In the model catchment Vydrica brook in Small Carpathians (mostly beech forest), concentrations of the selected chemical substances were monitored for evaluation of the land use impact upon the brook water quality. Concentrations of these substances were monitored within the years 1991-1993. In order to evaluate also a development of the long-term trend of the observed data, we are continuing in their monitoring since 2004. In this paper there are evaluated nitrate concentrations from two localities: in the upper Vydrica part (Spariská), and on the Bratislava city area limit (Červený Most), in the Vydrica lower part. The mean nitrate concentration in 1991-1993 at Spariská was 14.54 mg l-1, at Červený Most locality 10.84 mg l-1, in the years 2004-2005 the mean concentration at Spariská it was 11.85 mg l-1, and 9.36 mg l-1 at Červený Most. From the observed data it follows that in the 2004-2005 years the nitrate concentration dropped in comparison with the 1991-1993 period. As there was a significant relationship documented between the nitrate concentration and discharge, the empirical relationships were developed for estimating of daily nitrate concentration values based on the mean daily discharges, for the 1987-2005 period. From these, then the mean monthly and yearly nitrate wash offs were calculated from the unit area. So for the Spariská subcatchment the mean yearly nitrate wash off range was 15.42 to 102.37 kg ha year-1, for the profile Červený Most it was 9.01 to 70.53 kg ha year-1. and V modelovom povodí potoka Vydrica v Malých Karpatoch (prevažne bukový les) boli sledované koncentrácie vybraných chemických látok v povrchovom toku za účelom hodnotenia vplyvu využitia krajiny na kvalitu vody v toku. Koncentrácie týchto látok sme sledovali v rokoch 1991-1993. Aby sme zhodnotili dlhodobý trend vývoja nameraných údajov, od roku 2004 v monitoringu pokračujeme. V tomto príspevku sú zhodnotené koncentrácie dusičnanov na dvoch lokalitách: v hornej časti Vydrice (Spariská) a na hranici s hlavným mestom Bratislava (Červený Most) v dolnej časti povodia. Priemerná koncentrácia dusičnanov v rokoch 1991-1993 bola na lokalite Spariská 14,54 mg l-1, na lokalite Červený Most 10,84 mg l -1, v rokoch 2004-2005 bola priemerná koncentrácia na lokalite Spariská 11,85 mg l-1 a na Červenom Moste 9,36 mg l-1. Z nameraných hodnôt vyplýva, že v porovnaní s obdobím rokov 1991-1993 v rokoch 2004-2005 došlo k poklesu koncentrácií dusičnanov. Keďže sa preukázala významná závislosť medzi koncentráciami dusičnanov a prietokmi, odvodili sme empirické vzťahy na nepriamy odhad denných hodnôt koncentrácií dusičnanov na základe meraných priemerných denných prietokov za obdobie rokov 1987-2005. Z vypočítaných denných koncentrácií dusičnanov boli vypočítané priemerné mesačné a ročné odnosy dusičnanov z jednotky plochy. V podpovodí Spariská sa ročné odnosy dusičnanov pohybovali od 15,42 kg ha-1 rok-1 do 102,37 kg ha-1 rok-1, v profile Červený Most od 9,01 kg ha-1 rok-1 do 70,53 kg ha-1 rok-1.
Vegetation and biocrust play crucial roles in dune stability and mobility, and their interaction can lead to bistability, temporal oscillations, and hysteresis. We studied a two-dimensional (2D) mathematical model of vegetation and biogenic crust cover dynamics on sand dunes. Under a certain parameter range, the space-independent version of the model exhibited the bi-stability of an oscillatory state and a steady state, and we studied the 2D dynamics of the model under these parameters. The patterns developed by the 2D model showed a high degree of spatial heterogeneity and complexity depending on the initial conditions and on the state type across the front. The results suggest that spatial heterogeneity and complexity can evolve from the intrinsic dynamics between vegetation and biocrust, even without natural geodiversity and spatiotemporal climate fluctuations. In the real world, these two types of intrinsic and extrinsic heterogeneity processes interact such that it is difficult to distinguish between them.