Produção, acúmulo e decomposição da serapilheira em uma restinga da Ilha do Mel, Paranaguá, PR, Brasil

Em uma formação de restinga na Ilha do Mel, Paranaguá-PR, foram avaliadas, mensalmente, a serapilheira produzida e a acumulada, em quadrados de 0,25 m², durante um ano (julho/1996-junho/1997). A decomposição, mensal e anual, foi estimada, indiretamente, pela razão entre serapilheira produzida e acumulada. A produção anual de serapilheira de 5,1 t.ha-1 encontra-se no limite inferior aos obtidos em outras florestas tropicais, e decorre, provavelmente, do solo arenoso e pobre em nutrientes. A produção e a decomposição foram sazonais, mais intensa durante o período mais quente e chuvoso, estando relacionadas, principalmente, à temperatura. O pequeno acúmulo de serapilheira (5,5t.ha-1.ano -1), e a ausência de variações mensais significativas neste compartimento denotam o sincronismo entre estes processos, que, aliado a taxa de decomposição anual relativamente baixa (kL = 0,92), representa grande valor adaptativo para o ecossistema, pois, pode minimizar as perdas por lixiviação e permitir um melhor aproveitamento dos nutrientes e água disponíveis momentaneamente. Tais mecanismos, bem como o caráter perenifólio das espécies, escleromorfia, e uma rede de raízes superficiais, possibilitam o desenvolvimento da comunidade vegetal sob as condições oligotróficas do solo. Estes, além do clima, parecem exercer uma forte influencia na determinação dos padrões de produção e decomposição da serapilheira.

Amazon forest structure generates diurnal and seasonal variability in light utilization.

The complex three-dimensional (3-D) structure of tropical forests generates a diversity of light environments for canopy and understory trees. Understanding diurnal and seasonal changes in light availability is critical for interpreting measurements of net ecosystem exchange and improving ecosystem models. Here, we used the Discrete Anisotropic Radiative Transfer (DART) model to simulate leaf absorption of photosynthetically active radiation (lAPAR) for an Amazon forest. The 3-D model scene was developed from airborne lidar data, and local measurements of leaf reflectance, aerosols, and PAR were used to model lAPAR under direct and diffuse illumination conditions. Simulated lAPAR under clear-sky and cloudy conditions was corrected for light saturation effects to estimate light utilization, the fraction of lAPAR available for photosynthesis. Although the fraction of incoming PAR absorbed by leaves was consistent throughout the year (0.80?0.82), light utilization varied seasonally (0.67?0.74), with minimum values during the Amazon dry season. Shadowing and light saturation effects moderated potential gains in forest productivity from increasing PAR during dry-season months when the diffuse fraction from clouds and aerosols was low. Comparisons between DART and other models highlighted the role of 3-D forest structure to account for seasonal changes in light utilization. Our findings highlight how directional illumination and forest 3-D structure combine to influence diurnal and seasonal variability in light utilization, independent of further changes in leaf area, leaf age, or environmental controls on canopy photosynthesis. Changing illumination geometry constitutes an alternative biophysical explanation for observed seasonality in Amazon forest productivity without changes in canopy phenology.

Diferencia de daños por herbívoros entre hojas jóvenes de color rojo y verde, ¿podría tratarse de mimetismo vegetal?

La presencia de coloración roja en las hojas jóvenes de algunas especies vegetales en los bosques tropicales podría servir como una señal para los herbívoros de la presencia de defensas químicas en las mismas, que tendría como consecuencia el escape al daño por los herbívoros. Los objetivos específicos de este trabajo fueron comparar entre hojas jóvenes verdes y rojas: a) los niveles de daño por herbívoros, b) la dureza y c) la aceptabilidad de tejido vegetal por herbívoros generalistas (saltamontes Vellea mexicana). Las hojas jóvenes rojas presentaron significativamente menor daño por herbívoros que las hojas jóvenes verdes; la dureza fue también significativamente menor en las hojas jóvenes rojas, mientras que la aceptabilidad de follaje por herbívoros no mostró diferencia significativa entre los dos tipos de hojas. Se sugiere que la coloración roja podría representar una estrategia efectiva de baja inversión de recursos que estaría permitiendo a las vulnerables hojas jóvenes escapar al daño causado por los herbívoros.

Periodicidade do crescimento de espécies arbóreas da Floresta Estacional Semidecidual no Sul do Brasil.

Embora a sazonalidade climática seja menos evidente nas regiões tropicais que nas temperadas, muitas espécies tropicais apresentam crescimento rítmico. A avaliação do crescimento em circunferência do tronco (CCT) permitirá obter informações sobre o desenvolvimento dos indivíduos de espécies arbóreas desta região. Esse estudo teve como objetivo avaliar o CCT de 11 espécies arbóreas de uma floresta estacional semidecidual no sul do Brasil, visando testar duas hipóteses: (i) existe sazonalidade no CCT das árvores e este crescimento está relacionado às variações climáticas da região de estudo; (ii) as características dos indivíduos (posição sociológica, altura da árvore, grau de ocupação por lianas, deciduidade e diâmetro à altura do peito) influenciam no incremento acumulado em circunferência. Para detectar a periodicidade do CCT foram implantadas faixas dendrométricas permanentes no tronco (altura do DAP) de 156 indivíduos. O acompanhamento do crescimento foi realizado mensalmente por um período de 18 meses. Foram feitas correlações do CCT mensal com a precipitação, temperatura e fotoperíodo para verificar a influencia dos fatores ambientais e análise de covariância para averiguar se as características dos indivíduos também interferiram no incremento acumulado em circunferência do tronco. As espécies apresentaram um padrão sazonal de CCT, com as maiores taxas de crescimento de outubro a dezembro, sendo que os parâmetros ambientais avaliados atuaram em conjunto - principalmente o fotoperíodo e a temperatura - promovendo essa sazonalidade e confirmando a primeira hipótese. Considerando as características dos indivíduos, somente o diâmetro do tronco correlacionou-se negativamente com o incremento acumulado em circunferência (b = -0,32; p = 0,02), aceitando parcialmente a segunda hipótese.

Sustainable forest management for smallholder farmers in the Brazilian Amazon.

The paper describes a forest management system to be applied on smallholder farms, particularly on settlement projects in the Brazilian Amazon. The proposed forest management system was designed to generate a new source of family income and to maintain forest structure and biodiversity. The system is new in three main characteristics: the use of short cycles in the management of tropical forests, the low harvesting intensity and environmental impact, and the direct involvement of the local population in ali forest management activities. It is based on a minimum felling cycle of ten years and an annual timber harvest of 5-10 m3 ha-1.

A INFLUÊNCIA DO ESTOQUE DE MATÉRIA ORGÂNICA DO SOLO EM FRAGMENTOS FLORESTAIS DE MATA ATLÂNTICA

In the Atlantic forest biome, very fragmented and with high diversity of ecosystems, of species, and high endemism degree, the maintenance of the status of the biological diversity presupposes the recovery and conservation of the mosaic of existent fragments. In that context, the use of global functional indicators for the evaluation of the state of conservation of fragments, for the character of systemic synthesis that they act becomes interesting. In tropical forests ecosystems, the surface organic matter stock of the soil is one functional indicator of the decomposition subsystem and they are responsible in big measured by the maintenance and survival of the communities of those ecosystems group. The human action when fragmenting the forest ecosystems, as it substitutes the native forest for different forms of use of the soil, it creates different head offices that they exercise pressures differentiated on the fragment and, consequently, on the operation of the fundamental processes of the ecosystem that represents it. Thus, in the sense of understanding the state of functional conservation of fragments forest remainders of the Atlantic forest, in the extent of the Environmental Protection Area of Petrópolis - Rio de Janeiro, which interferes in the Mosaic of Units of Conservation of the Fluminense Central Atlantic forest and, in a larger scale still, in the Ecological Corridor of the Serra do Mar, in the present study the stock of organic matter of surface of four forest fragments in summer of 2008 and summer of 2009 are analyzed comparatively.

A methodological framework to assess the carbon balance of tropical managed forests.

Background: Managed forests are a major component of tropical landscapes. Production forests as designated by national forest services cover up to 400 million ha, i.e. half of the forested area in the humid tropics. Forest management thus plays a major role in the global carbon budget, but with a lack of unified method to estimate carbon fluxes from tropical managed forests. In this study we propose a new time- and spatially-explicit methodology to estimate the above-ground carbon budget of selective logging at regional scale. Results: The yearly balance of a logging unit, i.e. the elementary management unit of a forest estate, is modelled by aggregating three sub-models encompassing (i) emissions from extracted wood, (ii) emissions from logging damage and deforested areas and (iii) carbon storage from post-logging recovery. Models are parametrised and uncertainties are propagated through a MCMC algorithm. As a case study, we used 38 years of National Forest Inventories in French Guiana, northeastern Amazonia, to estimate the above-ground carbon balance (i.e. the net carbon exchange with the atmosphere) of selectively logged forests. Over this period, the net carbon balance of selective logging in the French Guianan Permanent Forest Estate is estimated to be comprised between 0.12 and 1.33 Tg C, with a median value of 0.64 Tg C. Uncertainties over the model could be diminished by improving the accuracy of both logging damage and large woody necromass decay submodels. Conclusions: We propose an innovating carbon accounting framework relying upon basic logging statistics. This flexible tool allows carbon budget of tropical managed forests to be estimated in a wide range of tropical regions

From slum to suburbia : examining a spectrum of planned and unplanned urban morphology in humid sub-tropical regions of the world

The current rapid urban growth throughout the world manifests in various ways and historically cities have grown, similarly, alternately or simultaneously between planned extensions and organic informal settlements (Mumford, 1989). Within cities different urban morphological regions can reveal different contexts of economic growth and/or periods of dramatic social/technological change (Whitehand, 2001, 105). Morpho-typological study of alternate contexts can present alternative models and contribute to the present discourse which questions traditional paradigms of urban planning and design (Todes et al, 2010). In this study a series of cities are examined as a preliminary exploration into the urban morphology of cities in ‘humid subtropical’ climates. From an initial set of twenty, six cities were selected: Sao Paulo, Brazil; Jacksonville, USA; Maputo, Mozambique; Kanpur, India; Hong Kong, China; and Brisbane, Australia. The urban form was analysed from satellite imagery at a constant scale. Urban morphological regions (types) were identified as those demonstrating particular consistant characteristics of form (density, typology and pattern) different to their surroundings when examined at a constant scale. This analysis was correlated against existing data and literature discussing the proliferation of two types of urban development, ‘informal settlement’ (defined here as self-organised communities identifiable but not always synonymous with ‘slums’) and ‘suburbia’ (defined here as master planned communities of generally detached houses prevalent in western society) - the extreme ends of a hypothetical spectrum from ‘planned’ to ‘spontaneous’ urban development. Preliminary results show some cities contain a wide variety of urban form ranging from the highly organic ‘self-organised’ type to the highly planned ‘master planned community’ (in the case of Sao Paulo) while others tend to fall at one end of the planning spectrum or the other (more planned in the cases of Brisbane and Jacksonville; and both highly planned and highly organic in the case of Maputo). Further research will examine the social, economical and political drivers and controls which lead to this diversity or homogeneity of urban form and speculates on the role of self-organisation as a process for the adaptation of urban form.

Allocasuarina tree hosts determine the spatial distribution of hypogeous fungal sporocarps in three tropical Australian sclerophyll forests

Across three tropical Australian sclerophyll forest types, site-specific environmental variables could explain the distribution of both quantity (abundance and biomass) and richness (genus and species) of hypogeous fungi sporocarps. Quantity was significantly higher in the Allocasuarina forest sites that had high soil nitrogen but low phosphorous. Three genera of hypogeous fungi were found exclusively in Allocasuarina forest sites including Gummiglobus, Labyrinthomyces and Octaviania, as were some species of Castoreum, Chondrogaster, Endogone, Hysterangium and Russula. However, the forest types did not all group according to site-scale variables and subsequently the taxonomic assemblages were not significantly different between the three forest types. At site scale, significant negative relationships were found between phosphorous concentration and the quantity of hypogeous fungi sporocarps. Using a multivariate information theoretic approach, there were other more plausible models to explain the patterns of sporocarp richness. Both the mean number of fungal genera and species increased with the number of Allocasuarina stems, at the same time decreasing with the number of Eucalyptus stems. The optimal conditions for promoting hypogeous fungi sporocarp quantity and sporocarp richness appear to be related to the presence and abundance of Allocasuarina (Casuarinaceae) host trees. Allocasuarina tree species may have a higher host receptivity for ectomycorrhizal hypogeous fungi species that provide an important food resource for Australian mycophagous animals.

Rainfall changes over tropical montane cloud forests of southern Western Ghats, India

The southern Western Ghats tropical montane cloud forest sites (Gavi, Periyar, High wavys and Venniyar), which are characterized by frequent or seasonal cloud cover at the vegetation level, are considered one of the most threatened ecosystems in India and the world. Three out of four montane cloud forest sites studied in the southern Western Ghats had experienced diminishing trends of seasonal average and total rainfall, especially during summer monsoon season. The highest level of reduction for summer monsoon season was observed at Gavi rainforest station (>20 mm/14 years) in Kerala followed by Venniyar (>20 mm/20 years) site in Tamil Nadu. Average annual and total precipitation increased during the study period irrespective of the seasons over Periyar area, and the greatest values were recorded for season 2 (>25 mm/28 years). Positive trends for winter monsoon rainfall has been observed for three stations (Periyar, High wavys and Venniyar) except Gavi, and the trend was positive and significant (90%) for Periyar and High wavys. Increase in summer monsoon rainfall was observed for Periyar site and the trend was found to be significant (95%).

Monitoring Indigenous Tropical Montane Forests in the Taita Hills Using Airborne Digital Camera Imagery

The loss and degradation of forest cover is currently a globally recognised problem. The fragmentation of forests is further affecting the biodiversity and well-being of the ecosystems also in Kenya. This study focuses on two indigenous tropical montane forests in the Taita Hills in southeastern Kenya. The study is a part of the TAITA-project within the Department of Geography in the University of Helsinki. The study forests, Ngangao and Chawia, are studied by remote sensing and GIS methods. The main data includes black and white aerial photography from 1955 and true colour digital camera data from 2004. This data is used to produce aerial mosaics from the study areas. The land cover of these study areas is studied by visual interpretation, pixel-based supervised classification and object-oriented supervised classification. The change of the forest cover is studied with GIS methods using the visual interpretations from 1955 and 2004. Furthermore, the present state of the study forests is assessed with leaf area index and canopy closure parameters retrieved from hemispherical photographs as well as with additional, previously collected forest health monitoring data. The canopy parameters are also compared with textural parameters from digital aerial mosaics. This study concludes that the classification of forest areas by using true colour data is not an easy task although the digital aerial mosaics are proved to be very accurate. The best classifications are still achieved with visual interpretation methods as the accuracies of the pixel-based and object-oriented supervised classification methods are not satisfying. According to the change detection of the land cover in the study areas, the area of indigenous woodland in both forests has decreased in 1955 2004. However in Ngangao, the overall woodland area has grown mainly because of plantations of exotic species. In general, the land cover of both study areas is more fragmented in 2004 than in 1955. Although the forest area has decreased, forests seem to have a more optimistic future than before. This is due to the increasing appreciation of the forest areas.

Vegetative phenology of tropical montane forests in the Nilgiris, South India

Spatial and temporal variation in foliar phenology plays a significant role in growth and reproduction of a plant species. Foliar phenology is strongly influenced by environmental factors such as rainfall. A study on phenology of tropical montane forests was undertaken in three different forest patches of the Nilgiri Mountains in peninsular India above 2000 meters ASL. Since August 2000, 500 trees belonging to 70 species of angiosperms were monitored for both vegetative and reproductive phenologies on a monthly basis. Climate data were collected from nearby weather stations. This paper reports results of the study from August 2000 - August 2003 on foliar phenology. Non-parametric correlations and multiple regressions were performed to analyse the influence of environmental factors such as rainfall, temperature and sunshine on foliar phenology. It was found that moisture related factors had a negative influence on the leaf initiation. Circular statistical analyses were performed to understand the seasonality in different phenophases of foliar phenology. Different phenophases of leafing were not significantly seasonal. Results are discussed and compared among three different forest patches on the Nilgiri plateau and also with other montane forest patches across the globe.

Impact of Disturrance on Composition, Structure, And Floristics of Tropical Moist Forests in Uttara Kannada District, Western Ghats, India

Impact of disturbance on forest stand density, basal area, dbh class distribution of density and basal area, species richness, species diversity and similarity index was assessed through monitoring six, one-hectare, permanent forest plots after a period of 24 years in tropical moist forests of Uttara Kannada district, Western Ghats, India. It was observed that all sites lost trees due to removal by people and mortality. Loss of trees was more in sites that are easily accessible and closer to human habitation. In spite of a decrease in tree density, an increase in basal area was observed in some forest plots, which could be on account of stimulatory growth of surviving trees. Decrease in basal area in other sites indicates greater human pressure and overexploitation of trees. Preponderance of lower girth class trees, and a unimodal reverse `J-shaped' curve of density distribution as observed in majority of the sites in the benchmark year, was indicative of regenerating status of these forests. The decrease in number of species in all forest sites was due to indiscriminate removal of trees by people, without sparing species with only a few individuals, and also due to mortality of trees of rare species. Higher species richness and diversity in the lowest dbh class in most of the sites in the benchmark year is indicative of the existence of favorable conditions for sylvigenesis. The decrease in the similarity index suggests extirpation of species, favoring invasion and colonization by secondary species. To minimize human pressure on forests and to facilitate regeneration and growth, proper management planning and conservation measures are needed.