Aims

Root traits associated with resource foraging, including fine-root branching intensity, root hair, and mycorrhiza, may change in soils that vary in rock fragment content (RFC), while how these traits covary at the level of individual root branching order is largely unknown.

Methods

We subjected two xerophytic species, Artemisia vestita (subshrub) and Bauhinia brachycarpa (shrub), to increasing RFC gradients (0%, 25%, 50%, and 75%, v v^− 1) in an arid environment and measured fine-root traits related to resource foraging.

Results

Root hair density and mycorrhizal colonization of both species decreased with increasing root order, but increased in third- or fourth-order roots at high RFCs (50% or 75%) compared to low RFCs. The two species tend to produce more root hairs than mycorrhizas under the high RFCs. For both species, root hair density and mycorrhizal colonization intensity were negatively correlated with root length and root diameter across root order and RFCs. Rockiness reduced root branching intensity in both species comparing with rock-free soil. At the same level of RFC, A. vestita had thicker roots and lower branching intensity than B. brachycarpa and tended to produce more root hairs.

Conclusion

Our results suggest the high RFC soil conditions stimulated greater foraging functions in higher root orders. We found evidence for a greater investment in root hairs and mycorrhizal symbioses as opposed to building an extensive root system in rocky soils. The two species studied, A. vestita and B. brachycarpa, took different approaches to foraging in the rocky soil through distinctive trait syndromes of fine-root components.

中文翻译：

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土壤中的岩石碎片含量改变了旱生植物的根部觅食行为

目标

与资源觅食相关的根性状，包括细根分枝强度、根毛和菌根，可能会在岩石碎片含量 (RFC) 不同的土壤中发生变化，而这些性状如何在单个根分枝顺序水平上共同变化在很大程度上是未知的.

方法

我们在干旱环境中对两种旱生植物Artemisia vestita（亚灌木）和Bauhinia brachycarpa（灌木）进行增加 RFC 梯度（0%、25%、50% 和 75%，vv ^-1）并测量细根性状与资源觅食有关。

结果

两种物种的根毛密度和菌根定植随着根序的增加而降低，但与低 RFC 相比，高 RFC（50% 或 75%）的三阶或四阶根增加。在高 RFC 下，这两个物种往往比菌根产生更多的根毛。对于这两个物种，根毛密度和菌根定植强度与根顺序和 RFC 的根长度和根直径呈负相关。与无岩石土壤相比，岩石减少了两个物种的根分枝强度。在相同的RFC水平下，A. vestita比B. brachycarpa具有更粗的根和更低的分枝强度 并且倾向于产生更多的根毛。

结论

我们的结果表明，高 RFC 土壤条件刺激了更高根目中更大的觅食功能。我们发现了对根毛和菌根共生的更大投资的证据，而不是在岩石土壤中建立广泛的根系。研究的两个物种，A. vestita和B. brachycarpa，通过细根成分的独特性状综合征采取不同的方法在岩石土壤中觅食。