1,720,965 research outputs found
Changes in soil carbon and nitrogen stocks followed the conversion from secondary forest to Chinese fir and Moso bamboo plantations
No full textLand use change is the second main reason for carbon (C) emissions after fossil fuel combustion, and it is recognized as an important driving force for soil organic carbon (SOC) and soil nitrogen (N) dynamics. Conversion of the secondary forest to Chinese fir (Cunninghamia ianceolata [Lamb.] Hook) and Moso bamboo (Phyllostachys heterocycle [Carr] Mitford cv. Pubescens) plantations represents one of the most important land use changes in subtropical China. However, the effects of these land use changes on the SOC and N stocks were not well documented. Therefore, in this study soil samples were collected in a secondary forest, a 17-year Chinese fir and a 18-year Moso bamboo plantation after the conversion from the secondary forest in November 2013, and total SOC and N concentrations were measured. Total SOC and N concentrations decreased with soil depth over the 0-50 cm in three land uses, and they were significantly higher in the secondary forest than those of Chinese fir and Moso bamboo plantations; however, these concentrations were not significantly different between Chinese fir and Moso bamboo plantations. Top soil (0-10 cm) stored one third of total SOC and N stocks. SOC and N stocks in the secondary forest were significantly higher than those of Chinese fir and Moso bamboo plantations with values of 203.68, 12734 and 118.25 t. ha(-1) for SOC stock and 924, 5.10 and 635 t. ha(-1) for N stock. The results indicated that converting the secondary forest to Chinese fir and Moso bamboo plantations significantly decreased the SOC and N stocks over 0-50 cm. (C) 2015 Elsevier B.V. All rights reserved
Soil respiration and carbon balance in a Moso bamboo (Phyllostachys heterocycla (Carr.) Mitford cv. Pubescens) forest in subtropical China
No full textUnderstanding spatial and temporal variation in soil respiration (RS) in different forest ecosystems is crucial to estimate the global carbon balance. Bamboo forest is a special forest type in southern China covering an area of 5.38 million ha, 70% of which are Moso bamboo (Phyllostachys heterocycla (Carr.) Mitford cv. Pubescens) forests. Bamboo forests contribute more than 10% to the whole carbon stock of forest ecosystems in China, and therefore play a critical role in the regional and national carbon balance. However, little information on the seasonal dynamic of RS and the carbon balance of Moso bamboo forests is available. In this study, litter removal and trenching methods were applied to partition RS into root respiration (RR), litter respiration (RL) and soil organic matter derived respiration (RM), and to study their seasonal dynamics and carbon balance in a pure Moso bamboo forest. Monthly RS, its source components and combined monthly environmental factors were measured. RS and its source components showed a significant seasonal variability with higher values from June to August and lower values from December to February driven by soil temperature and moisture (P < 0.001). Annual average RS, RR, RL and RM were 2.37, 0.69, 0.58 and 1.10 mu mol m(-2) s(-1) with Q10 values of 1.25, 1.15, 1.19 and 1.26, respectively. Annual RS was 8.97 t C ha(-1), and RR, RL and RM contributed 29%, 22% and 49%, respectively. Annual NEP was 4.72 t C ha(-1) y(-1), indicating that the Moso bamboo forest studied is a significant carbon sink
Soil respiration and net ecosystem production in relation to intensive management in Moso bamboo forests
No full textMoso bamboo forests represent an important forest type commonly found throughout subtropical China and are characterized by fast growing forests, and involves intensive management, such as reclamation, fertilization, and understory removal. However, effects of intensive management on soil respiration (R-S) and net ecosystem production (NEP) remain unclear. In this study, R-S was partitioned into root respiration (R-R), litter respiration (R-L), and soil organic matter derived respiration (R-M) by litter removal and trenching approaches. One-year measurements of respiration rates, soil temperature, and soil moisture were conducted in an unmanaged and an intensively managed stand. Regardless of stand management, R-S and source components increased exponentially with soil temperature and linearly with soil moisture. Temperature sensitivity (Q(10)) ranged from 1.6 to 2.5, with the highest value for R-M, highlighting the importance of R-M in regulating the response of R-S to soil temperature change. Annual R-S, R-R, R-L, and R-M were 32.6, 10.7, 6.9, and 15.0 t CO2 ha(-1) a(-1) for unmanaged stand, compared to 38.6, 12.5, 7.1, and 18.9 t CO2 ha(-1) a(-1) for intensive managed stand, respectively, indicating that intensive management increased R-S by R-R and R-M. Intensive management also increased NEP with 17.2 t CO2 ha(-1) a(-1) for unmanaged stand and 20.4 t CO2 ha(-1) a(-1) for intensive managed stand. This increase was mainly attributed to the increase in net primary production of bamboo forests under intensive management. However, the sustainability of intensive management needs further investigation due to the reduction of soil organic carbon content after intensive management. Forest management associated with the reduction in soil CO2 flux and increase in stand production should be developed for Moso bamboo forests. (C) 2015 Published by Elsevier B.V
A comparison of soil respiration, carbon balance and root carbon use efficiency in two managed Moso bamboo forests in subtropical China
Full text linkMoso bamboo forest (Phyllostachys heterocycla [Carr.] Mitford cv. Pubescens) is an important forest type in subtropical China and comprises an important pool in the global carbon cycle. Understanding the effects of the stand management, such as understory removal, on soil respiration (RS) will help to provide a more accurate estimation of carbon cycling and predict future climate change. The study aimed to compare RS and net ecosystem production (NEP) in two Moso bamboo forests managed by the application of herbicide (AH) and conventional hand-weeded (HW) treatment, and further examine their root carbon use efficiency (RCUE). Trenching and litter removal were used to partition the source components of RS and one-year field measurement was conducted. Maximum-minimum approach was used to estimate fine root production. NEP was determined by the balance between NPP of vegetation and heterotrophic respiration (RH) of soil. RCUE was calculated using an indirect method. In both stands, soil temperature and soil moisture at 5 cm depth were the main driving forces to the seasonality of RS. Annual RS was 31.6 t CO2 ha-1 for the stand AH and 33.9 t CO2 ha-1 for the stand HW, while net ecosystem production (NEP) were 21.9 and 21.1 t CO2 ha-1, respectively, indicating that the both Moso bamboo stands acted as carbon sinks in the scenarios of current climate change. The RCUE was 30.6% for the stand AH, which was significantly lower than that for the stand HW (58.8%). This result indicates that different stand management practices can alter RCUE and the assumed constant universal carbon use efficiency (CUE) of 50% is not appropriate in Moso bamboo forests. This study highlight the importance of partition the source components of RS and accurate estimation of RCUE in modelling carbon cycling in Moso bamboo forests.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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