新疆草原马铃薯鳃金龟幼虫的空间分布型及其与微地形的关系

Relationship between microtopography and spatial distribution patterns of summer chafer Amphimallon solstitiale(L.)in Xinjiang grasslands

为明确新疆草原的重要害虫马铃薯鳃金龟Amphimallon solstitiale(L.)在不同微地形的分布特征,采用棋盘式取样法在伊犁草原不同微地形区域进行取样,统计其中的马铃薯鳃金龟幼虫数量,利用9种聚集度指标(扩散系数C、丛生系数I、扩散型指数I_(δ)、负二项分布K值、久野指数CA、平均拥挤度m^(*)、聚块性指数m^(*)/m、L_(α)指标和Z指标)和2种回归模型(Iwao m^(*)-m回归模型和Taylor幂法则模型)分析幼虫的空间分布类型,通过聚集均数λ分析其聚集原因,并利用Iwao理论抽样数模型和Kuno序贯抽样模型提出抽样调查技术。结果显示:马铃薯鳃金龟幼虫的平均虫口密度随着伊犁草原地势的升高而降低,且9种聚集度指标和Taylor幂法则模型均表明马铃薯鳃金龟幼虫的空间分布型属于聚集分布。微地形对聚集度指标表征的聚集程度和Iwao m^(*)-m回归模型拟合结果存在影响,其中C、I、m^(*)、L_(α)和Z显示马铃薯鳃金龟幼虫聚集程度均随地势的升高而逐渐降低,K、CA、m^(*)/m和I_(δ)显示幼虫聚集程度均随地势的升高呈先升高后降低的趋势;位于平地和坡麓的马铃薯鳃金龟幼虫经Iwao m^(*)-m回归模型拟合呈均匀分布。由λ值可知马铃薯鳃金龟幼虫在4种微地形的聚集行为均由外部因素导致。基于马铃薯鳃金龟幼虫数量建立了Iwao理论抽样数模型和Kuno序贯抽样模型并得到理论抽样数和临界累计虫量,当允许误差为0.2时,平均虫口密度为6头/0.09 m^(2)的理论抽样数为49个样方;在允许误差为0.2时调查40个样方,临界累计虫量为33.22头。表明马铃薯鳃金龟幼虫在伊犁草原的空间分布型为聚集分布,微地形会影响其发生密度,但并不影响其空间分布类型。

To clarify the spatial distribution pattern of the significant pest summer chafer Amphimallon solstitiale(L.)in different microtopographies of the Xinjiang grasslands,the checkerboard sampling method was employed to sample different microtopographic regions of the Yili grasslands.The number of A.solstitiale larvae was recorded,and their spatial distribution patterns were analyzed by using nine aggregation indices(the diffusion coefficient C,clumping index I,diffusivity index I_(δ),negative binomi-al distribution index K,Cassie index CA,mean crowding m^(*),patchiness index m^(*)/m,L_(α)index,and Z in-dex)along with two regression models(the Iwao m^(*)-m regression model and Taylor’s power law).The cause of aggregation was analyzed using the aggregation meanλ,and a sampling technique was estab-lished based on Iwao’s theoretical sampling number model and Kuno sequential sampling model.The results showed that the population density of A.solstitiale larvae diminished as the elevation increased in the Yili grasslands.Nine aggregation indexes and Taylor’s power law suggested that A.solstitiale lar-vae followed an aggregated distribution pattern.Microtopography influenced the level of aggregation represented by aggregation indices and Iwao m^(*)-m regression model;for example,the degree of aggre-gation for five aggregation indices(C,I,m^(*),L_(α),and Z)tended to decrease as the elevation increased.In contrast,the four aggregation indices,K,CA,m^(*)/m,and I_(δ),showed that the degree of aggregation of the larvae initially rose and then fell with rising elevation.Larvae in the plains and toe slopes showed a uni-form distribution pattern according to the Iwao m^(*)-m regression model.The aggregation meanλindicat-ed that the aggregation behavior of A.solstitiale larvae in the four microtopographies was caused by ex-ternal factors.Based on the number of A.solstitiale larvae,Iwao’s theoretical sampling number model and Kuno’s sequential sampling model were established to obtain the theoretical sampling number and the critical cumulative number of larvae.When the permissible error D was 0.2 and the population den-sity was 6 larvae/0.09 m^(2),the theoretical sampling number was 49 sample squares;when the permissi-ble error D was 0.2 and 40 sample squares were investigated,the critical cumulative population was 33.22 larvae.The findings indicated that the spatial distribution type of A.solstitiale larvae in Yili grass-lands followed an aggregated distribution pattern.While microtopography influenced population densi-ty,it did not alter the spatial distribution pattern.