Sudmeyer R A, Speijers J, Nicholas B D
Department of Agriculture WA, PMB 50, Esperance 6450, Australia.
Tree Physiol. 2004 Dec;24(12):1333-46. doi: 10.1093/treephys/24.12.1333.
We quantified the extent and distribution of roots of four commonly planted tree species (Eucalyptus globulus Labill., Pinus radiata D. Don, P. pinaster Aiton and E. kochii Maiden & Blakely subsp. plenissima C.A. Gardner) in agricultural land adjacent to tree lines, and examined the effect of soil type and root pruning on root morphology. Root distribution in soil adjacent to tree lines was mapped by a trench profile method at 13 sites on the south coast of Western Australia. Soil samples were collected to determine water content and fertility. The lateral extent of tree roots ranged from 10 m for E. kochii to 44 m for P. pinaster. This equated to between 1.5 and 2.5 times tree height (H) for E. globulus and Pinus spp. to 4H for E. kochii. Root density declined logarithmically with distance from the trees and was greatest for P. pinaster and least for E. globulus (P < 0.001). The rate of decrease in root density with distance from the trees was greatest for the Pinus spp. and least for E. kochii (P < 0.05). Root density was generally greatest in the top 0.5 m of the soil profile and decreased with increasing depth. This decrease was relatively gradual in the deep sands, but abrupt in clay subsoil. Root dry mass in the sandy top soil beyond 0.5H ranged between 1.0 and 55.5 Mg km(treeline) (-1) for 6-year-old E. kochii and 50-year-old P. pinaster, respectively. Soil water content generally increased with distance from the trees (P < 0.001). There was no evidence of reduced soil fertility in the top 1.4 m of the soil profile adjacent to the trees. Two to four years after trees had been root pruned, both the lateral extent and vertical distribution of roots were similar for pruned and unpruned trees. The density of roots < 2 mm in diameter was greater for root-pruned trees than for unpruned trees (P < 0.05). We conclude that the study species can compete with agricultural crops based on the lateral extent of their roots and the occurrence of greatest root density within 0.5 m of the soil surface.
我们对四种常见造林树种（蓝桉、辐射松、海岸松和全缘桉）在林带附近农田中的根系范围和分布进行了量化，并研究了土壤类型和根系修剪对根系形态的影响。通过沟渠剖面法在西澳大利亚州南海岸的13个地点绘制了林带附近土壤中的根系分布图。采集土壤样本以测定含水量和肥力。树种根系的横向范围从全缘桉的10米到海岸松的44米不等。这相当于蓝桉和松属树种树高（H）的1.5至2.5倍，而全缘桉则为4H。根系密度随着与树木距离的增加呈对数下降，海岸松的根系密度最大，蓝桉的最小（P < 0.001）。松属树种根系密度随与树木距离增加的下降速率最大，全缘桉最小（P < 0.05）。根系密度通常在土壤剖面的顶部0.5米处最大，并随深度增加而降低。在深厚砂土中这种降低相对平缓，但在粘土层中则很突然。对于6年生的全缘桉和50年生的海岸松，在超出0.5H的砂质表土中，根系干质量分别在1.0至55.5 Mg km（林缘）（-1）之间。土壤含水量通常随着与树木距离的增加而增加（P < 0.001）。没有证据表明林带附近土壤剖面顶部1.4米内的土壤肥力下降。在对树木进行根系修剪两到四年后，修剪和未修剪树木的根系横向范围和垂直分布相似。直径小于2毫米的根系密度，修剪过的树木比未修剪的树木更大（P < 0.05）。我们得出结论，基于这些研究树种根系的横向范围以及土壤表层0.5米内根系密度最大的情况，它们能够与农作物竞争。
