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  • Volume 1 Issue 2
      
    Research Articles
    Jiquan Chen, Bin Zhao, Wenwei Ren, Sari C. Saunders, Zhijun Ma, Bo Li, Yiqi Luo, Jiakuan Chen
    2008, 1 (2): 79-84.
    Abstract ( 73 )   PDF   Save
    Aims This synthesis paper is developed to provide a summary of ecological, socioeconomic challenges facing the estuarine wetlands within the Yangtze River delta.
    Methods We combined literature review of the estuarine wetlands and ground measurements of sedimentation, vegetation, and carbon fluxes to illustrate the foreseeable crises in managing these wetlands that play a critical role in Shanghai's urban development. Where the Yangtze River meets the Pacific Ocean, 4.15 × 10 8 mg/year of suspended sediments are deposited along mainland and island shorelines of the 40?000 km 2 delta—resulting in an average growth rate of land outwards 64 m/year since 1951. However, completion of the Three Gorges Dam in 2003, and earlier dam projects, reduced the rates of sedimentation and growth of the islands. To meet the increasing demands for lands and agriculture, policymakers have attempted to enlarge the islands by diking coastal areas and introducing Spartina alterniflora— a grass native to tidal salt marshes of the southeastern USA but exotic to China. Spartina is one of the 16 greatest invasive species listed by the State Environmental Protection Administration of China. Successful plantations and rapid spread of this species have increased the production and fertility of the coast, but at the cost of native ecosystems. We outline the social, economic, and ecological controversies related to this land management strategy in the context of global warming.
    Important findings Combinations of these changes, including sea level rise, and alterations to storm patterns and long-shore currents, with the continued spread of Spartina, human population growth, and river flow and sediment reduction will make current management untenable.
    Deqiang Zhang, Dafeng Hui, Yiqi Luo, Guoyi Zhou
    2008, 1 (2): 85-93.
    Abstract ( 93 )   PDF   Save
    Aims We aim to construct a comprehensive global database of litter decomposition rate (k value) estimated by surface floor litterbags, and investigate the direct and indirect effects of impact factors such as geographic factors (latitude and altitude), climatic factors (mean annual tempePlrature, MAT; mean annual precipitation, MAP) and litter quality factors (the contents of N, P, K, Ca, Mg and C:N ratio, lignin:N ratio) on litter decomposition.
    Methods We compiled a large data set of litter decomposition rates (k values) from 110 research sites and conducted simple, multiple regression and path analyses to explore the relationship between the k values and impact factors at the global scale.
    Important findings The k values tended to decrease with latitude (LAT) and lignin content (LIGN) of litter but increased with temperature, precipitation and nutrient concentrations at the large spatial scale. Single factor such as climate, litter quality and geographic variable could not explain litter decomposition rates well. However, the combination of total nutrient (TN) elements and C:N accounted for 70.2% of the variation in the litter decomposition rates. The combination of LAT, MAT, C:N and TN accounted for 87.54% of the variation in the litter decomposition rates. These results indicate that litter quality is the most important direct regulator of litter decomposition at the global scale. This data synthesis revealed significant relationships between litter decomposition rates and the combination of climatic factor (MAT) and litter quality (C:N, TN). The global-scale empirical relationships developed here are useful for a better understanding and modeling of the effects of litter quality and climatic factors on litter decomposition rates.
    Bernhard Schmid, Andy Hector, Prasenjit Saha, Michel Loreau
    2008, 1 (2): 95-102.
    Abstract ( 89 )   PDF   Save
    Aims The potential for mixtures of plant species to produce more biomass than every one of their constituent species in monoculture is still controversially discussed in the literature. Here we tested how this so-called transgressive overyielding is affected by variation between and within species in monoculture yields in biodiversity experiments.
    Methods We use basic statistical principles to calculate expected maximum monoculture yield in a species pool used for a biodiversity experiment. Using a real example we show how between- and within-species variance components in monoculture yields can be obtained. Combining the two components we estimate the importance of sampling bias in transgressive overyielding analysis.
    Important findings The net biodiversity effect (difference between mixture and average monoculture yield) needed to achieve transgressive overyielding increases with the number of species in a mixture and with the variation between constituent species in monoculture yields. If there is no significant variation between species, transgressive overyielding should not be calculated using the best monoculture, because in this case the difference between this species and the other species could exclusively reflect a sampling bias. The sampling bias decreases with increasing variation between species. Tests for transgressive overyielding require replicated species' monocultures. However, it can be doubted whether such an emphasis on monocultures in biodiversity experiments is justified if an analysis of transgressive overyielding is not the major goal.
    Shuli Niu, Shiqiang Wan
    2008, 1 (2): 103-110.
    Abstract ( 81 )   PDF   Save
    Aims Quantifying changes in plant growth and interspecific interactions, both of which can alter dominance of plant species, will facilitate explanation and projection of the shifts in species composition and community structure in terrestrial biomes expected under global warming. We used an experimental warming treatment to examine the potential influence of global warming on plant growth and interspecific interactions in a temperate steppe in northern China.
    Materials and Methods Six dominant plant species were grown in monoculture and all 15 two-species mixtures for one growing season under ambient and elevated temperatures in the field. Temperature was manipulated with infrared radiators.
    Important findings Total biomass of all the six plant species was increased by 34–63% in monocultures and 20–76% in mixtures. The magnitude of the warming effect on biomass was modified by plant interactions. Experimental warming changed the hierarchies of both competitive response and competitive effect. The competitive ability (in terms of response and effect) of one C4 grass (Pennisetum centrasiaticum) was suppressed, while the competitive abilities of one C3 forb (Artemisia capillaris) and one C3 grass (Stipa krylovii) were enhanced by experimental warming. The demonstrated alterations in growth and plant interactions may lead to changes in community structure and biodiversity in the temperate steppe in a warmer world in the future.
    Christian Damgaard, Jacob Weiner
    2008, 1 (2): 111-116.
    Abstract ( 71 )   PDF   Save
    Aims We present an improved model for the growth of individuals in plant populations experiencing competition.
    Methods Individuals grow sigmoidally according to the Birch model, which is similar to the more commonly used Richards model, but has the advantage that initial plant growth is always exponential. The individual plant growth models are coupled so that there is a maximum total biomass for the population. The effects of size-asymmetric competition are modeled with a parameter that reflects the size advantage that larger individual have over smaller individuals. We fit the model to data on individual growth in crowded populations of Chenopodium album .
    Important findings When individual plant growth curves were not coupled, there was a negative or no correlation between initial growth rate and final size, suggesting that competitive interactions were more important in determining final plant size than were plants' initial growth rates. The coupled growth equations fit the data better than individual, uncoupled growth models, even though the number of estimated parameters in the coupled competitive growth model was far fewer, indicating the importance of modeling competition and the degree of size-asymmetric growth explicitly. A quantitative understanding of stand development in terms of the growth of individuals, as altered by competition, is within reach.
    Ruth Sherman, Renee Mullen, Li Haomin, Fang Zhendong, Wang Yi
    2008, 1 (2): 117-136.
    Abstract ( 93 )   PDF   Save
    Aims Conduct a quantitative, but rapid, regional-level assessment of the alpine flora across northwest Yunnan (NWY) to provide a broad-based understanding of local and regional patterns of the composition, diversity and health of alpine ecosystems across NWY.
    Methods A stratified random sampling design was employed to select sites across the different mountain ranges of NWY. Vegetation was sampled by stratifying each site by the three major alpine vegetation community types: meadow, dwarf shrub and scree. Two 50-m transects were randomly located within each community type at each sampling site with 10 1-m 2 subplots systematically placed along each transect. Environmental variables were recorded at each transect. Multivariate analyses were used to classify the major plant community assemblages and link community patterns to environmental and habitat variables.
    Important findings Forb species richness varied from 19 to 105 species per site (21 sites total) with an average of 59 species per site (60 m 2 sampled per site). Most species were patchily distributed with narrow distributions and/or small population sizes; over half the species occurred at only one or two sites. Distinct species assemblages were identified in the meadow vegetation that was strongly aggregated by geographic location suggesting the presence of distinct phytogeographic zones of the meadow alpine flora. Elevation and geographic location were the dominant environmental gradients underlying the variations in species composition. Jaccard's coefficient of similarity averaged only 10% among sites indicating there was little similarity in the alpine flora across the region. The alpine vegetation is highly heterogeneous across the complex landscape of the Hengduan Mountains of NWY. Conservation strategies need to take into account the large geographic differences in the flora to maximize protection of biodiversity.
    Xiongwen Chen, Bai-Lian Li, Xing-Shi Zhang
    2008, 1 (2): 137-141.
    Abstract ( 58 )   PDF   Save
    Aims Monitoring and assessing diversity change at a large scale is important for any meaningful biodiversity conservation and management. Spatial analysis techniques can provide information about different aspects of diversity distribution including change. We applied some common spatial analysis methods and additive partitioning of species diversity in the Northeast China Transect as a case study to show how to characterize the distribution and change of tree diversity in this area from different perspectives.
    Methods The field data were collected from the permanent plots conducted every 4 km. The additive partitioning of species diversity was used to characterize the diversity of tree species at different scales. Moran's I was used for identifying the spatial scale of autocorrelation, lacunarity was studied for diversity patch contagion and dispersion and spectral entropy was used for assessing the overall spatial distribution.
    Important findings Data collected from 1986 to 1994 indicate that the change of α diversity was not significant in the study area, but the change of β diversity was significant. The percentage of α diversity in total diversity (γ) increased from 14.2 to 17.2%, and the percentage of β diversity decreased from 85.8 to 82.8%. For both α and β diversities, the scale of spatial autocorrelation decreased at the scale of 25–40 km and increased around 15–20 and 200 km. The lacunarity of α diversity decreased significantly and there was a sudden change at the scale of 56–68 km, but the lacunarity of β diversity increased across scales. The spectral entropy decreased slightly in α diversity and remained similar for β diversity. By using spatial analysis, we can monitor the diversity change over a large area and also assess the effectiveness of the current conservation strategies.
    Short Communication
    Wenyun Zuo, Ni Lao, Yuying Geng, Keping Ma
    2008, 1 (2): 143-145.
    Abstract ( 90 )   PDF   Save
    Erratum
    Xianzhong Wang, Angela R. Ngigi, Daniel L. Smith,, Tamara M. McPeek
    2008, 1 (2): 147-147.
    Abstract ( 75 )   PDF   Save
Impact Factor
1.833
5 year Impact Factor
2.299
Editors-in-Chief
Wen-Hao Zhang
Bernhard Schmid