Abstract
In agroecosystems, crop diversification plays a fundamental role in maintaining and regenerating biodiversity and ecosystem services, such as natural pest control. Temporal diversification of cropping systems can affect the presence and activity of natural enemies by providing alternative hosts and prey, food, and refuges for overwintering. However, we still lack studies on the effects of temporal diversification on generalist predators and their biocontrol potential conducted at field scale in commercial agricultural settings. Here, we measured proxies of ecosystem functions related with biological pest control in 29 commercial agricultural fields characterized by cereal-based cropping system in Lower-Saxony, northern Germany. The fields differed in the number of crops and cover crops cultivated during the previous 12 years. Using the Rapid Ecosystem Function Assessment approach, we measured invertebrate predation, seed predation and activity density of generalist predators. We aimed at testing whether the differences in the crop rotations from the previous years would affect activity of predators and their predation rates in the current growing season. We found that the length of the crop rotation had neutral effects on the proxies measured. Furthermore, predation rates were generally lower if the rotation comprised a higher number of cover crops compared to rotation with less cover crops. The activity density of respective taxa of predatory arthropods responded differently to the number of cover crops in the crop rotation. Our results suggest that temporal crop diversity may not benefit the activity and efficiency of generalist predators when diversification strategies involve crops of very similar functional traits. Adding different resources and traits to the agroecosystems through a wider range of cultivated crops and the integration of semi-natural habitats are aspects that need to be considered when developing more diverse cropping systems aiming to provide a more efficient natural pest control.
Highlights
Biological control of pests by natural enemies represents an important ecosystem service in agriculture
In terms of identity of predator groups, attack marks caused by arthropods were found in 50% of the dummies attacked, while marks caused by vertebrates were found in 54,7% of the dummies attacked, with almost the totality of the latter were caused by rodents and only one case was attributed to birds
We expected to observe these effects driven by the previous crop rotation management on the ecosystem functions measured in the field during the current growing season
Summary
Biological control of pests by natural enemies represents an important ecosystem service in agriculture. Generalist ground-dwelling predators such as carabids (Coleoptera: Carabidae), spiders (Arachnida: Araneae), and staphylinids (Coleoptera: Staphylinidae), can occur in arable fields in large number and, given their polyphagous feeding habits, they can play a relevant role in suppressing pest populations (Ekschmitt et al, 1997) The occurrence of these generalist predators and the provision of the natural biocontrol service is threatened in many cropping systems through agricultural intensification resulting in loss of landscape elements, enlarged farm and field sizes, higher inputs of fertilizer and altogether a homogenization of land use and land management (Holland and Luff, 2000; Geiger et al, 2010; Rusch et al, 2013a). It is necessary to measure abundance and diversity of generalist predators, and to assess their potential contribution to pest control
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