Reproductive biology of two species of Kielmeyera (Guttiferae) in the cerrados of Central Brazil

1993 ◽  
Vol 9 (1) ◽  
pp. 67-79 ◽  
Author(s):  
Paulo E. Oliveira ◽  
Jose C. S. Silva
Keyword(s):  
Seedling Survival ◽  
Biotic Factors ◽  
Wet Season ◽  
Natural Conditions ◽  
Reproductive Process ◽  
Central Brazil ◽  
Seedling Bank ◽  
Pollination Systems ◽  
Adult Plants ◽  
Root Swelling

ABSTRACTThe reproductive process of two species of Kielmeyera, K. coriacea and K. speciosa, sympatric in savanna areas in central Brazil, has been studied. The trees have similar pollination systems and dispersal mechanisms but distinct phenological behaviours. Fast germination after the beginning of the wet season, early root swelling forming a xylopodium which enables survival during the dry season, and recurrent sprouting from the swollen root system during the first years of development were features of an establishment syndrome common to both species. The seedling survival after establishment was high; after five years 64% of the seedling cohort of K. coriacea was still alive. These seedlings, in natural conditions, remain poorly developed and resprout recurrently from the soil during some years. The recruitment of adult plants seems to occur from this ‘seedling bank’. The reproductive process was higher in K. coriacea during most stages of the reproductive process which may explain the smaller population size and distribution range of K. speciosa. For both species, the reproductive process as a whole was mainly affected by biotic factors in the wet season and not by seasonal drought or periodic fire.

scholarly journals Branch elongation and diameter growth were temporally dissociatedin "cerrado" tree species

Hoehnea ◽  
2009 ◽  
Vol 36 (3) ◽  
pp. 437-444 ◽  
Author(s):  
Davi Rodrigo Rossatto
Keyword(s):  
Water Status ◽  
Carbon Assimilation ◽  
Dry Season ◽  
Diameter Growth ◽  
Wet Season ◽  
Dry Period ◽  
Central Brazil ◽  
Branch Growth ◽  
Tree Community ◽  
One Year

Here is a communicating about time differences between branch and diameter growth in a tree community of ten species in Neotropical savanna ("cerrado") of Central Brazil. This work was conducted to study branch expansion and diameter growth in a period of one year between 2006 and 2007. Branch growth had begin in middle dry season and had the peak occurrence during the dry period in September, while diameter growth had begin in late dry season and peaked in the middle of wet season in December. The majority of species followed the same pattern. Branch growth did not have relation with rainfall, while diameter growth had a clear and positive relation with rainfall records. These results suggested that branch growth was not depend on rainfall but only on water status recover, while diameter growth probably depends strongly on water and to carbon assimilation that occurs after branch and leaf expansion.

The effect of water supply on tree seed germination and seedling survival in a tropical seasonal forest in Veracruz, Mexico

1991 ◽  
Vol 7 (1) ◽  
pp. 69-83 ◽  
Author(s):  
Dominique Blain ◽  
Martin Kellman
Keyword(s):  
Water Supply ◽  
Tree Species ◽  
Seedling Survival ◽  
Light Level ◽  
Water Retention Capacity ◽  
Wet Season ◽  
Retention Capacity ◽  
Large Fluctuations ◽  
Rainfall Patterns ◽  
Tropical Seasonal Forest

ABSTRACTIn Iropical seasonal forests, mass seedling death may incidentally occur early in the rainy season following untimely germination provoked by an isolated heavy rainfall. We hypothesized that, in a soil with little moisture retention capacity, irregular rainfall patterns would result in large fluctuations of water supply and, in the early wet season, drought episodes could cause seedling death. This hypothesis was tested in a seasonal tropical forest in Mexico where seedling density is low and the soil consists of almost pure sand with a low water retention capacity. Various patterns of simulated rainfall were applied in the forest to seeds and seedlings of three common tree species. Overall very little difference in germination and seedling survival was observed between the various rainfall treatments. The results showed that rainfall patterns and the soil texture may interact in a much more complex way than was initially hypothesized, and that water availability to seeds and seedlings is not necessarily predictable. The absence of seedlings of the three tree species might be better explained by high seed predation and low light level in the understorey.

scholarly journals Environmental factors determining growth of salamander larvae: A field study

2015 ◽  
Vol 61 (3) ◽  
pp. 421-427 ◽  
Author(s):  
Laura Limongi ◽  
Gentile Francesco Ficetola ◽  
Giuseppe Romeo ◽  
Raoul Manenti
Keyword(s):  
Field Study ◽  
Environmental Variables ◽  
Larval Growth ◽  
Experimental Studies ◽  
Field Studies ◽  
Development Rate ◽  
Biotic Factors ◽  
Natural Conditions ◽  
Fire Salamander ◽  
Salamander Larvae

Abstract Larval growth and survival of organisms are strongly influenced by abiotic and biotic factors, as demonstrated by experimental studies performed under controlled laboratory or semi-natural conditions. Even if they have many advantages, experiments cannot cover the full complexity of natural conditions and field studies are needed for a better understanding of how environmental variation determines growth and development rate. Fire salamander Salamandra salamandra females give birth to larvae in a variety of habitats, both epigean and subterranean. In caves, salamander larvae successfully grow and metamorphose, but their growth is more than three times longer than in epigean streams and factors determining these differences require investigation. We performed a field study to understand the factors related to the growth of fire salamander larvae in different environmental conditions, evaluating the relationship between environmental features and larval growth and differences between caves and epigean spring habitats. Both caves and epigean larvae successfully grew. Capture-mark-recapture allowed to individually track individuals along their whole development, and measure their performance. Growth rate was significantly affected by environmental variables: larvae grew faster in environments with abundant invertebrates and few conspecifics. Taking into account the effect of environmental variables, larval growth was significantly lower in caves. Food availability plays a different effect in the two environments. Larval growth was positively related to the availability of invertebrates in epigean sites only. The development rate of hypogeous populations of salamanders is slower because of multiple parameters, but biotic factors play a much stronger role than the abiotic ones.

scholarly journals Daily Precipitation Statistics for South America: An Intercomparison between NCEP Reanalyses and Observations

2011 ◽  
Vol 12 (1) ◽  
pp. 101-117 ◽  
Author(s):  
Viviane B. S. Silva ◽  
Vernon E. Kousky ◽  
R. Wayne Higgins
Keyword(s):  
South America ◽  
Large Scale ◽  
Atmospheric Model ◽  
Northeastern Brazil ◽  
South American ◽  
The South ◽  
Wet Season ◽  
Central Brazil ◽  
Monsoon System ◽  
Dry Bias

Abstract In this study, the authors document the extent to which the precipitation statistics of the new CFS reanalysis (CFSR) represent an improvement over the earlier reanalyses: the NCEP–NCAR reanalysis (R1) and the NCEP–DOE Second Atmospheric Model Intercomparison Project (AMIP-II) reanalysis (R2). An intercomparison between the CFSR, R1, R2, and observations over South America was made for the period 1979–2006. The CFSR shows notable improvements in the large-scale precipitation patterns compared with the previous reanalyses (R1 and R2). In spite of these improvements, the CFSR has substantial biases in intensity and frequency of occurrence of rainfall events. Over west-central Brazil, the core region of the South American monsoon system (SAMS), the CFSR displays a dry bias during the onset phase of the SAMS wet season and a wet bias during the peak and decay phases of the SAMS wet season. The CFSR also displays a dry bias along the South American coast near the mouth of the Amazon and along the east coast of northeastern Brazil. A wet bias exists in all seasons over southeast Brazil and over the Andes Mountains.

scholarly journals Vertical and horizontal distribution of pollination systems in cerrado fragments of central Brazil

2007 ◽  
Vol 50 (3) ◽  
pp. 503-514 ◽  
Author(s):  
Fernanda Quintas Martins ◽  
Marco Antônio Batalha
Keyword(s):  
Spatial Distribution ◽  
Significant Variation ◽  
Horizontal Distribution ◽  
Bee Pollination ◽  
Vertical Variation ◽  
Pollination System ◽  
Cerrado Vegetation ◽  
Central Brazil ◽  
Vertical And Horizontal Distribution ◽  
Pollination Systems

In fragments of the cerrado, we determined the frequency of pollination systems and analyzed their spatial distribution. We placed 38 transects, sampling 2,280 individuals and 121 species. As expected in Neotropical regions, bee-pollination was the most frequent pollination system. We found a decrease in the frequency of plants pollinated by beetles towards the fragment interior. Similarly, we found significant variation in relation to height just for the bats; there was an increase in the frequency of plants pollinated by bats towards the higher heights. In general, we found no horizontal and vertical variation in the pollination systems, probably as consequence of the more open physiognomy of the cerrado vegetation.

Fire, growth and survivorship in a Neotropical savanna grass Andropogon semiberbis in Venezuela

1989 ◽  
Vol 5 (4) ◽  
pp. 387-400 ◽  
Author(s):  
Juan F. Silva ◽  
Fernando Castro
Keyword(s):  
Seedling Growth ◽  
Canopy Structure ◽  
Structural Complexity ◽  
Dry Season ◽  
Root Competition ◽  
Annual Rainfall ◽  
Grass Species ◽  
Mortality Factors ◽  
Wet Season ◽  
Adult Plants

ABSTRACTThis study was conducted in a woodland savanna in western Venezuela exclosed from grazing and burnt once a year towards the end of the dry season. Mean annual rainfall is 1500 mm, with a strong seasonality.Two cohorts of seedlings of Andropogon semiberbis were tagged and monitored for up to three years. Several variables such as survivorship, plant size, seedling density, fire damage and distance to the nearest adult were measured or estimated. Two burning experiments to measure survivorship before and after fire, and two seedling-growth experiments to assess competitive interference from adult plants of three grass species were performed.The highest mortality takes place during the dry season and is due to fire. This decreases as the plants get bigger due to increasing structural complexity of the clump by growth which gives added protection to the meristems. Other mortality factors such as desiccation, uprooting and shading seem to be important during the wet season, when mortality rate is relatively constant. Survivorship during the first year and after three years is strongly correlated to the size attained by the end of the first growing season.Seedling densities are rather low and do not seem to play any role in survivorship in this population. Adult interference with seedling growth decreases with distance and seems to be due to root competition, although there is a tendency toward increased foliage interference related to the canopy structure of adult plants.

Establishment of Stylosanthes species: changes in hardseededness and potential speed of germination at Katherine, N.T

1983 ◽  
Vol 34 (5) ◽  
pp. 491 ◽  
Author(s):  
GM McKeon ◽  
K Brook
Keyword(s):  
Heat Treatment ◽  
Seedling Establishment ◽  
Seedling Survival ◽  
High Surface ◽  
Wet Season ◽  
Untreated Seed ◽  
Slow Potential ◽  
Hard Seed ◽  
Heat Treated ◽  
Germination Speed

The breakdown of hard seed, germination and establishment of heat-treated and untreated seed was compared for Stylosanthes humilis, S. hamata cv. Verano and S. scabra cv. Fitzroy at Katherine, N.T. Heat treatment significantly increased yield and seedling establishment for S. hamata and S, scabra. Recovery of seed samples at the end of the wet season showed that no decrease in hard seed occurred after the first wave of seedling establishment at the onset of the wet season. This result indicates that high surface temperatures are required for seed softening, and that hard seed which has not broken by the onset of the wet season is unlikely to contribute to the sward in the season of sowing. The lack of a significant heat-treatment effect for S. humdis was attributed to the high soft-seed content (29%) in the untreated seed at the time of sowing and the loss of seedlings from the heat-treated seeds owing to rapid germination on rainfall insufficient for seedling survival. In a second experiment, the changes in seed characteristics of heat-treated seed sown in the late dry season were studied. Seed was recovered before and after each major rainfall event. Standard germination tests were carried out at near optimal conditions of water availability, light and temperature to measure potential germination speed and changes in viability. Large increases in potential germination speed occurred over 4 weeks in the field-from < 10% germination in 18 h to 70-90% in 18 h. As a result, greater than 80% of germination occurred on isolated rainfall events with less than 18-h surface moisture and were followed by rapid seedling death. We found that slow potential germination speed of sown seed did not confer permanent protection against false-start germination, since large increases in potential germination speed are likely to occur under field conditions.

Two-year study of male orchid bee (Hymenoptera: Apidae: Euglossini) attraction to chemical baits in lowland south-eastern Perú

1985 ◽  
Vol 1 (1) ◽  
pp. 37-54 ◽  
Author(s):  
David L. Pearson ◽  
Robert L Dressler
Keyword(s):  
Flood Plain ◽  
Flowering Phenology ◽  
Seasonal Abundance ◽  
Wet Season ◽  
Terra Firme ◽  
Central Brazil ◽  
Orchid Bee ◽  
South Eastern ◽  
Forest Sites ◽  
A Minor

ABSTRACTChemical baits corresponding to natural orchid fragrance chemicals were used to attract and sample male orchid bees in terra firme and flood plain forest sites on the Tambo-pata Reserve in south-eastern Perú. The study was conducted monthly for two years. A total of 38 species of bees was collected at these chemical baits, and although most species were collected from both habitats, 11 species were significantly more common in one habitat than the other. There was considerable variation in the number and types of chemicals to which each of the orchid bee species was attracted.Two cycles of seasonal abundance occurred annually in the number of orchid bee individuals and species collected at the chemical baits. A major peak occurred a month following onset of the wet season, and a minor peak occurred during the dry season. Species body size was related to seasonal activity, but additional factors such as flowering phenology and nest parasites were also probably involved.The number of orchid bee species found on the Tambopata Reserve was similar to the number found in forest sites of eastern and central Brazil, Costa Rica, and Panamá. This homogeneity in species richness is in marked contrast to other insect groups such as Odonata, Lepi-doptera, Asilidae (Diptera), Tabanidae (Diptera), and Cicindelidae (Coleoptera), for which the species numbers recorded on the Tambopata Reserve are the highest for any similar sized area in the world.

Habitat Segregation by Serotinous Shrubs in Heaths: Post-fire Emergence and Seedling Survival

1997 ◽  
Vol 45 (1) ◽  
pp. 31 ◽  
Author(s):  
Paul R. Williams ◽  
Peter J. Clarke
Keyword(s):  
Soil Moisture ◽  
Field Experiments ◽  
Seedling Survival ◽  
Habitat Segregation ◽  
Differential Survival ◽  
Shrub Species ◽  
Edge Zone ◽  
Drainage Channels ◽  
Germination Trial ◽  
Adult Plants

Seeds of two serotinous shrub species generally restricted to the drier edges, and two serotinous shrub species commonly confined to the wetter drainage channels of upland sedge–heaths were assessed for germinability and used in manipulative field experiments. In post-fire field experiments the effects of habitat and manipulated soil moisture were examined to test if the distribution of adult plants was influenced by soil moisture at seed germination. The effects of habitat on seedling survival for 11 months were also assessed. One species from the edge zone, Banksia marginata Cav., and one from the channel zone, Hakea microcarpa R.Br., had germination preferences corresponding to the distribution of adult plants. The other edge species, Hakea dactyloides (Gaertner) Cav., did not show a significant preference for either zone. The second channel species, Callistemon pityoides F.Muell., did not germinate in the field or in a laboratory germination trial. Some evidence for soil-stored dormancy related to temperature and or waterlogging was found in both Hakea species. Overall the results suggest that for two species habitat segregation occurs when seeds are incorporated into the seed-bed and germination occurs. No differential survival effects across habitats were found in the first year of growth.

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