Spontaneous urban vegetation as an indicator of soil functionality and ecosystem services

Abstract

Questions: Our study focused on spontaneous vegetation in urban greenspaces in a Mediterranean city with the aim of relating plant community properties with ecological services along soil disturbance gradients. We asked which plant communities have the greatest plant biodiversity and soil carbon storage and the best-performing nutrient cycles and water regulation. Location: Madrid City (Central Spain).Methods: We studied four types of plant communities following soil disturbance gradients: vegetation on trampled soils, roadside vegetation, annual grasslands and perennial forbs. Regarding vegetation, we studied plant composition and productivity, plant diversity, plant growth forms and functional groups. Regarding soils, we determined soil organic carbon (TOC), available nutrients, the activity of seven enzymes relating to the main macronutrient cycles, and physical properties such as bulk density (BD) and soil water-holding capacity (WHC). We used one-way ANOVA to determine the influence of the plant community type on both soil and vegetation variables.Canonical correspondence analysis was performed to interpret the relationships between plant species assemblages with environmental gradients.Results: Perennial forbs showed greater biomass and developed on soils with the greatest TOC and available phosphorus. Annual grasslands displayed the highest plant diversity. Roadside vegetation developed on soils with higher phenoloxidase activity when compared to vegetation on trampled soils and annual grasslands. Vegetation on trampled soils developed on soils with lower WHC, lower beta-glucosidase, arylamidase and phosphatase activities and higher BD when compared to perennial forbs.Plant community distribution followed gradients most significantly associated with soil organic matter content, soil compaction and nutrient cycling performance. Conclusions:We conclude that plant communities are good indicators of ecosystem function and services which are unevenly distributed throughout urban habitats. The management in Mediterranean unmaintained urban greenspaces should be aimed at avoiding soil compaction to promote biodiversity, carbon storage and water regulation.

Contribution of ruderal herbaceous vegetation to supporting services in Mediterranean urban greenspaces

“…A decreasing species richness from annual grasslands to perennial herbs has previously been reported in Mediterranean cities (Filibeck et al 2016). Perennial herbs of Malva species have been associated with highly disturbed habitats (Dana et al 2002; Güler 2020), particularly with the high availability of soil nutrients and a rapid and high demand for nutrients (Molina et al 2023).…”

“…The high cover of nutrient-demanding species such as Malva spp. and Diplotaxis virgata in certain habitats (perennial herb communities, roadside communities) is related to the greater availability of certain macronutrients such as N and P in the soil in comparison to other ruderal habitats such as those dominated by Hordeum leporinum (Molina et al 2023;Molina et al 2024). These differences between ruderal habitats support the various phytosociological order units, namely Brometalia for ruderal vegetation on soils that are not excessively nitri ed, and Chenopodietalia muralis for ruderal nitri ed soils (Rivas-Martinez and Izco, 1977; Mucina et al 2016).…”

“…We therefore hypothesize that annual grasslands constitute a general herbaceous matrix in Mediterranean urban greenspaces, whereas perennial herb communities and roadside vegetation correspond to successional stages related to different soil disturbances. Since perennial grasslands showed a higher oristic dissimilarity with perennial herbs and roadside vegetation, which are most closely related to more disturbed soils (Molina et al 2023;Molina et al 2024), we also assume that perennial grasslands correspond to a successional stage towards a more established soil (Fig. 8).…”

“…Vegetation type in uences the relationship between plant biomass and plant diversity with soil nutrients (Fayiah et al 2019). Malva communities are constituted by an assemblage of dense tall herbs developed on soils with a large amount of organic matter and nutrient availability (Molina et al 2023, Molina et al 2024, which supports the positive correlation between soil nutrients and plant biomass, and the inverse relationships between species richness and productivity at higher production levels found by Vermeer and Berendse (1983). In contrast, the other perennial vegetation in the study, perennial grasslands, tended to have a lower biomass.…”

“…These greenspaces are established on wastelands, abandoned crop elds and land lls, where trees -often pine -and shrubs have been planted, and some areas are irrigated to maintain lawns. Nevertheless, the main vegetation matrix comprises spontaneous ruderal herbaceous plants, distributed in different habitats along gradients of soil disturbance (Molina et al 2023;Molina et al 2024). These non-irrigated green areas are subjected to annual mowing to prevent res, which tend to occur in the dry summer season.…”