Abstract
Urban gardens are vital green spaces, providing food for residents and space for engaged citizenry and community development. In California, climate change conditions (heat and drought) are becoming more extreme, threatening the resilience of urban gardens. Water use restrictions limit the timing and amount of water that gardeners can access, exacerbating these climate challenges for urban food production. Together with volunteer gardeners, we examined how ambient temperature, water use, vegetation, ground cover, and soil management affect rates of soil moisture gain and loss in urban gardens for a six-week period in the summer of 2017, during the hottest part of the growing season. We found that plot-level management of soils is essential for creating urban garden plots that maintain stable levels of water within garden soils. Although plots with better soil quality (i.e. water holding capacity) experienced slower rates of soil moisture gain after a watering event, they also experienced slower rates of soil moisture loss after the event, leading to soils with more stable, less fluctuating moisture profiles over time. This may benefit gardeners because under extreme climates (such as heat and drought) and water use restrictions, maintaining more stable soils for their plants means that the soils will retain water over a longer period after each watering event. Overall, such results highlight that better soil management that improves soil quality measures such as water holding capacity are potential solutions for maintaining soil moisture and reducing water use under changing climate conditions.
Highlights
Urban gardens are important sites of food production in cities, providing essential nutrients for food insecure communities and culturally appropriate foods where the traditional fruits and vegetables are unavailable in retail stores[1,2]
Urban gardens are usually irrigated by public water systems that are dependent on the water availability of the catchment
Soil moisture loss rates were calculated based on the 24 hours after the maximum soil moisture was achieved; some gardeners watered more periodically, and in these cases the soils continued to lose soil moisture until more water was input into the plot
Summary
Urban gardens are important sites of food production in cities, providing essential nutrients for food insecure communities and culturally appropriate foods where the traditional fruits and vegetables are unavailable in retail stores[1,2]. Urban heat islands can further exacerbate the effects of warming climate conditions[19] Due to this climate cycle and the lack of water storage during one of California’s worst droughts from 2012–201420, water use reductions were mandated in California and are expected to become more extreme in the upcoming decades with increased forecasted fire and drought events[21]. This has led to stricter local regulations of water supply that affect water availability for urban community gardens, with garden managers restricting water use amount and timing (for example, the San Jose Community Garden Program[22]). A soil moisture deficit is not uncommon during seasonal droughts in California[20], particular management decisions may affect the amount of water moisture that can be held in the system (Fig. 1 – a description of water balance factors provided in italicized font)
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