369 research outputs found
Biomass-dominant species shape the productivity-diversity relationship in two temperate forests
No full textInternational audienceAbstractKey messageA negative productivity-diversity relationship was determined for biomass-dominant species at the community level. This study thus supports the hypothesis in which the effects of individual species on the productivity-diversity relationships at the community level are related to their biomass density, an important functional trait.ContextThe productivity-diversity relationships have been extensively studied in various forest ecosystems, but key mechanisms underlying the productivity-diversity relationships still remain controversial.AimsThe objective of this study is to explore the productivity-diversity relationships at the community level, and to investigate the roles of individual species in shaping the community-level relationships between productivity and diversity under different forest types.MethodsThe study was conducted in two fully stem-mapped temperate mixed forest plots in Northeastern China: a natural secondary forest plot, and an old-growth forest plot. An individual-based study framework was used to estimate the productivity-diversity relationships at both species and community levels. A homogeneous Thomas point process was used to evaluate the significance of productivity-diversity relationship deviating from the neutral.ResultsAt the species level, most of the studied species exhibit neutral productivity-diversity relationship in both forest plots. The percentage of species showing negative productivity-diversity relationship approaches linearly a peak value for very close neighborhoods (the secondary forest plot: r = 3 m, 38%; the old-growth forest plot: r = 4 m, 42%), and then decreases gradually with increasing spatial scale. Interestingly, only a few species displayed positive productivity-diversity relationship within their neighborhoods. Dominant species mainly exhibit negative productivity-diversity relationship while tree species with lower importance values exhibit neutral productivity-diversity relationship in both forests. At the community level, a consistent pattern of productivity-diversity relationship was observed in both forests, where tree productivity is significantly negatively associated with local species richness. Four biomass-dominant species (Juglans mandshurica Maxim., Acer mono Maxim.,Ulmus macrocarpa Hance and Acer mandshuricum Maxim.) determined a negative productivity-diversity relationship at the community level in the secondary forest plot, but only one species (Juglans mandshurica) in the old-growth forest plot.ConclusionThe productivity-diversity relationship is closely related to the dominance of individual species at the species level. Moreover, this analysis is the first to report the roles of biomass-dominant species in shaping the productivity-diversity relationship at the community level
Relationships between tree biomass productivity and local species diversity
No full textThis study evaluated the relationship between the productivity of aboveground coarse woody biomass and species richness at individual species and community levels in two large and fully stem-mapped temperate forest plots in northeastern China. Although productivity-diversity relationships (PDRs) have been investigated for different forest ecosystems, specific patterns have rarely been documented for individual species. In our study, the PDR patterns were found to be scale dependent at the community level in both research forests. Productivity is positively linked with species richness at the 20 x 20 m sampling scale. At the 40 x 40 m scale, however, significantly positive PDRs were only observed in the mature forest. A summary statistic combining both productivity and richness characteristics was used to investigate whether and at which spatial scale individual species show positive, negative, or neutral PDRs. The results show that 66.7% of all focal species exhibited positive or negative PDRs in the near-mature forest, while 64.3% exhibited positive or negative PDRs in the mature forest. Contrary to expectations, there were few species showing positive PDRs in either forest. PDR patterns were found to be scale dependent in both forest types: Negative PDRs dominate at close neighborhoods in the near-mature forest, while both positive and negative PDRs were found in the mature forest. To our knowledge, this is the first analysis that evaluates the PDRs of individual species based on facilitative and competitive effects in their neighborhoods
Cross‐scale effects of multi‐strata plant diversity on ecosystem multifunctionality in temperate forests
No full textAbstract Unravelling the complex interplay between biodiversity and ecosystem multifunctionality (EMF) in naturally assembled communities is crucial. However, studies on the effects of biodiversity and species composition across different forest strata on EMF at varying spatial scales are still limited in temperate forests. Based on a large set of field observations, we explored the relationships between the diversity of trees and understory herbs and EMF across multiple spatial scales. Within the Hill–Chao numbers framework, we measured diversity in different forest strata and decomposed regional community EMF into α‐ and β‐components. Linear mixed‐effects models and structural equation modelling were applied to investigate the relationships between tree and herb α‐diversity and α‐EMF (the capacity of a specific community to deliver multiple ecosystem services and benefits), as well as between tree and herb β‐diversity and β‐EMF (the spatial dissimilarity of multiple ecosystem functions among local communities). We found that α‐EMF positively responded to tree α‐diversity, though less so by herb α‐diversity. Within regional communities, both tree and herb β‐diversity had positive effects on β‐EMF, with comparable relative importance. Synthesis . Our results show that tree and understory herb diversity (an often overlooked component of forest communities) are both essential for sustaining ecosystem multifunctionality (EMF) across multiple spatial scales in naturally assembled temperate forests of northeastern China. By integrating multi‐strata plant diversity across different spatial scales, our study provides new insights into the patterns and mechanisms underlying the biodiversity–EMF relationship in these forest ecosystems.National Key Research and Development Program of China https://doi.org/10.13039/50110001216
T ree diversity across multiple scales and environmental heterogeneity promote ecosystem multifunctionality in a large temperate forest region
No full textAbstract Aim Biodiversity across different scales provides multidimensional insurance for ecosystem functioning. Although the effects of biodiversity on ecosystem multifunctionality are well recorded in local communities, they remain poorly understood across scales (from local to larger spatial scales). This study evaluates how multiple attributes of biodiversity maintain ecosystem multifunctionality from local to regional scales, across diverse environmental gradients. Location North‐eastern China. Time Period 2017. Major Taxa Studied Woody plants. Methods We define multifunctionality using both averaged and modified multiple‐threshold approaches. Multiple dimensions of biodiversity across varying spatial scales were measured within the framework of Hill–Chao numbers. Using variance decomposition, linear mixed models and structural equation modelling, we explored how multiple attributes of tree diversity at varying spatial scales affect multifunctionality, and how these relationships are modulated by environmental drivers. Results We found that both α‐ and β‐diversity are critical for regional community multifunctionality, while the relationships between species, functional and phylogenetic diversity and multifunctionality decoupled across spatial scales and thresholds of ecosystem functioning. Phylogenetic β‐diversity and species α‐diversity are, respectively, more important for promoting high‐ and moderate‐threshold multifunctionality (e.g. EMF T90 and EMF T50 ) in regional communities. Environmental drivers typically have stronger effects than biodiversity on multifunctionality. Soil and climatic conditions had either direct effects on multifunctionality or indirect ones mediated by species α‐diversity. Environmental heterogeneity is important for high‐threshold multifunctionality, exerting directly and indirectly through phylogenetic β‐diversity. Latitude not only directly influences multifunctionality but also modulates it through species α‐diversity and phylogenetic β‐diversity. Main Conclusions This study underscores the positive effects of biodiversity on multifunctionality across multiple dimensions. Based on our findings, we conclude that any design of a forested landscape that is aimed at maximizing multifunctionality should consider maintaining high local diversity as well as forest community heterogeneity at varying scales
Reproduction and vegetative growth in the dioecious shrub Acer barbinerve in temperate forests of Northeast China
No full textKey message Trade-off in dioecious plant. The trade-off between reproduction, vegetative growth and maintenance is a major issue in the life history of an organism and a record of the process which is producing the largest possible number of living offspring by natural selection. Dioecious species afford an excellent opportunity for detecting such possible trade-offs in resource allocation. In this study, we selected the dioecious shrub Acer barbinerve to examine possible trade-offs between reproduction and vegetative growth in both genders at different modular levels during three successive years. Reproductive and vegetative biomass values were assessed during successive years to evaluate their intra-annual and inter-annual trade-offs. These trade-offs were examined at shoot, branch and shrub modular levels in Acer barbinerve shrubs. An intra-annual trade-off was detected at the shoot level for both genders in 2011 and 2012. Both males and females showed a negative correlation between reproduction and vegetative growth, but this was more prominent in males. For the females of the species, inter-annual trade-offs were only found at branch and shrub levels. Slightly negative correlations in females were detected between the reproduction in 2012 and the reproduction in the two previous years. The gender ratio was significantly male biased during the three successive years of our investigation. Females had higher mortality rates in the larger diameter classes, both in 2011 and 2012. This study revealed a clear trade-off between reproduction and vegetative growth in Acer barbinerve, but results varied between males and females. The degree of autonomy of the different modular levels may affect the ability to detect such trade-offs
Reduced soil moisture caused by human disturbance mediates the biodiversity effects on ecosystem multifunctionality across stand ages in the temperate forests of North-Eastern China
No full texthttp://dx.doi.org/10.13039/501100001809 National Natural Science Foundation of Chinahttp://dx.doi.org/10.13039/501100002855 Ministry of Science and Technology of the People's Republic of Chinahttp://dx.doi.org/10.13039/501100012166 National Key Research and Development Program of Chin
Estimating the effects of functional diversity and composition on the spatial variability of ecosystem multifunctionality in a large temperate forest region
No full textAbstract Functional diversity and composition have been shown to significantly influence the temporal variability of ecosystem functioning. However, their impact on the spatial variability of multiple ecosystem functions (multifunctionality) is still unknown. Therefore, this study aims to explore how functional diversity and composition affect the spatial variability of ecosystem multifunctionality (EMF-SV) under different environmental conditions in a temperate forest region. Regional communities representing specific spatial scales were established by assembling different numbers of sample plots. The EMF-SV was represented by the ratio of the standard deviation to the mean value of ecosystem multifunctionality within each regional community. Linear mixed-effects models were used to evaluate the effects of functional diversity and composition on the EMF-SV at different spatial scales. Structural equation models were applied to explore the direct and indirect pathways of functional diversity and composition influencing the EMF-SV. Our results show that functional diversity and composition had significant effects on the EMF-SV, and these effects changed with spatial scales and environmental conditions. They affected the EMF-SV directly or indirectly through species asynchrony and population stability. Our results demonstrate the role of functional traits in regulating the EMF-SV across spatial scales and explore the main impact mechanisms. This will contribute to our understanding and protection of ecosystem multifunctionality in temperate forests.the National Key R&D Program of Chinathe Program of National Natural Science Foundation of China http://dx.doi.org/10.13039/50110000180
Home beyond the house: the meaning of home for people living in Yanxia village, Zhejiang Province, China
No full textUnder the guidance of a new policy released by China’s central authority in 2006, which calls for “Building a New Socialist Countryside,” newly planned settlements with rows of nearly identical houses have rapidly emerged in rural China. As a result, rural residents, who, for generations, have lived in the same village in the countryside, are relocated to new settlements. Historic and vernacular houses were demolished; social relations among residents were broken down due to the relocation; cultural traditions were forgotten as the result of their detachment from associated cultural landscapes. The reason behind this phenomenon is the common understanding embraced by scholars and local government officials that new and modern houses are the foundation for creating the new socialist countryside. This policy has broad implications for Chinese society. According to the latest census in 2010, there are 674 million people living in rural China, over 50 percent of the Chinese population, many of whom live in traditional and vernacular built settlements that retain rich and diverse cultural heritage. The reconstruction of the built environments and the relocation of the residents have detached residents from the built environments where their cultural heritage has been rooted and nurtured.
This dissertation examines the ways in which tradition has affected the physical, psychological, and social constructions of home for the residents living in Yanxia. This dissertation argues that, in the context of rural China, the nature of vernacular settlements call for an understanding of place and certain aspects of Chinese culture challenge the spatial boundary of house. Thus, the meaning of home for people living in Yanxia goes beyond the physical boundary of the house or the legal boundary of the homestead and is attached to cultural traditions embraced by individuals or shared by the residents of Yanxia. Specifically, the meaning of home for the residents living in Yanxia ties to their bound kinship structure established in the early fourteenth century, their family-based economic practices since the 1850s, and, more importantly, the land on which their houses have been situated for generations.
This dissertation integrates the methodologies of ethnographic fieldwork and archival research. In particular, participants were asked to take photographs of aspects of their jia that are meaningful to them. Semi-structured and in-depth interviews then followed focusing on the contents of the photographs. This dataset was triangulated with data obtained from archival research and observations.
Situated between the scholarship on place, home, and tradition, this dissertation offers a unique understanding of the role of tradition in the physical, psychological, and social construction of home within the context of the historic and vernacular built environment in rural China. This dissertation expands and advances the literature on place, home, and tradition in vernacular environment and non-western cultures.
Moreover, the use of the method of photovoice, empowers the participants, who represent more than 50 percent of the Chinese population yet belong to a social group that is underrepresented in scholarship and underserved in modern China. Finally, this study provides guidance for the local practice of the policy of Building a New Socialist Countryside, which helps to preserve cultural traditions recognized by the residents and to sustain meanings of home.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2017-05-01The student, Wei Zhao, accepted the attached license on 2015-04-20 at 09:30.The student, Wei Zhao, submitted this Dissertation for approval on 2015-04-20 at 09:52.This Dissertation was approved for publication on 2015-04-22 at 13:34.DSpace SAF Submission Ingestion Package generated from Vireo submission #7943 on 2015-07-22 at 14:25:28Made available in DSpace on 2015-07-22T22:45:34Z (GMT). No. of bitstreams: 2
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Corrosion behavior of sintered CeNdFeB magnets in different solutions
No full textThe capability of CeNdFeB as a substitute for NdFeB is of considerable interest due to its cost effectiveness and fascinating magnetic properties. In this paper, we have systematically investigated the corrosion behavior of the sintered CeNdFeB magnets in alkaline and acidic media in order to evaluate their commercial viability. Electrochemical and immersion tests have been conducted using sintered CeNdFeB magnets with different amounts of Ce (0.0 wt%, 29.6 wt%, 44.6 wt%, 54.8 wt%) as substitution of Nd in different concentrations of sodium hydroxide (NaOH), nitric acid (HNO3), hydrochloric acid (HCl), sulfuric acid (H2SO4), and oxalic acid (H2C2O4). We have found that the sintered CeNdFeB magnets exhibit passive behavior and the corrosion rate decreases in NaOH and H2C2O4 solutions by comparison with sintered NdFeB magnets. When exposed in strong acids, the sintered CeNdFeB has comparable corrosion properties with sintered NdFeB in HNO3 solution and lower anticorrosion properties in HCl and H2SO4 solutions. (C) 2017 Elsevier B.V. All rights reserved
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