Native pine species performance in response to age at planting and mulching in a site affected by volcanic ash deposition

Under heavily disturbed conditions, the selection of the appropriate native species and of planting and ameliorating techniques is necessary. Volcanic eruptions create harsh conditions that can preclude native plant establishment. We tested the performance of two native species Pinus pseudostrobus and P. montezumae for restoration of volcanic ash covered areas. Two age classes of P. pseudostrobus and one of P. montezumae were tested as well as the effect of mulching to ameliorate harsh substrate conditions. Results show that older plants of P. pseudostrobus (19-month old at planting) have higher survival and growth rates than young plants (8-months at planting). Plants at least 19-months-old at planting of P. pseudostrobus and P. montezumae, are appropriate for restoration of volcanic ash covered areas. Mulching had no effect on plant survival or growth for this experiment.     

Thermal-softening properties and cooling set of water-saturated bamboo within proportional limit

Thermal-softening properties and cooling set of water-saturated bamboo were investigated using stressrelaxation measurements in heating and cooling processes, followed by residual deflection measurement. In the heating process, an obvious decrease in relative relaxation modulus due to thermal-softening of lignin was found at around 60°C. On the other hand, no clear change in the relative relaxation modulus was recognized in the cooling process. After the cooling process, about 65% and 75% of residual set was measured when the specimen was loaded on the epidermis and endodermis side, respectively. Also, residual set depended on the maximum temperature reached in the heating process and the unloaded temperature in the cooling process. From these results, it was deduced that the glass transition of lignin from the rubbery to glassy state is important to fix the deformation. Comparing thermal-softening behavior between bamboo and wood, the relative relaxation modulus of wood decreased steeply at higher temperatures than for bamboo. On the other hand, while about 75% of residual set was also found for wood, almost the same as for bamboo, the recovery of deformation with time was larger for wood than for bamboo. Part of this article was presented at the 53rd Annual Meeting of the Japan Zairyou Society, Okayama, May 2004     

Projected benefit-cost analysis of agri-silvicultural system: vegetable crops intercropping with <Emphasis Type="Italic">Salix alba</Emphasis> (Willow)

An experiment upon an agri-silvicultural system involving Willow (Salix alba) tree, Kale (Brassica oleracea var. acephala) and Knol khol (Brassica oleracea var. caularapa) was laid in randomized block designed at farmers’ willow field at Shalimar near Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Srinagar India during 2005 and 2006. The main plot was divided into sub-spots with 8 m × 2 m in size each in which four two-year-old willow (Salix alba) trees were at a spacing of 2 m × 2 m in a sub-spot. The intercrops were maintained at recommended spacing and supplied with recommended doses of fertilizers. The benefit-cost ratio in willow plantation intercropped with vegetable crops of Kale and Knol Khol was analyzed and compared with the benefit-cost ratio of sole willow tree forestry. The results showed that every rupee invested in plantation of agri-silvicultural system generates benefit-cost ratio of 2.78 and 2.79 in case of Willow intercropping with Kale and Willow with Knol khol, respectively, while as for sole crop of willows benefit-cost ratio was calculated to be 2.66. These results provided circumstantial evidence in favour of adopting agroforestry involving willow instead of Sole tree forestry.     

Root trenching: a useful tool to estimate autotrophic soil respiration? A case study in an Austrian mountain forest

We conducted a trenching experiment in a mountain forest in order to assess the contribution of the autotrophic respiration to total soil respiration and evaluate trenching as a technique to achieve it. We hypothesised that the trenching experiment would alter both microbial biomass and microbial community structure and that fine roots (less than 2 mm diameter) would be decomposed within one growing season. Soil CO₂ efflux was measured roughly biweekly over two growing seasons. Root presence and morphology parameters, as well as the soil microbial community were measured prior to trenching, 5 and 15 months after trenching. The trenched plots emitted about 20 and 30% less CO₂ than the control plots in the first and second growing season, respectively. Roots died in trenched plots, but root decay was slow. After 5 and 15 months, fine root biomass was decreased by 9% (not statistically different) and 30%, (statistically different) respectively. When we corrected for the additional trenched-plot CO₂ efflux due to fine root decomposition, the autotrophic soil respiration rose to ~26% of the total soil respiration for the first growing season, and to ~44% for the second growing season. Soil microbial biomass and community structure was not altered by the end of the second growing season. We conclude that trenching can give accurate estimates of the autotrophic and heterotrophic components of soil respiration, if methodological side effects are accounted for, only.     

Decline of <Emphasis Type="Italic">Pinus thunbergii</Emphasis> Parlat. stands due to excess soil moisture caused by a buried andosol layer at a coastal sand site in Hokkaido,northern Japan

To demonstrate the effect of excess soil moisture on the decline of a coastal Pinus thunbergii stand in Oshamanbe, southwestern Hokkaido, Japan, soil moisture content was monitored for 4 years. The saturated hydraulic conductivities (K _S) of different soil types (coastal sand, supplied topsoil, and buried concreted andosol) and the distribution of the buried concreted andosol layer were investigated. We also examined needle length to verify the real-time response of P. thunbergii to excess soil moisture. Soil moisture content at the heavily damaged site was more heterogeneous than that at the slightly damaged site, and a sensor near the ground always reported a higher soil moisture content at the heavily damaged site than at the slightly damaged site. The buried concreted andosol layer was always found at the heavily damaged site. The K _S of the andosol layer was 10⁻⁵, suggesting that this layer is less permeable to water, leading to excess soil moisture at this site. P. thunbergii needles from the heavily damaged site were shorter than those from the slightly damaged site, possibly because of water stress. Together with other symptoms observed at the study sites, i.e., crown dieback and intense lateral growth, this information leads us to conclude that the decline of P. thunbergii stands at the heavily damaged site in Oshamanbe was caused by excess soil moisture due to the less permeable buried concreted andosol layer.     

Performance of northern red oak enrichment plantings in naturally regenerating Southern Appalachian hardwood stands

The limited success of methods to naturally regenerate northern red oak (Quercus rubra L.) has increased the use of artificial techniques to improve overall oak composition. Enrichment plantings are often recommended as a means to supplement species composition within the existing natural reproduction. Previous enrichment efforts have often resulted in low survival and poor growth, generally due to poor planting stock quality and a lack of competition control. In this study, high quality northern red oak seedlings were established on four recently harvested sites in western North Carolina using one of four competition control treatments (untreated, year 1 control, year 2 control or a weed mat) in a 1.2 × 1.2 m area around each seedling with or without a soil fertility amendment. The 3 year results show that competition control and fertilization treatments had few positive impacts on survival and growth of the planted seedlings. These results suggest that either the treatment area was insufficient to adequately release the seedlings, or other factors like belowground competition from existing advance reproduction and/or stump sprouts may be important determinants of the overall success of northern red oak enrichment plantings on recently harvested sites.     

Relationship of wood composition to growth traits of selected open-pollinated families of <Emphasis Type="Italic">Eucalyptus urophylla</Emphasis> from a progeny trial in Vietnam

Lignin and cellulose contents and wood basic density were related to diameter at breast height (DBH) in six fast-growing and five slow-growing families from a combined progeny test and seedling seed orchard of Eucalyptus urophylla grown for 10 years in northern Vietnam. The mean cellulose content of the fast-growing families was significantly higher than that of the slow growing-families (40.0 and 37.1%, respectively), and for individual trees cellulose content was significantly correlated phenotypically with DBH. Wood basic density was significantly lower in the fast-growing group than in the slow-growing group (0.506 and 0.535 g cm⁻³, respectively), and was significantly negatively correlated phenotypically with DBH. The lignin contents were not significantly different between groups. Cellulose content and wood basic density were not correlated. The main conclusion is that there is no obstacle to combining high growth rate with high cellulose content, for plantation of forests intended mainly for pulpwood.     

Temperature-dependent differences in biological traits between two strains of <Emphasis Type="Italic">Trichogramma cacoeciae</Emphasis> (Hymenoptera: Trichogrammatidae)

Parasitoids’ efficiency in controlling pests depends not only on their ability to parasitize their hosts but also on how much they are adapted to climatic conditions (notably temperature) of the area where they are planned to be released. In addition, the optimal conditions for production of parasitoids used for inundative releases like Trichogramma spp. may also vary largely as a function of strains. Using the parasitoid Trichogramma cacoeciae Marchal as biological model, we studied how temperature affects important parasitoid efficiency-related biological traits under laboratory conditions. Emergence, mortality rates and fecundity of two strains of T. cacoeciae, one originating from France (Alsace) and the other one from Tunisia (Degache), were compared at constant temperatures of 15, 20, 25 and 30°C. The parasitoids of the French strain showed highest fecundity at 25°C with wasps that had been reared at 20 or 25°C. The Tunisian strain showed the highest fecundity at 25°C, but only when wasps were previously reared at 25 or 30°C. For both strains, the highest mortality occurred among wasps that had laid eggs at 30°C. Emergence rates were relatively high at all temperatures, although the French strain did better at 15–25°C and the Tunisian one at 20–30°C. Because of the differences in biological traits of these two T. cacoeciae strains in relation to the temperature, a judicious choice must be made among the various strains when using this species in biological control programs.     

A deterministic harvest scheduler using perfect bin-packing theorem

The use of heuristic techniques in forest planning has been promoted by the need to solve complex problems that cannot be solved using mixed integer programming. We proved that for merchantability standards ensuring the perfect bin-packing theorem (PBPT), the maximum volume that can be harvested annually equals the sum of the maximum MAI of the stands. The method accommodates optimality criteria at the stand level, regarded as maximum MAI, and at the forest level, regarded as maximum annual allowable cut. We scheduled the harvesting by adjusting the first fit decreasing algorithm (FFD) to the PBPT conditions. When PBPT conditions were not met, we developed a mixed integer programming solution to adjust the merchantability standards of the stands to the distributional requirements of the PBPT, an adjustment that ensured the optimal performance of the FFD. The adjusted FFD was compared with linear programming (LP) and simulated annealing (SA) using two harvesting ages (i.e., one based on MAI maximization and one determined as the minimal age) and the same set of spatial temporal constraints for three areas in north-eastern British Columbia, Canada. We found that the adjusted FFD performed 100 times faster than SA and for annual allowable cut (AAC) supplied results that were more homogenous and at least 10% greater than the AAC supplied by SA. Furthermore, the adjusted FFD seemed to be relatively insensitive to spatial constraints (i.e., adjacency), while SA displayed a 70% reduction in AAC in response to an increase in adjacency delay from 1 year to 20 years. The results suggest that both adjusted FFD and SA are impacted by the selection of the harvesting age, but the adjusted FFD could still outperform SA.     

Azimuthal variations of sap flux density within Japanese cypress xylem trunks and their effects on tree transpiration estimates

Sap flow techniques are practical tools for estimating tree transpiration. Though many previous studies using sap flow techniques did not consider azimuthal variations of sap flux density (F _d) on xylem trunk to estimate tree transpiration, a few studies reported that ignoring the azimuthal variations in F _d could cause large errors in tree transpiration estimates for some tree species. Therefore, examining azimuthal variations in F _d for major plantation tree species is critical for estimating tree transpiration. Using the thermal dissipation method, we examined azimuthal variations in F _d in six trees of Japanese cypress Chamaecyparis obtusa (Sieb. et Zucc.) Endl., which is one of the most common plantation tree species in Japan. We recorded considerable variations among F _d at four different azimuthal directions. The F _d value for one aspect was more than 100% larger than those for the other aspects. We calculated differences between tree transpiration estimates based on F _d for one to three azimuthal directions and those based on F _d for four aspects. The differences relative to tree transpiration estimates based on F _d for four aspects were typically 30, 20, and 10% in accordance with the F _d for one, two, and three measurement aspects, respectively. This finding indicates that ignoring azimuthal variations could cause large errors in tree transpiration estimates for Japanese cypress.