Prumnopitys Andina Research Articles

Species-specific influence of hydroclimate on secondary growth of three coexisting conifers in a temperate Andean forest in south-central Chile

There is limited knowledge on the growth responses of coexisting conifer species to water conditions in the Andean region of South America- particularly in South-Central Chile (37°−40°S) where high temperatures and drought risk is expected to increase in the future. Here, we used wood cores from living trees and cross-sections of stumps to study the secondary growth responses to hydroclimatic environmental variables in Araucaria araucana, Austrocedrus chilensis and Prumnopitys andina, three coexisting conifers in a temperate Andean forest. The standardized tree-ring chronologies are robust and have been well replicated over the past two centuries, with an expressed population signal greater than 0.90. Our findings indicate that chronologies of Austrocedrus and Prumnopitys were quite similar, while Araucaria was almost independent. The secondary growth of Araucaria was negatively related to August precipitation and river runoff, likely due to a high probability of snow cover at high elevations in winter. In contrast, the secondary growth of Austrocedrus and Prumnopitys was positively associated with precipitation and streamflow and negatively with high maximum temperatures in two seasons, summer (December to February) and autumn (April to May). Prumnopitys growth was strongly associated with streamflow during last year´s and current year´s growing seasons. In the years 1962, 1998 and 2008 there occurred severe droughts, which were associated with growth reductions in the three conifers. Araucaria growth showed the greatest resistance to drought, while Austrocedrus was the most resilient to drought and showed the greatest ability for growth recovery after a drought. Araucaria growth showed near-constant resistance, recovery and resilience to drought during the study period, while Austrocedrus growth showed high recovery and resilience after the 1962 and 2008 droughts. Our results revealed contrasting behavior of coexisting conifers with respect to hydroclimate, which could help predict future changes in the performance of temperate Andean forests in a potentially drier and warmer climate.

Prumnopitys Andina Fruit Extract Activates Liver X Receptors after InVitro Digestion.

20-Hydroxyecdysone (20E) is the main phytochemical present in the fresh arils of Prumnopitys andina. 20E is reported to have anabolic effects by modulation of gene transcription by interaction with nuclear receptors. Our aim is to evaluate the in vitro bioaccessibility, transepithelial transport of 20E, and the capacity of P. andina fruit extract and 20E to activate selected mammalian nuclear receptors in transiently transfected human cells after simulated gastrointestinal digestion. 20E shows good stability, solubility, and micellization after in vitro digestion. 20E is taken up by Caco-2 cells, but poorly transported through the epithelial cell membrane, possibly due to P-glycoprotein-mediated efflux. In transiently transfected HepG2 cells, the fruit extract significantly induces the signal intensity for the liver X receptor (LXR)-α and -β by 1.6 and 1.4-fold, respectively. In contrast, the treatment with 20E, irrespective of its concentration, did not change the activity of both LXR receptors. No effects are observed for the pregnane X receptor or the constitutive androstane receptor. Our findings show that components of the digested P. andina extract other than 20E are responsible for the effects on LXR-α and -β. Our findings open new perspectives on the potential role of P. andina fruits in cholesterol metabolism and inflammatory diseases.

Phytochemical characterization and antioxidant properties of Prumnopitys andina fruits in different ripening stages in southern Chile

The native conifer lleuque (Prumnopitys andina (Poepp. ex Endl.) de Laub.) grows in southern Chile, and has an edible and fleshy ovoid fruit. Some species of the genus Prumnopitys are valuable for the medicinal value of their edible fruits. Thus, the aim of this research was to characterize the phytochemical and antioxidant compounds in four ripening stages of P. andina fruits from La Araucanía Region, Chile. Fruit quality related parameters, bromatological, antioxidant and phenolic compounds analyses were performed in order to highlight their potential for human consumption. Our study showed that fresh weight, equatorial diameter, and soluble solid content significantly increased (P < 0.05) in P. andina fruits during ripening, reaching 4.02 ± 0.2 g, 17.9 ± 0.6 mm, and 23.7 ± 0.5 °Brix, respectively, per fruit at stage IV. Our bromatological analyses showed that P. andina fruits had 1.17 ± 0.1 g 100 g-1 DW protein, 1.55 ± 0.2 g 100 g-1 DW crude fiber, and 10.76 ± 2.2 g 100 g-1 DW fruit of ash at fruit ripe. Likewise, we found 2.6 ± 0.2 mg g-1 FW total phenols, 2.2 ± 0.2 mg trolox equivalent g-1 FW of antioxidant activity, and 6.4 ± 0.2 mg rutin equivalent g-1 FW total flavonoid in P. andina fruits. Interestingly, ripening stages I and II showed higher antioxidant compound levels compared to stages III and IV, with the exception of total anthocyanins, which did not change throughout the ripening process. This study shows that P. andina has great potential as a fruit with significant functional properties, which could help promote the propagation, care, and use of this native conifer.

Changes of cell wall-associated polysaccharides and sugars during development and ripening of arrayan (Luma apiculata) and lleuque (Prumnopitys andina) fruits

Changes of cell wall-associated polysaccharides and sugars during development and ripening of arrayan (Luma apiculata) and lleuque (Prumnopitys andina) fruits

Dendrochronological potential of Prumnopitys andina (Podocarpaceae) at the southern limit of its range in the Chilean Andes

ABSTRACT Prumnopitys andina is a South American podocarp with a restricted distribution in southern Andean temperate forests, and is severely threatened due to habitat loss. Despite much dendrochronological work on other temperate South American conifers, little is known about the dendrochronological potential of P. andina. Here, we examine the main features of P. andina tree rings and evaluate the potential of this species for yielding tree-ring chronologies sensitive to climatic variability. In a population at the southern range limit of the species, we collected tree cores and cross-section samples of P. andina for analyses following standard dendrochronological techniques. 76 tree-ring series from 45 trees were examined, 32 (42%) of which were successfully cross-dated and included in a chronology. We found that the species forms well-defined tree rings with distinct boundaries delimiting annual growth. The chronology began in 1778, with notable periods of suppression and release occurring in the late nineteenth and early twentieth centuries, respectively. The chronology showed a high inter-series correlation value of 0.51, suggesting a strong common signal among trees. December to January precipitation showed a positive relationship with radial growth. Conversely, maximum and mean temperature showed negative relationships with radial growth during the austral summer and autumn. These significant relationships of climate variables with radial growth of P. andina indicate that tree-ring series of this species are suitable for dendroclimatological studies.

Estructura y regeneración de bosques de Prumnopitys andina en los Andes del sur de Chile

Prumnopitys andina is a conifer tree species with a narrow distribution in Chile and Argentina. Despite its ecological importance, knowledge about the structure and dynamics of the forests where P. andina grows is limited. We aim to describe the structure and regeneration of forest with high presence of P. andina. Forests near Lonquimay (38°1' S, 71.3 W - 38°3'S, 71°3' W) were sampled by measuring trees, regeneration and vascular flora through 24 plots. We found that P. andina predominantly occurs in the upper canopy (15-18 m), usually in company of Nothofagus obliqua and/or Austrocedrus chilensis, in addition to Maytenus boaria and Lomatia hirsuta that occur in the mid-canopy (4-8 m). Based on forest structure, we identified three types of P. andina forests: open, secondary-mature, and pure. Pure P. andina forests reached basal areas among the largest reported for for temperate forests southern South America (230 m2/ha). P. andina regeneration ranged from 1,550 individuals/ha in open forests to 25,000 individuals/ha in pure forests. P. andina exhibited a continuous regeneration strategy, which in the absence of human disturbances, such as grazing by cattle or selective logging, suggests that its populations are self-sustaining.

Andean Prumnopitys Andina (Podocarpacae) Fruit Extracts: Characterization of Secondary Metabolites and Potential Cytoprotective Effect.

The fruits from the Chilean Podocarpaceae Prumnopitys andina have been consumed since pre-Hispanic times. Little is known about the composition and biological properties of this fruit. The aim of this work was to identify the secondary metabolites of the edible part of P. andina fruits and to assess their antioxidant activity by means of chemical and cell-based assays. Methanol extracts from P. andina fruits were fractionated on a XAD7 resin and the main compounds were isolated by chromatographic means. Antioxidant activity was determined by means of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), ferric reducing power (FRAP), trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays. The cytoprotective activity of the extract against oxidative and dicarbonyl stress was evaluated in human gastric epithelial cells (AGS). The total intracellular antioxidant activity (TAA) of the extract was determined in AGS cells. The inhibition of meat lipoperoxidation was evaluated under simulated gastric digestion conditions. Rutin, caffeic acid β-glucoside and 20-hydroxyecdysone were identified as major components of the fruit extract. Additional compounds were identified by high-performance liquid chromatography diode-array detector mass spectrometry (HPLC-DAD-MSn) and/or co-injection with standards. Extracts showed dose-dependent cytoprotective effects against oxidative and dicarbonyl-induced damage in AGS cells. The TAA increased with the pre-incubation of AGS cells with the extract. This is the first report on the composition and biological activity of this Andean fruit.

DO ENVIRONMENTAL FACTORS AFFECT THE TAXONOMIC RELIABILITY OF LEAF CUTICULAR MICROMORPHOLOGICAL CHARACTERS? A CASE STUDY IN PODOCARPACEAE

Leaf cuticle micromorphology has been cited as an important set of taxonomic characters in gymnosperms, but previous studies have largely been based on small sample sizes. The premise of this study was to understand whether external factors affect cuticular micromorphology of Podocarpaceae. Two example species, Prumnopitys andina and Podocarpus salignus, were studied. Of 21 sampled characters, nine (c.43% of the total) were visually assessed as being moderately reliable or highly reliable for taxonomic discrimination for both species, with an additional six (c.29%) being moderately reliable or highly reliable for only one or other of the example species, and six characters (c.29%) unreliable for both. Seven of the most variable stomatal characters were selected for further analysis to establish whether environmental factors affect them. The relationship between these seven stomatal characters, the environment and climate was analysed using the R ‘vegan’ package and climate data gathered from WorldClim. Our results showed that both species had larger stomata in moist and shady conditions, and a higher density of (smaller) stomata in sunny and drier conditions. An additional novel finding was the presence of stomata on the adaxial leaf surface in 46% of samples of Prumnopitys andina: the first record of adaxial stomata in this species, highlighting the necessity of studying multiple samples of a given species. In conclusion, these results indicate that larger sample sizes than have hitherto been employed in cuticle micromorphological studies are necessary to fully document the amount of phenotypic variation that exists.

The lleuque forests of South Central Chile: a phytosociological study and syntaxonomical classification within South American temperate forests

This paper is a phytosociological study of a forest community dominated by the lleuque (the Araucanian name for the podocarpaceae Prumnopitys andina). This is a mixed forest community with gymnosperm and broad-leaved trees growing in a temperate sub-Mediterranean climate, with a somewhat continental character within the very oceanic territory of Chile. The paper describes the new Nothofago obliquae-Prumnopitydetum andinae association, mostly located between the Bío-Bío and La Araucanía regions (parallels 36º to 40º south). We deal with the bioclimatic characteristics of the community, its biogeographical restrictions and its continuing presence in special topographical sites. The paper not only analyzes the floristic composition of the community in order to ascribe it syntaxonomically to the Wintero-Nothofagetea class, but also considers a number of floristic arrangements which support a reinterpretation of some syntaxa which are phytosociologically ranked as orders or classes.

Late Quaternary vegetation and fire history in the northernmost Nothofagus forest region: Mallín Vaca Lauquen, Neuquén Province, Argentina

AbstractThe last 16 000 cal. a of vegetation, fire and limnological history are described from the steppe‐forest ecotone in the northernmost Nothofagus forest region east of the Andes (Mallín Vaca Lauquen, Neuquén Province, Argentina, latitude 36° 51.336′ S, longitude 71° 02.538′ W). Between 16 000 and 14 800 cal. a BP, scrub steppe with substantial open ground expanded in formerly glaciated valleys, whereas Nothofagus–Prumnopitys andina woodland covered mountain slopes. The site was a relatively deep and unproductive small lake at this time. After 14 800 cal. a BP, both steppe and woodland vegetation became denser, indicating increased moisture and temperatures, although not to present levels. The lake was still relatively deep and dystrophic, but became more alkaline by 10 000 cal. a BP. Between 8900 and 5500 cal. a BP, conditions were markedly drier than before; a Cyperaceae marsh developed and disturbance taxa increased. After 5500 cal. a BP, moisture increased but varied greatly, as evidenced by fluctuating water levels and high fire activity from 5500 to 4400 cal. a BP and from 2300 to 1000 cal. a BP. Human activity, in terms of forest clearance and livestock grazing, is documented in the uppermost levels. The evidence of high environmental variability in the middle and late Holocene is consistent with the onset or strengthening of the El Niño–Southern Oscillation, but differences in the timing of fire activity among sites on the west and east sides of the Andes suggest that fuel conditions were important in determining the local occurrence of fire. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Cycloaspeptide A and Pseurotin A from the Endophytic Fungus Penicillium janczewskii

Penicillium janczewskii K. M. Zalessky was isolated as an endophytic fungus from the phloem of the Chilean gymnosperm Prumnopitys andina. When grown in liquid yeast extract-malt extract-glucose broth, the fungus produced two main secondary metabolites. The compounds were for the first time isolated from this species and identified by spectroscopic methods as pseurotin A and cycloaspeptide A. This is the first report on the production of cyclic peptides by endophytic fungi from Chilean gymnosperms. Pseurotin A and cycloaspeptide A presented low cytotoxicity towards human lung fibroblasts with IC50 > or = 1000 microM. Pseurotin A showed a moderate effect against the phytopathogenic bacteria Erwinia carotovora and Pseudomonas syringae, with IC50 values of 220 and 112 microg ml(-1), respectively.

2β-Acetoxyferruginol—A new antibacterial abietane diterpene from the bark of Prumnopitys andina

As part of an on-going project to isolate antibacterial compounds from rare conifer species, a new abietane diterpene, 2β-acetoxyferruginol was isolated from the stem bark of Prumnopitys andina. Molecular modelling studies were conducted to explain some of the NOEs observed in the A-ring of this compound and to support assignment of relative stereochemistry. This new compound had antibacterial activity at 8 μg/ml against two effluxing strains of Staphylococcus aureus, but interestingly was inactive at 128 μg/ml against a wild-type strain and against a methicillin-resistant (MRSA) clinical isolate. We have previously demonstrated that ferruginol is active against these four S. aureus stains and therefore the results indicate that the presence of the acetoxy group has a detrimental effect on antibacterial activity against certain strains. 2β-Acetoxyferruginol was also assayed against Propionibacterium acnes and was active at 4 μg/ml.

Chilean and Southeast Pacific paleoclimate variations during the last glacial cycle: directly correlated pollen and δ18O records from ODP Site 1234

Joint pollen and oxygen isotope data from Ocean Drilling Program Site 1234 in the southeast Pacific provide the first, continuous record of temperate South American vegetation and climate from the last 140 ka. Located at ∼36°S, ∼65 km offshore of Concepcion, Chile, Site 1234 monitors the climatic transition zone between northern semi-arid, summer dry-winter wet climate and southern year-round, rainy, cool temperate climate. Dominance of onshore winds suggests that pollen preserved here reflects transport to the ocean via rivers that drain the region and integrate conditions from the coastal mountains to the Andean foothills. Down-hole changes in diagnostic pollen assemblages from xeric lowland deciduous forest (characterized by grasses, herbs, ferns, and trees such as deciduous beech, Nothofagus obliqua), mesic Valdivian Evergreen Forest (including conifers such as the endangered Prumnopitys andina), and Subantarctic Evergreen Rainforest (comprised primarily of southern beech, N. dombeyi) reveal large rapid shifts that likely reflect latitudinal movements in atmospheric circulation and storm tracks associated with the southern westerly winds. During glacial intervals (MIS 2-4, and 6), rainforests and parkland dominated by Nothofagus moved northward into the region. At the MIS 6/5e transition, coeval with the rapid shift to lower isotopic values, rainforest vegetation was rapidly replaced by xeric plant communities associated with Mediterranean-type climate. An increased prominence of halophytic vegetation suggests that MIS 5e was more arid and possibly warmer than MIS 1. Although rainforest pollen rises again at the end of MIS 5e, lowland deciduous forest pollen persists through MIS 5d and 5c, into MIS 5b. Substantial millennial-scale variations occur in both interglacial and glacial regimes, attesting to the sensitivity of the southern westerly belt to climate change. Comparison of the cool, mesic N. dombeyi rainforest assemblage from Site 1234 with δ 18O in the Byrd Ice core shows that on time scales longer than ∼10 ka, cool-moist conditions in central Chile were coherent with and occurred in phase with Antarctic cooling. This is also likely at millennial scales, although rainforest pollen lags Antarctic cooling with exponential response times of about 1000 years, which plausibly reflects the ecological response time to regional climate change.

Gastroprotective and ulcer healing effect of ferruginol in mice and rats: Assessment of its mechanism of action using in vitro models

The gastroprotective activity of the diterpene ferruginol isolated from Prumnopitys andina wood and bark was determined on HCl/EtOH-induced gastric lesions in mice. The effect of the compound on the healing of subacute gastric lesions in rats was also studied. The mode of action of the diterpene was assessed using human gastric epithelial cells (AGS) and MRC-5 fibroblasts. The effect of ferruginol on the prostaglandin E 2 content, protection against sodium taurocholate induced-damage and reduced glutathione content was evaluated on AGS cells as well as on the growth of AGS and fibroblast cultures. The free radical scavenging effect of ferruginol was assessed by the 1,1-diphenyl-2-picryl-hydrazil radical and superoxide anion assays. The effect of ferruginol on human erythrocyte membrane lipoperoxidation was determined. The cytotoxicity of the compound was assessed by means of the neutral red uptake. At 25 mg/kg, ferruginol inhibited the appearance of gastric lesions by 60% showing similar effects than lansoprazole at 20 mg/kg. Additionally, the compound displayed a significant ulcer healing activity in rats at 25 and 50 mg/kg with curative ratios of 36.0% and 92.5%, respectively, while the reference compound ranitidine at 50 mg/kg showed a curative ratio of 79.6%. At 6 and 12 μM, ferruginol increased significantly the prostaglandin E 2 content. A strong inhibition of lipoperoxidation was found (IC 50: 1.4 μM), but no effect was observed on the sodium taurocholate induced-damage or reduced glutathione content. Ferruginol stimulated cell proliferation at 1–2 μM in AGS cells and at 4–8 μM in fibroblasts, with cytotoxicities (IC 50) of 24 and 26 μM, respectively. Our results support that ferruginol acts as gastroprotective increasing the PGs content, protecting the cells against lipid peroxidation and improving the gastric ulcer healing by a stimulating effect on the cell proliferation. These findings encourage further pharmacological studies of ferruginol as a potential new anti-ulcerogenic drug.

Preliminary Advice on Fruit Handling, Seed Pretreatment and 'Germination' of Embryos of Prumnopitys andina

Prumnopitys andina is a member of the Podocarpaceae native to Chile and Argentina. It is known to be relatively easy to propagate vegetatively, but germination from seeds is poor and can be spread over at least four years. This paper describes the methods that were used to raise 89 seedlings from 262 seeds (=34%) in less than 1 year. The sequence involves i) completely removing the fleshy sarcotesta; ii) thoroughly washing the seed-coat; iii) `pretreating' the imbibed seeds by incubating them in moist peat and sand at a daily alternating 10/15°C for several months (to allow 'maturation' or `after-ripening' / 'dormancy breakage' at present we do not know which); iv) carefully cracking the seed-coat in a vice and extracting the embryo; v) culturing clean, firm, healthy (=-`viable') embryos on moist filter paper at a daily alternating 20/30°C (with lights during the 30°C phase); [vi) where necessary, freeing the cotyledons of all seedlings that become trapped in the female gametophyte]; vii) transplanting seedlings to conventional nursery practice. A further 1008 seeds are continuing 'pretreatment' to investigate whether this will increase the proportion of seedlings per viable embryo or better still lead to a much less labour intensive seedling emergence from intact seeds.

Secondary metabolites from endophytic fungi isolated from the Chilean gymnosperm Prumnopitys andina (Lleuque)

Summary Two endophytic fungi isolated from the phloem of the Chilean gymnosperm Prumnopitys andina were cultured in liquid potato-dextrose medium. The secondary metabolites were isolated and identified by spectroscopic methods. The fungus E-3 which could not be identified yielded 4-(2-hydroxyethyl)phenol, p-hydroxybenzaldehyde and the isochromanone mellein. The second fungus, identified as Penicillium janczewskii K.M. Zalessky yielded peniprequinolone and gliovictin, reported for the first time for this species. This is the first report on secondary metabolites produced by endophytic fungi from Chilean gymnosperms.

Comparative anatomy and morphology of fertile complexes of Prumnopitys and Afrocarpus species (Podocarpaceae) as revealed by histology and NMR imaging, and their relevance to systematics

Fertile complexes (individual reproductive units of ovulate cones) of three Prumnopitys species and Afrocarpus falcatus (Podocarpaceae) were subjected to histological examination and non-destructive NMR imaging. The latter technique allowed the display, frame-by-frame analysis and electronic ‘dissection’ of internal structures such as the number and courses of vascular traces and resin canals and their morphology. Characters of these internal structures distinguished all three Prumnopitys species from each other and thus were shown to be taxonomically diagnostic. Fertile complexes of Prumnopitys andina and P. taxifolia were most similar, possessing simple vascular traces and few unbranched resin canals. Those of P. ferruginea were very different and possessed an interconnected network of resin ducts within the sarcotesta. These findings are congruent with relationships inferred from molecular phylogenetic studies, in which two subclades were recovered within Prumnopitys. The anatomy of the female fertile complexes of Afrocarpus falcatus was very distinct from all Prumnopitys species analysed. Its most distinctive feature was the existence of a complex network of radial vascular strands originating from within the outer layers of the sarcotesta and penetrating the inner layers of the fertile complex. The surface texture and morphology of the sclerotesta of the seed was also unique to each species.

Prumnopitys andina reinstated as the correct name for “Ueuque”, the Chilean conifer recently renamed P. spicata (Podocarpaceae)

SummaryMill, R. R. &amp; Quinn, C. J.: Prumnopitys andina reinstated as the correct name for “lleuque”, the Chilean conifer recently renamed P. spicata (Podocarpaceae). – Taxon 50: 1143–1154. 2001. – ISSN 0040–0262.It is demonstrated that Prumnopitys andina (Poepp. ex Endl.) de Laub. (Podocarpaceae) is the correct name for the Chilean conifer, known locally as “lleuque”, which was recently renamed Prumnopitys spicata (Poepp.) Molloy &amp; Muñoz‐Schick. Podocarpus spicatus R. Br. ex Mirb., a name that applies to the New Zealand species, Prumnopitys taxifolia (Sol. ex D. Don) de Laub, (based on Dacrydium taxifolium Sol. ex D. Don), commonly called “matai” or black pine, is validly published, and makes Pod. spicatus Poepp., upon which Molloy &amp; Muñoz‐Schick based their new combination, illegitimate. Moreover, if Podocarpus L'Hér. ex Pers. is circumscribed broadly to include Prumnopitys Phil., the epithets of two of the three species discussed in this paper must be changed from those used legitimately under Prumnopitys. Pod. spicatus R. Br. ex Mirb. is the only available name for that species (matai) in Podocarpus, because Pod. taxifolius Kunth, applicable to a tropical South American species, Prumnopitys montana (Humb., Bonpl. &amp; Kunth. ex Willd.) de Laub, (known locally as “chaquiro”), antedates Dacrydium taxifolium D. Don, preventing the use of Don's epithet in Podocarpus. Chaquiro, currently called Pr. montana, would become Pod. taxifolius Kunth. Full synonymies of the names for the Chilean and New Zealand species and a limited synonymy for that of the tropical South American taxon are given.

Pattern of glacial—interglacial vegetation in subtropical Chile

Pleistocene vegetation in the Mediterranean climate region of subtropical Chile during >40,000 yr of the last glaciation stands in contrast with vegetation of the past 10,000 yr of the present interglaciation. During the last ice age, open woodland of southern beech (Nothofagus dombeyi and N. obliqua types) and Andean podocarp (Prumnopitys andina) mixed with grasses and composites, was established on unglaciated, low‐lying terrain now occupied by broad sclerophyllous plant communities. This marked vegetation change during a glacial‐interglacial cycle, inferred from pollen contained in a core from Laguna de Tagua Tagua (34°30'S), suggests a pattern applicable to the vegetational setting during repeated cycles throughout the Quaternary. Ice‐age vegetation can be accounted for by year‐long domination of the polar maritime air mass at lower, middle latitudes, unlike modern interglacial type plant formations, which are regulated by seasonal interaction between subtropical and polar maritime air. Glacial‐interg...

Ice age vegetation and climate of subtropical Chile

Vegetation and climate of subtropical Chile over the past > 50,000 yr are reconstructed from pollen, spores, and other microfossils contained in a 10.7-m section of lacustrine deposits of Laguna de Tagua Tagua (34°30′ S, 71°10′W). Controlled by 14 radiocarbon age determinations, five pollen assemblages covering stratigraphic zones in the section represent plants on the upland and species inhabiting the lake basin. Surface pollen spectra from 58 stations (approximately 30–40°S) form an adjunct for interpreting past vegetation and climate from the fossil record. Temperature, semi-humid woodland of southern beech ( Nothofagus dombeyi type) and podocarp ( Prumnopitys andina) was apparently established about Laguna de Tagua Tagua during the Pleistocene. Contrasting existing semi-arid, broad sclerophyllous vegetation, the woodland was extensive about the lake at the time of the last glacial maximum (25,000–14,000 yr B.P.) and earlier (> 43,000–34,000 yr B.P.). Pollen from the families Chenopodiaceae and Amaranthaceae, which characterize intervals of the Pleistocene (centered around 33,000 and >43,000 yr B.P.) and the Holocene, suggests intervening episodes of relative aridity. Lake level fluctuations appear to follow the late Quaternary climatic pattern implied by pollen assemblage data. Water in the lake was relatively high during development of southern beech-podocarp woodland, whereas during intervals of chenopod-amaranth dominance, lake levels were comparatively low. Excess precipitation over evaporation, which during the Pleistocene favored development of woodland of beech and podocarp, is attributed to greater storm frequency. Conditions were apparently governed by strengthening of atmospheric circulation in the belt of southern westerly winds. In the late-glacial, the temperate and more humid, ice age climate with limited seasonality underwent transition to a subtropical, semi-arid, Mediterranean type that identifies the postglacial. Fluctuations in intensity of the southern westerlies, marked by latitudinal movement of the polar front, can account for past vegetation changes at Laguna de Tagua Tagua.