Laclau J P, Arnaud M, Bouillet J P, Ranger J
CIRAD-Forêt/UR2PI, Pointe-Noire, République du Congo.
Tree Physiol. 2001 Feb;21(2-3):129-36. doi: 10.1093/treephys/21.2-3.129.
Spatial statistical analyses were performed to describe root distribution and changes in soil strength in a mature clonal plantation of Eucalyptus spp. in the Congo. The objective was to analyze spatial variability in root distribution. Relationships between root distribution, soil strength and the water and nutrient uptake by the stand were also investigated. We studied three, 2.35-m-wide, vertical soil profiles perpendicular to the planting row and at various distances from a representative tree. The soil profiles were divided into 25-cm2 grid cells and the number of roots in each of three diameter classes counted in each grid cell. Two profiles were 2-m deep and the third profile was 5-m deep. There was both vertical and horizontal anisotropy in the distribution of fine roots in the three profiles, with root density decreasing sharply with depth and increasing with distance from the stump. Roots were present in areas with high soil strength values (> 6,000 kPa). There was a close relationship between soil water content and soil strength in this sandy soil. Soil strength increased during the dry season mainly because of water uptake by fine roots. There were large areas with low root density, even in the topsoil. Below a depth of 3 m, fine roots were spatially concentrated and most of the soil volume was not explored by roots. This suggests the presence of drainage channels, resulting from the severe hydrophobicity of the upper soil.
在刚果的一个成熟桉树无性系种植园中，进行了空间统计分析，以描述根系分布和土壤强度变化。目的是分析根系分布的空间变异性。还研究了根系分布、土壤强度与林分水分和养分吸收之间的关系。我们研究了三条垂直于种植行且距一棵代表性树木不同距离的、宽2.35米的垂直土壤剖面。土壤剖面被划分为25平方厘米的网格单元，并统计每个网格单元中三个直径类别的根系数量。两条剖面深2米，第三条剖面深5米。在这三条剖面中，细根分布存在垂直和水平各向异性，根密度随深度急剧下降，随距树桩距离增加而增加。根系存在于土壤强度值较高（>6000千帕）的区域。在这种沙质土壤中，土壤含水量与土壤强度之间存在密切关系。旱季土壤强度增加主要是由于细根吸收水分。即使在表土中，也有大面积根密度较低的区域。在3米深度以下，细根在空间上集中分布，大部分土壤体积未被根系探索。这表明由于上层土壤的严重疏水性，存在排水通道。
