Changes in Soil’s Chemical and Biochemical Properties Induced by Road Geometry in the Hyrcanian Temperate Forests

Saeid Rahbarisisakht,Seyed Mohammad Moein Sadeghi,Stelian Alexandru Borz,Inger Kappel Schmidt,Sebastian Kepfer-Rojas,Mohammad Hadi Moayeri,Elyas Hayati,Mohammad Hadi Pahlavani

doi:10.3390/f12121805

Abstract

Forest roads play an important role in providing access to forest resources. However, they can significantly impact the adjacent soil and vegetation. This study aimed to evaluate the effects of road geometry (RG) on the chemical and biochemical properties of adjacent soils to assist in environmentally friendly forest road planning in mountainous areas. Litter layer, canopy cover, soil organic carbon (SOC) stock, total nitrogen (TN), the activity of dehydrogenase (DHA), and urease (UA) enzymes at a 0–20 cm soil depth were measured by sampling at various distances from the road edge to 100 m into the forest interior. The measurements were done for three road geometries (RG), namely straight, curved, and bent roads, to ensure data heterogeneity and to reflect the main geometric features of the forest roads. Analysis of variance (ANOVA) showed that the effects of RG on the measured variables were statistically significant. Spearman’s correlation test clearly showed a strong positive correlation between environmental conditions, SOC, TN, DHA, and UA for given RGs. Based on piecewise linear regression analysis, the down slope direction of the straight and the inside direction of bent roads accounted for the lowest and highest ranges of ecological effects, respectively. The results of this study contribute to our understanding of the environmental effects brought about by road geometry, which can be important for forest road managers when applying the best management practices.

Highlights

Transportation infrastructure is an integral and inseparable element of development and growth, it directly impacts the structure and functioning of the surrounding ecosystems
This study aimed to evaluate the effects of road geometry (RG) on the chemical and biochemical properties of adjacent soils to assist in environmentally friendly forest road planning in mountainous areas
Due to the important role that soil enzymes are playing in the energy transfer via the decomposition of organic matter and nutrient cycling [31], they are often used as a measure of disturbances, such as those related to environmental conditions and forest management practices, and as a direct measure of the soil microbial activity [32]

Summary

Introduction

Transportation infrastructure is an integral and inseparable element of development and growth, it directly impacts the structure and functioning of the surrounding ecosystems. As an essential part of the ecosystem for vegetation development, forest soil is influenced by climate, plants, and animal species that control its physical, chemical, hydrological, and biological properties, and by engineering activities such as road construction and forest operations [4,15,16]. These activities directly or indirectly affect forest soil properties by changing the microclimate on adjacent areas [17]. Due to the important role that soil enzymes are playing in the energy transfer via the decomposition of organic matter and nutrient cycling [31], they are often used as a measure of disturbances, such as those related to environmental conditions and forest management practices, and as a direct measure of the soil microbial activity [32]

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Conclusion