Nematode communities were monitored in a field study at depths of 0～10 cmand 10～20 cm throughout a corn (Zea mays L.) growing season in the black soil region of NortheastChina. Plots were cropped corn with (IF) and ...Nematode communities were monitored in a field study at depths of 0～10 cmand 10～20 cm throughout a corn (Zea mays L.) growing season in the black soil region of NortheastChina. Plots were cropped corn with (IF) and without (NF) nitrogen fertilization. Fifteen familiesand 16 genera were observed in the nematode suspensions. Cephalobidae, Rhabditidae, Aphelenchus,Filenchus, and Helicotylenchus were found to be dominant genera/families in both plots at bothdepths. Significant differences were found between treatments and corn growing stages in the totalnumbers of nematodes during the study period. The total numbers of nematodes at the 0～10 cm depthwere higher in the inorganic fertilizer plot than in the control plot (no fertilizer applications)across jointing, filling, and mature stages. Bacterivores were the most abundant trophic groupsunder two treatments and at both depths, and the relative abundance averaged 42.8%.Omuivores-predators at both depths were lower in the inorganic fertilizer plot than in the controlplot during the study period, excluding corn jointing stage. Maturity index (MI) and plant parasiteindex (PPI) were used to detect the differences between the two treatments, MI and PPI wereeffective in distinguishing differences in nematode communities during corn growing season. The roleof nematode communities as bioindicators of ecosystem disturbance due to fertilization is noted.展开更多
Community detection has attracted a great deal of attention in recent years. A parsimony criterion for detecting this structure means that as minimal as possible number of inserted and deleted edges is needed when we ...Community detection has attracted a great deal of attention in recent years. A parsimony criterion for detecting this structure means that as minimal as possible number of inserted and deleted edges is needed when we make the network considered become a disjoint union of cliques. However, many small groups of nodes are obtained by directly using this criterion to some networks especially for sparse ones. In this paper we propose a weighted parsimony model in which a weight coefficient is introduced to balance the inserted and deleted edges to ensure the obtained subgraphs to be reasonable communities. Some benchmark testing examples are used to validate the effectiveness of the proposed method. It is interesting that the weight here can be determined only by the topological features of the network. Meanwhile we make some comparison of our model with maximizing modularity Q and modularity density D on some of the benchmark networks, although sometimes too many or a little less numbers of communities are obtained with Q or D, a proper number of communities are detected with the weighted model. All the computational results confirm its capability for community detection for the small or middle size networks.展开更多
基金the National Key Basic Research Support Foundation(NKBRSF)of China(G1999011804-04) the Foundation of Knowledge Innovation Program of IAE-CAS(Institute of Applied Ecology,the Chinese Academy of Science).
文摘Nematode communities were monitored in a field study at depths of 0～10 cmand 10～20 cm throughout a corn (Zea mays L.) growing season in the black soil region of NortheastChina. Plots were cropped corn with (IF) and without (NF) nitrogen fertilization. Fifteen familiesand 16 genera were observed in the nematode suspensions. Cephalobidae, Rhabditidae, Aphelenchus,Filenchus, and Helicotylenchus were found to be dominant genera/families in both plots at bothdepths. Significant differences were found between treatments and corn growing stages in the totalnumbers of nematodes during the study period. The total numbers of nematodes at the 0～10 cm depthwere higher in the inorganic fertilizer plot than in the control plot (no fertilizer applications)across jointing, filling, and mature stages. Bacterivores were the most abundant trophic groupsunder two treatments and at both depths, and the relative abundance averaged 42.8%.Omuivores-predators at both depths were lower in the inorganic fertilizer plot than in the controlplot during the study period, excluding corn jointing stage. Maturity index (MI) and plant parasiteindex (PPI) were used to detect the differences between the two treatments, MI and PPI wereeffective in distinguishing differences in nematode communities during corn growing season. The roleof nematode communities as bioindicators of ecosystem disturbance due to fertilization is noted.
基金This research is partially supported by the National Natural Science Foundation of China under Grant No. 60873205, Innovation Project of Chinese Academy of Sciences, kjcsyw-sT.
文摘Community detection has attracted a great deal of attention in recent years. A parsimony criterion for detecting this structure means that as minimal as possible number of inserted and deleted edges is needed when we make the network considered become a disjoint union of cliques. However, many small groups of nodes are obtained by directly using this criterion to some networks especially for sparse ones. In this paper we propose a weighted parsimony model in which a weight coefficient is introduced to balance the inserted and deleted edges to ensure the obtained subgraphs to be reasonable communities. Some benchmark testing examples are used to validate the effectiveness of the proposed method. It is interesting that the weight here can be determined only by the topological features of the network. Meanwhile we make some comparison of our model with maximizing modularity Q and modularity density D on some of the benchmark networks, although sometimes too many or a little less numbers of communities are obtained with Q or D, a proper number of communities are detected with the weighted model. All the computational results confirm its capability for community detection for the small or middle size networks.
