بومشناسی جنگلهای ایران (May 2024)
The Effect of Pure and Mixed Norway Spruce (Picea abies L.) Afforestationon Some Soil Physical and Chemical Characteristics
Abstract
Extended Abstract Background: Afforestation has been growing worldwide in recent decades and is expected to continue in this trend due to the increased use of wood. Therefore, the mass planting of pine trees and other fast-growing species for industrial wood production has intensified since the beginning of the 20th century. In Iran, with a low forest per capita (0.17 ha), per capita plans to create a forest and rehabilitate degraded forests to increase green space have been implemented with non-native species. For this reason, many non-native conifer species have been introduced to the country, which has not been successful in some areas. Therefore, for the success of afforestation with non-native species, it is necessary to select those that are suitable for the habitat conditions, adapt the ecological needs to the environment, and consider the effect of afforestation on the soil, understory plants, and living organisms. Ensuring sustainable management depends on knowing the effects of planted tree species on species diversity, structure, and ecosystem function. Since different tree species have different effects on soil characteristics in ecosystems, they can change soil properties with different mechanisms. In other words, the differences in litter quality, the state of nutrients, the performance of roots in nutrient uptake, the leaf structure, the crown of the tree, the microclimate under the crown, and finally the biological communities in different tree populations change the soil physicochemical properties. In general, the restoration of degraded forest lands through afforestation has a significant effect on the variability of soil characteristics, in which a major difference is observed between native and non-native species as well as broadleaf and coniferous species. Since broad-leaved tree species can positively affect the soil quality of conifer stands, this research aims to compare some soil physicochemical characteristics under the influence of pure and mixed Norway spruce (Picea abies L.) afforestation. Methods: The studied area is in the southeast of section 101 of the Makarood series, watershed 36 (Kazemroud) in Kalardasht city and at an approximate height of 1200 m. It includes the afforested areas of pure Norway spruce (PS) (2 ha), mixed Norway spruce (MS) (2.5 ha) forestry areas, and barren land (BL) (3 ha). Three transects in each area were planned due to the smallness of the areas and the need to adopt a method that best describes the condition of the soil in each area. Then, on the 10, 50, and 90 m points of the transects, soil samples were taken in layers of 0-10 and 10-30 cm (in each area, nine soil samples for each layer). The texture, saturation percentage (SP), electrical conductivity (EC), pH, neutralizing substances or lime (T.N.V), organic carbon (O.C), nitrogen (N), phosphorus (P), potassium (K), and bulk density (BD) was examined in the laboratory. Results: The bulk density was lower in the 0-10 cm layer in the MS stand (2.28 g/cm3) than in the other two areas. The soil saturation was higher in the upper layer in the PS stand (85.77%) than in the MS stand (59.83%) and BL (51.07%). On the contrary, it was greater in the lower layer of the BL (94.40%) than in the two forest stands. EC values were lower in both upper (0.40 ds/m) and lower (0.38 ds/m) layers in the BL than that in PS and MS stands. The pH was significantly lower in the 0-10 cm layer in the PS (4.84) and MS (4.88) stands than in the BL (5.75). In each of the three areas, the amount of lime was zero in the upper and lower layers. O.C. in the upper layer was significantly higher in the PS (2.57%) and the MS (2.96%) stands than in the BL (1.45%), and the highest value was measured in the MS stand (0.94%) in the lower layer. Nitrogen was higher in the upper layer of PS (0.197%) and MS (0.270%) stands than that in the BL (0.143%). It was higher in the lower layer of the MS stand (0.09%) than the PS (0.02%) and BL (0.03%) stands. The C/N was highest in the upper layer in the PS stand (12.97), but this ratio was not significantly different in the lower layer of the three areas (10.82-11.50). The amount of P was highest in the upper layer in the MS stand (8.4 ppm), but no significant difference in P was detected in the lower layer among the three areas (3.57-5.60 ppm). K content was higher in the upper layer of the PS stand (203.43 ppm), but it was higher in the BL (193.50 ppm) in the lower layer than in the two forest stands. Conclusion: In the upper soil layer (0-10 cm), pH, C, and N values did not differ between MS and PS stands, but BD and C/N were lower in the MS stand; on the contrary, soil porosity and P and K contents were higher than those in the PS stand. From this research, it is generally concluded that afforestation with MS has a better effect on the optimization of physical and chemical characteristics in the soil layers than PS, which can provide the basis for more suitable growth of trees and a better balance of the forest.
