RESUMO
Over the past decades, lands alongside Gurguéia River have witnessed rapid expansion of soybean agriculture which has increased soil degradation and affected nutrient concentration in sediment, especially phosphorus (P). The present study aimed to quantify the P concentration in soils under different land uses (i.e., croplands, grasslands, and cerrado) and fluvial sediments (suspended sediment, channel bank, and riverbed sediments), assessing pollution over the main watercourse in cerrado biome Gurguéia watershed, located in Piauí State, Brazil. In total, 136 composite soil samples at a depth of 0-5 cm, under different land uses, as well as 51 composite fluvial sediment samples were collected over the watershed. The land use change from native cerrado had resulted in an increase of total phosphorus (TP) whose concentration was higher in cropland areas, followed by suspended sediment, channel bank, and riverbed sediments. This high concentration in cropland areas resulted from phosphate fertilizer inputs. The transfer of phosphorus to water bodies was evidenced, since an increase of TP was observed in suspended sediment, channel bank and riverbed sediments. Mineralogical signatures in sediments were identified by X-ray diffraction analysis which showed the occurrence of kaolinite, illite, smectite, iron oxides, and other minerals in lesser proportions. The presence of 1:1 minerals was higher in riverbed sediments and downstream sampling points, while 2:1 minerals were present in higher proportions in suspended sediment and channel bank sediment, as well as at the upstream and middle sampling points. This finding shows that land use change from cerrado to cropland due to soybean agriculture expansion might increase P discharges from terrestrial to aquatic environments, with sediments being the major carrier of this element.
Assuntos
Fósforo , Solo , Agricultura , Ecossistema , Monitoramento Ambiental , Sedimentos Geológicos , Fósforo/análiseRESUMO
ABSTRACT Knowledge about the spatial distribution of fruit flies (Diptera: Tephritidae) and tritrophic interactions (fruit-fruit fly parasitoid) contributes to the monitoring and maintenance of the numerical density at a level lower than economic damage. The purpose of this study was to identify the spatial distribution and associations of fruit flies with their parasitoids and host plants in the municipality of Bom Jesus-PI. The flies were obtained from fruit collection from July 2018 to May 2019. A total of 1,711 individuals were obtained, represented by six species: Anastrepha obliqua (Macquart, 1835), An. fraterculus (Wiedemann, 1830), An. alveata Stone, 1942, An. sororcula Zucchi, 1979, An. zenildae Zucchi, 1979 and Ceratitis capitata (Wiedemann, 1824). Anastrepha obliqua was the species with the widest distribution throughout the ecotone area. Ceratitis capitata is distributed only in the urban perimeter. A tritrophic relationship occurred between four species of parasitoids, Asobara anastrephae (Muesebeck, 1958) or Opius sp. associated with An. obliqua in Spondias mombin or S. tuberosa fruits. Opius sp. has also been associated with An. alveata in Ximenia americana. Pachycrepoideus vindemiae was obtained from C. capitata in Malpighia emarginata, in addition to An. obliqua in Averrhoa carambola. Therefore, fruit flies are associated with native fruit trees (S. tuberosa, S. mombin, S. purpurea, P. acutangulum, Inga laurina, X. americana) and exotic fruits (M. emarginata, A. carambola, P. guajava). Ceratitis capitata was recorded for the first time in the state of Piauí infesting I. laurina (Sw.) Willd. This is the first record of the parasitoid genus Spalangia. in An. obliqua in Piauí and in the semiarid region of Brazil.
RESUMO
Soil and water are vital natural resources. However, due to their indiscriminate use, these resources are being seriously threatened. Therefore, it is essential to manage them in a sustainable way and leave them for future generations. Population and agricultural areas have expanded, deforesting native landscapes for cultivation and pastures. As a result, soil loss from agricultural areas is increasing the amount of sediment transport in water courses. The objective of this study was to quantify soil loss and sediment yield from the Corrente dos Matões sub-basin (CMSB). These measurements are essential to quantify the environmental impact of advancing agricultural frontiers. The Universal Soil Loss Equation (USLE) was applied due to its wide use, compatibility with GIS, and data availability. The suspended sediment transport was calculated by collecting samples with DH-48 sampler. From the application of USLE, the average soil erosion contributed very little to sediment delivery in the watercourse, with a magnitude of only 0.37 t ha-1 year-1. The highest soil loss was associated with greater slope and was observed in areas with agriculture or under the absence of vegetation cover. The low transport of suspended sediments in CMSB is due to the existence of preserved sites. About 99% of the sub-basin had a low degree of erosion. The high degree of soil loss was attributed to the cliffs and the development of agricultural activities leaving the soil uncovered. This work will help identify the most susceptible areas to water erosion for optimizing the allocation of financial resources for the preservation of this natural resource.