Mangrove forests store high densities of carbon across the tropical urban landscape of Singapore

Tropical forested ecosystems provide multiple ecosystem services to rural and urban landscapes, with carbon storage gaining particular attention. Deforestation due to rural-urban transitions may lead to a reduction in carbon storage ability. Coastal mangrove forests are particularly at risk from deforestation due to their location in the rapidly urbanizing coastal zone, and the city state of Singapore is an extreme example, losing as much as 90 % of its original mangrove cover due to land reclamation and reservoir construction. Knowledge of mangrove ecosystem services may allow better conservation, restoration and incorporation of remaining mangrove patches into the urban landscape. Focusing on the regulating ecosystem service of carbon storage, mangrove carbon stocks have been estimated for Singapore using a combination of field and remote sensing techniques. Biomass carbon showed substantial spatial variation, with old, contiguous mangrove patches containing a higher density of biomass carbon than fragmented, river-fringing or restored mangroves. In total, national biomass carbon equated to 116,117.1 megagrams of carbon (Mg C), and a coarse estimate of the total carbon stock (including soil carbon) suggests that Singapore’s mangroves may store 450,571.7 Mg C. While lower than other regional estimates focused on natural, oceanic mangroves, this is a significant carbon stock for a disturbed, urban mangrove system, and may be equivalent to the average annual carbon emissions of 621,000 residents. This analysis, alongside a review of other urban forest studies, highlights the importance of forested ecosystems such as mangroves in providing a carbon storage ecosystem service to urban areas.     

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.     

Forest soils adjacent to urban interstates: Soil physical and chemical properties,heavy metals,disturbance legacies,and relationships with woody vegetation

While urban ecology is an expanding field of study, some natural areas within the urban environment remain under-examined. These include naturally regenerating forest communities adjacent to urban interstates. In addition, the status of interstate soils and their relationships with the community composition of forested interstate verges has received little ecological study. The purpose of this study was to examine variation in soil conditions along forested interstate corridors in Louisville, KY and to explore the extent to which soil characteristics (e.g., bulk density, pH) and heavy metals (e.g., Pb, Zn) vary with respect to three factors: interstate (e.g., traffic density), surrounding urban environment (e.g., industrial land use), and interstate construction legacies. Additionally, we explored the relationships between several edaphic factors and woody vegetation structure in these forested verges. We found that the degree and direction of the slope of land towards the interstate and the distance to the interstate pavement were strong determinants of soil characteristics and heavy metal concentrations, suggesting that the movement of de-icing salts, heavy metals, and other pollutants from the interstate was important in determining forest soil conditions along urban interstates. Since within our study area these highways did not extend into rural lands, variation in urban land uses and cover within 26 km of the city center was not large enough to explain variation in soil characteristics or heavy metals, except for a positive correlation between chromium and surrounding industrial land use. We did find that past physical soil disturbance caused by interstate construction (e.g., imported fill) left an important legacy on soil characteristics, heavy metal retention, and woody plant growth patterns in forests adjacent to urban interstates. The legacy of interstate construction on the current forest community structure (e.g., lower species richness) and the future forest (e.g., reduced tree regeneration) may further alter ecosystem productivity and ecosystem services provided by these forests and their soils.     

Evaluating the distribution of invasive woody vegetation around riparian corridors in relation to land use

Invasive species have been causing important and irreversible impacts to native species and communities of ecosystems. They distort ecosystem functions by degrading forest lands, wetlands, and agricultural habitats and replace the native vegetation and reduce biodiversity, forest productivity, and suitable wildlife habitat. To address disturbances caused by invasive species occurrence, further information is needed regarding the occurrence, extent, and dispersal of invasive species and how land use may increase the spread of these species. The objective of this study was to find the frequency and dominance of three invasive species common to riparian areas of east Alabama: Ligustrum sinense (Chinese privet), Elaeagnus pungens (silverthorn), and Triadica sebifera (Chinese tallow tree). Surveys of these species in riparian forests in and around Auburn, Alabama were conducted to show the relative extent of these shrubs and their relation to urban land use. It was expected to see the highest levels of invasive species in the city center with decreasing levels radiating outward into rural areas. Another objective was how urban land use may affect the presence-absence and prevalence of these non-native plant species within study sites. The results showed that around the city center and suburban lands, cover of both Chinese privet and silverthorn tended to increase. In contrast, Chinese tallow tree density percent cover showed an opposite trend with landscapes close to city center often having slightly less cover. This study shows that urban land use may be an important association with distribution of invasive plant species.     

Canopy precipitation interception in urban forests in relation to stand structure

Urban forests provide important ecosystem services. In terms of hydrological benefits, forest ecosystems in urban environments represent qualitative and quantitative filter for rainwater. We quantified the canopy interception in relation to urban forest stand structure and rainfall intensity in an urban transect of the mixed (upland) forest in the city centre, towards a riparian pine forest and a floodplain hardwood forest in the City of Ljubljana, Slovenia. Bulk precipitation in open areas and throughfall were measured with fixed rainfall collectors in each forest. Stemflow was estimated from a review of relevant literature. We found that canopy interception in selected urban forests was mainly affected by tree species composition and other stand structure variables, such as canopy cover and tree dimensions. Average annual canopy interception was highest in the mixed forest (18.0% of bulk precipitation), while the riparian pine forest had the lowest level (3.9% of bulk precipitation) and the floodplain hardwood forest had the intermediate level for interception (7.1% of bulk precipitation). The mixed forest exhibited the stand structure factors that contributed to the highest canopy interception among the studied forests: high assemblage of dominant coniferous trees, denser canopy cover and the highest growing stock. Furthermore, rainfall intensity has proven to be an important factor for the seasonal partitioning (comparing the leafed and leafless period) of canopy interception. A better understanding of precipitation interception processes in urban forests is needed to assist urban forest managing and planning, aiming at maximizing canopy interception for the mitigation of stormwater runoff and flooding in urbanized watershed.     

Modeling above-ground carbon storage: a remote sensing approach to derive individual tree species information in urban settings

Vegetation has gained importance in respective debates about climate change mitigation and adaptation in cities. Although recently developed remote sensing techniques provide necessary city-wide information, a sufficient and consistent city-wide information of relevant urban ecosystem services, such as carbon emissions offset, does not exist. This study uses city-wide, high-resolution, and remotely sensed data to derive individual tree species information and to estimate the above-ground carbon storage of urban forests in Berlin, Germany. The variance of tree biomass was estimated using allometric equations that contained different levels of detail regarding the tree species found in this study of 700 km², which had a tree canopy of 213 km². The average tree density was 65 trees/ha per unit of tree cover and a range from 10 to 40 trees/ha for densely urban land cover. City-wide estimates of the above-ground carbon storage ranged between 6.34 and 7.69 tC/ha per unit of land cover, depending on the level of tree species information used. Equations that did not use individually localized tree species information undervalued the total amount of urban forest carbon storage by up to 15 %. Equations using a generalized estimate of dominant tree species information provided rather precise city-wide carbon estimates. Concerning differences within a densely built area per unit of land cover approaches using individually localized tree species information prevented underestimation of mid-range carbon density areas (10–20 tC/ha), which were actually up to 8.4 % higher, and prevented overestimation of very low carbon density areas (0–5 tC/ha), which were actually up to 11.4 % lower. Park-like areas showed 10 to 30 tC/ha, whereas land cover of very high carbon density (40–80 tC/ha) mostly consisted of mixed peri-urban forest stands. Thus, this approach, which uses widely accessible and remotely sensed data, can help to improve the consistency of forest carbon estimates in cities.     

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.     

The effects of landscape cover on surface soils in a low density residential neighborhood in Baltimore,Maryland

Previous studies at the scale of a city have shown that surface soil nutrients, pH, and soil organic matter (SOM) can vary by land cover, land use, and management. This study was conducted in Baltimore County, Maryland, to quantify the differences in characteristics of soil in a residential neighborhood and adjacent forest patch sampling at a fine scale. The first objective was to compare soil characteristics in a residential neighborhood among ecotope types of forest, lawn, and planting beds that were underlain by the same parent material and thus only differed in plant cover. Another objective was to examine differences in soil properties of lawn soils that differed in age by 10 years. The final objective was to quantify the variation of these residential and forest soils. Composite soil samples from the surface to a depth of 5 cm were taken from planting beds and lawns from 50 residences and an adjacent forest patch. Results showed that the forest soil had 30 % more SOM and was more acidic than lawn soil. Conversely, Mg, P, K, and Ca were 47 to 67 % lower in forest compared to lawn soils even though both soils developed from similar parent materials. For the residential lawns, the older development had significantly higher concentration of soil P. There was also a difference between front and back lawns where front lawns had 26 and 10 % higher concentrations of Ca and Mg, respectively, and a higher pH than the back lawns. Finally, the variation of soil characteristics of all areas sampled, from lowest to highest was pH < SOM < K < Mg < Ca < P. Results of this study suggest that anthropogenic factors appear to overwhelm natural soil forming factors in suburban residential areas in the Baltimore metropolitan area and these differences appear to increase with time.     

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.     

Exotic plant invasions in forested wetlands: effects of adjacent urban land use type

There are a variety of land use types in urbanized areas that may have different effects on the ecological characteristics of patches of natural vegetation. In particular, residential housing and industrial land-use may have different effects on adjacent forest communities. We tested this hypothesis by examining the vegetation of forested wetlands in a densely urban region, northeastern New Jersey. Wetlands embedded in industrial areas were much less invaded by exotic plant species than were wetlands embedded in residential areas, as reflected in the number of exotic species, the fraction of the total flora that was exotic, and their frequencies of occurrence. Few other structural characteristics of the vegetation differed between the two types of urban areas. We suggest that the management of land adjacent to forest edges may explain this surprising result. The low rate of invasion of wetlands within industrial areas suggests they could have high conservation value in urban ecosystems.     

Trampling tolerance of understorey vegetation in different hemiboreal urban forest site types in Finland

The effects of trampling on the understorey vegetation were studied in boreal urban forests of different fertility in the greater Helsinki area, Finland. The three studied forest types in decreasing order of fertility were: 1) herb-rich heath forest, 2) mesic heath forest, and 3) sub-xeric heath forest. We inventoried the cover percentages of understorey vegetation in 40 herb-rich, 75 mesic and 40 sub-xeric biotopes located in 51 urban forests varying in size (0.6–502 ha). Cover percentages were compared to those of untrampled reference areas. In our study, trampling tolerance increased with increasing fertility of the forest type. Wear of understorey vegetation correlated positively with the number of residents (i.e. recreational pressure) around the forest patch. In general, understorey vegetation cover in all three forest types was lower than in the same forest types in untrampled reference areas. Ground layer cover in urban forests was less than half of that in reference areas. Mosses, lichens, and dwarf shrubs, especially Vaccinium vitis-idaea, proved to be sensitive to trampling and consequently decreased in cover. The cover of tree saplings, mainly Sorbus aucuparia, and some resilient herbs increased.     

Functions of riparian forest in urban catchments: a case study from sub-tropical Brisbane,Australia

Riparian forests are vital for maintaining healthy stream ecosystems; acting as buffers against nutrient and contaminant inputs, contributing energy subsidies and providing favorable instream habitat conditions. In urban catchments riparian forests are often degraded or cleared, removing the ecosystem functions the forest provides. Intact riparian forest along urban waterways, may mitigate some aspects of degradation associated with an urbanized catchment. In Bulimba Creek, an urbanized catchment in southeast Queensland, Australia, we investigated some ecosystem functions provided by riparian forest. We found that during baseflow periods a forested riparian corridor provided energy subsidies to the stream through litterfall and had a controlling influence on instream production through shading. Denitrification potential of benthic sediments increased with increasing levels of woody debris and organic matter, deposited from riparian vegetation. Denitrification was nitrate limited, indicating some potential to reduce nitrate loads in the stream. Riparian soils also showed moderate denitrification potential; which, through management strategies, could be utilized to reduce excess nitrate loads. These results suggest that riparian forests provide important functions for urban streams; highlighting the importance of conserving forest remnants in urban landscapes and the usefulness of replanting degraded riparian forest to enhance stream health and habitat condition.     

Ecosystem services from converted land: the importance of tree cover in Amazonian pastures

Deforestation is responsible for a substantial fraction of global carbon emissions and changes in surface energy budgets that affect climate. Deforestation losses include wildlife and human habitat, and myriad forest products on which rural and urban societies depend for food, fiber, fuel, fresh water, medicine, and recreation. Ecosystem services gained in the transition from forests to pasture and croplands, however, are often ignored in assessments of the impact of land cover change. The role of converted lands in tropical areas in terms of carbon uptake and storage is largely unknown. Pastures represent the fastest-growing form of converted land use in the tropics, even in some areas of rapid urban expansion. Tree biomass stored in these areas spans a broad range, depending on tree cover. Trees in pasture increase carbon storage, provide shade for cattle, and increase productivity of forage material. As a result, increasing fractional tree cover can provide benefits land managers as well as important ecosystem services such as reducing conversion pressure on forests adjacent to pastures. This study presents an estimation of fractional tree cover in pasture in a dynamic region on the verge of large-scale land use change. An appropriate sampling interval is established for similar studies, one that balances the need for independent samples of sufficient number to characterize a pasture in terms of fractional tree cover. This information represents a useful policy tool for government organizations and NGOs interested in encouraging ecosystem services on converted lands. Using high spatial resolution remotely sensed imagery, fractional tree cover in pasture is quantified for the municipality of Rio Branco, Brazil. A semivariogram and devolving spatial resolution are employed to determine the coarsest sampling interval that may be used, minimizing effects of spatial autocorrelation. The coarsest sampling interval that minimizes spatial dependence was about 22 m. The area-weighted fractional tree cover for the study area was 1.85 %, corrected for a slight bias associated with the coarser sampling resolution. The pastures sampled for fractional tree cover were divided between ‘high’ and ‘low’ tree cover, which may be the result of intentional incorporation of arboreal species in pasture. Further research involving those ranchers that have a higher fractional tree cover may indicate ways to promote the practice on a broader scale in the region.     

Alien plant species do have a clear preference for different land uses within urban environments

Since neophytes can become invasive in the future, untangling their ecological preferences is of paramount importance, especially in urban areas where they represent a substantial proportion of the local flora. Studies exploring alien species assemblages in urban environments are however scarce. This study aims to unravel alien plant species preferences for five urban land uses (densely built-up areas, open built-up areas, industrial areas, broadleaved urban forests, and agricultural areas and small landscape elements). We took the city of Brussels as a model, in which we recorded all vascular species growing spontaneously in grid cells of 1 km². We tested two different ways of classifying the 1-km² cells: (1) We simply associated each cell with its dominant land cover; (2) We used a fuzzy approach for which the degree of association of a given cell to a given land cover depended on the proportion of that land cover within the cell. For both classification methods, we calculated the indicator species of the resulting land cover types based on alien species only. The crisp and fuzzy classifications identified 33 and 49 species, respectively, with a clear preference for some urban land use types (from a total of 129 alien plant species analyzed). Results showed that urban land use types having apparently similar environmental conditions can actually harbor different neophyte assemblages. Fine-tuning the categorization of urban environments in future ecological studies is therefore important for understanding spatial patterns of alien species occurrence.     

Direct and indirect effects of urbanization on soil and plant nutrients in desert ecosystems of the Phoenix metropolitan area,Arizona (USA)

Desert landscaping has become a dominant land cover type in arid US cities and often includes native plant species. Does replacement of native plant distribution in urban areas also reestablish ecological functioning characteristic of natural deserts? We compared ecological processes in three landscape types that are common to the metropolitan area of Phoenix, Arizona (USA): residential desert yards created from former lawns, Sonoran Desert preserves within the city, and Sonoran Desert preserves outside the city boundaries. Canopy cover, abundance of herbivorous insects, and soil properties (concentration of inorganic nitrogen (N), soil moisture and organic matter content, and water-holding capacity) were higher in residential desert yards than in native desert sites located both within and outside of the city. Furthermore, soil resources in desert yards were not organized around plant canopies, departing from the predictable resource island pattern that is characteristic of natural deserts. Intentional human manipulation and land use history accounts for these differences, while the urban environment contributes only subtly to soil N concentrations beneath plant canopies. While the use of desert landscaping may have important water conservation benefits, it does not help to mitigate the well-documented excess of reactive N within the Phoenix metropolitan area.     

Ecosystem services assessment of the urban forests of Addis Ababa,Ethiopia

Addis Ababa is a highland city with varied topography and landscape features. The mountains that surround the city are covered with urban forest of different types. These forests are providing various ecosystem services for the urban and peri-urban population of the city. Apart from surface temperature regulating function of the green spaces of Addis Ababa, no quantitative assessment of the carbon sequestration and soil protection ecosystem services provided by the urban forest has been conducted to date. The aim of this study was to assess selected ecosystem services such as carbon storage potential, habitat support and soil erosion protection provided by different categories of urban forest of Addis Ababa. The result showed that carbon density in the study area varied with forest categories viz. 293tons/ha, 142tons/ha and 132tons/ha in the dense, medium and open forest types respectively. The Shannon-Wiener diversity index is3.24 for Junipers dominated forest, 2.98 for mixed forest and 2.76 for Eucalyptus dominated forest. The formation of soil erosion features is significantly different among the Eucalyptus forest, Juniperus forest and Mixed forest where high incidence of soil erosion was recorded in the Eucalyptus forest. Therefore, irrespective of the environmental factors such as slope, aspect and elevation differences, there is an association between Eucalyptus forest cover and high soil erosion features. To ensure sustainable supply of ecosystem services and maintain a balanced urban environment, all green spaces in the city should be ecologically networked and diversified. Therefore, assessment of ecosystem services provided essential information for effective planning of the green space in terms of species composition and interconnectivity.     

Diversity,abundance, and species composition of ants in urban green spaces

Urbanization threatens biodiversity, yet the number and scope of studies on urban arthropod biodiversity are relatively limited. We sampled ant communities in three urban habitats (forest remnants, community gardens, vacant lots) in Detroit and Toledo, USA, to compare species richness, abundance, and species composition. We measured 24 site characteristics to examine relationships between richness and composition and habitat patch size, vegetation, and urban features. Ant richness was higher in forests (26) than in gardens (14) and intermediate in vacant lots (20). Ant richness in gardens and vacant lots negatively correlated with abundance of an exotic ant species (Tetramorium caespitum); thus this ant may affect native ant richness in urban habitats. Ant composition differed with habitat type, and abundance was lowest in forests. Site characteristics varied with habitat type: forests were larger, had more woody plants, higher woody plant richness, more branches, and leaf litter whereas lots and gardens had more concrete and buildings. Vacant lots had taller herbaceous vegetation, and gardens had higher forb richness, density, and more bare ground. Differences in vegetation did not correlate with ant richness, but several vegetation factors (e.g. patch size, number and size of trees, leaf litter, and amount of concrete and buildings) correlated with differences in ant species composition. Additional factors relating to soil, nests, or microclimatic factors may also be important for urban ant communities. Implications for biodiversity conservation in urban ecosystems are discussed.     

Gross primary productivity of a large metropolitan region in midsummer using high spatial resolution satellite imagery

Although gross primary productivity (GPP) is estimated with remote sensing over large regions of Earth, urban areas are usually excluded due to the lack of light use efficiency (LUE) parameters for urban vegetation and the spatial heterogeneity of urban land cover. Here, we estimated midsummer GPP, both within and among vegetation and land-use types, across the Minneapolis-Saint Paul, Minnesota metropolitan region. We derived LUE parameters for urban vegetation types using estimates of GPP from tree sap flow and eddy covariance CO₂ flux observations, and from fraction of absorbed photosynthetically active radiation based on 2 m resolution WorldView-2 satellite imagery. Mean GPP per unit land area (including vegetation, impervious surfaces, and soil) was 2.64 g C m^?2 d^?1, and was 4.45 g C m^?2 d^?1 per unit vegetated area. Mapped GPP estimates were within 11.4% of estimates from independent tall tower eddy covariance measurements. Turf grass GPP had a larger coefficient of variation (0.18) than other vegetation classes (~0.10). Vegetation composition was largely consistent across the study area. Excluding golf courses, mean land-use GPP for the total study area varied more by percent vegetation cover (R²?=?0.98, p?<?0.001) than by variability within vegetation classes (R²?=?0.21, p?=?0.19). Urban GPP in general was less than half that of natural forests and grasslands in the same climate zone.     

Spatio-temporal analysis of urban temperature in Bandung City,Indonesia

This study presents an evaluation of urban micro-climate about the exsistence level urban vegetation, in association with the urban temperature (surface temperature) and urban built-up area of Bandung City. The changes in urban vegetation cover, urban temperature, and urban built-up area observed using Landsat 5 TM and Landsat 7 ETM + bands were evaluated on the basis of the WDRVI (Wide Dynamic Range Vegetation Indices), NDBI (Normalized Difference Built-up Index), and SAVI (Soil-Adjusted Vegetation Index). It was found that, due to the uncontrolled urban growth and the removal of urban vegetation cover and urban green space, there was a significant increase in urban temperature, in NDBI, but a decrease in WDRVI. The maximum urban temperatures, NDBI, and the minimum values of WDRVI indices were established in 2009. Therefore the results indicate a significant effect of higher density of impervious surfaces coverage (urban built-up area) contributing significantly to the increase of urban temperature. Again the results also confirm that urban vegetation landscape coverage in the surrounding of industrial area reduced the urban temperature. Based on the results, we recommend the city government to provide more urban green space by cooperating with private land owner, in order to decrease urban temperature and create a healthier living environment for urban inhabitants.     

Hurricane driven changes in vegetation structure and ecosystem services in tropical urban yards: a study case in San Juan,Puerto Rico

Urban forests are valuable spaces for species conservation, protection of local biodiversity and provision of ecosystem services. However, they are also vulnerable to the impact of extreme climate events like hurricanes. Understanding how urban forests are responding to hurricane disturbances is crucial to improve their design, management, and resilience. Here we analyzed pre-and post-hurricane vegetation surveys in 52 residential yards in San Juan to assess urban forest responses after Hurricanes Irma and María impacted Puerto Rico in 2017. We used these surveys to compare vegetation structure and composition (including species-specific mortality and damage rates) and to quantify changes in the ecosystem services provided by these yards. We found that hurricane disturbances significantly altered the structure but not the composition of yard vegetation. We detected a 27% reduction and 31% mortality of standing stems, and a significant reduction in plants health. Yard species composition was dominated by non-native species and this trend did not change with hurricane disturbance. Changes in vegetation structure translated into substantial reductions in ecosystem services. Food provision, an important service provided by a large proportion of yards before the hurricane, reported the highest reduction (41.9%) while carbon storage was the service that changed the least (9%). Our combined results emphasize the key role played by residential yards providing ecosystem services in tropical cities and call for further efforts to manage private and public urban forests in ways that may ensure their resilience to mitigate extreme climate events, provide multiple ecosystem services, and promote long-term urban sustainability.