植被是生态环境变化的指示器,分析植被物候的时空变化特征及其影响因素对分析陆地生态系统的碳、水和能量平衡具有重要意义.该文利用MOD13Q1 EVI数据集,采用D-L拟合法和动态阈值法提取了北京市 2001-2020 年植被生长季开始期(start of season,SOS)、植被生长季长度(growing season length,GSL)和植被生长季结束期(end of season,EOS).通过构建城乡梯度带,分析了北京市城乡区域植被物候的时空变化特征.利用回归分析和趋势分析方法探讨了植被物候参数对气温、降水、日照、风速等气候因子以及城市热岛强度和城市化影响因子的响应.研究表明:2001-2020 年间北京市植被物候呈现出SOS提前、GSL延长和EOS推迟的趋势.林地和灌木的SOS比草地早,EOS较草地晚,说明木本植物生长季开始期早,结束期晚.通过分析气候因子与物候之间的关系发现气温、降水、日照和风速都对北京市植被物候有一定的影响,其中SOS对日照的变化最为敏感,EOS对风速的变化最为敏感.植被物候沿城区—郊区—农村方向呈现明显的梯度变化,城区SOS比农村平均提前 12.2 d、EOS平均推迟 18.9 d.城市夜晚热岛强度与SOS在城乡梯度带上具有显著相关性(p＜0.01),SOS,GSL和EOS与人口密度、城市建成区面积、地均GDP均存在显著相关关系(p＜0.01),说明城市化发展对北京市SOS提前、GSL延长和EOS推迟具有重要作用.
Analysis of the spatio-temporal variations in vegetation phenology in Beijing based on MODIS time series data
Vegetation can indicate the changes in ecological environments.Analyzing the spatio-temporal variations and influencing factors of vegetation phenology holds critical significance for exploring the carbon,water,and energy balance of terrestrial ecosystems.In this study,the MOD13Q1 EVI dataset was employed to extract the start of season(SOS),the growing season length(GSL),and the end of season(EOS)for vegetation in Beijing from 2001 to 2020 using the double logistic(D-L)function fitting method and the dynamic threshold method.The spatio-temporal variations of vegetation phenology in urban and rural areas of Beijing were analyzed by constructing an urban-rural gradient zone.The response of vegetation phenological parameters to climate factors like temperature,precipitation,sunshine,and wind speed,as well as urban heat island intensity and urbanization,was investigated through regression and trend analyses.The results show that from 2001 to 2020,the vegetation phenology of Beijing manifested a trend of earlier SOS,extended GSL,and delayed EOS.Compared to grassland,woodland and shrubs manifested earlier SOS and later EOS,suggesting that the phenology of woody plants started earlier and ended later.As revealed by the relationship between climate factors and phenology,temperature,precipitation,sunshine,and wind speed all displayed certain effects on vegetation phenology in Beijing,with SOS and EOS being the most sensitive to sunshine and wind speed,respectively.The vegetation phenology was characterized by a significant gradient change along the urban-suburban-rural direction.Compared to the rural area,the urban area showed SOS 12.2 d earlier and EOS 18.9 d later on average.The urban nighttime heat island intensity was significantly correlated with the SOS of vegetation in the urban-rural gradient zone(p＜0.01).Moreover,the SOS,GSL,and EOS were significantly linearly correlated with population density,urban built-up area,and GDP per square kilometer of land(p＜0.01).Therefore,urbanization played a significant role in advancing SOS,extending GSL,and delaying EOS of vegetation phenology in Beijing.
vegetation phenologyclimate changeurbanizationurban heat island effect
万方数据
维普
