Fidel Roig Juñent

Age effects on the climatic signal in Araucaria araucana from xeric sites in Patagonia, Argentina

Background: At different cambial ages, trees experience changes in their structure and interactions with environmental conditions. Reciprocal mechanisms between tree age and physical resources, photosynthetic rates, and xylem production may influence hydraulic resistance and plant water stress. However, it is yet uncertain how these mechanisms are associated with changes in growth sensitivity to biophysical drivers, especially climate. Aim: To establish age-associated climate – growth relationships in growth rings of Araucaria araucana trees from the temperate xeric zones of northern Patagonia, Argentina. Methods: We analysed the growth in 211 A. araucana trees from four sampling sites, in three age classes: young (≤120 years), mature (121–275 years), and old (≥276 years). We explored the correlations between the signal strength of tree growth and climate, based on comparisons between each age-class chronology and monthly mean surface air temperature, total precipitation, and the Southern Annular Mode (SAM) index. Results: The young trees showed higher correlations when their growth was compared with precipitation, air temperature, and the SAM index during austral spring and summer months of the same year. In contrast, growth in mature and old trees showed higher correlations with summer temperatures of the previous growing season. Conclusions: The sensitivity of the radial-growth response of A. araucana to climate varies with age and is strongest in the rings of young trees.

Frost ring distribution in Araucaria araucana trees from the xeric forests of Patagonia, Argentina

Resumen en: Frost rings are defined as anatomically abnormal and ecophysiologically pathological structures. We studied frost injuries in tree-rings of Araucaria ara...

Geomorphological-related heterogeneity as reflected in tree growth and its relationships with climate of Monte Desert Prosopis flexuosa DC woodlands

Key messageAcross the Central Monte Desert district in Argentina, landform and soil variability drive radial growth ofProsopis flexuosaand its relation with precipitation.AbstractDesert forests grow under diverse ecological conditions, mainly resulting from the spatial heterogeneity of drylands with consequences on tree growth and its interactions with climate. In the Monte Desert, geomorphological processes generate landform and soil variability, determining the distribution and growth of plant species. Prosopis flexuosa DC., a dominant tree species in the Central Monte Desert, grows in territories characterized by a high variability of landform and soil. We applied classical dendrochronological and statistical analysis to disentangle the effect of spatial heterogeneity upon the species radial growth and its further relation with precipitation fluctuations. Trees from 11 plots distributed in seven P. flexuosa forests encompassing the most important geomorphological/landform units in the Central Monte Desert were analyzed. Tree-ring development at both high and low frequencies reflects spatial landform variability. Soil heterogeneity drives ring growth within landform. Regionally, precipitation influences radial growth at the beginning and the end of the growing season, while locally dependent mechanisms related to landform/soil variability emerged. In this sense, the negative influence of late-summer precipitation found for a riparian chronology is a function of soil permeability. Ring growth at the paleo-river environment depends on late spring and early mid-summer precipitation, with within-landform differences probably related to soil heterogeneity. In the case of inter-dune and lowland units, radial growth depends on early spring rainfall. Our findings highlight the influence of the heterogeneity of desert environments on tree growth. The information is relevant to management and conservation policies, particularly for the forests of P. flexuosa in Argentine Monte.

Macro- and microclimate conditions may alter grapevine deacclimation: variation in thermal amplitude in two contrasting wine regions from North and South America

Low temperature is a limiting factor that affects vineyard distribution globally. The level of cold hardiness acquired during the dormant season by Vitis sp. is crucial for winter survival. Most research published on this topic has been generated beyond 40° N latitude, where daily mean temperatures may attain injurious levels during the dormant season resulting in significant damage to vines and buds. Symptoms of cold injury have been identified in Mendoza (32–35° S latitude), a Southern Hemisphere wine region characterized by a high thermal amplitude, and warm winds during the dormant season. These symptoms have usually been attributed to drought and/or pathogens, but not to rapid deacclimation followed by injurious low temperatures. Because local information on meteorological events as probable causes is scarce, this research was designed to test and study this assumption by comparing macro-, meso-, and microclimatic data from Mendoza, Argentina, and eastern Washington, USA. The goal was to unveil why freezing damage has occurred in both regions, despite the existence of large climatic differences. Because environmental parameters under field conditions may not correspond to data recorded by conventional weather stations, sensors were installed in vineyards for comparison. Microclimatic conditions on grapevines were also evaluated to assess the most vulnerable portions of field-grown grapevines. In order to better understand if it may be possible to modify cold hardiness status in a short period with high thermal amplitude conditions, deacclimation was induced using a thermal treatment. Hence, despite the fact that Mendoza is warmer, and temperatures are not as extreme as in Washington, high daily thermal amplitude might be partially involved in plant deacclimation, leading to a differential cold hardiness response.