Diversity, floristic composition, and structure of the woody vegetation of the Cerrado in the Cerrado–Amazon transition zone in Mato Grosso, Brazil

The final publication is available at Springer via http://dx.doi.org/10.1007/s40415-015-0186-2We compared the diversity and species composition and the structure of the vegetation of three distinct Cerrado phytophysiognomies (Cerradão, Dense Cerrado, and Typical Cerrado) in the Cerrado–Amazon transition, Mato Grosso (Brazil). Species richness (observed and estimated) in the Cerradão and Dense Cerrado was higher than that recorded in the Typical Cerrado. Species diversity, based on a Rényi profile, was highest in the Dense Cerrado, in comparison with the other phytophysiognomies. We recorded a higher number of exclusive species in the Cerradão and a greater similarity (Morisita and Sørensen indices) between this vegetation type and the Dense Cerrado. While individuals were tallest in the Cerradão and Dense Cerrado and lowest in the Typical Cerrado, there was no difference among phytophysiognomies in mean diameter. A gradient in decreasing species richness and diversity (hypothesis 1) and vegetation vertical structure (hypothesis 3) was expected for the Cerradão–Dense Cerrado–Typical Cerrado; however, neither hypothesis was supported by the results. The Cerradão and Dense Cerrado were most similar in species composition not confirming hypothesis 2, which predicted that the two savanna vegetation types (Dense Cerrado and Typical Cerrado) were more similar to one another than either is to the woodland (Cerradão). Overall, the similarities among the three study communities depended on the type of parameter analyzed. While the species richness and the vertical and structure of the vegetation of the Cerradão and Dense Cerrado are closely similar, the Cerradão and Typical Cerrado are more similar in their species diversity. With regard to the floristic composition, Dense Cerrado occupies an intermediate position between Cerradão and Typical Cerrado.UNEMAT Graduate Program in Ecology and ConservationBrazilian Higher Education Training Program (CAPES)“Tropical Biomes in Transition – TROBIT”CAPES/Science without Borders ProgramPELD/CNPq (Long-Term Ecological Studies)PROCAD UnB/UNEMA

A passagem do fogo resulta em mudanças de curto prazo para a fenologia vegetativa de espécies lenhosas em um cerrado stricto sensu

Avaliamos os efeitos do fogo sobre o comportamento fenológico vegetativo (cobertura de copa, brotação, folhas jovens e folhas adultas) de espécies lenhosas em dois sítios de cerrado sensu stricto: um queimado acidentalmente e outro não queimado. Usamos modelos aditivos mistos generalizados para testar a hipótese de que 1) o fogo danifica a cobertura de folhas das copas, o que resulta em alterações nos padrões fenológicos vegetativos das espécies; sendo isso verdadeiro, testamos se 2) os danos causados pelo fogo na cobertura de copa e nas folhas adultas são maiores em espécies sempre verdes do que em espécies decíduas e se 3) os efeitos negativos do fogo sobre a fenologia vegetativa persistem após um ano sem fogo. As duas primeiras hipóteses foram corroboradas, mas a terceira não. Os efeitos do fogo na cobertura de folhagem da copa e nas folhas adultas foram maiores após três meses da ocorrência do fogo e significativamente maiores para espécies sempre verdes. Para brotação e folhas jovens, as maiores diferenças foram entre três e sete meses após a queimada. Por outro lado, não foram percebidas diferenças entre os eventos fenológicos vegetativos dos sítios no segundo ano após a ocorrência do fogo, o que indica que os efeitos do fogo foram expressivos apenas por curto período. Os nossos resultados mostraram que o efeito do fogo sobre os eventos fenológicos vegetativos é negativo e mais intenso logo após a ocorrência da queimada, mas também que estes efeitos são temporários, e não são mais percebidos após o primeiro ano da ocorrência do fogo.We evaluated the effects of fire on the vegetative phenological behavior (crown foliage cover, sprouting, mature and young leaves) of woody species at two sites in the Brazilian savanna, one of which had been accidentally burned. We used generalized additive mixed models to test the hypothesis that: 1) fire damages total foliage cover, thus leading to changes in vegetative phenological patterns. As this hypothesis was corroborated, we also tested whether 2) the damage caused by fire to the total crown foliage cover and mature leaves is greater in evergreen than in deciduous species, and 3) the negative effects of fire on vegetative phenology persist after the first fire-free year. The first two hypotheses were corroborated, but the third was not. Fire effects on total crown foliage cover and mature leaves were greatest during the first three months following the fire, and were significantly greater in evergreen species. For shoots and young leaves, the greatest differences found between three and seven months post-fire. On the other hand, no differences were observed in phenological events between burned and unburned sites in the second year post-fire, indicating that marked effects of the fire were only observed over a short period. Our results showed immediate negative effects on the vegetative phenophases, but also that these effects are transient, and cannot be discerned after the first fire-free year

Fire in the Xingu region: its determinants and effects on vegetation and socio-environmental relevant resources

Slash-and-burning agricultural systems represent an important source of food for indigenous communities in Amazonia and have been conducted for centuries or millennia. However, the traditional use of fire has ignited an increasing number of wildfires. In 2010, for instance, 298,000 hectares of forests burned in the Xingu Indigenous Park (XIP). Yet, it is still unclear what are the main factors driving this apparent change in fire regimes inside the PIX, as well as the consequences of such changes to vegetation dynamics, ecosystem services, and food security for the indigenous communities. Here we describe the activities we are conducting on the scope of a project that aims to quantify the causes and consequences of changes in fire regimes inside the XIP and are funded by the Brazilian National Research Council (CNPq) and the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA). Objectives of the project include: 1) mapping burned areas inside the PIX over the past few decades using high-resolution imagery, differentiating those fire scars in slash-and-burn areas from wildfires in primary forests; 2) quantification of the combined roles of forest fires, droughts events, and forest management by indigenous peoples on recent changes of forest cover inside the XIP. Preliminary results indicate large areas on forest the XIP are now degraded mainly as a result of the increases in the burned area in the past two decades. The number of fire events in combination with number of drought years were the main predictors forest degradation. Overall, results of this project will contribute to a better understanding of the drivers of regional changes in fire regimes. We are also generating valuable information about management techniques that can reduce fire-related degradation of native forests and the ecosystem services that these forests provide for indigenous peoples, what can be used to improve food security for local communities of the PIX

Post-fire resprouting strategies of woody vegetation in the Brazilian savanna

Post-fi re response by vegetation may refl ect the severity of the damage suff ered, but we still know little about the species-specifi c nature of responses to fi re or their predictors. Here, we evaluated 26 woody species before and after a fi re event in an Cerrado sensu stricto area (typical Brazilian savanna-type) in order to evaluate mortality rates and the type of resprouting (epigeal, hypogeal or epigeal + hypogeal). We evaluated the relative importance of stem diameter, height, and bark thickness as predictors of the type of post-fi re resprouting, using a sequential logistic regression model (SLRM). Mortality was 4 %, while epigeal resprouting was recorded in 57 % of the individuals, hypogeal resprouting was recorded in 24 %, and epigeal + hypogeal resprouting in 15 %. Our SLRM analysis indicated that bark thickness, followed by stem diameter, were the best predictors of the type of resprouting. Th ere was a greater than 60 % probability that individuals with bark thicker than 1.6 cm resprouted only epigeally. Our results confi rm the resistance (low mortality) and resilience (high resprouting capacity) of the woody vegetation of the Cerrado sensu stricto to fi re, and that thick bark is an eff ective protection against fi re damage

Composição florística, diversidade e efeitos edáficos em duas comunidades de savanas rochosas na Amazônia e Cerrado, Brasil

Despite the uniqueness and reach of the flora from natural savannas in the Brazilian Amazon, and the existence of studies on its origin and diversity, there are no local studies associating floristic patterns with soil properties in savanna enclaves in the Amazon region of the state of Mato Grosso. Floristic composition and diversity were compared between a woody community from a rocky savanna inselberg in a transition region (RTS) between the two largest South American biomes (Cerrado-Amazon), and an enclave of rocky savanna in the Amazon (RAS), and the effects of soil properties were investigated. Floristic comparisons were also made between the two studied communities and two other rocky savanna communities near the Cerrado-Amazon transition. The flora and physical and chemical soil properties in twenty-five 20 × 20 m subplots (1 ha) in each community were sampled and georeferenced. An evident floristic distinction was found between the two studied communities, with low similarity values and a high number of indicator species. The observed and estimated richness and Rényi diversity profiles indicated lower species diversity in RAS than in RTS. Soils were found to be litholic, poorly drained, dystrophic, alic, extremely acidic, sandy and nutrient poor. Species composition and abundance was associated with soil properties in both communities. The clear difference in species composition and diversity between RTS and RAS seem to be shaped by soil properties, geographic isolation and floristic influence from the Cerrado and the Amazon. These results broaden the knowledge regarding the composition and diversity of woody plants of savannas in Amazonian enclaves and Cerrado inselbergs, and provide an important set of floristic and edaphic descriptors for the phytogeography of rocky savannas.Apesar da singularidade e extensão da flora de savanas naturais na Amazônia brasileira, e da existência de trabalhos sobre sua origem e diversidade, não há estudos locais que associam padrões florísticos com propriedades do solo em enclaves de cerrado na região amazônica no estado de Mato Grosso. Comparamos a composição florística e a diversidade entre uma comunidade lenhosa de um inselberg de savana rochosa em uma região de transição (STR) entre os dois maiores biomas sul-americanos (Cerrado-Amazônia) e um enclave de savana rochosa na Amazônia (SAR) e investigamos os efeitos das propriedades do solo. Além disso, comparamos as duas comunidades estudadas com outras duas comunidades de savanas rochosas próximos da transição Cerrado-Amazônia. A flora e as propriedades físicas e químicas do solo de vinte e cinco subparcelas de 20 × 20 m (1 ha), em cada comunidade foram amostradas e georreferenciadas. Uma evidente distinção florística foi encontrada entre as duas comunidades estudadas, com baixos valores de similaridade e um número elevado de espécies indicadoras. A riqueza observada e estimada e os perfis de diversidade de Rényi indicaram menor diversidade de espécies na SAR do que na STR. Os solos são litólicos, pouco drenados, distróficos, álicos, extremamente ácidos, arenosos e pobres em nutrientes em ambas as comunidades. A composição e a abundância de espécies foram associadas às propriedades do solo. A clara diferença na composição e diversidade entre STR e SAR parecem ser moldadas pelas propriedades do solo, isolamento geográfico e influências florísticas do Cerrado e Amazônia. Esses resultados ampliam o conhecimento sobre a composição e diversidade de plantas lenhosas de savanas em enclaves da Amazônia e inselbergs do Cerrado e fornecem um importante conjunto de descritores florísticos e edáficos para a fitogeografia de savanas rochosas

Deep soils modify environmental consequences of increased nitrogen fertilizer use in intensifying Amazon agriculture

Agricultural intensification offers potential to grow more food while reducing the conversion of native ecosystems to croplands. However, intensification also risks environmental degradation through emissions of the greenhouse gas nitrous oxide (N2O) and nitrate leaching to ground and surface waters. Intensively-managed croplands and nitrogen (N) fertilizer use are expanding rapidly in tropical regions. We quantified fertilizer responses of maize yield, N2O emissions, and N leaching in an Amazon soybean-maize double-cropping system on deep, highly-weathered soils in Mato Grosso, Brazil. Application of N fertilizer above 80 kg N ha−1 yr−1 increased maize yield and N2O emissions only slightly. Unlike experiences in temperate regions, leached nitrate accumulated in deep soils with increased fertilizer and conversion to cropping at N fertilization rates \u3e80 kg N ha−1, which exceeded maize demand. This raises new questions about the capacity of tropical agricultural soils to store nitrogen, which may determine when and how much nitrogen impacts surface waters

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio