Semiarid Chile Research Articles

Adaptive plasticity to drought of Grime's CSR strategies

Grime's strategies (competitor, stress tolerator, ruderal; CSR) represent viable trait combinations with which species deal with environmental conditions. CSR strategies are broadly used to understand plant adaptation to the environment, yet their plastic responses have received little attention. A globally‐calibrated tool (StrateFy) estimates CSR strategies using specific leaf area (SLA), leaf dry matter content (LDMC) and leaf area (LA) data, but these three traits can hardly characterise whole‐plant responses to the environment individually. CSR strategies reflect tradeoffs among growth, survival and reproduction, at both leaf and whole‐plant levels, thus integrating several functions. We hypothesised that CSR strategies and the three constituent traits would show independent plasticity patterns, and that CSR strategies would be more likely to show adaptive responses, i.e. to fit expected functional responses to environmental gradients. We compared phenotypic plasticity to drought in single traits (SLA, LDMC and LA) with the integrated plasticity of the resulting CSR strategy. The study species was the invasive plant Mesembryanthemum crystallinum, which is distributed in arid and semiarid Chile. We found that trait plasticity was rather idiosyncratic and contrary to what would be expected from a functional adjustment to drought: LDMC did not change (expected response: increase) and SLA increased (expected response: decrease). Conversely, plastic responses of CSR strategy and LA were consistent with functionally adaptive responses to drought in all populations: S‐strategy increased, while C‐strategy and LA decreased. We advocate the use of Grime's CSR theory as an integrative approach to further our understanding of adaptive plasticity in plants.

Variable interspecific competition under megadrought conditions: rodent population dynamics in semiarid Chile

Deciphering how climatic variability modulates the interspecific interactions in natural systems is one of the most interesting and least studied ecological processes. Rodent outbreaks or irruptions in semiarid Chile are associated with rainfall pulses driven by the El Niño Southern Oscillation (ENSO). During the last decade, north‐central Chile has experienced an almost uninterrupted sequence of > 10 dry years, the so‐called megadrought, which had led to a new ecological benchmark in this region. We employ a diagnostic approach to analyze abundance data regarding two rodent species, Phyllotis darwini and Abrothrix olivacea, using a 33 year time series spanning from 1987 to 2019. Our population dynamic models provide evidence of competitive interactions within and between both species. This result is novel because we show that rainfall variability influences the degree of interspecific competition and that it is asymmetric. The diagnostic approach used here offers a way to develop simple population models that are useful for understanding the causes of population fluctuations and for predicting population changes under a climate change scenario.

Complicating the tale of ‘first climate migrants’: Resource-dependent livelihoods, drought and labour mobilities in semi-arid Chile

While stories of ‘climate migrants’ regularly make the news, local perspectives often paint a different picture of migration motivations. Based on the case of ‘Chile’s first climate migrants’ from Monte Patria, an increasingly drought-affected rural municipality characterised by its agricultural economy, this article argues that mobilities under climate change need to be understood through a power-sensitive approach analysing both local perceptions of environmental changes and power relations extending beyond the case-study level. Through the combination of the environmental mobilities approach with a political ecology of climate change, this article studies how (a) precipitation deficits are translated into locally perceivable effects through the Chilean water distribution system, (b) how these effects impact different socio-economic groups differentially, and (c) what options – including (labour) mobilities – locals perceive to have for responding. Ethnographic fieldwork in Monte Patria, including 39 semi-structured interviews and 11 follow-alongs, has shown that uneven resource access, limited political bargaining power and the perceived impossibility to earn a sufficient income in the agricultural economy are locally considered as more important reasons for engaging in mobilities than considerations about climate change (adaptation). As prolonged droughts aggravate the existing structural economic insecurity of local livelihoods, creating a situation under which staying is considered increasingly difficult, the participation in pre-established labour mobility patterns directed outside of the municipality is considered as normal and potentially positive household-level response. The article concludes that these insights can serve to guide climate change adaptation policy-making that is attuned to existing mobility patterns and the importance of resource redistribution.

Contrasting geophysical signatures of a relict and an intact Andean rock glacier

Abstract. In semi-arid Chile, rock glaciers cover more surface area than glaciers and are potentially important water reserves. To understand their current and future hydrological role, it is necessary to characterize their internal structure (e.g. internal boundaries and ice, air, water and rock content). In this study, we present the results and interpretations of profiles of electrical resistivity and refraction seismic tomography collected on two contrasting rock glaciers in the Chilean Andes located at the headwaters of the Elqui River within the Estero Derecho nature reserve. These geophysical measurements are interpreted both independently and jointly through a scheme of petrophysical four-phase inversion. These first in situ measurements in Estero Derecho confirm that El Ternero (intact rock glacier) contains a significant volume of ground ice, while El Jote contains little to no ice (relict rock glacier). Within our study, we highlight the strong differences in the geophysical responses between intact and relict rock glaciers and propose a diagnostic model that differentiates between them.

Improving the underground structural characterization and hydrological functioning of an Andean peatland using geoelectrics and water stable isotopes in semi-arid Chile

High altitude, Andean wetlands, or bofedales as they are locally known, are important regulators of the local water balance and also play a key role in sustaining biodiversity. Nevertheless, there is almost no information regarding their hydrogeological structure and functioning. This paper aims to characterize the thickness of the alluvial filling of one peat-accumulating wetland in North-Central Chile using Electrical Resistivity Tomography (ERT) to assess its role as a water reservoir. To develop a quasi-3D understanding of the peatland’s structure, four ERT profiles were conducted. Results highlight a conductive basin shape of the peatland, with a thicker interface downstream than upstream between alluvial materials and the underlying bedrock or rock screes. Those results allow the estimate of the water column (1000–3400 mm) within the peatland alluvial filling. The second objective is to better understand the water exchanges between the peatland and the streamflow using discharge measurements and water stable isotopes. Water and isotopes budgets highlight a streamflow loss towards the peatland groundwater reservoir at the end of spring season. In addition, ten δ18O and δ2H surveys were used to characterize the distinct wetland water sources and their temporal variations. A peatland conceptual model is proposed to connect groundwater, rock glaciers, snowmelt, and hillslope flows. Andean peatlands provide a pivotal control on water delivery downstream, and therefore, understanding their structure and function is important, because they are unique structures providing ecological services at high elevations.

Tafonomía lítica del sitio Quebrada de Quereo

This paper aims to develop an analytical proposal for dealing with ambiguity in lithic material of late Pleistocene contexts in alluvial locations. We focus our study on the Quebrada de Quereo site (13480-13070 cal BP) located in the coast of Northern Semiarid Chile. To build a comparative analog, different combinations of taphonomic and technological variables are explored in an assemblage of natural origin from a nearby ravine that mimics lithic knapping attributes. This same set of variables was tested on the anthropogenic lithic assemblage of the Quebrada Santa Julia site (12990-12730 cal BP). This procedure allowed us developing an analytic system centered on the characteristics of chipped edges to weigh taphonomic and technological attributes and their natural production in torrential ravine contexts. By applying this scheme to a sample of the lithic material of Quebrada de Quereo, we discuss which pieces are most likely to be considered as lithic artifacts. We conclude that most of the Quebrada de Quereo lithic assemblage may be explained as produced by natural causes, thus those pieces should be considered pseudo-artifacts.

Characterizing the Water Storage Capacity and Hydrological Role of Mountain Peatlands in the Arid Andes of North-Central Chile

High-altitude peatlands in the Andes, i.e., bofedales, play an essential role in alpine ecosystems, regulating the local water balance and supporting biodiversity. This is particularly true in semiarid Chile, where bofedales develop near the altitudinal and hydrological limits of plant life. The subterranean geometry and stratigraphy of one peatland was characterized in north-central Chile using Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR) and core extraction. Two sounding locations, two transversal and one longitudinal profile allowed a 3D interpretation of the bofedal’s internal structure. A conceptual model of the current bofedal system is proposed. Geophysical results combined with porosity measurements were used to estimate the bofedal water storage capacity. Using hydrological data at the watershed scale, implications regarding the hydrological role of bofedales in the semiarid Andes were then briefly assessed. At the catchment scale, bofedal water storage capacity, evapotranspiration losses and annual streamflow are on the same order of magnitude. High-altitude peatlands are therefore storing a significant amount of water and their impact on basin hydrology should be investigated further.

Groundwater level trends and recharge event characterization using historical observed data in semi-arid Chile

ABSTRACTGroundwater is an important resource in semi-arid Chile to meet local social, economic and environmental water demands. Historical ground water level (GWL) data (1986–2014) in the Coquimbo Region were analysed to characterize short and long-term alluvial aquifer dynamics. Long-term trends were assessed using a seasonal Mann-Kendall trend test, which indicated that more than 80% of the time series exhibit a negative trend. Short-term analysis using cross-correlation provided information on recharge origin and its spatial pattern. Runoff and GWL are highly correlated depending on elevation, signifying that stream to aquifer flow is an important recharge process at higher altitudes. Long-term recharge behaviour was characterized using time-frequency wavelet power spectra. The results show significant amplitude of the 5-year recharge period for GWL, which is driven by a 5-year El Niño index periodicity. Such results provide key information of the spatiotemporal functioning of aquifers.

Shrubs mediate forest start-up and patch dynamics in a semiarid landscape

Plant spatial patterns in semiarid environments are often driven by a patchy availability of resources. We examined here drivers of forest patterns in a landscape where tree and shrub patches coexist in an herbaceous matrix on fog-inundated coastal hilltops in semiarid Chile, aiming to identify factors that set off forest patch formation and development. We hypothesized that a successional process driven by plant-plant interactions would start when tree seedlings establish in shrub patches, eventually leading to resource accumulation and increased diversity. Within shrub patches, soil moisture increased with increasing cover of a common shrub, Baccharis vernalis, unlike another shrub species, Griselinia scandens. Soil nutrients increased with patch size, but soil moisture remained similar among patches. Forest patches showed differences regarding soil moisture between wet windward and dry leeward edges, and these were associated with differences in community composition. While Baccharis patches were similar to windward forest edges, leeward edges were more similar to open areas. Patterns of species richness and diversity showed a shift in plant-plant interactions from positive to negative along successional transition from Baccharis to forest patches. Outside forest patches, tree species are rare but become established and survive under Baccharis vernalis, most likely thanks to a combination of fog-interception capacity, soil nutrient availability and low competition. Therefore, forest patch formation is strongly dependent on fog water interception and community composition. While some shrubs like Baccharis vernalis facilitate tree establishment and eventually initiate new forest patches, others compete with tree seedlings preventing establishment. Hence, a facilitation-competition balance between shrubs and trees explains the spatial arrangement of the forest-shrub patch mosaic in this semiarid environment.

Exclusion of small mammals and lagomorphs invasion interact with human-trampling to drive changes in topsoil microbial community structure and function in semiarid Chile

Species losses and additions can disrupt the relationship between resident species and the structure and functioning of ecosystems. Persistent human-trampling, on the other hand, can have similar effects through the disruption of biocrusts on surface soils of semiarid systems, affecting soil stability and fixation of carbon and nitrogen. Here, we tested the interactive and synergistic impacts of the exclusion of native mammalian herbivores and the effects of introduced lagomorphs in a semiarid thorn scrub ecosystem, where soils were subjected to two different trampling intensities (i.e., trampled and non-trampled). We postulated that because of their differential habitat use and fossorial activities, with respect to native small mammals, lagomorphs would have strong negative effects on soil structure, biocrust cover, and biocrust bacterial community structure. Our expectations were that changes in biocrust cover in response to trampling where native mammals were excluded, but exotic lagomorphs were present, will spread their impacts on soil chemical and physical features. To test our hypotheses, we measured changes in soil biogeochemical properties in four experimental plots where lagomorphs (L)/small mammals (SM) were experimentally manipulated to exclude them from the plots (−), or let them be present (+). The experimental combinations monitored were: -L/+SM, -L/-SM, +L/+SM, and +L/-SM. Results showed that human-trampling disturbance interacted with the loss of native small mammals and the presence of non-native lagomorphs to cause large changes on biological (i.e., biocrust cover, bacterial and nifH genes abundance), physical (i.e., soil moisture and soil stability) and chemical (i.e., TC and TN) soil features. The relative impacts of trampling disturbance on biological and physicochemical features were strongly influenced by the presence of non-native lagomorphs. For example, larger decreases in biocrust cover and bacterial abundance were observed in treatments without lagomorphs (-L/+SM; -L/-SM). In turn, losses of biocrust cover, in addition to trampling, determined decreases in soil stability in all treatments. These results suggest that non-native lagomorphs surpass the effects of the loss of native small mammals in reducing soil quality and productivity. Therefore, human-trampling has the potential to convert low disturbed soils, as those observed in non-trampled soils in treatments -L/+SM, -L/-SM into poor soils with low biocrusts cover and concomitant low stability, as observed in +L/+SM; +L/-SM treatments. These findings agree with previous observations that different components of global change act in synergic ways in fragile, water-limited environments. Because biological invasions and soil surface disturbance are becoming widespread in dryland regions globally, understanding the long-term consequences of these interactions is essential.

Soils act as sinks or sources of CH4 depending on air-filled porosity in sclerophyllous ecosystems in semiarid central Chile

Carbon dioxide (CO2) and methane (CH4) are greenhouse gases (GHG), which sustained increase in the atmosphere contribute to global warming and climate change. The GHG fluxes of soils are strongly controlled by water content, temperature, plant and microbial communities and soil management. The Chilean sclerophyllous ecosystem is a global biodiversity hotspot historically and increasingly threatened by human activity. The aim of this study was to compare soil CH4 (and CO2) fluxes, under prevailing aerobic (dry hot summer) versus presumed partial anaerobic (wet winter) conditions, across a disturbance gradient in sclerophyllous ecosystems of central semiarid Chile. The CO2 fluxes were measured with an infrared gas analyzer (IRGA) while CH4 fluxes by gas chromatography using closed soil chambers. Soils were sources of CO2 (∼3.35 µmol CO2 m−2 s−1) drastically changing with vegetation and seasons. Soils were generally sinks of CH4 in summer (∼−3.75 nmol CH4 m−2 s−1) and sources in winter (∼+4.12 nmol CH4 m−2 s−1), which was mainly explained by air filled porosity. Modelled values showed that soils of the severely-disturbed A. caven savannah was overall a CH4 source (0.86 g CH4 m−2 year−1), while the strongly-disturbed thorn scrub (−0.56 g CH4 m−2 year−1) and the moderately-disturbed sclerophyllous forest (−2.68 g CH4 m−2 year−1) were sinks. Hence protecting sclerophyllous forests and restoring disturbed ecosystems may contribute to mitigate anthropogenic CH4 emissions.

The assemblage of epigean ants (Formicidae) inhabiting altered patches found in a latitudinal transect of coastal matorral of semiarid Chile

espanolRESUMEN Los propositos del estudio fueron documentar taxonomicamente la composicion del ensamble; estimar su riqueza de especies y describir el efecto del gradiente latitudinal y la condicion del matorral sobre la abundancia relativa de las especies y la riqueza del ensamble. Las hormigas fueron capturadas con trampas de intercepcion de caida (tipo pitfall). El estudio fue realizado entre 2008 y 2011. Registramos la presencia de cuatro especies endemicas y una introducida. El R maximo se estimo en seis. Solenopsis gayi (Myrmicinae) y Tapinoma antarticum (Dolichoderinae) fueron las especies numericamente dominantes. Observamos un efecto del piso latitudinal del matorral y de la condicion de este sobre la abundancia relativa de las especies, particularmente en el caso de las especies endemicas. Este efecto no siguio ni el gradiente latitudinal ni la condicion del matorral. Estas respuestas fueron especie-especificas, con influencia del sitio de estudio. La distribucion de R-estimado no mostro un patron evidente en ninguno de los dos casos. Consideramos que nuestros resultados evidencian una situacion compleja derivada del entrelazamiento de influencias debidas a la gradiente pluviometrica historica y a su efecto concomitante sobre la vegetacion, al estado actual del matorral y a la sequia severa a la que este estuvo sujeto durante el estudio. Es posible que bajo condiciones de precipitacion promedio o superior, los resultados sean diferentes. EnglishABSTRACT The aims of the study were to document taxonomically the composition of the assemblage; estimate its species richness, and describe the effect of latitudinal gradient and matorral condition on species relative abundance and species richness of assemblage. The ants were caught with interception traps (pitfall type). The study was conducted between 2008 and 2011. We recorded the presence of four endemic species and one introduced. Maximum R was estimated at six. Solenopsis gayi (Myrmicinae) and Tapinoma antarticum (Dolichoderinae) were the numerically dominant species. We observed an effect of both the latitudinal floor of matorral and the matorral condition on the relative abundance of the species, particularly in the case of endemic species. This effect did no follow neither the latitudinal gradient nor the matorral condition. The ants’ responses were species specific, with influence of the study site over that provided by latitudinal gradient and matorral condition. The distribution of estimated R did not show a clear pattern in any of the two cases. We believe that our results show a complex situation derived from the interweaving of influences due both to the historical rainfall gradient and its concomitant effect on vegetation, the current state of matorral, and the severe drought recorded during the study. It is possible that under conditions of mean precipitation or above, the results are different.

Bet-hedging strategies of native and exotic annuals promote coexistence in semiarid Chile

Scientists are increasingly interested in the evolutionary responses of organisms to unpredictable, variable, and extreme climate changes. In semiarid environments, inter-annual variability in the frequency and amount of rainfall affects both the growth and recruitment of plant species, especially annuals. In these inherently variable environments, individual selection should favor demographic responses that spread the risk of mortality over time and enhance long-term reproductive success (i.e., bet-hedging strategies). However, the same processes that allow the persistence and recruitment of native species could facilitate the introduction and establishment of exotics. We assessed whether native and exotic annuals in semiarid Chile displayed similar or contrasting bet-hedging traits, and discuss mechanisms of coexistence of both types of species and their demographic variation under interannual rainfall variability driven by El Niño Southern Oscillation (ENSO). We analyzed a proxy of long-term fitness, i.e., the variability of seed density over 17 years, for the two most common native and two exotic annual plant species present in the study area. We experimentally tested whether the quality of the maternal environment (soil water supply in a given year) had an extended effect (e.g. the next year) on the proportion of seed germination or on the mean and/or variability of seed size and seed dormancy. Results showed that native and exotic species in this annual plant assemblage displayed contrasting bet-hedging strategies as evolutionary responses to variable rainfall. Although rainfall variability promotes the evolution of bet-hedging strategies, the nature of these strategies varies across species, presumably to minimize competitive exclusion. In semiarid Chile, the success of two exotic ephemerals that are components of a diverse community of native annual species seems to reflect bet-hedging germination strategies that complement rather than compete with those expressed in dominant natives.

Functional traits variation explains the distribution of Aextoxicon punctatum (Aextoxicaceae) in pronounced moisture gradients within fog-dependent forest fragments.

Climate change and fragmentation are major threats to world forests. Understanding how functional traits related to drought tolerance change across small-scale, pronounced moisture gradients in fragmented forests is important to predict species’ responses to these threats. In the case of Aextoxicon punctatum, a dominant canopy tree in fog-dependent rain forest patches in semiarid Chile, we explored how the magnitude, variability and correlation patterns of leaf and xylem vessel traits and hydraulic conductivity varied across soil moisture (SM) gradients established within and among forest patches of different size, which are associated with differences in tree establishment and mortality patterns. Leaf traits varied across soil-moisture gradients produced by fog interception. Trees growing at drier leeward edges showed higher leaf mass per area, trichome and stomatal density than trees from the wetter core and windward zones. In contrast, xylem vessel traits (vessels diameter and density) did not vary producing loss of hydraulic conductivity at drier leeward edges. We also detected higher levels of phenotypic integration and variability at leeward edges. The ability of A. punctatum to modify leaf traits in response to differences in SM availability established over short distances (<500 m) facilitates its persistence in contrasting microhabitats within forest patches. However, xylem anatomy showed limited plasticity, which increases cavitation risk at leeward edges. Greater patch fragmentation, together with fluctuations in irradiance and SM in small patches, could result in higher risk of drought-related tree mortality, with profound impacts on hydrological balances at the ecosystem scale.

Temporal variation in Trypanosoma cruzi lineages from the native rodent Octodon degus in semiarid Chile

Chagas disease is a zoonosis caused by the protozoan parasite Trypanosoma cruzi and transmitted by triatomine insects to several mammalian species acting as reservoir hosts. In the present study, we assess T. cruzi-prevalence and DTU composition of the endemic rodent Octodon degus from a hyper-endemic area of Chagas disease in Chile. Parasite detection is performed by PCR assays on blood samples of individuals captured in the austral summers of 2010–2013. The infection level in rodents differed in the summers of these four years between 18% and 70%. Overall, infected O. degus showed similar T. cruzi-DTU composition (TcI, TcII, TcV and TcVI lineages) among years, corresponding to single and mixed infection, but the relative importance of each DTU changed among years. In 2013, we detected that only three out of the four T. cruzi-DTU found in O. degus were present in the endemic triatomine Mepria spinolai. We suggest that O. degus, an abundant long-lived rodent, is an important native reservoir of T. cruzi in the wild transmission cycle of Chagas disease and it is able to maintain all the T. cruzi-DTUs described in semiarid Chile.

Effects of mammal host diversity and density on the infection level of Trypanosoma cruzi in sylvatic kissing bugs

Several reports have described host species diversity and identity as the most important factors influencing disease risk, producing either dilution or amplification of the pathogen in a host community. Triatomine vectors, mammals and the protozoan Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae) Chagas are involved in the wild cycle of Chagas disease, in which infection of mammals occurs by contamination of mucous membranes or skin abrasions with insect-infected faeces. We examined the extent to which host diversity and identity determine the infection level observed in vector populations (i.e. disease risk in humans). We recorded infection in triatomine colonies and on the coexisting host mammalian species in semi-arid Chile. Host diversity, and total and infected host species densities are used as predictor variables for disease risk. Disease risk did not correlate with host diversity changes. However, the densities of each infected rodent species were positively associated with disease risk. We suggest that the infected host density surrounding the vector colonies is a relevant variable for disease risk and should be considered to understand disease dynamics. It is crucial to pay attention on the spatial scale of analysis, considering the pattern of vector dispersal, when the relationship between host diversity and disease risk is studied.

Factors affecting cactus recruitment in semiarid Chile: A role for nurse effects?

The nurse-protégé hypothesis states that adult plants of one species provide micro-environmental conditions that favor the establishment of seedlings of a second species with no effect for the first species. Several studies suggest this effect should be prevalent in arid and semiarid zones as adult plants often provide shelter from low moisture and high temperature. Echinopsis chiloensis and Eulychnia acida are endemic columnar cacti that inhabit the arid and semiarid zones of Chile. In this study, we examined the pattern of recruitment of both cactus species at Reserva Nacional Las Chinchillas, located ∼60km east from the Pacific coast. We determined number, growth and survivorship of young cacti (<30cm height) through biannual monitoring between 2009 and 2012 in microhabitats that strongly differ in their abiotic variables (minimum and maximum temperature and mean relative humidity, moisture content, and physical and chemical soil characteristics), under five different shrub species and in open spaces, and examined the association of these cacti with potential nurse plants. Most young cacti occurred under shrubs, the microhabitat having the lowest mean and maximum temperatures and the highest relative humidity. In particular, E. chiloensis and E. acida were found under the shrubs Flourensia thurifera and Bahia ambrosioides, respectively, in a higher frequency than expected by chance, suggesting that these shrub species behave as nurse plants through species-specific effects than are not accounted for by differences in soil nutrients.

Diverging drought-tolerance strategies explain tree species distribution along a fog-dependent moisture gradient in a temperate rain forest

The study of functional traits and physiological mechanisms determining species' drought tolerance is important for the prediction of their responses to climatic change. Fog-dependent forest patches in semiarid regions are a good study system with which to gain an understanding of species' responses to increasing aridity and patch fragmentation. Here we measured leaf and hydraulic traits for three dominant species with contrasting distributions within patches in relict, fog-dependent forests in semiarid Chile. In addition, we assessed pressure-volume curve parameters in trees growing at a dry leeward edge and wet patch core. We predicted species would display contrasting suites of traits according to local water availability: from one end favoring water conservation and reducing cavitation risk, and from the opposite end favoring photosynthetic and hydraulic efficiency. Consistent with our hypothesis, we identified a continuum of water use strategies explaining species distribution along a small-scale moisture gradient. Drimys winteri, a tree restricted to the humid core, showed traits allowing efficient water transport and high carbon gain; in contrast, Myrceugenia correifolia, a tree that occurs in the drier patch edges, exhibited traits promoting water conservation and lower gas exchange rates, as well low water potential at turgor loss point. The most widespread species, Aextoxicon punctatum, showed intermediate trait values. Osmotic compensatory mechanism was detected in M. correifolia, but not in A. punctatum. We show that partitioning of the pronounced soil moisture gradients from patch cores to leeward edges among tree species is driven by differential drought tolerance. Such differences indicate that trees have contrasting abilities to cope with future reductions in soil moisture.

Análisis de microhuellas de uso mediante Microscopio Electrónico de Barrido (MEB) de artefactos óseos de un sitio Arcaico tardío del valle de Mauro (Región de Coquimbo, Chile): Aportes para una reconstrucción contextual

This paper presents the results of Scanning Electron Microscope (SEM) analysisperformed on seven bone tools from MAU085, a Late Archaic site in the semiarid northof Chile (31o 57` S-71o 01`O, IV Region). The main objective of this analysis was todetermine the function of a set of bone tools and their relation with the morphologicalvariability identified. Given prior hypothesis linking the functionality of these bonetools to flaking and resharpening of projectile points and cutting artifacts, we soughtcomplementary information in both artefactual and ecofactuals evidence, specificallythe lithic remains. Analysis by Scanning Electron Microscope shows that the bonetools studied were used in lithic as well as soft contact materials such as leather/skinand textile fibers, thus expanding the use of artefacts traditionally considered boneretouchers.

Agriculture Vulnerability to Climate Change in a Snowmelt-Driven Basin in Semiarid Chile

AbstractThe Limari River basin is one of the most important watersheds in north-central Chile (30°S). Its headwaters lie at the top of the subtropical Andes (>5,000 m above sea level) and the river flows westward into the Pacific Ocean over a length of approximately 200 km. This basin has a marked snowmelt-driven hydrological regime and, in spite of the arid conditions that characterize this region, holds more than 50,000 ha of highly productive agricultural land thanks to its irrigation infrastructure and three interconnected reservoirs. Like many semiarid regions around the world, north-central Chile is expected to become warmer and drier during the 21st century as a consequence of ongoing anthropogenic climate change. The associated reduction in streamflow, changes in hydrograph timing, and enhanced evapotranspiration will undoubtedly threaten agriculture in the Limari basin and elsewhere in semiarid Chile. In this paper, the effect of temperature and precipitation on surface hydrology, performance of...