Aix Marseille Univ, Avignon Université, CNRS, IRD, IMBE Institut Méditerranéen de Biodiversité et d'Écologie marine et continentale, Marseille, France.
Société EcoStat, Baudinard-sur-Verdon, France.
Sci Total Environ. 2023 Jun 20;878:162948. doi: 10.1016/j.scitotenv.2023.162948. Epub 2023 Mar 21.
Seabird colonies have a strong influence on both the physical and chemical soil parameters and plant communities of the islands where they settle to nest. Scientists have studied the effects of the demographic explosion of seabird populations, but few have explored the long-term effects when the colonies were in decline. The aim of this study was to investigate diachronic changes over a 24 year period of soil parameters, floristic composition and plant functionnal types (Raunkiaer growth forms and Grime life strategies) up to the decrease of the number of nesting yellow-legged gulls (Larus michahellis Naumann, 1840) on Mediterranean islands. We used 78 permanent plots to survey the vegetation and the soil parameters on 9 islands and one mainland area within the Calanques National Park (south east of France), for three periods (i.e., 1997, 2008, 2021). Since 1997, the increase of nesting gulls has caused a nitrogen and pH increase and organic carbon and C/N ratio decrease, although the values were still higher than mainland plots without nesting gulls. This has led to changes in plant species composition e.g., higher values of N favouring the development of ruderal plant species, still present in high frequency in 2021. Furthermore, plant species highly tolerant to disturbances (i.e., R Grime strategy) in harsh environments were still favoured even after the decline of gull abundance. However, both the frequency of the chamaephytes and the vegetation cover has increased with the decline of gull colony. In 2021, measures of trace elements' concentrations and calculation of pollution load index (Cu, Pb and Zn) reveals relatively low multi-contamination levels on the mainland and the archipelagos. On naturally oligotrophic and semi-arid Mediterranean islands, gull colonies induce a persistent alteration in soil characteristics that still influences plant communities (composition and functional types), 11 years after the decline in bird abundance.
海鸟群落在其筑巢栖息的岛屿上对土壤物理和化学参数以及植物群落具有强大的影响。科学家们研究了海鸟种群数量爆炸的影响，但很少有研究探索当海鸟群减少时的长期影响。本研究的目的是调查在 24 年的时间内，土壤参数、植物群落组成和植物功能型（Raunkiaer 生长型和 Grime 生活策略）的历时变化，直到地中海岛屿上黄腿海鸥（Larus michahellis Naumann，1840）筑巢数量减少。我们使用 78 个永久样本来调查卡尔卡松国家公园（法国东南部）内的 9 个岛屿和一个大陆地区的植被和土壤参数，共分为三个时期（即 1997 年、2008 年和 2021 年）。自 1997 年以来，筑巢海鸥的增加导致了氮和 pH 值的增加以及有机碳和 C/N 比的减少，尽管这些值仍然高于没有筑巢海鸥的大陆样地。这导致了植物物种组成的变化，例如，较高的氮值有利于杂草植物物种的发育，这些物种在 2021 年仍然高频出现。此外，在海鸥数量减少后，仍然有利于在恶劣环境中高度耐受干扰的植物物种（即 R Grime 策略）的发展。然而，随着海鸥群的减少，草本植物的频率和植被覆盖都有所增加。2021 年，微量元素浓度的测量和污染负荷指数（Cu、Pb 和 Zn）的计算表明，在大陆和群岛上的多污染水平相对较低。在自然寡营养和半干旱的地中海岛屿上，海鸥群落在鸟类数量减少 11 年后，仍然持续改变土壤特性，这仍然影响着植物群落（组成和功能型）。
