Urban landscapes are the most rapidly expanding biome on Earth (Laurance and Engert, 2022), harboring diverse urban green spaces (UGS), including urban forests, residential gardens, lawns, and meadows. Collectively, UGS supply multiple benefits (“ecosystem services”) to humans and the environment (Aronson et al., 2017; Paudel and States, 2023). Specifically, UGS provide habitats for plants and animals; reduce flooding, urban heat island effects, and pollution; store carbon; offset greenhouse gas emissions; and offer social, aesthetic, and human health benefits (Swanwick et al., 2003; Pataki et al., 2011; World Health Organization (WHO), 2016). Among the range of green spaces, lawns are ubiquitous and the most dominant features across urban landscapes in the urbanized world. Ongoing urbanization that will bring around 68% of the global population to cities by 2050 (UN DESA, 2018) drives fragmentation, habitat loss, and further spread of grassy lawns across residential and commercial areas. Despite some positive ecosystem benefits, such as soil organic matter accumulation, carbon capture, aesthetics, and recreation, increased lawn areas can have detrimental ecological and environmental effects (Paudel and States, 2023).
Lawns are dominated by one or a few grass species, often monoculture, planted intentionally for aesthetics and recreation purposes. Lawns increase economic burdens from management, such as inputs (e.g., nutrients, herbicides, and insecticides), gasoline use, and labor, ecological costs from biodiversity loss (Faeth et al., 2011), and environmental concerns from excessive use of chemicals, irrigation, and greenhouse gas emissions (Townsend-Small and Czimczik, 2010, van Delden et al., 2016). Lawns also alter ecosystem processes by changing soil structure, pH, nutrient cycling, and microbial communities, including mutualistic arbuscular mycorrhizal (AM) fungi (Schmidt et al., 2017; Nugent and Allison, 2022). Soils under continuously mowed lawns are compacted with high bulk density (Edmondson et al., 2011). These physical changes in urban soils reduce water, gases, and nutrients flow in the soil matrix (Gregory et al., 2006), leading to poor water infiltration and drainage. In addition, compacted soils reduce air and water movement, inhibit plant growth (Gregory et al., 2006; Tessler et al., 2023) and destabilize microbial networks (Hernandez et al., 2021), which affect denitrification and greenhouse gas emissions (Hartmann et al., 2014; Longepierre et al., 2021). Intensive inputs, such as fertilizers and pesticides, further contaminate urban soils and increase nonpoint source pollution, affecting downstream water systems from the local to continental scale.
A nature-based approach to the conservation and management of UGS can mitigate multifaceted negative consequences associated with urbanization and lawn management. One such strategy is to create biodiverse natural or semi-natural green spaces such as perennial native meadows (hereafter, meadows) in tropical to temperate climates or xeric meadows in more arid and semi-arid climates (Paudel and States, 2023). Indeed, managing urban green spaces as meadows has become increasingly popular in recent years (Southern et al., 2017; Paudel and States, 2023) due to their smaller size, ease of management, minimal maintenance (Smetana and Crittenden, 2014), enhanced aesthetic beauty (Lindemann-Matthies and Brieger, 2016), increased plant diversity (Chollet et al., 2018), and pollinator-friendly environment (Hoyle et al., 2017; Griffiths-Lee et al., 2022). Norton et al. (2019) reported increased plant and invertebrate abundance and richness in meadows compared to regularly mown traditional lawns in Southern England. Kawahara et al. (2021) recently suggested that converting urban lawns into diverse natural habitats, such as meadows, is one of the most important actions that can be taken to save the global decline of pollinators. Some studies also suggest that meadows can improve soil health by stabilizing and improving soil aggregate (Pohl et al., 2009) and supporting soil microbial diversity (e.g., AM fungi) (Baruh et al., 2020; Tessler et al., 2023). Baruh et al. (2020) suggest that replanting native vegetation can restore fungal microbiomes in urban green spaces. Tessler et al. (2023) in New York, USA, found higher levels of soil microbial diversity in meadows compared to lawns. Besides these few one-time studies, there are no comprehensive multi-year comparisons between traditional lawns and meadows of nutrients, trace metal elements, and microbial functional groups in urban soils. Investigating the influence of lawns and meadows on urban biodiversity and soil health can help decision-makers and urban planners develop urban green space management plans to enhance soil health, biodiversity, and socioecological services.
In this study, using multi-year systematic sampling, we compared plant species diversity and soil, chemical and biological characteristics in meadows and lawns. Specifically, we examined whether urban meadows (i) can positively contribute to plant alpha diversity and (ii) increase soil health by (a) improving soil nutrients and microbial functional group abundance and (b) reducing trace metal elements in the soil. We hypothesized that compared to lawns, meadows would have higher plant alpha diversity and microbial abundance. We also hypothesized that increased plant diversity in meadows would improve soil nutrients, lower trace metal elements, and enhance microbial abundance. Research efforts like this are crucial for the sustainable management of UGS and the design of future landscapes that align with the United Nations sustainable development goal of “Sustainable Cities and Communities” for rapidly urbanizing cities worldwide.