中文摘要：

数据源、时间范围、空间尺度等的差异导致许多物候变化对陆地生态系统碳收支影响的研究缺少可比性。该文基于4级碳通量填充数据,采用相对阈值方法提取了两个北美典型温带阔叶林站Harvard Forest（HF）和University of Michigan Biological Station（UMBS）共20年的物候参数（返青期、枯黄期和生长季长度）,并研究了物候变化对生态系统生产力的影响。结果表明：1）生长季长度的延长对年累积总初级生产力（GPP）有显著贡献,但由于呼吸作用（RE）的干扰,生长季长度变化对年净生态系统生产力（NEP）的影响并不显著;2）返青期的提前对上半年生态系统总初级生产力的贡献最为显著,二者的相关系数分别为0.76（HF）和0.93（UMBS）;3）枯黄期的延迟对生产力的影响并不显著;4）随着春季返青期的提前或秋季枯黄期的延迟,上、下半年GPP和RE的累积量虽均有增加趋势,但由于各自增加的幅度不确定,导致年NEP与二者的响应关系复杂。

英文摘要：

Aims Results of effects of phenological change on terrestrial ecosystem carbon budgets almost always lack comparability because of differences in data sources and time and spatial scales.Our objective was to determine how phenological change effects ecosystem productivity by analyzing annual phenological change of two deciduous broad-leaved forests in North America based on four-class carbon flux data.Methods We designed a relative threshold method to extract the phenological parameters,including start of growing season（SOS）,end of growing season（EOS） and growing season length（GSL） from four-class carbon flux data.The phenological parameters were linked to ecosystem productivity of North American deciduous broad-leaved forests（DBF） at Harvard Forest and the University of Michigan Biological Station.Important findings Prolonged GSL influences annual gross primary productivity（GPP）,but not net ecosystem productivity（NEP） due to disturbance of ecosystem respiration（RE）.Advanced SOS has the most significant influence on the first half year＇s GPP,with a correlation coefficient of 0.76 at Harvard Forest and 0.93 at the University of Michigan.Delayed EOS has little influence on annual GPP and NEP.Although increases of GPP and RE were observed with advanced SOS or delayed EOS,the relationship between phenology and NEP remains complicated due to the uncertainty of RE.