The impact of Brant`s oak (Quercus brantii Lindl.) decline on stand soil characteristics (Case study: Kohmareh Sorkhi, Fars Province)

Nowadays, the oak decline is the most important challenge in the Zagros forests for the last decade. Concerning the importance of soil physical, chemical, and biological properties in the forest ecosystems performance, the impacts of oak decline on soil characteristics were studied. In spring, two declined stands and two healthy stands of Brant`s oak (Quercus brantii Lindl.) with one ha area (100×100 m) in the north and south aspects were selected and then soil samples were collected systematically from 0-10 cm depth. Next, soil texture, reaction, EC, moisture content, organic carbon, nitrogen, potassium, and phosphorus content of collected soils were analyzed. Furthermore, basal soil microbial respiration, induced soil microbial respiration, and nitrification potential were measured. The results showed that pH, organic material and carbon, and nitrogen did not have any significant difference between the declined and healthy stands. On the other hand, EC (around 28-29 %), moisture (around 3-4 times), potassium (around two times), and phosphorus (around 4-5 times) content were considerably higher in the healthy stands. Furthermore, the highest induced microbial respiration were recorded in southern (2.06) and northern healthy stands (1.67) and southern decline stand (1.38 mg CO2.100g-1.dm.h-1), respectively while we did not find any reasonable trend for basal respiration. Nitrification potential did not response to oak decline occurrence. Although soil nutrient significantly declined in response to oak decline, it can be supposed that dried leaves and branches can repair deficiency of soil organic material to some extent in the declined stands but over time, as trees weaken, soil quality will decline. Finally, monitoring of soil fauna and soil enzymes can be suggested for future research.