Document Type : Research Paper
In temperate ecosystems, degradation and restoration of vegetation cover can profoundly influence ecological processes, particularly soil properties and functions. Soil serves as a fundamental component of terrestrial ecosystems, regulating nutrient cycling, organic matter dynamics, microbial activity, and hydrological processes. Over recent decades, extensive deforestation, land-use change, and unsustainable exploitation of forest resources in northern Iran, especially within the Hyrcanian region, have resulted in substantial alterations in vegetation structure and composition. Vegetation degradation and subsequent restoration practices exert strong impacts on soil fertility by modifying organic matter inputs, microbial communities, and nutrient availability. Therefore, implementing integrated systems for monitoring soil fertility, particularly biological indicators, is essential for evaluating ecosystem health and restoration success. Among soil attributes, texture represents a key factor in assessing soil vulnerability across different land uses. Changes in soil texture induced by vegetation loss or recovery can influence other soil properties, thereby affecting runoff generation and erosion rates. Although numerous studies have addressed the effects of vegetation degradation and restoration on soil physical and chemical properties, relatively limited attention has been given to biological fertility indices and soil texture dynamics under different vegetation covers. Biological indicators such as microbial biomass carbon and soil respiration provide sensitive measures of soil quality and reflect ecosystem functioning more rapidly than conventional chemical parameters. Accordingly, the present study aimed to evaluate the effects of vegetation degradation and restoration on soil biological fertility indices and soil texture across seven land-use types in temperate Hyrcanian ecosystems. Specifically, this research sought to (i) compare soil texture-related indices and organic matter status among natural, degraded, and restored vegetation types; (ii) assess soil biological fertility at different depths; and (iii) identify relationships between biological indicators and organic matter content.
The study area is located in the western part of Mazandaran Province, within the Kelarabad regions. In this research, seven different land-use types were selected across the study region, including: (1) natural forest, (2) degraded forest, (3) afforestation with Alnus subcordata C. A. Mey., (4) afforestation with Acer insigne Boiss, (5) mixed afforestation with Alnus subcordata C. A. Mey.– Acer insigne Boiss, (6) afforestation with the non-native coniferous species Sequoia sempervirens (D. Don) Endl, and (7) grassland. Soil sampling was carried out during the summer of 2025. Within each vegetation type, three one-hectare plots (100 × 100 m) were established. In each plot, soil sampling was conducted at the four corners at three depths (0–10, 10–20, and 20–30 cm) within a 30 × 30 cm sampling area. In total, 36 soil samples were collected from three depths (0–10, 10–20, and 20–30 cm), with 12 samples obtained from each depth across the studied land uses. Samples were air-dried, sieved, and transferred to the laboratory for analysis. Soil texture fractions were determined using standard procedures, and indices such as clay ratio and modified clay ratio were calculated. Soil organic matter content was measured, and critical organic matter thresholds were assessed. Soil biological fertility was evaluated using indicators including basal respiration, cumulative respiration, and microbial biomass carbon. A composite biological fertility indices was derived by scoring individual biological parameters and summing their values to classify fertility status. All statistical analyses were performed using SPSS software (version 22). Statistical analyses were performed using analysis of variance (ANOVA) to test for significant differences among vegetation types and soil depths. Duncan’s multiple range test was applied to compare mean values at a significance level of p < 0.05. Principal component analysis (PCA) was employed to explore relationships among biological indicators, organic matter content, and critical organic matter levels.
The results revealed significant differences in soil texture-related indices among vegetation types. The highest values of clay ratio and modified clay ratio were observed in the grassland site, whereas the lowest values were recorded in the Acer insigne plantation. These findings indicate greater soil structural vulnerability in grassland areas compared to forested and restored sites. Regarding critical organic matter levels, the Sequoia plantation exhibited the highest values at the 0–10 and 10–20 cm depths, while the mixed Al. subcordata – Ac. insigne plantation showed the highest critical organic matter at the 20–30 cm depth. In contrast, grassland consistently displayed the lowest critical organic matter across all soil depthes, reflecting reduced organic inputs and limited biological activity. Assessment of soil biological fertility demonstrated clear variation among land uses and depths. At the surface layer (0–10 cm), natural forest and Al. subcordata plantation exhibited good fertility status, with total scores of 20 and 19, respectively. These sites were characterized by higher microbial activity and organic matter content. All other land uses, across all depths, fell within the moderate fertility category. Degraded forest and grassland showed comparatively lower biological scores, highlighting the negative impacts of vegetation removal on soil biological functioning. Principal component analysis indicated strong positive relationships between soil organic matter, critical organic matter level, and key biological indicators, including basal respiration, cumulative respiration, and microbial biomass carbon. These variables clustered closely, suggesting that organic matter availability plays a central role in regulating microbial activity and overall soil biological fertility.
The findings of this study demonstrate that vegetation degradation and restoration significantly influence soil biological fertility and texture-related indices in temperate Hyrcanian ecosystems. Natural forest and Al. subcordata plantations were particularly effective in enhancing soil biological quality, especially in surface layers, whereas grassland exhibited the poorest soil conditions. The strong associations between organic matter content and biological indicators underscore the importance of organic inputs in sustaining soil microbial processes. Based on the observed changes in soil biological fertility following degradation and restoration, it is recommended that biological fertility indices be incorporated alongside conventional soil properties as key criteria for evaluating the success of land restoration programs under similar ecological conditions. Moreover, planting Al. subcordata species appears to be a promising strategy for improving soil biological status and accelerating ecosystem recovery in degraded temperate landscapes.
This work is based upon reserch funded by Iran National Science Foundation (INSF), under Postdoc research project No 4038546.
Data collection: Fatemeh Heidari; software and validation: Fatemeh Heidari; writing—original draft preparation: Fatemeh Heidari; writing—review and editing: Yahya Kooch; supervision, project administration, and funding acquisition: Yahya Kooch, Fatemeh Heidari. All authors have read and approved the published version of the manuscript. All authors contributed equally to the conceptualization of the study and to the preparation of the initial and subsequent drafts.
No artificial intelligence tools were used in the article writing process.
Data available on request from the authors.
We would like to thank Tarbiat Modares University Research Office and the Iranian National Science Foundation (INSF) for their financial support in carrying out this research.
The authors declare no conflict of interest.
