呼伦贝尔草原净初级生产力时空变化及气候响应分析

为了定量评估呼伦贝尔草原的生产能力, 明确气候因子对草原生物量累积过程的影响, 利用近18年中分辨率成像光谱仪(MODIS)净初级生产力(NPP)产品(MOD17A2H), 结合同时期气象数据, 基于像元定量分析了呼伦贝尔草原NPP的时空变化规律及其与气候因子的关系。结果表明:2000-2017年呼伦贝尔草原净初级生产力(NPP)均值为306.97 g C·m^-2, 18年来NPP变化呈波动中增加的趋势, 最低值为2001年的241.60 g C·m^-2, 最高值为2014年的372.10 g C·m^-2。NPP高值区(>400 g C·m^-2)分布于低地草甸;中值区(250400 g C·m^-2)分布于山地草甸和温性草甸草原;低值区(<250 g C·m^-2)出现在呼伦贝尔西部的温性草原, 不同草地类型NPP值整体变化趋势表现为:低地草甸>山地草甸>温性草甸草原>沼泽类>温性草原。呼伦贝尔草原NPP与降水的相关性高于与温度的相关性, 降水是NPP积累的主要影响因子, 温性草甸草原和温性草原对气候因子变化的响应总体比低地草甸和山地草甸敏感。

Analysis of spatio-temporal changes and climate-response of net primary production in Hulunbuir grassland

The aim of this research was to quantitatively assess the productivity of Hulunbuir grassland and clarify the impact of climatic factors on the grassland growth processes. Our study used the MOD17A2H dataset and meteorological data to study the temporal and spatial variation of annual net primary productivity (NPP) and the relationship between NPP and climate factors in the grassland of Hulunbuir, China. We found that the annual mean value of NPP in Hulunbuir grassland gradually decreased from northeast to southwest. The average NPP value for the period 2000 to 2017 was 307 g C·m^-2, and the NPP during the 18 years has increased, with the lowest value being 242 g C·m^-2 in 2001, and the highest value being 372 g C·m^-2 in 2014. The high NPP values (>400 g C·m^-2) are mainly distributed in the eastern and western of Daxing'anling mountainous area with grassland type of lowland meadow; the median NPP values (250-400 g C·m^-2) are mainly distributed in the interlaced hills and high plains with grassland types of mountain meadow and temperate meadow steppe; the low NPP values (<250 g C·m^-2) are mainly distributed in southwest Hulunbuir where the grassland is categorized as swamp meadow and temperate steppe. The NPP of different grassland categories ranked in order: lowland meadow>mountain meadow>temperate meadow steppe>swampy meadow>temperate steppe. Climate change is also observed to be a large influence on NPP interannual variation. The correlation between NPP and precipitation is higher than that between NPP and temperature, indicating that precipitation is the more important contribution to NPP variation in Hulunbuir grassland. The response of lowland meadow and mountain meadow to climatic change is less pronounced than that of temperate meadow steppe and temperate steppe.