Yahya Kooch *1, Zahra Mohmedi Kartalaei1, Mojtaba Amiri2, Mehrdad Zarafshar3, Saeid Shabani4, Majid Mohammady2
1- Faculty of Natural Resources & Marine Sciences, Tarbiat Modares University, Noor, Iran
2- Faculty of Natural Resources, Semnan University, Semnan, Iran
3- Fars Agricultural and Natural Resources Research and Training Center, Fars, Iran
4- Golestan Agriculture and Natural Resources Research and Education Center, Golestan, Iran
2- Faculty of Natural Resources, Semnan University, Semnan, Iran
3- Fars Agricultural and Natural Resources Research and Training Center, Fars, Iran
4- Golestan Agriculture and Natural Resources Research and Education Center, Golestan, Iran
Abstract: (767 Views)
Extended Abstract
Background: In dry ecosystems, especially in arid and semi-arid regions, which are fragile and vulnerable ecosystems, forest destruction and land use change are considered one of the most important factors affecting the variability of soil characteristics. In this regard, soil respiration, as the main carbon control process in underground processes, is correlated with soil microbial activity, availability of different substrates, soil nutrient content, root dynamics, soil temperature, and moisture, and is considered a good indicator to estimate the productivity of ecosystems. The long-term consequences of land degradation, soil properties, and microbial respiration, which significantly affect global carbon dioxide emissions, are not fully understood. Thus, this study aimed to investigate the effects of forest destruction and land use change on the physical, chemical, and respiration properties of soils in semi-arid mountain ecosystems.
Methods: The current investigation was conducted in the mountainous area of Mikhsaz, Kajur village, which is a part of the Nowshahr City region situated in Mazandaran Province, Northern Iran. The altitude ranges from 1600 to 1700 meters above sea level, with a slope gradient of 10-20%. The area experiences an annual precipitation of 365 mm and a mean annual temperature of 11˚C. Soils are clay loam and are classified under the Alfisoils order according to the Soil Taxonomy (United States Department of Agriculture, 2014). The examined region has the potential for forests (including Carpinus orientalis Mill. and Quercus macranthera F&M.) and rangelands (including Artemisia aucheri Boiss. and Astragalus podolobus Boiss. & Hohen). The study area was predominantly covered with forests, but it has been transformed into three distinct uses, forest, forest-woodland, and rangeland due to human activities during the last 30 years. In each of the studied uses (forest, woodland, and rangeland), four sample plots with an area of four hectares (200 × 200 meters) were considered at a distance of 4-6 km from each other. The selected areas were similar in terms of bedrock (dolomite limestone), physiography (average height of 1650 meters above sea level, the slope of the area between 10 and 15%, and the dominant geographical direction northward), climatic conditions (cold mountains), and management conditions (without human intervention, fertilization, and livestock grazing). The soil was sampled (in an area of 30 × 30 cm from two depths of 0-15 and 15-30 cm) from four corners and the center of each of the sample pieces in summer. In total, five samples were collected in each sample plot, and a total of 20 soil samples were collected from each depth of 0-15 and 15-30 cm in each land cover. To investigate the difference or non-difference of the values of the studied characteristics in the studied habitats, a split-plot design was used for physical and chemical characteristics, and the one-way analysis of variance (ANOVA) was used for biological characteristics with SPSS version 20 software. To determine the relationship between vegetation and soil respiration, graphs were drawn using Excel software.
Results: Examining the changes in the physical and chemical characteristics of the soil showed significant differences in the characteristics of micro-aggregate, macro-aggregate, soil stability, weighted mean diameter of soil aggregates, carbon in micro-aggregate, carbon in macro-aggregate, the ratio of carbon in micro to macro-aggregate, nitrogen in micro-aggregate, nitrogen in macro-aggregate, carbon to nitrogen ratio in micro-aggregate, carbon to nitrogen ratio in macro-aggregate, dissolved organic carbon, dissolved organic nitrogen, and dissolved organic matter among three land uses. Moreover, micro-aggregate, macro-aggregate, weighted mean diameter of soil aggregates, carbon in micro-aggregate, carbon in macro-aggregate, nitrogen in micro-aggregate, nitrogen in macro-aggregate, the ratio of nitrogen in micro to macro soil, and dissolved organic matter, carbon and nitrogen showed significant differences in the two soil depths. The results of the changes in soil elements in relation to soil carbon and nitrogen characteristics in three uses of forest, woodland, and rangelands showed that nitrogen in micro-aggregate (0.13, 0.09, 0.05 %), nitrogen in macro-aggregate (0.32, 0.16, 0.08 %), dissolved organic carbon (52.16, 38.05, and 18.41 g kg-1), and dissolved organic nitrogen (27.23, 17.85, and 12.9 g kg-1) showed significant differences (p < 0.05) between the three uses in the first soil depth. The results of soil microbial characteristics showed that the substrate-induced respiration in all the treatments used in forest land use was significantly (p < 0.05) higher than the other two land covers.
Conclusion: The findings of this study indicate that the physical, chemical, and biological soil properties are influenced by above-ground vegetation, particularly in the topsoil layer. Therefore, the removal of vegetation can lead to significant deterioration of soil properties in semi-arid regions. Considering that the soil in semi-arid areas is highly susceptible to destruction, the reduction and destruction of vegetation play an important role in intensifying these effects and influencing the provision of ecosystem services in such areas. Furthermore, the relationship between soil respiration and carbon dioxide emissions is intrinsically linked to climate change. The results of this research also emphasize that the conversion of forest areas to other ecosystems has led to changes in the carbon and nitrogen cycle and soil microbial respiration. The results of this research can contribute to the development of sustainable management and restoration programs for degraded areas in similar climates because the high quality of the soil of these forests indicates the high potential of woody vegetation (especially Carpinus orientalis Mill. and Quercus macranthera F&M.) for soil protection and biodiversity. These findings can be the basis for designing educational programs for local communities to preserve natural ecosystems by preventing land use changes and rehabilitating degraded areas. In general, these studies can help improve environmental, economic, and social conditions in different regions. Finally, this study emphasizes the urgent need to use sustainable management practices to prevent further degradation and promote the implementation of restoration techniques in degraded forests.
Background: In dry ecosystems, especially in arid and semi-arid regions, which are fragile and vulnerable ecosystems, forest destruction and land use change are considered one of the most important factors affecting the variability of soil characteristics. In this regard, soil respiration, as the main carbon control process in underground processes, is correlated with soil microbial activity, availability of different substrates, soil nutrient content, root dynamics, soil temperature, and moisture, and is considered a good indicator to estimate the productivity of ecosystems. The long-term consequences of land degradation, soil properties, and microbial respiration, which significantly affect global carbon dioxide emissions, are not fully understood. Thus, this study aimed to investigate the effects of forest destruction and land use change on the physical, chemical, and respiration properties of soils in semi-arid mountain ecosystems.
Methods: The current investigation was conducted in the mountainous area of Mikhsaz, Kajur village, which is a part of the Nowshahr City region situated in Mazandaran Province, Northern Iran. The altitude ranges from 1600 to 1700 meters above sea level, with a slope gradient of 10-20%. The area experiences an annual precipitation of 365 mm and a mean annual temperature of 11˚C. Soils are clay loam and are classified under the Alfisoils order according to the Soil Taxonomy (United States Department of Agriculture, 2014). The examined region has the potential for forests (including Carpinus orientalis Mill. and Quercus macranthera F&M.) and rangelands (including Artemisia aucheri Boiss. and Astragalus podolobus Boiss. & Hohen). The study area was predominantly covered with forests, but it has been transformed into three distinct uses, forest, forest-woodland, and rangeland due to human activities during the last 30 years. In each of the studied uses (forest, woodland, and rangeland), four sample plots with an area of four hectares (200 × 200 meters) were considered at a distance of 4-6 km from each other. The selected areas were similar in terms of bedrock (dolomite limestone), physiography (average height of 1650 meters above sea level, the slope of the area between 10 and 15%, and the dominant geographical direction northward), climatic conditions (cold mountains), and management conditions (without human intervention, fertilization, and livestock grazing). The soil was sampled (in an area of 30 × 30 cm from two depths of 0-15 and 15-30 cm) from four corners and the center of each of the sample pieces in summer. In total, five samples were collected in each sample plot, and a total of 20 soil samples were collected from each depth of 0-15 and 15-30 cm in each land cover. To investigate the difference or non-difference of the values of the studied characteristics in the studied habitats, a split-plot design was used for physical and chemical characteristics, and the one-way analysis of variance (ANOVA) was used for biological characteristics with SPSS version 20 software. To determine the relationship between vegetation and soil respiration, graphs were drawn using Excel software.
Results: Examining the changes in the physical and chemical characteristics of the soil showed significant differences in the characteristics of micro-aggregate, macro-aggregate, soil stability, weighted mean diameter of soil aggregates, carbon in micro-aggregate, carbon in macro-aggregate, the ratio of carbon in micro to macro-aggregate, nitrogen in micro-aggregate, nitrogen in macro-aggregate, carbon to nitrogen ratio in micro-aggregate, carbon to nitrogen ratio in macro-aggregate, dissolved organic carbon, dissolved organic nitrogen, and dissolved organic matter among three land uses. Moreover, micro-aggregate, macro-aggregate, weighted mean diameter of soil aggregates, carbon in micro-aggregate, carbon in macro-aggregate, nitrogen in micro-aggregate, nitrogen in macro-aggregate, the ratio of nitrogen in micro to macro soil, and dissolved organic matter, carbon and nitrogen showed significant differences in the two soil depths. The results of the changes in soil elements in relation to soil carbon and nitrogen characteristics in three uses of forest, woodland, and rangelands showed that nitrogen in micro-aggregate (0.13, 0.09, 0.05 %), nitrogen in macro-aggregate (0.32, 0.16, 0.08 %), dissolved organic carbon (52.16, 38.05, and 18.41 g kg-1), and dissolved organic nitrogen (27.23, 17.85, and 12.9 g kg-1) showed significant differences (p < 0.05) between the three uses in the first soil depth. The results of soil microbial characteristics showed that the substrate-induced respiration in all the treatments used in forest land use was significantly (p < 0.05) higher than the other two land covers.
Conclusion: The findings of this study indicate that the physical, chemical, and biological soil properties are influenced by above-ground vegetation, particularly in the topsoil layer. Therefore, the removal of vegetation can lead to significant deterioration of soil properties in semi-arid regions. Considering that the soil in semi-arid areas is highly susceptible to destruction, the reduction and destruction of vegetation play an important role in intensifying these effects and influencing the provision of ecosystem services in such areas. Furthermore, the relationship between soil respiration and carbon dioxide emissions is intrinsically linked to climate change. The results of this research also emphasize that the conversion of forest areas to other ecosystems has led to changes in the carbon and nitrogen cycle and soil microbial respiration. The results of this research can contribute to the development of sustainable management and restoration programs for degraded areas in similar climates because the high quality of the soil of these forests indicates the high potential of woody vegetation (especially Carpinus orientalis Mill. and Quercus macranthera F&M.) for soil protection and biodiversity. These findings can be the basis for designing educational programs for local communities to preserve natural ecosystems by preventing land use changes and rehabilitating degraded areas. In general, these studies can help improve environmental, economic, and social conditions in different regions. Finally, this study emphasizes the urgent need to use sustainable management practices to prevent further degradation and promote the implementation of restoration techniques in degraded forests.
Keywords: Aggregate stability, Forest, Land use change, Soil properties, Substrate induced respiration
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