## 4 Discussion
At optimal humidity, the oribatids can survive even in poor substrates with a minimum SOM content; in substrates with a wide C/N range, they are limited mainly by the lack of SOM immobilized by soil microorganisms. We found a low (none) oribatid abundance and diversity in samples of MOS and MOD, where the C/N range was extensive even though the amounts of MBC and respiration suggested a good functioning microbial community. Moreover, microbial indicators' values showed that despite the reduced organic matter available to the microorganisms, the microbial community could efficiently utilize the organic carbon, even more than in both unpolluted sites. The wide range of C/N, on the other hand, suggests that in the nitrogen-poor substrates, MOS and MOD decomposition processes were slowed down due to microbial immobilization of organic matter. This could be the other reason for the total absence or reduced numbers of mites in these kinds of substrates. [PERSON] [17] demonstrated that, even though the heavy metal pollution in the study site was high, the total number of species and numerical abundance reached high values due to the high humidity and acidity of the substrate, which provided a more favorable habitat. We also confirmed a positive correlation between humidity and mite abundance (r = 0.84, \(p<0.01\)). The abundance was meaningfully lower in MOD samples, where we measured significantly lower substrate moisture than in the natural soils. Therefore, it seems that the availability of soil water highly influences the performance of soil fauna. Depending on the species, different strategies can be used to cope with low soil-water potential. Soil microarthropods may be resistant to desiccation by reducing the water permeability of their integument. This strategy has been adopted by many epedaphic (surface-dwelling) species, whereas euedaphic (soil-dwelling) species have little or no control of evaporation across the integument [70]. In general, soil moisture's positive effect on soil arthropod communities' abundance has been emphasized [71; 72]. [PERSON] et al. [72] presented a study that showed that the abundance of microarthropods in copper-contaminated soil was stimulated by enforced drought in a field experiment. It was expected that the combination of copper and drought would harm soil microarthropods. We confirmed a negative correlation between mite diversity and copper (Table 4), which, connected with the low humidity of the technogenic substrates MOS and MOD, could have had a considerable effect on the mite community. Soil acidity unlikely affects orbiatid mite communities directly since most orbiatid mite species tolerate even very acidic conditions [62; 73]. Furthermore, soil microarthropods' community structure has been relatively resistant to substantial soil pH changes [74]. The soil pH affects the colonization of forests by soil macrodecomposers, which affects orbiatid mites via changes in the thickness of the litter layer since soil acidity may affect calcium availability. A negative correlation was observed between pH and mite abundance and diversity (Table 4). Although we cannot ignore the impact of drought and various toxic metals on the mite community, our observations showed that, with increasing pH, the diversity of orbiatid decreases. However, in the case of MOS and MOD samples, we are inclined to believe that the very low diversity values were caused by a combination of critical factors, e.g., higher pH, low humidity, and high concentrations of some risk elements.