黄土高原草地净初级生产力时空动态及其影响因素

利用光能利用效率模型(Carnegie-Ames-Stanford approach,CASA)模拟2000-2015年黄土高原草地净初级生产力(NPP),分析黄土高原草地NPP的时空动态、NPP变化稳定性和持续性特征,从植被类型、地形因素、气候变化和人类活动4个方面探讨黄土高原草地NPP的影响因素.结果表明:黄土高原草地NPP的平均值为202.93 g C·m^-2·a^-1,其年际变化特征呈现显著增加的趋势,平均年增加速率为2.43 g C·m^-2·a^-1;分布具有明显的空间异质性,大体呈南高北低的状态.黄土高原草地NPP呈增加趋势的区域占总草地面积的91.2%,主要分布在陕西省的大部分地区、甘肃陇东及陇中地区和青海等地.草地NPP变化较为稳定的区域主要集中在鄂尔多斯的南部地区、陕北地区和甘肃等地.大部分地区草地NPP未来的变化趋势与过去一致,且陕西省的大部分地区以及甘肃省的陇中及陇东地区的草地NPP将呈现持续显著增加的趋势.坡面草地的平均NPP值最高,为703.37 g C·m^-2·a^-1;而高山亚高山草地NPP平均值最低,为57.28 g C·m^-2·a^-1.高海拔地区的草地NPP较高,而平原及丘陵地带草地NPP相对较低.研究期间黄土高原降水量的增加对草地NPP的增加具有明显的促进作用;人类活动诸如过度放牧状况的改善以及退耕还草等政策的实施对黄土高原草地NPP的增加也具有重要作用.

Spatial-temporal dynamics of grassland NPP and its driving factors in the Loess Plateau,China

We estimated grassland NPP using CASA model in the Loess Plateau during 2000-2015 and further analyzed the spatiotemporal dynamics, stability and persistence of grassland NPP. The driving factors of grassland NPP were analyzed from four aspects, i.e., vegetation types, topographic factors, climate change, and human activities. The results showed that the average NPP was 202.93 g C·m^-2·a^-1. The grassland NPP showed an increasing trend with an average increase rate of 2.43 g C·m^-2·a^-1. The distribution of NPP in grassland had obvious spatial heterogeneity, which was generally high in the south and low in the north. 91.2% of the total grassland area showed an increasing trend, mainly distributed in most areas of Shaanxi Province, Longdong and Longzhong areas of Gansu Province, and most parts of Qinghai Province. The regions with a stable growth condition of grassland NPP mainly located in the south of Ordos, northern Shaanxi, and Gansu. The future change trend of grassland NPP would be consistent with that of the past in most areas. The grassland NPP would continue to increase in most areas of Shaanxi Province, Longzhong and Longdong areas in Gansu Province. The average NPP of slope grassland was 703.37 g C·m^-2·a^-1, while that of alpine and subalpine grassland was 57.28 g C·m^-2·a^-1. The grassland NPP was higher in high altitude area and relative low in plain and hilly area. The increased precipitation promoted the increase of grassland NPP during the study period. Human activities such as improvement of overgrazing and returning cropland to grassland also played an important role in the increase of grassland NPP in the Loess Plateau.