Effect of fire on nematode populations in superficial soils of Abr forest, city of Shahroud, Iran

Nematodes are one of the most abundant and effective soil organisms in natural ecosystems such as forests, and have been used as bioindicators in studying the effect of disturbing factors on environment. In this study, effects of fire on soil-inhabiting nematode populations in superficial soil layers (depth of 10, 20, 30 and 40 cm) of Abr forest, city of Shahroud was studied. To compare nematode populations in the soils of burned and unburned areas, a total number of 100 soil samples were taken from the above mentioned depths in two times (one and 13 months after the fire) based on a randomized complete block design. After exteraction by centrifugation or flotation method in a solution of sugar and identification and counting of nematodes, their groupings were performed using a stereo microscope based on morphological characteristics of stoma and pharynx. The results showed that the populations of nematodes were decreased in burned soil at depths of 10, 20 and 30 cm, compared to unburned soil, one month after burning. The highest population decrease was observed at the depths of 20, 10, 30 and 40, respectively in burned soil and in the first sampling date,while the highest population increase was observed at depths of 30, 40, 20 and 10 cm, respectively for burned soil and the second sampling time (P≤0.05).