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Greslebin A.G.,Research Center y Extension Forestal Andino Patagonico | Hansen E.M.,Oregon State University
Plant Pathology | Year: 2010

Field observations, isolations and pathogenicity tests were performed on Austrocedrus chilensis (Cupressaceae) trees to determine the pathogenicity of Phytophthora austrocedrae and its role in the aetiology of the cypress disease mal del ciprés (MDC) in Argentina. It was found that P. austrocedrae is a primary pathogen of A. chilensis. It was isolated from large necrotic lesions in the inner bark, and superficially in the sapwood, at the root collar and stem, in most of the MDC-affected stands surveyed along the range of A. chilensis in Argentina. The main symptom in naturally infected trees was a necrotic lesion extending from killed roots up to 1 m up the tree bole. Seedlings, saplings and adult trees were all susceptible to inoculation with P. austrocedrae. Under favourable experimental conditions (flooding), inoculated seedlings suffered massive mortality in less than a month. The importance of diseases caused by Phytophthora spp. in South American forests is discussed. © 2010 The Authors. Journal compilation © 2010 BSPP. Source

Austrocedrus chilensis is the most important natural conifer in the Patagonian Andes region of southern Argentina where there are 141,000 hectares of mainly pure stands. Fire is the main disturbance in the dynamics of these forests. The objective of the study was to analyze possible differences in chemical, physical and biological soil properties among unburned (NQ), partially burned (PQ) and completely burned (CQ) portions of two A. chilensis stands: one located near El Bolsón city (41° 59' 02'' S-71° 33' 20'' W) and the other one near Trevelin city (43° 12' 57'' S-71° 31' 15'' W). The stands were burned 21 months and five years before running the studies respectively. The following soil properties expected to influence forest recovery were measured: pH, electric conductivity (EC), organic carbon (C), total nitrogen (N), interchangeable potassium (K), calcium (Ca), magnesium (Mg), and nitrogen in the microorganisms (N-BM) in the upper 10 cm of soil. At El Bolsón study the PQ and CQ portions of the stand had higher pH and EC and less C, N, Mg and N-BM than the NQ portion. These changes may be related to the combustion of the organic matter. These differences were not registered at the Trevelin study; I speculate that at this site soil nutrient content could have been recovered because much more time elapsed between the occurrence of the fire and the installation of the study. It is desirable that after a forest fire the vegetation get reestablished as soon as possible to prevent nutrient loss and hasten the recovery of soils characteristics; this can be facilitated by planting A. chilensis. Source

Orellana I.A.,Research Center y Extension Forestal Andino Patagonico | Raffaele E.,CONICET
New Zealand Journal of Forestry Science | Year: 2010

Invasive introduced species are among the most severe threats to biodiversity and the functioning of natural ecosystems. In this study we analysed whether Pseudotsuga menziesii (Mirb.) Franco is an invader species of two common types of native communities (native Austrocedrus chilensis (D.Don) Pic. Serm. & Bizzarri forests and mixed shrublands) of the subantarctic region of Argentina. We determined the density and the age structures of both P. menziesii and A. chilensis regeneration at the edges of P. menziesii plantations adjacent to native forests of A. chilensis and mixed shrublands. The invasion of P. menziesii was recorded in both types of native communities. In A. chilensis forest, the establishment of P. menziesii was significantly higher than in the shrublands. Also, P. menziesii showed a greater spread than A. chilensis inside and outside the plantations. The increased abundance of P. menziesii plantations, in addition to its invasive characteristics could lead to the replacement of native communities at a regional scale in the long or medium term. © 2010 New Zealand Forest Research Institute Limited, trading as Scion. Source

Kuhar F.,Research Center y Extension Forestal Andino Patagonico | Papinutti L.,Laboratorio Of Micologia Experimental
Revista Argentina de Microbiologia | Year: 2014

Ganoderma lucidum (Curtis) P. Karst is a white rot fungus that is able to degrade the lignin component in wood. The ability of two strains of this species to produce the ligninolytic enzyme laccase was assessed. After the evaluation of induction with heavy metals and phenolic compounds, it was found that among the tested substances, copper and ferulic acid are the best laccase inducers. It was also observed that the two types of inducers (phenolic and metallic) produce different electrophoretic patterns of laccase activity. Optimized concentrations of inducers were obtained through a factorial design and the thermal stability of optimized supernatants was studied at a wide range of acidic pH. We found that the enzyme is more thermostable at higher pH values. © 2013 Asociación Argentina de Microbiología. Published by Elsevier España, S.L. All rights reserved. Source

In Patagonia Douglas-fir is grown to produce high quality timber; thus plantations should be pruned. To prune a stand, the proportion of green crown to be removed (pruning severity) and the number of lifts should be defined. The objectives of this research were to quantify the effect of pruning severity on tree growth and to select indicator variables to determine when to carry out pruning lifts. To achieve the first objective a trial was established on low, medium and highly productive sites. Pruning severities applied were heavy (65 % of the total tree height), intermediate (50 %), light (25 %) and control trees (no pruning). To accomplish the second objective the association between five easy to measure variables (diameter at breast height (DBH), total height, diameter over stubs height, pruning height, maximum diameter over stubs of previous pruning) and maximum diameter over stubs (DOS) was studied on 656 trees. Removing more than 25 % of the green crown progressively diminished subsequent tree growth. On highly productive sites, medium to high pruning severity did not reduce diameter growth as much as it did on low quality site, when carrying out second and third lifts. Diameter at breast height (DBH), and DBH along with previous lift height, was the more highly correlated variable with a maximum diameter over stubs. Source

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