潭江流域森林碳储量及其动态变化

根据森林碳储量的计算方法和森林资源清查资料,结合实地调查校正,估算了11年来快速城市化过程中潭江流域森林的碳储量及其动态变化,分析了人口密度、GDP增长与森林的碳储量、碳密度的相关关系.结果表明,潭江流域森林碳储量由1990年的5.906×10⁶t增长到2001年的7.852×10⁶t,年均增长0.18×10⁶ t,增长率为3.05%,起到了碳汇的作用.人口密度的增加和经济的快速发展没有影响到森林碳储量和碳密度的增加,但林业发展速度远落后于经济发展的速度.合理的林业管理模式与经济发展相互协调是流域森林生态系统在城市化过程中提供更好的服务功能并促使区域生态环境可持续发展的关键.     

深圳市龙华地区快速城市化过程中的景观结构研究--城市建设用地结构及异质性特征分析

利用多时段景观遥感制图信息和景观格局研究方法 ,对深圳市龙华地区快速城市化过程中城镇建成区和新开发区两种建设用地类型的结构和空间分布特征进行了研究 .结果表明 ,两种类型研究期间斑块数量、平均面积大幅度增加 ,碎裂化程度不断降低 ;建成区增长主要有大型居民点持续扩张和独立小斑块不断产生两种模式 ,开发区建设的高峰时期是 1990～ 1994年 ;受地形和交通等因素的影响 ,建成区一直表现出显著宏观异质性分布特征 ,但孔隙度水平不断降低 ,中小尺度的分布差异仍然比较明显 ;新开发区受与建成区相同的约束条件限制 ,同样表现为宏观异质性特征 ,空间不均匀分布的表现尺度大于建成区 .工作区内因城建用地快速膨胀引起的各种生态问题急需通过土利用政策的调整加以解决 .     

Modeling the ecological niche of long-term land use changes: The role of biophysical factors

Land use/land cover changes (LULCCs) represent the result of the complex interaction between biophysical factors and human activity, acting over a wide range of temporal and spatial scales. The aim of this work is to quantify the role of biophysical factors in constraining the trajectories of land abandonment and urbanization in the last 50 years. A habitat suitability model borrowed from animal ecology was used to analyze the ecological niche of the following LULCC trajectories occurred in Emilia-Romagna (northern Italy) during 1954–2008: (i) land abandonment (LA) and (ii) urbanization (URB), both from agricultural areas (URB_agr) and from semi-natural areas (URB_for). Results showed that the different LULCC trajectories were driven by different combinations of biophysical factors, such as climate, topography and soil quality. In particular, slope and elevation resulted as the main driving factors for rural processes, while slope and temperatures resulted as the main constraints underlying urban processes. This approach may represent a conceptual and technical step toward the systematic assessment of LULCC processes, thus providing an effective support tool to inform decision makers about land use transformations, their underlying causes, as well as their possible implications.     

The influence of rapid urbanization and land use changes on terrestrial carbon sources/sinks in Guangzhou,China

Complex changes in carbon sources and sinks caused by rapid urbanization have been observed with extensive changes in the quantity, structure, and spatial pattern of land use types. Based on the modified Carnegie-Ames-Stanford Approach model and on gray relational analysis, we analyzed the influence of land use changes on carbon sinks and emissions in Guangzhou from 2000 to 2012. The aim was to identify suitable options for built-up land expansion that would allow for minimal carbon losses. The key results were as follows: (1) Built-up land increased by 118.91% in Guangzhou city over the study period, with this expansion taking the form of concentric circles extending around the old Yuexiu district. (2) Carbon emissions over the period of analysis significantly exceeded carbon sink capabilities. The total carbon sink decreased by 30.02%, from 535.40 × 10³ t to 374.6 × 10³ t. Total carbon emissions increased by 1.89 times, from 13.73 × 10⁶ t to 39.67 × 10⁶ t; 80% of carbon emissions were derived from energy consumption. (3) There were large differences in the extent of carbon sink losses at different scales of built-up land expansion and land use change. In Guangzhou, the loss of carbon sink is small when cultivated land (though not prime farmland) and water bodies are converted to built-up land on a small scale. The loss of carbon sink is much smaller when grasslands are converted to built-up land on a large scale. However, forested land, which has excellent carbon sink functions, should not be converted. (4) Changes in carbon sinks were mainly affected by natural factors and land urbanization. Changes in carbon emissions were mainly affected by population urbanization, economic urbanization, and land urbanization. (5) To achieve “economical and intensive use of land”, “urban growth boundary” and “ecological red lines” should be determined for government policies on land use management. These factors have great significance for “increasing carbon sinks and reducing carbon emissions” in urban ecological systems.     

Quantifying urban ecological governance: A suite of indices characterizes the ecological planning implications of rapid coastal urbanization

Urban ecosystems in China have undergone a surge of rapid urbanization leading to phenomenal socio-ecological transformation. To mitigate the regional ecological and environmental impacts, cross-scale ecological governance has not been well established. This paper aims to propose an assessment framework to examine and understand urban ecological governance (UEG), a concept that intertwines multiple aspects such as governance, planning, and urban ecology into an integrated procedure for policy formulation and implementation. To test the assessment framework and thereby derive a quantitative approach to studying socio-ecological couplings within the urban systems, we choose Lianyungang, a rapid urbanizing coastal city in China for an empirical study. We ascertain each subsystem (e.g., urbanization, ecological, governance) presents a fluctuating trend particularly after 2005. Also, the overall trends of UEG increased slightly during the two study periods (1997–2012 and 2005–2012), mainly due to the influences of the Urban Master Plan and Eastern Coastal Regional Development Strategic Planning of Lianyungang. These results imply that the UEG in China’s local governments is unique, and the planning system especially acts a core player to cope with increasing regional ecological risks and uncertainties. It is suggested that China’s UEG needs to enhance experimental governance, ecological redline policy (ERP) and multi-plan integration and combine its current government-dominant top-down system with Western bottom-up decision-making mechanisms.     

δ15N of estuarine fishes as a quantitative indicator of urbanization

Nitrogen stable isotope values (δ¹⁵N) have commonly been used as a qualitative indicator of catchment urbanization in estuaries, but no quantitative relationship has to date been established between δ¹⁵N and degree of urbanization. We sampled five species of common estuarine fish (Mugil cephalus, Acanthopagrus australis, Sillago ciliata, Gerres subfasciatus and Herklotsichthys castelnaui) of different trophic levels from six estuaries in Southeast Queensland, Australia, to test if a quantitative relationship exists between fish δ¹⁵N and urbanization in the catchment. Degree of urbanization (urban %) in the catchment adjacent to the tidal estuary was measured using polygons constructed in Google Earth images, and verified using data from the detailed Queensland Land Use Mapping Project (QLUMP). Significant linear relationships exist between fish δ¹⁵N and urban % in most cases irrespective of the section of the estuary (upper, middle and lower) where the fish were caught, with no difference in slope and elevation between lines established for different sections. Inclusion of additional fish δ¹⁵N data from other Australian estuaries in a combined multiple regression model adding trophic level as a predictor generated a significant relationship predicting increase in fish δ¹⁵N values with increasing urban % and trophic level. There is therefore a generic quantitative relationship between estuarine fish δ¹⁵N values and degree of urbanization applicable to different fish species, geographic location or feeding habit. While the generality of this relationship needs to be tested further in other geographic locations, our findings potentially improve the applicability of fish δ¹⁵N values as a quantitative indicator of urban influence in estuaries.     

Comparing urbanization patterns in Guangzhou of China and Phoenix of the USA: The influences of roads and rivers

Examining the similarities and differences in urbanization pattern between cities in developed and developing countries may enhance our understanding of urbanization processes and mechanisms. Using a buffer analysis approach, we compared the long-term spatiotemporal patterns of urbanization between Guangzhou of China and Phoenix of the United States during the 20th century, with a particular emphasis on the impacts of major roads and rivers. The development of Guangzhou was relatively compact, whereas the development of Phoenix was much more dispersed. The two metropolitan areas were characterized mainly by two types of urban expansion processes. Guangzhou experienced a diffusion–coalescence–diffusion–coalescence process while Phoenix experienced a diffusion–coalescence process. The buffer analysis indicated that the impacts of roads and rivers on the urbanization of Guangzhou and Phoenix were similar in terms of urban area, the number of urban patches, the mean patch size, but different in terms of the complexity of urban patches. The urban area declined with increasing distances to roads, but it increased when the distance was close to the rivers and then declined with the increment of distances to rivers. In general, the impacts of roads are stronger in Phoenix than in Guangzhou, while the impacts of rivers are greater in Guangzhou than in Phoenix. These similarities and differences between the two metropolitan regions are reflective of those in both physical conditions and land use policies in the two countries. By comparing these similarities and differences, we can improve our understanding of the urbanization processes in both developed and developing countries, which is necessary for achieving global urban sustainability.     

Responses of wasp communities to urbanization: effects on community resilience and species diversity

Urbanization is one of the most extreme and rapidly growing anthropogenic pressures on the natural world. It is linked to significant impacts on biodiversity and disruptions to ecological processes in remnant vegetation. We investigated the richness and abundance of wasps in a highly fragmented urban landscape in Sydney, Australia, comparing assemblages in small urban remnants to edges and interiors of continuous areas of vegetation. We detected no difference in wasp abundance or species richness between remnant types indicating that communities are highly resilient to the effects of urbanization at this scale. However, Chao 2 estimates of predicted species richness indicate that edge sites would support a greater richness and abundance of species compared to small and interior sites. Although families were represented evenly across the sites, interior and edge sites supported more species within families. Wasp composition was significantly affected by the temporal variation and trap location (arboreal or ground), particularly at the family level demonstrating high species turnover and discrimination in vertical space. These sampling effects and temporal inconsistencies highlight the hazards of relying on one-off snapshot surveys and uncorrected datasets for assessments of diversity and responses to urban landscapes. The strong resilience of wasp communities to urbanization when assessed at coarse scales indicates that responses at finer spatial and taxonomic scales are critical to understanding the maintenance of ecosystem function in highly modified landscapes.     

Sources of reactive nitrogen affecting ecosystems in Latin America and the Caribbean: current trends and future perspectives

While the amount of reactive nitrogen circulating at the global level has increased markedly in the last century, the effects of this increase are largely seen at the regional level due to interacting ecological and socio-economic factors. In contrast with most other regions of the world, Latin America and the Caribbean (LA-Ca) stand out due to the fact that the major input of reactive nitrogen (Nr) still occurs naturally via biological nitrogen fixation (BNF) in natural ecosystems as opposed to anthropogenic inputs of synthetic fertilizer, fossil fuel combustion and cropping with leguminous species. Largely due to economic reasons, the consumption of fertilizer N in the LA-Ca region is still low in comparison with the average consumption of the world. However, the fertilizer N consumption is increasing at a much faster rate than that in developed regions of the world, like USA and Canada. The Nr production through BNF in cultivated plants that fix nitrogen (C-BNF) is 5 times lower than that occurring naturally in Latin America, but is still equivalent to 16% of the world C-BNF. The cultivation of nitrogen-fixing crop species in the LA-Ca region is also increasing, almost entirely due to the expansion of soybean fields in the central and northern regions of Brazil and the Pampa region of Argentina. Other anthropogenic activities in the region that contribute to an increase in the circulation of reactive nitrogen include the impact of biomass burning and urbanization. In the last decade, an average of 47,000 km² per year of forests was burned in the LA-Ca region. The environmental impact of urban centers in the LA-Ca region has become very important, since an intense urbanization process is occurring in this region, at an intensity that far exceeds urban development in the northern hemisphere. The consequences of increased urbanization include increased emissions of NO _x to the atmosphere due to the fossil fuel combustion, and the lack of sewage treatment facilities in most cities of the LA-Ca result in a large volume of untreated sewage discharged into surface waters, creating serious environmental problems. The combination of rapid urbanization and agricultural intensification in this region suggest that concern is warranted for the potential for increase in the circulation of reactive nitrogen in the very near future. At the same time, the opportunity still exists to mitigate some of the consequences of human impact on the nitrogen cycle in a region that still maintains a large fraction of its natural ecosystems intact.