Recent consequences of climate change have affected tree growth in distinct Nothofagus macrocarpa (DC.) FM Vaz & Rodr age classes in Central Chile

Forests play an important role in water and carbon cycles in semiarid regions such as the Mediterranean ecosystems. Previous research in the Chilean Mediterranean forests revealed a break point in 1980 in regional tree-ring chronologies linked to climate change. However, it is still unclear which populations and age classes are more affected by recent increases in drought conditions. In this study, we investigated the influence of recent variations in precipitation, temperature, and CO2 concentrations on tree growth of various populations and age classes of Nothofagus macrocarpa trees in Central Chile. We sampled 10 populations from five sites of N. macrocarpa through its whole geographic distribution in both Coastal and Andes ranges. We used standard dendrochronological methods to (i) group populations using principal component analysis, (ii) separate age classes (young, mature, and old trees), (iii) evaluate linear growth trends based on the basal area increment (BAI), and (iv) analyze the link between BAI and atmospheric changes using linear mixed-effects models. Results showed that young trees are more sensitive to climate variability. Regarding population grouping, we observed that all population clusters were sensitive to winter-spring precipitation, but only the Andes and Coastal populations were negatively correlated with temperature. The results of CO2 fertilization analyses were controversial and unclear. Since young trees from all population clusters reacted positively in the phase with an increase of atmospheric CO2 between 1980 and 2014, this behavior was not translated into growth for the last 15 years (2000-2014). However, it should be noted that the young trees of the highest elevation populations did not have a negative growth trend, so it seems that CO2 counteracted the negative effect of recent regional climate change (increase in temperature and precipitation decrease) in these population trees. Further studies are needed to assess the effects of climate variability over other ecological and physiological processes.Fil: Venegas González, Alejandro. Universidad Mayor.; ChileFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Peña Rojas, Karen. Universidad de Chile; ChileFil: Hadad, Martín Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Aguilera Betti, Isabella. Pontificia Universidad Católica de Valparaíso; Chile. Universidad Austral de Chile; ChileFil: Muñoz, Ariel A.. Pontificia Universidad Católica de Valparaíso; Chil

Six hundred years of South American tree rings reveal an increase in severe hydroclimatic events since mid-20th century

South American (SA) societies are highly vulnerable to droughts and pluvials, but lack of long-term climate observations severely limits our understanding of the global processes driving climatic variability in the region. The number and quality of SA climate-sensitive tree ring chronologies have significantly increased in recent decades, now providing a robust network of 286 records for characterizing hydroclimate variability since 1400 CE. We combine this network with a self-calibrated Palmer Drought Severity Index (scPDSI) dataset to derive the South American Drought Atlas (SADA) over the continent south of 12°S. The gridded annual reconstruction of austral summer scPDSI is the most spatially complete estimate of SA hydroclimate to date, and well matches past historical dry/wet events. Relating the SADA to the Australia–New Zealand Drought Atlas, sea surface temperatures and atmospheric pressure fields, we determine that the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) are strongly associated with spatially extended droughts and pluvials over the SADA domain during the past several centuries. SADA also exhibits more extended severe droughts and extreme pluvials since the mid-20th century. Extensive droughts are consistent with the observed 20th-century trend toward positive SAM anomalies concomitant with the weakening of midlatitude Westerlies, while low-level moisture transport intensified by global warming has favored extreme rainfall across the subtropics. The SADA thus provides a long-term context for observed hydroclimatic changes and for 21st-century Intergovernmental Panel on Climate Change (IPCC) projections that suggest SA will experience more frequent/severe droughts and rainfall events as a consequence of increasing greenhouse gas emissions

Tasas diarias de transpiración y relaciones hídricas en especies arbóreas con distinto nivel de sombra tolerancia en un bosque templado chileno Daily transpiration rates and hydraulic relationships in tree species with different shade-tolerance level in a Chilean temperate forest

En general se sabe que especies pioneras que sostienen altas tasas de crecimiento, transpiración y fotosíntesis son más tolerantes a la sequía y soportan mayores temperaturas, mientras que especies sombra tolerantes lo contrario. Sin embargo, no existen antecedentes respecto a los volúmenes diarios de agua transpirada a nivel de árbol en especies del bosque templado del sur de Chile, ni antecedentes respecto a la coordinación entre los rasgos funcionales involucrados en el transporte de larga distancia. El objetivo de este estudio fue cuantificar los volúmenes diarios de agua transpirada por cuatro especies arbóreas de diferente grado de sombra tolerancia en un bosque templado lluvioso del sur de Chile, así como evaluar su relación con diferentes rasgos funcionales asociados al transporte hídrico en tronco, ramas y hojas. Se encontró que existen diferencias significativas en las tasas diarias de transpiración entre especies, las que varían entre 0,07 y 0,01 lt cm-2dia-1 para Nothofagus dombeyi (Mirb.) Oerst. y Laureliopsisphilippiana (Looser) Schodde respectivamente. Contrario a lo esperado, ni la conductividad hidráulica específica (K ) ni la conductividad hidráulica foliar (K L) estuvieron bien correlacionadas con las tasas diarias de transpiración. Sin embargo, las especies menos tolerantes a la sombra presentaron rasgos asociados a una mayor tolerancia a la sequía y mientras que la semi-tolerante Eucryphia cordifolia Cav. estaría sufriendo importantes restricciones hídricas durante el verano.In general, pioneer species are known for supporting high transpiration, growth and photosynthesis rate, for being more drought tolerant and resist higher temperatures than shade-tolerant species. However, there is not information about rates of transpiration at the tree level in species of Chilean temperate forest, or about the coordination between hydraulic functional traits. We report here, transpiration rates of four tree species with different levels of shade tolerance in Chilean temperate rainforest, and explored some functional traits associated with water transport efficiency and drought tolerance. We found significant differences in daily transpiration rates ranging between 0.07 and 0.01 lcm-2day-1 in Nothofagus dombeyi (Mirb.) Oerst. and Laureliopsisphilippiana (Looser) Schodde respectively. Contrary to expectations, specific hydraulic conductivity (KS ) and leaf hydraulic conductivity (K L) were not well correlated with transpiration daily rates. However, the species less tolerant to shade showed traits associated with greater drought tolerance, while the semi-tolerant Eucryphia cordifolia Cav. showed important evidence of hydraulic restrictions during summer

A network for advancing dendrochronology, dendrochemistry and dendrohydrology in South America

Tree-ring research (TRR) in South America (SA) continues to make important contributions in multiple sub-disciplines, including dendrochemistry and dendrohydrology. This report describes some of the advances in TRR in SA presented in a two-day International Meeting Research entitled "An International Network to Promote Advances in Dendrochronology in South America", organized by the Laboratory of Dendrochronology and Environmental Studies of the Pontifical Catholic University of Valparaíso in Valparaíso, Chile, on January 21-22, 2019. The objective of the meeting was to communicate recent advances in TRR within a network of laboratories in Argentina, Brazil, Chile, Peru, and Uruguay. Novel methodologies and results in dendrochemistry and wood anatomy were also presented by collaborating researchers from German institutions. This report describes some of the research within the subdisciplines of tree-ring science, including dendrochemistry, anatomy and dendrohydrology, and their application to understanding spatio-temporal variability in heavy metal contamination, climate, hydrology, fire regimes and other critical components of South American forest and woodland ecosystems. The meeting demonstrated expansion and diversification of inquiry and applications of TRR in SA, whereby collaboration across research centers has been critical for the advances made in broad-scale comparative studies as well as multi-proxy approaches and the study of global and hemisphere-scale climate phenomena.Fil: Aguilera Betti, Isabella. Pontificia Universidad Católica de Valparaíso; Chile. Universidad Austral de Chile; ChileFil: Lucas, Christine. Universidad de la República; UruguayFil: Ferrero, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Muñoz, Ariel A.. Pontificia Universidad Católica de Valparaíso; Chil

Crecimiento radial de Abies pinsapo en el sur de Chile: relaciones con el clima local y su comparación con poblaciones naturales en España

Se estudió la relación entre el crecimiento de un rodal de Abies pinsapo de 43 años de edad cercano a la ciudad de Valdivia, Chile, y la variabilidad del clima local. Los objetivos fueron identificar los factores y periodos climáticos que regulan su crecimiento radial, comparando paralelamente sus tasas de crecimiento con dos rodales naturales de la especie en España, país que junto a Marruecos alberga sus últimas poblaciones. Las tasas de crecimiento en Valdivia fueron similares o superiores a los sitios de su hábitat natural, favorecidas en Chile por veranos cálidos y poco lluviosos, así como por abundantes precipitaciones invernales. A nivel de madera temprana y tardía, la primera se relacionó con las condiciones de los veranos previos, demostrando su relación con sustancias de reserva, mientras que la madera tardía, presentó una señal climática dominada por características de la estación de crecimiento corriente. Estos resultados indican que el clima templado-lluvioso de la región de Los Ríos, menos extremo que el clima de montaña de su hábitat natural, favorece el crecimiento de la especie constituyendo un hábitat alternativo para su conservación. Aquí la temperatura de verano favorece su crecimiento, a diferencia de su hábitat natural, donde el déficit hídrico es el factor que controla su crecimiento. Esta información puede ser relevante para la conservación ex-situ de una de las coníferas más amenazadas por el cambio climático y la presión humana en el sur de la península ibérica. ----------ABSTRACT---------- The relationship between the growth of 43-year old specimens of an Abies pinsapo Boiss stand located in the city of Valdivia (Chile) and the climatic variability of this site was studied. The objectives were to define the climatic response function and identify the climatic variables and periods that regulate radial growth rates and to compare the annual radial growth with those characterizing two natural stands of the same species growing in Spain provinces, which, together with Morocco, shelters its last populations. Growth rates in Valdivia, Chile, were similar to or even higher than those in their natural habitat, showing a predilection for warm summers with little rain, as well as for abundant winter precipitation. In relation to the early wood (EW) and late wood (LW) series, the first one was related with prevalent dominant climatic conditions of the previous summer. This may be related to stored food. Late wood showed a climatic signal controlled by dominant conditions of the current growing season. These results indicate that the temperate-rainy climate in Los Ríos Region (Chile), milder than the mountain climate in its original habitat, favors the growth of this species and therefore constitutes an alternative habitat for its conservation. Here, summer temperatures favor its growth, differing from its natural habitat, where soil-water availability is the major factor controlling its growth. This information can be relevant for ex-situ conservation of one of the most severely threatened conifers by climate change and human pressure in the south of the Iberian Peninsula

Cross-continental hydroclimate proxies: Tree-rings in Central Chile reconstruct historical streamflow in Southeastern South American Rivers

Regional teleconnections permit cross-continental modeling of hydroclimate throughout the world. Tree-rings are a good hydroclimatic proxy used to reconstruct drought and streamflow in regions that respond to common global forcings. We used a multi-species dataset of 32 tree-ring width chronologies from Chile and Uruguay as a climate proxy to infer annual streamflow (Q) variability in the Negro River basin, a grassland-dominated watershed of lowland Southeastern South America. A positive linear correlation between tree-ring chronologies from Central Chile and annual Negro River instrumental streamflow from 1957 to 2012 indicated a cross-continental teleconnection between hydroclimate variability in Central Chile and Northeastern Uruguay. This relationship was mediated in part by the El Niño Southern Oscillation (ENSO), whereby the El Nino 3.4 Index was positively correlated with regional rainfall, annual tree growth, and Q anomalies. Despite the proximity of Uruguayan tree-ring chronologies to Negro River hydrometric stations, the Chilean tree-ring chronologies best predicted annual streamflow. Thus, using tree-ring data from four long-term moisture-sensitive chronologies of the species Cryptocarya alba in Central Chile (32–34°S), we present the first streamflow reconstruction (1890–2009) in the lower La Plata Basin. The reconstruction supports regional evidence for increasing frequency of extreme flood years over the past century in Uruguay. We demonstrate how climate teleconnections that mediate local hydroclimate variability permit the cross-continental reconstruction of streamflow, filling a major geographical gap in historical proxies for flooding and drought in grassland biomes of the southern hemisphere

Prosopis L. woody growth in relation to hydrology in South America: A review

Arboreal species of the genus Prosopis L. have played an important role in the development of tree-ring research in arid and semi-arid ecoregions of South America. Given the distribution of Prosopis across a broad precipitation gradient from 0 to 2000 mm y−1 and its unique role as a phreatophyte, the relationship between Prosopis species growth and water has been a recurring theme over the past century. We conducted a systematic review of the literature addressing Prosopis and water research in South America, and combined site coordinates with GIS data of mean annual precipitation (MAP), elevation, biome, and soil moisture from online databases to understand the spatial distribution of research to date. We compiled 40 publications from 1931 to 2022, including results from 11 species of Prosopis among four countries, on the relationship between Prosopis spp and precipitation, groundwater levels, soil humidity, among other hydrological parameters. The spatial distribution of research sites spans tropical-subtropical and temperate latitudes from 4° to 35°S, excluding regions where the genus is present in Patagonia and northeastern South America. Studies covered a broad range of elevations from 30 to 3500 m a.s.l. but was limited to 1–730 mm y−1 MAP, excluding more humid climates where Prosopis occurs. Results obtained from 32 dendrochronological studies and eight studies relating to Prosopis and hydrology, were grouped into sub-disciplines of tree-ring formation and the hydrosystem, dendroclimatology, dendrohydrology, and dendroecology. The review highlights the unique affinities of Prosopis to arid conditions, and the use of tree rings as a proxy for historical droughts and variability in water tables. Nonetheless, there are opportunities to expand the geographical-climatological extent of Prosopis growth research to humid climates, as well as to incorporate novel techniques such as stable isotopes and vessel size chronologies to understand how this genus records hydrological change throughout South America.Fil: Ambite, Serrana. Universidad de la Republica; UruguayFil: Ferrero, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Continental; PerúFil: Piraino, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cuyo. Facultad de Cs.agrarias. Cátedra de Dasonomia; ArgentinaFil: Badagian, Juan. Universidad de la Republica. Centro Universitario del Litoral Norte.; UruguayFil: Muñoz, Ariel A.. Pontificia Universidad Católica de Valparaíso; Chile. Centro de Ciencia del Clima y la Resiliencia; ChileFil: Aguilera Betti, Isabella. Pontificia Universidad Católica de Valparaíso; Chile. Universidad de Magallanes; Chile. Universidad Austral de Chile; ChileFil: Gamazo, Pablo. Universidad de la Republica. Centro Universitario del Litoral Norte.; UruguayFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Mayor; ChileFil: Lucas, Christine. Universidad de la Republica. Centro Universitario del Litoral Norte.; Urugua

Water crisis in Petorca basin, Chile: The combined effects of a mega-drought and water management

Since 2010, Chile has experienced one of the most severe droughts over the last century, the so-called mega-drought (MD). The MD conditions, combined with intensive agricultural activities and the current water management system, have led to water scarcity problems in Mediterranean and Semi-arid regions of Chile. An emblematic case is the Petorca basin, where a water crisis is undergone. To characterize this crisis, we analyzed water provision by using tree-ring records, remote sensing, instrumental data, and allocated water rights within the basin. Results indicate that the MD is the most severe dry period over the last 700-years of streamflow reconstruction. During the MD, streamflow and water bodies of the upper parts of the basin have been less affected than mid and low areas of this valley, where consumptive withdrawals reach up to 18% of the mean annual precipitation. This extracted volume is similar to the MD mean annual precipitation deficits. The impacts of the current drought, along with the drier climate projections for Central Chile, emphasize the urgency for faster policy changes related to water provision. Climate change adaptation plans and policies should enhance the current monitoring network and the public control of water use to secure the water access for inhabitants and productive activities.Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 11161061 1181956 3170428 Center for Climate and Resilience Research (CR)2 FONDAP 1511000