Data from: Calcicolous plants colonize limed mires after long-distance dispersal

Aim Dispersal range is a key factor for understanding species’ persistence in dynamic landscapes. However, dispersal, especially over long distances, is inherently difficult to study. Making use of a unique system of anthropogenically disturbed, geographically isolated mires, we assessed dispersal ranges for a group of plants restricted to wet calcareous conditions via empirical studies of colonization patterns. We hypothesized that more species would have colonized the less isolated mires and that colonization frequencies would be related to traits influencing propagule pressure. Location Sweden Taxon Calcicolous vascular plants and bryophytes Methods The study system consisted of 52 acidic mires that had acquired a high pH through active liming by the Swedish government during the past two decades. These conditions killed off mat-forming Sphagnum spp. mosses, rendering the mires open to colonization by other species. In each mire, we recorded the presence of rich fen plant species typically only found in high pH wet soils throughout the country. We used citizen science-collected records of occurrences of obligate rich fen species surrounding each mire to examine the likely dispersal distances that were involved in creating the colonization patterns. Results A lower proportion of vascular plants than bryophytes from their respective species pools colonized the limed mires (27% vs 67%, p=0.001). The number of colonized rich fen species per site was 0–6 for vascular plants and 10–31 for bryophytes and was positively related to potential diaspore sources >20 km from the mires (p=0.026 and p=0.012, respectively). The proportion of colonized mires was positively related to the species’ regional frequency, but not with their diaspores’ terminal velocity. Main conclusions Many bryophyte species can effectively disperse over long distances (tens of kilometres) and variation among species in total diaspore production seems to be an important regulator of colonization across landscapes, for both vascular plants and bryophytes, in communities that are open to colonization.

研究目的：扩散范围是理解物种在动态景观中存续的关键因子。然而，扩散过程，尤其是长距离扩散，本质上难以开展研究。本研究依托一套独特的人为干扰、地理隔离的泥炭沼泽系统，通过对定居格局的实证研究，评估了一类局限于湿润钙质生境的植物类群的扩散范围。
研究区域：瑞典
研究类群：钙质维管植物（calcicolous vascular plants）与苔藓植物（bryophytes）
研究方法：本研究的实验系统包含52个酸性泥炭沼泽，在过去二十年中，瑞典政府通过主动施石灰使其pH值升高。该处理杀灭了形成垫状群落的泥炭藓属（Sphagnum spp.）苔藓，使沼泽得以被其他物种定居。在每个沼泽中，我们记录了仅在瑞典境内高pH湿润土壤中出现的富钙沼泽植物物种的存在情况。我们利用公民科学（citizen science）收集的各沼泽周边专性富钙沼泽物种的分布记录，探究了塑造该定居格局的潜在扩散距离。
研究结果：相较于苔藓植物，来自各自区域物种库的维管植物在施石灰沼泽中的定居比例更低（27% vs 67%，p=0.001）。每个样点的定居富钙沼泽物种数量：维管植物为0~6种，苔藓植物为10~31种，且该数量与距离沼泽>20km处的潜在繁殖体（diaspore）源呈正相关（分别为p=0.026和p=0.012）。定居沼泽的物种比例与物种的区域发生频率呈正相关，但与繁殖体的终端速度（terminal velocity）无显著关联。
主要结论：许多苔藓植物能够有效实现长距离（数十公里）扩散；对于开放定居的群落而言，物种间总繁殖体产量的差异似乎是调控维管植物与苔藓植物跨景观定居过程的重要因子。