Spatial and temporal distribution of tropical biomass burning Hao, W.M. (Intermountain Fire Sciences Laboratory, Intermountain Research Station, Forest Service, USDA, Missoula, Montana); Liu, M.H
Global biogeochemical cycles,
December 1994, Volume:
8, Issue:
4
Journal Article
Early evaluation of root morphology of maize genotypes under phosphorus deficiency Magalhaes, P.C.,National Maize and Sorghum Research Center, Sete Lagoas (Brazil); De Souza, T.C.,Federal Univ. of Lavras (Brazil). Biology Dept; Cantao, F.R.O.,University of Illinois, Urbana-Champaign (USA)
Plant, soil and environment,
03/2011
3
Journal Article
Peer reviewed
Open access
The aim of this paper was to evaluate the effect of two levels of phosphorus in soil (high and low P levels) on dry mass attributes and root characteristics in eight maize lines with different ...genetic backgrounds and origins. The experimental design was randomized blocks with three replications. The evaluation was performed 21 days after sowing. The WinRhizo program of images analysis was used for the root morphology. There were no differences between the two P levels for the dry mass attributes. However, root morphology of L13.1.2 strain performed the highest surface area and total root length, length of thin and very thin roots in low P concentration. The digital image analyses of root systems allowed efficient discrimination of maize genotypes in environments with low P levels.
Root symbioses of trees in savannas Hoberg, P. (Department of Forest Site Research, Swedish University of Agricultural Sciences, 901-83 Umea (Sweden))
1989
Book
Dry season survival of Anopheles funestus, Anopheles gambiae and Anopheles arabiensis in the Kilombero valley a dry savannah zone of east Africa, was investigated with over 400 collections from 23 ...areas, covering 300 sq km of the valley. Anopheles gambiae was found only in association with humans, in forested areas of high annual rainfall, while An. funestus occurred at high densities at the valley edge where large non-moving bodies of water remained. A large population of An. arabiensis was present along the river system throughout the middle of the valley, and mosquitoes probably derived from this population were occasionally caught in villages bordering the valley. No evidence was obtained of aestivation in any mosquito species. Anopheles gambiae was the most long lived, 6.3% compared to 2.0% of the An. arabiensis and 4% of the An. funestus surviving for four or more gonotrophic cycles, the approximate duration of the extrinsic cycle of most malaria parasites. Oocysts of malaria parasites were found in 5.4% of An. funestus and 2.3% of An. arabiensis from villages. Oocyst rates in An. funestus differed significantly between areas but not between houses within areas. Anopheles funestus is the most important dry season malaria vector in the valley, and remains in foci closely associated with groups of houses. All three species survive at high densities but as otherwise hidden refugia populations.
Modern soil science, spearheaded by research in Brazil has facilitated the utilization of vast areas of previously uncultivated soil long considered unsuitable for human food production into highly ...productive agricultural land. Naturally acid soils with high contents of aluminum and iron oxides and low CEC values and organic matter contents long considered insurmountable obstacles to crop production in tropical latitudes could be extremely productive. With continued development of the infrastructure needed by commercial agriculture Brazil has the potential to lead the world in its quest to provide food for growing human populations.
A moderna ciência de solo, liderada pelas suas pesquisas no Brasil, tem possibilitado a utilização de vastas áreas de solos, durante muito tempo não cultivados por serem avaliados como inaptos para uma intensiva produção de alimentos. Hoje, ao contrário, constata-se que essas terras são altamente produtivas para a agricultura. Estas pesquisas vêm mostrando que alguns atributos naturais destes solos, como acidez, baixos teores de matéria orgânica, baixa capacidade de troca de cátions, além de altos teores de óxidos de ferro e/ou de alumínio - considerados como obstáculos à produção de boas colheitas em latitudes tropicais - podem ser superados. Com a continuação do desenvolvimento das infra-estruturas necessárias para alavancar ainda mais a agricultura comercial, o Brasil tem potencial para, em breve, liderar o mundo no que tange ao fornecimento de alimentos para as crescentes populações humanas.
During the last decade, management of woodlands in the Sudanian region of Benin has been based on enrichment with valuable tree-species. Yet, no previous research has been undertaken to support ...enrichment design with respect to plant eye view, tree growth magnitude or survival capacity under local forest environments. To fill in this gap, Ripley's K function was used to assess the spatial pattern of trees, diameter classes and dominant valuable species in the Sudanian zone. Data were collected in four sites of variable size (150 × 100 m, 150 × 100 m, 100 × 50 m and 150 × 150 m). Mostly, the spatial patterns of the target species revealed small-clumps. Within these small-clumps, intraspecific repulsions were observed on average at a 3 m scale, while interspecific repulsions were noticed at a 4.5 m scale. Only a weak repulsion between diameter size was also remarked, suggesting that proximity to adult trees would not affect the survival of young plants. With regard to observed repulsion scales, we would suggest using a minimum of a 3 m space between trees of the same species and a 4.5 m space between trees of different species, for enrichment plantings in Sudanian woodlands, if based on the target species. However, this suggested spacing may not be optimal with regard to plant growth. Further investigation is needed to address this aspect. PUBLICATION ABSTRACT
http://dx.doi.org/10.5902/1980509810541 The seed germination strategy is important for the survival of species, allowing their maintenance and regeneration in the environment. Seed germination and ...seedling emergence of Anadenanthera colubrina were studied to examine the reproductive efficiency of this species, typical of Cerrado biome. The fruits were collected in ‘Vale do Rio Araguari’, in MG state. The water content at 105 °C, the germination in controlled laboratory conditions and seedling emergence in semi-open greenhouse were analyzed. The seeds had low water content between 6.7 to 10.7%. The germinating ability and the emergence percentage were high for almost all studied individuals, being registered 68 for seeds of individual number 2 and 85 - 94% for the others; 38% (individual number 2) and 78 - 91% (for the others), respectively. The speed of the processes was high, with the end of germination within 12.8 days and emergence within 18.8 days. The processes were heterogeneous, with values of coefficient of variation of the germination or emergence time above 28.5%; asynchronous, with values of uncertainty above 1.5 bits and synchrony below 0.3812. The seeds of this species were efficient in both processes and the heterogeneity and asynchrony may indicate the effects of environmental fluctuations during the seed formation, besides the genetic variability, intrinsic to each individual of the population. The speed and the high potential of seed germination of this species may also facilitate the programs of reforestation with the production of large numbers of seedlings in short time.
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