Martínez-De León Gerard, Dani Lauriane, Hayoz-Andrey Aline, Humann-Guilleminot Ségolène, Arlettaz Raphaël, Humbert Jean-Yves
Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012, Bern, Switzerland.
BMC Ecol Evol. 2022 Feb 15;22(1):19. doi: 10.1186/s12862-022-01972-4.
Species-rich semi-natural grasslands are impacted by the severe land-use changes that are affecting mountain regions, compromising their high biodiversity value. In particular, sprinkler irrigation and increased fertilisation stimulate vegetation growth, modifying and homogenising habitat conditions for ground-dwelling invertebrates. Among them, land snails have been largely understudied despite their commonness and vulnerability to small-scale habitat alteration. This study investigated the mid- and long-term responses of land snail communities to management intensification of montane and subalpine hay meadows. Mid-term effects were studied using a randomised block design experiment, mimicking an intensification gradient with different levels of irrigation and fertilisation applied during 5 years. Long-term effects were examined relying on an observational approach that consisted in comparing snail communities in meadows managed intensively for > 20 years with those from the 5-year experimental module.
We show that management intensification initially boosts snail densities, but erodes species richness by - 35% in intensively-managed meadows in the long term. Contrary to our expectations, drought-tolerant (xerophilous) snails benefitted from grassland intensification, whereas mesophilous species accounted for most species losses due to intensification in the long run, indicating that the latter may be especially sensitive to the hostile microclimate conditions abruptly prevailing in a meadow after mowing. Soil pH was also a principal determinant of land snail occurrence, with almost no specimen recorded in acidic meadows (pH < 5.5), while plant diversity favoured overall snail abundance.
Despite the fact that xerophilous snails appear tolerant to management intensification, we found that several drought-sensitive species are lost in the long term. We conclude that the preservation of species-rich land snail communities in mountain hay meadows requires the conservation and restoration of low-input grasslands on basic soils for preventing further species losses of gastropod fauna.
物种丰富的半自然草原受到影响山区的严重土地利用变化的冲击，其高生物多样性价值受到损害。特别是，喷灌和增加施肥刺激了植被生长，改变并使地面无脊椎动物的栖息地条件趋于同质化。其中，尽管陆地蜗牛很常见且易受小规模栖息地改变的影响，但在很大程度上仍未得到充分研究。本研究调查了陆地蜗牛群落对山地和亚高山干草草甸管理集约化的中长期响应。中期效应通过随机区组设计实验进行研究，该实验模拟了5年期间不同灌溉和施肥水平的集约化梯度。长期效应则通过一种观察方法进行检验，该方法包括将集约化管理超过20年的草甸中的蜗牛群落与5年实验模块中的蜗牛群落进行比较。
我们表明，管理集约化最初会提高蜗牛密度，但从长期来看，会使集约化管理草甸中的物种丰富度降低35%。与我们的预期相反，耐旱（喜旱）蜗牛受益于草地集约化，而中生动物种在长期内由于集约化导致的物种损失占大多数，这表明后者可能对割草后草甸中突然普遍存在的恶劣小气候条件特别敏感。土壤pH值也是陆地蜗牛出现的主要决定因素，在酸性草甸（pH < 5.5）中几乎没有记录到标本，而植物多样性有利于总体蜗牛丰度。
尽管喜旱蜗牛似乎能耐受管理集约化，但我们发现从长期来看，几种对干旱敏感的物种会消失。我们得出结论，要保护山地干草草甸中物种丰富的陆地蜗牛群落，需要在碱性土壤上保护和恢复低投入草地，以防止腹足动物区系的进一步物种损失。
