2000—2015年陕西植被净初级生产力时空分布特征及其驱动因素

Spatial-temporal distribution of vegetation net primary productivity and its driving factors from 2000 to 2015 in Shaanxi,China

利用MOD17A3 NPP时间序列数据、地表覆盖类型数据、气象数据、MOD16蒸散产品、地形数据等,分析2000—2015年陕西省植被净初级生产力(NPP)时空变异特征,探讨NPP的时空变异对各影响因素的响应特征.结果表明:研究期间,陕西植被NPP整体呈极显著上升趋势,NPP变化趋势线斜率为5.02 g C·m^(-2)·a^(-1).NPP年平均值为344 g C·m^(-2)·a^(-1),变化范围为247~390 g C·m^(-2)·a^(-1).陕西NPP显著增加的区域占全省国土面积的61.2%,主要分布在陕北、渭北地区和秦巴山地西部;显著减少的区域主要分布在西安市、宝鸡市等城市周边区域,仅占2.5%.陕西年平均气温和年降水量变化趋势均不显著,气温呈现不显著升高,降水呈现不显著降低,具有暖干化趋势.NPP与降水量、平均气温显著相关的区域分别占全省总面积的9.4%和1.5%.由于人类活动的频繁干预大大降低了气候环境对NPP变化的影响程度,人类活动逐渐成为影响NPP变化的主导因素.陕北、关中地区的NPP与蒸散显著相关,随着植被NPP的增加,势必对这些地区水平衡造成重大影响.各土地覆盖类型NPP平均值为耕地>林地>草地>园地,NPP增加速率为园地>草地>林地>耕地,NPP变化百分率为草地>园地>林地>耕地.研究区内坡度0°~5°、5°~25°和>25°区域的NPP增长百分率分别为14.6%、25.7%和35.9%.

Using MOD17 A3 NPP time series data,surface cover type data,weather data,MOD16 evapotranspiration products and terrain data,the temporal and spatial variability of vegetation net primary productivity（ NPP） in Shaanxi Province from 2000 to 2015 was analyzed,and its response to each influencing factor were discussed. The results showed that the NPP of Shaanxi had a significant upward trend in the past 16 years with a slope of 5.02 g C·m^-2·a^-1. The annual average of NPP was 344 g C·m^-2·a^-1 with a range from 247 to 390 g C·m^-2·a^-1. The NPP at 61.2% area of Shaanxi Province showed a significant increasing trend,which were mainly distributed at northern part of Shaanxi,Weibei area and western part of Qinba Mountain. There was a decrease trend of NPP for the area around Xi＇an and Baoji City,accounting for only 2. 5% of the whole province.During the study period,the variation of annual mean temperature and annual precipitation in Shaanxi showed no significance. The temperature showed a increase trend and the precipitation showed a decrease trend,implying a drier and warmer climate trend in Shaanxi Province. The areas with significant correlation between NPP and precipitation and temperature accounted for 9.4% and1.5% of the total area of the province. The frequent intervention of human activities reduced the impact of climate on the changes of NPP,so human activity had gradually become the dominant factor. NPP in northern Shaanxi and Guanzhong areas was significantly correlated with evapotranspiration. The increases of NPP in these areas would have great influence on the water and heat balance.The average NPP at different land cover was farmland 〉forestland〉 grassland 〉garden,increasing rate of NPP at different land cover was garden 〉grassland 〉forestland〉 farmland,and proportional changes of NPP was grassland〉 garden〉 forestland〉 farmland. The increasing percentage of NPP at three gradient ranges were 14. 6%（ 0°-5°）,25. 7%（ 5°-25°） and 35. 9%（ 25°）,respectively.