Mapping density, diversity and species-richness of the Amazon tree flora

Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees

Crioconservação de sementes de seis acessos de maracujazeiro

The cryoconservation has become an interesting alternative for the conservation of germplasm. Researched the seed conservation of passion fruit under two environments: laboratory (25ºC) and liquid nitrogen (-196ºC). Six accesses from IAC germplasm were studied: Passiflora serrato-digitata L., P. nitida Kunth. and four P. edulis Sims. genotypes (yellow, purple, small-purple, rose-apple). Seeds from the mature fruits were processed and evaluated in different moisture contents. Each treatment was composed of 400 seeds in four repetitions of 50 units each. The seed cryoconservation effects were evaluated by standard germination test (STG) and by the following tests of vigor: first counting of the STG (%), to the 7 days, length of seedling (cm) and emergency (%), to the 30 days. It was verified that the cryoconservation significantly affected the seeds quality of the P. edulis Sims. For this species, occurred improvement in the seeds germination and the seedlings emergency of yellow and rose-apple genotypes. For P. serrata-digitata seeds, similar results were 14 obtained to two treatments, showing germination below of 12%. Already, P. nitida seeds had the poorest % germination, independent of moisture contents. For these two last species will necessity of other searches to test cryprotectors for better seed conservations in ultra-low temperatures.A crioconservação em nitrogênio líquido transformou-se numa alternativa interessante e oportuna para a conservação de germoplasma vegetal. Neste trabalho pesquisou-se a conservação de sementes de maracujazeiro sob dois ambientes: laboratório (25ºC) e nitrogênio líquido (-196ºC). Utilizaram-se sementes, com variados teores de umidade, dos seguintes acessos do Banco Ativo de Germoplasma-Passiflora do IAC: Passiflora serrato-digitata L., P. nitida Kunth. e quatro genótipos de P. edulis Sims. (maracujás amarelo, roxo, rosa-maçã e roxinho-miúdo). Uma parte das sementes foi submetida à secagem, em estufa com circulação de ar a 32 4°C, para redução e uniformização da umidade até 20%. Os tratamentos foram esquematizados em fatorial 2 x 6 x 2, sendo o primeiro fator composto pela umidade inicial das sementes e umidade reduzida a 20%, o segundo fator pelos acessos de maracujazeiro e o terceiro fator pelo ambiente de armazenamento (ambiente de laboratório e criopreservação). O delineamento utilização foi o inteiramente casualizado. Cada tratamento constou de uma amostra de 200 sementes, divididas em 4 repetições de 50 sementes. Após 10 dias, as sementes não desidratadas e desidratadas foram congeladas em nitrogênio líquido e retiradas após 10 dias, sendo descongeladas sucessivamente à temperatura de -20ºC e de 5ºC, durante 24 horas cada. Os tratamentos foram avaliados pelo teste de germinação padrão (TPG, %), aos 7 dias e pelos testes de vigor: comprimento de plântula (cm) e emergência em viveiro(%), aos 30 dias. Verificou-se que a crioconservação afetou significativamente a qualidade das sementes de P. edulis. Para essa espécie, ocorreu melhoria na germinação das sementes dos maracujás amarelo e rosa-maçã. Para P. serratadigitata, as sementes se comportaram de forma similar em todos os tratamentos, mostrando germinação abaixo de 12%. As sementes de P. nitida não germinaram independente dos tratamentos. Para estas duas últimas espécies haverá necessidade de se pesquisar os variados tipos de crioprotetores para melhor conservação das sementes em condições de temperaturas ultra-baixas

Soil tillage systems: changes in soil structure and crop response

The introduction and intensification of no-tillage systems in Brazilian agriculture in recent decades have created a new scenario, increasing concerns about soil physical properties. The objective of this study was to assess the effects of different tillage systems on some physical properties of an Ultisol previously under native grassland. Five tillage methods were tested: no-tillage (NT), chiseling (Ch), no-tillage with chiseling every two years (NTCh2), chiseling using an equipment with a clod-breaking roller (ChR) and chiseling followed by disking (ChD). The bulk density, macroporosity, microporosity and total porosity, mechanical resistance to penetration, water infiltration into the soil and crop yields were evaluated. The values of soil bulk density, mechanical resistance to penetration and microporosity increased as macroporosity decreased. Soil bulk density was lower in tillage systems with higher levels of tillage/soil mobilization; highest values were observed in NT and the lowest in the ChD system. The water infiltration rate was highest in the ChR system, followed by the systems ChD, NT and NTCh2, while crop yields were higher in systems with less soil mobilization