147 research outputs found
Prescribed fire alters nematode communities in an old-field grassland
Get PDFFire is a common disturbance in many biomes, with both beneficial and detrimental effects on soil biology, which largely depend on fire intensity. However, little is known about the impact of fire on soil nematode communities in terrestrial ecosystem. In the present study, we investigated the effects of short-term prescribed fire on soil nematode communities and soil properties in an old-field grassland in Northern China. The results showed that burning significantly increased soil nematode abundance by 77% and genus richness by 49% compared to the control. Burning also decreased taxon dominance by 45% (Simpson's D) and increased nematode diversity by 31% (Shannon-Weaver H'). However, burning increased plant parasites (particularly genera Cephalenchus and Pratylenchus) and shifted community to more bacterial-feeding genera (i.e., decreased Channel Index). Generally, burning increased soil bio-available nitrogen (NH4+–N and NO3−–N) content, which would be the main drivers causing nematode community to flourish via a “bottom-up” effect. These results suggest that prescribed fire increases nematode diversity and alters community composition toward more plant parasites and bacterial feeders. Our findings highlight the importance of prescribed fire management in shaping short-term nematode community structure and function, but the long-term effects and impacts of these changes on soil nutrient and carbon cycling remain unknown.This article is published as Song, Min, Marshall D. McDaniel, Chen Zhu, Feng Lin, and Yaojun Zhang. "Prescribed fire alters nematode communities in an old‐field grassland." Ecology and Evolution 13, no. 4 (2023): e9977. doi:10.1002/ece3.9977.© 2023 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited
A new proof of Wojcicka's conjecture
No full textAbstractA graph G is 3-domination-critical if its domination number γ is 3 and the addition of any edge decreases γ by 1. Wojcicka conjectured that every 3-domination-critical graph with δ⩾2 has a hamiltonian cycle (J. Graph Theory 14 (1990) 205–215). The conjecture had been proved and its proof consists of two parts: the case α⩽δ+1 (J. Graph Theory 25 (1997) 173–184) and the case α=δ+2 (Discrete Appl. Math. 92 (1999) 57–70). In this paper, we give a new and simple proof of the conjecture by using Hanson's (J. Combin. Math. Combin. Comput. 13 (1993) 121–128) and Bondy-Chvátal's (Discrete Math. 15(1976) 111–135) closure operations
Financial Intermediation Development and Economic Growth: Does the Chinese Counterexample Exist?
No full textIn terms of the degree-of-freedom of bank loan decision-making, the ratio of loans of private enterprises and individuals to total loans is used to measure the development of China's financial intermediation. Applying generalized method of moments estimation developed for dynamic panel data models, the present paper finds that the effect of financial intermediation development on economic growth is positive and statistically significant when controlling for other variables, such as human capital, foreign direct investment, securitization and foreign trade. The empirical results indicate that the concept of the so-called Chinese counterexample in financial development is questionable. Financial system reforms, including encouraging banks to operate independently, reducing or eliminating mandatory loans, and making financial decision-making more market-oriented, are important for China's economic growth. Copyright (c) 2010 The Author China & World Economy (c) 2010 Institute of World Economics and Politics, Chinese Academy of Social Sciences.
Hamilton-connectivity of 3-Domination Critical Graphs with α=δ+ 2
No full textAbstractA graph G is 3-domination critical if its domination number \gamma is 3 and the addition of any edge decreases \gamma by 1. It was proved by Favaron et al. that α≤δ+ 2 for any connected 3-domination critical graph. Denote byτ (G) the toughness of a graph G. Recently Chen et al. conjectured that a connected 3-domination critical graph G is Hamilton-connected if and only if τ(G) > 1 and showed the conjecture is true when α≤δ. In this paper, by using a closure operation defined by Bondy and Chvátal, we show the conjecture is true whenα=δ+ 2
Hamilton-connectivity of 3-domination-critical graphs with α⩽δ
No full textAbstractA graph G is 3-domination critical if its domination number γ is 3 and the addition of any edge decreases γ by 1. Let G be a 3-connected 3-domination critical graph with α(G)⩽δ(G). In this paper, we show that G is Hamilton-connected if and only if τ(G)>1, where τ(G) is the toughness of G
Applied Study of Layer 3 Switching Configuration Based on VLAN among Colleges' Library Network Systems
No full textDisruption of oxide films during spark plasma sintering of micrometric-sized Al powders and its effect on microstructure and tensile properties of the consolidated Al
No full textThe Use of 3D Convolutional Autoencoder in Fault and Fracture Network Characterization
No full textConventional pattern recognition methods directly use 1D poststack data or 2D prestack data for the statistical pattern recognition of fault and fracture network, thereby ignoring the spatial structure information in 3D seismic data. As a result, the generated fault and fracture network is not distinguishable and has poor continuity. In this paper, a fault and fracture network characterization method based on 3D convolutional autoencoder is proposed. First, in the autoencoder training frame, 3D prestack data are used as input, and the 3D convolution operation is used to mine the spatial structure information to the maximum and gradually reduce the spatial dimension of the input. Then, the residual network is used to recover the input’s details and the corresponding spatial dimension. Lastly, the hidden features extracted by the encoders are recognized via k-means, SOM, and two-step clustering analysis. The validity of the method is verified by testing the seismic simulation data and applying real seismic data. The 3D convolution can directly process the seismic data and maximize the prestack texture attributes and spatial structure information provided by 3D seismic data without dimensionality reduction and other preprocessing operations. The interleaving convolution layer and residual block overcome low learning and accuracy rates due to the deepening of networks
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