Soil pH and phosphorus drive species composition and richness in semi-natural heathlands and grasslands unaffected by twentieth-century agricultural intensification

Background: Increased soil phosphorus (P) caused by agricultural intensification has been associated with decreased plant species richness (SR) in central Europe. How plant communities and soil P gradients are related in unimproved open habitats remains unclear. Aims: The aim of this article was to characterise the relationship between soil chemical parameters and plant species composition and richness in unimproved open habitats. Methods: The influence of soil chemical parameters (pH, P, K, Mg) on species composition was assessed, using data from 40 heathland and 54 grassland plots, by non-metric multidimensional scaling and permutational multivariate analysis of variance. The relationship between soil chemical parameters and SR was tested by linear mixed effects models. Results: A direct relationship between heathland community composition and pH was observed, explaining 10% of variation in species composition, while P, Mg and pH together explained 17% of variation in grassland composition. In heathlands, SR increased with increasing pH, whereas in grasslands, SR decreased with increasing soil P. Conclusions: Soil chemical parameters were substantially related to plant community composition and richness. In an area spared from a century of agricultural intensification, reduced pH appeared to constrain SR in heathlands, while even slight P increases (−1) depressed plant SR in semi-natural grasslands.

研究背景：农业集约化引发的土壤磷（P）含量升高，已被证实与中欧地区植物物种丰富度（Species Richness, SR）下降存在关联。但未改良开放生境中，植物群落与土壤磷梯度之间的关联机制仍不明确。
研究目的：本文旨在阐明未受改良的开放生境中，土壤化学参数与植物物种组成、物种丰富度之间的关联关系。
研究方法：本研究采集了40个石楠灌丛样地与54个草原样地的调查数据，采用非度量多维标度分析（non-metric multidimensional scaling）与置换多元方差分析（permutational multivariate analysis of variance），评估了土壤化学参数（pH、磷（P）、钾（K）、镁（Mg））对植物物种组成的影响；同时通过线性混合效应模型（linear mixed effects models），检验了土壤化学参数与物种丰富度之间的关联。
研究结果：石楠灌丛群落组成与pH值存在直接关联，该关联可解释物种组成变异的10%；而磷（P）、镁（Mg）与pH值三者共同解释了草原群落组成变异的17%。在石楠灌丛中，物种丰富度随pH值升高而增加；而在草原样地中，物种丰富度则随土壤磷含量升高而下降。
研究结论：土壤化学参数与植物群落组成及物种丰富度存在显著关联。在百年未受农业集约化干扰的区域中，pH值降低会限制石楠灌丛的物种丰富度；而在半自然草原中，即使是小幅的磷（P）含量升高（−1）也会抑制植物物种丰富度。