Aims

Belowground interactions are still poorly understood in mixed-species forests. We investigated the effects of soil fertility on belowground processes in mixed planted forests.

Methods

The dynamics and traits of Eucalyptus and Acacia mangium fine roots (diameter < 2 mm) in plantations with 50% of each species were studied in a randomized block design established in a nutrient depleted soil. Stands with NPK fertilization applied at planting (F+) were compared to unfertilized stands (F-).

Results

In the 0–15 cm soil layer, Eucalyptus root mass density (RMD) was higher than Acacia RMD by 50% in F+ and 10% in F-, considering both ages. At 34 months of age, Eucalyptus RMD was 94% higher near Acacia trees than near Eucalyptus trees in F-. In this layer, Eucalyptus specific root length (SRL) was 21% higher than Acacia SRL at 16 months of age and was 10% higher in F- than in F+ at 34 months of age. The cumulative Eucalyptus fine root length production between 16 and 34 months was 66% higher in F- than in F+ in the 0–1 m soil layer.

Conclusions

Fertilization increased the competition between species and led to a partial exclusion of Acacia fine roots from the nutrient-rich topsoil. Soil exploration by Eucalyptus roots in the vicinity of Acacia trees was higher in F- than in F+, which suggests that unfertilized trees benefited from facilitation through higher soil N availability and direct N transfer from Acacia trees.

中文翻译：

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营养供应调节地下物种间的相互作用：桉树和马占相思混交林中细根的动态和性状

目的

在混合物种森林中，地下相互作用仍然知之甚少。我们调查了土壤肥力对混合人工林地下过程的影响。

方法

以在营养贫瘠的土壤中建立的随机区组设计研究了桉树和马占相思细根（直径<2 mm）在每个物种有50％的人工林中的动态和性状。将种植时施用NPK施肥的林分（F +）与未施肥的林分（F-）进行比较。

结果

在两个年龄段，在0-15厘米的土壤层中，桉树的根质量密度（RMD）均比相思RMD高50％和F- 10％。在34个月大时，相思树附近的桉树RMD比F-中的桉树树高94％。在这一层中，桉树的比根长（SRL）在16个月大时比Acacia SRL高21％，F-比在34个月大时F +高10％。在0–1 m土层中，F-累积的桉树细根长累积产量在16-34个月内比F +高66％。

结论

施肥增加了物种之间的竞争，并导致了营养丰富的表土部分地排除了相思树的细根。相思树附近的桉树根对土壤的勘测在F-处高于F +，这表明未施肥的树得益于更高的土壤N利用率和从相思树中直接转移N的促进。