Heuristic planning techniques applied to forest road profiles

Two heuristic techniques, the genetic algorithm (GA) and Tabu search (TS), both with an embedded linear programming routine for earthwork allocation, were compared to a manually designed forest road profile. The manually designed road length was 345.7m and its average gradient was 14.1%. The best costs of the profiles designed by GA and TS, without changing the placement of control points, were less than that designed manually. The best cost found by GA was almost the same as the global optimum solution. While TS could not find a better solution than GA, it usually found a good solution in less time. It was not possible to search all alternatives by changing the placement of control points and find the global optimum solution within a reasonable time. However, it can be concluded from the results that both GA and TS found good solutions within a reasonable time. Since it is not possible to manually evaluate many alternatives, road designers should find heuristic techniques helpful for design of the road profile. Moreover, the effect of the number of control points on construction costs was examined. The results indicated that increasing the number of control points reduces the construction costs. However, driving safety and comfort might be decreased.     

Analysis of current forest operations in the Okumikawa Forestry Area by location and topography

We analyzed current forest operations in Toei, in the Okumikawa Forestry Area, Japan, by examining actual achievement, location, and topography. We considered five basic forest operations conducted by the Forest Owners Association between 1991 and 2000 in a subsidized reforestation and silviculture project: planting, weeding, pruning, cleaning, and thinning. In addition, we considered the road network, including public, forest, and strip roads. The area in which forest operations have been conducted over the past 10 years amounted to less than two-thirds of the area targeted in the Toei Forest Improvement Plan. The mean access distance of the work sites was 164m, which was 52m less than the 10-year average for the whole forest (216m). Forest operations tended to ignore remote forest areas where the topography was steep, due to cost, the logging techniques required, and labor requirements. We determined that the limitations on forest operations in Toei were a 300m access distance, an elevation of 800masl, and a 90% slope. In accessing work sites, the utilization ratios of forest and strip roads were higher than their composition ratios, and public roads were used most. Newly constructed strip roads were used more than forest roads. Based on current forest operations, we calculated the road density and length required to be 7.1m/ha and 79.2km, respectively, with an estimated cost exceeding 720 million yen for new construction.     

Comparing the precision and accuracy of GPS positioning in forested areas

The objective of this study is to clarify the performance of the Global Positioning System (GPS) in forested areas after selective availability (SA) was turned off. In this study, we conducted a field test on horizontal and vertical positional errors of GPS positioning at different points in forested areas. The precision and accuracy of GPS positioning at different points were then calculated and compared. Furthermore, the effect of differential GPS (DGPS) on precision and accuracy was analyzed using analysis of variance (ANOVA), and the necessity for DGPS after SA was turned off was discussed. As a result, the largest horizontal precision errors were found to be in the plantation forest, followed by the natural forest and forest road. On the other hand, precision errors were smallest at the landing, around which there were no obstacles. Horizontal accuracy errors were greatly improved by using the DGPS. Large vertical precision errors were produced in the plantation forest, on the forest road, and in the natural forest, while those at the landing were much smaller. Vertical accuracy errors were also relatively small at the landing. In conclusion, tree canopies greatly affected precision errors, and the DGPS improved not horizontal precision but horizontal accuracy. The autonomous GPS is sufficiently useful for purposes in which horizontal positional errors of a maximum of 10m are allowable. However, the DGPS should be used for surveying and mapping, for which higher accuracy is necessary.     

Tabu search optimization of horizontal and vertical alignments of forest roads

This article describes a program for optimizing horizontal and vertical alignments of forest roads using Tabu search, a modern heuristic technique. Once a series of intersection points (IPs) is selected manually, the program generates alternative horizontal and vertical alignments. The program precisely generates ground profile and cross sections using a high-resolution digital elevation model (DEM) derived from light detection and ranging (LiDAR) data. It accurately calculates earthwork volumes for curved roadways using the Pappus-based method. The program also estimates construction and maintenance costs. Tabu search optimizes forest road alignments based on the total costs. The application of the program to part of Capitol State Forest in Washington State, USA, indicated that the program successfully found better alignments than manually selected initial alignments. The effect of initial solutions and the number of iterations on the Tabu search process was examined. The result showed that the solutions were improved using the best solutions with the smaller number of grade change points as the initial solutions. It also showed that a small number of iterations could be used to reduce computation time due to the fact that Tabu search is based on a gradient search technique. Finally, the Dijkstra method was examined to find initial solutions without manually initialized solutions. The program, when combined with the Dijkstra method, could find similar-quality solutions from manually initialized solutions. The program will become useful with further tests and verifications.     

Canopy cover effects on nitrogen and phosphorus status in understory vegetation in oak and pine stands

The rate of change of leaf mass, N and P levels in understory vegetation at various levels of canopy cover were measured for 2 years following canopy cover manipulations in northern red oak (Quercus rubra L.) and red pine (Pinus resinosa Ait.) stands in northern Lower Michigan, USA. Canopy cover treatments consisted of clearcut, 25% (50% during first sampling year), 75%, and uncut. Leaf mass, and N and P contents were significantly higher in the clearcut treatment than in other canopy cover treatments, except for the 25% treatment in red pine stands. Leaf N concentrations in understory vegetation were also significantly higher in the clearcut (1991, 20.8mgg^–1; 1992, 22.4mgg^–1) than in the uncut treatment (1991, 16.5mgg^–1; 1992, 16.9mgg^–1). Canopy type (northern red oak and red pine) had little influence on understory nutrient status and leaf mass. In addition, fronds of bracken ferns in all canopy cover treatments in both northern red oak and pine stands were a major sink of nutrients in the understory. The results of this study showed that partial canopy removal generally had only a minor impact on understory leaf production and nutrient status compared with clearcuts during the 2-year period following canopy removal.     

Vibrational properties of wood plastic plywood

Wood plastic plywood (WPPW), composed of veneer and styrofoam, was manufactured without special adhesives such as urea–formaldehyde or phenol–formaldehyde resins, and its vibrational properties were investigated. WPPW can be produced at 1MPa and 160°C for 9min (three-ply) and 12min (five-ply). The dynamic Youngs modulus reached its highest value when the styrofoam thickness was 30mm. The sound velocity and dynamic Youngs modulus had minimum values at a grain angle of 45°. The results for dynamic Youngs moduli measured by a longitudinal vibration method and an in-plane flexural vibration method were almost the same. Dynamic shear moduli were measured by an in-plane surface wave propagation test and an in-plane flexural vibration method. From the experimental results, the dynamic shear moduli at 0° and 90° by the two methods were relatively close, although the surface wave propagation test results were higher than those from the flexural vibration method. Dynamic shear moduli at a grain angle of 45° measured by the in-plane surface wave propagation test and calculated from theory were relatively close. The surface wave propagation test results were smaller than the results calculated from theory. The shear stress distribution factors were about 1.000–1.189 for WPPW.     

Porewater dynamics and the formation of iron sulfides in a mangrove ecosystem,Sepetiba Bay,Brazil

Porewater dynamics and the formation of iron sulfides were studied in the Brazilian mangrove. Porewater samples were collected during tidal cycles using in situ equipment and physical–chemical and chemical data were obtained. The advective transport of porewater by tidal currents was found to be more effective between 0 and 5cm depth than below 15cm. The diffusive input of atmospheric oxygen during low tides resulted in oxidation of porewater dissolved sulfides. Thermodynamic considerations identified pyrite as the main iron sulfide forming at this depth, and the amorphous iron hydroxides are probably the main iron source. Below 15cm depth, irregular root distribution underground and benthic faunal bioturbation caused considerable spatial variation in a small scale (20cm). The correlation between alkalinity and total dissolved sulfide suggests that the main pathway for organic matter decomposition is sulfate reduction. Formed in the highly sulfidic diagenetic zone, the dissolved iron went through iron sulfide formation process. Crystalline iron oxides like hematite and magnetite may constitute an important iron source below 15cm, whereas pyrite is still the most probably occurring iron sulfide, according to thermodynamic considerations.     

Changes in the physical and chemical properties of six Japanese softwoods caused by lengthy smoke-heating treatment

The effects of prolonged smoke-heating treatments on wood quality were investigated. Six Japanese softwoods were smoke-heated for 100 and 200h at a temperature of 75° ± 5°C, which was recorded inside the log. After smoke heating, wood quality, including moisture content, amounts of chemical components, relative degree of crystallinity (RDC) of cellulose, and sapwood color were examined. Moisture content decreased as a result of smoke heating, especially in sapwood, leading to a uniform distribution of moisture content within a log. Almost no difference was found in the amounts of chemical components between the control woods and the woods that were smoke-heated for 100h. However, in the wood that was smoke-heated for 200h, the amounts of holocellulose decreased, suggesting that thermal deterioration and/or degradation of hemicelluloses had occurred. We assume that the increase in RDC was caused by smoke heating with the crystallization of cellulose and/or thermal degradation of hemicelluloses. Almost no differences were found in sapwood color between the control woods and the woods that were smoke-heated for 100h. In the wood that was smoke-heated for 200h, however, L*decreased, whereas a* and b* increased. As a result, E*ab, showing the total color change, increased, resulting in a deeper color. These results suggest that thermal degradation of hemicelluloses was caused by smoke heating for over 100h. Therefore, smoke heating of softwood logs using a commercial-scale kiln should not exceed 100h.     

Estimating individual tree heights of sugi (Cryptomeria japonica D. Don) plantations in mountainous areas using small-footprint airborne LiDAR

Recently, it was shown that individual tree heights could be accurately estimated using small-footprint airborne light detection and ranging (LiDAR) remote sensing. Because most of the areas studied previously were limited to flat terrain, we investigated the accuracy of LiDAR-derived individual tree height estimates for different types of topographical features in mountainous forests with a steeper and more complex topography. Several middle-aged (40–50 years old) sugi (Cryptomeria japonica D. Don) plantations are found in the mountainous regions in Japan; hence, we chose 48-year-old sugi plantations to investigate the accuracy of these estimates. The surveyed area was divided into three types of topographical features; steep slope (mean slope ± SD; 37.6° ± 5.8°), gentle slope (15.6° ± 3.7°), and gentle yet rough terrain (16.8° ± 7.8°). Before estimating tree heights, the number of detected trees within each topographical feature was researched. In each of these terrains, the percentage of trees detected correctly was 74%, 86%, and 92%; the average error between LiDAR-derived and field-measured tree heights was 0.227m, –0.473m, and –0.183m; and the accuracy of the LiDAR-derived tree height estimates, given as root mean square error (RMSE), was 0.901m, 0.846m, and 0.576m, respectively. Consequently, the procedure presented in this study could detect most canopy trees and estimate individual tree heights with an accuracy better than 1m, even in a forest with a mean slope angle of approximately 38°; thus, indicating that small-footprint airborne LiDAR will be a useful tool for accurately estimating the heights of individual canopy trees in sugi plantations in mountainous areas.     

Mangrove structure,litter and macroalgal productivity in a northern‐most forest of Florida

Rhizophora mangle L. dominated 10 overwash islands within Tampa Bay forming the northernmost mangrove forests on the west coast of Florida. The mean number of trees and basal area were 5040 trees ha^-1 and 20.5m²ha^-1, respectively. Basal areas ranged from 1.1 (Avicennia germinans (L.) Stern), to 2.6m²ha^-1 (Laguncularia racemosa Gaertner), to 16.8 (R. mangle). Cockroach Bay mangroves are small (5.8–7.0m tall) versus coastal forests of south Florida and the Caribbean. Total litter production for a 12 month period was maximal in September for fringing (7.4gdwtm^-2d^-1) and interior (8.7gdwtm^-2d^-1) areas with the two zones not being significantly different. Average litter fall (3.1gdwtm^-2d^-1) was similar to more tropical Caribbean mangals. Leaves accounted for 68 of the litter and reproductive material for 6, being similar to tropical riverine and overwash marine angiosperm communities on the Mexican coast. Although mangrove forests in Tampa Bay are small in stature and experience cold damage and occasional frosts, their litter fall is similar in biomass to that of more tropical mangals. However, their reproductive output is low based on litter fall versus more tropical mangals suggesting that the northern extension is less than optimum. Macroalgal diversity was low (10 species) as compared to Caribbean mangals. Macroalgal turf (0.8gCm^-2d^-1) and epiphyte communities of A.germinans pneumatophores (2.7gCm^-2d^-1) have productivity levels that are equal to or greater than those of Caribbean mangals.