我国草地螟发生间歇期的区域格局变化

2010—2016年我国草地螟一直维持总体轻发态势。为从长时间序列上分析连续轻发年份的历史地位,以1979年以来第2、3个暴发周期及其之间的间歇期为对照,分析了2010—2016年草地螟连续轻发的特点,即全国种群规模维持在历史低位,西北地区发生面积和比率加大,发生区域向西部缩减,提示我国草地螟种群发生已进入间歇期。分析了1979—2016年时间序列上华北、东北、西北3个地区的发生情况对全国的影响,结果表明:(1)华北地区、东北地区的发生面积自然对数值与全国发生面积自然对数值呈极显著的线性正相关,即华北、东北地区与全国发生趋势的年际波动完全一致;(2)西北地区发生面积自然对数值与全国的线性相关性达显著水平,但在不同的历史阶段西北地区与全国的波动趋势有明显差别;(3)自第3个暴发周期的2005年以后,西北地区的波动曲线逐渐与全国趋同,推测这一变化与新疆种群的建立和发展有关。

The regional pattern of Loxostege sticticalis L. varied during a new occurrence intermission in China

In China, the occurrence trend of the meadow moth Loxostege sticticalis L. remained low during the period 2010-2016. In order to reveal the historical status of these low-occurrence years, we analyzed the temporal and spatial characteristics of this new period, using second and third outbreak periods (1979-1985 and 1996-2009) and the intermission between them (1986-1995) as controls. Our results indicated that the new occurrence period (2010-2016) showed the same characteristics as intermission period by significance analysis of difference among four periods. (1) On comparison of the annual occurrence area in China among the four periods, we detected no significant difference between the 2010-2016 and 1986-1995 period, whereas there was a significant difference between these two periods and the other two outbreak periods. (2) On comparison of the annual occurrence areas in North China (NC), Northeast China (NEC), and Northwest China (NWC) among the four periods, we found that NC and NEC showed the same trend as the whole country, as the annual mean occurrence area in the 1996-2009 and 1979-1985 periods was significantly higher than that in the 1986-1995 and 2010-2016 periods. However, NWC showed obvious inconsistencies with the whole country, as its annual mean occurrence area was highest in the 2010-2016 period, moderate in the 1996-2009 and 1979-1985 periods, and lowest in the 1986-1995 period. (3) On comparison of the annual occurrence ratios of NC, NEC, and NWC with that in the whole country among the four periods, we found that NC sustained a considerably high occurrence ratio in each period, although the differences were not significant. Furthermore, the occurrence ratio of NEC in the 1996-2009 period was significantly higher than that in the 1986-1995 and 2010-2016 periods, and the occurrence ratio of NWC in the 2010-2016 period was significantly higher than that in the other three periods. The analysis of annual occurrence regions (counties) and the ratio of NC, NEC and NWC in 2010-2016 compared with 2006 (low occurrence) and 2009 (high occurrence), revealed a northwestward reduction in the occurrence distribution during the new period. These results indicated that the meadow moth had already entered a new intermission period after 2010 in China. In the time period from 1979 to 2016, the correlations of occurrence in NC, NEC and NWC with that in the whole of China were individually analyzed. The results obtained were as follows. (1) The natural logarithm (ln) of the occurrence area in NC and NEC was positively correlated with that of the whole China, showing the same fluctuating pattern in annual dynamics. (2) The ln of the occurrence area in NWC was also positively correlated with that of the whole China, but showed different fluctuations during some periods. (3) Since 2005, the fluctuation in NWC occurrence has gradually approached that of the whole China, which was deduced in connection with the establishment and development of a population in Xinjiang.