福州市中心城区植被覆盖度的时空演变及其驱动因素

Spatio-temporal Evolution and Driving Factors Analysis of Fractional Vegetation Coverage in Central Urban Area of Fuzhou City

以福州市中心城区为研究区域、植被覆盖度为研究对象,采用等间距法将植被覆盖度(取值范围为0~1)划分为低、中低、中、中高、高5个等级;选取11个与植被覆盖度时空动态变化密切相关的气候、地形地貌、人类活动等影响因素(地貌类型、高程、坡度、坡向、植被类型、夜间灯光、国内生产总值(GDP)密度、年降水量、年均温、人口密度、土地利用类型),以相关官网的植被覆盖度及各影响因素数据为基础,采用趋势分析法、变异系数、赫斯特(Hurst)指数、地理探测器,分析2002—2021年福州市中心城区植被覆盖度时空演变特征、量化11个影响因素对植被覆盖度空间分布的影响和不同影响因素协同作用的影响。结果表明:①植被覆盖度随时间的变化,2002—2021年福州市中心城区植被覆盖度总体呈显著降低趋势,变化率为0.0011·a^(-1)(P<0.05),其中2002—2014年显著降低(P<0.05),但2014—2021年变化趋势不显著;各等级植被覆盖度变化差异显著,中低、高的植被覆盖度面积占比分别减少了0.13%、10.67%;低、中、中高的植被覆盖度面积占比呈增加趋势,增加幅度分别为0.03%、7.26%、3.51%。②植被覆盖度在空间方面的差异,总体呈现北低南高的空间格局,空间变异系数均值为0.083,以低波动为主(占比高达67.8%),保持稳定的区域面积占比最多(占比40.9%);在未来一段时间,改善的区域面积大于退化面积,其中改善部分以未来改善为主(占总面积的43.11%)。③地理探测器的探测结果表明,2002年夜间灯光影响力最高(分异决定力为0.473),其余年份均为土地利用类型影响力最高(分异决定力均值为0.573);交互探测显示,土地利用类型与夜间灯光的协同作用,在2002—2021年对植被覆盖度空间分布的影响力均为最强,分异决定力均值达到0.659以上。④综合研究结果,福州市中心城区植被覆盖度整体良好,呈现总体下降的趋势,但在2014年出现拐点,未来存在上升趋势,植被覆盖度总体呈现北高南低的分布格局;土地利用类型、夜间灯光,是影响植被覆盖度空间分布的主导因素。

In the central urban area of Fuzhou City,we focused on Fractional Vegetation Coverage and divides it into five levels(low,low-medium,medium,medium-high,and high)using an equal interval method,with values ranging from 0 to 1.Eleven factors closely related to the spatio-temporal dynamics of Fractional Vegetation Coverage,including climate,topography and human activities,are selected(landform type,elevation,slope,aspect,vegetation type,nighttime lights,GDP density,annual precipitation,annual average temperature,population density,and land use type).Based on the data of Fractional Vegetation Coverage and the aforementioned factors from relevant official websites,trend analysis,coefficient of variation,Hurst index,and geodetector are employed to analyze the spatiotemporal evolution of Fractional Vegetation Coverage in the central urban area of Fuzhou City from 2002 to 2021,quantify the impact of the 11 influencing factors on the spatial distribution of Fractional Vegetation Coverage,and examine the synergistic effects of different influencing factors.The results indicate the following:(1)From 2002 to 2021,the overall vegetation coverage in the central urban area of Fuzhou City showed a significant decreasing trend,with a rate of change of 0.0011·a^(-1)(P<0.05).The decrease in Fractional Vegetation Coverage was significant from 2002 to 2014(P<0.05),but the trend was not significant from 2014 to 2021.There were significant differences in vegetation coverage changes among different levels.The proportion of low and high Fractional Vegetation Coverage areas decreased by 0.13%and 10.67%,respectively.However,the proportions of low,medium,and medium-high Fractional Vegetation Coverage areas showed an increasing trend,with increases of 0.03%,7.26%,and 3.51%,respectively.(2)The spatial pattern of Fractional Vegetation Coverage in the central urban area of Fuzhou City generally showed a north-south gradient,with a spatial variation coefficient mean value of 0.083.The majority of areas exhibited low volatility(67.8%of the total)and maintained stability(40.9%of the total).In the future,the area with Fractional Vegetation Coverage improvement is expected to be larger than the area with degradation,with the improvement portion accounting for 43.11%of the total area.(3)The results of the geographic detector analysis revealed that nighttime lights had the highest influence in 2002,with a differentiation power of 0.473.For the other years,land use type had the highest influence,with an average differentiation power of 0.573.The interactive detection showed that the synergistic effects of land use type and nighttime lights had the strongest influence on the spatial distribution of Fractional Vegetation Coverage from 2002 to 2021,with an average differentiation power of above 0.659.(4)Overall,the Fractional Vegetation Coverage in the central urban area of Fuzhou City is good but showed a declining trend,with a turning point in 2014 and a future upward trend.The distribution pattern of Fractional Vegetation Coverage is generally higher in the north and lower in the south.Land use type and nighttime lights were identified as the dominant factors influencing the spatial distribution of Fractional Vegetation Coverage.