Aims

Common Juniper (Juniper communis) populations in western Europe are rapidly declining due to a lack of regeneration, which has been linked to nitrogen (N) deposition. However, the mechanisms by which N deposition affects juniper are not clear. Nitrogen deposition can lead to N eutrophication and soil acidification, which cause nutrient leaching and metal mobilisation with potential negative impacts on juniper regeneration. We investigated associations among soil element concentration (soil [E]), needle element concentration (needle [E]) and plant performance in terms of height growth and viable seed production.

Methods

We sampled adult females and juveniles across 6 natural heathland areas in the Netherlands and Belgium, and applied linear mixed models for eleven elements to test associations among plant performance, soil [E], and needle [E].

Results

Soil [E] was reflected in needle [E], which subsequently was associated with juniper growth. However, direct associations between soil [E] and growth were absent. Seed viability was positively associated with soil Mg concentration, marginally with Ca and needle Ca and K concentrations, and negatively with soil NO₃ and needle N, S and Zn concentrations. Generally seed viability, needle Ca and K concentrations were low. Soil Al/P ratio was a better predictor for needle P than soil P concentration indicating that Al inhibits P uptake.

Conclusion

We conclude that 1) N eutrophication reduces seed viability, but increases growth, 2) nutrient leaching reduces nutrient uptake, seed viability and subsequently growth, and 3) Al mobilisation reduces P uptake and indirectly growth. N deposition amplifies these mechanisms and therefore inhibits regeneration and survival of juniper populations in western Europe.

中文翻译：

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氮沉降如何阻碍荒地中常见的杜松再生

 目标

由于缺乏再生，西欧的普通杜松（Juniper commis）数量正在迅速减少，这与氮（N）沉积有关。然而，氮沉降影响杜松的机制尚不清楚。氮沉降会导致氮富营养化和土壤酸化，从而导致养分淋溶和金属动员，对杜松再生产生潜在的负面影响。我们研究了土壤元素浓度（土壤[E]）、针元素浓度（针[E]）和植物在高度生长和可行种子产量方面的表现之间的关联。

 方法

我们对荷兰和比利时 6 个自然石南地区的成年雌性和幼体进行了采样，并应用 11 种元素的线性混合模型来测试植物性能、土壤 [E] 和针叶 [E] 之间的关联。

 结果

土壤 [E] 反映在针叶 [E] 中，随后与杜松生长相关。然而，土壤[E]和生长之间不存在直接关联。种子活力与土壤 Mg 浓度呈正相关，与 Ca 和针叶 Ca 和 K 浓度呈边际相关，与土壤 NO ₃和针叶 N、S 和 Zn 浓度呈负相关。一般来说，种子活力、针叶钙和钾浓度较低。土壤铝/磷比比土壤磷浓度更能预测针叶磷，表明铝抑制磷的吸收。

 结论

我们得出的结论是：1) 氮富营养化降低了种子活力，但增加了生长，2) 养分淋滤降低了养分吸收、种子活力和随后的生长，3) 铝动员降低了磷吸收和间接生长。氮沉积放大了这些机制，因此抑制了西欧杜松种群的再生和生存。