Soil properties and Austrocedrus chilensis forest decline in Central Patagonia, Argentina

Austrocedrus chilensis forests in Argentina suffer a widespread mortality, locally known as `mal del ciprés', whose causes remain unknown. `Mal del ciprés' occurs throughout the cypress range in Argentina, being Río Grande Valley, in Central Patagonian Andes, an area where the disease has notoriously increased its extension and importance in the last years. The purpose of this work was to characterize Río Grande Valley soils where declining cypress stands develop and to determine what soil properties are associated with the disease. Four sampling sites with pure cypress forests expressing `mal del ciprés' were selected. In each of them, 3 declining and 3 asymptomatic plots were established and were characterized by edaphic features. Selected morphological, physical and chemical soil properties were related to the occurrence of the decline by means of analysis of variance. The cypress forest developed in a wide range of soils with different parent materials: glacifluvial, alluvial, volcanic with a glacifluvial discontinuity, volcanic on an andesitic substratum, and soils derived from andesite alteration. All the soils presented dark superficial horizons, rich in organic matter and with granular structure. Cypress growing on volcanic soils with a glacifluvial discontinuity presented symptoms of decline in areas where the discontinuity, and therefore the clayey horizon and the redoximorphic features, were close to the surface. In soils derived from andesite alteration, the declining forest was also present on shallow soils with redoximorphic features near the surface. In volcanic soils with a lithological discontinuity of andesite, the decline was restricted to areas near a water stream. In alluvial soils, declining trees appeared related with the flood plain of the river; healthy forest stands developed on higher lands, where soils were well drained. Glacifluvial soils, presenting clayey textures and great difficulties for rooting, were the soils submitted to the worst drainage conditions. In these soils, the decline presented a random pattern of distribution, suggesting that the whole area is prone to develop the decline. Results showed cypress capacity to inhabit different soils; however microsite features related to poor drainage (i.e., low slope, nearness to water streams, the presence of clay and redoximorphic features near to the surface) determined a higher risk of disease occurrence.     

Runoff and erosion from volcanic soils affected by fire: the case of Austrocedrus chilensis forests in Patagonia, Argentina

Aims

We characterized the runoff and erosion from a volcanic soil in an Austrocedrus chilensis forest affected by a wildfire, and we evaluated the effects of a mitigation treatment.

Methods

Rainfall simulations were performed in the unburned and burned forest, with and without vegetation cover, and under a mitigation treatment.

Results

After the wildfire, the mean infiltration rate decreased from 100 mm?h^?1 in unburned soils to 51 and 64 mm?h^?1 in the burned with and without litter and vegetation cover, respectively. The fast establishment of bryophytes accelerated the recovery of soil stability. Sediment production was negligible in the control plots (4.4 g?m^?2); meanwhile in the burned plots, it was 118.7 g?m^?2 and increased to 1026.1 g?m^?2 in the burned and bare plots. Total C and N losses in the control plots were negligible, while in the burned and bare plots the organic C and total N removed were 98.25 and 1.64 g?m², respectively. The effect of mitigation treatment was efficient in reducing the runoff, but it did not affect the sediment production.

Conclusions

These fertile volcanic soils promoted the recovery of vegetation in a short time after the wildfire, diminishing the risk of erosion.     

Austrocedrus chilensis growth decline in relation to drought events in northern Patagonia, Argentina

The significant mortality of the Austrocedrus chilensis (D. Don) Pic. Serm. et Bizarri forests, locally known as “Mal del Ciprés”, has been reported since 1945 for most sites across its distribution in Argentina. However, the cause of this decline is still a topic of discussion. In this study, radial growth patterns from symptomatic and asymptomatic A. chilensis trees were analyzed to determine the influence of drought events on tree growth. Fifty pairs of symptomatic and asymptomatic trees with similar DBH, competition, and microsite conditions were cored at five pure A. chilensis stands near El Bolsón, Río Negro, Argentina. A reference chronology from nonaffected trees was used to cross-date all cores and to determine the relationship between A. chilensis radial growth and climate. The growth of A. chilensis is favored by above average precipitation in late spring–early summer (November and December). A strong relationship was also observed between radial growth patterns and the Palmer drought severity index, a measure of the regional water deficit. Significant differences in growth patterns were recorded between symptomatic and asymptomatic trees. Following extreme drought events, the growth of symptomatic trees is consistently lower than in asymptomatic trees. Based on the larger number of droughts recorded during the past decades and on future climatic predictions suggesting increasing trends in the frequency and intensity of drought events in northern Patagonia, a gradual increase in the number of trees affected by “Mal del Ciprés” along the twenty-first century is likely expected.     

Nothofagus dombeyi regeneration in declining Austrocedrus chilensis forests: Effects of overstory mortality and climatic events

This research examines the regeneration dynamics of Nothofagus dombeyi and Austrocedrus chilensis in A. chilensis-dominated forests growing near the eastern limit of N. dombeyi where precipitation is limiting. In these forests the widespread decline and mortality of overstory A. chilensis trees, known as ‘mal del ciprés’ (cypress sickness), generates large canopy gaps in which new individuals establish. Our objective was to study the population dynamics of N. dombeyi and A. chilensis in these forests to investigate the influences of overstory tree death and climatic variation on establishment. We sampled 6 symptomatic A. chilensis stands and used dendrochronological techniques to reconstruct basal area development and regeneration establishment over time. Bivariate event analysis was performed to examine the temporal relationships between tree establishment and mortality events and climatic variation. Overstory A. chilensis trees established as post-fire cohorts, with subsequent establishment of A. chilensis and N. dombeyi during the past 50–60 years. Regeneration in the past two decades was primarily N. dombeyi. The establishment of both A. chilensis and N. dombeyi was synchronous with overstory tree mortality events, but it was more consistent among stands and prolonged for N. dombeyi. Establishment of A. chilensis was not associated with climatic events but N. dombeyi establishment was synchronous with droughts, possibly related to climate-driven mortality creating canopy gaps or reducing competition within gaps. We have demonstrated that N. dombeyi has the ability to establish in post-fire A. chilensis-dominated forests resulting in mixed-species, uneven-aged forests. The ongoing increase in the abundance of N. dombeyi relative to A. chilensis represents a shift in composition and increased complexity in stand structure driven by ‘mal del ciprés’ and climatic variation.     

Monoterpene emissions from three Nothofagus species in Patagonia,Argentina

Abstract

Isoprenoid emissions have key roles in plant biology and plant interactions with the environment. Global emission inventories of isoprenoid emissions still lack information from a large number species, especially from South American vegetation other than the rainforest ecosystem. A study was conducted to identify the basal emission of isoprenoid under field conditions from three Nothofagus species. The three Nothofagus species were characterized as strong monoterpene emitters while the emission of isoprene was undetectable. The two deciduous species, N. pumilio and N. antarctica, had similar photosynthetic parameters, but monoterpene emission rate and, consequently, the fraction of photosynthetic carbon re-emitted in the atmosphere as monoterpenes, were more than three-fold higher in N. pumilio than in N. Antarctica. The evergreen species N. dombeyi showed intermediate values of both monoterpene emission rate and fraction of photosynthetic carbon re-emitted. The monoterpene emission spectrum was very similar among the three Nothofagus species screened, but clearly different from the spectrum reported in other monoterpene-emitting species of the Fagaceae family. The importance of these findings for atmospheric chemistry and phylogenic evolution are discussed.     

Heavy metal and other trace elements in native mussel Diplodon chilensis from Nothern Patagonia Lakes, Argentina

Native mussels, Diplodon chilensis, were sampled from four lakes in Nahuel Huapi National Park, Northern Patagonia, Argentina in order to evaluate heavy-metal distribution in the region and to assess the contribution of this compartment of the trophic web to their circulation in the food chain. The concentration of potential pollutants Ag, As, Cr, Hg, Sb, and Se, and other nine elements of interest (Ba, Br, Ca, Co, Cs, Fe, Na, Sr, and Zn) were determined in Diplodon chilensis pooled samples. Digestive glands were analyzed separately from soft tissues. Geological tracers Sc, Ta, Th, and rare earth elements were also determined in order to discriminate lithophile contributions. Elemental concentrations of Ba, Br, Fe, Sr, Se, and Zn in total soft tissues samples do not show significant differences among sampling sites. Arsenic and Cr contents in total soft tissues and digestive gland pooled samples are higher in sampling points close to zones with human settlements. Silver contents in samples collected in Lake Nahuel Huapi were higher than in the other lakes studied, and up to 50-fold higher than the sample collected in Lake Traful, considered as the reference. Mercury highest concentration values measured in total soft tissues pooled samples from lakes Nahuel Huapi and Moreno were found to be similar to those observed in other reported Hg contamination situations, and they are three to five times higher than those of the reference samples collected in Lake Traful.     

New species of dictyostelids from Patagonia and Tierra del Fuego, Argentina

In late Jan and early Feb 2005 samples for isolation of dictyostelid cellular slime molds (dictyostelids) were collected in five different provinces and from six national parks (all located 39-55°S) in Patagonia and Tierra del Fuego, Argentina. Southern beech (Nothofagus) forests represented the primary vegetation type investigated, but some samples were obtained from Patagonian steppe, alpine meadows, Valdivian temperate rainforests and coniferous forests dominated by Araucaria, Austrocedrus and Fitzroya. Among the dictyostelids isolated from the samples we collected were seven species new to science. These species (Dictyostelium austroandinum, D. chordatum, D. fasciculoideum, D. gargantuum, D. leptosomopsis, D. valdivianum and Polysphondylium patagonicum) are described herein on the basis of both morphology and molecular (SSU rDNA) data. One of the new species, D. gargantuum, is one of the largest representatives of the group reported to date. Another unusual species, D. chordatum, produces long interwoven sorocarps that do not appear to respond to a spacing gas similar to the condition first noted in D. implicatum.     

Phytophthora polonica, a new species isolated from declining Alnus glutinosa stands in Poland

In a survey of Phytophthora associated with alder decline in Poland, several isolates of a homothallic Phytophthora sp., which could not be assigned to other taxa including Phytophthora alni subspecies, were consistently recovered from rhizosphere soil samples. Their morphology and pathogenicity, as well as sequence data for three nuclear regions (internal transcribed spacer rDNA, elongation factor-1alpha and beta-tubulin) and a coding mitochondrial DNA region (nadh1), were examined. The new Phytophthora species is characterized by the moderate to slow growth rate of its colony in carrot agar at 20 degrees C, high optimal (c. 30 degrees C) and maximum (c. 38 degrees C) growth temperatures, formation of catenulate, often lateral, hyphal swellings, large chlamydospores in agar media and in soil extract, persistent, ovoid to ellipsoid nonpapillate sporangia and large oogonia with paragynous and sometimes amphigynous antheridia. Phytophthora polonica was slightly pathogenic to alder twigs and not pathogenic to trunks of several tree species. In a phylogenetic analysis using either Bayesian inference or maximum likelihood methods, P. polonica falls in clade 8 'sensu Kroon et al. (2004)' of Phytophthora.     

Eimeriid oocysts from archaeological samples in Patagonia, Argentina

Oocysts attributable to E. macusaniensis Guerrero et al. 1971, were found in coprolites and in archaeological sediments dating to the Holocene of Patagonia, Argentina. By means of a non-parametric regression using a generalized additive model, a significant relationship was found between the size of the oocysts and their antiquity. Specifically, a reduction in oocyst size over time was discovered, probably due to a parasite response to host replacement, to an extinct eimeriid species common during the Pliestocene-Holocene transition, or to environmental changes known for the Holocene. Explanations regarding coevolution between parasites, hosts and paleoenvironmental conditions are discussed herein.     

Lower Permian bivalves from central Patagonia, Argentina

The earliest Permian faunal successions of central Patagonia show compositional changes that probably reflected the environmental warming at the end of the Gondwana glaciations. Bivalves of Asselian to probably Early Tastubian age are described. A new genus,Sueroa, is proposed to reunite a previously known species and a new species,Sueroa andreisi n. sp. Another five new species:Parallelodon? quichaurensis n. sp.,Heteropecten cortignasi n. sp.,Etheripecten saraviae n. sp.,Streblopteria montgomeryi n. sp. andPraeundulomya moreli n. sp. are described. Two previously known species:Malimania patagoniensis (González) andEuchondria sabattiniae González are revised and new occurrences are reported. A further eleven species are described, but they are left in open nomenclature being because they are insufficiently known; these are:Phestia? n. sp.,Modiolus sp.,Palaeoneilo sp.,Stutchburia sp.,Schizodus sp.,Vacunella? sp.,Edmondia sp.,Myonia? n. sp.,Myonia? sp. andPachymyonia? n. sp.     

Development of highly polymorphic tetranucleotide microsatellite markers in Austrocedrus chilensis

An enriched genomic library was constructed and 9 novel polymorphic tetranucleotide microsatellite markers developed for Austrocedrus chilensis, the most economically important native conifer in the Andean Patagonian region. Polymorphism was investigated for these markers in 48 individuals from two populations. Numbers of alleles ranged from 3 to 19 and levels of observed heterozygosity among the 9 loci ranged from 0.32 to 0.95. No locus combinations exhibited linkage disequilibrium. These polymorphic markers will be useful tools for the study of demography and gene flow and more in general for population and conservation genetics of this species.     

Paleoparasitological records in a canid coprolite from Patagonia, Argentina

In this note, organic remains identified as a canid coprolite were examined. The material was dated at 6540 +/- 110 B.P.; it was collected in the Perito Moreno National Park, Santa Cruz, Argentina. Paleoparasitological analysis was performed following standard procedures. Coprolite fragments were rehydrated in a trisodium phosphate aqueous solution and subjected to spontaneous sedimentation for microscope analysis. Eggs of nematodes identified as Trichuris sp., Capillaria sp., Uncinaria sp., and an ascaridid (probably Toxascaris sp.) or spirurids (presumably Physaloptera sp.), plus a cestode (Anoplocephalidae), presumably Moniezia sp., were found.     

Phyllactinia chubutiana: a new species of Erysiphales from Patagonia (Argentina)

Phyllactinia chubutiana, a parasite on leaves of Lycium chilense (Solanaceae) collected in the arid Patagonian steppe, is proposed as a new species. The new combination Ovulariopsis insolita is introduced for its anamorph previously described as Oidium insolitum.     

Notes on Erysiphales (Ascomycetes) from Patagonia, Argentina

Fifteen Erysiphaceous taxa found on 20 host plant species in Patagonia are documented. A new species Oidium maculatae (type host: Viola maculata) is described. Berberis linearifolia, Buddleja globosa, Prosopis alpataco and Viola maculata, are new host plants for Erysiphales. Three new combinations on fungi and host plant species were founded: Erysiphe howeana – Fuchsia magellanica; E. patagoniaca – Nothofagus pumilio and N. antarctica. The genus Sawadaea and the species S. bicornis on Acer negundo and A. pseudoplatanus, are new records for South America. New host plants recorded for Argentina: Consolida ajacis, Galega officinalis and Plantago lanceolata. New host plants recorded for Patagonia: Galium aparine, Melilotus albus, Petunia × hybrida, Potentilla anserina, and Spiraea × bumalda. Oidium longipes is a new record for Argentina and Golovinomyces riedlianus is a new record for Patagonia.     

Nitrogen addition stimulates forest litter decomposition and disrupts species interactions in Patagonia,Argentina

Nitrogen (N) deposition and biodiversity loss are important drivers of global change, with uncertain consequences for carbon (C) and nutrient turnover in terrestrial ecosystems. We evaluated the simultaneous effects of N deposition and plant diversity on litter decomposition within a temperate forest in Patagonia. We identified ‘tree triangles’ created by the intersection of three tree‐canopies that directly controlled micro‐environmental conditions on the forest floor, and combined it with an N addition treatment. Triangles were composed of one or three Nothofagus species (N. dombeyi, N. obliqua or N. nervosa). We placed litterbags containing litter of each of the Nothofagus species and litterbags containing a mixture of the three species within all triangles and assessed mass loss over 2 years. We used a standard litter type in all triangles to independently evaluate triangle effects on decomposition. N addition had strong and positive effects on decomposition with an average 46% increase in the decomposition constant. Litter species significantly differed in their response to N addition; litter with higher lignin content and lower labile C content had larger increase in decomposition due to fertilization. Also, N addition disrupted two types of species interactions that control decomposition. The affinity relation between litter and decomposers, that enhanced decomposition of home litter (‘home‐field advantage’) that was demonstrated to be significant for all three Nothofagus species, disappeared with N addition. Second, N addition modified litter species interactions, transforming neutral effects of litter mixtures to positive, nonadditive effects on mass loss. Finally, N addition stimulated N release from decomposing litter which was modulated by plant species effects. Together, these results suggest that N addition to unpolluted forests increases C loss, contrary to what has been observed for temperate forests in industrialized areas of the world, and that alterations in nutrient pools have effects on species interactions, including the elimination of affinity effects for decomposition.     

Revision of the Proteaceae macrofossil record from Patagonia, Argentina

Proteaceae are restricted to the Southern Hemisphere, and of the seven tribes of the subfamily Grevilleoideae, only three (Macadamieae, Oriteae, and Embothrieae) have living members in Argentina. Megafossil genera of Proteaceae recorded from Patagonia includeLomatia, Embothrium, Orites, andRoupala. In this report, we evaluate and revise fossil Argentine Proteaceae on the basis of type material and new specimens. The new collections come from the Tufolitas Laguna del Hunco (early Eocene, Chubut Province), the Ventana (middle Eocene, Río Negro Province), and the Río Ñirihuau (late Oligocene-early Miocene, Río Negro Province) formations, Patagonia, Argentina. We confirm the presence ofLomatia preferruginea Berry,L. occidentalis (Berry) Frenguelli,L. patagonica Frenguelli,Roupala patagonica Durango de Cabrera et Romero, andOrites bivascularis Romero, Dibbern et Gandolfo. Fossils assigned toEmbothrium precoccineum Berry andE. pregrandiflorum Berry are doubtful, and new material is necessary to confirm the presence of this genus in the fossil record of Patagonia. A putative new fossil species of Proteaceae is presented as Proteaceae gen. et sp. indet. Fossil Proteaceae are compared with modern genera, and an identification key for the fossil leaf species is presented. Doubtful historical records of Proteaceae fossils for the Antarctic Peninsula region and Patagonia are also discussed. Based on this revision, the three tribes of Proteaceae found today in Argentina were already present in Patagonia by the early Eocene, where they probably arrived via the Australia-Antarctica-South America connection.     

Arecaceae Fossil Fruits from the Paleocene of Patagonia,Argentina

We describe fossil fruits collected from outcrops of the Salamanca Fm. (Paleocene, Danian, 63.3–61.9 Ma) at the Estancia Las Violetas locality, Chubut, Argentina that show affinities with members of the Subtribe Attaleinae, Tribe Cocoseae, Subfamily Arecoideae within the Arecaceae. The fossils are preserved as permineralizations, and were examined by longitudinal, tangential and cross-sections, as well as by the application of Computed Tomography Scanning technology (CT Scan). The fruits are ovoid drupes with 3 longitudinal grooves delimiting three valves; displaying apical stigmatic remains and a single apical germination pore. The exocarp and mesocarp are fused and anatomically indistinguishable one from another; they contain longitudinal fibrous bands with brachysclereids. A centrally placed seed occupies the single locule entirely; the seeds are deltoid with a basal hilum and acuminate tip while the endosperm is ruminate. The taxonomic position of the fossils was explored using phylogenetic analyses of molecular sequences combined with morphological data. Along with the suite of morphological characters that points to an affinity with the Subtribe Attaleinae, Tribe Cocoseae, subfamily Arecoideae, the results of the combined phylogenetic analyses confirm the taxonomic placement. This report constitutes the first confirmed record for the Subtribe Attaleinae worldwide and the first record of fossil palm fruits from Argentina.