not differ in leaf attributes (specific leaf area, leaf toughness, and leaf water content), or decomposability. Because of similar trait values and decomposability, we expected to find no differences in litter decomposability between plots dominated by exotic species and those of Native woodland. However, individual species decomposability weighted by species abundance in the communities showed that litter from exotic monospecific plots had slower decomposition than native ones. This pattern was confirmed by the higher decomposability and higher quality of the naturally mixed litter collected from native plots, compared to those collected from exotic plots. Despite the general similarities between most native and exotic species inhabiting Chaco montane woodlands, the overwhelming dominance of some exotic invaders in monospecific stands (and the consequent weight of their attributes on the litter each woodland produces) might be driving differences in decomposition patterns between woodland types. Our results indicate that when estimating the impact of exotic species on ecosystem processes, we should include their relative abundance in the community, as well as the relevance of the traits influencing those processes. Otherwise, we may draw erroneous conclusions. [Copyright &y& Elsevier]

Mountain forests and their soils provide ecological services such as maintenance of biodiversity, provision of clean water, carbon capture and forage for livestock rearing, which is one of the principal economic activities in mountain areas. However, surprisingly little is known about livestock impact in South American mountain forest soils. With the aim of understanding how livestock and topography influence patterns of forest cover, soil compaction, soil loss and soil chemical properties, we analysed these parameters in 100 Polylepis australis woodland plots situated in the humid subtropical mountains of Central Argentina. We used distance from the nearest ranch as an objective index of historical livestock impact and measured standard topographic variables. Our main results reveal that distance from ranch in all cases partly explains tree canopy cover, soil loss, soil compaction and soil chemical properties; suggesting a strong negative effect of livestock. Intermediate altitudes had more tree canopy cover, while landscape roughness – a measure of the variability in slope inclination and aspect – was negatively associated to soil impedance and acidity, and positively associated to soil organic matter content. Finally, flatter areas were more acid. We conclude that livestock has had a substantial influence on forest soil degradation in the Mountains of Central Argentina and possibly other similar South American mountains. Soil degradation should be incorporated into decision making when considering long-term forest sustainability, or when taking into account retaining livestock for biodiversity conservation reasons. Where soil loss and degradation are ongoing, we recommend drastic reductions in livestock density. [ABSTRACT FROM AUTHOR]

Climate affects litter decomposition directly through temperature and moisture, determining the ecosystem potential decomposition, and indirectly through its effect on plant community composition and litter quality, determining litter potential decomposition. It would be expected that both the direct and indirect effects of climate on decomposition act in the same direction along gradients of actual evapotranspiration (AET). However, studies from semiarid ecosystems challenge this idea, suggesting that the climatic conditions that favour decomposition activity, and the consequent ecosystem potential decomposition, do not necessarily lead to litter being easier to decompose. We explored the decomposition patterns of four arid to subhumid native ecosystems with different AET in central-western Argentina and we analysed if ecosystem potential decomposition (climatic direct effect), nutrient availability and leaf litter potential decomposition (climatic indirect effect) all increased with AET. In general, the direct effect of climate (AET) on decomposition (i.e. ecosystem potential decomposition), showed a similar pattern to nutrient availability in soils (higher for xerophytic and mountain woodlands and lower for the other ecosystems), but different from the pattern of leaf litter potential decomposition. However, the range of variation in the ecosystem potential decomposition was much higher than the range of variation in litter potential decomposition, indicating that the direct effect of climate on decomposition was far stronger than the indirect effect through litter quality. Our results provide additional experimental evidence supporting the direct control of climate over decomposition, and therefore nutrient cycling. For the ecosystems considered, those with the highest AET are the ecosystems with the highest potential decomposition. But what is more interesting is that our results suggest that the indirect control of climate over decomposition through vegetation characteristics and decomposability does not follow the same trend as the direct effect of climate. This finding has important implications in the prediction of the effects of climate change on semiarid ecosystems. [ABSTRACT FROM AUTHOR]

• Seasonally dry ecosystems experience low flow periods and recurrent fires. • Fires may influence low flows changing the water infiltration-evapotranspiration balance. • 12 burnt and 12 unburnt catchments were followed after a fire in central Argentina. • The minimum low flow was reduced by 48% the next dry season after the fire. • Reduced water infiltration and/or increased plant consumption are discussed as the causes. Wildfires are recurrent in seasonally-dry ecosystems; however, their effects on streamflows at the end of the dry season (low flows) are not well understood. The infiltration-evapotranspiration trade-off hypothesis postulates that when vegetation cover is lost or degraded, low flows in the following dry season are reduced due to impaired water infiltration and storage in soils during the wet season, which surpass gains due to diminished evapotranspiration. We tested this hypothesis in the context of vegetation loss produced by fire. For this purpose, we seized a wildfire in a subtropical highland of central Argentina and selected 12 burnt and 12 unburnt catchments of 15–60 ha. We measured low flows at the outlet point of each catchment in two opportunities: one year after the fire (post-fire dry season) and in a dry season not affected by previous fire (control dry season). Using the 12 unburnt catchments, we built linear regression models to estimate the expected low flows for the post-fire dry season under a no-fire scenario. The predictor variables were low flows in the control dry season. We applied the models to burnt catchments and compared the expected with the observed low flows. We also evaluated vegetation activity through satellite images. Burnt catchments showed significant low flow reductions of 31–48% compared with expectations under a no-fire scenario, supporting the infiltration-evapotranspiration trade-off hypothesis. Vegetation activity was lower in burnt than in unburnt catchments only for the first three months after the fire, while it was more active since then for one year. Together our results suggest that post-fire reduced low flows can be explained by a reduced infiltration, as well as by higher evapotranspiration due to increased vegetation activity. Given the extent of seasonally dry ecosystems worldwide, we highlight the importance of controlling wildfires to improve streamflow in the dry-season. [ABSTRACT FROM AUTHOR]