Effect of forest canopy gap on soil enzyme activity, dissolved organic matter and organic acids

Canopy gaps play an important role in the dynamics of temperate forests. The present study aimed to evaluate the effect of canopy gaps area on soil biochemical activities in Khanikan region of Nowshahr. In this study, 32 canopy gaps with small (195-205 m2), medium (397-406 m2), large (593-604 m2) and very large (792-807 m2) areas, 8 replications for each, were considered. Five points were selected within each canopy gap; soil samples were taken and mixed due to transferring to laboratory for analysis of physico-chemical, biological and biochemical properties. According to findings, whole of soil physico-chemical (except for silt content) and biological properties were significantly affected by different canopy gaps areas. The highest urease activity was found under medium and small (22.97 and 22.54 µg NH4–N g−1 2 h−1) canopy gap areas, respectively. Medium gaps showed the most values of acid phosphatase (633.75 µg PNP g−1 h−1), arylsulfatase (153.38 µg PNP g−1 h−1) and invertase (273.25 µg Glucose g−1 3 h−1). Greater amounts of dissolved organic carbon (94.73 mg/kg) and dissolved organic nitrogen (34.66 mg/kg) were found under very large and medium canopy gap areas, respectively. Creation of very large canopy gaps was due to increasing of fulvic (454.62 mg/100g) and humic (888.88 mg/100g) acids in the studied forest ecosystem. As a general conclusion, based on forest sustainable management, it is proposed to avoiding of large and very large canopy gaps creation.