<正>通过对南京市行道树及中山陵风景区森林资源的调查，对城市森林的生态价值进行了经济分析，计算了南京城市森林的生态价值，并从经济学角度为加快城市森林的发展和生态城市建设提出了建议。

There are lots of species of nematodes in a dead pine. However we did not know the pathogenicity of these nematodes to pine except Bursaphelenchus xylophilus and B. mucronatus. It is a basic work for study to collect and conserve these nematodes in pine. In this study, 212 nematode isolates had been collected, which were B. xylophilus, B. mucronatus、B. hofmanni, Aphelenchoides menthae, A. macronucleatus, Seinura sp. and Ektaphelenchidae sp. based on species, and isolates were 171, 22, 5, 1, 8, 3 and 2 respectiVely. Among them, the collection rate was 80.7% of B. xylophilus. According to geographic origins, nematode isolates obtained from China, Japan, America, Canada and Korea were 198, 10, 2, 1 and 1 respectively, and 93.4% nematodes came from China. All the above living nematodes were preserved with Bortrytis cinerea, and the DNA of 173 isolates of B. xylophilus, 5 isolates of B. mucronatus, and 5 isolates of other nematodes were preserved under the condition of -20℃ and -80℃. It was the first time to preserve nematode germplasm in a large scale in China.