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1.
An Acad Bras Cienc ; 89(2): 1189-1203, 2017.
Article in English | MEDLINE | ID: mdl-28640356

ABSTRACT

Currently, there is a lack of studies on the correct utilization of continuous distributions for dry tropical forests. Therefore, this work aims to investigate the diameter structure of a brazilian tropical dry forest and to select suitable continuous distributions by means of statistic tools for the stand and the main species. Two subsets were randomly selected from 40 plots. Diameter at base height was obtained. The following functions were tested: log-normal; gamma; Weibull 2P and Burr. The best fits were selected by Akaike's information validation criterion. Overall, the diameter distribution of the dry tropical forest was better described by negative exponential curves and positive skewness. The forest studied showed diameter distributions with decreasing probability for larger trees. This behavior was observed for both the main species and the stand. The generalization of the function fitted for the main species show that the development of individual models is needed. The Burr function showed good flexibility to describe the diameter structure of the stand and the behavior of Mimosa ophthalmocentra and Bauhinia cheilantha species. For Poincianella bracteosa, Aspidosperma pyrifolium and Myracrodum urundeuva better fitting was obtained with the log-normal function.


Subject(s)
Forests , Plant Dispersal/physiology , Trees/growth & development , Tropical Climate , Anacardiaceae/growth & development , Aspidosperma/growth & development , Bauhinia/growth & development , Biodiversity , Brazil , Caesalpinia/growth & development , Geographic Mapping , Mimosa/growth & development , Reference Values , Statistics, Nonparametric , Trees/classification
2.
An. acad. bras. ciênc ; 89(2): 1189-1203, Apr.-June 2017. tab, graf
Article in English | LILACS | ID: biblio-886706

ABSTRACT

ABSTRACT Currently, there is a lack of studies on the correct utilization of continuous distributions for dry tropical forests. Therefore, this work aims to investigate the diameter structure of a brazilian tropical dry forest and to select suitable continuous distributions by means of statistic tools for the stand and the main species. Two subsets were randomly selected from 40 plots. Diameter at base height was obtained. The following functions were tested: log-normal; gamma; Weibull 2P and Burr. The best fits were selected by Akaike's information validation criterion. Overall, the diameter distribution of the dry tropical forest was better described by negative exponential curves and positive skewness. The forest studied showed diameter distributions with decreasing probability for larger trees. This behavior was observed for both the main species and the stand. The generalization of the function fitted for the main species show that the development of individual models is needed. The Burr function showed good flexibility to describe the diameter structure of the stand and the behavior of Mimosa ophthalmocentra and Bauhinia cheilantha species. For Poincianella bracteosa, Aspidosperma pyrifolium and Myracrodum urundeuva better fitting was obtained with the log-normal function.


Subject(s)
Trees/growth & development , Tropical Climate , Forests , Plant Dispersal/physiology , Reference Values , Trees/classification , Brazil , Statistics, Nonparametric , Anacardiaceae/growth & development , Aspidosperma/growth & development , Caesalpinia/growth & development , Bauhinia/growth & development , Mimosa/growth & development , Biodiversity , Geographic Mapping
3.
Oecologia ; 178(3): 847-54, 2015 Jul.
Article in English | MEDLINE | ID: mdl-25707777

ABSTRACT

Successful persistence of dry forests depends on tree regeneration, which depends on a balance of complex biotic interactions. In particular, the relative importance and interactive effects of shrubs and herbivores on tree regeneration are unclear. In a manipulative study, we investigated if thornless shrubs have a direct net effect, an indirect positive effect mediated by livestock, and/or an indirect negative effect mediated by small vertebrates on tree regeneration of two key species of Chaco forest (Argentina). In a spatial association study, we also explored the existence of net positive interactions from thorny and thornless shrubs. The number of Schinopsis lorentzii seedlings was highest under artificial shade with native herbivores and livestock excluded. Even excluding livestock, no seedlings were found with natural conditions (native herbivores present with natural shade or direct sunlight) at the end of the experiment. Surprisingly, seedling recruitment was not enhanced under thornless shrubs, because there was a complementary positive effect of shade and interference. Moreover, thornless shrubs had neither positive nor negative effects on regeneration of S. lorentzii. Regeneration of Aspidosperma quebracho-blanco was minimal in all treatments. In agreement with the experiment, spatial distributions of saplings of both tree species were independent of thornless shrubs, but positively associated with thorny shrubs. Our results suggest that in general thornless shrubs may have a negligible effect and thorny shrubs a net positive effect on tree regeneration in dry forests. These findings provide a conceptual framework for testing the impact of biotic interactions on seedling recruitment in other dry forests.


Subject(s)
Anacardiaceae/growth & development , Aspidosperma/growth & development , Capparis , Forests , Herbivory , Animals , Argentina , Ecosystem , Random Allocation , Seedlings/growth & development , Trees/growth & development
4.
Rev Iberoam Micol ; 24(2): 142-7, 2007 Jun.
Article in Spanish | MEDLINE | ID: mdl-17604434

ABSTRACT

Aspidosperma quebracho-blanco (white quebracho) and Schinopsis balansae (red quebracho) are distinctive trees of the South American Park in Argentina. Quebrachos are found in forests that have been exploited very intensively. The object of this work was the identification of biotic and abiotic factors specially fungal pathogen that affect the quality of both species and its relation with germination. Seeds where evaluated through germination test and the percentage of the incidence of fungal agents in two different years of harvest was determined. In S. balansae the germination rate was 77% and of 27% in 2000 and 2001 harvests, respectively. Associations fungi-germination were found in 2001 for Alternaria spp., Curvularia spp., and Fusarium spp., showing an coefficient of correlation = -0.84; -0.85 and -0.73 (p < 0.00004), respectively. A high percentage of vane seeds (55%) was also found in 2001 harvest, due to adverse environmental factors, specifically higher precipitations during flowering. In A. quebracho-blanco seeds, the germination rate was 50% and 90% in 2000 and 2003 respectively, with a 42% of immature seeds in 2000 harvest that was associated to high precipitations and high temperatures during flowering and ripping of fruits. The incidence of pathogens was low and did not have association to germination.


Subject(s)
Anacardiaceae/embryology , Aspidosperma/embryology , Germination , Seeds , Alternaria/isolation & purification , Anacardiaceae/growth & development , Anacardiaceae/microbiology , Aspergillus niger/isolation & purification , Aspidosperma/growth & development , Aspidosperma/microbiology , Chaetomium/isolation & purification , Fruit/microbiology , Humidity , Plant Diseases/microbiology , Rain , Seasons , Seeds/microbiology , Seeds/physiology , South America , Temperature
5.
Metab Eng ; 4(3): 257-62, 2002 Jul.
Article in English | MEDLINE | ID: mdl-12616695

ABSTRACT

Metabolic engineering represents a promising approach to enhance the yield of valuable natural products from plants. A method to quantify flux through metabolite measurements is necessary for the analysis of native and modified pathways. Rather than focusing only on the accumulation of the final products, analyzing a wide range of secondary metabolites has significant advantages. We propose a model that organizes the flux analysis by grouping metabolites of similar biosynthetic origin. To this end, we have quantified temporal profiles of metabolites from several branches of the indole alkaloid pathway in Catharanthus roseus hairy root cultures. By analyzing these data, we are able to examine the distribution of flux around key branchpoints. Furthermore, this analysis provides crucial information such as an estimate of total flux to secondary metabolism.


Subject(s)
Catharanthus/growth & development , Catharanthus/metabolism , Indole Alkaloids/metabolism , Models, Biological , Plant Roots/growth & development , Plant Roots/metabolism , Aspidosperma/growth & development , Aspidosperma/metabolism , Cell Line , Computer Simulation , Models, Genetic , Species Specificity , Tabernaemontana/growth & development , Tabernaemontana/metabolism
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