麦蚜和寄生蜂对农业景观格局的响应及其关键景观因子分析

大量研究表明多样性的农业景观格局能够影响蚜虫及寄生蜂的分布。本文利用并设计了两种尺度的麦田农业景观格局,依据麦蚜种群发生特点,分为迁入期、增长期与高峰期三个时期,论述了不同尺度下农业景观元素对麦蚜及寄生蜂系统的影响,通过逐步回归筛选了不同时期麦蚜及寄生蜂分布的关键景观元素,最后通过CANOCO软件模拟了麦蚜及寄生蜂的分布排序格局。结果表明不同景观因子对麦蚜及寄生蜂种群影响不同,迁入期两种尺度下裸地最有利于两种有翅蚜的迁飞入田,塑料大棚对有翅蚜种群的入田有抑制作用。增长期草地与林地生境对麦蚜种群增长率促进最大,塑料大棚同样抑制了麦蚜的种群增长率；但塑料大棚、草地与林地对蚜茧蜂的种群增长率有促进作用,非麦类作物生境对蚜茧蜂种群增长率抑制作用最大；草地与林地有利于重寄生蜂的种群增长率；高峰期裸地比例大的农业景观下麦蚜的最大种群密度较大,草地与林地对蚜茧蜂与重寄生蜂的最大种群密度均有促进作用。两种尺度下的研究结果一致。不同麦物种的对不同景观元素反应与形态学与生活史特征有关,而且景观结构中特定的植物种类、非作物植物的密度与物候期都可能影响寄生蜂群落的多样性与功能。

Effects of landscape structure and key landscape factors on aphids-parasitoids- hyper parasitoids populations in wheat fields

Several studies have shown that multiple agricultural structures could affect dynamics and distribution of aphids, parasitoids and hyper parasitoids system. In this article, we designed two spatial scales of agricultural structure. The affects of different agricultural landscape factors for wheat aphids, parasitoids and hyper parasitoids in two spatial scales were analyzed and discussed. Through stepwise regression methods, we screened the key landscape factors in two spatial scales which influenced wheat aphids, parasitoids and hyper parasitoids respectively in different populations periods. Then we stimulated distribution and sequence of wheat aphid, parasitoids and hyperparasitoids by CANOCO software. The influence of landscape matrix and composition of surrounding landscapes on the abundance of aphids, parasitoids and hyper parasitoids were studied in wheat fields in Ningxia Province, P. R. China. Wheat aphids, parasitoids, hyper parasitoids and seven landscape factors (wheat fields, non-wheat crop fields, grassland, tree lands, bare area, plastic house, and other lands) in 95 fields over a two year periods (2009-2010). The composition and patchiness of the surrounding landscape were determined from high altitude photographs. Seven landscape variables, aggregated at two spatial scales ranging from 31400 m2 to 125600 m2, were measured from aerial photographs. Regression models incorporating within-field and seven landscape factors accounted for 37-58% of the variance in aphids, parasitoids and hyperparasitoids abundance in wheat fields. Result showed that different landscape factors had a different effects for dynamics and distribution of aphids, parasitoids and hyperparasitoids. In immigration periods, bare area could greatly enhance the immigration numbers of two wheat aphids. But plastic house sharply decreased the immigration number greatly. In growth periods, grassland and tree lands accelerated the population growth rate of two aphids species. Plastic house also suppressed the population growth rate of aphids. On the contrary, plastic houses, grassland and tree lands accelerated the population growth rate of parasitoids (aphidiidae), which was restrained greatly by non-wheat crop habitat. Grassland and tree lands were in favor of the population growth rate of hyperparasitoids. In stable periods, the max population density was highest in agricultural landscape which had a great percent of bare area. Both grassland and tree lands could increased the max population density of parasitoids and hyperparasitoids. The results in two spatial scales were similar. Overall, parasitoids and hyperparasitoids abundance, species and species diversity increased with increasing bare area in wheat fields and with increasing amounts of non-cultivated lands and increasing patchness in the surrounding landscape. The differential response of these parasotoids and hyperparasotoids to landscape factors was discussed in relation to differences in mophological and life history characteristics. The specfic composition of parasitoid and hyperparasitoid assemblaged could signficantly alter parasitism at different agricultural landscape composition. Future studies should evaluate more special plants in landscape, non-crop herbiove densities and span more years to fully understand the impact of agricultural landscapes on diversity and function parasitoid and hyperparasitoid. The core aims were the construction and design of agricultural structure in successive spatial-temporal scale, which enhanced activity and predation of natural enemies in agricultural landscape, and suppressed the pest population to the greatest extent.