陕北榆阳区植被生态系统净第一性生产力动态

以陕北榆阳区气候及土地利用方面的资料为依据，根据研究区特定的自然环境，结合相关研究成果和实地调查结果选择测算模型，对该区1988～2003年间的植被生态系统净第一性生产力动态变化情况进行估算和分析。研究表明：1988～2003年期间，榆阳区植被生态系统净第一性生产力总体上呈上升态势，总量在1988年的基础上增加了7．75％，年度递增率为0．50％；其中林地和园地净第一性生产力总量增加，增幅分别为11．35％和1054．99％，而草地的净第一性生产力总量呈明显下降趋势，降幅为6．15％；林地、园地和草地分别贡献了整个增量的95．56％、31．82％和-27．38％。榆阳区在研究时段内土地利用类型结构调整提升了区内植被生态系统净第一性生产力总量，改善了生态环境，为经济、环境和社会的和谐发展奠定了基础。图1，表4，参13。

Changes of Vegetation Ecosystem NPP in YUYANG District of Northern Shaanxi

Based on the date about the climate and the land utilization of YUYANG District, choosing some suitable models according to the related research results and the field survey,the we analyzed the changes of the Net Primary Productivity( NPP) of the vegetation ecosystem in Yuyang District during 1988 - 2003.Study has shown: The total NPP value of the vegetation ecosystem was on the rise,and it increased about 7.75% in Yuyang District during 1988 - 2003.The NPP value of the woodland increased about 11.35%, and that of the garden land increased about 1054.99% ,but that of the grassland reduced about 6.15% in Yuyang District during 1988 - 2003.The woodland,the garden land and the grassland contributed 95.56% ,31.82% and - 27.38% of the total increased NPP value in Yuyang District during 1988 - 2003.The structure adjustment of the land utilization increased the total value of the Net Primary Productivity and improved greatly the ecosystem environment of Yuyang District during 1988 - 2003. That established a basis for the harmonious development of economy .environment and society there.