巴西Embrapa的大豆育种程序

成立于1973年的巴西农牧研究院(Embrapa)是巴西的主要农业研究机构,拥有的39个研究中心遍布全国,大豆研究所位于巴西南部Londrina市,距巴西利亚约1000公里,其主要任务是从事大豆育种、栽培技术和生物技术研究,是巴西大豆生产的技术支撑.本文重点介绍了Embrapa大豆研究中心的大豆育种程序,配制组合较多,后代种植面积较大是其特点.     

Potential causes of population declines in forest fragments in an Amazonian frog

Forest fragmentation results in population declines and extinctions for many forest vertebrates, but little is known about the mechanisms causing declines in fragments. We investigated potential causes of declines in forest fragments for an Amazonian forest frog (Colostethus stepheni) at an experimental fragmentation study site in central Amazonian Brazil using field estimates of abundance and vital rates coupled with population simulations. Although adult male survival was not reduced by fragmentation, mean clutch size was reduced by 17%. Population simulations demonstrate that a reduction in clutch size of this magnitude is sufficient to cause the observed magnitude of population declines in fragments. Female snout-vent length was also reduced in fragments and may be related to the observed reduction in clutch size.     

The value of primary, secondary and plantation forests for Amazonian birds

Secondary forests and exotic tree plantations are rapidly expanding across tropical landscapes, yet we currently have a very poor understanding of the value of these human-dominated forest landscapes for biodiversity conservation. Mist netting, point counts and transect walks were used to compare the bird communities of these habitats and neighboring primary forest in north-east Brazilian Amazonia. The extensive spatial scale of plantations and second-growth in our study area enabled us to implement a robust replicated design, with survey plots approximately two to three orders of magnitude larger than most previous studies of land-use change in the tropics, thus minimising the influence of the surrounding landscape. Species richness was highest in primary forest and lowest in Eucalyptus plantations, and community turnover between habitats was very high whether based upon matrices of relative abundance or species presence-absence data, and for both point count and mist net data. Monthly line-transect censuses conducted over an annual cycle showed an increase in the detection of canopy frugivores and seed predators during the peak of flower and fruit availability in primary forest, but failed to suggest that second-growth or Eucalyptus stands provide suitable foraging habitat at any time of the year. The conservation value of both secondary forest and plantations was low compared to conclusions from previous studies. Our results indicate that while large-scale reforestation of degraded land can increase regional levels of diversity, it is unlikely to conserve most primary forest species, such as understorey insectivores and canopy frugivores.     

On the restoration of high diversity forests: 30 years of experience in the Brazilian Atlantic Forest

We present a review of more than 30 years of ecological restoration in the Brazilian part of the Atlantic Forest. Based on what has been done in this biome, we try to summarize the main findings and challenges for restoration in this highly threatened forest biome. We found that many past experiences did not result in self-perpetuating forests, for different reasons. Currently, most projects aim to construct self-sustaining communities and no longer see restoration as a deterministic process. We also found that the reconstruction of permanent forest with high diversity is feasible but it depends on the strategies applied and on the surrounding landscape. Although many new techniques have been created (e.g. seed rain management or promotion of natural regeneration), the most used one in the Atlantic Forest is still the planting of many native species from different functional groups. Native species are largely used and perform well even in highly disturbed environments. Today, many projects are trying to produce thousands of hectares of permanent forests and many technical advances are about to be incorporated. But restoration also faces some main challenges to become an effective and widespread means of conserving the Atlantic Forest which are, namely, reducing costs, planning restoration actions at landscape-level, and conforming to socio-political issues. The socio-political tools to overcome such barriers in practice have yet to be developed.     

巴西旱稻中稻栽培生态适应性研究

播种期的安排是水稻生产十分重要的措施.通过对引进的2个巴西旱稻品种(Iapar-9和Tangara)不同播种期的生态适应性研究,探讨了巴西旱稻的最佳播种期.结果表明:Iapar-9和Tangara在长沙地区的适宜播种期为5月10日左右,此时期播种产量最高;2个巴西旱稻品种不同播种期处理LAI和功能叶叶绿素含量变化总的趋势是齐穗期最大,随后逐渐减小;不同播种期处理齐穗期前根系活力差异不显著,齐穗期后根系活力随播种期的延迟而降低,且差异显著;每穗实粒数和结实率低是限制产量的主要原因.     

Fine root production and turnover in Brazilian Eucalyptus plantations under contrasting nitrogen fertilization regimes

Nitrogen fertilization increased largely over the last decade in tropical eucalypt plantations but the behaviour of belowground tree components has received little attention. Sequential soil coring and ingrowth core methods were used in a randomized block experiment, from 18 to 32 months after planting Eucalyptus grandis, in Brazil, in order to estimate annual fine root production and turnover under contrasting N fertilization regimes (120 kg N ha⁻¹ vs. 0 kg N ha⁻¹). The response of growth in tree height and basal area to N fertilizer application decreased with stand age and was no longer significant at 36 months of age. The ingrowth core method provided only qualitative information about the seasonal course of fine root production and turnover. Mean fine root biomasses (diameter <2 mm) in the 0–30 cm layer measured by monthly coring amounted to 0.91 and 0.84 t ha⁻¹ in the 0 N and the 120 N treatments, respectively. Fine root production was significantly higher in the 0 N treatment (1.66 t ha⁻¹ year⁻¹) than in the 120 N treatment (1.12 t ha⁻¹ year⁻¹), probably as a result of the greater tree growth in the control treatment throughout the sampling period. Fine root turnover was 1.8 and 1.3 year⁻¹ in the 0 N and the 120 N treatments, respectively. However, large fine root biomass (diameter <1 mm) was found down to a depth of 3 m one year after planting: 1.67 and 1.61 t ha⁻¹ in the 0 N and the 120 N treatments, respectively. Fine root turnover might not be insubstantial in deep soil layers where large changes in soil water content were observed.     

Genetic structure of plantations and the conservation of genetic resources of Brazilian pine (Araucaria angustifolia)

With growing concern about maintenance of genetic variation and conservation of gene resources, the question arises on the extent to which a planted population should be considered a resource able to preserve the gene pool of a species. In this study, levels of genetic diversity were assessed in natural and planted populations of Araucaria angustifolia using AFLPs and nuclear microsatellites, in order to assess the usefulness of planted forests in programs of species’ genetic resource conservation. In general, the genetic structure of the plantations was not strongly differentiated from the natural populations. For microsatellites, gene diversity (H) and allelic richness were significantly higher in plantations, while inbreeding was not different between planted and natural populations. For AFLPs, no significant difference was found between groups in the measures of genetic diversity. In the cluster analysis based on microsatellite data, plantations and natural populations from Santa Catarina State were grouped together, suggesting that plantations preserved genetic information very similar to natural populations. The cluster analysis of populations based on AFLP data differentiated plantations from natural populations. This pattern may be a result of genetic hitchhiking of AFLP fragments with genes under selective pressure due to plantations establishment and management. We suggest that the moderate to high level of genetic diversity retained in A. angustifolia populations after the intense fragmentation of the natural forest has the potential to supply plant material with sufficient genetic diversity for the species conservation through the establishment of planted forests. A sustainable management of the extant forest remnants and forestation/reforestation enterprises should additionally attend to trends revealed in previous studies concerning population structure and gene flow.     

Agroforestry adoption and maintenance: self-efficacy, attitudes and socio-economic factors

Agroforestry is a key land use in the development of ecological corridors in tropical rainforests biomes. This research tested the social dimensions of agroforestry adoption and maintenance in the Atlantic rainforest of Southern Bahia, Brazil. A quasi-experiment research design compared a group of farmers who participated in an agroforestry development program with a group of similar farmers who were not participants in the program. The effects of the program on the participants’ self-efficacy, attitudes and intentions to adopt or maintain agroforestry were tested. The effects of socio-economic factors and attitudes were also compared to self-efficacy in terms of farmers’ intentions to adopt or maintain agroforestry. Results indicate that the program neither raised nor lowered the farmers’ attitudes, self-efficacy or intentions to adopt or maintain agroforestry. However, multiple regression and logistic model analyses indicate that perceived behavioral control, attitudes about conservation and available labor contributed most significantly to farmers’ intentions to adopt or maintain agroforestry. Overall, perceived behavioral control proved to have the most significant correlation with farmers’ intentions to adopt or maintain agroforestry. Therefore, agroforestry development programs could benefit from focusing on farmers’ perceived control of certain behaviors to enhance the persistence of agroforestry practices.     

巴西农业生产与科研推广体系

文章简要介绍了巴西农业生产概况、农业科研体系和农业技术推广体系。