Patagonian Steppe Research Articles

Whole-genome sequencing of a Janthinobacterium sp. isolated from the Patagonian Desert.

Janthinobacterium is a genus of Gram-negative environmental bacteria that survive extreme conditions by forming biofilms and producing pigments. Janthinobacterium sp. LS2A, an extremophile isolated from soil in the Chilean Patagonia, contains seven known biosynthetic gene clusters, including the purple pigment violacein, which may aid in its survival in harsh environments.

Effect of conifer afforestation on the occurrence and food availability for Zaedyus pichiy (Xenarthra: Chlamyphoridae) in the north-western Patagonian steppe of Argentina

Abstract The grasslands and shrub areas of the Patagonian steppe are the most frequent habitat for the “Near Threatened” armadillo, known as pichi (Zaedyus pichiy). Dense exotic conifer plantations are replacing the steppe in Argentinean northern Patagonia. This study aimed to evaluate the effect of conifer afforestation on the occurrence and food availability in a Z. pichiy population in north-western Patagonia. Fifteen sites in the native steppe and 50 in exotic pine plantations were sampled. We recorded the number of signs of pichi’s presence and the diversity of invertebrates. Signs of Z. pichiy presence decreased in pine afforestation compared to the native steppe. Additionally, we found a decrease in the abundance, richness, diversity, and biomass of arthropods in pine plantations. Therefore, the presence of pine plantations in the steppe reduces the main food items of Z. pichiy and also eliminates the native steppe vegetation structure that provides preferred places to dig burrows. Pine monocultures do not provide a suitable habitat for Z. pichiy and may exacerbate the degradation of an already disturbed environment.

Differences in bacterial community composition between fish-stocked and fishless lakes from an arid Patagonian plateau

Differences in bacterial community composition between fish-stocked and fishless lakes from an arid Patagonian plateau

Photosynthetic response to water stress of the main grass species of southern patagonian steppe, Argentina

Comparative studies of basic physiological performance are needed to give insight of how grass species survive and grow under current and more severe drought predicted in the framework of climate change in arid steppe grasslands. In this study, photosynthetic performance and stomatal conductance (gs) were measured in leaves of six main grass species of southern Patagonian steppe, after exposing plants to different conditions of water availability. There was a negative linear relationship between photosynthesis at light saturation (Pmax) and plant water stress, expressed as pre-dawn leaf water potential (ψpd), mainly explained by the reduction in gs. A negative linear relationship was also observed between the photosynthetic efficiency (α) and the ψpd of plants, but only under moderate to severe water stress conditions. Grass species had different response to water stress graded in the following order: Pappostipa chrysophylla > Festuca gracillima > Rytidosperma virescens > Poa dusenii > Bromus setifolius. These results can assist to understand the natural spatial distribution of these species under arid conditions, to predict their performance under changing climate, and to select proper species for restoration plans in steppe grasslands.

Structure of plankton and waterbird communities under water level fluctuations: two case studies in shallow lakes of the Patagonian steppe

Structure of plankton and waterbird communities under water level fluctuations: two case studies in shallow lakes of the Patagonian steppe

Extending Grime's CSR model to predict plant demographic responses across resource availability gradients: evidence from the patagonian steppes

Sexual reproduction, growth, and survival are crucial demographic strategies for plant population viability. Here, we propose a conceptual model predicting demographic responses of species based on their ecological strategy and the heterogeneity of environmental conditions within a biogeographical unit and then applied it to a case study from a 5˚ latitudinal gradient in the Patagonian steppes. We also aim to disentangle genetic from environmental effects on demographic responses. We performed in situ and common garden experiments with two species from six local populations of the Occidental Phytogeographical District of the Patagonian steppes. Species differ in key ecological traits, and thus fit into Grime's model for evolutionary strategies in plants: one as competitive species and the other as stress‐tolerant species. We calculated population growth rate (λ) and performed elasticity analyses to compare the contribution of each demographic strategy to population fitness between species and among local populations distributed along 600 km latitudinal gradient with differences in mean annual precipitation (MAP). We highlight four results. First, the competitive species change from sexual reproduction to growth as MAP increases. Second, the stress‐tolerant species relied on growth and survival along the MAP gradient. Third, interannual variation in resource availability modulated demographic responses for both strategies. Fourth, based on the comparison of the in situ and common garden experiments, we submit that demographic responses were genetically driven. Our study shows that demographic responses can be roughly predicted by the ecological strategy across environmental gradients. We show that differences arise not only between species, but also were genetically driven differences within species among local populations. Scaling up plant‐level responses to population‐level dynamics allows for a process‐based understanding of current and future biogeographical species organization. Furthermore, conservation and restoration efforts should be guided by demographic strategies underlying population viability.

Nitrogen rather than water availability limits aboveground primary productivity in an arid ecosystem: Substantial differences between grasses and shrubs

AbstractChanges in water and nitrogen availability can affect the structure and function of arid ecosystems. How these resources affect aboveground primary productivity (ANPP) remains far from clear. We examined the N and water limitation of ANPP from the species to the community level and the response of ANPP to annual precipitation in a Patagonian steppe. We conducted a 7‐year field experiment with water addition (+W), nitrogen addition (+N) and +NW. Destructive methods for grasses and allometric relationships for shrubs were used to assess ANPP and vegetation indices (NDVI and MSAVI2) to estimate community ANPP. An increase in ANPP of one grass species (Papposstipa humilis) and a decrease of the grass Poa ligularis under +N were observed. Some shrub species exhibited mortality under nitrogen addition. Nitrogen exerted a positive effect on grass ANPP and amplified the sensitivity of grass ANPP to annual precipitation. However, +N had not effects on the shrub ANPP and shrub ANPP‐precipitation relationship. Water addition by itself had no effect on ANPP for either shrubs or grasses. However, shrubs responded positively to an unusually wet year regardless of treatment and were also more sensitive to changes in annual precipitation than grasses. Total ANPP increased significantly in +N relative to the C and +W but without changes in the sensitivity to annual precipitation. The results suggest that the responses of grasses and shrubs to water inputs are driven by soil moisture redistribution and rooting depth and that grass and community ANPP are more limited by N than by water.

Tracking floristic archetypes of Patagonian steppes

AbstractQuestionsThe classification of plant communities is a well‐established practice in ecology. However, the factors that determine the distribution of common species and the extent of their dominance and overlap are still being debated. Large‐scale studies based on field data are of great interest in the face of biodiversity changes and climate change impacts. This research was designed to answer the following two questions: What are the dominant plant communities in the Patagonian steppes and how do they relate to environmental features, as measured by latitude, longitude, altitude, mean annual precipitation and mean temperature? What have been the recent changes in plant communities in terms of expansion and contraction of different types of communities?LocationPatagonian steppes (South America).MethodsWe used a large database of species‐by‐species vegetation cover from 426 monitoring plots in the South American Patagonian steppes, surveyed between 2007 and 2019, with two different assessment dates at least 5 years apart. We applied archetypal analysis to identify different vegetation compositions at a regional scale (called floristic archetypes) and to track their changes over time. In addition, we analyzed the relationship between floristic archetypes and spatial and meteorological variables to assess the association between floristic composition and the environmental context.ResultsSeven floristic archetypes were identified in the Patagonian steppes. The dominant and most widespread floristic archetype showed an expanding pattern in floristic trajectories and was positively associated with mean annual temperature. This floristic archetype was characterized by both drought‐ and grazing‐tolerant species. Two floristic archetypes located at the longitudinal extremes showed decreasing relative participation in the vegetation configurations, and the archetype located towards the west showed a positive relationship with annual precipitation, suggesting a threatened scenario in the face of drier conditions. Southern floristic archetypes either showed a slight decrease or remained stable.ConclusionsPatagonian steppes are dominated by both drought‐ and grazing‐tolerant species communities and their spatial distribution is expanding across different biomes, whereas the more forage‐preferred species were associated with a decreasing floristic archetype. A projected drier and hotter climate scenario may potentiate this pattern. The floristic archetypes framework has potential as a monitoring tool for tracking changes in vegetation composition at a mesoscale and for identifying hotspots of vulnerable vegetation in the face of environmental changes.

Compost promotes biocrust and plant growth in greenhouse cocultures for dryland restoration

Biocrusts and plants are the main ground cover and provide multiple ecosystem functions in arid and semiarid areas. As land degradation worsens and waste management is ever more pressing, the use of composted waste appears as a sustainable restoration practice to enhance vegetation reestablishment, but its effects on biocrusts still remain largely understudied. Moreover, developing appropriate methods for the co‐introduction of plants and biocrusts can be an emerging approach to reconstruct the biocrust/plant interaction and their associated functions. We evaluated the effect of different compost types on biocrust and plant cocultivations. We performed a greenhouse mesocosm experiment using urban organic solid waste and sewage sludge composts to grow a moss‐dominated biocrust and seedlings of two pioneer shrubs (Senecio filaginoides and Acaena splendens) in the Patagonian steppe. Both compost types successfully enhanced biocrust cover and chlorophyll a development, with cultured biocrusts being compositionally similar to the natural inoculum. Only the addition of composted sewage sludge enhanced seedling growth, and biocrusts had significant but opposite effects (positive/negative) on the two plant species we used for experimentation. This difference in the biocrust/plant interaction outcome was likely mediated by the significant influence of biocrusts on the relative availability of ammonium and nitrate and possible plant species‐specific preferences for different inorganic nitrogen forms. We conclude that the application of sewage sludge compost effectively improves the success of biocrust and plant cocultures, but species‐specific differences in the performance of seedlings growing in biocrusted soils impose limits on attempts to promote biocrust and plant joint restoration.

Phenotypic plasticity in leaf traits in response to experimental precipitation increase: Wettability, foliar water uptake and gas exchange

AbstractWater availability is one of the factors affecting plant growth and development, especially in arid and semiarid environments. Changes in precipitation due climate change alter water availability to plants impacting on plant physiology. Numerous studies have focused on plant response to reduced precipitation and less on the effects of increased precipitation. The main objective of this study was to evaluate biophysical and physiological leaf traits in response to experimental water addition in four dominant shrubs and one grass species in a Patagonian steppe, during the dry season. The experiment consisted of two treatments: control and water addition, increasing the average annual rainfall by 25% during 6 years. We measured leaf wettability, water status, transpiration, photosynthesis, stomatal conductance, water use efficiency and foliar water uptake (FWU). In addition, we determined the phenotypic plasticity index of these evaluated traits. We expected lower FWU and higher transpiration and photosynthesis rates due changes in leaf surface properties under water addition treatment. All study species responded significantly to treatment with higher loss of water per transpiration and lower FWU. Also, all species increased photosynthesis rate and water use efficiency (WUE). However, water potential and leaf wettability did not change with higher precipitation. Thus, higher phenotypic plasticity was observed in functional than in morphological traits. Since functional traits were more sensitive than leaf surface traits, plants may quickly take advantage when environmental conditions tend to be more favourable to growth. Our findings suggest that plants of Patagonian steppe have adaptive ability to respond to environmental changes through plastic responses.

Threat patterns for endemic plants of Argentina reveal disparity of vulnerability and protection among spatially associated species groups

Given the accelerated rate of environmental degradation and climate change, there is an urgent need to protect biodiversity, especially endemic species with restricted ranges. However, which areas should be prioritized for protection remains a critical issue. A common approach to prioritizing conservation is to rank areas using species-level metrics. Nevertheless, biodiversity and threat patterns can become complex when the amounts of data increase. Here, we analyzed the distribution of 1570 Argentinean endemic plants using clustering of spatially associated species to disentangle distribution and threat patterns. We explored vulnerability levels in each cluster using mean values of species-level metrics of vulnerability, relating values obtained to the regions and environments they occupy. For each cluster we also identified its hotspots and evaluated the effectiveness of the current protected area network for their conservation. Results yielded nine main clusters, mostly differentiated by their geographic distribution and by the ecoregions they occupy. Metrics revealed disparity in vulnerability levels among clusters, with the highest values recorded for clusters related to the Central Puna in northwestern Argentina, to the Espinal, Humid Pampas, and Low Monte in the east of the country, and to the Patagonian steppe in the south. Likewise, coverage by protected areas was low for most hotspots, with the lowest values recorded for the Patagonian cluster. In particular, for hotspot of this cluster, located along the Patagonian steppe in southern Chubut and northeastern Santa Cruz provinces, analyses showed that it has both high levels of vulnerability and low levels of protection, giving it the highest conservation priority of the entire pool analyzed. Our findings identify gaps in the current protected area network and highlight key areas in need of conservation policies and strategies, both in situ and ex situ, to protect the endemic plants of Argentina.

High Trypanosoma cruzi prevalence in armadillo (Zaedyus pichiy; Xenarthra: Chlamyphoridae) populations from Mendoza, Argentina.

Armadillos are considered important reservoir hosts for Trypanosoma cruzi, the causative agent of Chagas disease. The first report of T. cruzi infection in pichis (Zaedyus pichiy), a small armadillo species endemic to central Argentina and Chile, dates back to 1935. However, more recent reports on T. cruzi in this species are scarce. The objective of this study was to assess T. cruzi infection and parasite load in Z. pichiy from Mendoza Province, an area endemic to human Chagas disease. Blood samples were obtained in 2014-2016 from pichis from Lavalle (low Monte), Malargüe (Patagonian steppe), and San Carlos (ecotone) departments, Mendoza Province, Argentina. The detection and quantification of T. cruzi was performed through qPCR amplification using satellite primers. Of the 265 analyzed samples, 201 (76%) were positive for T. cruzi. Parasite loads varied between < 0.1-55.8 parasite-equivalents/mL (par-eq/mL), with a median of 1.1 par-eq/mL in quantifiable samples. The prevalence was similar in Malargüe and Lavalle (85-94%), but significantly lower in pichis from San Carlos (50%). Animals from Lavalle captured after hibernation had significantly higher parasite loads (median 2.0 par-eq/mL). In Malargüe, T. cruzi infection and parasite loads were significantly lower before than after hibernation in 2016. The high prevalence and low median parasite load suggest a chronic and persistent infection of T. cruzi in pichis. Regional differences and a marked increase in precipitation during 2015-2016 could have influenced annual and seasonal infection rates of this vector-borne disease.

Individual‐plant selectivity by sheep in drylands scales‐up at plant population level and controls the forage supply and its accessibility

Abstract Diet selectivity by domestic herbivores controls plant community structure and dynamics and may induce rangeland degradation, particularly in drylands. However, management decisions frequently ignore herbivore selectivity. Here, we studied how grass morphology controls sheep selectivity for individual plants, and how this selectivity interacts with grazing intensity to determine population plant‐size distributions and the forage supply. In Patagonian steppes, we manipulated the plant morphology (size and standing‐dead proportion) of three dominant grass species differentially preferred by sheep for 4 years. Then, we evaluated how these morphological alterations affected intra‐ and inter‐specific preference patterns. We also evaluated how grazing intensity (ungrazed, moderate grazing and intensive grazing) affected the plant‐size distribution of the three species, the forage supply, and its accessibility. For the highly preferred species, herbivores selected plants that were either naturally or experimentally short, with low proportion of standing‐dead biomass. In contrast, morphological changes did not alter the within‐species selectivity of the least preferred species. Grazing intensity strongly changed the population plant‐size distribution of preferred species in ways that resembled the experimental manipulations of morphology. Moderate grazing showed the greatest morphological heterogeneity among individuals. When integrating the green biomass of forage species' individuals at ecosystem level, we found that the forage supply was the highest in ungrazed sites and decreased as grazing intensity increased. However, considering the dissuading effect of the standing‐dead proportion of plants, the accessible forage was the highest under moderate grazing. Synthesis and applications. Our findings (i) showed that, within preferred species, sheep selectivity at individual‐plant level is controlled by morphological characteristics that determine accessibility to green high‐quality biomass. This effect was as important as that of species identity; (ii) empirically proved plant–animal positive feedback at individual level; and (iii) revealed how the individual‐plant selectivity scales‐up at population level and controls the forage supply, but also its accessibility. Our complementary approach generates critical knowledge for developing management practices to control key forage species defoliation and to adjust the grazing pressure to the offer of accessible forage, avoiding the common carrying capacity overestimation. These aspects are essential for sustainable production in grazed drylands.

Exotic and native species used by traditional populations of the Patagonian steppe: An approach based on redundancy and versatility

AbstractThe utilitarian redundancy model has been used to indirectly verify the resilience of useful plant knowledge systems used by local populations. From the bases of this model and the hypothesis of diversification, we can think that exotic species can enter socio‐ecological systems to fill gaps and reduce the use pressure on native species. In this study, we want to draw a picture of the redundancy of plant species used by three traditional populations of the Patagonian steppe for medicinal, fuel, and edible purposes. We also compare the use of pressure and the degree of uniqueness of native and exotic species, using redundancy and versatility as proxies. Our results show that, according to utilitarian redundancy, the plant knowledge systems of the three communities seem to have similar adaptive capacity to provide options for responding to change; for example, by allowing certain elements to compensate/substitute for the loss of others. We found that native species are the most unique and may be under greater use pressure than exotic ones. Thus, our results point to the importance of conserving the steppe Patagonian native environment for the survival of traditional populations. Our study can be used to establish priority botanical species for conservation in the Patagonian steppe.

Digestive plants in a Mapuche community of the Patagonian steppe: multidimensional variables that affect their knowledge and use

Background: In a rural Mapuche community of the Patagonian steppe (Chubut, Argentina), we analyzed how the use and popularity of digestive plants are affected by their aroma, the presence of dual medicinal-edible uses, their digestive versatility, biogeographical origin and accessibility. Methods: Free listing and in-depth interviews were conducted with 25 collaborators, complemented with participant observation and walks in the field. Quantitative indices, non-parametric methods (Binomial and Chi-square tests, p &lt; 0, 05) and generalized linear models (GLM, Omnibus test, p &lt; 0, 05) were performed. Results: Local collaborators use 61 digestive plants, including a similar number of native and exotic species. Most are used for only one type of digestive use, are very accessible and have aroma. There are as many species with dual use as without dual use. Exotic species generally have more aroma than native ones. Only exotic species are highly accessible. Species with dual uses are mainly used as condiments. Digestive-only species could or could not have aroma. The popularity of species is only affected by their digestive versatility and aroma, mainly for exotic ones. Conclusions: Local pharmacopoeia reflects aspects that account for its cultural resilience, including a high richness of native and exotic digestive plants, many of which are used for specific ailments. The species have been selected from the joint evaluation of biophysical and sociocultural variables that influence their knowledge and forms of use. These variables and perceptions would also allow diversification in response to changes, forming part of a bio-cultural legacy unique to Patagonia. Keywords: Mapuche medicinal flora, Patagonia, popularity, cultural resilience.

Pinus contorta Alters Microenvironmental Conditions and Reduces Plant Diversity in Patagonian Ecosystems

Pinus contorta is considered one of the most invasive tree species worldwide, generating significant impacts on biodiversity and ecosystems. In several Patagonian ecosystems in southern Chile, it has escaped from plantations established mainly in the 1970s, and is now invading both forests and treeless environments. In this study, we evaluated the impact of the invasion of P. contorta on microenvironmental conditions in Araucaria araucana forest and Patagonian steppe ecosystems, and assessed how these changes related to the richness and abundance of native and non-native plant species. In each ecosystem, 24 plots of 100 m2 were established along a gradient of P. contorta biomass, where 18 environmental variables and the composition of native and non-native vegetation were measured at a local scale. Our results indicated that increased pine biomass was associated with differences in microclimatic conditions (soil and air temperature, photosynthetically active radiation (PAR), and soil moisture) and soil properties (potassium, nitrate, pH, and litter accumulation). These changes were ecosystem dependent, however, as well as associated with the level of invasion. Finally, the reduction in the richness and abundance of native plants was associated with the changes in soil properties (accumulation of leaf litter, pH, and organic matter) as well as in the microclimate (minimum air temperature, PAR) generated by the invasion of P. contorta. Overall, our results confirm that the invasion of P. contorta impacts microenvironmental conditions (i.e., canopy cover, litter accumulation, minimum air temperature, and maximum soil temperature) and reduces native plant diversity. For future restoration plans, more emphasis should be given to how environmental changes can influence the recovery of invaded ecosystems even after the removal of the living pine biomass (i.e., legacy of the invasion).

Effects of the cessation of fish-processing effluent discharges on the soil microbiome associated with saltbush patches

In the present scenario of global water scarcity, treated wastewater from some industries -such as the fishing industry- is an interesting resource to consider for irrigation purposes. In a previous study in a Patagonian steppe site dominated by the native halophile shrub Atriplex lampa, fish-processing effluent discharges induced soil salinization, changes in the soil prokaryotic community structure and a reduction of its diversity. In this study we aimed to test if a period without effluent discharges allowed the recovery of the microbial community in soils from this Patagonian steppe site, by analyzing the prokaryotic communities of A. lampa patches during the fish-processing effluent discharges and four years after cessation of such discharges (sites ES1 and ES2, respectively). Additionally, we aimed to test if the soil prokaryotic community of A. lampa patches either exposed to effluent discharges (ES2) or from a coastal dune site (Du) share a common core microbiome as a result of their same shrub cover and similar soil salinity. Regarding the comparison between ES1 and ES2, prokaryotic richness estimators (Chao1 and ACE) increased significantly in ES2. In addition, the cessation of effluent discharges induced a rise of Actinobacteria, and a recovery of some oligotrophic phyla, which had decreased during the effluent discharge period. Regarding the comparison between ES2 and Du, the core microbiome in soils associated with A. lampa patches consisted of just a few taxa. Moreover, Du site revealed a signature of dune-specific prokaryotes comprising halotolerant/halophilic microorganisms adapted to marine and intertidal environments, whilst no such signature was observed in ES2. Overall, our results contribute to unraveling the soil prokaryote diversity associated to A. lampa as well as to a better understanding of the microbiomes from saline environments, having valuable implications for a sustainable reuse of fishing industry wastewaters for irrigation.

Acumulación de biomasa en juveniles de arbustos nativos expuestos a distintos niveles de luz asociados a esquemas de manejo forestal de coníferas exóticas

Pinus ponderosa plantations established in the Patagonian steppe put ecosystem functions at risk if they are not properly managed. The response of shrubs to light variations caused by forest plantations and forestry interventions may influence their ecological role. In this work we evaluated the total biomass accumulation dynamics of calafate (Berberis microphylla) and mamuel choique (Adesmia volckmannii) at 20, 60 and 100% irradiance, and their response to the light increase that would occur after interventions such as thinning and harvesting. For each species we evaluated 1) the relationship between biomass and diameter at the base of the stem, 2) the biomass dynamics during two growing seasons in the three irradiance conditions, and 3) the early response to light increase in plants subjected to irradiances of 20 and 60%. In addition, 4) we compared the levels of irradiance that the proposed forest management schemes for the region would suppose with those evaluated here. For both species, biomass and diameter were linearly related and biomass accumulation was lower at 20% irradiances. Calafate showed a tendency to accumulate more biomass at 100%, and mamuel choique, at 60%, although no species showed differences between these irradiances. Whereas calafate from 20% irradiance only increased its biomass by increasing irradiance to 100%, mamuel choique did so by increasing it to 60%. These results suggest that the two species, at least in the juvenile phase, may acclimate to shade, and that mamuel choique would respond better to partial increases in light, as in the case of thinning. The response of calafate suggests that the proposed management, which irradiance levels would be lower than those evaluated here, would not be optimal for its development.

Nest predation in Patagonian wetlands: predator assemblage and microhabitat characteristics

ABSTRACT Multiple factors influence predation risk, ranging from habitat conditions to the composition and behaviour of predators. Although these factors are well documented for forest ecosystems, there is little evidence for wetlands, especially within Patagonia. Using artificial nests and camera traps, we documented the nest predation rates and predator assemblage of birds nesting in wetlands of the Patagonian steppe. We also determined the effect of vegetation cover on nest survival and studied the variation in predator groups according to nest placement: nests located in an open wetland, peripheral grassland to the wetland, and nests located in shrubs at different heights. We found 84% of nests failed, counting birds, mice, and armadillos as the main predators. Vegetation cover affected predation events of birds and small mammals, but not those of larger mammals. In turn, small mammals preyed on nests exclusively located in peripheral grassland, medium mammals preferred nests placed in open wetlands, and predation by birds was irrespective of open wetlands and grassland. We also found differences in nest predator assemblage between nests placed on the ground and in shrubs, with birds being the main predators of nests located above ground. These results can be attributed to differential habitat use and movement patterns specific to each predator group. Therefore, the identity, density, and behaviour of predators should be taken into account when planning conservation strategies for birds breeding in wetlands.

Coexistence of grasses and shrubs in Patagonian steppes. Norm or exception?

AbstractQuestions(1) Is the co‐dominance of grasses and shrubs a general feature of Patagonian steppes? (2) At a local scale, does it change with domestic grazing intensity or decadal changes in precipitation?LocationsQuestion 1. Patagonia region in southern South America. Question 2. Shrub–grass steppes (45°24′S, 70°17′W) subjected to different grazing intensity for decades.MethodsWe sampled vegetation to estimate perennial grass and shrub cover at two scales: regional and local. At the regional (phytogeographical) scale, we sampled grazed steppes under different climates and soils (n = 324 sites over ca. 487,000 km2). At the local scale, we sampled paddocks subjected to known grazing management, from commercial intensive densities of sheep to total (experimental) exclusion. Also, in the same site, we sampled permanent plots (25 years old) in a grazing exclosure to study the effects of precipitation variation.ResultsMixed communities are the predominant form of community organization in the Patagonia region. At the regional scale, shrub cover was negatively related to grass cover and communities where shrubs had higher cover than grasses represent 54% of the data set. At the local scale for an arid steppe, perennial grasses had higher cover than shrubs, regardless of grazing pressure. The shrub‐to‐grass ratio was increased only by intensive grazing. Permanent plots in a grazing‐excluded paddock indicate that decadal xeric or humid climate periods decrease or increase total cover, respectively. Surprisingly, the relative shrub‐to‐grass ratio did not change significantly.ConclusionsAlthough perennial grasses and shrubs cover are negatively correlated, they coexist in the Patagonian steppes under a wide range of climate, soil and grazing conditions. At a local scale, selective herbivory promotes species replacement but did not substantially change the life‐form covers. Water shortages, as well as periods of water surplus, similarly affect both life forms without compromising their coexistence.