Interferência de plantas daninhas em mudas de quatro espécies arbóreas neotropicais

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.

巴西东南部的季节性半落叶阔叶林（Seasonal semideciduous forests）曾遭受高强度生境片段化，杂草的侵扰可能会干扰恢复群落的动态。本研究旨在明确：杂草俯仰臂形草（Urochloa decumbens）与大叶牵牛花（Ipomoea grandifolia）达到何种特定密度时，会对4种新热带区树木幼苗的生长产生负面影响——这4个树种分别为豆科（Fabaceae）的多叶金合欢（Senegalia polyphylla）、弯荚合欢（Enterolobium contortisiliquum），以及锦葵科（Malvaceae）的美丽异木棉（Ceiba speciosa）与叉枝椴（Luehea divaricata）。本研究采用完全随机试验设计，在温室环境中开展，针对每个受试树种设置5个杂草密度处理（每盆对应不同的杂草株数），每个处理设置4次重复。待杂草开花后，测定各幼苗的株高、茎粗、地上部干生物量，以及叶片中大量元素与微量元素的含量占比。结果显示，当与俯仰臂形草或大叶牵牛花共存时，最低杂草密度（每盆2株）即可对树木幼苗的生长产生负面影响。整体而言，叶片中大量及微量元素的占比均出现显著下降，尤以每盆8株杂草的处理组最为明显。本研究结果可为恢复区域内这两种杂草的化学防治结合其他替代防控手段的试验实践提供参考依据。