Effects of Land-Use Change on Soil Nutrient Dynamics in Amazônia

Over the past several decades, the conversion of native forest to agricultural land uses has accelerated across the Amazon Basin. Despite a growing body of research on nutrient dynamics in Amazonian primary forest and forest-derived land uses, the effects of widespread land-use change on nutrient contents and cycles in soil and vegetation are not well understood. We reviewed over 100 studies conducted in Amazônia over the past 40 years on nutrient dynamics in natural forests and forest-derived land uses (pasture, shifting cultivation, and tree plantations). Our objectives were to compare soil data from land uses across Amazônia and identify any gaps in our present knowledge that might offer direction for future research. Specifically, by analyzing data we tested the following five widely cited hypotheses concerning the effects of land-use change on soil properties compiled from 39 studies in multifactorial ANOVA models; (a) soil pH, effective cation exchange capacity (ECEC), and exchangeable calcium (Ca) concentrations rise and remain elevated following the slash-and-burn conversion of forest to pasture or crop fields; (b) soil contents of total carbon (C), nitrogen (N), and inorganic readily extractable (that is, Bray, Mehlich I, or resin) phosphorus (P_i) decline following forest-to-pasture conversion; (c) soil concentrations of total C, N, and P_i increase in secondary forests with time since abandonment of agricultural activities; (d) soil nutrient conditions under all tree-dominated land-use systems (natural or not) remain the same; and (e) higher efficiencies of nutrient utilization occur where soil nutrient pools are lower. Following the conversion of Amazonian forest to pasture or slash-and-burn agriculture, we found a significant and lasting effect on soil pH, bulk density, and exchangeable Ca concentrations. Unlike the other three land uses studied, concentrations of extractable soil P_i were equally low in both forest and pastures of all age classes, which demonstrates that postburning pulses in soil P_i concentration following a slash-and-burn decrease rapidly after forest-to-pasture conversion, perhaps due to accumulation in organic P fractions. Neither the concentrations nor the contents of total C and N appeared to change greatly on a regionwide basis as a result of forest-to-pasture conversion, but surface soil C:N ratios in 5-year-old pastures were significantly higher than those in older pastures, suggesting changes in the soil concentrations of at least one of these elements with time after pasture creation. Pasture soils did have higher total C and N concentrations than land uses such as annual cropping and secondary forest fallow, indicating that soil C and N maintenance and/or accumulation following forest conversion may be greater in pastures than in these other two land uses. The low concentrations of C and N in shifting cultivation soils appear to persist for many years in secondary forests regenerating from abandoned crop fields, suggesting that the recuperation of soil losses of C and N resulting during no-input annual cropping is slower than previously thought. Soil C, N and P concentrations were strongly related to clay content. Across all land uses, efficiencies of N, P, and Ca use (estimated as the inverse of litterfall N, P, and Ca contents) were not related to the sizes of their soil pools. More work is needed to test and standardize P extraction procedures that more accurately reflect plant availability. Few studies have been conducted to determine the role of organic P fractions and dissolved organic N (DON) in the elemental cycles of both natural and managed systems in this region. In general, we recommend further study of annual and perennial cropping systems, as well as more detailed examination of managed pastures and fallows, and secondary forests originating from various disturbances, since the intensity of previous land use likely determines the degree of soil degradation and the rate of subsequent secondary regrowth.     

Titi monkeys (Callicebus spp., Atelidae: Platyrrhini) in the Brazilian state of Rondônia

Five species of titi monkey (Callicebus brunneus, Callicebus caligatus Callicebus cinerascens, Callicebus donacophilus, andCallicebus moloch) were recorded in surveys of primate populations at 26 sites throughout the Brazilian state of Rondônia. The distribution of the two species,C. cinerascens andC. donacophilus (recorded in the state for the first time), appeared to be related to that of non-forest ecosystems, the former in thecerrado woodlands, and the latter in gallery forests of the Guaporé grasslands. The results of the surveys also indicate thatC. brunneus has a more restricted distribution in southern Rondônia than was previously thought, whereasC. moloch is more widespread. However, the ecological factors that determine species distribution in the south of the state remain unclear on the basis of the available data. All species were observed in small social groups of no more than five individuals, which are typical of the genus, generally in the middle and lower forest strate.     

Temporal changes of mangrove vegetation boundaries in Amazônia: Application of GIS and remote sensing techniques

The present work analyses a 25-year timeseries of radar and satellite images, andidentifies areas with losses and gains ofvegetation coverage along 166 km of Para'scoastline (North Brazil) and in the innerparts of the Bragança peninsula. Thegeomorphology of this region hassignificantly changed in recent years. Aresult of these changes has been a retreatof the mangrove vegetation along thecoastline, mainly due to landward sandmigration, which covers the mudflat andasphyxiates the vegetation. Image analysissuggests that the loss of vegetationcoverage has been the dominating process inthe last 25 years, occurring on 42% ofthe Bragança coastline and adjacentareas. Vegetation has remained stable along 39% of the coastline, while mudsedimentation has allowed mangrovedevelopment along 19% of it. On the otherhand, during this period of time, mangroveshave invaded 3.4 km² ( 38%) of theelevated herbaceous flats in the highestsectors of the Bragança peninsula.Despite other possible causes for mangrovedeath along the coastline, such as littoraldrift currents or cyclical changes incoastal sediment dynamics, the invasion ofmangrove into herbaceous elevated flats inthe central peninsula cannot be attributedto these factors. The current dynamics ofvegetation coverage change seem to becompatible with a long-term trend relatedto the predicted rates of sea-level rise.     

Land Use Patterns in the Brazilian Amazon: Comparative Farm-Level Evidence from Rondônia

Since the 1970s the Brazilian Amazon has received over 1 million migrant farm households from other regions of the country, many of whom were attracted to government-sponsored frontier settlement programs that offered free tropical forest land. As a result, pressures on tropical forests have intensified along several settlement corridors throughout the region. Despite their importance as agents of landscape change, surprisingly little is known about the land use practices of these farmers. This paper briefly reviews the research literature on smallholder land use patterns in Amazonia, describes the recent history of one important agricultural land settlement program in the western Brazilian Amazon state of Rondônia, and, based on 240 household surveys conducted in three separate settlement locations in the state, highlights key differences in land use patterns among the rural population. Typologies of farming systems are presented on the basis of cluster analysis of land use data and ANOVA tests. The findings indicate considerable complexity and heterogeneity in smallholder farming systems. Spatial variations in farming system types may be due to geographic differences in soil regimes, the social histories of specific communities, and site-specific responses to exogenous variables.     

Ecophysiological traits of plant functional groups in forest and pasture ecosystems from eastern Amazônia,Brazil

The plant functional group approach has the potential to clarify ecological patterns and is of particular importance in simplifying the application of ecological models in high biodiversity ecosystems. Six functional groups (pasture grass, pasture sapling, top-canopy tree, top-canopy liana, mid canopy tree, and understory tree) were established a priori based on ecosystem inhabited, life form, and position within the forest canopy profile on eastern Amazonian region. Ecophysiological traits related to photosynthetic gas exchange were then used to characterize such groups. The ecophysiological traits evaluated showed considerable variations among groups. The pasture grass functional group (a C₄ photosynthetic pathway species) showed high instantaneous water use efficiency (A _max/g _s@A _max), high photosynthetic nitrogen use efficiency (A _max/N _area), and high ratio of A _max to dark respiration (A _max/R _d). Among the species with the C₃ photosynthetic pathway, the top-canopy liana group showed the highest mean of A _max/g _s@A _max, statistically distinct from the lowest average presented by the understory tree group. Furthermore, the pasture sapling group showed the lowest average of A _max/R _d, statistically distinct from the high average observed for the understory tree group. Welch-ANOVAs followed by Games–Howell post hoc tests applied to ecophysiological traits produced reasonable distinctions among functional groups, although no significant distinction was detected between the groups top-canopy tree and pasture sapling. Species distribution within the functional groups was accurately reproduced by discriminant analyses based on species averages of ecophysiological traits. The present work convincingly shows that the functional groups identified have distinct ecophysiological characteristics, with the potential to respond differently to environmental factors. Such information is of great importance in modeling efforts that evaluate the effects of dynamic changes in tropical plant communities over ecosystem primary productivity.     

Tabanidae (Diptera) of Amazônia XX. description of Tabanus pseudonebulosus n.sp

Tabanus pseudonebulosus, new species, is described based on 217 female specimens and 5 males collected in Venezuela (Guarico, Aguaio, Santa Elena, and Palmarito) and in Brazil (Parcí: Santana do Araguaia, Serra das Andorinhas in S?o Geraldo do Araguaia, Serra Norte Carajás and Gorotire; Amazonas: Canutama; Mato Grosso do Sul: Corumbá), mostly in open vegetation, scrub forest and in rocky environments. Observed intraspecific variation in the specimens is presented and related to collection localities, and morphological differences are diagnosed in relation to the similar species Tabanus nebulosus DeGeer 1776 and T. importunus Wiedemann 1828. Morphometrical data and indices for specimens in different localities are provided. Drawings and photo of the new species are presented.     

Morphometric comparison of Simulium perflavum larvae (Diptera: Simuliidae) in relation to season and gender in Central Amazônia, Brazil

Number of larval instars, age structure and environmental effects on these parameters represent basic information in the study of insect population biology. When species have economic importance, this information is essential in order to choose the best period to apply different control methods and to determine the stages of the life cycle of the insect that are most susceptible to each treatment. The family Simuliidae has many species of medical/veterinary importance in the world, and some studies in the temperate region have suggested that the number of larval instars and the larval size can vary according to the season, gender and some environmental factors, such as temperature and diet. This study, with the zoophilic species Simulium perflavum Roubaud, is the first in the Neotropics observing some of these factors and will serve as a template for other species of medical importance in the region. S. perflavum larvae were collected in five streams in Central Amaz?nia (Manaus and Presidente Figueiredo counties, State of Amazonas), in Sept./Oct. 1996 (dry season) and Feb./Mar. 1997 (rainy season). These larvae were measured (lateral length of head capsule and width of cephalic apodema) to determine the number of larval instars (n=3985), to compare the larval size between seasons and genders (last and penultimate larval instars, n=200). Seven larval instars were determined for this species using frequency distributions, t-tests and Crosbys growth rule. Significant differences were not detected (t-test, p>0.05) in larval size between seasons and genders. Our results differ from some found in temperate regions suggesting that in the Neotropical region the larval size in different seasons and different genders remains constant, although some environmental parameters, such as diet, change depending on the season.     

Stomach content analyses of Simulium perflavum Roubaud 1906 (Diptera: Simuliidae) larvae from streams in Central Amazônia, Brazil

Stomach contents of Simulium perflavum Roubaud larvae were analyzed and compared with plankton and periphyton collected in five streams, in Central Amazonia (Manaus and Presidente Figueiredo counties), in Sep./Oct.1996 (dry season) and Feb./Mar. 1997 (rainy season). A total of 1,400 last-instar larvae were dissected; the stomach contents were analyzed using different methods: fresh and after oxidation. A total of 87 taxa (algae, diatoms and rotifers) were found in the stomach contents. In each stream, qualitative samples of plankton and periphyton were collected; these were mounted between slides and cover slips. A total of 94 taxa of plankton and 54 taxa of periphyton were collected. One species of Rotifera was present in the stomach contents, plankton and periphyton. Cluster analysis based on species composition of the organisms present in the stomach contents grouped the streams into two major groups, each belonging to a different drainage area. Correlations based on presence/absence of species of microalgae in the stomach contents, plankton and periphyton indicated significant associations (p<0.05) between stomach contents and plankton and between plankton and periphyton (z test); the Sorensen coefficient and cluster analysis corroborate the same associations.     

The role of the shrub Cordia multispicata Cham. as a ‘succession facilitator’ in an abandoned pasture,Paragominas, Amazônia

We studied the conditions that permit the shrub, Cordia multispicata, to establish in Amazon pastures and the potential role of this shrub as a succession facilitator near the town of Paragominas, Pará State, Brazil. Local disturbances that reduce cover such as grazing and burning helped C. multispicata establish in pastures in active use. Germination of C. multispicata was significantly improved on sites subjected to simulated grazing and seedling growth was hastened following pasture burning. We found that below-ground competition, evaluated using root ingrowth cores, was reduced by burning and grazing. Recently abandoned pastures are frequently composed of a mix of forbs and grasses but as succession proceeds a mosaic of more discrete vegetation patches appears. At our site, a five-year-old abandoned pasture, grass patches (primarily Panicum maximum) and shrub patches (mainly C. multispicata) were common. We compared physical and biotic characteristics of zones dominated by C. multispicata and P. maximum and found: (1) the rain of bat and bird dispersed seeds of woody species was much greater in the zones of C. multispicata (92 seeds/m²/year) than in the patches of grass (6 seeds/m²/year); (2) the density of woody seedlings was eight times greater in the C. multispicata patches (0.65/m²) than in the zones of P. maximum (0.08 woody individuals/m²); (3) soil nutrient availability and litter nutrient concentrations were greater in the shrub zones than in the grass zones; and (4) photosynthetic photon flux density at the soil surface was generally more favorable for rainforest tree seedling growth in C. multispicata patches (16% of full sunlight) as compared to the grass zones (7.7% of full sun). We conclude that the shrub, C. multispicata, acts as a magnet, attracting volant seed vectors, and as a nurse plant, facilitating the establishment of woody species in abandoned Amazon pastures.     

Recent observations on the sand fly (Diptera: Psychodidae) fauna of the State of Rondônia, Western Amazônia, Brazil: the importance of Psychdopygus davisi as a vector of zoonotic cutaneous leishmaniasis

Sand flies were collected in the central region of the state of Rond?nia (W 64 degrees 30' to 63 degrees 00' and S 10 degrees 00'to 11 degrees 00') using Shannon and CDC light traps from October 1997 to August 2000. A total of 85,850 specimens representing 78 named species were captured. Of these 14 were new records for Rond?nia. The proportion of males/females was 1/1.131. Trypanosomatids, that are presently being identified, were detected in 11 species. Leishmania (Viannia) naiffi was recorded from Psychodopygus davisi and P. hirsutus. In the present study the dominant species was P. davisi (39.6%) followed by Lutzomyia whitmani (13.1%), P. carrerai (11.6%), and P. hirsutus (10.2%). The importance of P. davisi as a vector of zoonotic cutaneous leishmaniasis is discussed.     

Population structure of the malaria vector Anopheles darlingi in Rondônia, Brazilian Amazon, based on mitochondrial DNA

Anopheles darlingi is the most important Brazilian malaria vector, with a widespread distribution in the Amazon forest. Effective strategies for vector control could be better developed through knowledge of its genetic structure and gene flow among populations, to assess the vector diversity and competence in transmitting Plasmodium. The aim of this study was to assess the genetic diversity of An. darlingi collected at four locations in Porto Velho, by sequencing a fragment of the ND4 mitochondrial gene. From 218 individual mosquitoes, we obtained 20 different haplotypes with a diversity index of 0.756, equivalent to that found in other neotropical anophelines. The analysis did not demonstrate significant population structure. However, haplotype diversity within some populations seems to be over-represented, suggesting the presence of sub-populations, but the presence of highly represented haplotypes complicates this analysis. There was no clear correlation among genetic and geographical distance and there were differences in relation to seasonality, which is important for malarial epidemiology.     

The forest-cerrado transition zone in southern Amazonia: Results of the 1985 Projeto Flora Amazônica expedition to Mato Grosso

An account of the history of collecting in the Mato Grosso is followed by a discussion of the current views on the nature of the vegetation along the transition from Amazonian forest to cerrado. The purpose of the 1985 Projeto Flora Amazônica expedition was to sample the vegetation in the transition region in northern Mato Grosso. In order to characterize the vegetation at the various localities, the identified collections were assigned to one of five broad distributional categories: Planaltine, Transitional, Amazonian, Wide-spread, or Other. In most cases, as expected, the collecting sites in the north and the west were characterized by Amazonian forest species while those in the south and east comprised mainly cerrado elements. Our collections show that the transition zone is a complex mosaic of Amazonian forest and cerrado formations.     

An autochthonous case of Echinococcus vogeli Rausch & Bernstein, 1972 polycystic echinococcosis in the state of Rondônia, Brazil

The present case report refers to a patient from the State of Rond?nia, North region of Brazil, attended with clinical suspicion of hepatic echinococcosis. Examination by imaging (ultrasonography and computerized tomography) revealed a conglomerate of cystic lesions, with mobile contents within the cyst. The serology (immunoblot) for Echinococcus sp. was positive (21 and 31 kDa bands). This case is the first reported in Rond?nia, suggesting the need to investigate the polycystic echinococcosis in individuals with hepatic cysts from areas of tropical forest and hunting habits where wild life was present as wild dogs, cats and rodents, particularly Agouti paca (paca) and Dasyprocta aguti (agouti).     

Effects of pasture introduction on soil CO2 emissions during the dry season in the state of Rondônia,Brazil

Soil CO₂ evolution rates, soil temperatures and moisture were measured during the dry season in two forest-to-pasture chronosequences in Rondônia, Brazil. The study included pastures ranging from 3 to 80 years-old. Mean dry-season CO₂ evolution from the forest in chronosequence 1, 88.8 mg CO₂-C m^–2h^–1 was lower than from the pastures which ranged from 111 to 158 mg CO₂-C m^–2h^–1. We found that temperature was not a good predictor of CO₂ emissions from pasture but that there was a significant relationship (r = 0.72,p < 0.05) between soil moisture and pasture emissions. The ¹³C of the soil CO₂ emissions also was measured on chronosequence I; ¹³C of the CO₂ emitted from the C3 forest was –29.43%. Pasture¹³CO₂ values increased from –17.91%. in the 3 year-old pasture to –12.86% in the 80 year-old, reflecting the increasing C₄ inputs with pasture age. Even in the youngest (3 year-old) pasture, 70 percent of the CO₂ evolved originated from C₄ pasture-derived carbon.     

Vegetation types of the upper Madeira River in Rondônia,Brazil

We characterize the vegetation types of the upper basin of the Madeira River in the Brazilan state of Rondônia, a biodiverse region with elevated rates of habitat loss. Vegetation and environmental parameters were recorded from 37 observation points distributed along and near a 160 km stretch of the Madeira River and representing the range of regional environments. Analysis of structure and floristic variables, as well as associated edaphic attributes and water table fluctuation, permitted recognition of five main vegetation types and seven subtypes. Open Ombrophilous Forest was the most frequently encountered vegetation type and occurred on well-drained, nutrient-poor soils, whereas Dense Ombrophilous Forest was seldom recorded. Alluvial Ombrophilous Forests (várzea) were found along a narrow strip of land along the banks of the Madeira River on the most fertile soils in the study area. Semideciduous Forests were found on small areas of rocky outcrops with shallow soils and reduced water availability during the dry season. Campinaranas, which range from open savanna physiognomies to closed canopy forests, were found to be a key environment in the lowlands south of the Madeira River on silty hydromorphic soils, where they harbor a peculiar flora tolerant of flooding during the rainy season. Our classification of the main vegetation types in the upper Madeira River illuminates a high degree of floristic and environmental heterogeneity in a highly threatened region. Our results will be useful for designing conservation strategies aimed at protecting the full range of floristic diversity present in the region.     

Commentary: The Rôle of Toxicology in Prevention and Precaution

Advocates of the Precautionary Principle have recently called for a “new science” to support the goals of precaution-based environmental and occupational health policy. While much attention has been given to epidemiology, the evidentiary science most relevant to precaution, or prevention, is toxicology. Opportunities for enhancing the rôle of toxicology in public policy must consider current biases in the field. Thus, rather than a “new science,” advocates for change should focus upon ensuring that current scientific methods are appropriate and that interpretations of scientific data are accurate.     

The rôle of vitamins in plant development

The Botanical Review -     

Electromagnetic fields in medicine – The state of art

ABSTRACT

Introduction: Intense development of methods belonging to physical medicine has been noted recently. There are treatment methods, which in many cases lead to reduction treatment time and positively influence on quality of life treatment patients. Research implications: The present physical medicine systematically extends their therapeutic possibilities. This above applies to illnesses and injuries of locomotor system, diseases affecting of soft tissues, as well as chronic wounds. The aim of the study: The evidence on this are the results of basic and clinical examinations relating the practical use of electromagnetic fields in medicine. Originality: In this work the authors introduced the procedure using the current knowledge relating to physical characteristic and biological effects of the magnetic fields. In the work the following methods were used: static magnetic fields, spatial magnetic fields, the variable magnetic fields both with laser therapy (magnetolaserotherapy) and variable magnetic fields both with light optical non-laser (magnetoledtherapy) talked.