How Cool Are Allotment Gardens? A Case Study Of Nocturnal Air Temperature Differences In Berlin, Germany

Urban green infrastructures have been extensively studied for their ability to mitigate the urban heat island (UHI) effect. However, allotment gardens (AGs)-a prominent type of urban green infrastructure within many European cities-have not yet been comprehensively investigated concerning their microclimates. In this study, nocturnal air temperatures (T-N) in 13 AG complexes (AGCs) were measured during the summer of 2018 in Berlin, Germany. These were compared to measurements in densely built-up urban areas (URB), two large inner-city parks and rural areas (RUR). On average, the assessed AGCs were 2.7 K cooler at night than URB. Most of the investigated AGCs (11/13) displayed a larger mean TN difference to URB ((Delta T-N AGC) over bar) than the examined urban parks. RUR showed the largest differences to URB ((Delta T-N RUR) over bar ), indicating a UHI effect. Furthermore, the influence of land surface characteristics of the AGCs on (Delta T-N AGC) over bar was analyzed. (Delta T-N AGC) over bar decreased significantly as the floor space index around AGCs increased. The analysis of the shape complexity also produced a significant positive correlation with (Delta T-N AGC) over bar . In contrast, size and distance to the city center of an AGC decreased significantly with increasing (Delta T-N AGC) over bar . This study provides first insights into the microclimate of AGs and influencing variables concerning T-N.