Abstract

Aims

The effects of biocrusts on vascular plants are rarely evaluated in coastal saline lands. Our aim was to examine whether and how a mosaic of biocrusts affect seed germination of two typical herbaceous plants in a coastal saline land of the Yellow River Delta, to enhance our understanding by which substrate heterogeneity influences plant community dynamics.

Methods

We conducted growth chamber experiments to investigate the effects of biocrusts and uncrusted soil from bare patch-, Phragmites australis-, Suaeda glauca- and Tamarix chinensis-dominated habitats on seed germination percentage and mean germination time of two herbaceous plants: the perennial P. australis and the annual S. glauca. We also explored the mechanisms underlying the effects of substrate on seed germination.

Important Findings

Compared with uncrusted soil, biocrusts increased water content, nutrient accumulation and concentration of most salt ions, but they reduced soil pH value. Biocrusts with mosses directly decreased soil pH value and concentration of Mg²⁺, resulting in an indirect increase in seed germination percentage of S. glaucas. The low soil pH value also resulted in an indirect decrease in seed germination speed of P. australis in their own habitats. Bare patch directly increased accumulation of Cl⁻, resulting in an indirect decrease in seed germination speed of P. australis. These results suggest that biocrusts with mosses in P. australis habitats offer a window of opportunity for germination of S. glaucas. Biocrusts combined with habitat type have the potential to influence plant community structure through an effect on seed germination and establishment.

中文翻译：

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黄河三角洲沿海盐碱地镶嵌生物土壤结皮对维管束植物建立的影响

摘要

目的

在沿海盐碱地地区，很少评估生物结皮对维管束植物的影响。我们的目的是检查生物结壳的镶嵌是否以及如何影响黄河三角洲沿海盐碱地的两种典型草本植物的种子发芽，从而增进我们对底物异质性影响植物群落动态的理解。

方法

我们进行生长室实验，调查从裸patch-，biocrusts和uncrusted土壤的影响芦苇- ，碱蓬-和柽柳chinensis-对种子发芽率和两个草本植物的平均发芽时间决定的栖息地：常年芦苇和一年生的S. glauca。我们还探索了底物对种子发芽的潜在作用机理。

重要发现

与未覆盖的土壤相比，生物结壳增加了水分含量，养分积累和大多数盐离子的浓度，但降低了土壤的pH值。带有苔藓的生物结皮直接降低了土壤的pH值和Mg ^2+的浓度，从而间接增加了欧洲蓝点菜种子的发芽率。低的土壤pH值还间接导致了其自身栖息地中澳大利亚野菜的种子萌发速度的降低。裸补丁直接增加的Cl积累^- ，导致种子萌发速度的间接降低芦苇。这些结果表明，澳大利亚青枯菌中的生硬生物与苔藓栖息地为青冈种子的萌发提供了机会。生物结皮与栖息地类型相结合，有可能通过影响种子发芽和定殖而影响植物群落结构。