Tree species effects on albedo, soil carbon and nitrogen stocks in a temperate forest in Iran

Albedo and carbon sequestration, as important climatic parameters, are influenced by many factors. Since forests are important factors affecting carbon stocks, albedo, they have a significant role in global warming. This study intends to explore interactions between trees species and albedo, soil carbon (C) and nitrogen (N) stocks in the Hyrcanian forest of northern Iran. The study sites consist of five 20-year-old forest plantations consisting of maple (Acer velutinum Bioss), poplar (Populus deltoides Barter. ex Marsh), Mediterranean cypress (Cupressus sempervirens var. Horizontalis (Mill.) Loudon), chestnut-leaved oak (Quercus castaneifolia C. A. M. macranthera F. & M.) and alder (Alnus glutinosa (L.) Gaertn). In the summer, ten randomly located soil samples were taken from each stand from the top 10 cm of the soil to determine the soil characteristics, soil organic C, total C and N. Albedo was estimated with an albedometer set-up, which was installed on a movable mast in each stand. We used two analytical methods to determine the effect of tree species on albedo and soil C and N stocks. ANOVA was used to determine the significant difference between tree species and albedo, soil C and N stocks. TOPSIS technique-a commonly used classical Multi-Criteria Decision Making (MCDM) method-was employed to prioritize tree species considering the combination of the examined factors (albedo, C and N stocks). Our analysis suggests significant differences in albedo and soil C and N stocks between tree species (p < 0.01). Albedo of the alder stand (0.33) was highest and for Mediterranean cypress it was lowest (0.15). The highest values of soil C and N stocks we observed in the alder stand (64.61 and 2.68 t ha(-1), respectively) and the lowest amounts in the poplar stand (26.76 and 1.2 t ha(-1) respectively). The results of TOPSIS ranking indicated that, the preferred tree species are alder, chestnut-leaved oak, maple, polar and Mediterranean cypress, respectively. The findings of this study demonstrated that different planted tree species have different substantial effects on albedo and soil properties in the study region. Our results demonstrate the benefits of intercropped broad-leaved trees on albedo and soil C and N stocks. These findings may help to optimize forest management activities, such as selection of tree species in reforestations, plantations and agroforestry systems.