Data from: Land use history and seed dispersal drive divergent plant community assembly patterns in urban vacant lots

1. Despite high levels of disturbance and habitat modification, urban ecosystems still host substantial levels of biodiversity. The processes that maintain existing levels of diversity, however, remain understudied. Identifying the links between urban ecological processes and patterns has, therefore, become a fundamental research goal to support urban biodiversity and ecosystem functioning. 2. We conducted a study to determine how the diversity and composition of urban plant communities is affected by spatially and temporally variable land use legacies. We constructed a chronosequence of vacant lot properties covering a range of 3-22 years since demolition, in an urban neighborhood in Baltimore, Maryland (USA). Surveys of herbaceous plant species abundance were conducted during the summers of 2012 and 2013 in sections of each vacant lot where the building previously stood (the ‘building footprint’) and sections of the lot that was previously a backyard or garden (the ‘remnant garden’). 3. We found divergent patterns in plant community composition between areas of vacant lots with varying land use histories. This includes significant shifts in the functional composition of biotically-vectored seed dispersal strategies, as well as an increase in seed mass and terminal velocity trait values of plant communities in building footprints over time. Additionally, we found that communities in different sections of the same vacant lot tended to become more functionally dissimilar in dispersal strategies over time. In contrast, we found no significant changes in taxonomic diversity over time for any of our measures. 4. Policy implications: Our study suggests that regional-scale patterns of seed dispersal interact with heterogeneous land use legacies to structure urban plant communities. Although it has been suggested that highly altered local environmental conditions and competition from introduced species limit native plant diversity in urban environments, we find dispersal to be a more significant driver of urban plant community assembly patterns. Implementing management strategies that focus on habitat connectivity and augmenting species pools via seeding may present an effective strategy for promoting more successful establishment of diverse flora in urban environments.08-May-2017

1. 尽管受到高强度干扰与生境改造，城市生态系统仍维系着可观的生物多样性水平。然而，维持当前多样性水平的相关生态过程仍未得到充分研究。因此，明确城市生态过程与格局之间的关联，已成为支撑城市生物多样性保护与生态系统功能运行的核心研究目标。2. 本研究旨在探究空间与时间维度上异质的土地利用遗留效应如何影响城市植物群落的多样性与组成。我们在美国马里兰州巴尔的摩市的一处城市街区中，构建了拆除后时长覆盖3至22年的空置地块时间序列样地（chronosequence）。于2012年与2013年夏季开展草本植物物种多度调查，调查区域涵盖每个空置地块中原有建筑所在的建筑基底（building footprint）区段，以及原属后院或花园的遗留花园（remnant garden）区段。3. 研究发现，不同土地利用历史的空置地块区域间，植物群落组成呈现分化格局。具体表现为：建筑基底区段的植物群落中，生物媒介传播种子（biotically-vectored seed dispersal）策略的功能组成随时间发生显著变化，同时种子质量与终端速度等功能性状值亦呈上升趋势。此外，同一空置地块不同区段的植物群落，其传播策略的功能差异随时间逐渐增大。与之形成对比的是，本研究采用的所有分类多样性指标均未随时间出现显著变化。4. 政策启示：本研究表明，区域尺度的种子传播格局与异质的土地利用遗留效应共同塑造了城市植物群落结构。尽管此前有研究提出，城市环境中剧烈改变的局域生境条件与外来引入物种的竞争会抑制本土植物多样性，但本研究发现，种子传播是驱动城市植物群落组装格局的更关键因素。实施以生境连通性为核心、通过播种扩充物种库的管理策略，或可成为促进城市环境中多样植物区系成功定植的有效途径。2017年5月8日