Background and aims

Biological soil crusts (BSCs) co-occur with vascular plants in many ecosystems. Nevertheless, little is known regarding the interaction among BSCs and vascular plants, and no standard methods exist aiming to evaluate BSC–plant interactions. While some reports emphasized the inhibition effect of BSCs on germination, others reported the opposite or did not find any differences between germination under crusted and non-crusted conditions. Contradictory findings were also reported regarding the BSC effects on vascular plants after germination, with some reports claiming that BSCs promote growth, while others claim the opposite.

Methods

By a seed addition experiment (using light and heavy seeds of three species belonging to the Fabaceae family) in an early-successional system in Germany, we tested in situ the emergence of seedlings under variable surface conditions (cyanobacterial crust, disturbed and removed crust), and quantified crust-plant interactions (survival, flowering) during and following seedling emergence.

Results

In comparison to an average of 8% of the light Lotus corniculatus and 20% of the light Ornithopus sativus that emerged through the cyanobacterial BSC, 76% of the heavy Glycine max emerged. Once emerged, the crust did not significantly affect the survival, growth, biomass, or flowering of G. max, whereas many of the seedlings from lightweight seeds dried up soon after emergence. The thickness of the cyanobacterial biocrust had no influence on Fabaceae emergence.

Conclusion

The cyanobacterial BSC acted as a filter that hindered the emergence of the lightweight seeds.

中文翻译：

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以蓝藻为主的生物土壤结皮对幼苗出苗和命运的影响：原位实验

 背景和目标

在许多生态系统中，生物土壤结皮（BSC）与维管植物同时存在。然而，关于 BSC 和维管植物之间的相互作用知之甚少，并且不存在旨在评估 BSC 与植物相互作用的标准方法。虽然一些报告强调了BSC对发芽的抑制作用，但其他报告则相反，或者没有发现结皮和非结皮条件下的发芽之间存在任何差异。关于BSC对发芽后维管植物的影响也有相互矛盾的研究结果，一些报告声称BSC促进生长，而另一些报告则相反。

 方法

通过德国早期演替系统中的种子添加实验（使用属于豆科家族的三种物种的轻质和重质种子），我们在不同的表面条件（蓝藻结皮、扰动和去除结皮）下原位测试了幼苗的出苗情况，并量化出苗期间和出苗后的外壳与植物的相互作用（存活、开花）。

 结果

与平均 8% 的轻百脉根和 20% 的轻鸟鸟通过蓝藻 BSC 出现相比，76% 的重大豆出现。一旦出苗，结皮不会显着影响G. max的存活、生长、生物量或开花，而许多轻质种子的幼苗在出苗后很快就干枯了。蓝藻生物结皮的厚度对豆科植物的出现没有影响。

 结论

蓝藻BSC充当过滤器，阻碍轻质种子的出现。