<b>Interference of weeds on seedlings of four neotropical tree species

Abstract

Seasonal semideciduous forests in southeastern Brazil have experienced intensive fragmentation, and the interference of weeds may affect the dynamics of restored communities. The purpose of this study was to determine if there were specific densities of the weeds Urochloa decumbens and Ipomoea grandifolia at which the growth of seedlings of four Neotropical tree species -Senegalia polyphylla and Enterolobium contortisiliquum (Fabaceae) and Ceiba speciosa and Luehea divaricata (Malvaceae) -would be negatively affected. A randomized experimental design was conducted in a greenhouse, with five treatments to each tree species (different weed densities per pot per tree species) and four replicates per treatment. After the weeds flowered, the height and stem diameter of seedlings were quantified, including the aboveground dry biomass and the percentages of macro and micronutrients contents in the leaves. The growth of the tree seedlings was affected by the lowest weed density (two weeds per pot) when interacting with U. decumbens or I. grandifolia. In general, significant decreases in the percentage of macro and micronutrients in the leaves were observed, especially at eight weeds/pot. Such results could warrant experimental practices in chemical control in conjunction with alternative methods to control of these two weeds in restored areas.Interferência de plantas daninhas em mudas de quatro espécies arbóreas neotropicais RESUMO. As florestas estacionais semideciduais do sudeste do Brasil têm experimentado intensa fragmentação e a interferência de plantas daninhas influencia a dinâmica das comunidades restauradas. O objetivo deste estudo foi testar se o aumento das densidades de plantas daninhas (Urochloa decumbens e Ipomoea grandifolia) afetava o crescimento de mudas de quatro espécies de árvores neotropicais -Senegalia polyphylla e Enterolobium contortisiliquum (Fabaceae), Ceiba speciosa e Luehea divaricata (Malvaceae). O delineamento experimental foi inteiramente casualizado: cinco tratamentos por espécie (diferentes densidades de plantas daninhas por vaso, por espécie de árvore) e quatro repetições por tratamento. Após o florescimento das plantas daninhas, quantificaram-se a altura, o diâmetro do caule, a biomassa aérea seca e as porcentagens de conteúdo de macro e micronutrientes nas folhas das espécies arbóreas. Verificou-se que a menor densidade de U. decumbens e de I. grandifolia afetou de negativamente, o crescimento das mudas das espécies nativas. No geral, observou-se diminuição do conteúdo de macro e micronutrientes nas folhas das mudas das quatro espécies arbóreas, principalmente na densidade de oito plantas daninhas/vaso. Os resultados obtidos podem embasar práticas experimentais sobre o controle químico em conjunto com métodos alternativos no controle de I. grandifolia e U. decumbens em áreas de restauração ecológica.Palavras-chave: competição, manejo, floresta estacional semidecidual, restauração.

Additive design: the concept and data analysis

“…Britton & Rose , Ceiba speciosa (A.St.‐Hil.) Ravenna, and Luehea divaricata Mart] (Monquero et al ., ). It becomes difficult to evaluate and compare weed competitiveness when different equations with non‐related parameters are used.…”

INFLUENCE OF Urochloa brizantha ON THE GROWTH AND NUTRITIONAL ABSORPTION OF TREE SPECIES

“…grandis in competition with U. brizantha, from 22 plants m -2 (COLMANETTI et al, 2019) and Pinus elliottii with U. plantaginea and U. humidicola (PEREIRA et al, 2016). In studies with native tree species, Monquero et al (2015) evaluated the effect of increased densities of U. decumbens on the growth of Senegalia polyphylla, Enterolobium contortisiliquum, Ceiba speciosa and Luehea divaricata and found that the presence of the competing species negatively affected the growth of these tree species even at the lowest density of two plants per pot. Santos et al (2019b) observed that the coexistence with U. brizantha negatively affected the growth of Schinus terenbtifolius.…”

Light intensity and sowing depth on the emergence and development of weeds

“…Weeds are one of the ecological factors that most affect the agricultural economy permanently because their presence in cultivated areas causes losses to crops and their control entails expenses that increase production costs (Monquero et al, 2015;Marchi et al, 2019). One of the highest limitations for implementing a weed management program is the lack of knowledge on the biology and ecology of the main species (Ramesh et al, 2017).…”

“…In general, seed germination is regulated by the interaction between environmental conditions and the state of physiological aptitude, and each species of plant requires a set of environmental resources necessary for the germination of its seeds, such as water, light, and temperature availability and sowing depth (Zuffo et al, 2014). Thus, knowledge of the emergence capacity of seedlings from seeds located at different soil depths can assist in the weed management through the adoption of methods that reduce or prevent their occurrence (Monquero et al, 2015;Montanha et al, 2018;Marques et al, 2019). An example is the mechanical control using equipment for soil preparation capable of providing seed incorporation at depths unfavorable to that ideal for seedling emergence (Maciel, 2014).…”