不同农业景观结构对麦蚜种群动态的影响

研究表明农业景观结构的复杂性与害虫种群发生强度关系密切,然而在不同农业景观结构下研究麦蚜的发生、种群及寄生蜂的变化还不多。设计了不同的麦田景观结构,调查研究了不同麦田景观结构对麦蚜种群的影响。在简单与复杂两种农业景观结构下,分析了不同种类麦蚜的入田时间、入田量、种群增长率、种群密度及寄生性天敌的多样性与寄生率。结果表明:景观结构对不同种类麦蚜影响不同,但复杂农业景观下麦蚜迁飞入田时间都要晚于简单农业景观(连片种植)下的入田时间,复杂农业景观下有翅蚜的迁入量显著低于简单景观下有翅蚜的迁入量,并且复杂农业景观下麦蚜种群增长速率高于简单农业景观下的增长速率。不同种类麦蚜对景观结构的不同反应可能与形态学与生活史特征有关,两种不同农业景观结构下寄生性天敌的多样性与寄生率无显著差异。复杂景观结构下的麦蚜有翅蚜低的迁入量、高的增长速率可能与生境高度破碎化有关,其中与温室大棚塑料白色反光有的很大的影响。生境破碎化影响了麦蚜对寄主植物寻找以及天敌对猎物的寻找效应。

Population dynamics of wheat aphids in different agricultural landscapes

Habitat destruction and fragmentation remain major influences of biodiversity loss due mainly to anthropogenic disturbance, e.g. the expansion and intensification of modern agriculture. Designing a robust and sensitive landscape that can sustain a viable population has become a priority in conservation. Several studies have gathered negative responses regarding pest populations to landscape complexity, but articles about wheat aphid dynamics in different agricultural landscapes are rare. In agro-ecosystems, landscape structure may alter the assemblage of insects, such as phytophagy (aphids) and parasitoids (aphidiidae), potentially affected intraguild interactions. In this article, two different agricultural landscapes were designed; three species of wheat aphids, parasitism and diversity of parasitoids of wheat aphids were collected and studied. Time of immigration, individuals of immigration, population growth rate, population density, diversity and parasitism of parasitoids were recorded and analyzed in two different agricultural landscapes. According to population dynamics of wheat aphids and parasitoids, we divided population dynamics into three different periods: immigration periods (May 2-May 15), growth periods (May 16-May 30), and stable periods (May 30-June 20). The results showed that different agricultural landscapes affected different species respectively. For example, the time of immigration in simple agricultural landscapes was 5-7d earlier than that in complex agricultural landscapes; the individuals of immigration in complex agricultural landscapes were less than simple agricultural landscapes; and the population growth rates in complex agricultural landscapes were higher than simple agricultural landscapes. The population growth rates of wheat aphids in complex and simple agricultural landscapes were 39.43±11.84 and 13.73±7.49 respectively in growth periods, three species of wheat aphids behaved the similar tendency. Our study also suggested that the differences of diversity and parasitism of parasitoids in different agricultural landscapes made no significances. The diversity indices of parasitoids and parasitism were 2.65±0.58 and (28.76±13.09)% respectively in complex agricultural landscapes, comparing to 3.24±0.37 and (48.32±18.61)% respectively in simple agricultural landscapes in growth periods. We got the similar results by comparing and analyzing the experiment results in stable periods. The diversity indices of parasitoids and parasitism were 2.94±0.65 and (38.54±8.92)% respectively in complex agricultural landscapes, comparing to 3.73±0.48 and (61.29±12.43)% respectively in simple agricultural landscapes. It appeared that the different responses of different species were related to taxonomy and life characteristics. The lower individuals of immigration and higher growth rate in complex agricultural landscapes could be related to higher habitat fragmentation in complex agricultural landscape. We concluded that habitat fragmentation might affect the search of wheat aphids for host plants and natural enemies for prey. The lower individuals of immigration and higher growth rate in complex agricultural landscape were related to higher habitat fragmentation in complex agricultural landscape. Habitat fragmentation effected the rearch of wheat aphids to host plant and natural enemies to prey. The strong reflection of flim may disturb the immigration of wheat aphids and action of natural enemies. The max population density of wheat aphids in complex and simple agricultural landscapes were 821.65±66.56 and 677.81±32.98 respectively. Our research also found that landscape structure had the same affects on Macrosiphum avenae (F.) and Rhopalosiphum padi (L.), but had different affects on Schizaphis graminum (Rond). The analysis results also suggested that the host-parasitoid interactions worked only at certain spatial scales (patch sizes), which not only coincides with the general conclusion from spatial ecology but also enables us to conduct successful biological control without encountering the environmental risk of pesticide. The application of this scale-dependence of host-parasitoid interaction, together with providing heterogeneous and refugee habitat for the natural enemies of pests, could beget efficient pest control in agricultural land. The focus of most habitat management research has been on understanding the role of these plant-provided resources to natural enemies biologically and ecologically, and their ability to enhance suppression of pest populations. The core technology in this study was the construction and design of agricultural structure in successive spatial-temporal scales, which enhanced activity and predation of natural enemies in agricultural landscapes and suppressed the pest population to a greatest extent.