2000-2020年石羊河流域草地净初级生产力时空动态及其对气候的响应

Spatio-temporal dynamics and climate response of grassland net primary productivity in Shiyang River Basin from 2000 to 2020

石羊河流域是河西典型的干旱内陆河流域,其生态本底极为敏感脆弱,探究该地区草地植被净初级生产力(NPP)数量和分布变化及其对气候的响应,对该地区草地管理等具有重要意义。本研究基于草原综合顺序分类系统(CSCS)改进的CASA模型模拟了2000-2020年石羊河流域草地NPP,并辅以Sen’s斜率、变异系数(CV)和Hurst指数探究了NPP时空动态、变化趋势、变化稳定性、未来变化趋势,并通过偏相关分析方法分析了积温和降水与NPP之间的相关关系。结果表明:1)草地年均NPP为170.24 g·(m^(2)·a)^(-1),10年NPP增量为28.96 g·m^(-2),呈波动上升趋势,未来一段时间内NPP还会有所增加。2)草地类中,年均NPP最高的是山地草甸类(ⅡE30),年均548.74 g·(m^(2)·a)^(-1);其次为山地草甸草原类(ⅡD23),年均为454.50 g·(m^(2)·a)^(-1);年均NPP最低的是温带荒漠类(ⅣA4),年均91.65 g·(m^(2)·a)^(-1)。3)石羊河流域草地整体稳定,中波动草地占据主体地位,仅温带典型草原类(ⅢC17)存在较高波动。4)多数草地NPP增加的主导因素是降水,对降水响应敏感的区域占流域面积的24.93%,仅两类荒漠草地(ⅢA3和ⅣA4)对降水响应关系不明显;草甸类草地NPP对积温响应最为敏感,荒漠类草地与积温呈现一定的负相关关系。

The Shiyang River Basin is a typical arid inland river basin in the Hexi river.Its ecological base is sensitive and fragile.Exploring the relationship between the number and distribution of net primary productivity(NPP)and its response to climate is of great significance to grassland management in this area.This study was based on the improved Carnegie-Ames-Stanford approach(CASA)model and the comprehensive and sequential classification system(CSCS)to simulate the grassland NPP in the Shiyang River Basin from 2000 to 2020,supplemented by Sen’s slope,coefficient of variation(CV)and Hurst index.The correlation between accumulated temperature,precipitation,and NPP was analyzed by partial correlation analysis.The results showed that:1)The average annual NPP value of grassland was 170.24 g·(m^(2)·a)^(-1).The NPP increased by 28.96 g·m^(-2) over 10 years,showing a fluctuating upward trend.The NPP will increase further in the future.2)The highest annual NPP of grassland was measured in the mountain meadow(ⅡE30)with an annual NPP value of 548.74 g·(m^(2)·a)^(-1),followed by mountain meadow grassland(ⅡD23)with an annual NPP value of 454.50 g·(m^(2)·a)^(-1).The lowest annual NPP of grassland was measured in the temperate desert(ⅣA4)with an average annual value of 91.65 g·(m^(2)·a)^(-1).3)Overall,the grassland was stable,the grassland with medium fluctuation occupied the prominent position,and only cool temperate-semiarid temperate typical steppe(ⅢC17)had a high fluctuation.4)Precipitation was the dominant factor in increasing NPP in most grasslands in the basin.The area sensitive to precipitation accounts for 24.93%of the basin area.Only two types of desert grassland(ⅢA3 andⅣA4)were not visibly sensitive to precipitation;NPP of meadow grassland was the most sensitive to accumulated temperature.There was a certain negative correlation between desert grassland and accumulated temperature.