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.
., Moayeri, M. H. and Arp, P. A. 1998. Modeling potentially sustainable biomass productivity in jack pine forest stands. Can. J. Soil Sci. 78: 105-113. A steady-state mass balance model (ForSust), developed to simulate potentially sustainable levels of tree biomass growth and related nutrient uptake dynamics, was applied to 17 jack pine sites across Canada. The model simulates potential tree biomass growth based on nutrient inputs from estimated atmospheric deposition (N, Ca, Mg, K) and soil weathering (Ca, Mg, K), and matches the resulting nutrient supply rates with calculated nutrient demand. Nutrient demand calculations are based on nutrient concentrations in wood, bark, branches, and foliage. Specifically, the model simulates sustainable annual increment (SAI) of biomass growth for stem-only and whole-tree (aboveground biomass) harvesting, and for recurring forest fire conditions. Calculated SAI levels were compared with field-estimated mean annual increments for aboveground forest biomass (MAI). For recurring forest fires, it was found that SAI values, as simulated, corresponded with the MAI field estimates in general. For whole-tree harvesting, SAI was lower than MAI for most but not all sites. For stem-only harvesting, SAI corresponded with MAI, but there was a greater scatter between SAI and MAI values than what appeared to be the case for the recurring forest fire scenario.
Stand structure is a key principle in stand biodiversity. High biodiversity was associated with the stands that have different trees species with different dimension. In this regard, for evaluation Structural diversity in different diameter and height classes and also their changing procedure of beech stands in north of Iran, 30 modified Whittaker plots by systematic random system were located. The heterogeneity indices of Shannon–Wiener, number of equally common species and evenness indices of Simpson and smith-Wilson were using for the quantitative data. In order to understand the diversity condition in horizontal and vertical composition of stand further, the diameter divided in 10-cm classes and method of Mohajer and the height divided in 10-m height classes and dominant height. Then diversity of each class was extract by ecological methodology software. Results showed the most diversity of trees and shrubs is in low height and diametrical classes. Thus, the study of biodiversity changes in different diameter and height category cause ecologically precise perspective in management of forest stands.
For comparison purposes, two methods are proposed for mapping sustainable acid deposition within the context of natural and managed (harvested) forest biomass growth in Northeastern North America. One method uses existing geospatial data for forest cover type, soil type, local climate, topography, and atmospheric deposition. The other method uses data specific to well‐studied sites. Maps will be developed that show the spatial distributions of sustainable acid deposition rates by tree type, eco‐unit, and local forest disturbance regimes (by harvest method). Additional maps will be produced to show where these rates are likely exceeded, and by how much. The information so generated will be presented to policy and decision makers who deal with forest health and abatement control measures regarding regional sulfur (S) and nitrogen (N) emissions.
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