Effect of Planting Cupressus sempervirens in the Natural Broadleaf Forests on the Physical and Chemical Properties of the Soil (Case Study: Pilambra Forest of Paresar, Gilan)

Background and Objectives: One of the major challenges in managing the forests is selecting suitable species for afforestation and restoration of degraded areas. Coniferous species such as Cupressus sempervirens have received attention in recent years due to their unique characteristics. On the other hand, conversion of natural broadleaf forests to coniferous forests may cause changes in the physical and chemical properties of the soil. The aim of the present study is to compare the physical and chemical properties of soil in three areas including pure coniferous stand, natural broadleaf stand, and mixed broadleaf and coniferous stand in the Pilembra forest of Paresar, Gilan province. This study was conducted with the aim of making decisions about expanding afforestation with the species Zerbin. Studying soil changes in these areas can provide useful information for improving forest management in the region. Studying soil changes in these areas can provide useful information for improving forest management in the region. Usually, effect of broadleaf or coniferous species on soil properties has been studied separately, but it has been less common to study a pure broadleaf stand and a pure coniferous stand simultaneously alongside a mixed stand of these two species.
Materials and Methods: The geographical area under the study is located 73 kilometers from Rasht city in Gilan province. The minimum and maximum altitudes above sea level are 80 and 118 meters, respectively, and the average slope of the area is 8 percent. For this study, three linear transects, each 200 meters long with sampling intervals of 10 meters, were established. Sampling was conducted from the soil depth of 15 to 20 cm. The samples were transferred to the laboratory, and after preparation, soil factors such as pH, electrical conductivity (EC), soil texture, available phosphorus and potassium, bulk density, and organic carbon were measured. Duncan and Tukey statistical tests were used to compare the data between the three regions.
Results: Results of the study indicated that physical and chemical properties of the soil varied significantly across the three regions. The soil pH was highest in the broadleaf region and lowest in the needleleaf region. Electrical conductivity (EC) in the mixed region was intermediate between the other two regions. Bulk density also showed a significant difference across the three regions. The organic matter content was similar in the needleleaf and mixed regions, while the lowest potassium content was observed in the mixed region. Additionally, the highest phosphorus content was found in the mixed region, and the lowest was recorded in the needleleaf region. The nitrogen content was highest in the broadleaf region, whereas the lowest was observed in the mixed region. In terms of soil texture composition, the clay percentage was higher in the broadleaf region compared to the other two regions, while the sand percentage was highest in the needleleaf region.
Conclusion: According to the results obtained in this study, it can be said that pure coniferous planting has a negative impact on the soil of the research area, but its impact is desirable and acceptable when mixed with broadleaf forest. It should be noted that other indicators, in addition to this research topic, such as ecosystem conditions, regional plant competition, presence of pests and natural disasters, forest economics and environmental actions, as well as the discussion of water exchange, should be considered in order to provide a more precise opinion on how to plant the Zerbin species.