The Characterization of a Novel PrMADS11 Transcription Factor from Pinus radiata Induced Early in Bent Pine Stem.

A novel MADS-box transcription factor from Pinus radiata D. Don was characterized. PrMADS11 encodes a protein of 165 amino acids for a MADS-box transcription factor belonging to group II, related to the MIKC protein structure. PrMADS11 was differentially expressed in the stems of pine trees in response to 45° inclination at early times (1 h). Arabidopsis thaliana was stably transformed with a 35S::PrMADS11 construct in an effort to identify the putative targets of PrMADS11. A massive transcriptome analysis revealed 947 differentially expressed genes: 498 genes were up-regulated, and 449 genes were down-regulated due to the over-expression of PrMADS11. The gene ontology analysis highlighted a cell wall remodeling function among the differentially expressed genes, suggesting the active participation of cell wall modification required during the response to vertical stem loss. In addition, the phenylpropanoid pathway was also indicated as a PrMADS11 target, displaying a marked increment in the expression of the genes driven to the biosynthesis of monolignols. The EMSA assays confirmed that PrMADS11 interacts with CArG-box sequences. This TF modulates the gene expression of several molecular pathways, including other TFs, as well as the genes involved in cell wall remodeling. The increment in the lignin content and the genes involved in cell wall dynamics could be an indication of the key role of PrMADS11 in the response to trunk inclination.

Potential of Pinus radiata, Eucalyptus globulus and Acacia dealbata for the long-term phytostabilization of copper mine tailings.

Many contaminated tailings throughout the world cause environmental and human-health related problems due to air and water drift. Tailing phytostabilization is a promising solution, but only certain plant species may tolerate and grow in these contaminated areas. We analyzed the chemical properties of a vegetated and unvegetated area in a tailing site in Central Chile. In addition, in the vegetated area we analyzed the metals content of roots, stems, and foliage in 41-years old plantations of Pinus radiata, Acacia dealbata, and Eucalyptus globulus (the only three species that survived from a total of 34 species planted), and determined height (H), and diameter at breast height (DBH). The results indicated that, except for pH, Se, Pb, and organic matter, all components (nutrients and metals) were two- to three- fold lower in the vegetated tailing compared to that of the unvegetated tailing. The analysis of plant tissues indicated that Cu was higher in the roots of P. radiata (2,073 mg kg-1) and lower in the stems of the same species (4.1 mg kg-1). However, the ability to take up and transport Cu to the shoots was higher in A. dealbata and lower in P. radiata (bioaccumulation factor of 0.19 and 0.06, respectively).

Here we present results for the first long-term phytostabilization project of copper mine tailings in Chile. From the 34 native and exotic species established in 1980 in a mine tailing disposal site with 1,000 mg Cu kg⁻¹, only the exotic Pinus radiata, Acacia dealbata and Eucalyptus globulus were able to survive and adapt to the tailing conditions the last 41 years. This corroborates their potential for the future phytostabilization of copper mine wastes.

Natural durability of timber species exposed to xylophagous fungi in southern Durango, Mexico.

Introduction: Wood is a natural resource used for construction and the manufacture of many products. This material is exposed to damage due to biotic and abiotic factors. An important biotic factor is wood-degrading fungi that generate large economic losses. The objectives of this study were to determine the effect of xylophagous fungi (Coniophora puteana and Trametes versicolor) on the natural durability of six timber species in southern Durango, Mexico, and to establish differences between fungal effects on each tree species. Materials and Methods: Samples of Pinus durangensis, P. cooperi, P. strobiformis, Juniperus deppeana, Quercus sideroxyla, and Alnus acuminata were exposed to fungi for 4 months under laboratory conditions according to European Standard EN350-1. Samples of Fagus sylvatica were used as control. Durability was determined as the percentage of wood mass loss for each species. Welch ANOVA tests were performed to establish differences among tree species. Welch t-tests were used to prove loss mass differences between fungi for each tree species. Results: The most resistant species to C. puteana were P. durangensis, J. deppeana, P. cooperi and P. strobiformis, showing mean mass losses lower than 8.08%. The most resistant species to T. versicolor were J. deppeana, P. strobiformis and P. durangensis (mean mass losses lower than 7.39%). Pinus strobiformis and Q. sideroxyla were more susceptible to C. puteana effect; in contrast, P. durangensis and P. cooperi showed more damage due to T. versicolor degradation. Conclusions: Woods of P. durangensis, P. cooperi, P. strobiformis and Juniperus deppeana are well adapted to infection by these xylophagous fungi and are therefore highly recommended for commercial use in southern Durango, Mexico.

Coupled plant traits adapted to wetting/drying cycles of substrates co-define niche multidimensionality.

Theories attempting to explain species coexistence in plant communities have argued in favour of species' capacities to occupy a multidimensional niche with spatial, temporal and biotic axes. We used the concept of hydrological niche segregation to learn how ecological niches are structured both spatially and temporally and whether small scale humidity gradients between adjacent niches are the main factor explaining water partitioning among tree species in a highly water-limited semiarid forest ecosystem. By combining geophysical methods, isotopic ecology, plant ecophysiology and anatomical measurements, we show how coexisting pine and oak species share, use and temporally switch between diverse spatially distinct niches by employing a set of functionally coupled plant traits in response to changing environmental signals. We identified four geospatial niches that turned into nine, when considering the temporal dynamics of the wetting/drying cycles in the substrate and the particular plant species adaptations to garner, transfer, store and use water. Under water scarcity, pine and oak exhibited water use segregation from different niches, yet under maximum drought when oak trees crossed physiological thresholds, niche overlap occurred. The identification of niches and mechanistic understanding of when and how species use them will help unify theories of plant coexistence and competition.

Induction of PrMADS10 on the lower side of bent pine tree stems: potential role in modifying plant cell wall properties and wood anatomy.

The molecular mechanisms underlying inclination responses in trees are unclear. In this study, we identified a MADS-box transcription factor differentially expressed early after inclination in the stems of Pinus radiata D. Don. PrMADS10 has a CDS of 582 bp and encodes a group II MADS-box transcription factor. We measured highest accumulation of this transcript on the lower side of inclined pine stems. In an effort to identify putative targets, we stably transformed Arabidopsis thaliana with a 35S::PrMADS10 construct. Transcriptome analysis revealed 1,219 genes differentially-expressed, with 690 and 529 genes up- and down-regulated respectively, when comparing the transgenic and wild-type. Differentially-expressed genes belong to different biological processes, but were enriched in cell wall remodeling and phenylpropanoid metabolic functions. Interestingly, lignin content was 30% higher in transgenic as compared to wild-type plants consistent with observed changes in gene expression. Differentially expressed transcription factors and phenylpropanoid genes were analyzed using STRING. Several MYB and NAC transcription factors showed interactions with genes of the phenylpropanoid pathway. Together, these results implicate PrMADS10 as a regulatory factor, triggering the expression of other transcription factors and genes involved in the synthesis of lignin.

Evaluation of laccase production by Ganoderma lucidum in submerged and solid-state fermentation using different inducers.

Laccases are multicopper oxidases with high potential for industrial applications. Several basidiomycete fungi are natural producers of this enzyme; however, the optimization of production and selection of inducers for increased productivity coupled with low costs is necessary. Lignocellulosic residues are important lignin sources and potential inducers for laccase production. Pinus taeda, a dominant source of wood-based products, has not been investigated for this purpose yet. The aim of this study was to evaluate the production of laccase by the basidiomycete fungus Ganoderma lucidum in the presence of different inducers in submerged and solid-state fermentation. The results of submerged fermentation in presence of 5 µM CuSO 4 , 2 mM ferulic acid, 0.1 g/L P. taeda sawdust, or 0.05 g/L Kraft lignin indicated that although all the tested inducers promoted increase in laccase activity in specific periods of time, the presence of 2 mM ferulic acid resulted in the highest value of laccase activity (49 U/L). Considering the submerged fermentation, experimental design following the Plackett-Burman method showed that the concentrations of ferulic acid and P. taeda sawdust had a significant influence on the laccase activity. The highest value of 785 U/L of laccase activity on submerged fermentation was obtained on the seventh day of cultivation. Finally, solid-state fermentation cultures in P. taeda using ferulic acid or CuSO 4 as inducers resulted in enzymatic activities of 144.62 and 149.89 U/g, respectively, confirming the potential of this approach for laccase production by G. lucidum.

In seedlings of Pinus radiata, jasmonic acid and auxin are differentially distributed on opposite sides of tilted stems affecting lignin monomer biosynthesis and composition.

Plants respond to the loss of vertical growth re-orientating their affected organs. In trees, this phenomenon has received the scientific attention due to its importance for the forestry industry. Nowadays it is accepted that auxin distribution is involved in the modulation of the tilting response, but how this distribution is controlled is not fully clear. Auxin transporters that determine the spatio-temporal auxin distribution in radiate pine seedlings exposed to 45° of tilting were identified. Additionally, based on indications for an intimate plant hormone crosstalk in this process, IAA and JA contents were evaluated. The experiments revealed that expression of the auxin transporters was down-regulated in the upper half of the tilted stem, while being induced in the lower half. Moreover, transporter-coding genes were first induced at the apical zone of the stem. IAA was consistently redistributed toward the lower half, which is in accordance with the expression profile of the auxin transporters. In contrast, JA was mainly accumulated in the upper half of tilted stems. Finally, lignin content and monomeric composition were analyzed in both sides of stem and along the time course of tilting. As expected, lignin accumulation was higher at the lower half of stem at longer times of tilting. However, the most marked difference was the accumulation of the H-lignin monomer in the lower half, while the G-lignin unit was more dominant in the upper half. Here, we provide detailed insight in the distribution of IAA and JA, affecting the lignin composition during the tilting response in Pinus radiata seedlings.

Conditions Affecting Lingzhi or Reishi Medicinal Mushroom Ganoderma lucidum (Agaricomycetes) Basidiome Quality, Morphogenesis, and Biodegradation of Wood By-products in Argentina.

Solid-state fermentation (SSF) with the medicinal higher Basidiomycete Ganoderma lucidum was studied as a strategy to use pine (Pinus radiata D. Don) and poplar (Populus nigra L.) wood chips and sawdust. Fruiting bodies were produced and the value of the biotransformed substrate was assessed. The highest mushroom yield (63 g dry weight per kilogram of dry substrate) was obtained with poplar sawdust and wood chips. Immersion of the bioreactors was a simple watering method that obtained suitable yields. Two morphological types were induced using 2 different incandescent light intensities. High light irradiation induced the highest valued mushroom morphology (as a whole product). Time course study of substrate biodegradation and mycelial growth dynamics indicated that the trophophase lasted 20 days and presented laccase activity of 0.01-0.03 units · g-1. The activity at idiophase was 10 times higher. Aqueous and alkali extracts, as well as carbohydrase enzyme profile activity, revealed differences in the properties of the residual substrate; some related to the substrate source are considered to be of concern for further use of this pretreated biomass. In view of the results obtained, we propose use of SSF of pine and poplar with G. lucidum to profitably recycle softwood by-products from the timber industry.

Transcriptional and computational study of expansins differentially expressed in response to inclination in radiata pine.

Plants have the ability to reorient their vertical growth when exposed to inclination. This response can be as quick as 2 h in inclined young pine (Pinus radiata D. Don) seedlings, with over accumulation of lignin observed after 9 days s. Several studies have identified expansins involved in cell expansion among other developmental processes in plants. Six putative expansin genes were identified in cDNA libraries isolated from inclined pine stems. A differential transcript abundance was observed by qPCR analysis over a time course of inclination. Five genes changed their transcript accumulation in both stem sides in a spatial and temporal manner compared with non-inclined stem. To compare these expansin genes, and to suggest a possible mechanism of action at molecular level, the structures of the predicted proteins were built by comparative modeling methodology. An open groove on the surface of the proteins composed of conserved zresidues was observed. Using a cellulose polymer as ligand the protein-ligand interaction was evaluated, with the results showing differences in the protein-ligand interaction mode. Differences in the binding energy interaction can be explained by changes in some residues that generate differences in electrostatic surface in the open groove region, supporting the participation of six members of multifamily proteins in this specific process. The data suggests participation of different expansin proteins in the dissembling and remodeling of the complex cell wall matrix during the reorientation response to inclination.

Genetic and correlation analysis of oleoresin chemical components in slash pine.

This is the first comprehensive study of the genetic analysis of the majority of oleoresin components of slash pine (Pinus elliottii). Pine oleoresin, the resin secreted from the pine tree, is a raw material widely used in industrial products. The objective of this study was to explore the genetic variation and correlation between the major oleoresin components of 50 open pollinated families of slash pine. The individual narrow-sense heritability of the 23 oleoresin components and genetic correlations between them were estimated using the residual maximum likelihood in the flexible mixed modeling program, ASReml-R. A high heritability of 0.424 was observed for ß-pinene. Moderate levels of heritability were estimated for ß-phellandrene, methyl abietate, estragole, 15-hydroxy-dehydroabietic acid, and isopimaric acid methyl ester at 0.303, 0.294, 0.27, 0.258, and 0.2, respectively. The heritabilities for pimaric acid methyl ester, abieta-8, 13-diene-18-oic acid methyl ester, sandaracopimaric acid, methyl ester, and camphene were relatively low and ranged from 0.11 to 0.17. Many negative genetic correlations were observed as unfavorable while the corresponding phenotypic correlations presented no significant relationships or positive phenotypic correlations. However, the heritabilities and genetic correlations showed that single or multiple component selections and improvement, directly or indirectly, were effective. We postulate that genetic parameters estimated in this study will work as a reference in breeding programs of oleoresin components, especially in slash pine.

Remote sensing estimation of isoprene and monoterpene emissions generated by natural vegetation in Monterrey, Mexico.

In addition to oxygen, hydrocarbons are the most reactive chemical compounds produced by plants into the atmosphere. These compounds are part of the family of volatile organic compounds (VOCs) and are discharged in a great variety of forms. Among the VOCs produced by natural sources such as vegetation, the most studied until today are the isoprene and monoterpene. These substances can play an important role in the chemical balance of the atmosphere of a region. In this project, we develop a methodology to estimate the natural (vegetation) emission of isoprene and monoterpenes and applied it to the Monterrey Metropolitan Area, Mexico and its surrounding areas. Landsat-TM data was used to identify the dominant vegetation communities and field work to determine the foliage biomass density of key species. The studied communities were submontane scrub, oak, and pine forests and a combination of both. We carried out the estimation of emissions for isoprene and monoterpenes compounds in the different plant communities, with two different criteria: (1) taking into account the average foliage biomass density obtained from the various sample point in each vegetation community, and (2) using the foliage biomass density obtained for each transect, associated to an individual spectral class within a particular vegetation type. With this information, we obtained emission maps for each case. The results show that the main producers of isoprene are the communities that include species of the genus Quercus, located mainly on the Sierra Madre Oriental and Sierra de Picachos, with average isoprene emissions of 314.6 ton/day and 207.3 ton/day for the two methods utilized. The higher estimates of monoterpenes were found in the submontane scrub areas distributed along the valley of the metropolitan zone, with an estimated average emissions of 47.1 ton/day and 181.4 tons for the two methods respectively.

A Modified Protocol for High-Quality RNA Extraction from Oleoresin-Producing Adult Pines.

RNA extraction resulting in good yields and quality is a fundamental step for the analyses of transcriptomes through high-throughput sequencing technologies, microarray, and also northern blots, RT-PCR, and RTqPCR. Even though many specific protocols designed for plants with high content of secondary metabolites have been developed, these are often expensive, time consuming, and not suitable for a wide range of tissues. Here we present a modification of the method previously described using the commercially available Concert™ Plant RNA Reagent (Invitrogen) buffer for field-grown adult pine trees with high oleoresin content.

Cloning of three genes involved in the flavonoid metabolic pathway and their expression during insect resistance in Pinus massoniana Lamb.

Pinus massoniana Lamb. is an important timber and turpentine-producing tree species in China. Dendrolimus punctatus and Dasychira axutha are leaf-eating pests that have harmful effects on P. massoniana production. Few studies have focused on the molecular mechanisms underlying pest resistance in P. massoniana. Based on sequencing analysis of the transcriptomes of insect-resistant P. massoniana, three key genes involved in the flavonoid metabolic pathway were identified in the present study (PmF3H, PmF3'5'H, and PmC4H). Structural domain analysis showed that the PmF3H gene contains typical binding sites for the 2OG-Fe (II) oxygenase superfamily, while PmF3'5'H and PmC4H both contain the cytochrome P450 structural domain, which is specific for P450 enzymes. Phylogenetic analysis showed that each of the three P. massoniana genes, and the homologous genes in gymnosperms, clustered into a group. Expression of these three genes was highest in the stems, and was higher in the insect-resistant P. massoniana varieties than in the controls. The extent of the increased expression in the insect-resistant P. massoniana varieties indicated that these three genes are involved in defense mechanisms against pests in this species. In the insect-resistant varieties, rapid induction of PmF3H increased the levels of PmF3'5'H and PmC4H expression. The enhanced anti-pest capability of the insect-resistant varieties could be related to temperature and humidity. In addition, these results suggest that these three genes maycontribute to the change in flower color during female cone development.

Comparison of orthologous cytochrome P450 genes relative expression patterns in the bark beetles Dendroctonus rhizophagus and Dendroctonus valens (Curculionidae: Scolytinae) during host colonization.

Bark beetles of the genus Dendroctonus are important components of coniferous forests. During host colonization, they must overcome the chemical defences of their host trees, which are metabolized by cytochrome P450 (CYP or P450) enzymes to compounds that are readily excreted. In this study, we report the relative expression (quantitative real-time PCR) of four orthologous cytochrome P450 genes (CYP6BW5, CYP6DG1, CYP6DJ2 and CYP9Z20) in Dendroctonus rhizophagus and Dendroctonus valens forced to attack host trees at 8 and 24 h following forced attack and in four stages during natural colonization [solitary females boring the bark (T1); both male and female members of couples before oviposition (T2); both male and female members of couples during oviposition (T3), and solitary females inside the gallery containing eggs (T4)]. For both species gene expression was different compared with that observed in insects exposed to single monoterpenes in the laboratory, and the expression patterns were significantly different amongst species, sex, gut region and exposure time or natural colonization stage. The induction of genes (CYP6BW5v1, CYP6DJ2v1 and CYP9Z20v1 from D. rhizophagus, as well as CYP6DG1v3 from D. valens) correlated with colonization stage as well as with the increase in oxygenated monoterpenes in the gut of both species throughout the colonization of the host. Our results point to different functions of these orthologous genes in both species.

Control of resin production in Araucaria angustifolia, an ancient South American conifer.

Araucaria angustifolia is an ancient slow-growing conifer that characterises parts of the Southern Atlantic Forest biome, currently listed as a critically endangered species. The species also produces bark resin, although the factors controlling its resinosis are largely unknown. To better understand this defence-related process, we examined the resin exudation response of A. angustifolia upon treatment with well-known chemical stimulators used in fast-growing conifers producing both bark and wood resin, such as Pinus elliottii. The initial hypothesis was that A. angustifolia would display significant differences in the regulation of resinosis. The effect of Ethrel(®) (ET - ethylene precursor), salicylic acid (SA), jasmonic acid (JA), sulphuric acid (SuA) and sodium nitroprusside (SNP - nitric oxide donor) on resin yield and composition in young plants of A. angustifolia was examined. In at least one of the concentrations tested, and frequently in more than one, an aqueous glycerol solution applied on fresh wound sites of the stem with one or more of the adjuvants examined promoted an increase in resin yield, as well as monoterpene concentration (α-pinene, ß-pinene, camphene and limonene). Higher yields and longer exudation periods were observed with JA and ET, another feature shared with Pinus resinosis. The results suggest that resinosis control is similar in Araucaria and Pinus. In addition, A. angustifolia resin may be a relevant source of valuable terpene chemicals, whose production may be increased by using stimulating pastes containing the identified adjuvants.

Proteomic analysis during ontogenesis of secondary xylem in maritime pine.

Secondary xylem (wood) is formed through an intricate biological process that results in a highly variable final product. Studies have focused on understanding the molecular events for wood formation in conifers. In this process environmental, ontogenic and genetic factors influence variation in wood characteristics, including anatomical, chemical and physical properties. The main objective of this study was to analyse the ageing (ontogenic) effect on protein accumulation in wood-forming tissues along a cambial age (CA) gradient, ranging from juvenile wood (JW) sampled at the top of the tree, to mature wood (MW) sampled at the bottom of the tree. A total of 62 proteins whose accumulation varied by at least 1.5-fold according to CA were selected and identified by ESI-MS/MS; 30 of these were more abundant in MW and 32 were more abundant in JW. Consistent with earlier findings, our results show that JW is a tissue characterized by a high energy demand with the accumulation of gene products involved in energy, protein fate and cellular transport, while proteins identified in MW (heat shock response, oxygen and radical detoxification, and the S-adenosyl methionine cycle) support the idea that this tissue undergoes extended cell-wall thickening and a delay of programmed cell death.

Similar variation in carbon storage between deciduous and evergreen treeline species across elevational gradients.

BACKGROUND AND AIMS: The most plausible explanation for treeline formation so far is provided by the growth limitation hypothesis (GLH), which proposes that carbon sinks are more restricted by low temperatures than by carbon sources. Evidence supporting the GLH has been strong in evergreen, but less and weaker in deciduous treeline species. Here a test is made of the GLH in deciduous-evergreen mixed species forests across elevational gradients, with the hypothesis that deciduous treeline species show a different carbon storage trend from that shown by evergreen species across elevations. METHODS: Tree growth and concentrations of non-structural carbohydrates (NSCs) in foliage, branch sapwood and stem sapwood tissues were measured at four elevations in six deciduous-evergreen treeline ecotones (including treeline) in the southern Andes of Chile (40°S, Nothofagus pumilio and Nothofagus betuloides; 46°S, Nothofagus pumilio and Pinus sylvestris) and in the Swiss Alps (46°N, Larix decidua and Pinus cembra). KEY RESULTS: Tree growth (basal area increment) decreased with elevation for all species. Regardless of foliar habit, NSCs did not deplete across elevations, indicating no shortage of carbon storage in any of the investigated tissues. Rather, NSCs increased significantly with elevation in leaves (P < 0·001) and branch sapwood (P = 0·012) tissues. Deciduous species showed significantly higher NSCs than evergreens for all tissues; on average, the former had 11 % (leaves), 158 % (branch) and 103 % (sapwood) significantly (P < 0·001) higher NSCs than the latter. Finally, deciduous species had higher NSC (particularly starch) increases with elevation than evergreens for stem sapwood, but the opposite was true for leaves and branch sapwood. CONCLUSIONS: Considering the observed decrease in tree growth and increase in NSCs with elevation, it is concluded that both deciduous and evergreen treeline species are sink limited when faced with decreasing temperatures. Despite the overall higher requirements of deciduous tree species for carbon storage, no indication was found of carbon limitation in deciduous species in the alpine treeline ecotone.

Accumulation of aluminium and physiological status of tree foliage in the vicinity of a large aluminium smelter.

A pollution gradient was observed in tree foliage sampled in the vicinity of a large aluminium production facility in Patagonia (Argentina). Leaves of Eucalyptus rostrata, and Populus hybridus and different needle ages of Pinus spec. were collected and concentrations of aluminium (Al) and sulphur (S) as well as physiological parameters (chlorophyll and lipid oxidation products) were analyzed. Al and S concentrations indicate a steep pollution gradient in the study showing a relationship with the physiological parameters in particular membrane lipid oxidation products. The present study confirms that aluminium smelting results in high Al and sulphur deposition in the study area, and therefore further studies should be carried out taking into account potentially adverse effects of these compounds on human and ecosystem health.

Electrophysiological and behavioral responses of the bark beetle Dendroctonus rhizophagus to volatiles from host pines and conspecifics.

The bark beetle Dendroctonus rhizophagus is endemic to northwestern Mexico where it kills immature pines < 3 m tall. We report the first investigation of the chemical ecology of this pest of forest regeneration. We used GC-EAD to assess olfactory sensitivity of this species to volatile compounds from: resin of a major host, Pinus arizonica; mid/hindguts of single, gallery-initiating females; and mate-paired males within galleries of attacked host trees in the field. Antennae of both sexes responded to monoterpenes α-pinene, ß-pinene and 3-carene as well as to the beetle-derived oxygenated monoterpenes fenchyl alcohol, myrtenal, cis-verbenol, trans-verbenol, verbenone, and myrtenol. These monoterpenes were quantified from pre-emerged D. rhizophagus adults forced to attack host tissue in the laboratory, and from individuals dissected from naturally-attacked hosts at different stages of colonization. In both bioassays, myrtenol and trans-verbenol were the most abundant volatiles, and trans-verbenol was the only one produced in significantly greater quantities by females than males in a naturally-colonized host. Two field experiments were performed to evaluate behavioral responses of D. rhizophagus to antennally-active monoterpenes. Results show that 3-carene was significantly attractive either alone or in a ternary (1:1:1) combination with α-pinene and ß-pinene, whereas neither α-pinene nor ß-pinene alone were attractive. None of the beetle-associated oxygenated monoterpenes enhanced the attractiveness of the ternary mixture of monoterpenes, while verbenone either alone or combined with the other five oxygenated terpenes reduced D. rhizophagus attraction to the ternary mixture. The results suggest that attraction of D. rhizophagus to the host tree P. arizonica is mediated especially by 3-carene. There was no conclusive evidence for an aggregation or sex attractant pheromone.

Ciclos biogeoquímicos en bosques naturales y plantaciones de coníferas en ecosistemas de alta montaña de Colombia

Biogeochemical cycles in natural forest and conifer plantations in the high mountains of Colombia. Plant litter production and decomposition are two important processes in forest ecosystems, since they provide the main organic matter input to soil and regulate nutrient cycling. With the aim to study these processes, litterfall, standing litter and nutrient return were studied for three years in an oak forest (Quercus humboldtii), pine (Pinus patula) and cypress (Cupressus lusitanica) plantations, located in highlands of the Central Cordillera of Colombia. Evaluation methods included: fine litter collection at fortnightly intervals using litter traps; the litter layer samples at the end of each sampling year and chemical analyses of both litterfall and standing litter. Fine litter fall observed was similar in oak forest (7.5Mg ha/y) and in pine (7.8Mg ha/y), but very low in cypress (3.5Mg ha/y). Litter standing was 1.76, 1.73 and 1.3Mg ha/y in oak, pine and cypress, respectively. The mean residence time of the standing litter was of 3.3 years for cypress, 2.1 years for pine and 1.8 years for oak forests. In contrast, the total amount of retained elements (N, P, S, Ca, Mg, K, Cu, Fe, Mn and Zn) in the standing litter was higher in pine (115kg/ha), followed by oak (78kg/ha) and cypress (24kg/ha). Oak forests showed the lowest mean residence time of nutrients and the highest nutrients return to the soil as a consequence of a faster decomposition. Thus, a higher nutrient supply to soils from oaks than from tree plantations, seems to be an ecological advantage for recovering and maintaining the main ecosystem functioning features, which needs to be taken into account in restoration programs in this highly degraded Andean mountains. Rev. Biol. Trop. 59 (4): 1883-1894. Epub 2011 December 01.

La caída y descomposición de hojarasca representan los principales ingresos de materia orgánica y nutrientes a los ecosistemas forestales. Se estudiaron la caída y acumulación de hojarasca fina y el retorno de nutrientes, en un robledal (Quercus humboldtii) y en plantaciones de pino (Pinus patula) y ciprés (Cupressus lusitanica) en tierras altas de Colombia. La caída de hojarasca fina fue similar entre el robledal (7.5Mg/ha.a) y el pinar (7.8Mg/ha.a), y muy inferior en el cipresal (3.5Mg/ha.a). El mantillo representó 1.76, 1.73 y 1.3Mg/ha.a en el robledal, pinar y cipresal, respectivamente. El tiempo medio de residencia (TMR) del mantillo siguió la secuencia: cipresal (3.3 años)>pinar (2.1 años)>robledal (1.8 años). La cantidad de nutrientes retenidos en el mantillo siguió la secuencia: pinar (115kg/ ha)>robledal (78kg/ha)>cipresal (24kg/ha). Los menores TMR de nutrientes se presentaron para la hojarasca foliar del robledal, en su mayoría inferiores a 1.0 años. En términos de la función ecosistémica en el robledal los procesos estudiados son muy superiores vía provisión de nutrientes al suelo y regulación de los ciclos biogeoquímicos, aspectos que deben ser considerados previa implementación de programas de repoblamiento forestal.