Determination of the best canopy gap area on the basis of soil characteristics using the Analytical Hierarchy Process (AHP)

The assessment of canopy gap areas on the basis of soil characteristics in forest ecosystems could be one of benefit points for management of forests. This research was conducted in 20 ha areas of Experimental Forest Station of Tarbiat Modares University that is located in a temperate forest of Mazandaran province in the north of Iran. Twenty one canopy gaps with different areas were found in studied areas and classified as small (85.12 m2), medium (325.21 m2), large (512.11 m2) and very large (723.85 m 2) gaps. These areas classes of canopy gaps were assessed with respect to nine criteria (soil pH, carbon to nitrogen ratio, cation exchange capacity, phosphorus, potassium, calcium, nitrogen mineralization, microbial respiration and earthworm's biomass). Soil samples (0-45 cm depth from the gap center and edge positions) were measured in the laboratory. The Analytical Hierarchy Process (AHP) was used for assessment of canopy gap areas. This method is widely used the Multiple Criteria Decision Support (MCDS) method and perhaps the most popular in many fields, including natural resource management, especially in forest sciences. Results of AHP indicate that the maximum of local priority belongs to small areas of canopy gaps when considering all soil characteristics. However, medium, large and very large canopy gap areas have priorities, respectively. The calculated overall priority showed that with respect to considered criterias, small and medium gap areas have higher, more ideal condition in comparison to large and very large areas. AHP results emphasise that considering soil characteristics canopy gap areas should be less than 400 m2 in Hyrcanian forests of Iran. Also, AHP can be introduced as an effective instrument in decision-making processes for investment planning and prioritization in compliance with environmental regulations

Global data on earthworm abundance, biomass, diversity and corresponding environmental properties

14 p.Earthworms are an important soil taxon as ecosystem engineers, providing a variety of crucial ecosystem functions and services. Little is known about their diversity and distribution at large spatial scales, despite the availability of considerable amounts of local-scale data. Earthworm diversity data, obtained from the primary literature or provided directly by authors, were collated with information on site locations, including coordinates, habitat cover, and soil properties. Datasets were required, at a minimum, to include abundance or biomass of earthworms at a site. Where possible, site-level species lists were included, as well as the abundance and biomass of individual species and ecological groups. This global dataset contains 10,840 sites, with 184 species, from 60 countries and all continents except Antarctica. The data were obtained from 182 published articles, published between 1973 and 2017, and 17 unpublished datasets. Amalgamating data into a single global database will assist researchers in investigating and answering a wide variety of pressing questions, for example, jointly assessing aboveground and belowground biodiversity distributions and drivers of biodiversity change

Application of Statistical Method of Path Analysis to Describe Soil Biological Indices

Introduction: Among the collection of natural resources in the world, soil is considered as one of the most important components of the environment. Protect and improve the properties of this precious resource, requires a comprehensive and coordinated action that only through a deep understanding of quantitative (not only recognition of the quality) the origin, distribution and functionality in a natural ecosystem is possible. Many researchers believe that due to the quick reactions of soil organisms to environmental changes, soil biological survey to estimate soil quality is more important than the chemical and physical properties. For this reason, in many studies the nitrogen mineralization and microbial respiration indices are regarded. The aim of the present study were to study the direct and indirect effects of soil physicochemical characteristics on the most important biological indicators (nitrogen mineralization and microbial respiration), which has not been carefully considered up to now. This research is the first study to provide evidence to the future planning and management of soil sciences. Materials and Methods: For this, a limitation of 20 ha area of Experimental Forest Station of Tarbiat Modares University was considered. Fifty five soil samples, from the top 15 cm of soil, were taken, from which bulk density, texture, organic C, total N, cation exchange capacity (CEC), nitrogen mineralization and microbial respiration were determined at the laboratory. The data stored in Excel as a database. To determine the relationship between biological indices and soil physicochemical characteristics, correlation analysis and factor analysis using principal component analysis (PCA) were employed. To investigate all direct and indirect relationships between biological indices and different soil characteristics, path analysis (path analysis) was used. Results and Discussion: Results showed significant positive relations between biological indices and clay, organic carbon and total nitrogen, whereas the correlations of the other soil properties (bulk density, silt, sand and CEC) were insignificant. Factor analysis using of principle component analysis showed that the behavior of these two biological indices in the same territory and controlled by the same factors. Path analysis was employed to study the relationship among soil biological indices and the other soil properties. According to results, soil nitrogen mineralization is more imposed by nitrogen (0.98) and organic carbon (0.91) properties as direct and indirect effects respectively. Whereas the values of soil microbial respiration were affected by organic carbon (0.89) and total nitrogen (0.81). It can be claimed that total nitrogen and organic carbon are the most important soil properties in relation to nitrogen mineralization and microbial respiration, respectively. Regarding to the strong relationship between soil organic carbon and nitrogen and also similarly strong relationship between nitrogen and organic carbon mineralization, enhancing nitrogen mineralization is expected by the increase in organic carbon. In this regard, Nourbakhsh, et al. (2002) claimed that nitrogen mineralization is depended to soil organic nitrogen and derived from total nitrogen. In addition, there is a strong relationship between total nitrogen and soil organic carbon. So, the greater amounts of nitrogen mineralization can be related to more accumulation of organic carbon and nitrogen in topsoil (23). This result is in accordance with Wood, et al. (1990) and Norton, et al. (2003) findings (21, 30). Ebrahimi, et al. (2005) stated that if the C/N ratio is more than 30, the process immobility or nitrogen mineralization stopwill be occurred. The ratios between 20 and 30 usually settle and release of mineral nitrogen does not take place, and the balance remains. If the C/N ratio is less than 20 net release of nitrogen in the soil will increase (9).In the present study, the values of soil C/N ratio were less than 20 (mean 15.80), so the process of nitrogen mineralization occurred in the study area. Suitable conditions for microbial activity of soil microorganism's especially adequate supply of organic carbon increased the microbial respiration in the study area. High correlation between the amount of organic carbon and microbial respiration confirmed this claim. However; it seems that the soil organic carbon is driver of microbial respiration rate. This finding is reported by different researchers (6, 7, 15, and 20). Conclusion: Path analysis as a complementary method of regression analysis and factor analysis using principal component analysis showed that the biological activity of the soil characteristics are directly affected by soil nitrogen (for nitrogen mineralization index) and organic carbon (for microbial respiration index) and other useful features influence them indirectly through strong correlation with the characteristics of nitrogen and organic carbon in soil

Pit and mound influence on soil features in an Oriental Beech (Fagus orientalis Lipsky) forest

Windthrow, i.e. the felling of trees by wind, occurs continually in forest ecosystems. The uprooting of old trees creates multiple microsites (e.g. pit and mound landscape) that are the main source of soil heterogeneity. To determine the impact of pit and mound landscapes on soil features, a beech forest of the Langa district (Mazandaran province, Northern Iran) was studied. An area of 25 ha was considered for this study wherein three microsites were distinguished, including pit bottom (pit), mount top (mound) and level areas (closed canopy). In this area, 22 uprooted trees were also found. Soil samples were collected at different depths (i.e. 0\u201315, 15\u201330 and 30\u201345 cm) from all microsites and analysed. Our study shows that windthrow events should be considered as an important factor in influencing forest ecosystem, as they affect physical (i.e. density, texture and water content), chemical (i.e. pH, organic C, total N, cation exchange capacity and available nutrients) and biological (i.e. soil microbial respiration and earthworm density/biomass) characteristics of soil, thus resulting in pit and mound microsites that may strongly differ with respect to the closed canopy