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Hydrogeochemical and microbiological parameters of groundwater samples in the Paipayales agricultural community in western Ecuador were studied to evaluate groundwater origin, contamination, and suitability for domestic use and irrigation. The water wells studied are typically shared by multiple families which account for 37% of the total community population. A total of 31 parameters of water samples from the wells used by the community were analysed by four laboratories at the ESPOL University. The parameters analysed included microbiological and chemical compounds, along with physical characteristics typically influencing water quality. As regards the World Health Organization (WHO), U.S. Environmental Protection Agency (EPA), and Ecuadorian standards, all samples failed to meet the required concentrations for at least one compound. The chemical analysis showed eight elements (cadmium, aluminium, ammonia, iron, manganese, chloride, and bromide) exceeded the maximum limits for drinking water in at least one well. Seventy percent of sampled wells failed to meet the maximum permissible limits for at least one chemical parameter. Water in all wells showed the presence of microbiological contaminants. The high natural groundwater salinity limits the ability to use this groundwater for irrigation purposes. Water in open and closed wells shows different hydrochemical and microbiological patterns. The presence of domestic animals and the lack of protection for wells may influence the quality of water. It is highly recommended that the authorities increase water supply and storage capacity to improve the availability of drinkable water in rural communities in the area.

Abstract Tropical South American climate is influenced by the South American Summer Monsoon and the El Niño Southern Oscillation. However, assessing natural hydroclimate variability in the region is hindered by the scarcity of long-term instrumental records. Here we present a tree-ring δ 18O-based precipitation reconstruction for the South American Altiplano for 1700–2013 C.E., derived from Polylepis tarapacana tree rings. This record explains 56% of December–March instrumental precipitation variability in the Altiplano. The tree-ring δ 18O chronology shows interannual (2–5 years) and decadal (~11 years) oscillations that are remarkably consistent with periodicities observed in Altiplano precipitation, central tropical Pacific sea surface temperatures, southern-tropical Andean ice core δ 18O and tropical Pacific coral δ 18O archives. These results demonstrate the value of annual-resolution tree-ring δ 18O records to capture hydroclimate teleconnections and generate robust tropical climate reconstructions. This work contributes to a better understanding of global oxygen-isotope patterns, as well as atmospheric and oceanic processes across the tropics.

Abstract Background Natural and anthropogenic wildfires burn large areas of arid and semi-arid forests with significant socio-economic and environmental impacts. Fire regimes are controlled by climate, vegetation type, and anthropogenic factors such as ignition sources and human-induced disturbances. Projections of climate and land-use change suggest that these controlling factors will change, altering fire regimes in the near future. In the southern Central Monte, Mendoza, Argentina, the factors that modulate the fire temporal and spatial variability are poorly understood. We reconstructed the fire history of southeast of Mendoza from 1984 to 2023 and investigated the relationships between fire extent and climate variability at seasonal and interannual scales. Burned areas were determined using Google Earth Engine by processing Landsat 5-TM, Landsat 7-ETM+ , and Landsat 8-OLI-TIRS sensor imagery. Results The region exhibited high spatial and temporal variability in fire occurrence, being a mosaic of areas with different fire histories and recovery times. Between 1985 and 2023, fire recurrence ranged from sites unburned to sites with up to 14 fires. The occurrence of large fires was strongly favored by a combination of a year with abundant spring–early summer precipitation, which favors fuel accumulation, followed by a year of low spring–early summer precipitation. Precipitation and burnt area showed a very pronounced 6–7 year cycle, suggesting a dominant climatic control on fire occurrence. Conclusions Fire distribution in southeastern Mendoza forests is not homogeneous, resulting in a mosaic of patches with different fire histories. This heterogeneity may be related to vegetation patterns and land use. The temporal variability of fires is strongly influenced by climate variability, which would promote fuel production and subsequent drying. Large fires are concentrated in periods of high interannual precipitation variability. Climate change scenarios predict an increase in temperature and precipitation variability in the region, suggesting future changes in fire dynamics. Our results contribute to the development of fire guidelines for southeastern Mendoza forests, focusing on periods of wet years followed by dry years that favor fire occurrence and spread.

Non sustainable land uses are disturbing natural habitats and wild animals’ ecology worldwide. Nevertheless, the sensitisation of key actors combined with research and a consequent management can influence decision-making and improve animals’ well-being. COVID-19 has influenced the number of interactions with wildlife in urban environments and the ESPOL Polytechnic University is a university campus that holds forested areas in Guayaquil, Ecuador. We implemented an environmental education course with an empathetic approach for the security guards of the university. We used questionnaires to evaluate their attitudes and knowledge on wildlife before and after the sensitisation course. In addition, we registered the incidences of native fauna resulting from the guards’ collaborations and we designed management strategies according to the data gathered. The guards showed an improvement in their knowledge of the issues covered (n = 81–87; X̄ = 163.4%) and an increased preference for wild and native fauna after the sensitisation course (n = 67; 151.6%). Furthermore, the collaborations of guards with the Biodiversity Unit of the university concerning animal-human interactions increased, as did the supporting actions towards the well-being of native animals. Moreover, the information about direct and indirect interactions with wildlife included reports on traces of large to medium animal activity and a record of illegal hunting of Choloepus hoffmanni for bushmeat consumption. Obtained data sustained adaptive management actions such as signalling and restrictions in use. We recommend educating key actors with an empathetic approach, developing critical skills and promoting collaborations to reduce human impacts in wild areas.

Wildlife trafficking and human–wildlife conflict are major causes of species decline. The illegal nature of wildlife trafficking makes it hard, and sometimes dangerous, to study. ‘Mansión Mascota’ is a veterinary clinic in Guayaquil, Ecuador, which, through agreement with the Ecuadorian Ministry of the Environment, receives confiscated wildlife for treatment. Mansión Mascota also receives injured and abandoned wildlife brought in by the authorities and the public. Between January 2018 and September 2022, the clinic received 3212 wild animals from ≥171 taxa, including mammals, birds, reptiles, and amphibians. Through the classification of records based on reported use, native distribution, and evidence of capture/pet keeping, we were able to classify 1127 animals of 68 species as subject to wildlife trafficking. Turtles were the most abundant group (69%). The majority of turtles (91%) and primates (80%) were of Amazonian origin, whereas 90% of psittacines and 97% of carnivores had potential coastal origins. Threatened and conservation-dependent species were common in the traffic. Furthermore, ≥955 animals of 106 species were brought to the clinic due to anthropogenic wildlife conflict. Trafficking, combined with the high number of injured animals, highlights the synergistic threats facing wildlife in Ecuador.

En el Monte Central, Neltuma flexuosa es la principal especie arbórea con importantes funciones ecológicas y socio-culturales. En esta región, la ganadería integrada al bosque nativo, en combinación con prácticas silvícolas, es la forma más extendida de utilización del bosque. Estas actividades humanas pueden generar cambios en la dinámica del bosque que, a su vez, está condicionada por la disponibilidad hídrica. Nuestro objetivo fue evaluar el patrón de crecimiento de árboles de N. flexuosa del Monte Central y asociarlo a distintos usos del suelo y al clima. Se emplearon métodos dendrocronológicos para analizar muestras de madera extraídas en áreas destinadas a conservación, uso ganadero y extracción de madera. Se observó que los árboles del área con extracción de madera crecieron entre los años 1977 y 2000 aproximadamente dos veces más que los individuos de los campos ganaderos y del área protegida, para luego reducir su crecimiento a niveles similares a los registrados en las otras dos áreas. Mientras las máximas tasas de crecimiento en el área de extracción se alcanzaron entre los 20 y 40 años de edad de sus individuos, en el área protegida y en los campos ganaderos se presentaron alrededor de los 70 años. Además, se observó una asociación positiva pero baja de las precipitaciones con el crecimiento. Los resultados indican que los usos del suelo han afectado el patrón de crecimiento radial de los árboles de N. flexuosa. La capacidad de rebrote de la especie habría facilitado su recuperación a nivel de árbol, lo cual combinado con un cambio en la intensidad de uso humano posibilitó la recuperación de la población de N. flexuosa y el restablecimiento del bosque. Estos resultados sugieren que la ganadería extensiva y la extracción de madera para uso doméstico son actividades compatibles con el uso sustentable del bosque.

We present geodetic mass-balance estimates for ten glaciers (22.6 ± 1.1 km2) around Volcán Domuyo between 1962 and 2020 (and 46 glaciers covering 29 ± 1.5 km2 between 1984 and 2020), derived from airborne, ASTER and Pléiades imagery. Overall, we find a slightly negative mass balance (−0.15 ± 0.09 m w.e. a–1) for the entire 1962–2020 time span. A closer inspection of sub-periods reveals, however, an increasingly negative mass balance with time. The Domuyo glaciers shifted from a moderately positive mass balance of +0.28 ± 0.13 m w.e. a–1 between 1962 and 1984, to a strongly negative mass balance of −0.99 ± 0.19 m w.e. a–1 between 2012 and 2020. An increase in summer temperatures and a decrease in winter precipitation during the last four decades are likely drivers of the observed glacier changes. We support this finding by implementing a minimal glacier model, relying solely on monthly precipitation and air temperatures. The mass-balance evolution detected in Volcán Domuyo is consistent with other sites spread across the Central Andes, suggesting rapidly increasing glacier wastage impacts are occurring at a geographically wider scale.

The Desert Andes contain >4500 ice masses, but only a handful are currently being monitored. We present the mass changes of the small mountain glacier Agua Negra (1 km2) and of the rest of glaciers in the Jáchal river basin. Remote-sensing data show Agua Negra glacier lost 23% of its area during 1959–2019. Glaciological measurements during 2014–2021 indicate an average annual mass balance of −0.52 m w.e. a−1, with mean winter and summer balances of 0.80 and −1.33 m w.e. a−1, respectively. The Equilibrium Line Altitude (ELA) is estimated to be 5100 ± 100 m a.s.l., which corresponds to an Accumulation Area Ratio (AAR) of 0.28 ± 0.21. Geodetic data from SRTM X and Pléiades show a doubling of the loss rate from −0.32 ± 0.03 m w.e. a−1 in 2000–2013, to −0.66 ± 0.06 m w.e. a−1 in 2013–2019. Comparatively, the ice losses for the entire Jáchal river basin (25 500 km2) derived from ASTER show less negative values, −0.11 ± 16 m w.e. a−1 for 2000–2012 and −0.23 ± 14 m w.e. a−1 for 2012–2018. The regional warming trend since 1979 and a recent decline in snow accumulation are probably driving the observed glacier mass balance.

We present the first records of the post-release follow-up and monitoring of a rehabilitated two-toed sloth (Choloepus hoffmanni) as well as freezing behavior and an inferred antagonistic interaction for this species. Two-toed sloths are nocturnal and arboreal mammals whose survival relies on their capability to remain undetected by predators. Nevertheless, in the Guayas province of Ecuador, they are among the most common mammal species in rehabilitation centers. The liberation of animals back to the forest is the main goal of rehabilitation, while the follow-up of post-release human support of animals facilitates their re-establishment in their natural habitat. Follow-up, direct observation, and Bluetooth-based monitoring of the two-toed sloths secured the survival of this species in this part of Ecuador. The range of detectability of the device used indicates its suitability for tracking low-mobility animals. After the first five days, the number of trees used per day increased, and 19 trees within 1152 m2 were visited. Daylight and movement time range showed a correlation towards detectability. The follow-up effort allowed for keeping the two-toed sloth safe for 10 days after release. Due to the difficulty monitoring nocturnal animals, economic constraints in conservation, accessibility, and safety of the animals, biodegradable Bluetooth-based backpacks are recommended to ease the location of the animal and support its survival in the wild.

Soil moisture (SM) is a crucial factor in the water cycle, sustaining ecosystems and influencing local climate patterns by regulating the energy balance between the soil and atmosphere. Due to the absence of long-term, in-situ measurements of SM, studies utilizing satellite-based data and tree-ring analysis have become valuable in assessing variations of SM at regional and multi-century scales, as well as determining its effects on tree growth. This information is particularly pertinent in biodiversity hotspots made up of semi-arid ecosystems currently threatened by climate change. In the Mediterranean Chile region (MC; 30°–37° S), an ongoing megadrought since 2010 has resulted in a significant decline in the forest throughout the area. However, the impact of SM on tree growth at a multi-species and regional level remains unexplored. We analyzed a new network of 22 tree-ring width chronologies across the MC to evaluate the main spatiotemporal tree-growth patterns of nine woody species and their correlation with SM, using PCA. We also reconstructed the SM variations over the past four centuries and assessed its connection with large-scale climate forcings. Our results indicate that the primary growth patterns (PC1) explained 27% of the total variance and displayed a significant relationship with SM between 1982–2015 ( r = 0.91), accurately reflecting the current megadrought. The tree-ring SM reconstruction covers the period 1616–2018 and shows a strong decrease around the year 2007, revealing an unprecedented recent change in aridity with respect to the last four centuries. The intensity of the South Pacific subtropical anticyclone, which primarily owe their existence to the subsiding branch of the Hadley Cell, appears as the primary climatic mechanism correlated with the reconstruction and the present aridity conditions in MC. The current SM conditions align with anticipated aridity changes in MC, providing a bleak perspective of future regional climate.

Glacier ice thickness is crucial to quantifying water resources in mountain regions, and is an essential input for ice-flow models. Using a surface velocity inversion method, we combine ice thickness measurements with detailed surface elevation and velocity data, and derive ice thickness and volume estimates for the Monte Tronador glaciers, North Patagonian Andes. We test the dependence of the inversion model on surface slope by resampling glacier slopes using variable smoothing filter sizes of 16–720 m. While total glacier volumes do not differ considerably, ice thickness estimates show higher variability depending on filter size. Smaller (larger) smoothing scales give thinner (thicker) ice and higher (lower) noise in ice thickness distribution. A filter size of 300 m, equivalent to four times the mean ice thickness, produces a noise-free thickness distribution with an accuracy of 35 m. We estimate the volume of the Monte Tronador glaciers at 4.8 ± 2 km3 with a mean ice thickness of 75 m. Comparison of our results with earlier regional and global assessments shows that the quality of glacier inventories is a significant source of discrepancy. We show that including surface slope as an input parameter increases the accuracy of ice thickness distribution estimates.

Glaciers and the periglacial environment in Argentina have been protected by the Law since 2010. This legislation required the development of the first National Glacier Inventory (NGI), which was officially presented in May 2018 and based on satellite images spanning between 2004 and 2016. Here, we present the methods and results of the NGI, summarize the glaciers’ morphological and spatial characteristics, and compare our results to previous regional and global inventories. The NGI reveals an impressive variety of ice masses including rock glaciers, permanent snowfields, mountain and valley glaciers with varying amounts of debris-cover and large outlet glaciers. The Argentinean Andes contain 16 078 ice masses covering an area of 5769 km2 between 200 and 6900 m a.s.l. Comparison of the combined national inventories of Argentina and Chile (~30 000 glaciers and 28 400 km2) with the Randolph Glacier Inventory 6.0 for the Southern Andes (~16 000 glaciers and 29 400 km2), shows that there are large differences in extent and number of glaciers in some sub-regions. The NGI represents an improvement for a better understanding of Argentina's freshwater reservoirs and provides detailed information for the preservation and study of ice masses along 4000 km of the Southern Andes.

Resilience to drought is crucial for tree survival under climate change. Here, DeSoto et al. show that trees that died during drought were less resilient to previous dry events compared to surviving conspecifics, but the resilience strategies differ between angiosperms and gymnosperms.

Abstract We present a case of Sarcoptes and canine distemper virus (CDV) infection in a white-nosed coati (Nasua narica) that was trapped in the dry tropical forest of Cerro Blanco reserve, located in the coastal region of Ecuador. Sarcoptic mange is a highly contagious and zoonotic disease with worldwide distribution that causes epidemics. Mange is produced by Sarcoptes mites that causes severe epidermal damage. Secondary infections and physiological constrictions without treatment can lead to death of the host. In addition, cooccurrence of canine distemper virus was detected via iiRT-PCR from serum samples. Physical analyses showed that 90% of the skin was affected by severe alopecia due to the sarcoptic mange infection. The presence of mites and histopathological analyses confirmed the diagnosis of infection. This coati was taken to a veterinary clinic and was fed every day, but it died after four days. This is the first report of sarcoptic mange and the first report of CDV in white-nosed coatis in South America. Further studies are needed in this region, to seek out other suspected cases, given the high capacity for disease transmission. Preventive actions to avoid epidemic and zoonotic episodes are needed.

A number of glaciological observations on debris-covered glaciers around the globe have shown a delayed length and mass adjustment in relation to climate variability, a behavior normally attributed to the ice insulation effect of thick debris layers. Dynamic interactions between debris cover, geometry and surface topography of debris-covered glaciers can nevertheless govern glacier velocities and mass changes over time, with many glaciers exhibiting high thinning rates in spite of thick debris cover. Such interactions are progressively being incorporated into glacier evolution research. In this paper we reconstruct changes in debris-covered area, surface velocities and surface features of three glaciers in the Patagonian Andes over the 1958–2020 period, based on satellite and aerial imagery and Digital Elevation Models. Our results show that debris cover has increased from 40 ± 0.6 to 50 ± 6.7% of the total glacier area since 1958, whilst glacier slope has slightly decreased. The gently sloping tongues have allowed surface flow velocities to remain relatively low (

Based on the recently released National Glacier Inventory (NGI), we analyzed the characteristics and the mass balance rates of ice masses in the Argentinean Central Andes (ca. 30°–37° S). The NGI provides unprecedented information on area, number and distribution of different ice masses, including debris-covered glaciers and rock glaciers. In the Central Andes, a number of 8,076 ice masses were identified covering a total area of 1767 km2. For the period 2000–2018, a general lowering of the ice surface was observed with a region-wide mass balance rate of −0.18 ± 0.19 m w.e. yr−1. Clear differences depending on the debris coverage of the different ice masses were identified, with mass balance rates ranging from −0.36 ± 0.19 m w.e. yr−1 for partly debris-covered glaciers to −0.02 ± 0.19 m w.e. yr−1 for rock glaciers. Considering different sub-periods, the region-wide mass balance rate was slightly positive (+0.12 ± 0.23 m w. e. yr−1) from 2000 to 2009 and negative (−0.21 ± 0.30 m w.e. yr−1) from 2009 to 2018. A comparison with the Randolph Glacier Inventory (RGI version 6.0) indicates that the NGI provides more detailed information regarding different type of ice masses whereas region-wide mass balance rates show limited sensitivity to the choice of the inventory. The inclusion of rock glaciers and “debris-covered ice with rock glacier” in the NGI causes mass balance rates to be slightly less negative than when using the RGI. Since the Central Andes are experiencing an unprecedented decade-long drought, our study provides crucial information to estimate current and future hydrological contribution of the different type of ice masses to river discharge in the arid subtropical Andes.

Las guías de campo para avistamientos de cetáceos son herramientas didácticas que ayudan a cumplir con los objetivos de las actividades ecoturísticas favoreciendo la preparación de los guías turísticos. En este trabajo se examina la importancia del ecoturismo de delfines y se presenta un método para ajustar las guías de campo a las características locales, en este caso, las de Puerto El Morro (Ecuador). Proporcionando a los guías información que fomente la valoración y conservación de los bufeos o delfines nariz de botellaTursiops truncatus, se potencia el conocimiento en el enlace principal entre el público y los delfines; es decir, los guías de las actividades de avistamiento de delfines. Se utilizaron cuestionarios realizados a usuarios para determinar los atractivos de mayor interés del Refugio de Vida Silvestre Manglares del Morro en el turista y se evaluó la fortaleza de la guianza en las temáticas ecológicas relacionadas. El 76% de los usuarios de las operadoras encuestados (N=22) percibieron al delfín como atractivo turístico principal, sobre las aves y el ecosistema de manglar. Estos elementos eran cubiertos de forma poco desarrollada durante la guianza por lo que se justificó incluirlos estratégicamente en la guía de campo para el avistamiento de delfines.

The Andes is the most biodiverse region across the globe. In addition, some of the largest urban areas in South America are located within this region. Therefore, ecosystems and human population are affected by hydroclimate changes reported at global, regional and local scales. This paper summarizes progress of knowledge about long-term trends observed during the last two millennia over the entire Andes, with more detail for the period since the second half of the 20th century, and presents a synthesis of climate change projections by the end of the 21st century. In particular, this paper focuses on temperature, precipitation and surface runoff in the Andes. Changes in the Andean cryosphere are not included here since this particular topic is discussed in other paper in this Frontiers special issue, and elsewhere (e.g. IPCC,2019b). While previous works have reviewed the hydroclimate of South America and particular sectors (i.e., Amazon and La Plata basins, the Altiplano, Northern South America, etc.) this review includes for the first time the entire Andes region, considering all latitudinal ranges: tropical (North of 27°S), subtropical (27°S−37°S) and extratropical (South of 37°S). This paper provides a comprehensive view of past and recent changes, as well as available climate change projections, over the entire Andean range. From this review, the main knowledge gaps are highlighted and urgent research necessities in order to provide more mechanistic understanding of hydroclimate changes in the Andes and more confident projections of its possible changes in association with global climate change.

Despite their extensive use, the absolute dating of tree-ring chronologies has not hitherto been independently validated at the global scale. Here, the identification of distinct 14C excursions in 484 individual tree rings, enable the authors to confirm the dating of 44 dendrochronologies from five continents.

A full understanding of glacier changes in the Patagonian Andes over decadal to century time-scales is presently limited by a lack of detailed and appropriate long-term observations. Here, we present geodetic mass and area changes of three valley glaciers from Monte San Lorenzo derived from stereo aerial photos, the Shuttle Radar Topography Mission (SRTM) and satellite imagery (SPOT5 and Pleiades) spanning four periods from 1958 to 2018. Our results indicate that net mass balance was negative throughout the six decades, with a mean mass loss of −1.35 ± 0.08 m w.e. a–1 and a total glacier area loss of 14.2 ± 0.7 km2 (23 ± 1% or 0.40 ± 0.02% a–1). The period 1981–2000 had the most negative mass budget, with an area-averaged mass loss of 1.67 ± 0.11 m w.e. a–1 and a maximum loss of −2.23 ± 0.07 m w.e. a–1 at San Lorenzo Sur glacier. Over the periods of 2000–2012 and 2012–2018, the mass budget of these three glaciers remained virtually unchanged at −1.37 ± 0.06 and −1.36 ± 0.17 m w.e. a–1, respectively. To place these results into a broader geographical context, the mass balance of a further 15 glaciers from around the Monte San Lorenzo massif was determined from 2000 onwards. This wider analysis reveals a period of reduced mass loss of −0.13 ± 0.21 m w.e. a–1 from 2012 to 2018 after a period of enhanced mass loss of −0.31 ± 0.16 m w.e. a–1 between 2000 and 2012. We find that increasing air temperatures coupled with diminishing precipitation across the region explains the observed patterns and are the main drivers of the negative mass budget. Furthermore, increased calving and melting into recently formed proglacial lakes has further enhanced mass loss at some lake-terminating glaciers.

Para la ecología política del cambio climático, los eventos naturales tienen una materialidad contundente pero interactúan con configuraciones económicas, políticas, sociales y territoriales específicas que los condicionan. Este enfoque es aplicado al análisis de la vulnerabilidad rural al cambio climático en Mendoza. El enfoque se distancia de los estudios que focalizan en la adaptación y, en cambio, identifica los condicionantes estructurales de la vulnerabilidad en el área de estudio: gestión fragmentada del agua y el suelo; rentabilidad negativa persistente; condiciones de mercantilización y predominancia del paradigma de la eficiencia hídrica y productiva. A partir de un análisis principalmente cualitativo, el trabajo remite la explicación de las causas de la vulnerabilidad a la preponderancia de un modelo de desarrollo orientado a la productividad para el mercado global que va expulsando a los que no son capaces de adoptarlo.

Extreme climatic events, such as late frosts in spring during leaf flush, have considerable impacts on the radial growth of temperate broadleaf trees. Albeit, all broadleaved species are potentially vulnerable, damage depends on the particularities of the local climate, the species, and its phenology. The impact of late spring frosts has been widely investigated in the Northern Hemisphere, but the potential incidence in Southern Hemisphere tree species is still poorly known. Here, we reconstruct spring frost occurrence at 30 stands of the deciduous tree Nothofagus pumilio in its northern range of distribution in the Patagonian Andes. We identified tree ring-width reductions at stand level not associated with regional or local drought events, matching unusual minimum spring temperatures during leaf unfolding. Several spring frosts were identified along the northern distribution of N. pumilio, being more frequent in the more continental Argentinean forests. Spring frost in 1980 had the largest spatial extent. The spring frosts in 1980 and 1992 also induced damages in regional orchards. Spring frost damage was associated with (i) a period of unusually warm temperatures at the beginning of leaf unfolding, followed by (ii) freezing temperatures. This study helps expand our understanding of the climatic constraints that could determine the future growth and dynamics of Andean deciduous forests and the potential use of tree-rings as archives of extreme events of spring frosts in northern Patagonia.

Recent studies documenting climate variability in South America have provided valuable information for understanding current and past dynamics of the climate system. Long meteorological records represent an essential tool to properly characterize climate fluctuations from decadal to multi-decadal scales. Unfortunately, the scarcity of continuous and homogeneous instrumental records is a major constraint to determine long-term variations in South America. Our knowledge of the forcings modulating the hydrological variability in mountains is still limited, despite their importance as freshwater sources for people living in the adjacent piedmonts and lowlands. The objective of this work is to determine the spatial–temporal variability of precipitation in the humid subtropical Andes and the Chaco region in North Western Argentina (NWA). Thirty-four rainfall records covering the common period 1934–1990, partially updated to 2016, were used to extend and identify the dominant patterns of seasonal to annual hydroclimatic variability based on principal components analysis. Intensity and frequency of droughts and pluvials (95th percentiles, respectively) were determined for the dominant patterns of variability. Our results show a positive trend in precipitation since 1970s in all temporal patterns and sub-regions. In addition, precipitation variability (both positive and negative extremes) increases during these last decades. Correlation analysis with sea-surface temperatures and wind anomalies during summer, reveal Amazon moisture sources and large-scale oceanic controls on NWA precipitation. The extended precipitation series shows that the frequency of pluvials has increased since the 1970s interrupted by few extreme droughts. This record can be considered representative of precipitation variations across NWA, including different environments in the Chaco, sub-Andes, and Puna.

The prominent Andes cordillera induces significant differences in climates between its eastern and western slopes. These climatic differences are largely reflected by contrasting vegetation and ice coverages but remain poorly documented. This study quantifies the abrupt changes of precipitation and cloud properties at both sides of the Andes south of 20°S by using surface daily precipitation and satellite (CloudSat and MODIS) data during the 2006–2016 period. Results show that the precipitation changes drastically and precipitating clouds can be of very different nature on each side of the Andes. In the tropical Andes (20–25°S), precipitation normally falls from a sole layer of thick stratiform and convective precipitating clouds during the warm semester, but the annual mean accumulation is about 10–100 times larger on the eastern than on the western slopes. A sole layer of low stratus clouds dominates over the Pacific coast, occasionally producing light rains, whereas high, thin, and non-precipitating clouds dominate most of the time over the continent. In the subtropical Andes (25–35°S), annual mean precipitation is similar on both sides, however, it falls from convective and stratiform precipitating clouds in the warm semester on the eastern slopes, and from stratiform precipitating clouds in the cold semester, mostly as frozen particles, on the western slopes. These different features on both slopes denote a climatic transition between the tropics and extratropics. In the extratropical Andes (south of 35°S), stratiform cloud types produces precipitation on both sides during all the year, but the annual mean precipitation and cloud frequency are enhanced on the western slopes and strongly reduced on the eastern slopes of the Andes. Cloud frequencies are higher than in the subtropics and evenly distributed as single- or multi-layers of low, middle and high clouds. Frozen particles become important in precipitating clouds over the mountains and on the lee side. These findings demonstrate the significant influence of the Andes cordillera on the climate all along southwestern South America, and constitute an excellent example of how the simple dependence of climate on latitude can be substantially altered by the topography.

Tree mortality is a key driver of forest dynamics and its occurrence is projected to increase in the future due to climate change. Despite recent advances in our understanding of the physiological mechanisms leading to death, we still lack robust indicators of mortality risk that could be applied at the individual tree scale. Here, we build on a previous contribution exploring the differences in growth level between trees that died and survived a given mortality event to assess whether changes in temporal autocorrelation, variance, and synchrony in time-series of annual radial growth data can be used as early warning signals of mortality risk. Taking advantage of a unique global ring-width database of 3065 dead trees and 4389 living trees growing together at 198 sites (belonging to 36 gymnosperm and angiosperm species), we analyzed temporal changes in autocorrelation, variance, and synchrony before tree death (diachronic analysis), and also compared these metrics between trees that died and trees that survived a given mortality event (synchronic analysis). Changes in autocorrelation were a poor indicator of mortality risk. However, we found a gradual increase in inter-annual growth variability and a decrease in growth synchrony in the last ∼20 years before mortality of gymnosperms, irrespective of the cause of mortality. These changes could be associated with drought-induced alterations in carbon economy and allocation patterns. In angiosperms, we did not find any consistent changes in any metric. Such lack of any signal might be explained by the relatively high capacity of angiosperms to recover after a stress-induced growth decline. Our analysis provides a robust method for estimating early-warning signals of tree mortality based on annual growth data. In addition to the frequently reported decrease in growth rates, an increase in inter-annual growth variability and a decrease in growth synchrony may be powerful predictors of gymnosperm mortality risk, but not necessarily so for angiosperms.

El deshielo de la nieve acumulada durante el invierno en la cuenca alta del río Mendoza constituye el principal suministro de agua para la agricultura, la industria y el consumo humano en los sectores bajos adyacentes. Sin embargo, a pesar de su gran importancia, hay muy pocos estudios que permitan conocer y entender la variabilidad espacial y temporal de la nieve en este sector de los Andes Centrales de Argentina. En este trabajo presentamos una técnica para cuantificar la evolución diaria de la cobertura nival en esta cuenca basada en la integración de imágenes de los sensores MODIS Aqua y Terra para el período 2000 y 2014. La técnica muestra disminución en la pérdida de información por presencia de nubosidad y fue realizada utilizando herramientas y funciones de los lenguajes de programación Libres R y BASH. Las series de cobertura de nieve obtenidas muestran importantes variaciones estacionales con aumentos de la cobertura nival en invierno (58% de cobertura máxima en promedio) y reducciones significativas en verano. Asimismo, se observa una importante variabilidad interanual con claras diferencias entre años secos (ej. 2010, con 12% de cobertura promedio) y nevadores (ej. 2005, 32% de cobertura anual promedio). Los mapas de cobertura nival muestran además que los sectores con mayor persistencia de nieve coinciden con la ubicación de glaciares, en los sectores más elevados, protegidos y de menor insolación de la cuenca. Los resultados brindan información novedosa y relevante para conocer y entender de forma más completa la distribución y variabilidad de la cobertura nival en este sector de la cordillera. Los mismos pueden servir de base para múltiples aplicaciones incluyendo el modelado hidrológico de la cuenca del río Mendoza contribuyendo al manejo racional de sus recursos hídricos.

In this paper we explore how changes in human strategies are differentially modulated by climate in a border area between hunter-gatherers and farmers. We analyze multiple proxies: radiocarbon summed probability distributions (SPDs), stable C and N isotopes, and zooarchaeological data from northwestern Patagonia. Based on these proxies, we discuss aspects of human population, subsistence, and dietary dynamics in relation to long-term climatic trends marked by variation in the Southern Annular Mode (SAM). Our results indicate that the farming frontier in northwestern Patagonia was dynamic in both time and space. We show how changes in temperature and precipitation over the last 1000 years cal BP have influenced the use of domestic plants and the hunting of highest-ranked wild animals, whereas no significant changes in human population size occurred. During the SAM positive phase between 900 and 550 years cal BP, warmer and drier summers are associated with an increase in C4 resource consumption (maize). After 550 years cal BP, when the SAM changes to the negative phase, wetter and cooler summer conditions are related to a change in diet focused on wild resources, especially meat. Over the past 1000 years, there was a non-significant change in the population based on the SPD.

The upper treeline provides a unique opportunity for documenting changes in forest dynamics in the context of current environmental fluctuations. Documenting the response of forests to present environmental changes will be very useful in developing and validating vegetation models that predict plant responses to global changes resulting from human activities. It is generally suggested that the expansion of the upper treeline is limited by cold temperatures, so warmer conditions are expected to induce an advance of forests into alpine vegetation. Significant changes in temperature and precipitation have already been documented in regional studies along the Patagonian Andes during the last decades. Across Patagonia, there are strong relationships between changes in climate and variations in the Southern Annular Mode (SAM). The atmospheric circulation indexes, act as climate packages summarizing climatic information since they combine changes in environmental variables. In order to complement previous studies in the northern Patagonia treeline, we have conducted a this study in the southern Patagonian Andes to: (1) characterize the patterns of Nothofagus pumilio establishment in the upper treeline along a precipitation gradient, (2) to establish the relationship between variations in regional climate and tree establishment and (3) to determine the influence of continental and hemispheric-scale climatic forcing on tree establishment at regional scale. Our studies suggest that the location of the upper treeline of the N. pumilio forest in the Patagonian Andes is sensitive to changes in climate variations. The temperature increment has facilitated the tree recruitment, however, the rate of seedling establishment appears to be more strongly modulated by the interaction between temperature increase and variations in precipitation. The expansion of the upper treeline has been limited to 5–10m from the abrupt treeline. This comparatively reduced advance of the forest in the alpine grassland is regulated by other biotic and abiotic factors rather than the temperature increase. While the recent expansion of the upper treeline in northern Patagonia was regulated by temperature and precipitation variations associated with the different phases of the Pacific Decadal Oscillation, the establishment above the upper treeline in the southern Patagonian Andes was facilitated by climatic variations induced by the positive trend of the SAM during the last decades.

The original version of this Article contained an error in the Data Availability section, which incorrectly read ‘All data will be freely available via https://www.ams.ethz.ch/research.html.’ The correct version states ‘http://www.ams.ethz.ch/research/published-data.html’ in place of ‘https://www.ams.ethz.ch/research.html’. This has been corrected in both the PDF and HTML versions of the Article.

Abstract Understanding the influence of climatic variations on forest decline is a major challenge for scientists investigating global changes. Although reductions in tree growth have previously been associated with forest decline, comprehensive efforts to understand these relationships are rare. Based on ring‐width variations, we determine the influence of climatic fluctuations on the onset and temporal evolution of Nothofagus pumilio forest decline in the Patagonian Andes. Basal area increment (BAI) data from 294 Nothofagus trees at 11 stands in a 500‐km latitudinal transect along the forest–steppe ecotone were used to identify the dominant patterns of regional growth. Three Regional dominant patterns, showing common variations in BAI, were derived. Two BAI patterns show high rates of growth from early to mid‐20th century, followed by sustained negative trends over the last 3–6 decades, whereas the third pattern is characterized by a positive trend since the 1960s. Tipping points in growth trends of the first two patterns are associated with two extreme dry–warm climate events in spring–summer of 1942–1943/1943–1944/1944–1945 and 1978–1979. Both severe droughts were preceded by up to 10 yr of wet periods that promoted above‐average tree growth. We concluded that severe droughts occurring after wet periods trigger the decline of large, dominant N. pumilio trees with high rates of growth. The coincidence between major changes in regional growth with two of the most severe droughts in the instrumental records shows that climatic variations over northern Patagonia synchronize the beginning of forest decline at a regional scale. As these dry–mesic N. pumilio sites will face more severe droughts in the 21st century, as suggested by future climate scenarios, the areas affected by forest decline would increase substantially.

Las avalanchas de nieve representan un importante riesgo natural en diversas regiones montañosas alrededor del mundo. Daños a infraestructura y pérdidas de vidas humanas son reportados frecuentemente en relación a eventos catastróficos de avalanchas. En los Andes, numerosas obras de infraestructura se ubican en zonas vecinas a senderos de avalanchas, de las que poco se conoce sobre sus alcances máximos, periodos de retorno y presiones de impacto. A través de la implementación de técnicas dendrocronológicas hemos reconstruido las fechas de ocurrencia y áreas de influencia de eventos pasados de avalanchas de nieve. Ejemplares de Nothofagus pumilio con perturbaciones visibles de avalanchas fueron muestreados en sectores del canal, bordes y zonas de frenado de 11 senderos de avalanchas ubicados en Loma de las Pizarras, próximo a El Chaltén, Santa Cruz, Argentina. Además, áreas de control fueron muestreadas para determinar las condiciones de crecimiento en árboles no afectados por avalanchas. Nuestros análisis indican que las cicatrices, las variaciones de excentricidad en el leño, los cambios abruptos de crecimiento y la presencia de leño de tensión son los principales indicadores dendrocronológicos en N. pumilio asociados a la ocurrencia de avalanchas. Basados en una ponderación cuantitativa de los indicadores y en la profundidad de muestreo, calculamos un índice de ocurrencia de eventos, el cual nos permitió determinar para cada sendero los años con ocurrencia de avalanchas. Considerando de manera integral la actividad de avalanchas en los 11 senderos muestreados, los años con mayor ocurrencia de eventos fueron 1936, 1966, 1978 y 1995. Complementariamente, registros climáticos fueron analizados con el objetivo de determinar las relaciones entre los años con ocurrencia de avalanchas y las variaciones mensuales de precipitación y temperatura. Se observa que los años con gran frecuencia de avalanchas están significativamente correlacionados con la ocurrencia de abundantes precipitaciones invernales; no se detectaron relaciones significativas con las variaciones de temperatura. Los resultados alcanzados en esta investigación prueban el potencial dendrocronológico de N. pumilio para reconstruir patrones espaciales y temporales de avalanchas de nieve en los Andes patagónicos.

El objetivo de este trabajo fue evaluar las relaciones entre las variaciones en el clima y en la concentración de C0(2) durante el siglo XX con el crecimiento radial y la eficiencia en el uso del agua en los bosques de Nothofagus pumilio a lo largo de un gradiente altitudinal, en El Chaltén (49°22' S), Santa Cruz, Argentina. Se empleó una combinación de técnicas dendrocronológicas e isotópicas. Los patrones de crecimiento radial a lo largo del gradiente altitudinal reflejan las tendencias climáticas registradas en la zona durante el siglo XX. El crecimiento de los árboles ubicados en el límite superior muestra una tendencia positiva en respuesta al incremento regional de las temperaturas. Por el contrario, los bosques en contacto con la estepa patagónica presentan, en respuesta a una intensificación del déficit hídrico, una tendencia negativa de crecimiento durante el siglo pasado. Los árboles creciendo en bosques mésicos ubicados en alturas intermedias muestran una tendencia levemente negativa no significativa. Los valores de 6(13)C reflejan en qué medida el contenido de humedad en el suelo regula en forma diferencial los procesos de conductancia estomática y tasa fotosintética a lo largo del gradiente altitudinal. En sitios donde el déficit hídrico varía desde leve a muy marcado, la eficiencia intrínseca en el uso del agua (EIUA) parece estar influenciada por la disponibilidad de agua en el suelo. La relación entre la EIUA y las variables climáticas es más clara en sitios con reducido estrés hídrico. En sitios secos, el estrés hídrico muy marcado reduciría la tasa fotosintética en grado tal que el crecimiento no podría ser compensado por el aumento en EIUA. En contraste con el concepto tradicional en dendrocronología que postula una relación más estrecha entre el crecimiento radial y las variaciones climáticas en los bosques ecotonales, los valores isotópicos de 6(13)C representan más claramente las variaciones de la disponibilidad hídrica en sitios mésicos.Influences of climate and C0(2) concentration variations during the last century on radial growth and water-use efficiency oí Nothofagus pumilio were evaluated along an altitudinal gradient in El Chaltén (49°22' S), Santa Cruz, Argentina. We used a combination of dendrochronological and isotopic techniques. Tree growth in the upper treeline shows a positive trend concurrent with increasing regional temperatures. In contrast, due to a gradual increase in water déficits, the rate of radial growth in the xeric forest-steppe ecotone has decreased in the past 100 years. Intermediate-elevation trees from mesic forests show a weak, non-significant negative trend in radial growth during the same interval. 6(13)C reflects soil moisture variations with elevation and its differential influence on stomatal conductance and photosynthetic rate processes. In sites with reduced to severe water déficits, the intrinsic water-use efficiency (IWUE) appears to be influenced by the amount of water in the soil. However, the relationship between IWUE and climate is more obvious in sites with reduced water stress. In drier sites, the photosynthetic rate is severely limited by water déficits so that the reduction in radial growth is not compensated by the increase in IWUE. In contrast with the traditional assumption in dendrochronology indicating that the strong relationships between radial growth and climate are recorded at the forest ecotones, the variations in 6(13)C better reflect water déficits at intermedíate mesic forests.

La liquenometría es una técnica de datación que estima la edad de exposición de una superficie a partir del diámetro de los líquenes que crecen en ella. El objetivo de este estudio es calibrar la curva de crecimiento de Rhizocarpon subgénero Rhizocarpon en los Andes Patagónicos, y aplicarla para reconstruir las fluctuaciones glaciares durante los últimos siglos. Para ello se investigaron seis glaciares, tres en el norte y tres en el sur de los Andes Patagónicos, en los cuales se realizaron mediciones del diámetro de ejemplares del subgénero Rhizocarpon en sitios de edad conocida (sitios control) y sitios de edad desconocida. La edad de los sitios control se determinó fehacientemente a partir de información histórica. Los datos liquenométricos relevados en estos sitios control fueron utilizados para calibrar la curva de crecimiento. La relación entre el tamaño de los líquenes y la edad de la superficie (curva de crecimiento) es lineal, indicando que los líquenes del subgénero Rhizocarpon tienen una tasa de crecimiento constante a lo largo del tiempo. Esta curva se extiende por 270 años. Aplicación de la curva a los datos liquenométricos relevados en las morenas de edad desconocida permitió establecer la cronología de la secuencia de morenas de los seis glaciares bajo estudio. Los datos liquenométricos fueron contrastados con datos dendrocronológicos, mostrando una gran concordancia entre los métodos. Los resultados obtenidos muestran dos períodos principales de formación de morenas. El primer período se extiende desde la mitad del siglo XVII hasta finales del siglo XIX, y está caracterizado por morenas muy prominentes. El segundo período se extiende desde mediados del siglo XIX hasta finales del siglo XX, y esta caracterizado por la formación de un gran número de morenas pequeñas.

Nothofagus pumilio (Poepp. et Endl. Krasser) is a deciduous species that dominates the upper tree line of the Chilean and Argentinean Andes between 35º 36' and 55º 31' S. In this study we describe the development of 21 tree-ring width chronologies of N. pumilio across its southernmost range of distribution (51-55º S) in Chile, and analyze the relationship between N. pumilio tree-growth and climate. Ten of the tree-ring chronologies in our study, show an increasing trend and/or above average tree-ring growth since ca. 1960 to 1996, which coincides with the increase in temperatures shown by instrumental records from southern Patagonia. Another dominant pattern in tree-growth is a remarkable ca. 7-year cycle present in three of the study sites from Isla Navarino, the southernmost of our study areas (ca. 55º S). These two dominant tree-growth patterns, represent the main modes of variation of the N. pumilio tree-ring records in the southern Chilean Patagonia, accounting for 14 and 28 % of its total variance, respectively. Based on the positive correlation between tree growth and temperature in several of the study sites analyzed in this work, we developed a reconstruction of the Punta Arenas minimum annual temperatures from the seven tree-ring records with the highest correlation with temperature, covering the 1829-1996 period. The reconstruction shows that during most of the 19th century, minimum annual temperatures remained below-average and increased to values fluctuating around the mean during the 1900-1960 period, followed by a clear trend with above-average values after 1963Nothofagus pumilio (Poepp. et Endl. Krasser) es una especie caducifolia que domina el límite arbóreo superior de los Andes de Chile y Argentina entre los 35º 36' y 55º 31' S. En este trabajo describimos el desarrollo de 21 cronologías de ancho de anillos de N. pumilio para su rango más austral de distribución (51-55º S) en Chile, así como el análisis de su relación con el clima. Diez de las cronologías de ancho de anillos estudiadas muestran una tendencia al incremento y/o crecimiento sobre el promedio a partir de aproximadamente 1960 hasta 1996, lo cual coincide con un incremento sostenido en las temperaturas mostrado por los registros instrumentales de la Patagonia austral. Otra característica particular del crecimiento de los árboles es un notable ciclo de cerca de 7 años presente en tres de los sitios de estudio en la Isla Navarino, el área de estudio más austral estudiada por nosotros (55º S). Estos dos patrones de crecimiento, representan los principales modos de variación de los registros de anillos de crecimiento de N. pumilio en la Patagonia austral de Chile, y explican respectivamente el 14 y 28 % de la varianza total. Sobre la base de la correlación positiva que se verifica entre el crecimiento arbóreo y la temperatura en varios de los sitios de estudio analizados en este trabajo, reconstruimos las variaciones de las temperaturas mínimas anuales de Punta Arenas para el período 1829-1996. La reconstrucción muestra que durante la mayor parte del siglo 19 las temperaturas mínimas anuales permanecieron por debajo del promedio, aumentando a valores que fluctuaron en torno a la media durante el período 1900-1960, seguido por una clara tendencia sobre la media para el período posterior a 1963

During the period 2010–2015, the semi-arid Central Andes in Argentina (CAA) experienced one of the most severe and long-lasting hydrological droughts on record. Since the snowmelt is the most important source of water, the reduced snowfall over the mountains propagated the drought signal through the streamflows in the adjacent foothills east of the Andes ranges. Motivated by the widespread impacts on the socio-economic activities in the region, this study aims to characterize the recent hydrological drought in terms of streamflow deficits. Based on streamflow data from 20 basins, we used the standardized streamflow index (SSI) to characterize hydrological droughts during the period 1971–2016. We found that the regional extent of the 2010–2015 hydrological drought was limited to the basins located north of 38° S, with mean duration of 67 months and maximum drought severity exhibiting a heterogeneous pattern in terms of spatial distribution and time of occurrence. The drought event reached extreme conditions in 14 of the 15 basins in the CAA, being record-breaking drought in six of the basins. This condition was likely driven by a cooling in the tropical Pacific Ocean resembling La Niña conditions, which generated a decrease in snowfall over the Andes due to suppressed frontal activity.

La liquenometría es una técnica de datación que estima la edad de exposición de una superficie a partir del diámetro de los líquenes que crecen en ella. El objetivo de este estudio es calibrar la curva de crecimiento de Rhizocarpon subgénero Rhizocarpon en los Andes Patagónicos, y aplicarla para reconstruir las fluctuaciones glaciares durante los últimos siglos. Para ello se investigaron seis glaciares, tres en el norte y tres en el sur de los Andes Patagónicos, en los cuales se realizaron mediciones del diámetro de ejemplares del subgénero Rhizocarpon en sitios de edad conocida (sitios control) y sitios de edad desconocida. La edad de los sitios control se determinó fehacientemente a partir de información histórica. Los datos liquenométricos relevados en estos sitios control fueron utilizados para calibrar la curva de crecimiento. La relación entre el tamaño de los líquenes y la edad de la superficie (curva de crecimiento) es lineal, indicando que los líquenes del subgénero Rhizocarpon tienen una tasa de crecimiento constante a lo largo del tiempo. Esta curva se extiende por 270 años. Aplicación de la curva a los datos liquenométricos relevados en las morenas de edad desconocida permitió establecer la cronología de la secuencia de morenas de los seis glaciares bajo estudio. Los datos liquenométricos fueron contrastados con datos dendrocronológicos, mostrando una gran concordancia entre los métodos. Los resultados obtenidos muestran dos períodos principales de formación de morenas. El primer período se extiende desde la mitad del siglo XVII hasta finales del siglo XIX, y está caracterizado por morenas muy prominentes. El segundo período se extiende desde mediados del siglo XIX hasta finales del siglo XX, y esta caracterizado por la formación de un gran número de morenas pequeñas.

Debido a la escasez de especies con anillos anuales de crecimiento, la dendrocronología de regiones áridas de montañas tropicales y subtropicales está muy poco desarrollada. En este trabajo evaluamos el potencial de la especie arbórea Prosopis ferox,"churqui", para estudios dendrocronológicos analizando las características anatómicas del leño y las relaciones entre registros climáticos y cronologías de ancho de anillos de una colección realizada a 3.500 m, en la quebrada de Humahuaca (23°13' S, 65°20' O), Provincia de Jujuy, Argentina. Las observaciones microscópicas de cortes histológicos muestran que los anillos están claramente demarcados por una banda parenquimática terminal clara. Comparando la cronología estandarizada de ancho de anillos con los registros instrumentales de La Quiaca (22º06'S, 65º36'O), se observan correlaciones significativas con precipitaciones por encima de la media y temperaturas por debajo de la media durante los meses de verano (diciembre_marzo). Esto se interpreta como una relación positiva con la disponibilidad de agua en el suelo durante el período de crecimiento. Esta cronología representa no solamente el primer registro dendrocronológico desarrollado a partir de P. ferox, sino también la primera cronología de anillos de árboles en la provincia biogeográfica Prepuneña. La buena discriminación de los anillos anuales de crecimiento, la fuerte relación con variables climáticas, el amplio rango de distribución de la especie en el noroeste de Argentina y sur de Bolivia (20° a 25° S) y la longevidad observada en individuos aislados (c. 500 años), hacen de P. ferox una especie muy promisoria para estudios dendroclimatológicos y dendroecológicos en desiertos subtropicales de alta montañaDue to the scarcity of species with annual tree rings, the use of dendrochronological techniques has received little attention in tropical and subtropical montane dry areas. In this study, we assess the dendrochronological potential of Prosopis ferox, "churqui", through the analysis of its wood anatomy and the relationships between climate and tree growth variations from trees collected at 3,500 m, in the Humahuaca valley (23°13' S, 62°20' W), Jujuy province, Argentina. Microscopic observations show that annual rings are clearly defined by a relatively lighter parenchyma belt formed at the end of the annual band. Comparisons between the standardized ring-width chronology and the instrumental records from La Quiaca (22º 06'S, 65º36'W) indicated that above-average rainfall and below-average temperature during summer (i.e., December to March) favor tree growth. This can be interpreted as a positive relationship between radial growth and abundant soil water content during the growing season. The chronology shown here represents not only the first dendrocronological record from P. ferox, but also the first tree-ring chronology for the Prepuna biogeographic province. The well-defined annual rings, the strong relationship between growth and climatic variables, the large range of distribution across northwestern Argentina and southern Bolivia (20° to 25° S), and the longevity observed in some individuals (c. 500 years), indicate that P. ferox is a very promising species for dendroclimatological and dendroecological studies in subtropical montane ecosystems