Despite growing interest in urban resilience, remarkably little is known about vegetation dynamic... more Despite growing interest in urban resilience, remarkably little is known about vegetation dynamics in the aftermath of a major urban flooding. In this study, we examined the composition and structure of plant communities across New Orleans (Louisiana, USA) following catastrophic flooding triggered by levee failures during Hurricane Katrina in 2005. Focusing on eight neighborhoods that span a range of demographic and topographical conditions, we assessed whether plant communities in post-Katrina New Orleans reflect flooding disturbance and post-disaster landscape management policies. We then contextualized vegetation patterns and associated ecosystem services and disservices with census-based demographic trends and in- depth interviews to draw inferences about the drivers and outcomes of urban land abandonment in the aftermath of catastrophic disaster. We found that areas subject to the greatest flooding disturbance exhibit the highest rates of vegetation response. Disturbance intensity and elevation, however, are relatively weak drivers of vegetation differences among the studied neighborhoods. Rather, we found that household income, racial demographics, and land abandonment intensity are important drivers of vegetation community composition and structure across the city following Hurricane Katrina. Our findings indicate that resettlement and landscape management policies can mediate post-flooding ecological outcomes, and further that unmanaged, emergent vegetation on abandoned lands can be an environmental justice concern in underserved communities.
ABSTRACT As urbanization can involve multiple alterations to the soil environment, it is uncertai... more ABSTRACT As urbanization can involve multiple alterations to the soil environment, it is uncertain how urbanization effects soil nitrogen cycling. We established 22-0.04 ha plots in six different land cover types—rural slash pine (Pinus elliottii) plantations (n = 3), rural natural pine forests (n = 3), rural natural oak forests (n = 4), urban pine forests (n = 3), urban oak forests (n = 4) and urban lawns (n = 5) to investigate how net soil nitrogen mineralization rates and soil microbial biomass differed between urban forests and rural forests and between urban forests and urban lawns in the Florida panhandle. Urban forest sites have 2.5 times as much net total nitrogen mineralized than rural forest sites based on the mean daily rates averaged over the 2 years study (2010-2012). Urbanization may increase soil microbial biomass and activity (potential carbon mineralization rates) and this may be influencing the soil nitrogen mineralization rates in the forest sites. To include an urban lawn (turfgrass) component in the study, one time measurements of soils from the aforementioned forest sites and from urban lawn sites (no fertilization, no irrigation) were collected in 2012. Urban forest sites and urban lawns sites do not differ in their potential carbon mineralization rates, potential net total nitrogen mineralization rates or microbial biomass carbon and nitrogen contents. However, lawns have a higher potential net nitrification rate compared to urban forests.
Background/Question/Methods The Gulf Coast of Florida has been considered a “hotspot” of populati... more Background/Question/Methods The Gulf Coast of Florida has been considered a “hotspot” of population growth and very few studies exist that focus on the impact of land use change on biogeochemical cycling along coastlines. Previous research in the Florida Panhandle has indicated that shifts in land use from pine flatwoods and maritime forests to urban forests increase carbon storage in the top 90 cm of the mineral soil. As an example, urban forest pine dominated sites can have a forest floor mass of 97 Mg ha-1, a significantly higher mass than that stored in the forest floor of pine plantations and naturally regenerating forest (33 to 38 Mg ha-1, respectively). The focus of this research is to investigate the impact of land use change on carbon and nutrient cycling by measuring foliar decomposition rates, nitrogen mineralization and microbial biomass over a two year period. Plots representing five different land use types (pine plantation, urban pine forest, urban oak forest, natural...
Ecosystem benefits from trees are linked directly to the amount of healthy urban forest canopy co... more Ecosystem benefits from trees are linked directly to the amount of healthy urban forest canopy cover. Urban forest cover is dynamic and changes over time due to factors such as urban development, windstorms, tree removals, and growth. The amount of a city's canopy cover depends on its land use, climate, and people's preferences. This fact sheet examines how tree cover changes over time, how tree composition and location influence urban forest canopy and leaf area, and how tree and ground surface covers vary across Gainesville.
A city's trees reduce its energy use year round. In warm months trees shade buildings and pro... more A city's trees reduce its energy use year round. In warm months trees shade buildings and provide evaporative cooling, and in cold months they block icy winter winds. Trees near a building tend to reduce air conditioning use in that building in the summer months. The same trees can either increase or decrease energy use in a building during the winter months depending where the trees are in relation to the building. Knowing the size of a given building and the sizes and positions of the trees near it will enable us to place an economic value on the trees based on how much they reduce or increase energy use in the building.
We present information on the urban forests and land uses within the watershed of Puerto Rico’s 2... more We present information on the urban forests and land uses within the watershed of Puerto Rico’s 21 658-ha San Juan Bay Estuary based on urban forest inventories undertaken in 2001 and 2011. We found 2548 ha of mangrove and subtropical moist secondary forests covering 11.8 percent of the total watershed area in 2011. Red, black, and white mangroves (Rhizophora mangle, Avicennia germinans, and Laguncularia racemosa) were the most common species due to the watershed’s extensive mangrove forests, while tulipan africano (Spathodea campanulata) and María (Calophyllum antillanum) were predominant species in the moist forest patches and developed land uses. Approximately 10.1 million trees created an average tree cover of 24.1 percent, stored 319 737 metric tons of carbon (C) and sequestered C at a rate of 28 384 metric tons/year. This stored C had an estimated value of $8.1 million with an annual C sequestration value of $718,113 in 2011, up from the 2001 values. In 2011 approximately 19 0...
Background/Question/Methods Urban watersheds are heterogeneous, often including complex forest st... more Background/Question/Methods Urban watersheds are heterogeneous, often including complex forest structure and dynamics. Our understanding of the importance of legacy in hydric forest systems is lacking for subtropical urban watersheds. This study focused on hydric sites in the Hillsborough River watershed within the greater Tampa Bay Watershed, Florida. The area was divided into a grid of 0.17 m2 hexagons with a random sample point selected in each. A total of 500 plots, each 400 m2, were inventoried. Of these, 83 were identified as hydric (within 15 m of a hydric feature such as a stream, river, lake, or wetland). For each plot, diameter at breast height (dbh) for trees ≥ 2.5 cm dbh was measured by species. Based on aerial photography and site visits, each plot was assigned a legacy class—remnant (forest, pre-1948), emergent (forest, post 1948), and managed (actively managed grass on the plot). A hierarchical agglomerative cluster analysis identified community types within a legacy ...
ABSTRACT Urbanization can alter nutrient cycling. This research evaluated how urbanization affect... more ABSTRACT Urbanization can alter nutrient cycling. This research evaluated how urbanization affected nutrient dynamics in the subtropics. We established 17-0.04 ha plots in five different land cover types—slash pine (Pinus elliottii) plantations (n = 3), rural natural pine forests (n = 3), rural natural oak forests (n = 4), urban pine forests (n = 3) and urban oak forests (n = 4) in the Florida panhandle, a subtropical region that has experienced rapid urbanization. On each plot, we measured the decomposition of mixed species foliar litter, the nutrient release patterns in decomposing litter, foliar litter quality, and forest floor temperatures. Aboveground net primary productivity and soil carbon and nitrogen contents were also measured to characterize the carbon and nitrogen stocks and fluxes in the urban and rural sites. Litter decay rates, liter quality indices and nutrient release patterns in decomposing litter did not differ among urban and rural forests despite differences in forest floor temperatures between urban and rural sites. Urban forest floor temperatures are on average warmer by 0.63 °C in the winter (p = 0.005) and tend to have a more narrow temperature range than those of the rural forested sites. Foliar mass was measured over an 82 week period that was characterized by drought, which may have masked an urbanization effect. Urban forest land covers had higher aboveground net primary productivity and foliar productivity compared to rural land covers. This increased input of foliar carbon is not reflected in statistically different forest floor or surface soil (0-7.5 cm) carbon contents between urban and rural sites. Understanding how drought interacts with other drivers of change in urban systems may be a necessary component of city specific ecological knowledge.
We examined the spatial distribution, occurrence, and socioecological predictors of woody invasiv... more We examined the spatial distribution, occurrence, and socioecological predictors of woody invasive plants (WIP) in two subtropical, coastal urban ecosystems: San Juan, Puerto Rico and Miami-Dade, United States. These two cities have similar climates and ecosystems typical of subtropical regions but differ in socioeconomics, topography, and urbanization processes. Using permanent plot data, available forest inventory protocols and statistical analyses of geographic and socioeconomic spatial predictors, we found that landscape level distribution and occurrence of WIPs was not clustered. We also characterized WIP composition and occurrence using logistic models, and found they were strongly related to the proportional area of residential land uses. However, the magnitude and trend of increase depended on median household income and grass cover. In San Juan, WIP occurrence was higher in areas of high residential cover when incomes were low or grass cover was low, whereas the opposite wa...
Urban environments are key to the future of human-kind in terms of commerce, importance of green ... more Urban environments are key to the future of human-kind in terms of commerce, importance of green space to health, happiness, equity and productivity, to lowland biodiversity, and lessons on limits to growth and sustainability. In this presentation we review current knowledge of urban change ecology, the nature of chronic and catastrophic disruption, and the mechanisms of, and management for living and recovering within the context of dynamic physical, social and biological systems. Urban resilience to disasters is a very important and timely topic given all the earthquakes, fires, floods, tsunami's, dust storms that have occurred, particularly around the Pacific Rim in the past few years. Urban ecology was born after WW11 in Europe with the Sukopp and others who studied "dynamic" vegetation change. Since then we have categorised the vegetation of urban environments, explored the relationships between plants and animals and the urban environment, investigated ways of studying the biological-sociological, cultural and economies of cities with a special focus on human well being, the values of biodiversity to the provision of ecosystem services and the value of biodiversity to humans. It has become a reality that not only are we experiencing a rise in global temperatures but the climate is becoming more unpredictable. In this presentation we focus on the ecology and biodiversity aspects of natural disasters and how these might affect cities. We use examples from recent earthquakes, hurricanes, shrinking cities, new primal sites, new plant successions, and new dynamics between vegetation, invertebrates and vertebrates.
ABSTRACT Background/Question/Methods Understanding variables that are associated with higher or l... more ABSTRACT Background/Question/Methods Understanding variables that are associated with higher or lower aboveground carbon in forest ecosystems will aid in managing our forest resources for reducing carbon emissions through sequestration in plant biomass. We tested the effect of land use (as a proxy of anthropogenic influence on forest ecosystems), tree density, vegetation cover, species diversity, composition, and richness on aboveground carbon using data from urban forests in San Juan Puerto Rico. These variables interact with each other; therefore, they have both direct and indirect effects, via intermediate variable, on aboveground carbon. We teased out these relationships using structural equation modeling. Results/Conclusions Percentage tree cover had a significant positive effect on species composition, species diversity, basal area, and aboveground carbon. Species composition and basal area also affected aboveground carbon positively; however, species diversity did not have a statistically significant influence on carbon. Land use also had significant direct and indirect effects on the aboveground. The direct effect of land use was lower than its indirect effect via tree density. Our study indicated that land use, tree density, and species composition are important predictors of aboveground carbon and these issues should be addressed while managing our forest resources, especially in urban areas.
In order to understand the effect of urban development on the functioning of forest ecosystems, d... more In order to understand the effect of urban development on the functioning of forest ecosystems, during the past decade we have been studying red oak stands located on similar soil along an urban-rural gradient running from New York City ro rural Litchfield County, Connecticut. This paper summarizes the results of this work. Field measurements, controlled laboratory experiments, and reciprocal transplants documented soil pollution, soil hydrophobicity, litter decomposition rates, total soil carbon, potential nitrogen mineralization, nitrification, fungal biomass, and earthworm populations in forests along the 140 × 20 km study transect. The results revealed a complex urban-rural environmental gradient. The urban forests exhibit unique ecosystem structure and function in relation to the suburban and rural forest stands; these are likely linked to stresses of the urban environment such as air pollution, which has also resulted in elevated levels of heavy metals in the soil, the positive effects of the heat island phenomenon, and the presence of earthworms. The data suggest a working model to guide mechanistic work on the ecology of forests along urban-to-rural gradients, and for comparison of different metropolitan areas.
Despite growing interest in urban resilience, remarkably little is known about vegetation dynamic... more Despite growing interest in urban resilience, remarkably little is known about vegetation dynamics in the aftermath of a major urban flooding. In this study, we examined the composition and structure of plant communities across New Orleans (Louisiana, USA) following catastrophic flooding triggered by levee failures during Hurricane Katrina in 2005. Focusing on eight neighborhoods that span a range of demographic and topographical conditions, we assessed whether plant communities in post-Katrina New Orleans reflect flooding disturbance and post-disaster landscape management policies. We then contextualized vegetation patterns and associated ecosystem services and disservices with census-based demographic trends and in- depth interviews to draw inferences about the drivers and outcomes of urban land abandonment in the aftermath of catastrophic disaster. We found that areas subject to the greatest flooding disturbance exhibit the highest rates of vegetation response. Disturbance intensity and elevation, however, are relatively weak drivers of vegetation differences among the studied neighborhoods. Rather, we found that household income, racial demographics, and land abandonment intensity are important drivers of vegetation community composition and structure across the city following Hurricane Katrina. Our findings indicate that resettlement and landscape management policies can mediate post-flooding ecological outcomes, and further that unmanaged, emergent vegetation on abandoned lands can be an environmental justice concern in underserved communities.
ABSTRACT As urbanization can involve multiple alterations to the soil environment, it is uncertai... more ABSTRACT As urbanization can involve multiple alterations to the soil environment, it is uncertain how urbanization effects soil nitrogen cycling. We established 22-0.04 ha plots in six different land cover types—rural slash pine (Pinus elliottii) plantations (n = 3), rural natural pine forests (n = 3), rural natural oak forests (n = 4), urban pine forests (n = 3), urban oak forests (n = 4) and urban lawns (n = 5) to investigate how net soil nitrogen mineralization rates and soil microbial biomass differed between urban forests and rural forests and between urban forests and urban lawns in the Florida panhandle. Urban forest sites have 2.5 times as much net total nitrogen mineralized than rural forest sites based on the mean daily rates averaged over the 2 years study (2010-2012). Urbanization may increase soil microbial biomass and activity (potential carbon mineralization rates) and this may be influencing the soil nitrogen mineralization rates in the forest sites. To include an urban lawn (turfgrass) component in the study, one time measurements of soils from the aforementioned forest sites and from urban lawn sites (no fertilization, no irrigation) were collected in 2012. Urban forest sites and urban lawns sites do not differ in their potential carbon mineralization rates, potential net total nitrogen mineralization rates or microbial biomass carbon and nitrogen contents. However, lawns have a higher potential net nitrification rate compared to urban forests.
Background/Question/Methods The Gulf Coast of Florida has been considered a “hotspot” of populati... more Background/Question/Methods The Gulf Coast of Florida has been considered a “hotspot” of population growth and very few studies exist that focus on the impact of land use change on biogeochemical cycling along coastlines. Previous research in the Florida Panhandle has indicated that shifts in land use from pine flatwoods and maritime forests to urban forests increase carbon storage in the top 90 cm of the mineral soil. As an example, urban forest pine dominated sites can have a forest floor mass of 97 Mg ha-1, a significantly higher mass than that stored in the forest floor of pine plantations and naturally regenerating forest (33 to 38 Mg ha-1, respectively). The focus of this research is to investigate the impact of land use change on carbon and nutrient cycling by measuring foliar decomposition rates, nitrogen mineralization and microbial biomass over a two year period. Plots representing five different land use types (pine plantation, urban pine forest, urban oak forest, natural...
Ecosystem benefits from trees are linked directly to the amount of healthy urban forest canopy co... more Ecosystem benefits from trees are linked directly to the amount of healthy urban forest canopy cover. Urban forest cover is dynamic and changes over time due to factors such as urban development, windstorms, tree removals, and growth. The amount of a city's canopy cover depends on its land use, climate, and people's preferences. This fact sheet examines how tree cover changes over time, how tree composition and location influence urban forest canopy and leaf area, and how tree and ground surface covers vary across Gainesville.
A city's trees reduce its energy use year round. In warm months trees shade buildings and pro... more A city's trees reduce its energy use year round. In warm months trees shade buildings and provide evaporative cooling, and in cold months they block icy winter winds. Trees near a building tend to reduce air conditioning use in that building in the summer months. The same trees can either increase or decrease energy use in a building during the winter months depending where the trees are in relation to the building. Knowing the size of a given building and the sizes and positions of the trees near it will enable us to place an economic value on the trees based on how much they reduce or increase energy use in the building.
We present information on the urban forests and land uses within the watershed of Puerto Rico’s 2... more We present information on the urban forests and land uses within the watershed of Puerto Rico’s 21 658-ha San Juan Bay Estuary based on urban forest inventories undertaken in 2001 and 2011. We found 2548 ha of mangrove and subtropical moist secondary forests covering 11.8 percent of the total watershed area in 2011. Red, black, and white mangroves (Rhizophora mangle, Avicennia germinans, and Laguncularia racemosa) were the most common species due to the watershed’s extensive mangrove forests, while tulipan africano (Spathodea campanulata) and María (Calophyllum antillanum) were predominant species in the moist forest patches and developed land uses. Approximately 10.1 million trees created an average tree cover of 24.1 percent, stored 319 737 metric tons of carbon (C) and sequestered C at a rate of 28 384 metric tons/year. This stored C had an estimated value of $8.1 million with an annual C sequestration value of $718,113 in 2011, up from the 2001 values. In 2011 approximately 19 0...
Background/Question/Methods Urban watersheds are heterogeneous, often including complex forest st... more Background/Question/Methods Urban watersheds are heterogeneous, often including complex forest structure and dynamics. Our understanding of the importance of legacy in hydric forest systems is lacking for subtropical urban watersheds. This study focused on hydric sites in the Hillsborough River watershed within the greater Tampa Bay Watershed, Florida. The area was divided into a grid of 0.17 m2 hexagons with a random sample point selected in each. A total of 500 plots, each 400 m2, were inventoried. Of these, 83 were identified as hydric (within 15 m of a hydric feature such as a stream, river, lake, or wetland). For each plot, diameter at breast height (dbh) for trees ≥ 2.5 cm dbh was measured by species. Based on aerial photography and site visits, each plot was assigned a legacy class—remnant (forest, pre-1948), emergent (forest, post 1948), and managed (actively managed grass on the plot). A hierarchical agglomerative cluster analysis identified community types within a legacy ...
ABSTRACT Urbanization can alter nutrient cycling. This research evaluated how urbanization affect... more ABSTRACT Urbanization can alter nutrient cycling. This research evaluated how urbanization affected nutrient dynamics in the subtropics. We established 17-0.04 ha plots in five different land cover types—slash pine (Pinus elliottii) plantations (n = 3), rural natural pine forests (n = 3), rural natural oak forests (n = 4), urban pine forests (n = 3) and urban oak forests (n = 4) in the Florida panhandle, a subtropical region that has experienced rapid urbanization. On each plot, we measured the decomposition of mixed species foliar litter, the nutrient release patterns in decomposing litter, foliar litter quality, and forest floor temperatures. Aboveground net primary productivity and soil carbon and nitrogen contents were also measured to characterize the carbon and nitrogen stocks and fluxes in the urban and rural sites. Litter decay rates, liter quality indices and nutrient release patterns in decomposing litter did not differ among urban and rural forests despite differences in forest floor temperatures between urban and rural sites. Urban forest floor temperatures are on average warmer by 0.63 °C in the winter (p = 0.005) and tend to have a more narrow temperature range than those of the rural forested sites. Foliar mass was measured over an 82 week period that was characterized by drought, which may have masked an urbanization effect. Urban forest land covers had higher aboveground net primary productivity and foliar productivity compared to rural land covers. This increased input of foliar carbon is not reflected in statistically different forest floor or surface soil (0-7.5 cm) carbon contents between urban and rural sites. Understanding how drought interacts with other drivers of change in urban systems may be a necessary component of city specific ecological knowledge.
We examined the spatial distribution, occurrence, and socioecological predictors of woody invasiv... more We examined the spatial distribution, occurrence, and socioecological predictors of woody invasive plants (WIP) in two subtropical, coastal urban ecosystems: San Juan, Puerto Rico and Miami-Dade, United States. These two cities have similar climates and ecosystems typical of subtropical regions but differ in socioeconomics, topography, and urbanization processes. Using permanent plot data, available forest inventory protocols and statistical analyses of geographic and socioeconomic spatial predictors, we found that landscape level distribution and occurrence of WIPs was not clustered. We also characterized WIP composition and occurrence using logistic models, and found they were strongly related to the proportional area of residential land uses. However, the magnitude and trend of increase depended on median household income and grass cover. In San Juan, WIP occurrence was higher in areas of high residential cover when incomes were low or grass cover was low, whereas the opposite wa...
Urban environments are key to the future of human-kind in terms of commerce, importance of green ... more Urban environments are key to the future of human-kind in terms of commerce, importance of green space to health, happiness, equity and productivity, to lowland biodiversity, and lessons on limits to growth and sustainability. In this presentation we review current knowledge of urban change ecology, the nature of chronic and catastrophic disruption, and the mechanisms of, and management for living and recovering within the context of dynamic physical, social and biological systems. Urban resilience to disasters is a very important and timely topic given all the earthquakes, fires, floods, tsunami's, dust storms that have occurred, particularly around the Pacific Rim in the past few years. Urban ecology was born after WW11 in Europe with the Sukopp and others who studied "dynamic" vegetation change. Since then we have categorised the vegetation of urban environments, explored the relationships between plants and animals and the urban environment, investigated ways of studying the biological-sociological, cultural and economies of cities with a special focus on human well being, the values of biodiversity to the provision of ecosystem services and the value of biodiversity to humans. It has become a reality that not only are we experiencing a rise in global temperatures but the climate is becoming more unpredictable. In this presentation we focus on the ecology and biodiversity aspects of natural disasters and how these might affect cities. We use examples from recent earthquakes, hurricanes, shrinking cities, new primal sites, new plant successions, and new dynamics between vegetation, invertebrates and vertebrates.
ABSTRACT Background/Question/Methods Understanding variables that are associated with higher or l... more ABSTRACT Background/Question/Methods Understanding variables that are associated with higher or lower aboveground carbon in forest ecosystems will aid in managing our forest resources for reducing carbon emissions through sequestration in plant biomass. We tested the effect of land use (as a proxy of anthropogenic influence on forest ecosystems), tree density, vegetation cover, species diversity, composition, and richness on aboveground carbon using data from urban forests in San Juan Puerto Rico. These variables interact with each other; therefore, they have both direct and indirect effects, via intermediate variable, on aboveground carbon. We teased out these relationships using structural equation modeling. Results/Conclusions Percentage tree cover had a significant positive effect on species composition, species diversity, basal area, and aboveground carbon. Species composition and basal area also affected aboveground carbon positively; however, species diversity did not have a statistically significant influence on carbon. Land use also had significant direct and indirect effects on the aboveground. The direct effect of land use was lower than its indirect effect via tree density. Our study indicated that land use, tree density, and species composition are important predictors of aboveground carbon and these issues should be addressed while managing our forest resources, especially in urban areas.
In order to understand the effect of urban development on the functioning of forest ecosystems, d... more In order to understand the effect of urban development on the functioning of forest ecosystems, during the past decade we have been studying red oak stands located on similar soil along an urban-rural gradient running from New York City ro rural Litchfield County, Connecticut. This paper summarizes the results of this work. Field measurements, controlled laboratory experiments, and reciprocal transplants documented soil pollution, soil hydrophobicity, litter decomposition rates, total soil carbon, potential nitrogen mineralization, nitrification, fungal biomass, and earthworm populations in forests along the 140 × 20 km study transect. The results revealed a complex urban-rural environmental gradient. The urban forests exhibit unique ecosystem structure and function in relation to the suburban and rural forest stands; these are likely linked to stresses of the urban environment such as air pollution, which has also resulted in elevated levels of heavy metals in the soil, the positive effects of the heat island phenomenon, and the presence of earthworms. The data suggest a working model to guide mechanistic work on the ecology of forests along urban-to-rural gradients, and for comparison of different metropolitan areas.
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Papers by Wayne Zipperer