In urban areas, anthropogenic drivers of ecosystem structure and function are thought to predominate over larger‐scale biophysical drivers. Residential yards are influenced by individual homeowner preferences and actions, and these factors are hypothesized to converge yard structure across broad scales. We examined soil total C and total δ¹³C, organic C and organic δ¹³C, total N, and δ¹⁵N in residential yards and corresponding reference ecosystems in six cities across the United States that span major climates and ecological biomes (Baltimore, Maryland; Boston, Massachusetts; Los Angeles, California; Miami, Florida; Minneapolis‐St. Paul, Minnesota; and Phoenix, Arizona). Across the cities, we found soil C and N concentrations and soil δ¹⁵N were less variable in residential yards compared to reference sites supporting the hypothesis that soil C, N, and δ¹⁵N converge across these cities. Increases in organic soil C, soil N, and soil δ¹⁵N across urban, suburban, and rural residential yards in several cities supported the hypothesis that soils responded similarly to altered resource inputs across cities, contributing to convergence of soil C and N in yards compared to natural systems. Soil C and N dynamics in residential yards showed evidence of increasing C and N inputs to urban soils or dampened decomposition rates over time that are influenced by climate and/or housing age across the cities. In the warmest cities (Los Angeles, Miami, Phoenix), greater organic soil C and higher soil δ¹³C in yards compared to reference sites reflected the greater proportion of C₄ plants in these yards. In the two warm arid cities (Los Angeles, Phoenix), total soil δ¹³C increased and organic soil δ¹³C decreased with increasing home age indicating greater inorganic C in the yards around newer homes. In general, soil organic C and δ¹³C, soil N, and soil δ¹⁵N increased with increasing home age suggesting increased soil C and N cycling rates and associated ¹²C and ¹⁴N losses over time control yard soil C and N dynamics. This study provides evidence that conversion of native reference ecosystems to residential areas results in convergence of soil C and N at a continental scale. The mechanisms underlying these effects are complex and vary spatially and temporally.

中文翻译：

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城市土壤碳和氮在全球范围内汇聚

在城市地区，生态系统结构和功能的人为驱动因素被认为比大规模生物物理驱动因素更为重要。住宅院子受个体房主的偏好和行为的影响，并且假设这些因素可以在广泛范围内融合院子结构。我们研究了土壤总C和总δ ¹³ C，有机碳和有机δ ¹³ C，全N和δ ¹⁵ N的住宅码和相应的美国各地的跨越大的气候和生态生物群落六个城市参考的生态系统（巴尔的摩，马里兰州；马萨诸塞州波士顿；加利福尼亚州洛杉矶；佛罗里达州迈阿密；明尼苏达州明尼阿波利斯-圣保罗；亚利桑那州凤凰城。在整个城市中，我们发现土壤碳，氮含量及土壤δ ¹⁵N进行比较，以支持这一假设参考点在住宅码不太变量，土壤C，N，和δ ¹⁵ ñ收敛在这些城市。在有机土壤C，土壤中氮和土壤增加δ ¹⁵ ñ跨城市，郊区和农村住宅码在几个城市支持了土壤的反应相似跨城市改变了资源的投入，在码促进土壤C，N的收敛假说与自然系统相比。居民区土壤碳氮的动态变化表明，随着时间的流逝，城市土壤中碳和氮的输入增加或分解速率受制于城市间气候和/或居住年龄的影响。在最温暖的城市（洛杉矶，迈阿密，凤凰城），更大的有机土壤碳和较高的土壤δ ¹³与参考点相比，院子中的C反映出这些院子中C ₄植物的比例更高。在两场热身干旱城市（洛杉矶，凤凰城），总土壤δ ¹³ ℃升高和有机土壤δ ¹³ C ^，随着年龄的家庭表示在码左右较新的家庭更大的无机碳减少。一般情况下，土壤有机碳和δ ¹³ C，土壤N，和土壤δ ¹⁵ N含量上升随着年龄家表明增加土壤C和N循环速率和相关联的¹² C和¹⁴随着时间的流逝，N的损失控制了院子土壤的C和N动力学。这项研究提供的证据表明，将原始参考生态系统转换为居住区会导致整个大陆的土壤碳和氮趋同。这些影响的潜在机制是复杂的，并且会在空间和时间上发生变化。