Understanding belowground morphological mechanisms of trees and grasses is a complicated task but can help in the design and management of silvopastoral systems. In this study, we evaluated the effect of the harvest intervals (i.e. 30 and 50 days) of aboveground biomass on the fine root density and vertical distribution in two silvopastoral systems (SPS): one comprising Leucaena leucocephala (legume tree) and Cynodon plectostachyus (grass) and the other L. leucocephala and Panicum maximum. We used a completely randomized design with four repetitions. We sampled fine roots by using a metal cylinder (8 cm diameter and 50 cm length) 7 days after each harvest. We washed the samples with pressurized water to separate them from the soil. The roots were digitalized at a resolution of 600 dpi to determine the diameter and specific root length by using IJ Rhizo® software. Samples were subsequently dried to quantify fine root mass. We found that the greater percentages of fine roots were between 0.4 and 0.8 mm for the legume and between 0.2 and 0.4 mm for grasses. The fine root length and mass density of P. maximum was higher (P < 0.001) compared to C. plectostachyus in both harvest intervals. However, the fine root density of L. leucocephala did not vary between SPS (P > 0.05). The effect of harvest interval was significant only in some soil layers in both SPS (P > 0.05). Most of the pasture roots were found in the upper soil layer (0–20 cm), while L. leucocephala roots were present to deeper soil layers. We conclude that P. maximum has a greater rooting capacity and a more rapid recovery than C. plectostachyus, which has greater diameters and lower root density. However, L. leucocephala presented deeper and thicker fine roots in both SPS, which is a good indication of its belowground recovery capacity to aboveground disturbances.

中文翻译：

---

两种收获间隔下林牧系统中银合欢和禾本科植物的细根密度和垂直分布

了解树木和草的地下形态机制是一项复杂的任务，但有助于林牧系统的设计和管理。在这项研究中，我们评估了地上生物量的收获间隔（即 30 天和 50 天）对两种林牧系统 (SPS) 中细根密度和垂直分布的影响：一种包括银合欢（豆科植物树）和犬齿苋（草）和其他 L. leucocephala 和 Panicum 最大。我们使用了四次重复的完全随机设计。我们在每次收获后 7 天使用金属圆柱体（直径 8 厘米，长度 50 厘米）对细根进行采样。我们用加压水清洗样品以将它们与土壤分离。使用 IJ Rhizo® 软件以 600 dpi 的分辨率对根进行数字化以确定直径和特定根长。随后将样品干燥以量化细根质量。我们发现豆科植物的细根比例较大，介于 0.4 至 0.8 毫米之间，而草则介于 0.2 至 0.4 毫米之间。在两个收获间隔中，与 C. plectostachyus 相比，P. maximum 的细根长度和质量密度更高（P < 0.001）。然而，L. leucocephala 的细根密度在 SPS 之间没有变化（P > 0.05）。收获间隔的影响仅在两种 SPS 的某些土层中显着（P > 0.05）。大多数牧草根存在于上层土层（0-20 cm），而 L. leucocephala 根存在于更深的土层中。我们得出结论，P。maximum 比 C. plectostachyus 具有更大的生根能力和更快的恢复，后者具有更大的直径和更低的根密度。然而，L. leucocephala 在两种 SPS 中都呈现出更深更粗的细根，这很好地表明了其对地上干扰的地下恢复能力。