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The role of epigeic macroarthropod predators in the regulation of abundance and biomass of saprophagous nematodes on grass litter of meadow

Stanuszek S.

Polish Journal of Ecology

2001

Vol. 49, nr 1

45-57

Research hypothesis supposed that: 1) microbes, saprophagous nematodes and predacious, epigeic macroarthropods could create the aboveground, detrital food web of meadow; 2) in such food web the top-down regulation of abundance and biomass of saprophagous nematodes and microbes take place in a way predicted by trophic-dynamic theory. A field experiment with manipulation of macroarthropod predators abundance as a method in order to test this hypothesis was chosen. The results were quite opposite to the supposition of the trophic-dynamic theory. Exclusion of epigeic macroarthropods from the supposed food-web results in decreased abundance and biomass of nematodes and increased abundance of bacteria considered as entity. However, it was evident that the top-down regulation of nematode abundance exists there, but its mode is rather behavioral than trophic. Trophic interactions between predacious macroarthropods and nematodes has not been observed there. The macroarthropods served as the transport for the nematodes. In such way they could regulate the initial number of nematodes which colonized the litter.

Effect of macroarthropods on microbial and faunal numbers and organic matter content in soil

Kajak A., Kusińska A., Stanuszek S., Stefaniak O., Szanser M., Wasylik A., Wasilewska L.

Polish Journal of Ecology

2000

Vol. 48, nr 4

339-354

A field exclusion experiment in Arrhenatherrethalia mown meadow was carried out in mesocosms to analyse the role of epigeic, mobile macroarthropods in decomposition processes. A mineral bag technique allowed assessment of annual organic matter accumulation in the sandy substrate of mesocosms. Higher total organic C content was recorded in the top substrate layer (0-3 cm) in mesocosms accessible for macroarthropods, than in closed, inaccessible ones (17 and 23% more, respectively, in the two years), as well as higher amount of C in humus acids (6 and 36% more in two years). Possible reasons for these differences were considered. The total plant biomass, the litter disappearenc3 rate and water content in litter did not differ significantly between the types of mesocosms. In the top layer of mesocosms accessible for macroarthropods higher content of comminuted plant material (38,9 g m^-2) and arthropods feces (12.3 g^-2) were found compared to the amount in closed mesocosms (17,1 and 2,1 g m^-2 respectively). But the particulate organic matter derived from comminuted plant remnants and from fecal pellets accounted, in the period of the highest content, for about a half of the total carbon accumulated in the top substrate layer. In the litter of the open mesocosms reduced number of fungivorous mites and aphids was found, coupled with higher density of bacterivorous nematodes and higher abundance of fungi. The density of fungivorous mites was negatively correlated with the intensity of area patrolling by Araneae (tau = -0.79, P=0,0028) and Staphylinidae (tau = -0.58, P = 0.03). The elimination of aphids was positively correlated with area patrolling by the last group (tau = 0.81, P = 0.005). These results suggest that predation by macroarthropods changed proportions between fungi- and bacteriovorous invertebrates and as a consequence proportions between fungi and bacteria.