Urban vegetation phenology is essential for understanding climate change impacts on urban ecosystems, offering insights into ecological and health implications. Although previous studies have explored the response patterns of vegetation phenology along the urban-rural gradient, quantitative analysis considering the neighborhood and scale effects is still insufficient. In this study, we comprehensively assessed the responses of the start of season (SOS) on urban-rural gradients depicted by both impervious surface percentage (ISP) and its kernel density values (ISPKD) at different spatial scales in 32 large cities in the north temperate zone. Our results revealed that the ISPKD can moderately amplify the sensitivity of spring phenology responses to urban intensity compared to the direct ISP indicator, with a mean difference of 0.02 days per ISP or ISPKD unit increase among cities with a significant linear response. These changes are associated with the magnified urban-rural phenological difference when characterizing the urban-rural gradient using ISPKD compared to ISP, with an increased average urban-rural difference of 1.37 days across all study cities. Observations at coarser spatial resolutions made the overall advancing trends of spring phenology on the urban-rural gradient more pronounced. Specifically, the average trends across all study cities showing significant response trends across all spatial resolutions shifted from −0.07 days/% at 250 m resolution to −0.11 days/% at 2 km. In addition, coarser resolutions of 500 m, 1 km, and 2 km amplified the average urban-rural phenological differences by 0.69 days, 0.68 days, and 1.37 days, respectively, compared to 250 m. These findings provide quantitative evidence for understanding the impact of urban intensity on spring phenology, deserving attention when drawing conclusions from vegetation phenology products at different resolutions.

中文翻译：

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尺度效应对量化春季植被物候对城市强度响应的影响


城市植被物候学对于了解气候变化对城市生态系统的影响至关重要，有助于深入了解生态和健康影响。尽管前人的研究已经探索了植被物候沿城乡梯度的响应模式，但考虑邻域效应和尺度效应的定量分析仍然不够。本研究综合评估了北温带 32 个大城市在不同空间尺度上不透水表面百分比 （ISP） 及其核密度值 （ISPKD） 所描述的季节开始 （SOS） 对城乡梯度的响应。我们的结果表明，与直接 ISP 指标相比，ISPKD 可以适度放大春季物候响应对城市强度的敏感性，在具有显著线性响应的城市之间，每 ISP 或 ISPKD 单位增加的平均差异为 0.02 天。与 ISP 相比，使用 ISPKD 表征城乡梯度时，这些变化与放大的城乡物候差异有关，所有研究城市的平均城乡差异增加了 1.37 天。在较粗糙的空间分辨率下进行的观测使春季物候在城乡梯度上的总体推进趋势更加明显。具体来说，所有研究城市的平均趋势在所有空间分辨率上显示出显著的响应趋势，从 250 m 分辨率的 -0.07 天/% 转变为 2 km 时的 -0.11 天/%。此外，与 250 m 相比，500 m、1 km 和 2 km 的粗分辨率分别将城乡平均物候差异放大了 0.69 d、0.68 d 和 1.37 d。 这些发现为理解城市强度对春季物候的影响提供了定量证据，在不同分辨率下从植被物候产品中得出结论时值得关注。