摘要:分析北部湾南流江流域净初级生产力时空动态变化特征及其驱动机制，为该区域生态环境保护及应对气候变化提供科学依据。基于光能利用率模型（CASA），利用遥感数据、气象数据和植被类型数据估算了研究区2000-2015年流域的净初级生产力（NPP），借助于Theil-Sen趋势、Mann-Kendall检验以及Hurst指数等数理统计方法对研究区NPP的时空变化特征、未来趋势及其驱动因素进行了定量化分析。结果表明：①时间尺度上，流域NPP总体上呈现出波动上升趋势，增速为44.03 g C m^-2（10 a）^-1，快于广西自治区，上游和下游地区NPP快于全区，而中游地区慢于全区；②空间尺度上，流域NPP的分布规律表现出明显的地域分异，中游最高（1098.99 g C/m²），下游次之（1041.71 g C/m²），而上游最小（1013.22 g C/m²）。NPP的Sen趋势度介于-77.10-74.80 g C m^-2 a^-1之间，在空间上呈现出增加的趋势。③空间波动性上，流域NPP的变异系数较大，其值介于0.01-0.71，其中洪潮江水库、小江水库周边以及玉林市的城乡建设用地扩张区域处于高波动状态，而流域中部的六万大山以及五皇山地带则处于低波动状态；④未来变化趋势上，流域NPP的Hurst指数范围介于0-0.99之间，平均值为0.70，呈现单峰右偏分布，预示着流域NPP未来处于持续性增加的趋势；⑤驱动机制上，流域NPP与多年平均气温呈正相关关系，与年均降水量呈负相关关系，气温是该流域植被NPP的主控因子。由耕地转化为建设用地所导致的NPP损失值最大，其值达到4715.62 t/a，而草地转换为建设用地导致NPP损失值最小，其值仅为184.63 t/a。



Abstract:By analyzing the spatiotemporal dynamic characteristics of net primary productivity and its driving mechanism in the Nanliu River basin of the Beibu Gulf, the goal of this study was to provide a scientific basis for the protection of the ecological environment and the response to climate change in the region. Based on the light energy utilization model (CASA), the net primary productivity (NPP) of the Nanliu River basin in the Beibu Gulf from 2000 to 2015 was estimated using remote sensing data, meteorological data, and vegetation type data. The spatiotemporal variation characteristics, the future trend of NPP and its driving factors in the study area were analyzed with the aid of mathematical statistics, such as the Theil-Sen trend, Mann Kendall test, and Hurst index. The results indicated:(1) Regarding temporal variation, the annual average NPP increased with a fluctuation in the study area from 2000 to 2015, with a growth rate of 44.03 g C m^-2 (10 a)^-1, which is faster than that of the Guangxi autonomous region. The annual average NPP in the upstream and downstream of the river basin was faster than that of the entire region, whereas that in the middle reaches was slower than that of the entire region. (2) Regarding spatial distribution, the distribution law of NPP showed obvious regional differentiation, with the net primary productivity of vegetation in the middle reaches being the highest (1098.99 g C/m²), followed by that downstream (1041.71 g C/m²), and that upstream smallest (1013.22 g C/m²). The Sen trend of NPP was from -77.10 to 74.80 g C/m², and the net primary productivity of the basin showed an increasing trend. (3) Regarding the volatility of NPP, the CV of NPP was larger, being from 0.01 to 0.39. The expansion area of urban and rural construction land around the Hongchao River reservoir, Xiaojiang reservoir, and Yulin City was in a state of high fluctuation, whereas the Liuwandashan mountain in the middle of the basin and in the the Wuhuang mountain belt were in a state of low fluctuation. (4) Regarding the future trend of NPP, the NPP value of the Hurst index was from 0 to 0.99, with a mean of 0.70, and it presented a right unimodal distribution, which indicated that the overall NPP would take on a continuously increasing trend in the future. (5) Regarding the driving mechanism, the watershed NPP had a significant positive correlation with the annual average precipitation, and had a non-significant negative correlation with the annual average temperature, indicating that precipitation was the main climatic factor affecting the vegetation NPP in this basin. The value of NPP loss caused by conversion from cultivated land to construction land was maximal, and its value was 4715.62 t/a. The conversion of grassland to construction land will lead to a minimum value of NPP loss, being only 184.63 t/a.





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