Liangjun Da

Biodiversity changes in the lakes of the Central Yangtze

The Central Yangtze ecoregion in China includes a number of lakes, but these have been greatly affected by human activities over the past several decades, resulting in severe loss of biodiversity. In this paper, we document the present distribution of the major lakes and the changes in size that have taken place over the past 50 years, using remote sensing data and historical observations of land cover in the region. We also provide an overview of the changes in species richness, community composition, population size and age structure, and individual body size of aquatic plants, fishes, and waterfowl in these lakes. The overall species richness of aquatic plants found in eight major lakes has decreased substantially during the study period. Community composition has also been greatly altered, as have population size and age and individual body size in some species. These changes are largely attributed to the integrated effects of lake degradation, the construction of large hydroelectric dams, the establishment of nature reserves, and lake restoration practices.

Temporal and spatial characteristics of the urban heat island during rapid urbanization in Shanghai, China

Based on meteorological data from 1978 to 2007, we investigated the annual, seasonal, and fixed hourly variations of Shanghai urban heat island (UHI) in urban and suburban areas and spatial distribution of UHI. The results demonstrated a remarkable interannual increase of UHI intensity in Shanghai. The UHI was the strongest in autumn and the weakest in summer, as a consequence of the prevailing weather conditions. Similar to previous studies of other cities, the UHI in Shanghai was stronger in the nighttime than in the daytime. The SW–NE cross section followed the general cross section of the typical UHI described by Oke (1987) who defines its characteristic parts as “cliff”, “plateau”, and “peak”. Analysis of the association of UHI and urbanization indicated that the UHI increased with the expansion of population and rapid increase of gross domestic product. The continuous increase of power consumption and area of paved road and decrease of area of cropland caused the growth of UHI intensity. Green land had a positive effect on mitigation of heat island based on an inversed U-shaped curve with UHI intensity.

The biomass and aboveground net primary productivity of Schima superba–Castanopsis carlesii forests in east China

The biomass and productivity of Schima superba-Castanopsis carlesii forests in Tiantong, Zhejiang Province, were determined using overlapping quadrants and stem analyses. The total community biomass was (225.3±30.1) t hm−2, of which the aboveground parts accounted for 72.0% and the underground parts accounted for 28.0%. About 87.2% of biomass existed in the tree layer. The resprouting biomass was small, of which over 95.0% occurred in the shrub layer. The productivity of the aboveground parts of the community was (386.8±98.9) g m−2a−1, in which more than 96.0% was present at the tree level. The trunk’s contribution to productivity was the greatest, while that of leaves was the smallest. In China, the community biomass of subtropical evergreen broadleaved forests differs significantly with the age of the forest. The community biomass of the 52-year-old S. superba-C. carlesii forests in this study was lower than the average biomass of subtropical evergreen broadleaved forests in China, and was lower than the biomass of other subtropical evergreen broadleaved forests elsewhere in the world. Moreover, its productivity was lower than the model estimate, indicating that without disturbance, this community has great developmental potential in terms of community biomass and productivity.

Variations in air quality during rapid urbanization in Shanghai, China

Shanghai is the largest commercial and industrial city of China, but air quality issues have hindered its development in becoming a “global city.” This study used monitoring data on SO2, NOx, acid rain pH, dustfall, and total suspended particles (TSP) from the Shanghai Environmental Monitoring Center to evaluate and analyze the air quality in urban, suburban, and rural areas during the period 1983–2005. The results showed that the spatial pattern of air parameters was determined by the level of urbanization; thus, the higher the level of urbanization, the worse the air quality. On the whole, the atmospheric environment of the three spatial regions improved gradually because of economical growth and environmental protection since the 1990s. For the entire region of Shanghai, the relationship between the integrated air quality index and gross domestic product (GDP) per capita was an N-shaped environmental Kuznets curve (EKC) due to decreasing air quality in suburban and rural areas this century. Thus, environmental controls should be increased in Shanghai, especially in developing suburban and rural areas during rapid urbanization.

Dynamics of ruderal species diversity under the rapid urbanization over the past half century in Harbin, Northeast China

Urbanization has resulted in obvious changes in plant species diversity. We analyzed the dynamics of ruderal species diversity in Harbin over the past half century using historical data collected in 1955 and data of the present spatial distribution in 2010–2011. The results show that, the number of ruderal species decreased from 611 to 175 with remarkable tendency of decreasing in perennial species and increasing in winter annual species in the past half century, which caused the shift of life form spectrum from perennial mono-dominant type to summer annual and perennial co-dominant type. Meanwhile, the proportion of tropical originated species increased and the proportion of temperate originated species decreased which were considered to relate with the increase of temperature in urban area during the past half century. Moreover, there was a distinct decrease of the proportion of aquatic and hygrophytic ruderal species while an increase of mesic and xeric ruderal species which suggested a drought trend in urban habitats that consistent with the change of land use characterized as decrease of natural water bodies and wetlands and increase of urban land. Comparison of ruderal species along urbanization gradient also got the similar results with the above results from analysis on temporal scales and confirmed the effect of urbanization on decreasing plant richness. Our results suggested that land use change combined with its effect on temperature and disturbance regimes in urban habitats preferred species with short life span, high drought tolerance, fast growth rates and high seed yields.

The spatio-temporal pattern of historical disturbances of an evergreen broadleaved forest in East China: a dendroecological analysis

Evergreen broadleaved forests (EBLF), the zonal forest ecosystem of the subtropical zone in east China, have been degraded from recent anthropogenic disturbance. Understanding the role of past disturbances in EBLFs would be helpful to the restoration of degraded EBLFs. We used dendroecological techniques to reconstruct the disturbance history of a secondary EBLF dominated by Schima superba and Castanopsis carlesii in Tiantong National Forest Park (29°48′N, 121°47′E), Zhejiang Province, East China. The disturbances were inferred from tree-ring growth release and long-term establishment patterns obtained from 91 overstory trees. The initial growth rates of these trees were compared to trees originating in the understory to evaluate the intensity of past disturbances. The spatial distribution patterns of disturbances were portrayed with tree mapping. The results revealed that there were five disturbances, averaging one disturbance per decade over the past half century. The first disturbance event was probably most intense given that most canopy trees established at that time and displayed high initial growth rates. The timing of the second disturbance event coincided with the documented selective logging. The last three disturbances, having lower tree growth responses and a clumped spatial distribution of gap creation, were probably the result of recurring typhoons. The first two disturbances led to tree regeneration and secondary succession, represented mainly by long-lived deciduous trees in the forest. The subsequent disturbances facilitated the stand development process, creating a complex three-dimensional structure from a pre-existing single-age cohort. This study suggests that EBLFs affected by large disturbances can recover in a few decades and the frequent gap disturbances probably facilitate its process in the early successional stages.

The spatial-temporal pattern and influencing factors of negative air ions in urban forests, Shanghai, China

Negative air ions are natural components of the air we breathe. Forests are the main continuous natural source of negative air ions (NAI). The spatio-temporal patterns of negative air ions were explored in Shanghai, based on monthly monitoring in 15 parks from March 2009 to February 2010. In each park, sampling sites were selected in forests and open spaces. The annual variation in negative air ion concentrations (NAIC) showed peak values from June to October and minimum values from December to January. NAIC were highest in summer and autumn, intermediate in spring, and lowest in winter. During spring and summer, NAIC in open spaces were significantly higher in rural areas than those in suburban areas. However, there were no significant differences in NAIC at forest sites among seasons. For open spaces, total suspended particles (TSP) were the dominant determining factor of NAIC in summer, and air temperature and air humidity were the dominant determining factors of NAIC in spring, which were tightly correlated with Shanghai’s ongoing urbanization and its impacts on the environment. It is suggested that urbanization could induce variation in NAIC along the urban-rural gradient, but that may not change the temporal variation pattern. Furthermore, the effects of urbanization on NAIC were limited in non-vegetated or less-vegetated sites, such as open spaces, but not in well-vegetated areas, such as urban forests. Therefore, we suggest that urban greening, especially urban forest, has significant resistance to the effect of urbanization on NAIC.

The Construction of Near-Natural Forests in the Urban Areas of Shanghai

Throughout the ages, China has had a high regard for afforestation and forest protection. Old growth forests, secondary forests, Fengshui forests (which can be good luck for forest owners, such as monastery or temple forests, cemetery forests, and forests around houses), all of various areas and patterns, are seen across the nation. While forests have been planted throughout the nation since 1950 to improve environmental quality, the pace of forest construction has accelerated since 1980. As a result, China is now among the top nations with the greatest area of human-made forests in the world. Because the history of human activities in China has been long and often violent, indigenous vegetation has been severely damaged. This has made forest construction and reconstruction difficult by decreasing the survival rate of these forests and prolonging the time it takes for their restoration and establishment. Although this situation has been partially caused by problems such as policies and lack of funding, the lack of proper theory to support operational methods that can guide forest construction projects has also created setbacks. At present, there are discrepancies and inconsistencies in theories and methods for informing the process of restoring and reconstructing urban forest ecosystems (Hobbs, 1996; Allen et al., 1997; Palmer et al., 1997; Miyawaki, 1998; Bao and Chen, 1999; Zhang and Xu, 1999). Empirical studies that scientifically experiment with various methods and test different theories are needed both to advance the discipline of urban forestry and to determine best management techniques and approaches in different urban contexts. The city is an artificial, constructed ecosystem where human occupation is dominant. Cities are complex ecosystems consisting of social, economic, and natural subsystems. The natural ecosystem within urban areas is in a precipitous state of decline due to intense human activities of long duration. The discipline of urban forestry, which arose in Western nations in the latter half of the 20th century, is a type of forestry that serves to improve the quality of human life in the city. Therefore, in its narrowest sense, the objective of urban afforestation is to make the city green, beautiful, and healthy for people. Near-natural forests is a new urban afforestation method developed and carried out by Miyawaki (1998, 1999a,b; see also Chapter 12). This recent restoration approach is based on the theories of potential natural vegetation and community succession. Native tree and shrub species are selected from the natural vegetation in a local area and their seeds germinated and

Structure and diversity of remnant natural evergreen broad-leaved forests at three sites affected by urbanization in Chongqing metropolis, Southwest China

Evergreen broad-leaved forests (EBLFs, lucidophyllous forests) are vegetation types characteristic of East Asia. The extent of EBLFs has decreased significantly due to long-term anthropogenic disturbance, and remnant EBLFs in urban area are rare and important landscape types contributing to biodiversity and sustainable development. This study focuses on remnant EBLFs on Mt. Gele (GL), Mt. Tieshanping (TSP), and Mt. Jinyun (JY), located from the inner city to outskirts of Chongqing metropolis, Southwest China. Species of Theaceae, Lauraceae, Symplocaceae, and other families, which are essential floristic components of primary EBLFs, were still the main components at the three sites. GL and JY showed higher biodiversity, with richer heliophytes and shade-tolerant species, respectively. Castanopsis carlesii var. spinulosa was the sole dominant species at all three sites in woody layer, with codomination by Pinus massoniana and Cinnamomum camphora at GL and by Machilus pingii and Castanopsis fargesii at JY; these evergreen broad-leaved trees all showed inverse-J or sporadic-shaped size distribution with large numbers of small stems, but the conifer tree Pinus massoniana showed unimodal distribution with small stems at GL. The height growth of tree species, especially Castanopsis carlesii var. spinulosa, was increasingly restricted from JY to TSP to GL. Sprouting is an important life history strategy at community and population level, and differences were exhibited from GL to TSP to JY. A rural–urban gradient from JY to TSP to GL was indicated in this study. Species composition, biodiversity, and stand structure of these remnant EBLFs showed obvious differences along this gradient, and conservation responses to address the effects of urbanization need to be carefully considered.

Seasonal dynamics of dissolved organic carbon, nitrogen and other nutrients in soil of Pinus massoniana stands after pine wilt disease disturbance

To understand changes in soil nutrients in Pinus massoniana forests affected by pine wilt disease (PWD), we examined the seasonal variation in dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and soil nutrients in Hefei, East China. The results showed a considerable decline in the population density and basal area in both highly disturbed (HD) and moderately disturbed (MD) forest stands and an increase in dead pine trees, causing pronounced changes in the stand structure and soil nutrient status. The concentrations of DOC and NO3-- N were significantly (p < 0.05) higher in every season in the disturbed forests compared to the undisturbed (UD) forest stand. However, during spring and summer, the variation in the DON and NH4+-N values was significantly (p < 0.05) lower in the HD forest stand than in the UD stand; total N concentrations were higher in the disturbed forests in every season. During spring and autumn, the variation in total P values was significantly (p < 0.05) lower in the MD forest stand than in the UD stand, whereas the total P values were significantly (p < 0.05) lower in every season in the HD stand than in the UD stand. In this study, disturbance resulted in a considerable increase in DOC, N and NO3-- N when compared to the UD stand and a pronounced increase in soil nitrate in the HD stand, which may lead to soil acidification, thereby increasing the possibility of soil nutrient leaching.