Ground-dwelling spider diversity within organic and conventional croplands in the hilly and plain areas of North China

The growing demand for food has led to increased focus on agricultural development in hilly areas. However, intensive agriculture may be one of the main reasons for biodiversity loss in the landscape. To better understand the effects of production management practices and boundary hedges on ground-dwelling spider biodiversity in different topographic areas, this study was conducted at five different farmlands in a typical agricultural area of North China. In the hilly area, conventional maize fields with and without a plant hedge (CMH/CM) and organic maize fields with or without a plant hedge (OMH/OM) were sampled for spiders. Conventional maize fields without a plant hedge were also sampled in the plain area (PCM). Spiders were sampled using pitfall traps from August to September 2019. The results showed that the Shannon diversity and rarefied species diversity of spiders in the maize fields were significantly higher in the hilly area than in the plain area; and organically managed maize fields had significantly higher spider rarefied species diversity than conventional maize fields. Furthermore, the spider rarefied species diversity was significantly higher in maize fields with hedges than without hedges. The species composition of the spider assemblages significantly differed between the farmlands with organic and conventional management, between the farmlands in the hills and plains, and between the farmlands with and without hedges. Based on these results, we recommend that regional land use planning and zoning management strategies be applied to improve agricultural production development and conserve biodiversity. The hilly region experiences less human disturbance and has greater diversity; thus, it may represent a hotspot for biodiversity conservation in an intensive agriculture region that could be promoted by developing extensive agriculture (such as organic agriculture) and more diverse landscapes with hedgerows. In the plain area, the semi-natural boundary should be reserved, and the agricultural production intensity should be reduced to improve the environment and promote green development.