农业景观生物多样性与害虫生态控制

Biological diversity in support of ecologically-based pest management at landscape level

现代农业的一个重要特征就是人类对农田生态系统的干扰强度及频率不断增加,严重影响农业景观的结构及其生物多样性。农业景观结构的变化及其生物多样性的丧失,必然引起生态系统服务功能的弱化,不利于实施以保护自然天敌为主的害虫生态控制。农业的集约化经营导致自然生境破碎化,减少了农业景观的复杂性,使得作物和非作物变成一种相对离散化的生境类型和镶嵌的景观格局;破碎化的生境不仅会减少某些物种的丰度,还会影响物种之间的相互关系及生物群落的多样性和稳定性。非作物生境类型如林地、灌木篱墙、田块边缘区、休耕地和草地等,是一种比较稳定的异质化环境。非作物生境较少受到干扰,可以为寄生性和捕食性节肢动物提供适宜的越冬或避难场所以及替代猎物、花粉和花蜜等资源,因此,非作物生境有利于自然天敌的栖息和繁衍,也有利于它们迁入邻近的作物生境中对害虫起到调节和控制作用。景观的格局-过程-尺度影响农田生物群落物种丰富度、多度、多样性以及害虫与天敌之间的相互作用。从区域农业景观系统的角度出发,运用景观生态学的理论和方法来研究作物、害虫、天敌等组分在不同斑块之间的转移过程和变化规律,揭示害虫在较大尺度和具有异质性的空间范围内的灾变机理,可为利用农业景观生物多样性来保护农田自然天敌,实施害虫的区域性生态控制提供新的研究思路和手段。

Agricultural intensification has resulted in simplification and fragmentation of natural landscape. Such expansion has been characterized by larger agricultural fields and the removal of natural habitats. These changes have had as consequences a rapid decline in biodiversity with most remaining species mostly located in ecotones and natural undisturbed habitats. This mosaic landscape also influences the ecosystem functions such as the presence and migration of natural enemies that can control pest in agricultural fields. Due to their stability and heterogeneity, natural habitats can provide shelters and alternative food for these species thus maintaining their critical roles in agroecosystems. Considering the need for such diversity in these ecosystems, sustainable pest management requires a landscape management approach.. Sustainable pest management can only be achieved if conservation of biodiversity takes into account the mosaic pattern of this landscape, thus reducing distances between habitats for poorly-dispersed and specialized natural enemies. Structurally complex landscapes with high habitat connectivity may enhance the roles of beneficial species by efficiently regulating pest populations. Their heterogeneity allows for greater level of species diversity where natural habitats compensate the homogeneity and reduction in diversity in agricultural fields. Complex landscapes characterized by highly connected crop and non-crop mosaics may be best for the survival of natural enemies and long-term conservation of biodiversity. However, further studies are required to better design agricultural landscapes that optimally maintain biodiversity of natural enemies in support of regional ecologically pest management.