Spatial Variability of Soil Fauna Under Different Land Use and Managements

Abstract

Geostatistics allows the evaluation of the distribution pattern of data with high spatial variability in agricultural systems. This study aimed to evaluate the spatial variability of biological diversity indices of soil fauna under different land (agriculture and forest). Samples were collected in seven areas (millet, soybean, corn, eucalyptus, pasture crops, and preserved and disturbed Cerrado), in Maranhão state, Brazil. The soil fauna was caught trapped in pitfall traps, installed 3 m away from each other. In each area, 130 traps were maintained for seven days. After this period, they were removed and their content transferred to bottles and taken to the laboratory, where the insects were screened and identified at the level of orders and families. Eight indices were calculated, namely: individuals trap-1 day-1 , Jackknife richness estimator, the Simpson, McIntosh, Shannon, and total diversity, and Simpson dominance, and Pielou equitability indices. The spatial variability was derived from the semivariograms fitted to Gaussian, spherical, and exponential geostatistical models. Statistical analysis showed medium values of the coefficient of variation for millet, except for the indices individuals trap-1 day-1 and McIntosh diversity, which were considered high. The values of the correlation matrix were negative for some indices, suggesting an inverse relationship. For millet, corn, eucalyptus, disturbed Cerrado, and pasture areas, the Shannon diversity index exhibited a pure nugget effect. For the areas of millet, corn, disturbed Cerrado and pasture, the total diversity index was adjusted to the Gaussian model. The degree of spatial dependence was considered high for the individuals trap-1 day-1 and Pielou equitability indices for millet. Only for soybean and pasture similarity in the scaled semivariograms was observed for the spatial variability of the indices, indicating similarity of performance. Soil management and land use affect the patterns of soil fauna abundance, richness, and diversity. The presence of groups such as Araneae, Diplura, and Poduromorpha are related to ecological equilibrium, quality, and sustainability of the agricultural systems studied.

Digital soil mapping in the Bara district of Nepal using kriging tool in ArcGIS

“…Determination of the range values provides an idea of the correlation between different sampling locations, along with the maximum spatial dependence distance between them [ 95 ]. Fluctuation in the range with different lag sizes indicates that spatial structure may merely be regarded with a single model for semivariogram [ 96 ]. This difference may not be important for semivariance calculation, but it may be important if the purpose is to understand the underlying spatial structure of the data [ 97 ].…”

Multifractal analysis of soil fauna diversity indexes

“…The area with eucalyptus had values of α 0 greater than 1,000, indicating that the fauna of the soil in this area is more diverse (Shannon -α 0 = 1,132 ± 0,038). The occurrence of higher numbers of invertebrates in the area with eucalyptus can be explained by the higher content of organic material (Table 1 -OM = 27 g•dm -3 ) (Wardle et al 2006;Silva et al 2018). This justifies the dominance of Collembola, which, according to Bardgett and van der Putten (2015), are organisms that only develop in favorable environments with high content of organic matter.…”

“…The natural dynamic of soil fauna is altered with time in agricultural systems. Silva et al (2018) found that the abundance and richness of soil organisms are altered depending on the use and the management. Paul et al (2015) described that conservationist management practices besides improving the physical and chemical quality of the soil, also provided the increment of the soil fauna and other biological attributes.…”

The effect of farming system and management practices on surface-dwelling soil macrofauna

“…There are often considerable differences between organic and conventional agriculture in particular conditions, which does not only mean the use of pesticides but also the way the soil is tilled. In some cases these interventions can be quite a harmful factor in terms of biodiversity of soil fauna (Silva et al, 2018). These authors state that physical disturbance (e.g., ploughing) is a key factor affecting biotic activity and species diversity in agroecosystems.…”