农牧交错区耕地净第一性生产力动态变化研究——以陕西榆林市榆阳区为例

Study on the dynamic changes of net primary productivity of cultivated land in pasturing-farming region——A case over Yuyang district

以榆林市榆阳区1984-2003年各乡镇的粮食产量统计数据为依据，选用了适合农用地的净第一性生产力估算模型，对该区耕地净第一性生产力单位面积量及总量进行分区动态测算，以揭示生态环境对耕地净第一性生产力的影响。研究表明：（1）1984～2003年间，榆阳区耕地净第一性生产力总量在波动中上升，20a内总物质量从21．94×10^4t／a增加到57．98×10^4t／a，年度递增率为5．24％。（2）在1984-2001年间，擒阳区北部耕地净第一性生产力远高于南部，且呈较快上升趋势，而南部黄土丘陵沟壑区的耕地净第一性生产力呈较平缓的波动变化。且略有下降。（3）在1984-2001年间，榆阳区城区、近郊、远郊的差异性在单位耕地面积净第一性生产力上体现为城区〉近郊〉远郊；在耕地NPP总量方面，城区、近郊和远郊都表现为在波动中上升，三区变化以远郊波动幅度最大。（4）榆阳区耕地净第一性生产力总量的大幅增长有农业投入增加的原因，但主要得益于该区的生态环境的改善。

Based on the grain yield of Yuyang district from 1984 to 2003, the author chosen a suitable model to estimate net primary productivity of cultivated land of different region to research the relation between ecological environment and NPP of cultivated land. The results shown as follows： （1） The total amount of NPP. of cultivated land in Yuyang district generally increased during 1984- 2003. Its total amount has grown fro n 21.94×10^4t/a in 1984 to 57. 98×10^4 t/a in 2003. The annual increasing rate was 5.24%. （2） The unit anamount of NPP of cultivated land in the north was not only much more than that in the south but also increaed fast during 1984-2001. At the same time, the unit area amount of NPP of cultivated land changed little in the south. （3） During 1984-2001, the unit area amount of NPP of cultivated land in urban was the highest and that in suburb fellowed it. The total amount of NPP of cultivated land in urban, suburb and outer suburb of Yuyang district all increased generally, and that in outer suburb fluctuated largestly. （4）The increase of the NPP of cultivated land was partly because of increasing investition in agriculture, but mainly because of ecological environment improvement of Yuyang district.