Data from: Effects of water level and grassland management on alpha and beta diversity of wet grassland birds in restored wetlands

1. Nearly 60% of European wetlands have been lost to drainage or to the cessation of grassland management. Large amounts of resources are put into wetland restoration with the aim to recover biodiversity. However, few studies have simultaneously evaluated effects of management, wetness and flooding dynamics on biodiversity of restored wetlands such as seasonally-flooded wet grasslands. 2. We inventoried bird communities over four years at 137 sites (each 3.1 ha) within five restored wet grassland areas in Sweden to investigate whether species richness, and occurrence of 12 common wet grassland species were related to: (i) local conditions such as management (grazing, mowing and unmanaged areas), basic wetness and spring flooding dynamics. Further, we investigated whether: (ii) the composition of the adjacent landscape (20 ha) related to local bird diversity and (iii) species turnover (i.e. beta diversity) differed between sites characterized by their basic wetness, degree of flooding and predominant management regime. 3. Local species richness was positively linked to degree of flooding, and basic wetness of grasslands but not to type of grassland management. Species richness tended also to be negatively linked to proportion of forest at the landscape scale. Although variable, the same results were also true concerning the probability of the occurrence of a single species at the local scale. 4. Species turnover between sites, and thus total species richness, was distinctly higher in: (i) grazed as compared to mowed grasslands except in dry non-flooded grasslands and (ii) flooded as compared to non-flooded sites. Similar patterns held for the subset of 12 red-listed species. We suggest that the high beta diversity in grazed and flooded grasslands is driven by the heterogeneous vegetation structure, resulting in good conditions for foraging and nesting for several wet grassland bird species. 5. Synthesis and applications. The selection of wetlands for conserving wet grassland birds should prioritize temporary flooded grasslands of moderate wetness, preferably far from forest edges. Restoration and management of wet grasslands should include water level management, removal of shrubs and trees, and low intensity grazing whereas mowing could be used in non-flooded grasslands of low basic wetness.1. 欧洲近60%的湿地（wetland）因排水或草地管理终止而丧失。当前已投入大量资源开展湿地修复工作，以期恢复生物多样性（biodiversity）。然而，鲜有研究同时评估管理措施、湿地湿度及淹水动态对季节性淹水湿草甸（seasonally-flooded wet grasslands）等修复后湿地的生物多样性的影响。 2. 本研究在瑞典5处修复湿草甸区域内的137个样地（每个样地面积3.1公顷）开展了为期4年的鸟类群落调查，旨在探究：(i) 物种丰富度（species richness）及12种常见湿草甸鸟类的出现概率是否与局部环境条件相关，包括管理措施（放牧、刈割及未管理区域）、本底湿度及春季淹水动态；(ii) 周边20公顷范围内的景观组成是否与当地鸟类多样性相关；(iii) 以本底湿度、淹水程度及主要管理模式为特征的样地之间，物种更替（即β多样性（beta diversity））是否存在差异。 3. 局部物种丰富度与淹水程度及草地本底湿度呈显著正相关，但与草地管理类型无关。物种丰富度还倾向于与景观尺度上的森林占比呈负相关。尽管存在一定变异性，单物种在局部样地的出现概率也呈现出一致的规律。 4. 样地间的物种更替（即β多样性（beta diversity）），进而总物种丰富度，在以下两种情况中显著更高：(i) 与刈割草甸相比，放牧草甸（干燥非淹水草甸除外）；(ii) 与非淹水样地相比，淹水样地。针对12种红色名录物种（red-listed species）的亚组也得到了一致的规律。我们认为，放牧且淹水的草甸中较高的β多样性由异质化植被结构驱动，这为多种湿草甸鸟类提供了良好的觅食与筑巢条件。 5. 综合与应用。为保护湿草甸鸟类而遴选湿地时，应优先选择湿度适中的暂时性淹水草甸，且最好远离林缘。湿草甸的修复与管理应包括水位调控、灌丛与乔木移除及低强度放牧；而对于本底湿度较低的非淹水草甸，则可采用刈割管理方式。