Data from: Biodiverse cities: the nursery industry, homeowners, and neighborhood differences drive urban tree composition

In arid and semi-arid regions, where few if any trees are native, city trees are largely human-planted. Societal factors such as resident preferences for tree traits, nursery offerings, and neighborhood characteristics are potentially key drivers of urban tree community composition and diversity, however they remain critically understudied. We investigated patterns of urban tree structure in residential neighborhoods of the Salt Lake Valley, Utah, combining biological variables, such as neighborhood and plant nursery tree species and trait composition, and sociological data comprised of resident surveys and U.S. Census data. We sampled nine neighborhoods that varied in household income and age of homes. We found more tree species were offered in locally-owned nurseries compared with mass merchandiser stores and yard trees at private residences were more diverse than public street trees in the same neighborhoods. There were significant differences among neighborhoods in street and yard tree composition. Newer neighborhoods differed from older neighborhoods in street tree species composition and trait diversity, while neighborhoods varying in affluence differed in yard tree composition. Species richness of yard trees was positively correlated with neighborhood household income, while species richness of street trees was negatively correlated with home age of neighborhood residences. Tree traits differed across neighborhoods of varying ages, suggesting different tree availability and preferences over time. Lastly, there was a positive correlation between resident preferences for tree attributes and the number of trees that had those attributes both in residential yards and in nursery offerings. Strong relationships between social variables and urban tree composition provides evidence that resident preferences and nursery offerings affect patterns of biodiversity in cities across Salt Lake Valley. These findings can be applied toward efforts to increase taxonomic and functional diversity of city trees in semi-arid regions in ways that will also provide ecosystem services of most interest to residents.

在干旱与半干旱区域中，本土原生树木本就极为稀少，城市树木几乎均为人工栽植。居民对树木性状的偏好、苗圃供应的苗木种类以及社区特征等社会因素，可能是影响城市树木群落组成与多样性的关键驱动因子，但目前相关研究仍严重不足。本研究针对美国犹他州盐湖谷的住宅社区，探究其城市树木结构特征，整合了两类数据：一是生物变量，涵盖社区与苗圃的树木物种及性状组成；二是社会经济数据，包括居民调查问卷数据与美国人口普查数据。我们选取了9个家庭收入与住宅房龄存在差异的社区作为研究样本。研究发现，与大型量贩式商超相比，本地苗圃供应的树木物种更为丰富；且同一社区内，私人住宅庭院的树木多样性显著高于公共行道树。不同社区的行道树与庭院树木组成均存在显著差异。房龄较新的社区，其行道树物种组成与性状多样性均与老旧社区存在显著差异；而贫富水平不同的社区，其庭院树木组成也存在差异。庭院树木的物种丰富度与社区家庭收入呈正相关，而行道树的物种丰富度则与社区住宅的平均房龄呈负相关。不同房龄的社区，其树木性状存在差异，这表明随着时间推移，可供选择的树木种类与居民的偏好均发生了变化。最后，居民对树木属性的偏好，与住宅庭院及苗圃供应中具备该属性的树木数量均呈正相关关系。社会变量与城市树木组成之间存在显著关联，这证明居民偏好与苗圃供应确实会影响盐湖谷各城市区域的生物多样性格局。本研究结果可用于指导半干旱区域城市树木的分类与功能多样性提升工作，同时还能为居民提供他们最为关注的生态系统服务功能。