doi: 10.1093/forestscience/44.3.z7pmid: N/A
This content is only available as a PDF. © 1998 by the Society of American Foresters
doi: 10.1093/forestscience/44.3.z1pmid: N/A
This content is only available as a PDF. © 1998 by the Society of American Foresters
Mutch, Linda S.; Parsons, David J.
doi: 10.1093/forestscience/44.3.341pmid: N/A
Pre- and post-burn tree mortality rates, size structure, basal area, and ingrowth were determined for four 1.0 ha mixed conifer forest stands in the Log Creek and Tharp's Creek watersheds of Sequoia National Park. Mean annual mortality between 1986 and 1990 was 0.8% for both watersheds. In the fall of 1990, the Tharp's Creek watershed was treated with a prescribed burn. Between 1991 and 1995, mean annual mortality was 1.4% in the unburned Log Creek watershed and 17.2% in the burned Tharp's Creek watershed. A drought from 1987 to 1992 likely contributed to the mortality increase in the Log Creek watershed. The high mortality in the Tharp's Creek watershed was primarily related to crown scorch from the 1990 fire and was modeled with logistic regression for white fir (Abies concolor [Gord. and Glend.]) and sugar pine (Pinus lambertiana [Dougl.]). From 1989 to 1994, basal area declined an average of 5% per year in the burned Tharp's Creek watershed, compared to average annual increases of less than 1% per year in the unburned Log Creek watershed and in the Tharp's watershed prior to burning. Post-burn size structure was dramatically changed in the Tharp's Creek stands: 75% of trees ≤50 cm and 25% of trees >50 cm were killed by the fire. For. Sci. 44(2):341-355.
doi: 10.1093/forestscience/44.3.356pmid: N/A
Different decision models can be constructed and used to analyze a regeneration decision in even-aged stand management. However, the optimal decision and management outcomes determined in an analysis may depend on the decision model used in the analysis. This paper examines the proper choice of decision model for determining the optimal planting density and land expectation value (LEV) for a Scots pine (Pinus sylvestris L.) plantation in northern Sweden. First, a general adaptive decision model for determining the regeneration alternative that maximizes the LEV is presented. This model recognizes future stand state and timber price uncertainties by including multiple stand state and timber price scenarios, and assumes that the harvest decision in each future period will be made conditional on the observed stand state and timber prices. Alternative assumptions about future stand states, timber prices, and harvest decisions can be incorporated into this general decision model, resulting in several different decision models that can be used to analyze a specific regeneration problem. Next, the consequences of choosing different modeling assumptions are determined using the example Scots pine plantation problem. Numerical results show that the most important sources of uncertainty that affect the optimal planting density and LEV are variations of the optimal clearcut time due to short-term fluctuations of timber prices. It is appropriate to determine the optimal planting density and harvest policy using an adaptive decision model that recognizes uncertainty only in future timber prices. After the optimal decisions have been found, however, the LEV should be re-estimated by incorporating both future stand state and timber price uncertainties. For. Sci. 44(3):356-364.
doi: 10.1093/forestscience/44.3.365pmid: N/A
In pursuing silvicultural goals on licensed public lands, governments worldwide have adopted various policy instruments including contractual requirements, the reimbursement of silvicultural costs, and investment incentives in the form of shares in the value of timber crops resulting from voluntary silvicultural activities. Monte Carlo simulations are used to investigate the efficiency implications of alternative silvicultural policy options. Results indicate that current policies, dominated by requirements and reimbursements with uncertain costs, may create significantly less wealth than policies that include some share of future timber crops. Means of granting shares include reimbursing tenure holders according to the present value of the future benefits created by their expenditures or by sharecropping arrangements. Such policies could potentially provide tenure holders with incentives to efficiently invest in silvicultural activities, by alleviating tenure insecurity while correcting for market failures. For. Sci. 44(3):365-378.
Ozanne, Lucie K.; Smith, Paul M.
doi: 10.1093/forestscience/44.3.379pmid: N/A
A study was conducted to segment consumers in terms of their attitudes toward environmentally certified wood products. Factor analysis reduced seven variables of environmental certification to two distinct factors. Cluster analysis, performed on the seven variables of forest and wood products certification, suggested the existence of six relatively homogeneous groupings or segments of consumers. Multiple discriminant analysis provided a method for profiling these six consumer segments in terms of demographic, attitudinal, and trust (respondent's trust in potential certifying organizations) variables. This paper identifies one consumer segment of approximately 25 million Americans who would most likely seek out environmentally certified wood products. Relative to our other study respondents, they can be described as politically liberal, Democrats, female, members of an environmental organization, fairly well educated, concerned about the quality of the environment and forest resources, and having high self-rated environmental knowledge. In addition, these respondents would place the most trust in the certification claims made by an environmental organization. Conversely, a consumer segment of nearly 10 million Americans appears highly skeptical of certification programs, in general. Consistent with previous literature, our demographic variables were less effective in discriminating among groupings of consumers than attitudinal and trust variables. Implications of segmentation strategies are discussed for both industrial managers and forest policymakers. For. Sci. 44(3):379-389.
Adams, W. Thomas; Zuo, Jinghua; Shimizu, Jarbas Y.; Tappeiner, John C.
doi: 10.1093/forestscience/44.3.390pmid: N/A
Genetic implications of natural and artificial regeneration following three regeneration methods (group selection, shelterwood, and clearcut) were investigated in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) using genetic markers (17 allozyme loci). In general, harvesting followed by either natural or artificial regeneration resulted in offspring populations little altered from those in the previous generation. Cutting the smallest trees to form shelterwoods, however, resulted in the removal of rare, presumably deleterious, alleles, such that slightly fewer alleles per locus were observed among residual trees (2.76) and natural regeneration (2.75) than found in uncut (control) stands (2.86). Thus, although the shelterwood regime appears quite compatible with gene conservation, it would be best to leave parent trees of a range of sizes in shelterwoods designated as gene conservation reserves, in order to maximize the number of alleles (regardless of current adaptive value) in naturally regenerated offspring. Seedling stocks used for artificial regeneration in clearcut, shelterwood, and group selection stands (7 total) had significantly greater levels of genetic diversity, on average, than found in natural regeneration. This is probably because the seeds used in artificial seedling stocks came from many wild stands and thus, sampled more diversity than found in single populations. For. Sci. 44(3): 390-396.
Zutter, Bruce R.; Glover, Glenn R.; Mitchell, Robert J.
doi: 10.1093/forestscience/44.3.397pmid: N/A
Loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) seedlings were planted at a range of densities on a formerly cultivated field which varied in soil organic matter (soil OM) in the upper 15 cm of the soil. Mean aboveground biomass per plant at the end of one growing season was examined to see how it varied as a function of plant density and soil OM. Biomass per plant as a function of density, holding soil OM constant, was described well by a reparameterized form of a standard yield density equation. A simple linear equation suitably described per plant biomass as a function of soil OM, holding density constant. Effects of soil OM on biomass were positive for both species, with sweetgum exhibiting a stronger response than loblolly pine. Based on the results of fitting equations to single factors, an equation considering both density and soil OM was developed and fitted using all data for each species. The equations explained 85% of the variation in response for both species. The inclusion of soil OM was more important in describing response of sweetgum than for loblolly pine. Inclusion of both density and soil OM in a single equation to describe mean response of plants in a monoculture might be extended to a mixture of species and used to examine intraspecific and interspecific competitive effects of competition and their relationship with productivity. For. Sci. 44(3):397-404.
Bondesson, Lennart; Ståhl, Göran; Holm, Sören
doi: 10.1093/forestscience/44.3.405pmid: N/A
In this article, the problem of determining standard errors of area estimates obtained by traversing is addressed. In traversing, a surveyor moves along the boundary of a compartment and makes measurements at certain base points to determine their coordinates. Two cases of traversing are described: the case when coordinates are determined directly using GPS equipment and the case when distances and directions are measured from every base point to the next. It is shown that the problem of determining standard errors of the area estimates is different for the two cases. Formulas are derived from basic assumptions about the measurement errors. The efficiency of the two approaches is compared. It is found that the standard errors for the two methods often are of a similar magnitude but that the size and the shape of a compartment affect what method should be preferred. For. Sci. 44(3):405-413.
Parker, Bruce L.; Skinner, Margaret; Gouli, Svetlana; Ashikaga, Takamaru; Brenton Teillon, H.
doi: 10.1093/forestscience/44.3.414pmid: N/A
The hemlock woolly adelgid (Adelges tsugae Annand [Homoptera: Adelgidae]) (HWA), a nonnative insect, is a major threat to New England forest and suburban environments, where one of its hosts, eastern hemlock, Tsuga canadensis (L.) Carrière, is a dominant native tree species. To determine the potential spread of HWA into northern New England, we studied the winter coldhardiness of a northerly population. Sistens were collected at three times during the winter and subjected to temperatures typical of those during winter in the next coldest USDA plant coldhardiness zone. Samples collected in January and February 1996 were subjected to -20, -25, and -30°C; those collected in March to -15, -20, and -25°C; all date-temperature treatments were tested at exposure times of 1, 2, 4, 8, and 24 hr. When all exposure times were combined, the percentage of live adelgids after subzero treatment (adjusted for control mortality at 0°C) declined significantly as temperature decreased. In most cases, fewer HWA were alive after treatment as exposure time increased. Significantly more HWA collected in January were alive after treatment than those collected in February and March. This suggests that HWA coldhardiness declines over this time period. When comparing the percentage of live HWA from February and March for -20 and -25°C, a noticeable decline occurred between the February and March sample dates. Although mortality was as high as 95% in one of the most severe treatments (February collection exposed to -30°C for 24 hr), the fact that complete mortality did not occur suggests that HWA may be able to continue to expand its range into areas with colder winters. For. Sci. 44(3):414-420.
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