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1.
Dunsworth  G.B. 《New Forests》1997,13(1-3):439-448
The regions of the world using operational seedling testing to any significant extent are Canada, Britain, Sweden, and the Pacific Northwest region of the United States. Testing has been used operationally for batch culling (to ensure quality), as well as for research into improved nursery cultural practices. Savings from testing for seedling survival are substantial. However, growth gains from operational testing are more tenuous. Reduced rotation lengths and lower weeding costs are more likely to be associated with planting larger stock, rather than planting stock with higher physiological quality.Large opportunities for savings exist for regions and organizations that produce poor quality stock, have high planting costs, or both. New tests have been developed and some are becoming operational. New tests might be more effective than existing tests. However, in the regions most involved in seedling testing, plantation survival has increased over the last ten years. Subsequently, additional investments in operational testing will likely achieve diminishing returns.  相似文献   

2.
Farm-level simulators such as the Agroforestry Estate Model use as inputs either yield tables or outputs from forest modeling tools. Forest models rely upon assumptions on site index, stem diameter (DBH) distribution, wood production and tree mortality, which may or may not apply to agroforestry practices. Differences may arise because of the effects on tree growth of unusual spacings and configurations, fertilizer, pruning and grazing regimes, and tree-understory relationships as well. We examined data from published or existing field trials to determine mid- and long-term trends in tree growth and understory yields in silvopastoral practices with southern pines (Pinus spp.) in the United States. Tree DBH and height were greater in practices with improved pastures than in those with spontaneous grasses. Understory affected DBH more than height and, therefore, DBH-height relationships differed among practices. Sigmoidal models predicted that tree height will peak at different age depending on tree spacing and understory type. These changes may affect the accuracy of site indices and wood yield predictions. Livestock gains decrease linearly with increasing stand basal area and stand age, although forage yields sometimes decay exponentially. In one of the experiments, livestock gains decreased to almost zero at age 19 but with stand basal areas at that age markedly differing (14 and 25 m2 ha–1) for two different spacings. Additional data would allow to generate empirical algorithms to obtain farm-level simulations of broad application, improve economic analysis and generate hypotheses to guide future experimental work. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

3.
Bareroot nursery practices that maximize root development and growth have been studied and documented over a number of years. Each nursery, however, has its own unique combination of climate, soils, species, and stocktypes for which site specific cultural practices are necessary. J. Herbert Stone Nursery, a USDA Forest Service nursery, located in Central Point, OR, has completed a variety of production trials to adapt general cultural practices to its site. These trials resulted in changes which include: developing a strategy to maintain a high soil porosity through the application of organic matter and tillage measures; sowing seed earlier in the winter for 1 + 0 stocktypes; lowering seedbed densities from 267 seedlings/m2 (25 seedlings/ft2) to between 161 and 195 seedlings/m2 (15 and 18 seedlings/ft2); transplanting seedlings in early fall instead of spring; and developing a miniplug + 1 stocktype.  相似文献   

4.
Mechanical shock during transportation: effects on seedling performance   总被引:1,自引:0,他引:1  
Stjernberg  Ernst I. 《New Forests》1997,13(1-3):401-420
A study was carried out to monitor shocks to seedling planting stock during transport from nursery to the planting site in normal commercial reforestation operations. Size and exact time of mechanical shocks were measured by a recorder placed inside seedling boxes. Seedling shipments by refrigerated semi-trailer, 5-ton truck, pickup truck, small trailer and all-terrain vehicles were monitored in Alberta and British Columbia. Number of shocks, peak acceleration and average drop height were tabulated for travel on both paved and gravel roads.Twenty-two trials involving seven species were established at nurseries and field locations covering several ecological zones in both provinces. Frozen-stored, cool-stored, and freshly lifted seedlings were used in the trials. Seedlings were given two mechanical stress treatments by dropping them 30 times from 0.5-m and 30 times from 1.0-m, respectively. Control seedlings were not dropped. Treatments were applied to nursery-trial seedlings not exposed to normal handling and transport, and to field-trial seedlings after transport to the planting site. Six root growth potential tests were made with treated and control seedlings in conjunction with the nursery trials.Seedling survival and volume growth were recorded for two growing seasons and the results statistically analysed.  相似文献   

5.
Rationale for growing southern pine seedlings at low seedbed densities   总被引:2,自引:0,他引:2  
Although most bare-root pine seedlings in the Southern United States are grown at seedbed densities near 300/m2, the density used in other regions of the world is often less than 200/m2. One rationale for growing seedlings at lower seedbed densities is based on the desire to reduce the time required for successful stand establishment. Achieving a one- to two-year advancement in stand establishment can result in an additional 15 to 30 m3/ha within 15 to 20 years. Although seedling grade studies have demonstrated similar gains in volume production at ages 10 to 30 years, the findings from these studies are not widely known. The rationale in the Southern United States for growing at higher seedbed densities appears to be based on: (1) misinformation regarding the performance of morphologically improved seedlings; (2) a desire to minimize seedling and planting costs; and (3) density recommendations that are not based on volume growth in the field.  相似文献   

6.
Information regarding how site preparation techniques affect residual woody structure is lacking for the southern United States in spite of the importance of such structure for many wildlife species. Therefore, we documented retained structure in young loblolly pine (Pinus taeda L.) plantations established using four common site preparation regimes: mechanical only, chemical only, chemical + mechanical, or chemical + prescribed burning. Herbicides reduced live tree density and increased snag density relative to mechanical methods. Prescribed burning reduced density of coarse woody debris (CWD) along with density and volume of piled CWD relative to chemical and mechanical methods. Our results provide a baseline for further studies of wildlife and retained structure in southern pine forests.  相似文献   

7.
Intensively managed loblolly pine (Pinus taeda) forests are common in the southeastern United States and offer opportunities for conservation of biologic diversity. Within intensively managed landscapes, stand establishment relies on combinations of mechanical and chemical site preparation and herbaceous weed control (HWC) to manage competing vegetation and increase pine production. However, few long-term studies have described relationships between intensity of stand establishment and effects on plant communities. Therefore, we examined effects of 6 treatments that varied in intensity via combinations of mechanical (wide spacing and strip shear or narrow spacing and roller chop) and chemical (application or no application) site preparation treatments with HWC (broadcast or banded) from 1 to 8 years after site preparation on plant communities in loblolly pine plantations (n = 6) in the Coastal Plain of North Carolina, USA. All treatments resulted in abundant and diverse plant communities. Chemical site preparation had short lived (?4 year) effects on the herbaceous community but long-term effects on woody plants and pine cover. Increasing management intensity by including broadcast HWC or roller chop/narrow spacing did not additively reduce woody vegetation cover or species richness. However, broadcast HWC reduced grass, vine, and forb cover in the first year post-treatment. Average Morista community similarity values ranged from 0.69 to 0.89 among treatments and plots receiving the same chemical site preparation contained the most similar plant communities. Banded HWC can be paired with wide spacing to maximize herbaceous plant growth important for many wildlife species, particularly in the first few years after site preparation. Site preparation techniques should be tailored to local site conditions, plant communities, and management objectives.  相似文献   

8.
After five years of growth at high-elevations (∼3000 m) in Utah, container lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings survived well (80–95%) and grew to similar heights regardless of nursery storage method and site preparation technique. Seedlings received one of three storage treatments: (1) spring-sown in the nursery, overwintered in cooler storage and outplanted in July; (2) spring-sown, overwintered in freezer storage, and outplanted in July; or (3) winter-sown, no storage, and hot-planted in late August. We outplanted seedlings at two locations that were clearcut and had received two treatments of surface organic matter (coarse wood, logging slash, and forest floor) removal: surface organic matter (OM) piled with a bulldozer and burned or surface OM remaining in situ. Compared to adjacent uncut stands, both site preparation treatments increased total soil bulk density, but retaining surface OM in situ maintained soil OM, carbon, and nitrogen levels. After one growing season, seedlings planted where surface OM had been bulldozed were taller and had more biomass, although survival was similar (≥96%) across site preparation treatments. The height growth advantage disappeared after five growing seasons and although overall survival was good, survival was highest where site preparation involved removal of surface OM and freezer-stored seedlings were planted. Total non-structural carbohydrates tended to be higher in roots than in shoots and were also higher in hot-planted seedlings than in stored seedlings. Our results indicate that nursery and forest managers have several options for successful nursery production and outplanting of container lodgepole pine seedlings in the central Rocky Mountains. Using hot-planted seedlings allows for a faster turnaround time (from seed to plantable seedling) and maintaining surface OM may be a cost-effective alternative to dozer piling and burning.  相似文献   

9.
GILL  J. GRAHAM S. 《Forestry》1983,56(1):61-73
A system has been developed by the British Forestry Commissionfor bulking-up plant numbers from scarce seedlots by rootedcuttings. Commercial-scale trials of the system are now underway.This paper describes a comparison of the costs of producingplanting stock by two methods; traditional nursery rearing oftransplants (1 + 1) and vegetative propagation of stock materialto produce cuttings (Cl + 1). Genetic gains are predicted andcompared for both systems, predictions being based on quantitativeestimates of genetic variables from progeny tests and on thecurrent progress of the breeding programme. The implicationsof the economic comparison for the future breeding programmefor Sitka spruce are discussed.  相似文献   

10.
Infections with Heterobasidion parviporum devalue the Norway spruce timber as the decayed wood does not meet the necessary quality requirements for sawing. To evaluate the incorporation of disease resistance in the Norway spruce breeding strategy, an inoculation experiment with H. parviporum on 2-year-old progenies of 466 open-pollinated families was conducted under greenhouse (nursery) conditions. Lesion length in the phloem (LL), fungal growth in sapwood (FG) and growth (D) were measured on an average of 10 seedlings for each family. The genetic variation and genetic correlations between both LL, FG and growth in the nursery trial and wood quality traits measured previously from 21-year old trees in two progeny trials, including solid-wood quality traits (wood density, and modulus of elasticity) and fiber properties traits (radial fiber width, tangential fiber width, fiber wall thickness, fiber coarseness, microfibril angle and fiber length). For both LL and FG, large coefficients of phenotypic variation (>?26%) and genetic variation (>?46%) were detected. Heritabilities of LL and FG were 0.33 and 0.42, respectively. We found no significant correlations between wood quality traits and growth in the field progeny trials with neither LL nor FG in the nursery trial. Our data suggest that the genetic gains may reach 41 and 52% from mass selection by LL and FG, respectively. Early selection for resistance to H. parviporum based on assessments of fungal spread in the sapwood in nursery material, FG, will not adversely affect growth and wood quality traits in late-age performance.  相似文献   

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