Análise da fauna edáfica em diferentes usos do solo no Bioma Pampa

The soil is populated by thousands of organisms which are responsible for various ecosystem functions. Among these organisms, those belonging to the soil fauna stand out and present a great sensitivity, responding to modifications in the environment, and may be regarded as a good soil quality bioindicator. This work aimed to characterize the edaphic fauna distribution in different soil uses and at different seasons of the year in São Gabriel, RS state, evaluating its use as a bio-indicator of the soil quality. Soil fauna evaluations were conducted in three areas of different soil uses: native forest, native pasture and ryegrass/soybean, in two distinct seasons (winter and summer). During the samples, the soil temperature, the soil water content and the biomass/litter were also evaluated, to verify the influence that these attributes exert on the soil fauna. The abundance and diversity were evaluated as well as the diversity, uniformity and similarity indexes in the areas were calculated. The results presented a large diversity of edaphic organisms. Collembola, Hymenoptera and Acarina were the groups with greater abundance. Some groups have shown to be sensitive to changes in environmental variables. The area with greater diversity and greater uniformity was the native forest, while the ryegrass/soybean had the least diversity and uniformity. The most similar areas were the native forest and the native pasture in the winter evaluations. The soil fauna presents potential to be used as a soil quality bioindicator.O solo é habitado por milhares de organismos responsáveis por diversas funções no ecossistema. Entre esses organismos, destacam-se os pertencentes à fauna do solo, a qual apresenta uma grande sensibilidade às modificações realizadas no meio, podendo ser considerada como um bom bioindicador de qualidade do solo. Assim, este trabalho teve como objetivo caracterizar a distribuição da fauna edáfica em diferentes usos do solo e em diferentes épocas do ano no município de São Gabriel - RS, avaliando a sua utilização como bioindicador da qualidade do solo. Foram realizadas avaliações da fauna do solo em três áreas de diferentes usos do solo: Mata Nativa, Campo Nativo Pastejado e Lavoura Azevém/Soja, em duas épocas distintas (inverno e verão). Durante as coletas, também foram avaliadas a temperatura, a umidade e a biomassa/serapilheira acumulada no solo, para verificar a influência que esses atributos exercem sobre a fauna do solo. Foram verificadas a abundância e a diversidade em nível de ordem dos indivíduos, sendo calculados os índices de diversidade, uniformidade e similaridade das áreas. Os resultados apresentaram uma grande diversidade de organismos edáficos, sendo Collembola, Hymenoptera e Acarina, os grupos com maior abundância no total das avaliações realizadas. Alguns grupos mostraram ser sensíveis a mudanças das variáveis ambientais. A área com maior diversidade e maior uniformidade foi a Mata Nativa, enquanto a Lavoura Azevém/Soja foi a menos diversa e menos uniforme. As áreas mais similares foram a Mata Nativa e o Campo Nativo Pastejado, durante as avaliações de inverno. Em termos gerais, a fauna edáfica apresenta potencial de ser utilizada na avaliação da qualidade do solo

Terracing increases soil available water to plants in no-tillage

Several management practices can increase soil water storage capacity, but their effectiveness to minimize the adverse effects of drought depends on their potential to increase the soil available water to plants. Terracing is an effective option to increase soil water storage, but its effect on available water to plants in no-tillage system is still a knowledge gap. In this study, we monitored soil water content at eight layers down to 1.6 m in two zero-order paired catchments for 16 months. Presence of five broad-based terraces in one of the catchments was the main difference between the two. Water availability to plants over time was expressed as a fraction of available water capacity (FAW). Positive differences of FAW between the terraced and non-terraced catchments were noticed over periods of rainfall shortage, but they were barely perceptible in periods of abundant rainfall. Over the 16 months, the frequency of FAW higher than 0.75 was between 46 and 50 % in the non-terraced catchment, and between 67 and 75 % in the terraced catchment. This benefit of terracing is more noticeable in thicker upper-section of the soil profile evaluated and with greater number of terraces upstream from the point of observation. We concluded that terracing in no-tillage turn excess rainfall into noticeable positive increases in available water to plants in the following periods of rainfall shortage