Spatial resilience of a soil microarthropod community on disturbed areas

Abstract

Disturbances in soil ecosystems are generally associated with natural or anthropogenic factors (or both), and may affect the abundance and diversity of soil microarthropod communities. Nevertheless, such changes help to maintain the dynamic of the ecosystems, and play an important role in its conservation and future reorganization. After disturbances in soil, the recovery of soil fauna communities stimulates the recolonisation of those areas and, consequently, the establishment and growth of the different populations. A successful recolonisation depends not only on the existence of suitable habitat conditions in those disturbed areas, but also on the dispersal ability of the organisms and the spatial configuration of disturbed and non-disturbed (donor) patches. In principle, an interspersion of disturbed and donor patches will increase the spatial resilience of these communities, i.e., recolonisation will be faster. Moreover, when minimum habitat conditions are found, community will recover faster on a spatial basis. The study was developed at the Botanical Garden of the University of Coimbra, Portugal. Collembola were used as bioindicators to analyse the abundance and number of taxa after disturbances. Collembola are one of the most numerous species found in soils. Furthermore, Collembola help keep basic ecological services of the soils. Their traits allow an analysis of the ability of dispersal and recolonisation of each species according to morphotypes. This study aims to investigate the spatial resilience of Collembola on disturbed areas focusing on the influence of number of donor patches (non-disturbed habitat) within disturbed treatments. The experiments consisted of four treatments comprisingdifferent numbers of donor patches (0, 1, 2 and 4 patches) inside a disturbed matrix, but maintaining the total donor area. Each treatment was replicated 3 times following a block design. A disturbance was applied in order to decrease the number of Collembola in the treatments, trying to minimize the impact on habitat structure. Both soil and litter layers were defauned: leaf litter was removed and dried at 70°C and placed again in the field; at leaf replacement, soil was showered with water at 80ºC. Soil corers were collected immediately after the disturbance and six weeks later. Soil microarthropods were extracted from these soil corers using the Tullgren funnel method. Extracted Collembola were classified according to morphtypes, following Vanderwalle’s scoring traits (mainly related to the dispersal ability of the organisms). Apart from a few rare exceptions, community composition was similar in undisturbed areas inside and outside treatments. Also, but contrary to what was expected, there was no clear trend in the decrease of dissimilarity values in community composition with the increase of the number of donor patches inside the disturbed areas. (with the exception of pitfall data on block 2). Since weather conditions and habitat structure play an important role in Collembola distribution, taking these variables into consideration when defining the disturbance to be applied may help further studies find better trends and differences in community composition and, ultimately, help to unveil a bit more on the process of recolonisation after disturbance.