Data from: Lake and catchment-scale determinants of aquatic vegetation across almost 1000 lakes and the contrasts between lake types

Aim: The factors controlling macrophyte (aquatic plant) composition are complex, recent research showing that the well-studied filtering effects of lake environmental factors are constrained by hydrological and landscape factors. We investigated the factors determining macrophyte composition in lakes over water body and catchment- scales and the transferability of this pattern across lake types. Location: Almost 1000 lakes distributed across Britain. Taxon: Lake macrophytes. Methods: Lakes were partitioned into five types based on subdivision of alkalinity and elevation gradients. Data from botanical surveys were used to compare spatial turnover and nestedness components of beta diversity between lake types. The relative importance of lake environment (based on local physicochemical data), hydrology (e.g. lake and stream density), landscape (e.g. fragmentation indices, land cover) and spatial autocorrelation in explaining macrophyte composition were derived from variance partitioning. Results: Species composition showed strong spatial structuring, suggestive of overland dispersal, enhanced by spatially-correlated abiotic factors such as alkalinity and elevation. Catchment-scale factors (e.g. land use, connectivity) promoted the establishment of different communities (more or less diverse, or differing in composition) but were of secondary importance. Turnover in composition between upland lakes was lower than in other lake types, reflecting a more specialist flora and increased potential for propagule exchange due to spatial aggregation and hydrological connectivity. Main conclusions: Vegetation composition in lakes is more spatially-structured than previously appreciated, consistent with the importance of dispersal limitation, but this does not apply evenly to all lakes, being most acute in lowland high alkalinity lakes. Thus, spatially-structured abiotic factors, such as alkalinity, influence macrophyte composition most (suggestive of niche filtering) in those lakes where human impacts tend to be greatest, although nestedness was also lowest there. By contrast, hydrological connectivity has a proportionally stronger structuring role in upland lakes.

研究目的：调控大型水生植物（macrophyte）群落组成的因素复杂多样，已有研究表明，被广泛探讨的湖泊环境因子过滤效应会受到水文与景观因子的约束。本研究旨在探究水体与集水区尺度下，决定湖泊大型水生植物群落组成的影响因子，以及该分布格局在不同湖泊类型间的可推广性。
研究区域：分布于英国全境的近1000个湖泊。
研究类群：湖泊大型水生植物。
研究方法：本研究依据碱度（alkalinity）与海拔梯度的细分标准，将湖泊划分为5种类型。采用植物学调查数据，对比不同湖泊类型间β多样性（beta diversity）的空间周转（spatial turnover）与嵌套性（nestedness）组分。通过方差分区（variance partitioning）分析，量化湖泊环境（基于局地理化数据）、水文要素（如湖泊与溪流密度）、景观要素（如破碎化指数、土地覆盖类型）以及空间自相关（spatial autocorrelation）在解释大型水生植物群落组成中的相对重要性。
研究结果：物种组成呈现显著的空间结构特征，暗示存在陆地扩散过程，而碱度与海拔等空间相关的非生物因子进一步强化了该结构。集水区尺度的因子（如土地利用、水体连通性）会促进不同群落（多样性水平或组成存在差异的群落）的建立，但此类因子的重要性相对次要。高地湖泊间的群落组成周转速率低于其他湖泊类型，这反映出高地湖泊拥有更为特化的植物区系，且由于空间聚集与水文连通性提升了繁殖体（propagule）交换的潜力。
主要结论：湖泊水生植物群落的空间结构比以往认知更为显著，这与扩散限制的重要性相符，但该规律并非均匀适用于所有湖泊，在低地高碱度湖泊中这一特征最为突出。因此，在人类活动影响通常最为强烈的湖泊中，诸如碱度这类具有空间结构的非生物因子对大型水生植物群落组成的影响最为显著（该结果符合生态位过滤（niche filtering）的理论预期），尽管此类湖泊的嵌套性水平也最低。与之相反，水文连通性在高地湖泊中发挥的群落结构调控作用相对更强。