Abstract Epigeic coleopteran species are linked by complex trophic webs and implicated in several ecosystem services for agriculture. Although there are reports of ground-dwelling Coleopterans inhabiting main extensive agroecosystems, their assemblages in horticultural crops in Argentina have been little explored. We examined the community structure of epigeal Coleoptera assemblages of Curculionidae, Carabidae, Staphylinidae and Coccinellidae species, in lettuce and tomato crops located in Northern Buenos Aires province, over a 3-year sampling period (2010 to 2013) by using pit-fall traps. Crop species and cycles, and phytosanitary measures (conventional and organic farming), were main factors considered as influencing the insect species composition, abundance and seasonal occurrence in the assemblages. Seventy coleopteran species were identified. The curculionids Ceutorhynchini sp. and Phyrdenus muriceus (Germar), the carabid Scarithes anthracinus Dejean, the coccinelid Eriopis connexa (Germar) and the staphylinids Aleochara sp. and Aleochara obscurus Bernhauer are the most common species in lettuce and tomato crops in the region studied. Especially the carabids, staphylinids and E. connexa are known act as natural enemies of several pests in the agroecosystems studied. Coleopteran assemblages found in lettuce differed from those associated to tomato crops, being the cropping season the main factor that influenced the community structure.

Abstract Edaphic arthropodofauna reflects the vegetation conditions and the soil functioning, therefore, its study is a useful tool to evaluate the soil crops sustainability. Oribatid mites and collembolan hexapods (mesofauna) as well as beetles and spiders (macrofauna) are permanent, abundant and diverse groups in these systems. They are essential organisms in the soil functioning because they regulate and participate in different stages of the decomposition process. The aim of the study was both, to identify the main components of the meso and macrofauna while a conventional tomato crop was developing its cycle and to propose a possible model of relationships among them which helps to assess positive effects due to healthy practices. The study was carried out in a farm where tomato conventional management was being applied, in the neighborhood area of La Plata city. The fauna was collected during a complete crop cycle from December 2012 to February 2013, using the appropriate procedures for each group. We collected 136 individuals and seven oribatid species, 59 individuals and nine collembolan species, 300 individuals and 12 spider species and 113 individuals and 32 coleopteran species. Among them, Scheloribates praeincisus acuticlava, Tullbergidae sp. 1, Glenognatha lacteovittata, Lycosidae sp. 2, Linyphiidae sp. 4 and Phyrdenus muriceus were the most abundant permanent populations in each group. The poor records of mesofauna indicate that it establishes weak links in the trophic soil network, possibly due to the disruptive effect of conventional management practices. The macrofauna presents the greatest number of individuals and specific diversity, especially spiders, probably by their capacity to move to the adjacent crop areas. It is concluded that the edaphic fauna stable group is principally composed by predators, saprophagous and phytophagous related to the crop, so they belong to the herbivory network more than the detritus one.

Resumen La artropodofauna edáfica refleja las condiciones de la vegetación y el estado del funcionamiento del suelo y, por lo tanto, su estudio es útil como herramienta de evaluación de la sustentabilidad de suelos cultivados. Ácaros oribátidos y hexápodos colémbolos (mesofauna); coleópteros y arañas (macrofauna) son grupos permanentes, abundantes y diversos en estos sistemas. Son organismos esenciales para el funcionamiento del suelo porque regulan y participan en distintas etapas del proceso de descomposición. El objetivo del estudio fue identificar a los principales componentes de la meso y macrofauna del suelo durante un ciclo de cultivo de tomate convencional y proponer un posible modelo de interrelaciones entre ellos, que sirva para evaluar los beneficios de la aplicación de prácticas consideradas más saludables. El estudio se llevó a cabo en una parcela sembrada con tomate, con manejo convencional, en el área periférica de la ciudad de La Plata. La fauna se recolectó durante un ciclo de cultivo completo desde diciembre de 2012 hasta febrero de 2013, a través de los procedimientos adecuados para cada grupo. Se recolectaron: 136 individuos y siete especies de oribátidos, 59 individuos y nueve especies de colémbolos, 300 individuos y 12 especies de arañas y 113 individuos y 32 especies de coleópteros. Entre ellas Scheloribates praeincisus acuticlava, Tullbergidae sp. 1, Glenognatha lacteovittata, Lycosidae sp. 2, Linyphiidae sp. 4 y Phyrdenus muriceus, fueron las más abundantes y permanentes poblaciones de cada grupo. El pobre registro de mesofauna indica que ésta constituye un eslabón débil en la red trófica del suelo, posiblemente debido al efecto disruptivo de las prácticas convencionales de manejo. Los representantes de la macrofauna presentan mayor número de individuos y de diversidad específica, especialmente las arañas, debido probablemente a que cuentan con la capacidad de trasladarse hacia zonas aledañas al cultivo. Se concluye que el conjunto estable de la fauna edáfica del sistema estudiado está constituido principalmente por depredadores, saprófagos y fitófagos relacionados con el cultivo, es decir pertenecen a la red de herbivoría más que a la de detritos.