Differences in soil chemical properties with distance to roads and age of development in urban areas

The main objective of this study was to characterize variation in soil chemical properties with length of urbanization period and distance to roads. Urban boundaries from 1920’s (old), 1960’s (middle) and 2000’s (new) were identified for three cities in northeast Ohio: Massillon, Wooster and Canton. Within each identified historic boundary, soil samples were collected from two road-side and two interior lawns in one public school site in each city. Thus, there were three urban age and two distance-to-roads classes. Soil particle composition and basic chemical properties including pH, available phosphorus (P), exchangeable potassium (K), calcium (Ca), magnesium (Mg), cation exchange capacity (CEC), nitrate, total carbon (C), total nitrogen (N), and soil organic matter (SOM) were measured. Two notable spatio-temporal patterns appeared repeatedly in the data set. First, total C, total N and SOM were higher in the soils of old (>50 years) urban sites than of newly developed sites. Similar, but not always significant, trends in soil pH, and exchangeable Ca were also observed. Second, road-side soils had higher pH, Ca, total C and N than interior sites regardless of urban age. These data indicate that key soil chemical properties can vary in predictable ways with urban age and distance-to-roads classes. Such variations in key soil chemical properties may influence or reflect soil biota and biogeochemical processes in urban soils.     

URban Biotopes of Aotearoa New Zealand (URBANZ) (I): composition and diversity of temperate urban lawns in Christchurch

Christchurch urban lawns are dominated by non-native grasses and forbs. However, we document considerable plant diversity; the total number of species encountered in our 327 sampled lawns was 127, although 80 species occurred in <2% of lawns. Seven distinct lawn communities were identified by Two-Way INdicator SPecies ANalysis using occurrence of 47 species that occurred in > 2% of lawns. Our ability to explain variation in species composition was surprisingly good and indicates intensity of lawn maintenance such as frequency of mowing, irrigation, fertiliser, and herbicide use and whether clippings are removed or not plays the major role. Species richness significantly declines with an increase in total area of contiguous lawn, leaf litter cover, the presence of grass clippings, and on loamy soil. Hence, park lawns with coarser management had lower species richness than residential lawns. Native species were more prevalent in well tended residential lawns, where more frequent mowing and removal of clippings or litter build-up diminishes shoot competition or shading. There is tremendous potential for more native species in New Zealand lawns which would contribute substantially to the conservation of endangered lowland herbaceous flora.     

Contrasting soil nitrogen dynamics across a montane meadow and urban lawn in a semi-arid watershed

Urbanization substantially increases nitrogen (N) inputs and hydrologic losses relative to wildland ecosystems, although the fate of N additions to lawns and remnant grasslands remains contested. In montane semi-arid ecosystems, N cycling is often closely coupled to snowmelt (the dominant period of infiltration) and snow cover, which impact soil temperature and moisture. Here, we compared soil N dynamics between a fertilized and irrigated urban lawn and nearby riparian meadow in Salt Lake City, Utah during a snow manipulation experiment. Snow removal increased freeze/thaw events but did not affect N pools, microbial biomass, denitrification potential, or soil oxygen (O₂). Mineral N was similar between sites despite lawn fertilization, but dissolved organic N (DON) was four-fold greater (2.1 ± 0.1 mg N l^?1) in lawn soil water. Infiltration was lower in the lawn subsoil, and leaching losses (modeled with Hydrus) were small at both sites (< 2 kg N ha^?1 y^?1) despite substantial lawn fertilization. Lawn soil O₂ fluctuated between 20.9 and 1.6 % following snowmelt and irrigation, but remained near 20 % in the meadow; the lawn had more reducing microsites as indicated by iron speciation. Post-snowmelt potential denitrification was six-fold greater in the lawn than the meadow. Lawns can potentially provide hotspots of denitrification in a semi-arid landscape that exceed some natural riparian ecosystems, whereas DON may represent an increasingly important form of N loss from lawns.     

Ecology of urban lawns under three common management programs

Turfgrass lawns are a central part of urban and suburban landscapes throughout North America and are often managed using repeated applications of chemical fertilizers and pesticides. These inputs are expensive and may negatively affect ecological processes in lawns. Therefore, we evaluated the influence of three most common lawn care programs on ecological characteristics of turfgrass lawns. Twenty-eight home lawns, separated into 3 groups based on the lawn care program (professional, do-it-yourself [DIY], and no-input), were studied. Data on lawn quality, weed and insect infestation, disease incidence, soil nematode community, soil nitrogen pools, microbial biomass (MBN), and soil organic matter (SOM) were collected. Results indicated that professional lawn care resulted in the highest aesthetic lawn quality mainly due to better weed control, compared to DIY and no-input programs. However, professional and DIY programs negatively affected MBN and SOM pools and enhanced disease (rust) severity. No significant differences in soil nematode population and nematode community indices across the three programs were found, indicating no differences in net ecosystem productivity among the three programs. Overall, soil nematode food web in turfgrass lawns represented a disturbed food web compared to natural grasslands and forest ecosystems, irrespective of the lawn care program used.     

Drivers of soil carbon in residential ‘pure lawns’ in Auburn,Alabama

Urban land area is expanding worldwide and may contribute to long-term carbon (C) storage; however, little is known about potential drivers of soil C in urban areas. Residential areas are one of the largest urban land use zones and lawns can provide stable chronosequences for studying soil C dynamics. In residential lawns containing no trees (n?=?23), the relationships between soil C and four potential drivers [home age (1–51 years), yard maintenance practices (fertilization, irrigation, and bagging or mulching lawn clippings), soil nitrogen (N) and soil texture] were investigated. Soil C increased with home age at 0–15 cm depth by 0.026 kg C m^?2?yr^?1, declined by ?0.011 kg C m^?2?yr^?1 at 15–30 cm depth, and was stable at 30–50 cm depth. Soil C had a positive relationship with soil N (R ²?=?0.55) at the 0–15 cm depth. Soil C and N were not related to yard maintenance practices or soil texture. The low soil C sequestration rate and limited relationships between soil C and home age, yard maintenance, soil N and soil texture may have resulted from the positive influence of Auburn’s humid, subtropical climate on residue decomposition.     

Changes through time in soil Collembola communities exposed to urbanization

The study aimed to assess if long-term exposure to urbanization changes the structure and composition of soil collembolan communities in urban green components (street lawns and park lawns) and in all urban green. Species diversity metrics, rarefaction, species richness estimators (Chao 1 and ACE) and multivariate analysis were used for the comparison of changes in community structure and diversity pattern over ca 30 years’ time span. Our results clearly demonstrate a shift, through time, in Collembola community composition and structure in an urban ecosystem and confirm that there is a linkage between long-term exposure to urbanization and changes in collembolan communities. Long-term urbanization led to erosion in species diversity and the formation of species-poor communities, species replacement, loss of specialized forms and promoted the invasion of exotic species. However, we show that the time span considered produced significant differences in diversity attribute values for the collembolan communities from street lawns and insignificant differences in park lawns, also we noted lack of significant differences in collembolan abundance across the two urban green components. The observed temporal changes in collembolan communities indicate that their response to disturbances in urban settings and selecting species is shaped by multiple processes. We conclude that more resistant collembolan communities were found over time in less stressed urban greening components such as park lawn soils compared to street lawn soils.     

Estimating urban lawn cover in space and time: Case studies in three Swedish cities

Lawns are considered monocultures and lesser contributors to sustainability than diverse nature but are still a dominating green area feature and an important cultural phenomenon in cities. Lawns have esthetical values, provide playground, are potential habitat for species, contribute to carbon sequestration and water infiltration, but also increase pesticides, fertilization, are monocultures and costly to manage at the same time. To evaluate the potential impact of lawns, whether positive or negative, it is of interest to estimate the total lawn cover in cities and its change over time. This is not a straightforward process, e.g., because many lawns are small and covered by trees. In this study we review the existing literature of lawn cover in cities and the different methodologies used for cover estimation. We found both pros and cons with NDVI and LiDAR data as well as manually interpreted aerial photos. The total cover of lawns in three case study cities was estimated to 22.5%. By extrapolating these percentages to all Swedish cities lawn cover was estimated to 2589 km² (0.6% of the terrestrial surface). The approximated total municipal management cost of lawns in all Swedish cities was 910,000,000 USD/ year. During 50 years lawn area almost doubled in relative cover and 56% of them were continuously managed. Since lawns constitute large parts of the urban greenery and are costly to manage it is highly relevant to consider their social, ecological and cultural value compared to alternatives, e.g., meadows with less intensive management.     

Potential nitrogen mineralization responses of urban and rural forest soils to elevated temperature in Louisville,KY

Soil nitrogen (N) mineralization is an important process determining terrestrial N availability, and evidence suggests elevated temperatures will enhance N mineralization rates. Along a 40 km urban-rural gradient of chestnut oak forest stands in Louisville, KY, we expected N mineralization rates would be higher in urban than in rural forests in part due to increased temperatures caused by the urban heat island. However, a 12-month field study along this Louisville gradient showed that annual N mineralization rates were lower in urban than in rural stands. Since variation in precipitation inputs and other factors across this land-use gradient may be influencing soil N mineralization rates, we conducted a three-month soil incubation experiment in the lab to determine the extent to which a + 2 °C temperature difference could affect soil N mineralization in urban and rural soils. Across the range of temperatures tested, rural soils mineralized N at twice the rate of urban soils under base (7.86 vs. 3.65 mg N kg^?1 AFDW soil d^?1) and elevated (9.08 vs. 4.76 mg N kg^?1 AFDW soil d^?1) temperatures (p < 0.01). A 2 °C temperature difference, did not significantly alter total inorganic N production in urban (p = 0.272) or rural soils (p = 0.293). The proportion of nitrate produced was lower in the urban (15.1 %) than in the rural soils (72.3 %; p < 0.01). These results suggest that differences in soil organic matter quality and potentially decomposer community composition are the primary explanatory factors for forests along this Louisville gradient.     

Baseline biodiversity surveys of the soil macrofauna of London’s green spaces

A serious barrier to our understanding of urban ecosystems is a lack of information on the ecology of soils organisms of green spaces within large cities. This study addresses this gap by providing baseline survey data on the biodiversity of soil macrofauna in urban parks and domestic gardens of London, UK. In April and June 2004, the soil macrofauna were handsorted from soil cores in eleven parks and gardens of various sizes in central London. Five taxa were identified to species (Lumbricidae, Isopoda, Diplopoda, Chilopoda and Formicidae). The biodiversity value of the two main habitats (horticultural borders and mown grass lawns) was assessed and the influence of a range of environmental factors on species density (number of species per unit area) examined. The species densities of the studied soil invertebrates in the urban gardens were comparable with those found in natural ecosystems, although plant borders contained significantly more species than lawns. Borders had higher levels of plant nutrients, higher floristic diversity and lower levels of micronutrients and heavy metals than lawns. Significant predictor variables of species densities in the plant borders were the percentage of leaf litter cover, sampling month and soil pH. Species densities in the lawns were significantly correlated with the distance of the samples from the edge of the lawn.     

A comparison of carbon and nitrogen stocks among land uses/covers in coastal Florida

Coastal areas are rapidly developing due to population growth and the appeal of coastlines. In order to gain insight into how land use/cover affects carbon (C) storage in a coastal context, we examined soil and vegetation C and soil nitrogen (N) across land uses near Apalachicola, FL. Forested wetlands had the greatest soil C and N storage, while natural pine forests and pine plantations had the least. In paired plots, urban lawns had significantly greater mineral soil N content compared to urban forest remnants. Total ecosystem C (soil + vegetation) was higher in forested wetlands than all other land uses/covers combined due to the high organic content of those wetland soils. Urban forest remnants and lawns had greater total ecosystem C than natural pine forests and pine plantations, which likely reflects the differential influence of prescribed fire and less frequent anthropogenic disturbances between the rural and urban areas, respectively. Projections of land use change in Franklin County, FL combined with these data suggest that increases in C storage are possible with continued urbanization along the Gulf Coast, if forest remnants are left and lawns are incorporated in built-up areas. However, this study does not account for C emissions during land conversion, or any emissions associated with maintaining urban built-up and residential areas. A better understanding of land use/cover influences on C pools has applications for planning and development, as well as ecological and environmental protection in the region.     

Water,sediment, and nutrient runoff from urban lawns established on disturbed subsoil or topsoil and managed with inorganic or organic fertilizers

Urban runoff has become an increasingly important environmental concern in recent years. With increasing urbanization, turfgrass area has substantially expanded in North America, and these lawns are often established on subsoil stripped of topsoil. In this study, 24 turfgrass-type tall fescue (Festuca arundinacea) plots were established on subsoil or topsoil, and managed with inorganic fertilizer (Scott’s Turf Builder®), organic fertilizer (Nature’s Touch® with enzymes), or no fertilizer (control). A one-hour simulated rainfall at 8.9 cm/hour was applied to the plots, and the time to runoff initiation and total runoff volume were measured. Runoff water samples were analyzed to quantify the amounts of sediment, N (NH₄-N), P, K, and S losses. The results indicated that runoff initiation time was almost half in subsoil lawns (12.5 min) than in topsoil lawns (23 min). The total runoff volume and sediment loss were significantly larger in subsoil lawns (11,900 ml and 3,700 mg, respectively) than in topsoil lawns (2,200 ml and 900 mg, respectively). Although the N, P, K, and S losses in runoff were low, they were significantly higher from the subsoil-based than topsoil-based lawns, and were higher from inorganic fertilizer treated lawns than those treated with organic fertilizer. These results highlight the significance of topsoil preservation in city planning and urban development with respect to urban run-off and water quality and show distinct benefits of organic lawn management practices over the conventional inorganic practices for maintaining urban water quality.     

Influence of aboveground tree biomass,home age,and yard maintenance on soil carbon levels in residential yards

With the rapid urbanization of natural lands, researchers have begun to examine the capacity of urban soils to store carbon (C), with recent attention to residential yards. We performed a case study to examine four potential influences on soil C levels in residential yards. In 67 yards containing trees, we examined the relationship of soil C (kg m^?2) to tree aboveground biomass, home age (3–87 years), yard maintenance (fertilization, irrigation, mulching or bagging lawn clippings), and soil texture (% clay, % sand, % silt), at three depths (0–15 cm, 15–30 cm, and 30–50 cm). Six tree aboveground biomass data sets were developed: 1) biomass, 2) biomass*(1/distance from tree), 3) biomass?≤?15 m from sample site, 4) biomass?≤?10 m, 5) biomass?≤?5 m, and 6) biomass?≤?4 m. Biomass?≤?5 m and biomass?≤?4 m had the greatest explanatory power for soil C at 30–50 cm depth (P?=?0.001, R²?=?0.28; P?=?0.05 R²?=?0.39, respectively). The relationship between soil C and home age was positive at 0–15 cm (P?=?0.0003, R²?=?0.19), but constant at the two lower depths. Yard maintenance had no significant influence on soil C levels across home age. At 0–15 cm, soil C increased with % silt (P?=?0.006, R²?=?0.12). Overall, trees in turfgrass yards may have a stabilizing effect on soil C levels below 15 cm but minimal influence above 15 cm.     

A comparison of soil organic carbon stocks between residential turf grass and native soil

A central principle in urban ecological theory implies that in urbanized landscapes anthropogenic drivers will dominate natural drivers in the control of soil organic carbon storage (SOC). To assess the effect of urban land-use change on the storage of SOC, we compared SOC stocks of turf grass and native cover types of two metropolitan areas (Baltimore, MD, and Denver, CO) representing climatologically distinct regions in the United States. We hypothesized that introducing turf grass and management will lead to higher SOC densities in the arid Denver area and lower densities in the mesic Baltimore area relative to native cover types. Moreover, differences between turf grass soils will be less than differences between the native soils of each metropolitan region. Within Baltimore, turf grass had almost a 2-fold higher SOC density at 0- to 1-m and 0- to 20-cm depths than in rural forest soils, whereas there were no differences with soils of urban forest remnants. Moreover, urban forest remnants had more than 70% higher SOC densities than rural forest soils. Within Denver, turf grass (>25 years of age) had more than 2-fold higher SOC densities than in shortgrass steppe soils, while having similar densities to Baltimore turf grass soils. By contrast, the native soils of Baltimore were almost 2-fold higher than the native steppe grass soils of Denver using SOC densities of remnant forests as representative of native soils in the Baltimore region. These results supported our hypothesis that turf grass systems will be similar in SOC densities across regional variations in climate, parent material, and topography. These similarities are apparently due to greater management efforts in the Denver region to offset the constraint of climate, i.e., anthropogenic factors (management supplements) overwhelmed native environmental factors that control SOC storage.     

Ecosystem services provided by urban spontaneous vegetation

Spontaneous vegetation colonizes large areas in and around cities. These unmanaged areas are considered to have low economic value or indicate dereliction, but recent research suggests that these can contribute valuable ecosystem services. This study evaluates indicators of ecosystem services in three habitats: urban spontaneous vegetation (USV), managed lawns, and semi-natural urban forest, in Halifax, Nova Scotia. USV had higher indicator values for habitat provisioning (plant species diversity, invertebrate abundance and taxonomic diversity) than the other habitats. Indicators of climatic regulatory services (albedo and leaf area index) in USV were similar to those in lawn habitats. Organic carbon content of the soils, an indicator of carbon storage, was lowest in USV but only marginally lower than in lawns. Standing biomass, an indicator of production services, was lowest in USV but lawn production may have been overestimated. While USV sites are usually transitory components of the urban landscape, they deserve further consideration due to their provision of ecosystem services, in some cases to a greater extent than conventionally valued urban habitats.     

Implementing integrated pest management in professional lawn care: a case study

Human choices regarding land cover management practices may influence ecosystem services provided by urban green spaces. We conducted a 2-year study to compare biological (weed, insect, and disease), aesthetic (lawn quality), and economic (lawn care program cost) attributes of an integrated pest management (IPM) program, in which pesticides are applied on the basis of treatment thresholds, with a standard program, in which pesticides are applied on a calendar basis without pest monitoring. Both programs were managed by a professional lawn care operator. Although weed incidence was low, the IPM program had significantly more lawns with weed presence than the standard program during 2005 and 2006. However, only 21% of the IPM lawns required herbicide applications in 2005, and none exceeded the treatment threshold (5% weed cover) in 2006 as compared to 100% of the standard program lawns being treated for weeds in both years. The IPM program also had significantly more lawns with insect damage than the standard program during June 2005 and August 2005, but not September 2005 and throughout 2006. Only 28% of the IPM lawns required insecticide applications in 2005 and none exceeded the threshold (5% insect damage) in 2006 whereas all of the lawns in the standard program received insecticide treatments in both years. Rhizoctonia blight was present on some of the lawns, but was not a common problem. Although lawn quality was high for both programs (>8, on a scale of 1–9), it was significantly higher for standard than for IPM program lawns during 2005, and June 2006 and September 2006, but not August 2006. The annual lawn management costs were lower for the IPM (281.50) than the standard program (281.50) than the standard program (458.06). Thirty one percent of the IPM program customers who continued with the study in 2006 did so because they were satisfied with the IPM program. Among those who did not continue with the program, 33% cited weed or insect problems, while 33% expected better results. The implications of these findings for implementation of IPM in professional lawn care are further discussed.     

Soil microbial community of urban green infrastructures in a polar city

Urban and technogenic landscapes in subarctic zones are not considered comfortable habitats for soil microbiota. However, green infrastructures in polar cities can provide a new niche for the development of a microbial soil community. Soil microbial biomass and the diversity of cultivable microfungi have been studied in relation to the chemical and morphological properties of urban soils in the polar city of Apatity. The quantitative indicators based on fluorescence microscopy and PCR real-time methods as well as the qualitative composition of the cultivable microfungal community were used to characterize the microbial community. Changes in the morphological and chemical composition of urban soils included a shift in pH and increased C and N content compared with forest soil. Studies have shown that the biomass of microfungi and actinomycetes in urban soils was lower than in forest soils and equals 0.12–0.19 mg/g and 0.06–0.44?×?10^?3 mg/g, respectively. Bacterial biomass, on the contrary, increased in urban soils up to 2.6?×?10^–3 – 5.6?×?10^–3 mg/g. The number of ITS gene copies of fungi in urban soils varied from 5.0?×?10⁹ to 1.45?×?10¹⁰ copies/g of soil, reaching the highest values in the courtyard. The number of rRNA gene copies of bacteria and archaea in urban soils increased compared with forest soil and amounted to 2.37?×?10¹⁰ – 9.99?×?10¹⁰ and 0.4?×?10¹⁰ – 0.8?×?10¹⁰ copies/g of soil, respectively. In urban soils, morphological changes in microfungi, including the predominance of small spores, were revealed in comparison with forest soils, where mycelium prevailed. An increase in the diversity of microfungi in urban soil and changes in the structure of their communities compared with forest soil was noted. Microfungi found in urban soils are not typical of the background soils of the region and would be expected in more southern conditions. Among them, opportunistic fungi species have been identified in humans, which increases the risk of diseases in residents of the northern region.

     

A comparison of soil carbon dynamics in residential yards with and without trees

Residential lawns provide chronosequences to examine influences of home age and aboveground tree biomass (ATB) on soil carbon (C) levels. Soil C dynamics were compared between 44 lawns with trees (LwT) and 23 without trees (PL). At the 0–15 cm depth, LwT had higher mean soil C than PL and an earlier rise in median soil C across home age. Nonparametric quantile regression also showed a steeper rise in the 5th, 50th, and 95th soil C quantiles for LwT. Fitted polynomial regression models indicated that home age and ATB together accounted for 40 % of the soil C variation at the 0–15 cm depth [C = 1.34 + 0.05(Age) + 0.0003(ATB)]. At the 15–30 cm depth, the interaction between home age and ATB explained 33 % of the soil C variation [C = 0.78 + 0.0003(Age*ATB)]; at 30–50 cm, ATB was responsible for 20 % [C = 0.56 + 0.0003(ATB)].     

Urbanisation factors impacting on ant (Hymenoptera: Formicidae) biodiversity in the Perth metropolitan area, Western Australia: Two case studies

Two synchronous projects undertaken in 2011 examined the likely impact of increasing urban densification on invertebrate populations within urban settlement in Perth, Western Australia. One project analysed the ant fauna found in 20 gardens and lawns in small to very small properties (these having a bungalow or duplex (semi-detached) as the main residential building, and a lawn or garden area of 43 m²–332 m²) east, south, north and west of the Central Business District (CBD). The other project examined the ant fauna at 14 sites, principally in native regrowth along the Kwinana Freeway, a major artery that runs north to south through Perth’s suburbs. The gardens and lawns produced a very depauperate fauna of 26 ant species, of which a maximum of 20 were native and at least six species were exotic. The ant fauna from regrowth adjacent to the Kwinana Freeway and at two additional sites (one a bush control) was more than twice as rich, the 56 species collected including only two exotics. In the garden project, ant richness, evenness and abundance were not significantly correlated with size of the garden area. The same applied even when the exotic Pheidole megacephala-dominated gardens were removed from the analysis. Ordination analysis combining the two sets of data revealed a distinct clustering of most of the regrowth sites, whereas the bush control stood alone and garden or lawn sites exhibited a much looser pattern of association. We suggest that increasing the density of Perth suburbs is resulting in drastic loss of native invertebrate fauna, of which ants are a useful bioindicator. However, native vegetation regrowth along major arterial roads could act as a reservoir for invertebrate species that might otherwise disappear entirely from the Perth metropolitan area.     

Does education influence wildlife friendly landscaping preferences?

In sprawling metropolitan areas, residential landscaping is a major concern with respect to biodiversity conservation, and it could play a critical role in conserving wildlife habitat. In the United States, residential landscaping typically consists of maintained lawns with specimen plantings of non-native trees and shrubs; such designs provide poor habitat for urban wildlife species. We conducted a case study of Raleigh, North Carolina residents to determine how providing information about the benefits of native plant landscaping to bird species influenced urban residents’ landscaping preferences. We used Wilcoxon Signed Rank tests to determine if respondent preferences for 0, 50, 75 and 100 % native plant landscaping coverages changed after residents were informed about the benefits that native plants provide for birds. Initially, the 50 % native landscaping coverage was most preferred by residents; however, preferences for all four native plant landscaping coverage designs were significantly different after the informational treatment. Neutrality changed to opposition for the 0 % native plant coverage, while opposition changed to support and neutrality for the 75 and 100 % native plant coverage designs, respectively. After the informational treatment, the 50 and 75 % native plant landscaping coverage had the highest mean preference levels, although the 100 % design was ranked first more than any other design. Our findings suggest that residential support for native plant landscaping is higher than is reflected by typical residential landscaping practices, and that dissemination of information regarding the benefits of native plant landscaping to birds could alter public preferences for native plant landscaping.     

Soil-atmosphere exchange of carbon dioxide,methane and nitrous oxide in urban garden systems: impact of irrigation,fertiliser and mulch

Urban green spaces provide important ecosystem services, such as amenity, biodiversity, productivity, climate amelioration, hydrological and biogeochemical cycling. Intensively managed urban gardens can sequester carbon through vegetation growth and soil C increase, but may experience nitrous oxide (N₂O) emissions and reduced soil methane (CH₄) uptake from irrigation and fertiliser use. Soil atmosphere exchange of N₂O, CH₄ and carbon dioxide (CO₂) was measured in lawn and wood chip mulched garden areas in Melbourne, Australia in winter, spring and summer under various water and fertiliser regimes. Gas exchange before and after lawn fertiliser application was measured continuously for three weeks using an automated chamber system. Applying fertiliser led to a peak N₂O emission of >60 μg N m⁻² h⁻¹, but overall only weekly irrigation (10 mm) significantly increased mean soil N₂O emissions above that in other treatments. Under mulch, mean soil N₂O emissions (14.0 μg N m⁻² h⁻¹) were significantly smaller than from irrigated lawn (27.9 μg N m⁻² h⁻¹), whereas mean soil CH₄ uptake under mulch (−30.7 μg C m⁻² h⁻¹) was significantly greater (p < 0.01) than in any lawn treatment. Lawns were either a weak CH₄ sink or source. Soil C density (0–25 cm) under mulch (12.5 kg C m⁻²) was greater that under lawn (8.0 kg C m⁻²). On a carbon dioxide equivalent (CO₂-e) basis, soil N₂O emissions offset the benefits of soil CH₄ uptake. Mulched garden areas provide greatest C sequestration potential in soil and vegetation and the smallest non-CO₂ emissions, as soil CH₄ uptake offsets a large fraction of soil N₂O emissions. Results of this study suggest that reducing the irrigation and fertiliser application to lawns can help mitigate GHG emissions from urban garden systems, and increasing the area of mulched perennial garden beds can also provide net GHG benefits; however, this needs to be tested in other garden systems with different soil types and environmental conditions.