Savanna Physiognomies Research Articles

Disentangling the roles of resource availability and disturbance in fine and coarse root biomass in savanna

Savannas are among the most unknown biomes concerning the plant below-ground system. Root biomass might be influenced by the availability of limiting resources and by the type and intensity of disturbances, mediated by the plant functional attributes related to environmental conditions. Fine and coarse roots should be affected differently: the former should be more responsive to resource supplies, whilst the latter should be related to changes in disturbance frequency. We studied the roles of soil fertility, topography of the plots indicating water availability, fire frequency and plant resistance to fire in affecting fine and coarse root biomass. We sampled the root biomass, environmental variables and functional attributes of all individuals present in 100 plots in savanna physiognomies of cerrado, in central Brazil. We used structural equation modelling to test our hypothesis and found that shallow root biomass, from 0 to 20 cm deep, was not caused by resource availability, by disturbances, as fire or drought, or by functional attributes. Biotic interactions were not considered in our study, but they may have a central role in affecting the shallow root biomass. In the deep layer, from 20 to 100 cm deep, we identified soil fertility and recent fires as the main factors causing changes in fine and coarse root biomass in the cerrado, respectively. Low nutrient availability in the soil caused higher fine root biomass, increasing the uptake of resources, whereas recent fires led to less coarse root biomass below 20 cm deep, probably due to the higher dominance of the herbaceous layer in the plots, with less coarse root biomass. According to our expectation, fine roots were mostly affected by nutrient availability in the soil, whereas coarse roots were more related to disturbance, in our case, recent fires.

Root behavior of savanna species in Brazil’s Pantanal wetland

The objective of this study was to determine the maximum depth, structure, diameter and biomass of the roots of common woody species in two savanna physiognomies (savanna woodland and open woody savanna) in Brazil’s Pantanal wetland. The root systems of 37 trees and 34 shrubs of 15 savanna species were excavated to measure their length and depth and estimate the total root biomass through allometric relationships with stem diameter at ground level. In general, statistical regression models between root weight and stem diameter at ground level showed a significance of P<0.05 and R2 values close to or above 0.8. The average depths of the root system in wetland savanna woodland and open woody savanna are 0.8±0.3m and 0.7±0.2m, respectively, and differ from the root systems of savanna woody species in non-flooding areas, whose depth usually ranges from 3 to 19 m. We attribute this difference to the adaptation of woody plant to the shallow water table, particularly during the wet season. This singularity of woody species in wetland savannas is important when considering biomass and carbon stocks for national and global carbon inventories.

Natural history of Micrablepharus maximiliani (Squamata: Gymnophthalmidae) in a Cerrado region of northeastern Brazil

Micrablepharus maximiliani (Reinhardt & Luetken, 1861) is a microteiid lizard widely distributed in the open areas of South America. Little is known about its ecology and reproductive biology. Here, we analyzed aspects of the natural history of a population of M. maximiliani from a Cerrado area in the state of Piauí, northeastern Brazil. Our results suggest that the reproductive activity of M. maximiliani might be seasonal in the Cerrado, since reproductive females were observed only in the dry season, whereas reproductive males were present in both seasons. Vitellogenic follicles and oviductal eggs were found simultaneously in one female, suggesting that females may produce more than one clutch per season. Sexual dimorphism was observed in body shape, and individuals were mainly restricted to a typical savanna physiognomy. The diet consisted of small arthropods, including spiders, crickets and cockroaches as the most important items.

O gênero Stylosanthes (Leguminosae) em Roraima, Brasil

Stylosanthes faz parte do clado Pterocarpus, tribo Dalbergiae. Possui 50 espécies distribuídas mundialmente e é principalmente diverso em áreas savânicas do Brasil. Este trabalho apresenta o estudo taxonômico do gênero Stylosanthes para o Estado de Roraima. Foram analisados materiais provenientes de trabalho de campo e de materiais depositados em herbário. Sete espécies foram encontradas em todas as fitofisionomias de savanas do estado: S.capitata, S.angustifolia, S. gracilis, S. viscosa, S. humilis, S. guianensis e S. scabra. São apresentadas chave de identificação, descrições e ilustrações, bem como informações sobre distribuição geográfica, ambientes preferenciais e usos econômicos das espécies.

Comparative effects of desiccation, heat shock and high temperatures on seed germination of savanna and forest tree species

Although forest and savanna biomes predominate in tropics regions, the factors that control their distribution remain unclear. South American savannas occur in regions that are considered warm and humid enough to support forests, indicating that agents other than climate determine the occurrence of one or the other physiognomy. Herbivory, fire and water deficit have been considered environmental filters that limit the forest species encroachment in savanna physiognomies, but the effects of these filters on the capability of these species to recruit from seeds remain poorly understood. In this study we investigated how stress factors characteristic of savanna environments, such as soil desiccation, heat shocks and high temperatures affect the survival and germination of seeds from savanna and forest tree species. We found that desiccation (to 5%) reduced the germination percentage of forest seeds, but had no effect on the germination of savanna seeds. Forest seeds were less tolerant to heat shocks of 140°C and 200°C, and showed lower germination percentage at temperatures of 35 and 40°C, when compared with savanna seeds. Savanna seeds presented longer germination times and higher germination variance than forest seeds, indicating a risk-spreading germination strategy among savanna species. The low tolerance of forest seeds to desiccation, heat shock and high temperatures may explain the low recruitment of forest trees into savanna physiognomies. Climate change models predict lower soil moisture, higher temperatures and higher fires frequency for South America biomes. Our results suggest that savanna species are likely to be more capable of withstanding the effects of these changes than forest species.

Demography and growth of subadult savanna trees: interactions of life history, size, fire season, and grassy understory

Tree populations in mesic (&gt;650 mm precipitation/yr) savannas of the world have strong demographic bottlenecks to the transition of subadult trees to the canopy layer. Although such bottlenecks are a major determinant of savanna physiognomy, the factors that allow subadults to traverse the bottleneck are little studied. In a landscape‐scale field experiment in a northern Australia savanna, we determined the survival and growth of 1506 permanently marked juveniles (&lt;150 cm tall) and saplings (150–599 cm tall) of canopy species in response to season of fire (early dry season, late dry season, wet season, and unburned), and understory type (herbaceous forbs vs. sorghum [native annual grass]) that differ in seasonal growth patterns and competitive regimes. Trees were assessed before fires and at the end of the following growing season, without repeat fires. We used Akaike‐information‐criterion‐based model selection and multi‐model inference for data analyses. Initial height was an important explanatory variable for all responses except genet mortality wherein fire season was important for juveniles and understory type for saplings. Fire season was important to height growth of large juveniles and small saplings (enhanced the year following dry‐season fires). Fire season × understory interactions were important for height growth of small juveniles and for the proportion of juveniles transitioning to saplings. Changes in stem numbers were affected by all explanatory variables. All fires topkilled most juveniles (fewer in early dry‐season fires in herbaceous understory), but genet death was rare. Late dry‐season fires topkilled most saplings; they failed to regain previous height and some died the following year. Given no further fires, persistent large juveniles can grow to sapling size within a year; whereas sapling success is severely hampered by late‐dry‐season fires, especially in grassy understory. Differences in seasonal phenological patterns of both understory vegetation and trees that vary with size and life history stage are among suggested explanatory mechanisms. Weighted averaged model coefficients for all responses to the explanatory variables are provided for use in population dynamics models. A conceptual framework links landscape‐scale variables to tree attributes and responses, with implications for population ecology and community assembly.

Optimal Shrub Density for Bird Habitat in the Midwestern United States

Shrubs play a key role as bird habitat in eastern North America and are associated with a group of songbirds that are in sharp decline in the Midwest region, U.S.A. Savanna restoration throughout the region is a key priority for vegetation managers, and a priority goal is often to clear the understory of woody species encroachment, including shrubs. However, while the benefit of maintaining a shrub layer in restored savanna has been noted by wildlife managers, the degree to which native shrubs should be retained has not yet been quantified. In this study, I measured songbird occurrence in sites that met the criteria of savanna physiognomy and that have shrub cover ranging from 10 to ≥75%. The results indicated that the highest overall species richness and richness of species conservation concern occurred when shrub cover was =35%. This observation suggests that shrub cover in the range of 10-35% may be adequate to conserve declining shrub dependent bird species, while also meeting the objective of opening the understory desired by savanna restoration practitioners.

Heat shock effects on seed germination of five Brazilian savanna species

Fire is considered an important factor in influencing the physiognomy, dynamics and composition of Neotropical savannas. Species of diverse physiognomies exhibit different responses to fire, such as population persistence and seed mortality, according to the fire frequency to which they are submitted. The aim of this study is to investigate the effects of heat shocks on seed germination of Anadenanthera macrocarpa (Benth.) Brenan, Dalbergia miscolobium Benth., Aristolochia galeata Mart. & Zucc., Kielmeyera coriacea (Spreng.) Mart. and Guazuma ulmifolia Lam., which are native species of the Brazilian savanna. The temperatures and exposure times to which the seeds were submitted were established according to data obtained in the field during a prescribed fire: 60 °C (10, 20 and 40 min), 80 °C (5, 10 and 20 min) and 100 °C (2, 5 and 10 min). Untreated seeds were used as controls. Seeds of A. galeata and K. coriacea showed high tolerance to most heat treatments, and seeds of A. macrocarpa showed a significant reduction in germination percentage after treatments of 80 °C and 100 °C. Treatments of 100 °C for 10 min reduced germination percentage for all species except G. ulmifolia, which has dormant seeds. For this species, germination was accelerated by heat treatments. The high temperatures applied did not interfere with the time to 50% germination (T(50) ) of the tolerant seeds. Seeds of the savanna species K. coriacea and A. galeata were more tolerant to heat shocks than seeds of the forest species A. macrocarpa. Guazuma ulmifolia, the forest species with seeds that germinate after heat shock, also occurs in savanna physiognomies. Overall, the high temperatures applied did not affect the germination rate of the tolerant seeds.

Biological functioning of Brazilian Cerrado soils under different vegetation types

Over a 2 year period, we compared the soil biological functioning (SBF) of Cerrado physiognomies ranging from grassland-savannic to forest formations, sampling in the middle of the dry and rainy seasons. Soil samples were collected at two depths (0 to 5 cm and 5 to 20 cm) under the following physiognomies: Campo Sujo, Cerrado Ralo, Cerrado sensu stricto, Cerradao and Mata de Galeria. The SBF was represented by the simultaneous analyses of microbial biomass carbon, soil basal respiration and the activity of enzymes linked to the C, P and S cycles (β-glucosidase, acid phosphatase and arylsulfatase, respectively). The results demonstrated that Cerrado physiognomies are a major determinant of SBF patterns. The forest-like physiognomies (Mata de Galeria and Cerradao) presented the highest biomass and activity compared to the grassland (Campo Sujo) and savanna physiognomies (Cerrado Ralo and Cerrado sensu stricto). These differences were more evident in the topsoil layer (0 to 5 cm), and the seasonal effect on the SBF of the Mata de Galeria and Cerradao was more pronounced than on the other physiognomies. These results provide a benchmark for evaluating changes in SBF and related processes in Cerrado areas due to shifts toward agriculture and cattle production.

A continental analysis of correlations between tree patterns in African savannas and human and environmental variables

This study analyses possible relationships between natural processes taking place in savannas and the tree patterns found in savannas. This can lead to new hypotheses about which processes are driving savanna physiognomy. To do so tree patterns were quantified for African savannas from historical aerial photographs applying frequently used landscape metrics. Also, additional data for these areas were collected to quantify the processes taking place at these locations. Correlations between tree pattern indices and explaining factors were analysed. We found a negative trend between tree cover and density of sheep and goats, but no relationship between tree cover and density of cattle, suggesting that small livestock have an effect on tree cover, but that larger livestock (or obligate grazers) do not. Also, a positive correlation between human population density and tree cover was found. Possible explanations for the found relations are discussed. Subsequent ways to analyse the latter correlation are discussed, and the potential of the presented historical database of aerial photographs is highlighted.

Spatial-temporal distribution of fire-protected savanna physiognomies in Southeastern Brazil

The analysis of the influence of edaphic finer textures, as a facilitating factor for the expansion of forest formations in the absence of fire, was possible thanks to rare characteristics found in a savanna fragment located in the State of São Paulo, Brazil. The total suppression of fire for over four decades, and the occurrence of two savanna physiognomies, cerrado sensu stricto and cerradão, allowed the conduction of this study based on the hypothesis that cerradão, a physiognomy of forest aspect consisting of fire-sensitive tree and shrubs species, is favored by fire absence and higher soil hydric retention capacity. Edaphic samples were collected from a regular grid of 200 m(2) for the production of isopletic maps of the distribution of clay, fine sand, coarse sand and silt edaphic textures by the geostatistic method of ordinary kriging. Changes in the areas occupied by both savanna physiognomies, defined on the basis of aerial photographs taken over a period of 43 years, were assessed through mean variation rates. Besides corroborating the hypothesis of edaphic hydric retention as a facilitating factor for the expansion of forest physiognomies in savanna areas, we were able to infer the positive influence of higher precipitation on the increase in cerradão expansion rates.

Classificação de padrões de savana usando assinaturas temporais NDVI do sensor MODLS no Parque Nacional Chapada dos Veadeiros

A savana é o principal tipo de vegetação no Brasil Central, cobrindo aproximadamente 23% do território nacional. Localmente é conhecido como Cerrado, sendo formado por um mosaico de fisionomias tais como Campo, Campo Cerrado e Cerrado que possuem um ciclo fenológico típico. Neste contexto, os dados do MODIS fornecem medidas diárias que permitem monitorar a fenologia sazonal da vegetação. O presente trabalho objetiva avaliar o emprego de assinaturas temporais para detectar tipos de savanas no Parque Nacional da Chapada dos Veadeiros. A metodologia adotada pode ser subdividida nos seguintes passos: (a) elaboração do cubo 3D das imagens temporais NDVI-MODIS, onde o perfil em z corresponde à assinatura temporal, (b) tratamento do ruído pela combinação das técnicas de Filtro de mediana e o Minimum Noise Fraction, (c) detecção dos membros finais utilizando o invólucro convexo, e(d) classificação espectral usando o método Spectral Correlation Mapper. Os resultados demonstram que as fisionomias do Cerrado apresentam assinaturas temporais típicas. Os membros finais correspondem aos três maiores domínios fisionômicos: (a) Campo, região com dominio do extrato herbáceo; (b) Cerrado, uma mistura de campo e arbustos; e (c) Cerrado Denso, densamente coberto por árvores. Comparações com imagem Landsat 7/ETM+ demonstram a eficiência da classificação das séries temporais. O estudo concluiu que as séries NDVI são úteis na diferenciação dos tipos de vegetação. A eficiência da metodologia tem sido provada para delimitação regional das fisionomias de savana, mesmo considerando abaixa resolução espacial de 250m do sensor MODIS e a alta mistura espectral.

Nutritional adaptations of native plants of the cerrado biome in acid soils

Soils of the cerrado biome, mostly oxisols and deep sandy entisols, are acid, dystrophic and poor in available nutrients. These soils are not very different from soils that occur in the Amazon region. However, the open savanna physiognomies of cerrado with lower biomass of their different components are deficient in nutrients at the ecosystem level, unlike the Amazon forests which retain high nutrient reserves in their live biomass. Field crops are susceptible to aluminum and manganese toxicities, besides nutrient deficiencies, in cerrado soils and do not grow well in the absence of liming and fertilization. However, concepts of nutrient deficiencies and toxicities, well established for cultivated plants, should not be extended to native species in natural ecosystems, indiscriminately. Many native plants in the cerrado biome are resistant or tolerant to soil conditions deemed unfavorable for cultivated plants but their geographic distribution, frequency in native communities, growth and productivity are determined by water and nutrient availability and other edaphic conditions. Species growing on acid soils are aluminum tolerant or resistant, since their capacity to absorb essential nutrients, growth and reproduction is not affected by high aluminum levels in the soil. Many common species of the cerrado, instead of excluding aluminum, absorb and transport it to leaves and accumulate it in different tissues including leaves and seeds whereas others do not survive in the absence of exchangeable aluminum, even though no specific role of Al in plant metabolism is yet established.

POST-FIRE RESPROUTING AND MORTALITY IN CERRADO WOODY PLANT SPECIES OVER A THREE-YEAR PERIOD

The objective of this work was to evaluate resprouting features and mortality in Cerrado woody plants after annual controlled fires (in 1998, 1999 and 2000) in a campo sujo area (an open savanna physiognomy) of 2500 m2 at the Reserva Ecológica do IBGE, Brasília-DF, Brazil. The area was protected against fire for 23 years prior to the fires. All plants of the woody layer with diameter larger than 2.0 cm at 30 cm from soil level were tagged and identified. At about one year after each controlled fire the damage type and the number of basal and underground sprouts for each individual were recorded. Stem diameter and height were measured for each marked sprout. A total of 1307 sprouts were tagged and measured. The main impact of fire on resprouting was a decrease in the number of new sprouts after each controlled fire: 684 sprouts after the first burning to 248 after the third burning. Mortality of sprouts was 34.8% and 37.8% after the 1999 and 2000 fires. A decrease in the number of sprouts with a diameter smaller than 1.0 cm after the successive fires was also observed, indicating that fires at one-year intervals resulted in alterations in the structure of the woody vegetation in the area. The species mortality rates were higher after the first controlled fire. However, it seems that there is no relation between sprouting capacity and species survival. The species that show mortality rates lower than 10% also showed a variety of sprouting capacity.

Anthropogenic disturbance and the formation of oak savanna in central Kentucky, USA

AbstractAim To deepen understanding of the factors that influenced the formation of oak savanna in central Kentucky, USA. Particular attention was focused on the link between historical disturbance and the formation of savanna ecosystem structure.Location Central Kentucky, USA.Methods We used dendrochronological analysis of tree‐ring samples to understand the historical growth environment of remnant savanna stems. We used release detection and branch‐establishment dates to evaluate changes in tree growth and the establishment of savanna physiognomy. We contrasted our growth chronology with reference chronologies for regional tree growth, climate and human population dynamics.Results Trees growing in Kentucky Inner Bluegrass Region (IBR) savanna remnants exhibited a period of suppression, extending from the establishment date of the tree to release events that occurred c. 1800. This release resulted in a tripling of the annual radial growth rate from levels typical of oaks suppressed under a forest canopy (&lt; 1 mm year−1) to levels typical of open‐grown stems (3 mm year−1). The growth releases in savanna trees coincided with low branch establishment. Over the release period, climatic conditions remained relatively constant and growth in regional forest trees was even; however, the growth increase in savanna stems was strongly correlated with a marked increase in Euro‐American population density in the region.Main conclusions Our data suggest that trees growing in savanna remnants originated in the understorey of a closed canopy forest. We hypothesize that Euro‐American land clearing to create pasturelands released these trees from light competition and resulted in the savanna physiognomy that is apparent in remnant stands in the IBR. Although our data suggest that savanna trees originated in a forest understorey, this system structure itself may have been a result of an unprecedented lack of Native American activity in the region due to population loss associated with pandemics brought to North America by Euro‐Americans. We present a hypothetical model that links human population dynamics, land‐use activities and ecosystem structure. Our model focuses on the following three land‐use eras: Native American habitation/utilization; land abandonment; and Euro‐American land clearance. Ecological understanding of historical dynamics in other ecosystems of eastern North America may be enhanced through recognition of these eras.

Cerrado vegetation study using optical and radar remote sensing: two Brazilian case studies

The amount of phytomass is a crucial parameter in ecology as a whole. Conventional methods to estimate phytomass parameters are often prohibitive in terms of time, environment, and manpower. Seasonality in Brazilian savanna physiognomies is marked by green leaves lost during the dry season and regrowth during the wet season. Branches and trunks remain the same through the seasons. The amounts of the phytomass components can be estimated by nondestructive methods using remote sensing. This paper presents case studies where the abilities to predict vegetation variation are tested using optical and radar images. The foliar component leaf area index (LAI) obtained in the field is related to the normalized difference vegetation index (NDVI) obtained from satellite images, and both methods present a strong relationship with green leaves biomass. Japanese Earth Resources Satellite (JERS-1) images are used to estimate the aboveground woody biomass. Campo cerrado physiognomy showed the highest seasonal variation in NDVI, and cerradão the lowest variation in NDVI. During August, the lower the NDVI values, the lower the solar albedo and the higher the photosynthetically active radiation (PAR) albedo. During November, the higher the NDVI values, the lower the PAR and the higher the solar albedo. The same proportion in seasonal variation was observed with LAI values. A significant equation is proposed to estimate trunk and branch biomass using allometric parameters and JERS-1 backscattering.

Análise da dinâmica sazonal e separabilidade espectral de algumas fitofisionomias do cerrado com índices de vegetação dos sensores MODIS/TERRA e AQUA

Composições de 16 dias de índices de vegetação do sensor MODerate resolution Imaging Spectroradiometer (MODIS), com resolução espacial de 1km, a bordo dos satélites TERRA e AQUA, foram usadas para caracterizar a dinâmica sazonal em 2004 de cinco fitofisionomias de Cerrado e analisar a sua separabilidade espectral. Os índices Normalized Difference Vegetation Index (NDVI) e Enhanced Vegetation Index (EVI), calculados a partir dos dados dos sensores de ambas as plataformas e de uma base comum de pixels, foram comparados entre si. Os resultados indicaram que: (a) dentre as fitofisionomias estudadas, a Floresta Estacional decídua apresentou uma dinâmica sazonal muito marcante em função da perda de folhas da estação chuvosa para a seca (substancial redução nos índices) e do rápido verdejamento com o início da precipitação no final de outubro (rápido incremento de NDVI e EVI); (b) o NDVI mostrou maior variabilidade entre as classes de vegetação do que o EVI apenas na estação seca; (c) a discriminação entre as fitofisionomias melhorou da estação chuvosa para a seca; (d) o NDVI foi mais eficiente do que o EVI para discriminar as classes de vegetação na estação seca, ocorrendo o contrário na estação chuvosa; e (e) na maioria das datas selecionadas para estudo, não houve diferenças estatisticamente significativas entre os índices de vegetação gerados de ambas as plataformas, apesar das variações na qualidade dos pixels selecionados para as composições de 16 dias e na geometria de iluminação e de visada.

Variations in reflectance with seasonality and viewing geometry: Implications for classification of Brazilian savanna physiognomies with MISR/Terra data

Bidirectional Reflectance Factor (BRF) data, collected at nine view angles, four bands and six dates by the Multi-angle Imaging SpectroRadiometer (MISR), were used to characterize the seasonality and viewing geometry effects on the discrimination of five selected physiognomies of a specific Brazilian savanna environment. Spectral–angular profiles for each physiognomy (Seasonal, Dry and Pluvial Forests; Arboreous and Park Savanna) were obtained from nadir-normalized BRF data at each MISR band and date of image acquisition. The maximum likelihood classification technique was applied at each camera and date using a common set of pixels as training samples. A reference map was used as ground truth to obtain the classification accuracy for each physiognomy, view angle and date. Results showed that the surface anisotropy signatures of the savanna physiognomies were not unique and varied with Sun-view geometry and seasonality. Directional effects increased from data collected in the orthogonal plane to those acquired close to the solar principal plane, and with increasing Sun zenith angles. Such effects were also affected by seasonality due to differences in the dynamics of the vegetation response to precipitation, as indicated by the Fraction of Photosynthetically Active Radiation (FPAR) and Leaf Area Index (LAI) values. Dry Forest presented a faster rate of “green-up” in the beginning of the rainy season and more abrupt changes in LAI values earlier in the dry season than the other physiognomies. In relation to the nadir response, the strongest anisotropy was observed in the backward scattering direction and in the red band at large Sun zenith angles. Directional effects were also observed after the Normalized Difference Vegetation Index (NDVI) determination. Classification accuracy of vegetation improved from the rainy to the dry season. The exception was Park Savanna, which was also well discriminated from the other physiognomies in the beginning of the rainy season due to the spectral effects of non-photosynthetic vegetation (dry grass understore) that produced an increase in the red reflectance. In general, classification accuracy of the physiognomies improved also from the forward to the backward scattering direction. The best view angles for classification purposes ranged from 0° (nadir) to − 45.6°, and were associated with viewing directions of maximum backscattering at the different dates. In comparison with single view direction results, the use of Anisotropy Index (ANIX) images produced a general decrease in classification accuracy values. Results indicated that off-nadir viewing can improve discrimination and mapping of major physiognomies in the Brazilian savanna environment.

Influence of soil fertility on the distribution of tree species in a deciduous forest in the Triângulo Mineiro region of Brazil

Dry semideciduous and deciduous forests occur only on calcium-rich soils and occupy almost 20% of the 200 million ha of the cerrado region of central Brazil. Other savanna physiognomies of woodlands and grasslands, and gallery forests generally occur on acid soils with low calcium levels. The literature on phytosociological aspects of such cerrado physiognomies is quite abundant whereas there is very little information on deciduous forests. Also lacking is information on soil fertility and its influence on species distribution. The objective of the present study was to study the distribution of native species within a dry deciduous forest in the Araguari river valley, Uberlândia, Minas Gerais as related to soil properties. A 1-ha sampling area, with no apparent difference in physiognomy, was divided into fifty 10 m × 20 m plots arrayed in 10 × 5 grid and all trees with a minimum circumference of 15 cm at 1.30 m height were surveyed. A composite soil sample was collected from 0 to 10 cm depth in each plot and soil pH, organic C and nutrient availability were determined. Cluster analysis based on soil chemical properties showed the existence of two distinct groups of plots. Further field examinations revealed that the forest was situated in an area of transition between mica schist and basalt parent materials, without any apparent difference in the forest physiognomy. The basalt-derived soil in 23 plots had significantly higher availability of Ca (47.0 cmol(+) kg−1 soil), Mg (2.59), and K (0.96) than the mica schist derived soil (Ca—18.4, Mg—1.29, and K—0.66) in the remaining 27 plots, though both soils would be classified as eutrophic. A total of 59 species belonging to 27 families were encountered in the area as a whole, of which 36 were common to both soils. In total, 16 species occurred exclusively on the mica schist soil and 7 on the basaltic soil. Myracrodruon urundeuva Allem. (Anacardiaceae) and Tabebuia roseo-alba (Ridl.) Sandwith (Bignoniaceae) were species with high importance values in the forest as a whole. Though there was no significant difference in the diversity index between the two soils, the importance values of these species was larger in the basalt-derived soil with higher nutrient availability.

Identificação regional da Floresta Estacional Decidual na bacia do Rio Paranã a partir da análise multitemporal de imagens MODIS

Parana river basin has one of the major fragments of Decidual Seasonal Forest in Brazil. This vegetation is widely fragmented due to the selective wood exploitation and the growth of pasture areas, what justifies the development of studies in order to understand its dynamics and preserve its diversity. Thus, the present study aimed at defining a method for regional identification of the Deciduous Forest in the Parana river basin. The deciduous forest has a typical phenological cycle in comparison with other savanna physiognomies. Due these characteristics, a temporal series of normalized difference vegetation index (NDVI) images of the MODIS sensor was used for its detection. The adopted methodology may be subdivided into the following steps: (a) elaboration of the 3D cube of NDVI images, where the z profile corresponding to temporal signature or NDVI spectrum, (b) noise elimination using the Minimum Noise Fraction (MNF) transformation, and (c) NDVI temporal variability examination of deciduous forest vegetation, with the establishment of the best NDVI band applied in the vegetation index differencing method. The Deciduous Forest presents a typical NDVI spectral behaviour, with higher values in the raining season and lower values in the dry season, what makes this kind of vegetation different from others. The employment of a changing detection algorithm between two images: one for the dry season and the other for the raining season enhances the localization of the Decidual Seasonal Forest. So, the methodology has proved to be effective for regional delimitation of Deciduous Forests considering the MODIS sensor. Considering the changing detection method, Deciduous Forest region is characterized by presenting NDVI alteration values.