The effects of different rice cultivation systems and ages on resting stages of wetland invertebrates in southern Brazil

Abstract

The use of machinery and pesticides in modern agriculture are supposed to negatively affect the viability and diversity of invertebrate egg banks. Studies that evaluate the emergence of invertebrates through analysis of their dormant stages are needed in order to identify the resiliency of food webs in wetlands. In this study, the following hypotheses were tested: (1) richness is lower in conventional rice fields than in organic ones and natural wetlands; (2) richness is lower in older rice fields than younger fields; (3) composition varies among different rice systems and ages; and (4) emergence rate may vary among rice systems and ages over time. Dry sediment samples were collected from six rice fields cultivated under different systems, nine conventional rice fields with different cultivation ages and three natural wetlands. Our study showed that the richness was surprisingly higher in conventional rice fields than wetlands, with cladocerans being more associated with the former and insects more frequent in the latter. Invertebrate richness was similar among rice fields of different ages, but the composition differed between 20-year-old fields and younger fields. Variation in the viable resting stages found across different rice cultivation systems and ages contributes valuable information to wetland restoration initiatives.