Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge, 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 organism 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 neglected 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 lost

Selectivity of Herbicides to Cabbage (Brassica oleracea var. capitata)

The presence of weeds in commercial fields of cabbage may interfere directly and indirectly on yield and on the quality of the commercial product. Therefore, the satisfactory production depends on a successful control of weeds. Because of the limited availability of herbicides registered in Brazil for cabbage crop in addition to the lack of information in the literature, the objective of this work was to evaluate the selectivity of herbicides to cabbage. The herbicides S-metolachlor (1,740 and 768 g ha-1), oxyfluorfen (240 and 96 g ha-1), flumioxazin (40 and 40 g ha-1) clomazone (720 and 360 g ha-1) and oxyfluorfen + flumioxazin (240 + 20 and 96 + 20 g ha-1) were applied before and after transplant of seedlings, besides the S-metolachlor + flumioxazin (768 + 20 g ha-1) mixture applied after transplant. The experiment was developed in the field, in a randomized block design with four replications. Weed control and cabbage crop injury were evaluated as well as the number of productive and suppressed cabbage plants, the average fresh mass of heads and yield. All herbicide treatments controlled weeds in the area satisfactorily; however, most of them caused high toxicity in plants with the exception of oxyfluorfen, applied before transplant, and flumioxazin and S-metolachlor, applied after transplant, which caused little leaf injury in plants. Oxyfluorfen applied before and after transplant and S-metolachlor, applied after transplant did not affect the number of productive and suppressed plants nor yield, being selective in cabbage.A presença de plantas daninhas em áreas comerciais de repolho pode interferir direta e indiretamente na produtividade e na qualidade do produto comercial. Nesse sentido, a produção satisfatória depende do controle bem sucedido das infestantes. Diante da limitada disponibilidade de herbicidas registrados no Brasil para a cultura do repolho, aliada à escassez de informações na literatura, objetivou-se neste estudo avaliar a seletividade de herbicidas ao repolho. Os herbicidas S-metolachlor (1.740 e 768 g ha-1), oxyfluorfen (240 e 96 g ha-1), flumioxazin (40 e 40 g ha-1), clomazone (720 e 360 g ha-1) e oxyfluorfen + flumioxazin (240 + 20 e 96 + 20 g ha-1) foram aplicados antes e após o transplante das mudas, respectivamente, e a mistura S-metolachlor + flumioxazin (768 + 20 g ha-1), após o transplante. O experimento foi desenvolvido em campo, no delineamento em blocos casualizados com quatro repetições. O controle de plantas daninhas e a toxicidade da cultura do repolho foram avaliados, além do número de plantas produtivas e suprimidas de repolho, a massa fresca média de cabeça e a produtividade. Todos os tratamentos com herbicidas resultaram no controle satisfatório das plantas daninhas na área. Contudo, a maioria causou toxicidade elevada às plantas, com exceção de oxyfluorfen, aplicado antes do transplante, e flumioxazin e S-metolachlor, aplicados após o transplante, que provocaram poucos sintomas visuais nas plantas. Oxyfluorfen, aplicado antes e após o transplante, e S-metolachlor, aplicado após o transplante, não afetaram o número de plantas produtivas e suprimidas nem a produtividade, sendo seletivos ao repolho

The Allelopathic Effect of Eucalyptus Leaf Extract on Grass Forage Seed

This study aimed to evaluate the allelopathic effect of various concentrations of an aqueous extract of eucalyptus leaves on Urochloa decumbens and Panicum maximum seeds. The extract was prepared from Eucalyptus urograndis leaves that were milled and mixed with distilled water in a 1:9 milled leaves: water ratio to obtain an extract with a defined concentration of 100%. In addition, dilutions of 50%, 25% and 12.5% were prepared, and a 0% dilution was used as a control. The experiment followed a completely randomized design, with four replicates, each of 50 seeds of U. decumbens and 50 seeds of P. maximum, arranged on filter paper moistened with each concentration of extract in a Gerbox plastic box. The results demonstrated the allelopathic potential of E. urograndis aqueous extracts applied to the seeds of U. decumbens and P. maximum. The 50% and 100% concentrations of leaf extract most strongly inhibited the germination, vigor and seedling growth of U. decumbens and P. maximum. The germination speed index and the root length were the characteristics that were most affected by the potentially allelopathic substances contained in the eucalyptus extracts at all concentrations

Soil microorganisms and their role in the interactions between weeds and crops

The competition between weeds and crops is a topic of great interest, since this interaction can cause heavy losses in agriculture. Despite the existence of some studies on this subject, little is known about the importance of soil microorganisms in the modulation of weed-crop interactions. Plants compete for water and nutrients in the soil and the ability of a given species to use the available resources may be directly affected by the presence of some microbial groups commonly found in the soil. Arbuscular mycorrhizal fungi (AMF) are able to associate with plant roots and affect the ability of different species to absorb water and nutrients from the soil, promoting changes in plant growth. Other groups may promote positive or negative changes in plant growth, depending on the identity of the microbial and plant partners involved in the different interactions, changing the competitive ability of a given species. Recent studies have shown that weeds are able to associate with mycorrhizal fungi in agricultural environments, and root colonization by these fungi is affected by the presence of other weeds or crops species. In addition, weeds tend to have positive interactions with soil microorganisms while cultures may have neutral or negative interactions. Competition between weeds and crops promotes changes in the soil microbial community, which becomes different from that observed in monocultures, thus affecting the competitive ability of plants. When grown in competition, weeds and crops have different behaviors related to soil microorganisms, and the weeds seem to show greater dependence on associations with members of the soil microbiota to increase growth. These data demonstrate the importance of soil microorganisms in the modulation of the interactions between weeds and crops in agricultural environments. New perspectives and hypotheses are presented to guide future research in this area

Lixiviação de sulfentrazone, isoxaflutole e oxyfluorfen no perfil de três solos

O destino de herbicidas aplicados em pré-emergência das plantas daninhas varia de acordo com o solo. Dessa forma, objetivou-se avaliar a lixiviação dos herbicidas sulfentrazone, isoxaflutole e oxyfluorfen no perfil de três solos. As doses de 0,5 e 0,75 kg ha-1 de sulfentrazone, 0,113 e 0,169 kg ha-1 de isoxaflutole e 0,72 e 1,08 kg ha-1 de oxyfluorfen foram aplicadas na superfície de colunas de PVC de 30 cm de altura preenchidas com três solos: um franco-arenoso e dois argilosos com teores alto (9,0 dag kg-1) e baixo (4,4 dag kg-1) de matéria orgânica. Após a aplicação, foram simuladas duas chuvas de 40 mm cada, com intervalo de 24 horas, respeitando o período de infiltração em cada solo. A lixiviação dos herbicidas ao longo do perfil dos solos foi verificada pelo método de bioensaio utilizando plantas de sorgo (Sorghum bicolor). A atividade herbicida do sulfentrazone e a movimentação no perfil dos solos foram elevadas na maior dose aplicada. A maior movimentação descendente do produto, na dose de 0,75 kg ha-1 de sulfentrazone, foi constatada no solo de textura franco-arenosa até 27,5 cm, seguido pelos solos de textura argilosa com baixo e alto teor de matéria orgânica até 25 e 17,5 cm, respectivamente. Verificou-se elevado potencial de lixiviação do isoxaflutole, ultrapassando a profundidade de 22,5 cm nos três solos estudados e nas duas doses aplicadas, diferentemente do oxyfluorfen, que permaneceu adsorvido nas camadas superficiais dos solos. Ao comparar os solos, maior atividade herbicida e movimentação ocorreram naquele de textura franco-arenosa. Em relação aos herbicidas, o isoxaflutole apresentou maior mobilidade do que o sulfentrazone, enquanto o oxyfluorfen mostrou baixo potencial de lixiviação