Abstract

The objective of this study was to analyze the root distribution of grasses and shrubs, at different soil depths, in two ecological sites (ES): highland (forest) and lowland (grassland). The root density (RD) estimation was used as a proxy to test the two-layer hypothesis. Three trenches were dug in both ES and the number of roots m⁻² was registered at different depth classes. The roots were classified in categories: (a) life forms (LF), grasses and shrubs and (b) root size (diameter): fine (<0.1 cm), small (0.11–0.5 cm); medium (0.51–1.5 cm) and large (>1.51 cm). Soil bulk density (Bd) was assessed by gravimetric method and its relation with RD was determined by regression analysis. RD was analyzed by using ANOVA with the factors: ES, LF, depth and root size. There were no significant differences in RD between the ES but RD significantly decreased with depth in both ES. In the upper horizons of the forest, there was higher shrubs RD (764 roots m²) than grass RD (128 roots m²) (p < 0.0001). In grassland, grass RD was registered in all the depths. Mean fine root density was greater than the mean of other root size categories. The relationship between RD and Bd was negative and only significant in the forest (p = 0.009). The distribution of roots of both LF in the soil profile of both ES did not respond completely to the two-layer hypothesis since in upper horizons an overlap was observed.

摘要

本研究的目的是分析不同土壤深度的草和灌木在两个生态位点 (ES) 中的根分布：高地（森林）和低地（草地）。根密度（RD）估计被用作检验两层假设的代理。在 ES 和根数 m ^{-2中都挖了三个沟}在不同的深度等级注册。根分为几类：（a）生命形式（LF）、草和灌木；（b）根大小（直径）：细（<0.1 cm）、小（0.11-0.5 cm）；中号（0.51–1.5 厘米）和大号（>1.51 厘米）。土壤容重（Bd）通过重量法评估，其与RD的关系通过回归分析确定。RD 通过使用 ANOVA 与以下因素进行分析：ES、LF、深度和根大小。ES 之间的 RD 没有显着差异，但 RD 在两个 ES 中随深度显着降低。在森林的上层，灌木 RD (764 根 m ² ) 高于草 RD (128 根 m ² ) ( p < 0.0001)。在草原，草RD在所有深度都有记录。平均细根密度大于其他根大小类别的平均值。RD 和 Bd 之间的关系是负的，并且仅在森林中显着（p  = 0.009）。两种 ES 土壤剖面中两种 LF 根的分布对双层假设没有完全响应，因为在上层观察到重叠。