Variability of the Oribatida/Prostigmata ratio in altered patches of the coastal matorral of the transitional desert of Chile.
The objectives of this study were to document the variability of the Oribatida/Prostigmata mite relationship (O/P) in altered patches of coastal matorral of the transitional desert of Chile, and to explore its viability as an indicator of the effects of soil degradation and its rehabilitation with introduced species. We studied a transect that extended through three latitudinal sections of matorral. The landscape of these sections consisted of patches dominated by: (a) original matorral in semi natural condition, (b) severely degraded patches of matorral aforested with Acacia saligna (Labill.) H.L. Wendl. (Fabaceae), (c) severely degraded patches of matorral aforested with Atriplex nummularia Lind. (Amaranthaceae), and (d) patches severely degraded, without afforestation. Results from patches aforested with A. saligna were inconclusive. The lowest O/P mean was obtained from patches without afforestation. Higher scores resulted from patches with semi-natural matorral and those afforested with A. nummularia. These results suggest that the O/P ratio has the potential to be used as an indicator of rehabilitation of degraded soils subject to improvement efforts of their plant cover. The O/P ratio obtained in this study tended to be higher than that found in previous work conducted in arid ecosystems. This result is probably due to the fact that, following current taxonomic criteria, we excluded Endeostigmata from the Prostigmata-counts. Since some Endeostigmata families are fairly common and abundant in arid and semi-arid soils, their elimination reduced the magnitude of the denominator of the relationship. The current taxonomic situation of Acari obliges us to redefine its value as an indicator and to explore its validity in a broader set of situations.