Intra-urban variations in land surface phenology in a semi-arid environment

• Published in: Environmental research letters 2025-01, Vol.20 (1), p.014036
• Main Authors: Crawford, Ben, Kelsey, Kathy, Ibsen, Peter, Rees, Amanda, Charobee, Amanda
• Format: Article
• Language: English
• Subjects: Air temperature; Arid environments; Arid zones; Cities; Climate change; Ecosystem management; Ecosystem services; Environmental conditions; Environmental control; Environmental impact; Extreme heat; Green infrastructure; Growing season; Heterogeneity; Irrigated lands; Land cover; Metropolitan areas; Neighborhoods; Phenology; Remote sensing; Semi arid areas; Semi arid environments; semi-arid; Semiarid environments; Semiarid lands; Senescence; Soil moisture; Soil temperature; Time measurement; urban; Vegetation; Vegetation index
• ISSN: 1748-9326; 1748-9326
• DOI: 10.1088/1748-9326/ad9759

Urban vegetation is growing in importance as cities use ‘green infrastructure’ to mitigate the impacts of climate change, reduce extreme heat, and improve human health and comfort. However, due to the heterogeneity of city landscapes, urban vegetation experiences a diverse range of environmental conditions, potentially leading to differences in growing season timing and length within cities. Here, we investigate physical drivers of urban land surface phenology and timing within a semi-arid city (Denver, CO, USA) using four years (2018-2021) of remotely sensed vegetation indices, modelled air temperature, and land cover datasets. Within the metropolitan region study area, satellite-based vegetation index measurements (NDVI) indicate growing season length is variable on sub-neighborhood spatial scales. This variability is largely due to differences in the timing of fall senescence, as opposed to early season growth. Areas with substantial fractions of irrigated land cover tend to remain greener longer, while unirrigated and cooler areas are correlated with an earlier end to the growing season (up to ~two months shorter). These findings complement those from non-arid cities where surface and air temperature are the dominant environmental control on phenological timing. Results here indicate the importance of soil moisture for phenology in semi-arid regions and suggest unique semi-arid urban growing season dynamics and temperature-vegetation feedbacks. These interactions have implications for water, heat, and vegetation management strategies to maximize ecosystem services in water-limited environments.