Comprehensive comparison of different sampling methods for arthropod diversity in farmland

Abstract

Aims: Arthropod biodiversity in farmlands has considerable value in terms of pest control, pollination, and other ecological services. To adequately assess arthropod biodiversity in farmlands, a fundamental step to select appropriate, accurate, and efficient sampling methods and identify appropriate indicator taxa. Methods: Here, we compared several arthropod sampling methods in different types of agricultural habitats within organic managed and conventional managed farmland, including the surface trap cup method, coloured pan traps, the sweeping method, visual counting, and the vacuum-suction method. We compared the capture efficiency, economic costs, and response sensitivity of each method for different species assemblages. Results: We found that the surface trap cup method and coloured pan traps had the highest capture efficiency, followed by the sweeping method, the vacuum-suction method, and visual counting, which had the lowest capture efficiency. Coloured pan traps was more efficient at capturing carabids, spiders, bees, and ladybugs. The surface trap cup method was mainly applicable to sampling ground spiders and carabids. The sweeping method was also effective at sampling spiders and ladybugs. In terms of economic costs, the most economical method was the surface trap cup method, which was used to capture carabids or spiders. The sweeping method had the highest cost due to its low capture efficiency of spiders. Sampling methods varied in their response sensitivity and were reasonably able to estimate abundances only of certain taxa (e.g., the number of spiders and carabids by the surface trap cup method, the total number of specimens, the number of bees, and the number of ladybugs by coloured pan traps, and the number of Orthoptera and Hemiptera by the sweeping method). Conclusion: We further compared sampling methods after taking into account the economic value of the taxon, the difficulty of sampling operation, the difficulty of taxon identification, the degree of passive sampling, and whether the taxon was influenced by different individuals conducting the sampling. The most comprehensive method was the surface trap cup method targeting carabids and spiders. Using a combination of different sampling methods for multiple taxa is recommended to comprehensively evaluate and monitor overall farmland arthropod biodiversity, and our results suggest that the best combination includes sampling carabids and spiders using the surface trap cup method and sampling bees using coloured pan traps.