Impact of rice field management on the spider community characteristics in Taihu Lake Basin

Spiders are important natural enemies that provide a key biological control service in rice planting systems. In recent decades, agricultural intensification has caused a series of environmental problems, including the loss of biodiversity and the decline of associated ecosystem services. Therefore, it is necessary to explore if the spider diversity can be improved by adjusting the rice farming practices to enhance the biological control services to allow more sustainable agricultural production. Recent studies on rice field spiders have compared the spider diversity between organic and conventional farming systems. However, studies on spider diversity in green rice fields are rare. The Taihu Lake Basin is an important rice production area in China, but it has also suffered from serious non-point pollution in recent years. Thus, it is important to develop a sustainable rice production approach and conserve the biodiversity and associated ecosystem services for regional sustainability. In this study, we sampled spiders with a suction sampler to assess the impact of different farming practices, including organic, green, and conventional farming practices, on the diversity, composition, and dynamics of spiders in rice fields. The results indicated that 1) there were significant differences in the spider diversity among different farming systems. Species richness, abundance, and the Simpson diversity index of spiders in organic rice fields were significantly higher than those in the other two treatments. 2) There were no significant differences in spider body size and the ballooning capacity among different farming practices. 3) The composition of spider communities in organic rice fields was distinct from that in conventional rice fields, whereas green rice fields had a similar spider composition as that of conventional and organic rice fields. 4) Organic and green rice fields were dominated by web-building spiders, whereas conventional rice fields were dominated by hunting spiders. 5) Organic rice fields had many indicator species, such as Bianor incitatus, Chrysso octomaculata, and Clubiona corrugata, while the spider communities in green and conventional rice fields were dominated by generalist and common species and lacked endemic species. 6) The spider community diversity in rice fields changed with rice growth. The species richness and Simpson diversity indexes of the spider communities were greater in organic rice fields than those in conventional and green rice fields across all rice-growing seasons, except during the early tillering and elongation stages. In summary, compared with conventional and green farming systems, organic farming system sustains greater spider diversity and distinct spider compositions with more web-building and indicator species. The spider diversity under green farming system, on the other hand, did not differ from that under conventional rice practices. To improve spider diversity and the associated biological control services in rice fields, the transformation of conventional rice production to organic production and reduced chemical reagents input should be encouraged, which is also important for the ecological restoration of the Taihu Lake Basin.