ISSN:1054-9811    

DOI:10.1300/J091v08n01_01

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Four conifer species [Douglas-fir(Pseudotsuga men-ziesiivar.glauca(Beissn.) Franco), ponderosa pine(Pinits pondero-saDougl. ex. Laws.), western larch(LarLx occidentalisNutt.), and western white pine(Pimts monticolaDougl. ex. D. Don)], growing on three different duff depths on burned and unburned seedbeds, were examined for germination, survival, height and diameter growth after three years on aThuja plicatajClintonia unijlorahabitat type (Cooper et al. 1991) in northern Idaho. Regeneration success increased as duff thickness decreased. Germination and seedling establishment were greater on mineral soil seedbeds than the three burned duff seedbeds. Significant differences in total height and basal . diameter appeared between burned and unburned seedbeds, with taller and thicker diametered individuals for all species on burned seedbeds. Based on these findings, prescribed burning should be the site preparation method for natural regeneration of these coniferous species on this habitat type in the northern Rocky Mountains.

ISSN:1054-9811    

DOI:10.1300/J091v08n01_02

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Individual and interactive effects of elevated atmospheric COT and soil N fertility on juvenile ponderosa pine(Piiius ponderosaDougl. ex Laws.) were examined, focusing primarily on root system development. Controlled-environment growth chambers permitted creation of atmospheres with 700 µL L-1, 525 µL L-1, or ambient CO2concentrations. Seedlings were reared from seed in soil with a total N concentration of 900 µL L-1or in soil amended with sufficient (NH4)2S04 to increase total N by 100 mgg. An initial whole-seedling harvest after 4 months and a final harvest after 11 months permitted assessment of shoot and root growth and ectomy-corrhizal colonization as affected by each combination of COi and N treatment. Throughout the study, shoot growth was moderately increased by the 525 µL L-1' CCb atmosphere, evident primarily in volume measurements, but not by 700 µL L-1CCb. The stimulation of shoot growth by the intermediate CCb concentration was confined to low soil N initially but to high N at the conclusion of the study. Total root system length and specific root length were increased by 525 µL L-1CCb after 4 months and specific root length again after 11 months. Both enriched atmospheres increased root volume, total root length, and fine root mass after 11 months as well. Elevated CO2 effects on shoot/root ratio were nonsignificant initially, but at the final harvest, reduced ratios prevailed in the 525 and 700 µL L-1treatments, a result accentuated by high soil N. Total numbers of mycorrhizae formed were increased by 525 µL L-1CCb throughout the study, and mycorrhizal count and the percentage of root length colonized were increased by 700 µL L-1CCb after II months. These results suggest that the growth of root organs is stimulated by CCb enrichment substantially more than that of shoot tissues in juvenile ponderosa pine.

ISSN:1054-9811    

DOI:10.1300/J091v08n01_03

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Availability of quality planting material in the Himalayan region is one of the major constraints limiting the progress of afforestation programmes and rehabilitation of degraded/wastelands. The poor economy, difficult terrain and inaccessibility prohibits the use of high-tech controlled condition glasshouses for raising tree saplings.

ISSN:1054-9811    

DOI:10.1300/J091v08n01_04

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The presence of white pine(Pinus strobusL.). influenced the structure and yields of mixed-species, multi-cohort, northern conifer stands in Maine. In each of the five stands studied, mean plot volumes were consistently higher where white pine grew with more shade tolerant conifers, than in plots without the additional pine component. However, considerable variability in stand structures among plots resulted in no significant differences in volumes within stands. When plot volumes from the five stands were combined, the larger sample size resulted in the mean volume of pine plots being significantly higher (P < 0.02) than those that had none (355.30 ± 25.24 m3/ha vs. 275.06±16.98 m-Vha). Generally, pine's presence enhanced plot volumes but had a negative effect on spruce and hemlock volumes. Whether or not pine was present, plot volumes were greatly affected by variability in age structures. Plots with a representation of two or three cohorts had higher volumes than plots with a single cohort.

ISSN:1054-9811    

DOI:10.1300/J091v08n01_05

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

To determine the initial effects of slash pile burning on chemical and physical properties in the Vassar soil series, mineral soil samples from two depths (2.5 cm and 12.5 cm) were collected before and after burning slash piles of four fuel loadings (0.5 m, 1 m, 2 m and 3 m) over wet and dry soils, as well as from burned and unburned litter plots. Surface soil CEC decreased with increasing fuel loads, reflecting the increased combustion of fuels, longer residence time of the fires, and increased fire severity with these heavier loads. Available nitrogen increased with increasing fuel loads as a result of the increased total quantity of mineralization of organic N from the heavier fuels. While some cations (magnesium and sodium) increased after burning, others, such as calcium, in general decreased.

ISSN:1054-9811    

DOI:10.1300/J091v08n01_06

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

UNDAUNTED COURAGE: MERIWETHER LEWIS, THOMAS JEFFERSON, AND THE OPENING OF THE AMERICAN WEST. Ambrose, Stephen E. 1996.Simon and Schuster, NY, pp. 511.Reviewed by Graeme P. Berlyn.

ISSN:1054-9811    

DOI:10.1300/J091v08n01_07

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor