Urban Forest Landscape Research Articles

Associations between Road Density, Urban Forest Landscapes, and Structural-Taxonomic Attributes in Northeastern China: Decoupling and Implications

A better understanding on the associations between road density (RD), urban forest structural-taxonomic attributes, and landscape metrics is vital for forest ecological service evaluations and suitable management in sprawling urban areas with increasing road networks. We chose Harbin, a fast growing provincial capital city in northeast China, as a case study to address this issue. We utilized ArcGIS software (Esri, version 10.0; Redlands, CA, USA) and FRAGSTATS (V4.2.589) to digitize GF-1 images (Gaofen No.1 remote sensing images) to acquire road net characteristic information and landscape metrics of urban forests in Harbin. Together with forest structural-taxonomic attributes from a stratified random sampling survey, statistical methods such as an analysis of variance, a regression analysis, and a redundancy analysis were used to determine the road-dependent differences and to decouple the associations between them. The results indicated that road area percentages, road length/imperious surface area (ISA) ratios, road area/ISA ratios, and road cross-points sharply increased from low to heavy RD areas. This road intensification was strongly associated with increased urban forest area, patch density, and diverse patch shapes; smaller tree sizes, lower tree densities, and diverse tree species compositions were generally observed. Redundancy-based variation partitioning showed that part of the variations in structural-taxonomic attributes of forests could be explained by road intensity characteristics. In low RD (0–1.5 km/km2) regions, the road characteristics significantly affected forest characteristics (Shannon Wiener diversity index, species richness, and evenness index); however, such associations weakened with increasing forest landscape-related associations in medium to heavy RD (1.5–6 km/km2) regions. Our findings highlighted that road development is strongly associated with forest characteristics in Harbin city, and RD-dependent forest landscape regulating management could favor the maximization of forest ecological services that are related to structural and species identities.

Study of the Spatiotemporal Variation Characteristics of Forest Landscape Patterns in Shanghai from 2004 to 2014 Based on Multisource Remote Sensing Data

The landscape patterns of urban forests not only reflect the influence of urbanization on urban forests, but also determines its function in urban ecosystem services. In the case of mastering the overall forest landscape pattern of a city, a study of the structure of urban forest landscapes at different scales and in urbanized regions is beneficial to a comprehensive understanding of the forest characteristics of a city. In the present study, an attempt was made to map and monitor the spatio-temporal dynamics of an urban forest in Shanghai from 2004 to 2014 using remote sensing techniques. Methods of landscape ecology analysis are followed to quantify the spatiotemporal patterns of an urban forest landscape by urban and rural gradient regionalization. The results show that the spatial structure of an urban forest landscape is essentially consistent with an urban landscape pattern. Due to strong interference from human activities, the ecological quality of forest landscapes is low. At the landscape level, the urban forest coverage rate increased from 11.43% in 2004 to 16.02% in 2014, however, the number of large patches decreased, there was a high degree of urban forest landscape fragmentation, landscape connectivity was poor, landscape patch boundaries were uniform, and weak links were present between ecological processes. Different urban and rural gradient division methods exhibit obvious gradient characteristics along the urban–rural gradient in Shanghai. The regional differences in the urban forest landscape ecological characteristics have further increased as a result of urban planning and zoning. The total amount of urban forest is located closer to the urban center, which has the smallest total amount of forest; however, in terms of urban forest coverage, the suburbs have more coverage than do the outer suburbs and the central urban areas. The urban forest landscape’s spatial distribution area is evidently different. Urbanization affects the areas closest to urban residential areas, which are markedly disturbed by humans, and the urban forest landscape has a high degree of fragmentation. The forest patches have become divided and unconnected, and the degree of natural connectivity has gradually decreased over the past 10 years. At the landscape class level, broadleaf forests are dominant in Shanghai, and their area exhibits an increasing trend; shrublands and needleleaf forests, however, show a decreasing trend. Compared with other forest types, the spatial distribution of broadleaf forest is concentrated in the suburbs, and the aggregation effect is relatively apparent. From the perspective of urban forest landscape pattern aggregation characteristics in Shanghai, the spatial distribution of urban forest landscape point patterns in the study area exhibit extremely uneven characteristics. The point density of urban forest patches larger than 1 ha in Shanghai increased from 2004 to 2014. However, the total number of patches with areas larger than 5 ha decreased, and this decrease plays an important role in the ecological environment. In the past 10 years, the concentration characteristics of urban forests with large patches has gradually decreased. In 2014, the urban forest landscapes decreased by 5 km compared to the intensity of aggregates in 2004, which also indicates that urban forests in Shanghai tend to be fragmented. The results of this study can be useful to help improve urban residents’ living environments and the sustainable development of the urban ecosystem, and they will also be vital to future management.

Association of urban forest landscape characteristics with biomass and soil carbon stocks in Harbin City, Northeastern China

BackgroundUrban forests help in mitigating carbon emissions; however, their associations with landscape patterns are unclear. Understanding the associations would help us to evaluate urban forest ecological services and favor urban forest management via landscape regulations. We used Harbin, capital city of the northernmost province in China, as an example and hypothesized that the urban forests had different landscape metrics among different forest types, administrative districts, and urban–rural gradients, and these differences were closely associated with forest carbon sequestration in the biomass and soils.MethodsWe extracted the urban forest tree coverage area on the basis of 2 GF-1 remote sensing images and object-oriented based classification method. The analysis of forest landscape patterns and estimation of carbon storage were based on tree coverage data and 199 plots. We also examined the relationships between forest landscape metrics and carbon storage on the basis of forest types, administrative districts, ring roads, and history of urban settlements by using statistical methods.ResultsThe small patches covering an area of less than 0.5 ha accounted for 72.6% of all patches (average patch size, 0.31 ha). The mean patch size (AREA_MN) and largest patch index (LPI) were the highest in the landscape and relaxation forest and Songbei District. The landscape shape index (LSI) and number of patches linearly decreased along rural-urban gradients (p < 0.05). The tree biomass carbon storage varied from less than 10 thousand tons in the urban center (first ring road region and 100-year regions) to more than 100 thousand tons in the rural regions (fourth ring road and newly urbanized regions). In the same urban–rural gradients, soil carbon storage varied from less than five thousand tons in the urban centers to 73–103 thousand tons in the rural regions. The association analysis indicated that the total forest area was the key factor that regulates total carbon storage in trees and soils. However, in the case of carbon density (ton ha−1), AREA_MN was strongly associated with tree biomass carbon, and soil carbon density was negatively related to LSI (p < 0.01) and AREA_MN (p < 0.05), but positively related to LPI (p < 0.05).DiscussionThe urban forests were more fragmented in Harbin than in other provincial cities in Northeastern China, as shown by the smaller patch size, more complex patch shape, and larger patch density. The decrease in LSI along the rural-urban gradients may contribute to the forest carbon sequestrations in downtown regions, particularly underground soil carbon accumulation, and the increasing patch size may benefit tree carbon sequestration. Our findings help us to understand how forest landscape metrics are associated with carbon storage function. These findings related to urban forest design may maximize forest carbon sequestration services and facilitate in precisely estimating the forest carbon sink.

The Concept of Landscape Structure, Forest Continuum and Connectivity as a Support in Urban Forest Management and Landscape Planning

Close-to-nature urban forests and remnants of natural vegetation represent an important opportunity for urban residents to experience daily perception of and access to the natural environment. Despite there being a high percentage of forest cover (59%) and a favorable structure of the prevailing forested landscapes in Slovenia, urban expansion and infrastructure-driven development has severely weakened the connectivity and conservation of urban and suburban forests. The majority of urban settlements lie within walking distance of the surrounding forests (&lt;1 km). However, only close-to-nature forests with relatively low silvicultural inputs offer ecosystem services sufficient to fulfil the supply and demand of the expanding urban population. In order to estimate the conservation of forests in the open space of Slovenian settlements, we used a spatial model of landscape structure and forest connectivity. The model can be enhanced with patterns of corridors and stepping stones of natural vegetation in the landscape matrix to provide support in the decision-making process of landscape planning and the conservation of urban and suburban forests.

Understanding treescape changes as the basis of urban forest planning in fringe areas

We selected the Mapo-Niulanshan township located in the urban fringe of the Beijing metropolis as a case study with the goals of understanding urban forest change dynamics and locating potential spaces for conserving and developing urban forests, in the context of land use change associated with rapid urbanization. The results revealed an increase in canopy cover and forestland with the urbanization process. There was a significant increase in canopy cover in highly developed areas due to rising landscape needs and regulatory demands. The majority of forestland was converted from farmland and consisted of tree nurseries that usually lacked a recognizable canopy cover in remote sensing images. The influence of population density (POP) was strongest, followed by those of the built-up area ratio (BCOV) and gross industrial production (GIP). These socioeconomic factors had varying effects on the spatial heterogeneity of the urban forest landscape. Most of the areas demonstrated a positive influence of socioeconomic factors on urban forest landscape, especially those adjacent to water bodies and forestland. Based on the R2 values of the geographically weighted regression (GWR) models, unquantifiable indicators, such as policies and public preferences, were deemed very important in shaping urban forest landscape. According to the minimum cumulative resistance model (MCRM), suitable land for the development of urban forest mainly concentrated in the peripheral regions. Our research confirms that canopy cover must be considered with forestland area in spatial pattern analysis of the urban forest landscape. The results of the socioeconomic influence analysis and the MCRM helps to advance the understanding of urban forestry conservation and could improve policy-making and practices that promote urban forest under the pressure of urbanization.

Bryophytes as bioindicators of the atmospheric environment in urban-forest landscapes

Bryophytes have been used as indicators to evaluate atmospheric conditions in urban areas. However, further research is needed for their effective application. In this study, we focused on four metrics related to atmospheric problems in urban areas (nitrogen concentration [% N], isotope ratio of nitrogen [δ15N], index of atmospheric purity [IAP], and richness of hygrophilic life-forms [RHL]). Then, using linear and generalized linear models, we examined the influence of land use on these four metrics in urban atmospheric environments, and evaluated the usefulness and limitation of them. The % N and δ15N models were well explained by the influence of nitrogen sources and/or sinks. The RHL models were significantly affected by urban and forest areas, reflecting urban heat islands. Surprisingly, IAP was higher in urban areas, but comparisons of IAP are not informative in areas with narrow pollution gradients. Land use strongly affected % N and δ15N models in smaller areas because of a point-source influence of nitrogen pollution, whereas RHL was strongly influenced by land use at larger scales owing to drought stress in urban settings. Correlations among the metrics revealed that severe drought stress tended to occur in areas with high nitrogen pollution. The nitrogen pollution sources were diverse, with no significant correlation of δ15N values with % N.

Consensus in visual preferences: The effects of aesthetic quality and landscape types

Our research used pictures of four different landscapes to study the effects of two possible sources (visual aesthetic quality (VAQ) and landscape types) on the consensus of visual preferences among 156 undergraduate respondents. There were ten pictures each of urban, urban green space, farm, and forest landscapes presented for visual preference assessment. We found that VAQ assessment had a significantly positive linear relationship with judgment consensus when the four landscape types were combined. However, this relationship differed when examining one individual landscape type, it varied depending on the different landscape types. Thus landscape types had a significant influence on the consensus. Additionally, we found that consensus increased when a landscape was well maintained and had greater vegetation coverage.

Assessment of landscape silhouette value in urban forests based on structural diversity indices

Urban forests form an important component of the urban environment. They make a significant contribution to landscape silhouettes due to species diversity and the differences observed within forest communities such as tree composition, size and form. Visual effects such as these are referred as aesthetic value. Therein, quantitative assessments of targeted forest structures that will optimize aesthetic values are vital during urban forest planning. However, the silhouette effect, which is an important component of aesthetic value, has not been extensively studied to date. This study aims to reveal the relationship between forest structure, the visual quality of tree composition and the different forms and sizes that create the silhouette effect. To this end, virtual landscapes of different structures were created using computer-assisted images. The forest structure was characterized by a Form Mingling Index (FMI) and Height Dominance Index (HDI). A Pearson correlation was applied in order to find the relationship between the landscape silhouette values through a perceptual test as well as the FMI and HDI. The results of the analyses showed that there was a strong positive relationship between the FMI and HDI (r = 0.78, r = 0.75, P < 0.01, respectively) and landscape silhouette values. The combined effect of FMI + HDI was found to have the highest relationship with landscape silhouette values (r = 0.80, P < 0.01). In conclusion, FMI and HDI offer a rapid, cost-effective method which can be used by managers to assess the silhouette value of an urban forest landscape.

Geographical modeling of spatial interaction between human activity and forest connectivity in an urban landscape of southeast China

Geographical detector models provide a quantitative approach for evaluating spatial correlations among ecological factors, population density and landscape connectivity. Here, we used a geographical model to assess the influence of different gradients of urbanization, human activities and various environmental factors on the connectivity of urban forest landscapes in Xiamen, China from 1996 to 2006. Our overarching hypothesis is that human activity has modified certain ecological factors in a way that has affected the connectivity of urban forest landscapes. Therefore, spatiotemporal distributions of landscape connectivity should be similar to those of ecological factors and can be represented quantitatively. Integral indices of connectivity and population density were employed to represent urban forest landscape connectivity and human activity, respectively. We then simulated the spatial relationship between forest patches and population density with Conefor 2.6 software. A geographical detector model was used to identify the dominant factors that affect urban forest landscape connectivity. The results showed that a distance of 600 m was the threshold of node importance. Mean annual temperature, mean annual precipitation, elevation, patch area, population density and dominant species had significant effects on the node importance. Mean annual temperature was more significant than population density in controlling the spatial pattern of the delta of the integral index of connectivity (dIIC). The spatial interaction between population density and various ecological factors as well as their linearly enhanced or nonlinearity enhanced urban forest landscape connectivity. In conclusion, a combination of graph theory and geographical detector models is effective for quantitatively evaluating interactive relationships among ecological factors, population density and landscape connectivity.

Analyzing the causal factors of carbon stores in a subtropical urban forest

Studies of forests and urban forest ecosystems have documented the various biophysical and socioeconomic correlates of carbon storage. Tree cover in particular is often used as a determinant of carbon storage for local and national level urban forest assessments. However, the relationships among variables describing the biophysical and socioeconomic environment and carbon are not simple statistical ones. Instead, there are complex interactions that can have either a unidirectional causal effects, or produce indirect effects through interactions with other ecosystem structure and landscape characteristics. Thus, understanding the direct and indirect effects of structure, composition, and landscape characteristics is key to quantifying ecosystem services. This study used field data from plots across an urban watershed, site-specific biomass equations, and structural equation modeling of urban forest structure and landscape variables to quantify the causal influences of tree cover, land use, stand density, species composition and diversity on carbon stores. Our path analysis shows that the effect of tree cover on carbon stores is not only direct but also indirect and influential through basal area and composition. Findings suggest that species composition, species diversity and land use have much more complex relationships than previously reported in the urban forest literature. The use of path analysis in these types of studies also presents a novel method to better analyze and quantify these direct and indirect effects on urban forest carbon stores. Findings have implications for urban forest ecosystem assessments that use tree cover as the sole metric for inferring ecosystem functions and services.

Factors explaining the occurrence of the Siberian flying squirrel in urban forest landscape

Urban forests are often modified and fragmented by human land use and the original habitat might exist only in remnant patches. Due to their specific habitat requirements and unwillingness to move through matrix many forest-dwelling mammals are susceptible to changes in landscape structure. It is important to understand how the availability of suitable habitat and landscape fragmentation affect species distributions, and what landscape characteristics are essential to the persistence of a given species to conserve urban wildlife. We investigated the effect of landscape composition and configuration on the occurrence of the Siberian flying squirrel, a small-sized arboreal rodent, in a partly urbanized area of Eastern Finland. All suitable and potential forest patches were searched to determine the presence or absence of species, and the landscape characteristics of occupied sites were compared to those of unoccupied sites. Flying squirrels occurred both at the edges of large suitable forested areas, but also in small forest fragments within residential areas. Surprisingly, urban areas did not have a negative effect on the flying squirrel occurrence. Occurrence probability was not either associated with the proportion of suitable habitat, but occupied sites contained larger amount of movement habitat and had shorter distances to nearest occupied sites than unoccupied sites. Our results show that flying squirrels can exist in urbanized landscape and near residential areas, but more detailed information on habitat use and survival is still needed to determine the long-term persistence and viability of the urban populations.

Developing an amenity value calculator for urban forest landscapes

The goal of this research is to develop a framework that can be used by landscape and urban planners to implement an “amenity value calculator” for urban forest landscapes across a metropolitan county. By balancing the pros and cons of using typical hedonic frameworks versus urban forest inventory and management software systems, we (1) construct a data-driven approach to estimate the total amenity value associated with access to, views of, and existence of a particular forest landscape from among all available forest sites in a community and (2) develop a framework for an amenity value calculator for numerous community forest landscapes within a metropolitan county, using the amenity values generated from objective (1), that can be accessed and understood by anyone who is interested in the benefits provided by nearby community forests. Our research suggests that (i) residential household’s amenity value per acre of forest landscape decreases asymptotically towards zero as the driving time from a residential house increases, (ii) an amenity value calculator can be developed to sum the amenity values across all detached single-family houses within a range of driving times from any selected forest landscape, and (iii) a user-friendly, web-based application, that allows users to view the estimated amenity values of forest landscapes that interest them, can be created to better inform the public about the values of forest landscapes of interest to them.

Physiological and psychological effects of viewing urban forest landscapes assessed by multiple measurements

The present study investigated the physiological and psychological effects of viewing urban forest landscapes on 48 young male urban residents. Four forested areas and four urban areas located in central and western Japan were used as the test sites. We found that in the forested areas, the subjects exhibited (i) significantly lower diastolic blood pressure, (ii) significantly higher parasympathetic nervous activity, but significantly lower sympathetic nervous activity, and (iii) significantly lower heart rate. The forest landscapes (iv) obtained better scores in subjective ratings, and (v) induced significantly less negative and more vigorous moods. Taken as whole, these findings suggest that even a short-term viewing of forests has relaxing effects. We have thus concluded that the approach taken in this study is useful in exploring the influences of urban green space on humans, as well as contributing to the planning and design of a healthy environment for urban residents.

Linking landscape patterns with ecological functions: A case study examining the interaction between landscape heterogeneity and carbon stock of urban forests in Xiamen, China

The relationship between landscape patterns and functions is the central research theme of landscape ecology and forest management. This study assesses the interactive relationship of landscape heterogeneity with the carbon stock of urban forests in the city of Xiamen, Fujian Province, China, using spatial and statistical analyses. The objectives of this study are to explore the most appropriate scale for studying urban landscape patterns in Xiamen, analyze the dynamics of forested landscape heterogeneity at different scales, and identify suitable landscape metrics that are closely related to and can be used to describe vegetation carbon density. This study is based on data from 31,933 plots measured during the years 1972, 1996, and 2006 and collected as part of the Chinese National Forest Resource Planning and Inventory Program. A total of 12 landscape metrics were used to quantify spatial patterns and were subsequently related to vegetation carbon density. The results show that the most appropriate scale for landscape pattern analysis is 80km2. With urbanization advancing between 1972 and 1996, landscape heterogeneity at both class and landscape levels showed a significant increase and then remained stable from 1996 to 2006. Shannon’s diversity index was the most sensitive landscape metric among all selected landscape heterogeneity metrics, and its ability to explain the variation of carbon density was better than that of forest types. This study clearly shows that information on spatial patterns of landscape heterogeneity is important for urban forest landscape planning to achieve forest carbon objective.

Studi Kenyamanan untuk Aktivitas di Lanskap Hutan Kota UGM Studi Kasus: Klaster Agro UGM

A Study of Comfort for Activities in Urban Forest Landscape of UGM; Study Case: Agro Cluster UGMThe phenomenon of global warming has caused discomfort activity in urban area. Greening in open space of Gadjah Mada University campus has been developed as urban forest landscape that supporting good environment produced high comfort for activity and enhancing urban conservation. The research objectives were to observe the comfort for activity in urban forest landscape, to observe the canopy coverage of urban forest and to reveal the effect of tree canopy coverage to the comfort for activity. Data collection was carried out by visual observation, questioner, micro climate measurement, and hemispherical images of the tree canopy coverage. Data were analyzed by descriptive statistics. The tree canopy coverage was calculated by the Sky View Factor (SVF) of hemispherical images. Research results showed that activity types in the urban forest landscape were study (10%), sitting (37%), meeting (39%), others (14%) at spread of sitting areas. Some factors that affect the comfort for activity in urban forest landscape were aesthetic, lower temperature, fresh air, inspirited area, and listened bird voice. The respondents (82%) said that the urban forest landscape was comfort for activity at whole time of 07.00 - 17.00 by the condition of local climate presented by air temperature at 29.7 - 32.6°C, normal humidity at 61.5 -74.1% and breeze wind velocity at 0.6 - 2.8 m/s. Tree canopy of urban forest landscape had covered more than 50% identified by Sky View Factor (SVF 0.026-0.446). The tree canopy coverage of urban forest created tree shaded areas for the activities which showed thermally comfort because of microclimate controlled by urban forest.

Dry deposition velocity of total suspended particles and meteorological influence in four locations in Guangzhou, China

AbstractDry deposition velocity of total suspended particles (TSP) is an effective parameter that describes the speed of atmospheric particulate matter deposit to the natural surface. It is also an important indicator to the capacity of atmosphere self-depuration. However, the spatial and temporal variations in dry deposition velocity of TSP at different urban landscapes and the relationship between dry deposition velocity and the meteorological parameters are subject to large uncertainties. We concurrently investigated this relationship at four different landscapes of Guangzhou, from October to December of 2009. The result of the average dry deposition velocity is (1.49 ± 0.77), (1.44 ± 0.77), (1.13 ± 0.53) and (1.82 ± 0.82) cm/sec for urban commercial landscape, urban forest landscape, urban residential landscape and country landscape, respectively. This spatial variation can be explained by the difference of both particle size composition of TSP and meteorological parameters of sampling sites. Dry deposition velocity of TSP has a positive correlation with wind speed, and a negative correlation with temperature and relative humidity. Wind speed is the strongest factor that affects the magnitude of TSP dry deposition velocity, and the temperature is another considerable strong meteorological factor. We also find out that the relative humidity brings less impact, especially during the dry season. It is thus implied that the current global warming and urban heat island effect may lead to correlative changes in TSP dry deposition velocity, especially in the urban areas.

Urban forest landscape patterns in Ma'anshan City, China

The landscape pattern of Ma'anshan City was analyzed based on theories and methodologies of landscape ecology, remote sensing, global positioning, and a geographic information system (GIS). The study area encompassed the entire built-up area of 63.88 km2; a north–south transect 3-km wide and 13-km long was established along the long axis of the city. Five major landscape elements were assessed: urban land, urban forest, agriculture, water, and grass. Urban land was the dominant land cover type, and occupied 67% of total land area; while patches of urban forest occupied 16%, with a landscape element dominance of 0.42. Urban forest was classified according to land-use category and location into six types: scenic forest, yard forest, recreational forest, roadside forest, shelter forest, and nurseries. There were 2464 urban forest patches, the largest being 185.1 ha, with an average of 0.43 ha. The low nearest neighbor index and high patch density indicated that urban forest patches tend to be aggregated and have a high degree of fragmentation. This study also demonstrated that the spatial pattern of urbanization could be quantified using a combination of landscape metrics and gradient analysis. Urban forest has distinct spatial characters that are dependent on specific landscape metrics along the urbanization gradient.

Consumer-Grade Global Positioning Systems Performance in an Urban Forest Setting

Abstract Consumer-grade global positioning system (GPS) receivers are available for several hundred dollars or less and can be used for urban forestry measurement applications provided that acceptable accuracies are achieved. Potential applications include locating and mapping trees, arbor facilities, and urban infrastructure. We examined the measurement accuracy and reliability of six identical contemporary consumer-grade GPS receivers that collected data simultaneously at two distinct test courses. One test course was located in an open field and the other test course simulated an urban forest landscape with partial tree canopy cover and several buildings blocking a view of the horizon. We also varied data collection techniques by using 1, 10, and 30 point averages to examine the influence of different point averages on measurement accuracy and precision. Measurement accuracies for all GPS receivers averaged 1.8 m from true position at the open field course and 3.8 m from true position at the urban forest course with variations depending on when the courses were visited. We also found that although six identical receivers were used to collect measurements simultaneously and in close proximity to one another, there were statistically significant differences in the measurement accuracies of the receivers. However, no statistically significant influence of different point averaging (1, 10, and 30) on measurement accuracy was detected.

Current situation and development of Chinese urban forestry

This paper introduces Chinese urban forestry research in terms of the concept, forest types, ecosystem services, spatial structure, planning and construction, assessment and management. Modern Chinese urban forest had a close relationship with traditional landscape architecture. Urban forest services had been quantified in some case cities, and determined by urban forest spatial patterns and internal structures. Based on landscape ecology and urban planning, urban forest spatial patterns have been analysed and planned rationally in some cities. However, studies on urban forestry generally lack long-term, continuous and systemic observations, as well as in-depth research on ecological processes and mechanisms. The development trends in urban forestry in China might include extensive application of '3S' technology, research on the relationship between urban forest landscape spatial patterns and their ecological effects, economic assessment, ecological and economic benefits and studies on the negative effects of pollutants.

Channel morphology and sediment origin in streams draining the Georgia Piedmont

Summary Urbanization is common across much of the US However, the Southeast, including the Georgia Piedmont, is developing much faster than other regions ( USDA, NRCS, 2004 ). Consequently, water resources in the Middle Chattahoochee Watershed of western Georgia are threatened by increased sedimentation from extensive urban development as well as from other land covers such as livestock grazing and silviculture. A 2-yr study was developed to assess sediment transport and origin across 16 watersheds draining urban, developing, pastoral, managed forest and unmanaged forest landscapes. Total suspended solids (TSS) and total dissolved solids (TDS) yields and sediment rating curves were measured concomitantly with channel morphometry measurements in each stream. Urban streams featured the lowest baseflow concentrations, but sediment concentrations rose rapidly during stormflow in urban streams. Detailed cross-sections assessed channel stability and showed that pasture streams were the most unstable streams during stormflows. Finally, sediment source tracking was performed in a subset of intermittent streams using amorphous to crystalline ratios of iron to estimate the fraction of sediment coming from instream vs. landscape sources. Artificial stormflows were generated to mobilize bed sediment for the development of an instream sediment signature. If these ratios differed during natural events, it was inferred the differences were due to sediments mobilized from the terrestrial landscape. Results indicated that higher ratios of amorphous:crystalline Fe occurred during artificial floods (urban = 0.60 and unmanaged forest = 0.14) than natural stormflows (urban = 0.08 and unmanaged forest = 0.03) in watersheds dominated by urban and unmanaged forest land cover, suggesting that crystalline (i.e., terrestrial) sources of Fe were transported to the stream during rainfall events.