Search

In metropolises with high urbanization and being squeezed by a shortage of land available for urban development,it is of great significance to recognize important ecological nodes to designate as protected areas for controlling urban sprawl,and enhancing urban quality of life.In this study,ecological networks analysis has been designed,developed and tested with GIS technique for recognition of important ecological nodes.This paper applies this method to a model of urban district of Nanjing.The procedure was described as follows:(1) the potential ecological networks and ecological nodes were recognized using landscape resistance analysis and network analysis;(2) next,the ecological patches with high special service functions,such as those can protect rivers,provide recreational space,and mitigate industrial pollution,along the recognized potential ecological networks or around ecological nodes were screened;(3) finnaly,the ecological patches with high special service functions greater than a certain size were selected.The results showed that 7 important eco-patches were recommended to designate as permanent green space by law.Furthermore,some suggestion were given to guide the protection of the 7 important eco-patches in the correct direction.

Sugarcane is one of the most important crops for sugar and energy production,and the Guangxi region is the major sugarcane and sugar producing area in China,producing about 60% of China′s sugarcane and sugar.Nitrogen fertilizer input for sugarcane production in China is very high.It is essential to reduce nitrogen fertilizer input and thus cultivation cost while achieving a high yield for sustainable and environmentally friendly sugarcane production.Research on biological nitrogen fixation has increased significantly because of its potential importance to the economy and the environment.Sugarcane plants can obtain nitrogen from biological nitrogen fixation via diazotrophs,and 15N isotope assays have demonstrated that some Brazilian sugarcane varieties are able to obtain considerable nitrogen from biological nitrogen fixation.The aim of this work was to screen and identify nitrogen-fixing bacteria from the rhizosphere of sugarcane cultivated in the diverse geographical region of Guangxi,investigate their diversity and predominant affiliation,and to demonstrate their potential for associative nitrogen fixation with sugarcane as well as plant growth promotion.One hundred and forty eight bacterial isolates associated with sugarcane were isolated from 20 soil samples collected from 10 major production areas over the Guangxi region using Ashby nitrogen deficient minimal media.Thirty six of these isolates were found to have N2 fixing ability as demonstrated by the acetylene reduction assay.All 36 isolates also yielded a polymerase chain reaction product with primers targeting the nifH gene,which encodes a key enzyme in the nitrogen fixation process.Further screening and selection indicated that five efficient isolates(GX0703,GX0798,GX07104,GX08125,and GX0797) were obtained which possessed multiple plant growth promoting traits such as higher N2 fixing,phosphate solubilization and IAA production,and all of the isolates with these attributes may well be valuable for agriculture.To demonstrate their potential for associative nitrogen fixation with sugarcane and growth promotion activities,the five isolates were inoculated into micropropagated sugarcane seedlings,and the seedlings were then incubated in a growth cabinet for 50 d at 28°C.The results indicated that all five isolates significantly promoted the growth of the micropropagated sugarcane seedlings.They also increased the dry weight and nitrogen contents by 29.15 to 57.61% and 29.35 to 45.04%,respectively,compared with the uninoculated controls.Based on phenotypic tests,biolog microplate tests and 16S rRNA gene sequence analysis,the five efficient isolates,GX0703,GX0798,GX07104,GX08125,and GX0797 were identified as Klebsiella sp.,Bacillus megaterium,Pseudomonas sp.,Pantoea sp.and Burkholderia sp.,respectively.These promising associative nitrogen fixation bacteria isolates from the rhizosphere of micropropagated sugarcane showed potential to promote sugarcane production via nitrogen fixation and other plant growth promoting functions.This will improve sugar production efficiency in China and reduce the environmental pollution that results from sugarcane production. The nifH and 16S rDNA sequences of the N fixing bacterial isolates GX0703,GX0798,GX07104,GX08125 and GX0797 were deposited in the GenBank,and the accession numbers were FJ822998,FJ823001,EU938523,FJ822992 and EU938522 for nifH,and FJ823041,FJ823003,FJ823047,FJ823045 and FJ823002 for 16S rDNA sequences,respectively.

Pairwise combinatorial coverage testing which is a significant method for test data generation in functional test fields was discussed.As the method is difficult of solution,a improved method of test data generation for the solution space tree based on intelligent planning was proposed according to the relationship of different factors in the system.The method generates all the available data into a solution space tree,then searches a path from a root node to a leaf node to produce a test data. Experimental results show that this method can test adequately and cover more effect factors of software system by using less test data and can achieve the combinatorial corerage of two factors for test data.As compared with traditional methods,it can obtain the simplest and more complete data sets.In conclusion,it improves the efficiency and veracity of generating test data when this method is taken to a bear space camera software test.