基于Mann-Kendall法的湖泊稳态转换突变分析

采用变化趋势与倾向率、Mann-Kendall趋势检验法和突变点分析法对1981~2008年间太湖湖泊稳态转换关键因子总氮(TN)、总磷(TP)和叶绿素a(Chla)进行突变识别,结果表明,(1)TN、TP和Chla分别在0.05、0.10和0.05水平上呈显著增加趋势;(2)TN浓度在1990~1991年间和1994~1995年间发生了两次突变;TP浓度突变点发生在1987~1988年;Chla浓度历史变化存在三个阶段,1981~1989年为第一阶段,尚未产生突变阶段,第二阶段为1990~1996年,突变过渡阶段,第三阶段为1997~2008年,属于突变后的状态;(3)综合TN、TP和Chla浓度历史变化存在不同阶段,结合各因子的历史变化序列,太湖湖泊稳态转换突变点为1988年和1997年,并把太湖划分为三个阶段,第一阶段为1981~1987年, TP浓度为0.025mg/L,属于草藻共存,接近于清水稳态阶段;第二阶段为1988~1996年, TP浓度为0.086mg/L,属于藻草共存阶段;第三阶段为1997到2008年, TP浓度为0.103mg/L,属于藻型浊水稳态.研究结果表明Mann-Kendall法在湖泊稳态转换突变分析中具有一定的适用性.

Analysis of regime shift in Taihu Lake based on Mann-Kendall method

Basing on the rate of change of trends and tendencies, Mann-Kendall method, total nitrogen (TN)、total phosphorus (TP) and chlorophyll a (Chla) were took as the key factors, and regime shift and mutation were analyzed in Taihu Lake among 1981~2008. The results showed that: (1) Significant increases in TN, TP and Chla were 0.05, 0.10 and 0.05 level respectively; (2) There were two TN mutations from 1990 to 1991 and 1994 to 1995. The TP mutation occurred between 1987 and 1988. Chla changes contained three stages: 1981~1989, the first stage had not yet mutated; 1990~1996: the second was mutation transitional stage; 1997~2008: the third was mutated stage; (3) Considering the mutation and the historical change sequence of TN, TP and Chla, the two mutations of regime shift were 1988 and 1997 in Taihu Lake. The lake regime was divided into three stages in Taihu Lake. The first stage was from 1981 to 1987, in which the TP concentration was 0.025 mg/L and it was called macrophytes-algae coexist stage which was closed to clear water steady state. The second stage was algae-macrophytes coexist state from 1988 to 1996, and the TP concentration was 0.086mg/L. The third stage was algae-dominated turbid water state from 1997 to 2008, and the TP concentration was 0.103mg/L. The results showed that Mann-Kendall method could be used for lake regime shift analysis.