Hypericum Laricifolium Research Articles

Effectiveness of a novel experimental herbal toothpaste against bacterial consortium associated with dental caries.

To evaluate the effectiveness of an experimental toothpaste based on Hypericum laricifolium Juss. essential oil against a bacterial consortium associated with dental caries. The antibacterial activity of the essential oil was evaluated by the disk diffusion and microdilution tests against Streptococcus mutans, Streptococcus sanguinis and Streptococcus salivarius. Petri dishes were incubated at 37°C for 24 h. An experimental toothpaste was prepared at a concentration of 201.76 mg/mL. The antibacterial activity of the experimental and six commercial toothpastes were evaluated by agar well-diffusion method. Petri dishes were inoculated with a bacterial consortium prepared with the three strains. 80 mg of the toothpastes were placed in the wells and the Petri dishes were incubated at 37°C for 24 h. The inhibition zones were measured with a digital compass. The differences between the pastas were evaluated with the one-way ANOVA test, with a 5% level of significance. The essential oil was more effective than 0.12% chlorhexidine in inhibiting the growth of S. mutans (29.02±1.74 mm) and S. sanguinis (21.92±3.43 mm), being more moderate for S. salivarius (17.66±1.11 mm) . In MBC tests, the EO showed complete inhibition of the growth of S. mutans at a concentration of 5% (50.44 mg/mL), 10% (100.88 mg/mL) for S. sanguinis and 2.5% (25.22 mg/mL) for S. salivarius. The experimental toothpaste was effective in inhibiting the growth of the bacterial consortium (31.88±66 mm), having a similar performance to Total Dent, Colgate Total 12, Kolynos® Herbal and Colgate® Herbal (p> 0.05). The development of an experimental paste based on H. laricifolium Juss. essential oil (0.28% v/v) showed an important antibacterial activity similar to commercial toothpastes against a bacterial consortium of S. mutans, S. sanguinis and S. salivarius. Key words:Antibacterial agents, toothpastes, medicinal plants, Streptococcus mutans, Streptococcus sanguinis, Streptococcus salivarius.

Constituents, Enantiomeric Content, and ChE Inhibitory Activity of the Essential Oil from Hypericum laricifolium Juss. Aerial Parts Collected in Ecuador.

The physical properties, chemical composition, enantiomer distribution, and cholinesterase (ChE) inhibitory activity were determined for a steam-distilled essential oil (EO), with a yield of 0.15 ± 0.05 % (w/w), from H. laricifolium aerial parts, collected in southern Ecuador. The oil qualitative and quantitative analyses were performed by GC-EIMS and GC-FID techniques, using two capillary columns containing a non-polar 5%-phenyl-methylpolysiloxane and a polar polyethylene glycol stationary phase, respectively. The main constituents (>10%) detected on the two columns were, respectively, limonene (24.29, 23.16%), (E)-β-ocimene (21.89, 27.15%), and (Z)-β-ocimene (12.88, 16.03%). The EO enantioselective analysis was carried out using a column based on 2,3-diethyl-6-tert-butyldimethylsilyl-β-cyclodextrin. Two mixtures of chiral monoterpenes were detected containing (1R,5R)-(+)-α-pinene (ee = 83.68%), and (S)-(-)-limonene (ee = 88.30%) as the major enantiomers. This finding led to some hypotheses about the existence in the plant of two enantioselective biosynthetic pathways. Finally, the EO exhibited selective inhibitory effects in vitro against butyrylcholinesterase (BuChE) (IC50 = 36.80 ± 2.40 µg/mL), which were about three times greater than against acetylcholinesterase (IC50 = 106.10 ± 20.20). Thus, the EO from Ecuadorian H. laricifolium is an interesting candidate for investigating the mechanism of the selective inhibition of BuChE and for discovering novel drugs to manage the progression of Alzheimer's disease.

Speciation of metals in indigenous plants growing in post-mining areas: Dihydroxynicotianamine identified as the most abundant Cu and Zn ligand in Hypericum laricifolium

Ag, As, Cu, Pb and Zn were found to be the principal metallic contaminants of a post-mining area of Peru (Hualgayoc, Cajamarca). Study of metal distribution amongst roots, stems, and leaves of four indigenous hypertolerant plant species, Arenaria digyna, Puya sp., Hypericum laricifolium, Nicotiana thyrsiflora indicated significant translocation of Zn (0.6 < TF ≤ 10.0) and Cu (0.4 < TF ≤ 6.5) into aerial plant organs and substantial water-extractable fraction (20–60%) of these metals, except for A. digyna (root and stems). A study of the metal speciation by ultrahigh-performance size-exclusion (fast-SEC) and hydrophilic ion interaction (HILIC) liquid chromatography with dual ICP (inductively coupled plasma) and electrospray (ESI) Orbitrap MS detection revealed the presence of nicotianamine and deoxymugineic acid copper and zinc complexes in roots, stem and leaves of N. thyrsiflora and Puya sp., and nicotianamine alone in A. digyna. A previously unreported compound, dihydroxy-nicotianamine was identified as the most abundant Cu and Zn ligand in H. laricifolium. The presence of arsenobetaine and an arsenosugar was confirmed by ESI MS. Ag and Pb were hardly translocated to leaves and were found as high molecular species; one of the Pb-containing species co-eluted in fast-SEC-ICP MS with rhamnogalacturonan-II-Pb complex commonly found in in the walls of plants.

Accumulation of As, Ag, Cd, Cu, Pb, and Zn by Native Plants Growing in Soils Contaminated by Mining Environmental Liabilities in the Peruvian Andes.

The capability of native plant species grown in polluted post-mining soils to accumulate metals was evaluated in view of their possible suitability for phytoremediation. The study areas included two environmental liabilities in the Cajamarca region in the Peruvian Andes. The content of As, Ag, Cd, Cu, Pb, and Zn was determined in individual plant organs and correlated with soil characteristics. The degree of the pollution depended on the metal with results ranging from uncontaminated (Cd) to moderately (Zn), strongly (As, Cu), and extremely contaminated (Pb, Ag) soils. The metals were mainly present in the fractions with limited metal mobility. The bioaccumulation of the metals in plants as well the translocation into overground organs was determined. Out of the 21 plants evaluated, Pernettya prostrata and Gaultheria glomerate were suitable for Zn, and Gaultheria glomerata and Festuca sp. for Cd, phytostabilization. The native species applicable for Cd phytoremediation were Ageratina glechonophylla, Bejaria sp., whereas Pernettya prostrata Achyrocline alata, Ageratina fastigiate, Baccharis alnifolia, Calceolaria tetragona, Arenaria digyna, Hypericum laricifolium, Brachyotum radula, and Nicotiana thyrsiflora were suitable for both Cd and Zn. None of the studied plants appeared to be suitable for phytoremediation of Pb, Cu, As and Ag.

Estrategias de restauración para el páramo de frailejones perturbado por incendios en el norte de Ecuador

En orden a proponer estrategias para la restauración del páramo de frailejones perturbado por incendios en el norte de Ecuador, este estudio evaluó la efectividad de tres técnicas que utilizaron tres especies nativas en tres sitios con diferente pendiente del terreno: alta (&gt;30%), media (entre 15% y 30%) y baja (&lt;15%). En cada sitio se establecieron seis ensayos de restauración en los que se implementaron las técnicas: introducción de especie nativa, con plantación de Polylepis incana en dos densidades diferentes; reubicación de plantas y regeneración natural, cada una con las especies Hypericum laricifolium e Hypericum lancioides. Las plantas fueron monitoreadas durante 24 meses. Se evaluó la efectividad de las técnicas en términos del éxito en supervivencia, crecimiento y estado fitosanitario de las plantas, mediante el estimador de Kaplan-Meier, análisis de varianza utilizando el test de comparación de medias Tukey (p&lt;0.05) y prueba de Chi cuadrado, respectivamente. Las estrategias fueron propuestas con base en la efectividad de las técnicas en cada sitio. La estrategia para sitios con pendiente alta debe estar conformada por introducción de especie nativa de P. incana en menor densidad y regeneración natural con H. lancioides; para sitios con pendiente media con introducción de especie nativa de P. incana en ambas densidades, y regeneración natural con H. laricifolium; para sitios con pendiente baja con introducción de especie nativa de P. incana en mayor densidad y reubicación de plantas con H. laricifolium y H. lancioides. Las estrategias propuestas contribuyen en el diseño y planificación de la restauración de este importante ecosistema altoandino.

Interactions between nurse-plants and an exotic invader along a tropical alpine elevation gradient: growth-form matters

Conceptual models of how interactions with native species influence invasions emphasize competition, but recent evidence suggests facilitation can promote invasion in stressful environments. However, how nurse-plants with contrasting growth-forms and distribution interact with invaders remains unexplored, although it could offer insights on nurse/exotic interaction mechanisms. We asked whether shrub and cushion nurses differed in their effects on the exotic Rumex acetosella in sites at four elevations in the high tropical Andes (4100–4400 m), shrubs dominating the lowest sites and cushions the highest sites. During the dry season, we measured soil organic matter (SOM) and water content (SWC) under the shrub Hypericum laricifolium, the cushion Azorella julianii, and adjacent areas outside. We compared Rumex’s performance under each situation, measuring midday leaf temperatures (Tleaf), vapor pressure deficit (VPD), minimum water potentials (Ψmin) and leaf nitrogen (Nleaf) and compared the number, size and proportion of fruiting ramets within sampling rings in each situation. SOM and SWC were higher at all elevations under cushions, then under shrubs and lower outside. Rumex’s density was generally reduced under shrubs but increased on cushions. However, both nurses had positive effects along the gradient on Rumex’s size, reproduction, water balance and Nleaf, shrubs having stronger effects on Tleaf and VPD and cushions on Nleaf. Our results indicate that alternating nurses influenced an invader’s physiological performance to different extents via contrasting effects on shading and soil resources, leading to mixed competitive/facilitative effects of shrubs on the exotic’s demography, while cushions had more consistent facilitative effects across elevations.

Stomatal response functions to environmental stress of dominant species in the tropical Andean páramo

ABSTRACTBackground: Stomatal response functions of dominant plant species can provide insights into the behaviour of ecosystems under environmental stress, and provide tools for modelling their response to climate change. However, they remain little studied in tropical Alpine ecosystems.Aims: Our objective was to formulate and compare stomatal response functions for two dominant páramo species with different adaptive strategies to drought, the stress-tolerant shrub Hypericum laricifolium, and the stress avoiding giant rosette Espeletia schultzii and thus enable making projections as to their future fitness in a changing climate.Methods: A reanalysis of data found in the literature and new ecophysiological and micrometeorological measurements were used to fit and test new stomatal response functions to environmental variables for these two species.Results: The response functions of vapour pressure differences between leaf and air showed an exponential decrease for both species, while for photosynthetically active radiation (PAR), peak-form response functions provided the best fit. The response function for leaf water potential was linear for the drought-tolerant shrub and decreased exponentially for the stress avoiding giant rosette. Several thresholds prior to stomatal closure were also included in the functions.Conclusions: Although stress-avoiding and stress-tolerant strategies are both successful in the Andean páramo, the response functions suggest that the tolerant shrub could be more resistant to more intense drought.

Screening In Vitro Targets Related to Diabetes in Herbal Extracts from Peru: Identification of Active Compounds in Hypericum laricifolium Juss. by Offline High-Performance Liquid Chromatography.

This study investigates in vitro targets related to diabetes in 30 herbal extracts from Peru, for the first time, using α-glucosidase, aldose reductase (AR) inhibitory assays and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging assays. Among the 30 herbal extracts, Hypericum laricifolium Juss. (HL) was the herb which showed more than 50% inhibition in all assays, presenting 97.2 ± 2.0%, 56.9 ± 5.6%, 81.9 ± 2.5%, and 58.8 ± 4.6% inhibition for the α-glucosidase, AR, DPPH, and ABTS assays, respectively. Finally, six bioactive compounds, namely, protocatechuic acid, chlorogenic acid, caffeic acid, kaempferol 3-O-glucuronide, quercetin, and kaempferol were identified in HL by offline high-performance liquid chromatography (HPLC). Quercetin exhibited the strongest inhibition in all enzyme assays and the strongest antioxidant activity. The results suggest that HL shows great potential for the complementary treatment of diabetes and its complications.

Screening of Peruvian Medicinal Plants for Tyrosinase Inhibitory Properties: Identification of Tyrosinase Inhibitors in Hypericum laricifolium Juss.

Tyrosinase inhibitors are of far-ranging importance in cosmetics, medicinal products, and food industries. Peru is a diverse country with a wide variety of plants that may contain excellent anti-tyrosinase inhibitors. In the present study, the tyrosinase inhibitory properties of 50 medicinal plant extracts from Peru were investigated using tyrosinase assay. Among plant extracts, those that showed an inhibition rate >50% were Hypericum laricifolium Juss., Taraxacum officinale F.H.Wigg., and Muehlenbeckia vulcanica Meisn., with H. laricifolium Juss. showing the greatest anti-tyrosinase activity. Although H. laricifolium Juss. has been widely used as a medicinal plant by Peruvians, little is known regarding its bioactive components and effects on tyrosinase activity. For this reason, we attempted to discover tyrosinase inhibitors in H. laricifolium Juss. for the first time. The bioactive components were separated by Sephadex LH-20 chromatography and eluted with 100% methanol. Eight compounds were discovered and characterized by high-performance liquid chromatography coupled with diode array detection (HPLC-DAD): protocatechuic acid, p-hydroxybenzoic acid, chlorogenic acid, vanilic acid, caffeic acid, kaempferol 3-O-glucuronide, quercetin, and kaempferol. In addition, the concentration of these compounds required for 50% inhibition (IC50) of tyrosinase activity were evaluated. Quercetin exhibited the strongest tyrosinase inhibition (IC50 14.29 ± 0.3 μM). Therefore, the Peruvian plant H. laricifolium Juss. could be a novel source for anti-tyrosinase activity.

Acylphloroglucinol derivatives from Hypericum laricifolium Juss

A new dimeric acylphloroglucinol derivative, hyperlaricifolin (1), and two new monomeric acylphloroglucinols, laricifolin A (2) and laricifolin B (3), were isolated from an extract of the aerial parts of Hypericum laricifolium Juss., along with the four known dimeric acylphloroglucinols uliginosin B, isouliginosin B, hyperbrasilol B, and isohyperbrasilol B. Their structures were elucidated by interpretation of their 1D-, 2D-NMR and mass spectra.

Antiproliferative activity and phenotypic modification induced by selected Peruvian medicinal plants on human hepatocellular carcinoma Hep3B cells

Ethnopharmacological relevanceThe high incidence of human hepatocellular carcinoma (HCC) in Peru and the wide use of medicinal plants in this country led us to study the activity against HCC cells in vitro of somes species used locally against liver and digestive disorders. Materials and methodsEthnopharmacological survey: Medicinal plant species with a strong convergence of use for liver and digestive diseases were collected fresh in the wild or on markets, in two places of Peru: Chiclayo (Lambayeque department, Chiclayo province) and Huaraz (Ancash department, Huaraz province). Altogether 51 species were collected and 61 ethanol extracts were prepared to be tested.Biological assessment: All extracts were first assessed against the HCC cell line Hep3B according a 3-step multi-parametric phenotypic assay. It included 1) the evaluation of phenotypic changes on cells by light microscopy, 2) the measurement of the antiproliferative activity and 3) the analysis of the cytoskeleton and mitosis by immunofluorescence. Best extracts were further assessed against other HCC cell lines HepG2, PLC/PRF/5 and SNU-182 and their toxicity measured in vitro on primary human hepatocytes. ResultsEthnopharmacological survey: Some of the species collected had a high reputation spreading over the surveyed locations for treating liver problems, i.e. Baccharis genistelloides, Bejaria aestuans, Centaurium pulchellum, Desmodium molliculum, Dipsacus fullonum, Equisetum bogotense, Gentianella spp., Krameria lapacea, Otholobium spp., Schkuhria pinnata, Taraxacum officinale.Hep3B evaluation: Fourteen extracts from 13 species (Achyrocline alata, Ambrosia arborescens, Baccharis latifolia, Hypericum laricifolium, Krameria lappacea, Niphidium crassifolium, Ophryosporus chilca, Orthrosanthus chimboracensis, Otholobium pubescens, Passiflora ligularis, Perezia coerulescens, Perezia multiflora and Schkuhria pinnata) showed a significant antiproliferative activity against Hep3B cells (IC50≤ 50µg/mL). This was associated with a lack of toxicity on primary human hepatocytes in vitro. Immunofluorescence experiments on Hep3B cells showed that crude extracts of Schkuhria pinnata and Orthrosanthus chimboracensis could block Hep3B cells in mitosis with an original phenotype. Crude extracts of Perezia coerulescens, Perezia multiflora, Achyrocline alata, Ophryosporus chilca, Otholobium pubescens and Hypericum laricifolium could modify the overall microtubule cytoskeletal dynamics of Hep3B cells in interphase by an original mechanism. ConclusionsOur method allowed us to select 9 extracts which displayed antiproliferative activities associated with original cellular phenotypes on Hep3B cells, regarding known microtubule-targeting drugs. Both chemical and cellular studies are ongoing in order to elucidate natural compounds and cellular mechanisms responsible of the activities described.

Medicinal plants used in South Ecuador for gastrointestinal problems: An evaluation of their antibacterial potential

The present study aimed to identify the main medicinal plants used by people in Ecuador South Andes to treat gastrointestinal problems, and to evaluate their antibacterial effect. Escherichia coli and Salmonella spp., as gram-negative and Staphylococcus aureus as gram-positive bacteria were used as in vivo models for the antibacterial screening. An ethnobotanical survey about gastrointestinal problems was applied to known healers in the study area. Collected information was contrasted to results of interviews to 13 different yachaks from the same area. The antibacterial potential of chloroform and methanol extracts was evaluated by a micro – dilution technique, and IC50 and IC90 values of the bioactive extracts were estimated. Cytotoxicity of bioactive extracts was assessed using MRC-5 SV2 cells. The ethnomedical approach allowed collecting a total of 132 plants used for the treatment of 9 different gastrointestinal problems described by the consulted experts (yachaks). Among collected plants, 82 are native, 38 are introduced, and 3 are endemic of Ecuadorian Andes. Methanol and chloroform extracts of Hypericum laricifolium, Otholobium mexicanum and Peperomia sp. showed activity against S. aureus, while either chloroform or methanol extracts from other 13 plants were also active against the same bacteria. No activity against gram-negative bacteria was detected. The collected information was verified by yachaks and it agrees with previous ethnomedical reports. The results of antibacterial screening and cytotoxicity assays will contribute to a more rational and safer use of medicinal plants. Key words: Medicinal plants, ethnobotanical survey, gastrointestinal problems, diarrhea, gastroenteritis, antibacterial effect, Cytotoxicity.

Linking patterns and processes through ecosystem engineering: effects of shrubs on microhabitat and water status of associated plants in the high tropical Andes

Studies on alpine and semi-arid environments indicate that plants that act as ecosystem engineers improve microhabitat conditions and modify local plant abundance and diversity. However, few studies have linked these patterns with the physiological responses of associated species. We analyze the role of a dominant shrub (Hypericum laricifolium) as an ecosystem engineer in paramo ecosystems at two altitudes (3,715 and 4,300 m) in the Venezuelan Andes. Superficial soil temperatures, soil water content, and organic matter were compared under the crown and outside. We selected the species with positive and negative spatial relations with the shrub and compared their midday leaf water potentials and turgor loss points in individuals growing under shrubs and outside. Results show that H. laricifolium dampened temperature oscillations and increased soil water and organic matter contents, the effect being more pronounced at the drier, lower elevation site. While positively associated forbs showed an improvement in their water status when growing under the crown, the species with the lowest water potentials and higher water-stress tolerance were grasses with a negative spatial relation with the shrub; this was consistent at both elevations. Moreover, the effect of the shrub on the water status and abundance of the exotic herb Rumex acetosella changed from positive in the drier site to negative in the more mesic site. Our results provide mechanistic evidence for interpreting spatial association patterns between nurse plants and other species in the alpine tropics. We propose that stress-resistance strategies (tolerance vs. avoidance) and origin (native vs. exotic) influence interactions with ecosystem engineers.

Assessing the phytochemical profiles and antidepressant-like activity of four Peruvian Hypericum species using the murine forced swimming test

The antidepressant-like activity of crude ethanolic extracts (CEE) from four Peruvian Hypericum species (Hypericum andinum, Hypericum brevistylum, Hypericum silenoides and Hypericum laricifolium) was assessed using the forced swimming test (FST) in mice. Different doses of all CEE shortened the immobility time of mice in experimental groups, indicating that these extracts possessed a potential antidepressant-like activity. Phytochemical analyses revealed that the CEE were rich in flavonoids, principally hyperoside, and to a lesser extent, dimeric acylphloroglucinol derivatives. The phytochemical composition of Hypericum species with reported antidepressant-like activity in the FST is briefly summarized, and the importance of flavonoids with reference to the activity highlighted.

Xanthones from aerial parts of Hypericum laricifolium Juss

From the aerial parts of Hypericum laricifolium Juss., twelve compounds were isolated and identified. They were the xanthones: 1-hydroxy-7-methoxy-xanthone (1), 1,7-dihydroxy-xanthone (2), 2-hydroxy-xanthone (3), 6-deoxyisojacareubin (4), 1,3-dihydroxy-6-methoxy-xanthone (6), and 1,5,6-trihydroxy-7-methoxy-xanthone (7), together with beta-sitosterol, betulinic acid, vanillic acid, isoquercitrin and a mixture of quercetin and isorhamnetin. All the compounds were characterized by spectroscopic and mass spectrometric methods, and by comparison with literature data. Thisis the first report on the presence of xanthones in H.laricifolium. 1,3-Dihydroxy-6-methoxy-xanthone has been previously synthesized, but this is the first report of its isolation from a natural source.

Chemical Composition of Hypericum laricifolium Juss. Essential Oil Collected from merida-Venezuela

Hypericum is one of nine genera forming the family Hypericaceae distributed mainly in temperate regions and tropical mountains. Fresh aerial parts of H. laricifolium Juss. collected by the Pinango road, Merida state, at 3900 m above sea level, yielded 1.2 mL (0.24% w/v) of essential oil by hydrodistillation. GC and CG/MS analysis showed the presence of 21 components being α-pinene (20.2%), verticiol (13.4%), 3-methyl-nonane (12.3%), 2-methyl-octane (9.6%) and nonane (7.6%) in major proportions. To the best of our knowledge, this is the first report on the chemical composition of the Hypericum laricifolium essential oil.

Minimum inhibitory concentrations of medicinal plants used in Northern Peru as antibacterial remedies

The plant species reported here are traditionally used in Northern Peru to treat bacterial infections, often addressed by the local healers as "inflammation". The aim of this study was to evaluate the minimum inhibitory concentration (MIC) of their antibacterial properties against gram-positive and gram-negative bacteria. The antimicrobial activity of ethanolic and water extracts of 141 plant species was determined using a deep-well broth microdilution method on commercially available bacterial strains. The ethanolic extracts of 51 species inhibited Escherichia coli, and 114 ethanolic extracts inhibited Staphylococcus aureus. In contrast, only 30 aqueous extracts showed activity against Escherichia coli and 38 extracts against Staphylococcus aureus. The MIC concentrations were mostly very high and ranged from 0.008 to 256 mg/ml, with only 36 species showing inhibitory concentrations of <4 mg/ml. The ethanolic extracts exhibited stronger activity and a much broader spectrum of action than the aqueous extracts. Hypericum laricifolium, Hura crepitans, Caesalpinia paipai, Cassia fistula, Hyptis sidifolia, Salvia sp., Banisteriopsis caapi, Miconia salicifolia and Polygonum hydropiperoides showed the lowest MIC values and would be interesting candidates for future research. The presence of antibacterial activity could be confirmed in most species used in traditional medicine in Peru which were assayed in this study. However, the MIC for the species employed showed a very large range, and were mostly very high. Nevertheless, traditional knowledge might provide some leads to elucidate potential candidates for future development of new antibiotic agents.

Temporal changes in local spatial structure of late‐successional species: establishment of an Andean caulescent rosette plant

Summary 1 We analyse successional changes in local spatial structure of populations of a dominant late-successional species ( Espeletia schultzii ) in the high tropical Andes. 2 Spatial maps of plants of E. schultzii and important features of their environment were recorded at early (year 3) and middle (year 8) stages of succession after agricultural disturbance, and in non-cultivated paramo. 3 Spatial covariance functions were calculated from the maps to provide information on the changing ‘plant-eye’s view’ of seedlings and adults during succession, and on the coupling of spatial structure to dynamics of successional communities. 4 Seedlings of E. schultzii appeared at high densities shortly after agricultural disturbance ceased. Spatial aggregation, which among seedlings was strongest in later stages of succession, was absent among adults, suggesting greater mortality within aggregations of conspecifics plays a part in regulating population dynamics. 5 Early in succession, seedlings of E. schultzii were slightly segregated from the dominant early successional species, Rumex acetosella . By year 8 of succession, R. acetosella was strongly segregated from adults of E. schultzii , but not from seedlings. This suggests that competitive exclusion caused by asymmetric competition may contribute to decline in early successional species. 6 Spatial sorting in relation to abiotic factors was most evident in the mature paramo, with E. schultzii adults occurring on steeper slopes and on less stony ground. E. schultzii adults here were also segregated from Hypericum laricifolium , the other dominant species. 7 The coupling of local spatial structure to community dynamics may have profound effects on succession. In particular, the development of interspecific segregation could contribute to the continued coexistence of early and late successional species throughout succession.

Ecophysiology of Dominant Plant Species during Old-Field Succession in a High Tropical Andean Ecosystem

We compared ecophysiological characteristics of plant species that dominate during different stages of succession in fallow fields of a traditional agroecosystem in the Venezuelan High Andes. For each species we determined during the dry and wet seasons the photosynthetic light response and photosynthesis rate at light saturation (Amax), specific leaf area (SLA), stomatal conductance at light saturation (gmax), midday water potential (ψ), and intrinsic water use efficiency (WUEi, photosynthesis rate per unit of stomatal conductance). The species studied were the forbs Rumex acetosella (early succession dominant) and Lupinus meridanus (intermediate stages), the shrubs Acaena elongata and Baccharis prunifolìa (late succession), the giant rosette Espeletia schultzii, and the shrub Hypericum laricifolium (mature ecosystem dominant). Clear ecophysiological trends were identified: early and intermediate successional species had higher Amax, gmax, and SLA but lower WUEi. E. schultzii maintained a high water potential during the dry season and, together with B. prunifolia, was the only species with no significant differences in Amax between seasons. The results indicate that traits generally linked to fast growth (high Amax and SLA) are associated with dominance during early succession, while traits linked with drought resistance (e.g., high WUEi and thick xeromorphic leaves) are associated with dominance during late succession in this tropical mountain environment.

Vegetation patterns, regeneration rates and divergence in an old-field succession of the high tropical Andes

Vegetation restoration during old-field succession was studied in an alpine Andean ecosystem (paramo). 123 plots with different fallow times (1 to 12 years) and 8 plots under natural vegetation were sampled. The results indicate that secondary succession in the paramo, like in other extreme environments, can be interpreted as an autosuccession: there are mainly changes in species relative abundance and little floristic relay (i.e. species turnover). Only a few herbaceous species, mostly introduced (e.g. Rumex acetosella), act as strict pioneers and strongly dominate the early stages. Then, they undergo a progressive decline, while native forbs (e.g. Lupinus meridanus) and grasses (e.g. Vulpia myuros) have their peak abundance in intermediate stages. The characteristic paramo life forms, sclerophilous shrubs (e.g. Baccharis prunifolia, Hypericum laricifolium) and giant rosettes (e.g. Espeletia schultzii), appear very early and gradually increase in abundance during succession, becoming dominant in the late stages and showing a dual behaviour, both as ruderal and stress tolerant species. The 1st axis of a Detrended Correspondence Analysis arranges the sites according to their fallow time. The 2nd and 3rd axes, associated with diverging pathways of regeneration, are correlated with topographic factors and physio-chemical soil characteristics. Hence, structural divergence between plots increases along succession as community composition starts to reflect the conditions of each site. We found evidence of a constant rate of succession during the first 12 years, contradicting the generally accepted hypothesis in the succession literature of a continous slow down up to the climax. Regeneration of vegetation physiognomy is relatively fast, questioning the prevailing idea of slow restoration in alpine ecosystems. However, 12 years of fallow are insufficient to attain the species richness of the natural paramo. Under the current trend of fallow length reduction observed in traditional potato cultivation in the Andes, our results raise doubts about the conservationist value of this management strategy.