bluuebunny/crossref_metadata_2025 huggingface dataset:
Airtanker initial attack: a spreadsheet-based modeling procedure
Authors: Greulich Francis E
Published: March 2003

Airtankers are widely employed in wildland fire control operations. This paper presents a spreadsheet procedure for modeling airtanker initial-attack performance within a protection region. Easily written and modified, this spreadsheet-based model provides the user with substantial flexibility when specifying the spatial distribution of fire occurrence within the initial-attack zone of an airtanker base. Once this spatial distribution has been specified, the expected flight distance from the airtanker base to a random fire ignition point as well as higher moments of the flight distance distribution are readily computed and applied using the spreadsheet. The chief advantages of this spreadsheet approach are described. Calculation procedures and potential applications of flight distance moments including the optimization of airbase location are illustrated. Detailed numerical examples and opportunities for future development are indicated.
11 000 years of fire history and climate in the mountain hemlock rain forests of southwestern British Columbia based on sedimentary charcoal
Authors: Hallett Douglas J , Lepofsky Dana S , Mathewes Rolf W , Lertzman Ken P
Published: March 2003

Little is known about the role of fire in the mountain hemlock (Tsuga mertensiana (Bong.) Carrière) rain forests of southern British Columbia. High-resolution analysis of macroscopic charcoal from lake sediment cores, along with 102 accelerator mass spectrometry (AMS) ages on soil charcoal, was used to reconstruct the long-term fire history around two subalpine lakes in the southern Coast and North Cascade Mountains. AMS ages on soil charcoal provide independent evidence of local fire around a lake and support the interpretation of peaks in lake sediment charcoal as distinct fire events during the Holocene. Local fires are rare, with intervals ranging from centuries to several millennia at some sites. Overall fire frequency varied continuously throughout the Holocene, suggesting that fire regimes are linked to climate via large-scale atmospheric circulation patterns. Fires were frequent between 11 000 and 8800 calendar years BP during the warm and dry early Holocene. The onset of humid conditions in the mid-Holocene, as rain forest taxa established in the region, produced a variable fire period until 3500 calendar years BP. A synchronous decrease in fire frequency from 3500 to 2400 calendar years BP corresponds to Neoglacial advances in the region and cool humid climate. A return of frequent fire between 2400 and 1300 calendar years BP suggests that prolonged summer drought occurred more often during this interval, which we name the Fraser Valley Fire Period. The present-day fire regime was established after 1300 calendar years BP.
Cellular phenology of annual ring formation ofAbies balsameain the Quebec boreal forest (Canada)
Authors: Deslauriers Annie , Morin Hubert , Begin Yves
Published: March 2003

Cell formation in growth rings of balsam fir (Abies balsamea (L.) Mill) in the boreal forest was studied to describe the timing of ring formation and the development patterns of earlywood and latewood. Wood micro-cores were extracted during the growing season from 1998 to 2000. The micro-cores were stained with cresyl fast violet to facilitate counting the number of cells in the radial enlargement, wall thickening phases, and mature cell phases. The periods required to complete these various phases were then estimated. Variations in the beginning of the growing season (May 7  June 7), the earlywoodlatewood transition (July 2  July 19), and the end of the growing season ( August 20  September 20) were observed. Short cell enlargement durations of less than a week for earlywood and 510 days for latewood were observed. Time required for cell wall thickening was about 20 days for earlywood and longer than 1015 days for latewood. A certain flexibility was observed in the ring formation patterns and in the cell development rate, providing an advantage in the boreal forest where optimal growth conditions change from year to year. These findings on the spatial and temporal patterns of ring development may be useful for understanding tree relationships with climate or other environmental parameters.
Changes in structural inequality in Norway spruce stands on peatland sites after water-level drawdown
Authors: Sarkkola Sakari , Alenius Virpi , Hökkä Hannu , Laiho Raija , Päivänen Juhani , Penttilä Timo
Published: March 2003

Size structural dynamics of naturally established Norway spruce (Picea abies (L.) Karst.) stands growing on peatlands drained for forestry were investigated. The study was based on modelling of diameter at breast height (DBH) distributions of repeatedly measured stands in southern Finland. The Weibull function was used to parameterize the DBH distributions and mixed linear models were constructed to characterize the impacts of different ecological factors on stand dynamics. Initially, the positive skewness of the DBH distributions increased after drainage as a result of increases in stem numbers and a reduction in mean diameters. Simultaneously, the size inequality among trees increased. These changes were due to regeneration and (or) ingrowth and indicated only little competition from the larger trees. Subsequently, the DBH distributions changed from positively skewed to normal and finally to negatively skewed resulting from tree growth and a reduction in the number of small DBH trees. This indicated increased asymmetric intertree competition. Size inequality did not change during this later stage in stand development, suggesting a concurrent component of symmetric competition. Thinnings had little impact on DBH distribution trends. The observed stand dynamics allow the allocation of growth resources to the desired crop component by appropriate silvicultural treatments.
Growth-dependent tree mortality models based on tree rings
Authors: Bigler Christof , Bugmann Harald
Published: March 2003

Mortality is a crucial element of population dynamics. However, tree mortality is not well understood, particularly at the individual level. The objectives of this study were to (i) determine growth patterns (growth levels and growth trends) over different time windows that can be used to discriminate between dead and living Norway spruce (Picea abies (L.) Karst.) trees, (ii) optimize the selection of growth variables in logistic mortality models, and (iii) assess the impact of competition on recent growth in linear regression models. The logistic mortality model that we developed for mature stands classified an average of nearly 80% of the 119 trees from one site correctly as being dead or alive. While more than 50% of the variability of recent growth of living trees can be attributed to the influence of competition, this percentage was only 25% for standing dead trees. The predictive power of the logistic mortality model was validated successfully at two additional sites, where 29 of 41 (71%) and 34 of 42 (81%) trees were classified correctly, respectively. This supports the generality of the mortality model for Norway spruce in subalpine forests of the Alps. We conclude that growth trends in addition to the commonly used growth level significantly improve the prediction of growth-dependent tree mortality of Norway spruce.
Belowground and aboveground biomass in young postfire lodgepole pine forests of contrasting tree density
Authors: Litton Creighton M , Ryan Michael G , Tinker Daniel B , Knight Dennis H
Published: March 2003

As much as 40% of live biomass in coniferous forests is located belowground, yet the effect of tree density on biomass allocation is poorly understood. We developed allometric equations using traditional harvesting techniques to estimate coarse root biomass for [Formula: see text]13-year-old postfire lodgepole pine trees (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.). We then used these equations, plus estimates of fine root and aboveground biomass, to estimate total tree biomass and belowground to aboveground biomass ratios in young postfire lodgepole pine stands with a wide range of tree densities. Belowground biomass allocation increased with tree density, but the increase was largely determined by inherent differences associated with tree size, not competition. Stand biomass in trees ranged from 46 to 5529 kg·ha1 belowground, from 176 to 9400 kg·ha1 aboveground, and from 222 to 13 685 kg·ha1 for total biomass. For individual trees, the ratio of belowground to total biomass declined with tree size from 0.44 at a basal diameter of 0.5 cm to 0.11 at a basal diameter of 8 cm. This shift in individual tree allocation caused the proportion of total stand biomass in belowground tissues to increase from 19% in low-density stands with larger trees to 31% in high-density stands with small trees.
Distribution and dynamics of tree species across a fire frequency gradient in the James Bay region of Quebec
Authors: Parisien Marc-André , Sirois Luc
Published: March 2003

This study examines how forest structure and composition change with spatial variations in the fire cycle across a shore-hinterland gradient. Twenty-one well-drained sites were sampled at different distances from James Bay to describe the forest stands. To quantify the role of fire in tree species distribution, a spatial analysis of fire polygons from 1930 to 1998 was undertaken in a 43 228 km2 study area adjacent to James Bay. Results from this analysis reveal an important decrease in the fire cycle, from 3142 to 115 years, from the shore to the hinterland. In forests bordering James Bay, white spruce (Picea glauca (Moench) Voss) is found in pure stands. It is gradually replaced by black spruce (Picea mariana (Mill.) BSP) at 0.5 km from the shore. Jack pine (Pinus banksiana Lamb.) abruptly appears at 22 km from the shore. There is a positive correlation between the frequency of white spruce and the fire cycle (R = 0.893), whereas this correlation is negative for black spruce (R = 0.753) and jack pine (R = 0.807) (Spearman correlations). Jack pine is confined to regions having a short fire cycle, while black spruce can seemingly maintain itself with or without fire. The exclusion of white spruce hinterland seems to be mainly due to a short fire cycle; however, other factors, such as soil development and species abundance, presumably have a marked influence on the distribution of this species.
Beech bark disease in northern hardwood forests: the importance of nitrogen dynamics and forest history for disease severity
Authors: Latty Erika F , Canham Charles D , Marks Peter L
Published: March 2003

Beech bark disease has been a major cause of mortality of American beech (Fagus grandifolia Ehrh.) in North America during the past century. Previous studies have suggested a positive relationship between disease severity and both bark nitrogen content and tree size, presumably due to higher rates of infestation by beech scale insects, which allow more extensive infection of the tree by Nectria fungi. Recent concerns about nitrogen saturation in northeastern forests, particularly in old-growth forests, led us to examine patterns of disease severity as a function of bark tissue nitrogen content in old-growth and second-growth forests in the Adirondack region of New York and northern Maine. Trees growing in old-growth stands possessed significantly higher levels of bark nitrogen than similarly sized trees in second-growth forests. The severity of disease symptoms was more acute in the old-growth forests and was positively correlated with the percent nitrogen of the bark in both forest types. Comparisons of the coefficients of variation between beech bark sampled from disease-free forests in the upper peninsula of Michigan and that sampled from diseased forests indicated that elevated bark nitrogen concentrations in diseased trees were a cause and not an effect of disease presence. While there was no difference in disease severity between control and nitrogen-fertilized forests in Maine, these forests had both been exposed to the disease for longer time periods than the other studied forests and they are likely approaching nitrogen saturation.
Nitrogen mineralization dynamics following the establishment of a loblolly pine plantation
Authors: Li Qingchao , Allen H Lee , Wilson Carlos A
Published: March 2003

The USDA Forest Service initiated a national study in the early 1990s to examine the effects of organic matter removal, compaction, and vegetation control on tree growth and soil processes at several locations across the United States and Canada. Our study was undertaken on the Lower Coastal Plain of North Carolina installation during the second and the fifth growing seasons following loblolly pine (Pinus taeda L.) plantation establishment. We used the in situ soil core incubation method to assess net N mineralization, and collections were conducted monthly from March to December in 1993 and 1996. The largest differences in N mineralization resulted from soil type differences between blocks. Organic matter removal did not affect N mineralization in either year; however, compaction reduced N mineralization during both years. Vegetation control had a pronounced positive effect on N mineralization and was only slightly less important as compared with soil type. Mineralization rates in year 5 were 80% less than in year 2. We hypothesized that the high N mineralization rates in year 2 may be related to a decrease in the input of soluble organic C following harvest (reducing immobilization), a quick mineralization of microbial N, fluctuating soil temperature and water conditions, and fine roots and litter biomass input following harvest.
Radial growth of hardwoods following the 1998 ice storm in New Hampshire and Maine
Authors: Smith Kevin T , Shortle Walter C
Published: March 2003

Ice storms and resulting injury to tree crowns occur frequently in North America. Reaction of land managers to injury caused by the regional ice storm of January 1998 had the potential to accelerate the harvesting of northern hardwoods due to concern about the future loss of wood production by injured trees. To assess the effect of this storm on radial stem growth, increment cores were collected from northern hardwood trees categorized by crown injury classes. For a total of 347 surviving canopy dominant and subdominant trees, a radial growth index was calculated (mean annual increment for 19982000 divided by the mean annual increment for 19951997). Sugar maple (Acer saccharum Marsh.), yellow birch (Betula alleghaniensis Britt.), white ash (Fraxinus americana L.), and red maple (Acer rubrum L.) categorized in injury class A (crown loss of less than one-half) had mean growth index values of approximately 1.0, indicating no loss of mean radial growth after 3 years. For injury class B (crown loss of one-half to three-quarters) and class C (crown loss greater than three-quarters), growth index values significantly decreased for sugar maple, yellow birch, and red maple. For white ash, growth index values of classes B and C were not significantly different from those of class A trees. Growth index values of A. saccharum and A. rubrum in injury class C were the lowest of those measured. These results indicated that the severity of growth loss due to crown injury depends on tree species and crown replacement as well as the extent of crown loss.
Whole-seedling biomass allocation, leaf area, and tissue chemistry for Douglas-fir exposed to elevated CO2 and temperature for 4 years
Authors: Olszyk David M , Johnson Mark G , Tingey David T , Rygiewicz Paul T , Wise Claudia , VanEss Erica , Benson Annick , Storm Marjorie J , King Richard
Published: March 2003

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown under ambient or elevated ( ambient + 180 µmol·mol1) CO2 and ambient or elevated (ambient + 3.5°C) temperature in outdoor, sunlit chambers with a field soil. After 4 years, seedlings were harvested and measured for leaf area, leaf, fine root (<1 mm diameter), and structural (buds, branches, stems, main root, and lateral roots >1 mm in diameter) dry masses, and leaf and fine root C/N ratio, percent sugar, and percent cellulose. Elevated CO2 did not affect biomass production or allocation for any plant organ but increased specific leaf mass, leaf C/N ratio, and percent sugar and decreased the ratio of leaf area to structural weight and leaf percent cellulose. Elevated temperature tended to reduce biomass allocation to leaves and leaf sugar concentration. Fine root percent sugar tended to increase with elevated temperature but only at elevated CO2. Therefore, for Douglas-fir seedlings growing under naturally limiting soil moisture and nutrition conditions, elevated CO2 and temperature may have little impact on biomass or leaf area except for reduced specific leaf mass with elevated CO2 and reduced biomass allocation to leaves with elevated temperature. However, both elevated CO2 and temperature may alter leaf chemistry.
Urea fertilizations of a Norway spruce stand: effects on nitrogen in soil water and field-layer vegetation after final felling
Authors: Ring Eva , Bergholm Johan , Olsson Bengt A , Jansson Gunnar
Published: March 2003

Effects of previous fertilization with N (in total, 600 kg urea-N·ha1 applied in 1976, 1980, and 1985) were studied after final felling in 1992 of a Norway spruce (Picea abies (L.) Karst.) stand in southern Sweden. The logging residues were removed from the site. In the clearcut, soil water at 50 cm depth was sampled 16 times with ceramic suction samplers (P80) in experimental plots during 19921995. The biomass and N content of the field layer was measured on seven occasions. The N storage of the field layer was significantly (p < 0.05) higher in the urea treatment than in the control. Significant interactions between treatment and time were found in soil water for nitrate-N and total N but not for ammonium-N, organic N, and pH. During the first year after final felling, nitrate-N tended to increase faster in the urea treatment than in the control. After a period with similar concentrations in both treatments, nitrate-N in the urea treatment declined while at the same time, a peak was observed in the control showing four to seven times higher concentrations than in the urea treatment. At the end of the study, the concentrations still appeared to be highest in the control. Thus, the study demonstrated the importance of using a sufficiently long study period when investigating environmental effects. Total leaching of nitrate-N from the urea treatment was roughly 40% ([Formula: see text]20 kg·ha1) less than that from the control. The difference in leaching may be partly explained by the greater accumulation of N in the field-layer vegetation in the urea treatment.
Growth and nutrition of three conifer species across site gradients of north coastal British Columbia
Authors: Kranabetter J M , Banner A , Shaw J
Published: March 2003

We compared height growth and nutrition (foliar nutrient concentrations and retranslocation rates from 1-year-old needles) of second-growth plantations on imperfectly drained, lower productivity cedarhemlocksalal forests with those of more productive ecosystems of north coastal British Columbia. Soils ranged from deep organic profiles to well-drained mineral soils derived from igneous to metamorphic bedrock. Leader increments on imperfectly drained sites were smaller than on well-drained sites, averaging 42% less for western hemlock (Tsuga heterophylla (Raf.) Sarg.), 56% less for Sitka spruce (Picea sitchensis (Bong.) Carrière), and 32% less for western redcedar (Thuja plicata Donn ex D. Don). Strong linear correlations were found between leader increment and foliar N, P, and S concentrations for all three tree species, and baseline foliar data for productive sites were presented. The foliar N ratios with P, S, and K were consistent across sites and indicated that many key foliar nutrients increased proportionally to the availability of N. A comparison of nutrient concentrations between current and 1-year-old foliage generally showed little difference on poorer sites, which suggested that there had been no retranslocation of nutrients from young needles within trees to compensate for low soil nutrient availability. This study confirmed the inherently low productivity of cedar-hemlock-salal forests, especially on granodiorite and gneissic diorite bedrock types, and suggested the need for site treatments or long rotations for sustainable management.
Belowground biomass, production, and carbon cycling in mature Norway spruce, Maine, U.S.A.
Authors: Cronan Christopher S
Published: March 2003

Two 55-year-old stands of Norway spruce (Picea abies (L.) Karst.) were sampled to determine belowground biomass, production and decomposition of fine and small roots, litterfall and litter decay rates, soil respiration rates, and carbon cycling patterns. Mean biomass of live fine (<1 mm) Norway spruce roots to a soil depth of 40 cm was 359 ash-free dry g·m2, whereas biomass of live fine + small roots ([Formula: see text]3 mm) amounted to 561 g·m2. Mean root production averaged 297 g·m2·year1for roots <1 mm and 418 g·m2·year1for roots [Formula: see text]3 mm. By comparison, needle litter production was 205 g·m2·year1. Norway spruce roots [Formula: see text]3 mm decomposed at a rate of 9.5% of total root mass per month during the growing season, compared with a needle litter annual decay rate of 22.3%·year1. A partial carbon budget for Norway spruce indicated that annual needle litterfall mass was 98 g C·m2·year1, and annual carbon release from fresh litter decay was approximately 22 g·C·m2·year1. During the growing season, monthly CO2flux from soil respiration was 69 g C·m2·month1, belowground C allocation to net production of roots [Formula: see text]3 mm was 33.5 g C·m2·month1, and C release from decomposition of roots [Formula: see text]3 mm was 31 g C·m2·month1. These values were also extrapolated to annual estimates of C fluxes.
How forest models are connected to reality: evaluation criteria for their use in decision support
Authors: Stage Albert R
Published: March 2003

Choice of a model for exploring forest management options depends on the decision space defined by the actions, indicators, ecosystem scope, and cybernetic context of the decisions. To be useful in a particular decision context, candidate models must include all relevant hypotheses of effects of the actions on the indicators in a spatial and temporal structure appropriate for the particular decision. The architecture of a suitable model is implied or constrained by these components of the decision space. A set of attributes for assessing a model's suitability for decision support is proposed. In addition to a firm foundation in science, decision support models should provide predictions with quantified bias and precision, and without artifacts that influence choice of management alternatives. Descriptions of information flow across levels of integration within and between models and between models and field observations should be included in model descriptions. Schematic diagrams of these flows illustrate several broad classes of how modelling systems may be linked to reality to improve their utility.
Yield prediction errors of a stand density management program for black spruce and consequences for model improvement
Authors: Newton P F
Published: March 2003

The objectives of this study were to (i) quantify the prediction error associated with estimating density (N (stems/ha)), quadratic mean diameter (Dq (cm)), basal area (G (m2/ha)), total volume (Vt (m3/ha)), and merchantable volume (Vm (m3/ha)) using a stand density management decision-support program (SDMDSP) developed for black spruce (Picea mariana (Mill.) BSP) plantations and (ii) given objective i, assess model adequacy by examining the relationship between prediction error and model input variables (prediction period, site index, initial density, and number of thinning treatments) by yield variate. Specifically, the SDMDSP was evaluated by comparing its yield predictions with corresponding measured values (n = 44) within 19 black spruce plantations. The resultant tolerance intervals indicated that 95% of the relative errors associated with future predictions would be within the following limits 95% of the time (minimummaximum): (i) 27.3 to 29.7% for N, (ii) 26.1 to 14.3% for Dq, (iii) 48.3 to 26.1% for G, (iv) 64.3 to 37.7% for Vt, and (v) 87.0 to 73.0% for Vm. Graphical analysis indicated that errors for Vt and Vm were associated with the data from thinned plantations. This result is discussed within the context of residual stand structure variation and response delay from which recommendations for model improvement are derived.
Forest-level models and challenges for their successful application
Authors: Nelson John
Published: March 2003

Significant advances have been made that integrate landscape issues in forest-level models. These advanced models are designed to simulate and evaluate economic, ecological, and social goals that are included in the management of forests. The application of multiple-objective heuristics such as tabu search and simulated annealing, combined with remarkable advances in computing power, now allows us to explore highly complex management scenarios over long time horizons and over vast geographic scales. While the power of these decision support systems is highly appealing, and even intoxicating, we still face three sobering challenges on the path towards generating credible forecasts. First, advanced data acquisition and data management systems are needed to support these systems. Data management systems must have high storage capacity, be capable of rapid updates, and accommodate a seemingly endless demand for queries from customers, government agencies, and the public. Planning is an interdisciplinary, hierarchical process, and team members have different data demands, depending on where they fit in the hierarchy. Second, the models must be verified. Multiple-objective models have dozens of parameters, and when these are combined with random search techniques, they become difficult to understand and replicate. Thorough sensitivity analysis is needed to test model parameters, goal weights, and assumptions of uncertainty. Finally, our ability to formulate and run large-scale, long-term forecasting models often exceeds the scientific credibility of the data, especially for complex forest ecosystems. In the absence of critical thinking, such powerful models can become dangerous weapons.
Analysis and planning systems for multiresource, sustainable forestry: the Heureka research programme at SLU
Authors: Lämås Tomas , Eriksson Ljusk Ola
Published: March 2003

Forest management in Sweden today, as in many other places, involves the management of multiple resources for diverse purposes, such as promoting biodiversity, recreation, hunting, carbon sequestration, and reindeer herding as well as wood production. Sustainability is no longer related only to timber production; it now embraces the composition, processes, and functions of the entire ecosystem. Moreover, pressure from substitute products requires the production of timber, wood fuel, etc., to be economically competitive. The increased complexity of forest management has intensified the need for improved instruments for analysis and decision support. In response to this, a research programme aiming to develop new systems for forest management analysis and planning was recently initiated at the Forest Faculty, Swedish University of Agricultural Sciences (SLU), in which research efforts in different fields are being linked in a common framework to generate models and methods with the following desired attributes. The new systems should be designed with (i) a modular structure to allow the development of different applications, (ii) the landscape as the basic planning unit, (iii) the tree as the basic unit of projection of the tree layer, (iv) models of the interactions between processes and the management of the tree layer, and (v) models for evaluating risks and uncertainties in the data acquired and model projections. We believe that the separation of the system into a decision phase and a projection phase should facilitate the analysis of large and complex multiresource planning problems and suggest in this paper possible avenues for implementing such a feature. Since spatial problems are inherent in many biodiversity-related applications, we propose that appropriate spatially structuring principles should be included in the design of the system. The complex trade-offs involved when selecting ecosystem models in relation to the purpose of the analysis and data availability are highlighted.
Predicting the effect of thinning on growth of dense balsam fir stands using a process-based tree growth model
Authors: Raulier Frédéric , Pothier David , Bernier Pierre Y
Published: March 2003

A tree-level process-based model of forest growth is used to investigate the effects of thinning on the growth of balsam fir (Abies balsamea (L.) Mill.) in stands that have almost reached commercial maturity but that have never been thinned. The model is applied to predict the 20-year growth of a stand following a recently established thinning experiment in which four thinning treatments were tested. The combination of stand properties and treatment type is quite particular and the resulting long-term effect on growth cannot be evaluated based on past experiments. The objectives of the study are to provide estimates of treatment outcome and of their errors over the appropriate time frame for decision making. This is achieved by representing growth processes through functions empirically adjusted to field observations while limiting the inputs of the model to what are usually available through regular forest inventory. Simulations suggest that 20-year growth of individual trees from the smaller diameter classes is improved by the treatments, but the growth of larger trees (>0.1 m3) is left unchanged. When the model error is not taken into account, the results after 20 years suggest, with a confidence level greater than 95%, that the merchantable volume of the treated plots does not recover to the level found in the untreated control plots, a result contrary to the initially expected effect of such thinning. By including modelling uncertainty, however, the confidence level associated with such a result is reduced to 70%. Such an inclusion prevents the misuse of the model predictions too far into the future.
Growth and yield of tropical moist forest for forest planning: an inquiry through modeling
Authors: Glauner R , Ditzer T , Huth A
Published: March 2003

For the forest growth and yield calculations presented here, the process-based model FORMIX was applied in combination with a geographic information system. The study was carried out for the 55 084 ha of the Deramakot Forest Reserve, which consists of heavily logged and degraded lowland dipterocarp forest. FORMIX was used to assess forest development with and without timber harvesting. Three scenarios were compared: undisturbed forest growth and two reduced-impact timber harvesting scenarios ("textbook" and "borderline"). The latter differ in the number of seed trees retained after harvesting. The simulations reveal that timber harvesting is feasible, although stands are presently degraded. Achievable harvesting levels differ widely from 200 to 10 000 m3·year1for the next 40 years for the textbook and borderline scenario, respectively. A future increase up to 80 000 m3·year1is possible if all silvicultural and management standards are strictly observed. An analysis of stand development reveals that the portion of commercial dipterocarps decreases with time, while the portion of pioneer and understorey species increases. Future stands do not contain as many trees >60 cm DBH (diameter outside bark at 1.3 m height above ground), whereas they contain more trees in lower diameter classes, ensuring adequate potential for future harvests.
RADIATION EFFECTS IN STAINLESS STEEL AND TUNGSTEN FOR USE IN THE ADS SPALLATION NEUTRON SOURCE SYSTEM
Authors: XU YONGJUN , WANG ZHIQIANG , ZHU JIAZHENG , MINAMISONO T. , MATSUTA K. , ZHENG YONGNAN , ZHOU DONGMEI , XU GUOJI , DU ENPENG , FU YOULIN , FUKUDA M. , MIHARA M. , ZHU SHENGYUN
Published: March 2003

Radiation effects have been studied in modified 316L stainless steel and commercially available stainless steel and tungsten by the heavy ion irradiation simulation and positron lifetime techniques. The experimental results show that the radiation resistant property of stainless steel is much better than that of tungsten, and the modified 316L stainless steel is the best among them. The stainless steel is a good choice for the beam window material of the ADS spallation neutron source system, and the modified 316L stainless steel is the best choice.
EXTENDED SELF-SIMILARITY AND THE MOST INTENSE VELOCITY STRUCTURES IN TURBULENT RAYLEIGH–BÉNARD CONVECTION
Authors: CHING EMILY S. C. , CHOY T. P. , CHUI K. W.
Published: March 2003

It has been conjectured13 that the extended self-similarity measured in turbulent flows is an indication of the maximum velocity difference being scale-independent and thus the most intense velocity structures being shock-like. In this paper, we present analyses of velocity measurements in turbulent Rayleigh–Bénard convection that show further support to this conjecture.
HIGH FREQUENCY AHARONOV–BOHM OSCILLATIONS IN CARBON NANOTUBES
Authors: YANG LINFENG , JIANG JIE , DONG JINMING
Published: March 2003

We give a multiple-cycle quantum interference model and obtain magnetoresistance (MR) expression in the framework of the weak localization. The MR expression based upon finite phase-breaking length Lφ can explain well several experimental results about distinct negative magnetoresistance of carbon nanotubes. The higher-order oscillation peaks with magnetic flux exist in the MR can also be explained by our model. And a new method to measure the phase-breaking length Lφ of the single-wall carbon nanotubes has been proposed.
THERMODYNAMIC PROPERTIES OF THE PHASE TRANSITION TO SUPERCONDUCTING STATE IN THIN FILMS OF TYPE I SUPERCONDUCTORS
Authors: SHOPOVA D. V. , TODOROV T. P. , UZUNOV D. I.
Published: March 2003

The effect of magnetic fluctuations on the free energy, the order parameter profile and the latent heat at the equilibrium point of the first order phase transition to superconducting state in thin films of type I superconductors is considered. The possibility for an experimental observation of the fluctuation change of the order of the superconducting phase transition is briefly discussed. Numerical data for the order parameter jump and the latent heat of Al films are presented.
A NEW GENERALIZED JAYNES–CUMMINGS MODEL BASED ON TWO-MODE PHOTON NUMBER-DIFFERENCE AND OPERATIONAL PHASE
Authors: FAN HONG-YI , LU HAI-LIANG
Published: March 2003

A new generalized Jaynes–Cummings model based on two-mode photon number-difference and operational phase is presented. The excitation of the atom is proportional to the net variation of the competion of two modes of photons in some nonlinear process. The corresponding Hamiltonian is diagonalized by virtue of the supersymmetric transform.
RENORMALIZATION GROUP OF A TWO-DIMENSIONAL PATCHED FERMI SURFACE
Authors: FERRAZ A.
Published: March 2003

Using the renormalization group we calculate the single particle Green's function G and the momentum occupation function [Formula: see text] for a quasiparticle in a two-dimensional Fermi Surface (FS) composed of four symmetric patches with both flat and curved arcs in [Formula: see text]-space. We show that G develops an anomalous dimension as a result of the vanishing of the quasiparticle weight at the FS. [Formula: see text] is a continuous function of [Formula: see text] with an infinite slope at FS for CU*2/(1 - CU*2) < 1. This result resembles a Luttinger liquid and indicates the breakdown of Fermi liquid theory in this regime.
CO OXIDATION ON Ag(110): SURFACE RECONSTRUCTIONS CONTRA SUBSURFACE OXYGEN
Authors: BURGHAUS U. , BÖTTCHER A. , CONRAD H.
Published: March 2003

Transient CO2formation has been studied under "quasi-steady-state" measuring conditions by means of surface titrations. By this method the reactivity of the surface could be sampled as a function of time, thereby following the formation of the surface reconstruction induced by oxygen. The reactivity of the surface towards CO oxidation was reduced in the course of the developing surface reconstruction. A possible influence of subsurface oxygen on the CO2formation rates can be excluded.
GROWTH OF ULTRATHIN Rh FILMS ON Fe(100)
Authors: PFANDZELTER R. , LANG M. , WINTER H. , URAZGIL'DIN I.
Published: March 2003

The growth and structure of ultrathin Rh films on Fe(100) are studied by grazing scattering of 50 keV He projectiles, incident along "random" and low index surface lattice directions. Oscillations in the specular intensity for scattered ions indicate initial layer-by-layer growth, followed by multilayer growth on top of the two-monolayer film. Growth temperatures below about 400 K result in a persistent though rough layer growth up to higher coverages. From distinct maxima in the target current as a function of the azimuthal incidence angle, we deduce that growth is epitaxial and pseudomorphic.
HOLOGRAPHIC ANALYSIS OF KIKUCHI ELECTRON DIFFRACTION DATA FROM ${\rm Si}(111)(\sqrt{3}\times\sqrt{3}){\rm R}30^\circ{\rm -Al}$
Authors: GLANDER G. S.
Published: March 2003

Holographic analysis was applied to Kikuchi electron diffraction data collected from the [Formula: see text] structure to produce real-space images of the surface structure. Methods for calibrating the initial diffraction data are fully described. The images clearly show features caused by the Al atoms in the T4 absorption site. Measurements of the Al–Si bond length and the height of the Al above the top layer of Si agree with the values known from dynamical LEED studies.
6H- AND 4H-SiC(0001) Si SURFACE RICHNESS DOSING BY HYDROGEN ETCHING: A WAY TO REDUCE THE FORMATION TEMPERATURE OF RECONSTRUCTIONS
Authors: DIANI M. , DIOURI J. , KUBLER L. , SIMON L. , AUBEL D. , BOLMONT D.
Published: March 2003

In 6H- or 4H-SiC(0001) surface technology, a Si-rich 3 × 3 reconstruction is usually first prepared by heating at 800°C under Si flux, and two other most stable [Formula: see text] or [Formula: see text] reconstructions are obtained by further extensive annealing at higher temperatures ranging between 900 and 1250°C. The 3 × 3 Si excess is thus progressively depleted up to a graphitized C-rich surface. By crystallographic (LEED) and chemical surface characterizations (XPS and UPS), we show that all these reconstructions can be obtained at a unique, low formation temperature of 800°C if the Si richness is controlled before annealing. This control is achieved by exposing the 3 × 3 surface to atomic hydrogen at room temperature. This procedure allows one to etch or partially deplete the (3 × 3)-associated Si excess, and make it more comparable to the final Si coverages, required to form the less Si-rich [Formula: see text] or [Formula: see text] reconstructions. After annealing at 800°C, the latter reconstructions are no longer determined by the heating time or temperature but only by the initial Si coverage set by the H doses inducing the low temperature etching. The high temperature treatment, required to remove by sublimation a significant Si amount associated with the Si-rich 3 × 3 reconstruction, is thus avoided. Such a methodology could be applied to other binary systems in the formation of reconstructions that depends on surface richness.
ADSORPTION OF C60 ON Li-COVERED Ni(110) SURFACES
Authors: SALTAS V. , PAPAGEORGOPOULOS C. A.
Published: March 2003

In this paper the adsorption of C60 on Li-covered Ni(110) surfaces is investigated by means of Auger electron spectroscopy, low-energy electron diffraction and work function measurements, in ultrahigh vacuum. Deposition of C60 on the 1 × 2 Li-induced Ni(110) surface at 650 K causes the formation of islands with a 4 × 2 structure, where the C60 molecules adsorb along neighboring troughs of the substrate. At higher C60 coverages, the Li-induced 1 × 2 reconstruction of the Ni(110) surface is lifted and a 9 × 3 structure is formed, which finally ends in a semihexagonal structure, as in the case of C60 adsorption on clean Ni(110) surfaces. AES and LEED measurements suggest that charge is transferred from Li to the C60 molecules, which in a rough approximation was estimated to be around one electron per C60 molecule. The above estimated charge transfer to the C60 molecules is substantially smaller than that we have calculated when Li is adsorbed on C60-covered Ni(110) surfaces. Apparently, the order of Li and C60 deposition is very important for the charge transfer and the deposition of Li on C60-covered surfaces provides a substantially greater amount of charge to the C60 molecules.
A METHANOL–WATER COMPLEX STABILIZED ON A Zn(0001) SURFACE
Authors: VIJAYALAKSHMI S. , VINOD C. P. , KULKARNI G. U.
Published: March 2003

Coadsorption of water and methanol on a clean Zn(0001) surface has been investigated by employing X-ray photoelectron spectroscopy after exposing the surface at 80 K to the binary vapor from water–methanol liquid mixtures of varying compositions and subsequently warming the surface up to the room temperature. When the surface was exposed to the vapor from a mixture with water molefraction, xw, of 0.5, the proton abstraction and the C–O bond cleavage in methanol leading to methoxy (CH3O) and the hydrocarbon ( CH x) species respectively, occurs at a much higher temperature of 180 K, compared to 120 K in the case of pure methanol adsorption. For water-rich mixtures (xw = 0.7 and 0.9) molecular methanol is stabilized on the surface up to 200 K, beyond which water itself desorbs. For xw = 0.7, virtually no dissociation is observed up to 200 K. The increased stability of molecular methanol on the Zn(0001) surface is attributed to the surface-mediated hydrogen bonds that stabilize a water–methanol complex.
THERMAL DECOMPOSITION AND DESORPTION OF DIETHYLAMIDO OF TETRAKIS(DIETHYLAMIDO)ZIRCONIUM (TDEAZr) ON Si(100)
Authors: JEONG JOONHEE , LIM SUNGWON , YONG KIJUNG
Published: March 2003

The thermal decomposition pathway and desorption of diethylamido of tetrakis(diethylamido)zirconium [TDEAZr, Zr(N(C2H5)2)4] on Si(100) were studied using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). During TPD experiments, ethylethyleneimine (C2H5N=CHCH3), diethylamine [NH(C2H5)2], acetonitrile (CH3CN), ethylene (C2H4) and hydrogen (H2) desorbed as the main decomposition products of diethylamido, which was chemisorbed on Si(100) through the scission of the zirconium–diethylamido bond in TDEAZr. After TPD runs, the formation of silicon carbide and silicon nitride was observed on the surface by XPS, indicating that a complete decomposition of diethylamido proceeded. This could be a reaction pathway of C, N incorporation in the thin film growth using TDEAZr as a Zr precursor.
MAPPING REFERENCE CODE TO IRREGULAR DSPS WITHIN THE RETARGETABLE, OPTIMIZING COMPILER COGEN(T)
Authors: GRÉWAL GARY WILLIAM , WILSON CHARLES THOMAS
Published: March 2003

Generating high quality code for embedded processors is made difficult by irregular architectures and highly encoded parallel instructions. Rather than dealing with the target machine at every stage of the compilation, a promising new methodology employs generic algorithms to optimize code for an idealized abstraction of the true target machine. This code, called reference code, is then mapped to the real instruction set by enhanced genetic algorithms. One perturbs the original schedule to find a number of alternative (parallel) instruction sequences, and the other evolves feasible register assignments, if possible, for each sequence. This paper describes the strategy for mapping idealized code into actual code. The COGEN(T) system employs this methodology to produce good code for different commercial DSPs and ASIPs.
DATA ACQUISITION AND RECOGNITION OF FINGERPRINTS WITH LVQ
Authors: KHUWAJA GULZAR. A. , ABU-REZQ A. N.
Published: March 2003

A typical biometric system has three distinct phases. These are biometric data acquisition, feature extraction, and decision-making. The first step, the acquisition phase, is extremely important. If high quality images are not obtained, the next phase cannot operate reliably. Fingerprint recognition remains as one of the most prominent biometric identification methods. In this paper, we develop a prototype optical-based fingerprints data acquisition system using a CCD digital still camera to capture a complete impression of finger area required for accurately identifying an individual and present an image-based approach for online fingerprint recognition with the objective to increase the overall matching performance. The fingerprint images are matched based on features extracted with an adaptive learning vector quantization (LVQ) neural network to yield peak recognition of 98.6% for a random set of 300 test prints (100 fingers × 3 images). This system can be adopted as a multi-modal biometrics where two or more fingers are matched.
INCREASING THE AUTONOMY OF DELIBERATIVE AGENTS WITH A CASE-BASED REASONING SYSTEM
Authors: CORCHADO J. M. , LAZA R. , BORRAJO L. , YAÑES J. C. , VALIÑO M.
Published: March 2003

This paper shows how deliberative agents can be built by means of a case-based reasoning system. The concept of deliberative agent is introduced and the case-based reasoning model is presented. Once the advantages and disadvantages of such agents have been discussed, it will be shown how to solve some of their inconveniences, especially those related to their implementation and adaptation. The World Wide Web has emerged as one of the most popular vehicle for disseminating and sharing information through computer networks; a distributed agent-based solution for e-business, in which such agents have been used, is also presented and evaluated in this paper.
APPLICATION OF GENETIC ALGORITHMS TO A LARGE-SCALE MULTIPLE-CONSTRAINT VEHICLE ROUTING PROBLEM
Authors: MOURKOUSIS GEORGE , PROTONOTARIOS MATHEW , VARVARIGOU THEODORA
Published: March 2003

This paper presents a study on the application of a hybrid genetic algorithm (HGA) to an extended instance of the Vehicle Routing Problem. The actual problem is a complex real-life vehicle routing problem regarding the distribution of products to customers. A non homogenous fleet of vehicles with limited capacity and allowed travel time is available to satisfy the stochastic demand of a set of different types of customers with earliest and latest time for servicing. The objective is to minimize distribution costs respecting the imposed constraints (vehicle capacity, customer time windows, driver working hours and so on). The approach for solving the problem was based on a "cluster and route" HGA. Several genetic operators, selection and replacement methods were tested until the HGA became efficient for optimization of a multi-extrema search space system (multi-modal optimization). Finally, High Performance Computing (HPC) has been applied in order to provide near-optimal solutions in a sensible amount of time.
ON OPERATING STRATEGIES OF THE FUZZY ARTMAP NEURAL NETWORK: A COMPARATIVE STUDY
Authors: KUAN MEI MING , LIM CHEE PENG , HARRISON ROBERT F.
Published: March 2003

In this paper, the effectiveness of three different operating strategies applied to the Fuzzy ARTMAP (FAM) neural network in pattern classification tasks is analyzed and compared. Three types of FAM, namely average FAM, voting FAM, and ordered FAM, are formed for experimentation. In average FAM, a pool of the FAM networks is trained using random sequences of input patterns, and the performance metrics from multiple networks are averaged. In voting FAM, predictions from a number of FAM networks are combined using the majority-voting scheme to reach a final output. In ordered FAM, a pre-processing procedure known as the ordering algorithm is employed to identify a fixed sequence of input patterns for training the FAM network. Three medical data sets are employed to evaluate the performances of these three types of FAM. The results are analyzed and compared with those from other learning systems. Bootstrapping has also been used to analyze and quantify the results statistically.