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. 尽管城市生态系统面临高强度干扰与生境改造，但其仍承载着相当丰富的生物多样性。然而，维持现有生物多样性水平的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发挥的核心研究目标。
2. 本研究旨在探究城市植物群落的多样性与组成如何受时空异质性土地利用遗留效应的影响。我们在美国马里兰州巴尔的摩市的一个城市街区中，选取了一批自建筑拆除以来时长覆盖3至22年的空置地块，构建了演替年代序列样地。于2012年与2013年夏季开展草本植物物种多度调查，调查点位覆盖每个空置地块中曾为建筑基底（building footprint）的区域，以及曾为后院或菜园的遗留花园（remnant garden）区域。
3. 研究发现，不同土地利用历史的空置地块区域间，植物群落组成呈现出显著分化格局：具体表现为建筑基底区域内植物群落的生物媒介种子传播策略功能组成发生显著变化，且随时间推移，植物群落的种子质量与终端速度功能性状值均有所提升。此外，同一空置地块不同区域的植物群落，其传播策略的功能差异随时间推移逐渐增大。与之相反，本研究的所有分类多样性测度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性土地利用遗留效应共同作用，塑造了城市植物群落的组成结构。尽管此前有研究提出，城市环境中强烈改变的局域生境条件与外来物种的竞争会抑制本土植物多样性，但本研究发现，种子传播是调控城市植物群落组装格局的更关键驱动因子。因此，聚焦生境连通性、并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群落成功建立的有效手段。2017年5月8日