bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in interstitial K+ and pH during exercise: implications for blood flow regulation
Authors: Juel Carsten 
Published: April 2008

The analysis of blood samples has clearly demonstrated that exercise is associated with the release of K+ and H+ from muscle. However, blood samples give only incomplete information about the ion changes in the muscle interstitium. Interstitial changes in ion composition may affect the transport properties of the sarcolemmal membrane, may affect fibre excitability and induce fatigue, and may affect sensory nerve endings. Therefore, to better understand muscle function, it is important to quantify the exercise-induced interstitial ion changes. Both interstitial K+ and H+ changes have been quantified with the microdialysis technique. Interstitial K+ accumulation is dependent on the intensity and duration of muscle activity and may reach 10 mmol/L during intense exercise, and the concentration in T-tubules may be even higher. Thus, interstitial K+ can reach a level that affects fibre excitability and the development of fatigue. It has also been demonstrated with microdialysis that the interstitial decrease in pH during muscle activity is larger than the reduction in blood pH. Ion changes in the interstitium may affect blood flow directly or indirectly. Infusion of K+ into the femoral artery in humans has demonstrated that blood flow is affected by changes in K+ as low as 0.1 mmol/L. The vasodilatory effect of K+ can be inhibited with simultaneous barium infusion, indicating that inward rectifier potassium (Kir)channels are involved. Acidosis has a direct effect on blood flow and an indirect effect, mediated by changes in other vasoactive compounds.
Modeling of freeway breakdown process with log-periodic oscillations
Authors: Bassan Shy , Polus Abishai , Faghri Ardeshir 
Published: April 2008

Urban and suburban freeways are designed to allow smooth traffic flow at high speed. However, when traffic demand is high or during irregular events, significant congestion may develop. Traffic breakdown occurs during the phase transition from dense congested stable (DCS) flow to breakdown flow. In this study, the process of freeway flow breakdown was investigated by calibrating models in the density–time plane using morning peak data from Interstate 66, a US highway connecting Washington, D.C., and Virginia. It was shown that the models, which describe the collective behavior of drivers using the mathematical property of the log-periodic oscillations (LPO) process, reflect suitably the phase transition in freeway traffic flow. The LPO process has been used in the past to model stock market crashes and the occurrences of large earthquakes. The cyclic properties of the LPO models developd in this study were found to identify the “critical transition period,” which triggers the traffic breakdown process. This period starts when the density rate of change reaches its maximum during the first cycle that follows the DCS flow regime. This triggers a breakdown of flow conditions, which occur 5–8 min after the density rate of change has achieved its maximum.
Have repeated applications of nitrogen and phosphorus to a loblolly pine plantation changed stand productivity and soil nutrient supply?
Authors: (Bennett) Phelan Jennifer , Allen H. Lee 
Published: April 2008

To develop a nitrogen (N) and phosphorus (P) fertilization regime that produces long-term increases in stand productivity and soil nutrient supply in loblolly pine plantations, a series of N + P fertilizer studies were established in the Southeastern United States. One of these installations was examined partway through the study to determine if changes to stand productivity and soil nutrient supply had already been achieved. Stand growth and foliar nutrient concentrations were measured for 6 years, and during the third year, a seedling bioassay was conducted with soil collected from the highest fertilization and nonfertilized treatments. Annual stand growth was increased by 14%–27% in the fertilized plots suggesting that the fertilizer regime improved stand productivity. However, results from the seedling bioassay showed that only P fertilization had caused changes in soil nutrient supply. Seedling P contents in the fertilized treatments were 3.6 times larger than those in the nonfertilized treatments. In contrast, total system N contents were equivalent in the fertilized and nonfertilized systems, and extractable nitrate (NO3–), ammonium (NH4+), and biologically active N were higher in the nonfertilized soils. Future measurements and seedlings bioassay assessments should be conducted to determine when and if long-term changes in soil quality and stand productivity are achieved.
Long-term outcome of precommercial thinning in northwestern New Brunswick: growth and yield of balsam fir and red spruce
Authors: Pitt Doug , Lanteigne Len 
Published: April 2008

A study was established between 1959 and 1961 to study the long-term responses of balsam fir ( Abies balsamea (L.) Mill.) and red spruce ( Picea rubens Sarg.) to precommercial thinning. Three nominal spacings of 4 ft (1.2 m), 6 ft (1.8 m), and 8 ft (2.4 m) were compared with an unthinned control in a randomized complete block design with five replicates. At the time of thinning, natural regeneration averaged 16 years of age, 8 years after harvest. Although thinning had minimal effect on gross total volume production over a 42 to 44 year observation period, actual spacings between 2.1 and 2.5 m produced an average of 360 m3·ha–1gross merchantable volume (GMV), representing a 21% gain over unthinned stands. The same spacings produced quadratic mean diameters of 21 and 23 cm, respectively, compared with 18 cm in the unthinned stands. These size increases translated to individual stem volume gains of 33% and 62%, significantly reducing the age at which thinned stands would meet a specified minimum requirement for merchantability or habitat. The mean annual increment of GMV ranged from 6 m3·ha–1·year–1in unthinned stands, to more than 7 m3·ha·–1·year–1in the thinned stands, and had not yet culminated an average of 50 years postharvest.
How to find the rare trees in the forest — New inventory strategies for culturally modified trees in boreal Sweden
Authors: Andersson Rikard , Östlund Lars , Kempe Göran 
Published: April 2008

Culturally modified trees (CMTs) in northern forests are rare traces of past human activity that provide unique information on past land use and the relationship between people and forests throughout history. There is an apparent need to provide probability sampling methods for these traces. This article describes the simulation and evaluation of circular plot sampling and strip surveying for estimating the density of culturally modified trees in 25 ha of a forest reserve in northern Sweden. CMTs were surveyed, documented, and prepared for use in simulator software and the bias, precision, and cost of different inventory strategies were calculated. For a given level of precision circular plot sampling was found to be more efficient than strip surveying for estimating the abundance frequencies of all CMTs. For smaller subpopulations of scarce CMT types, the strip-surveying method was superior. Probability sampling would be an important tool for examining larger areas and gaining more CMT information at a lower cost. The results are important for studies of cultural history in sparsely populated forested regions in northwestern North America, northern Scandinavia, and northern Russia, but there are also implications for finding other rare objects in forest ecosystems.
Modeling the decay of coarse woody debris in a subalpine Norway spruce forest of the West Carpathians, Poland
Authors: Holeksa Jan , Zielonka Tomasz , Żywiec Magdalena 
Published: April 2008

Coarse woody debris (CWD) is an important structural element in forests. Its role depends on the species, size, position, and decay rate. This paper reports an attempt to determine the total residence time of CWD across all decay classes and also within successive decay classes. We simulated the process of CWD decomposition for stem size and position (snags versus logs), using matrices of the transition of CWD between decay classes. The study was based on a sample of 2785 Norway spruce snags and logs measured twice over a 10 year period in a Carpathian subalpine forest. The revealed pattern of decomposition depended highly on CWD size. When log numbers were considered, the mean total residence time increased from 71 years for small logs (diameter < 23 cm) to 90 years for medium-sized logs (23–35 cm), and to 113 years for large logs (>35 cm). In terms of volume, the mean total residence times of logs were 47, 49, and 63 years for the three diameter categories. Still shorter were the mean total residence times for log mass: 34, 41, and 41 years for the three diameter categories. The pattern of decomposition depended highly on the CWD attributes taken into consideration. The differences in decay rate between log diameter categories are considerable when the number of logs is taken into account, but they practically vanish when log mass is considered.
Long-term spatial and structural dynamics in Acadian mixedwood stands managed under various silvicultural systems
Authors: Saunders Mike R. , Wagner Robert G. 
Published: April 2008

Using inventory data from a long-term silviculture experiment in east-central Maine, spatial models were developed to analyze 28 years (1974–2002) of stand structural dynamics. Differences in spatial pattern, species mingling, height differentiation, and relative stand complexity index (rSCI) were compared among five treatments: commercial clear-cutting, fixed diameter-limit, 5 year single-tree selection, three-stage shelterwood (both with and without precommercial thinning), and unharvested natural areas. Regardless of treatment, regeneration events (whether induced by natural breakup of the overstory or by harvesting) increased aggregation in spatial pattern and reduced species mingling, more so in the commercial clearcut and fixed diameter-limit treatments where hardwood densities were highest. Regular spatial patterns were rare. Height differentiation values for individual trees and stand-level mean rSCI were generally highest in untreated natural areas and 5 year selection treatments, intermediate in commercial clearcut and fixed diameter-limit treatments, and lowest in three-stage shelterwood treatments. After a brief adjustment period, precommercial thinning in a shelterwood treated stand generally increased species mingling, height differentiation, and rSCI. Two untreated natural areas exhibited divergent pathways of structural development. Dynamics in uneven-aged selection treatments more closely resembled that of the untreated natural areas than did the shelterwood, commercial clearcut, or fixed diameter-limit treatments.
Regional variation in wood specific gravity of planted loblolly pine in the United States
Authors: Jordan Lewis , Clark Alexander , Schimleck Laurence R. , Hall Daniel B. , Daniels Richard F. 
Published: April 2008

Loblolly pine ( Pinus taeda L.) is the most important plantation species in the southeastern United States and specific gravity (SG) is its most important wood quality trait. Analysis of annual ring SG of breast height (1.37 m) increment cores from 3957 trees representing 147 plantations across the species natural range showed that ring SG increases with increasing age and varies significantly among physiographic regions. The South Atlantic and Gulf regions had the highest ring SGs, while the Hilly and Piedmont regions had the lowest. Based on ring SG, the juvenile period averages 4.3 years, followed by 8.6 years of transition wood, with mature wood produced by year 13. Whole-core mean SG was significantly higher in the South Atlantic (0.486) compared with the other regions (mean = 0.455), which were not statistically different from each other. Trees from the South Atlantic have significantly higher whole-core SG because they contain significantly more latewood (40.1%) compared with trees growing in other regions (33.8%). Maps indicate that stands in the South Atlantic and Gulf regions have the highest SG at a given age. Stands growing on the northern and western fringe of the natural range of loblolly pine have the lowest whole-core SG.
An optimization model for locating fuel treatments across a landscape to reduce expected fire losses
Authors: Wei Yu , Rideout Douglas , Kirsch Andy 
Published: April 2008

Locating fuel treatments with scarce resources is an important consideration in landscape-level fuel management. This paper developed a mixed integer programming (MIP) model for allocating fuel treatments across a landscape based on spatial information for fire ignition risk, conditional probabilities of fire spread between raster cells, fire intensity levels, and values at risk. The fire ignition risk in each raster cell is defined as the probability of fire burning a cell because of the ignition within that cell. The conditional probability that fire would spread between adjacent cells A and B is defined as the probability of a fire spreading into cell B after burning in cell A. This model locates fuel treatments by using a fire risk distribution map calculated through fire simulation models. Fire risk is assumed to accumulate across a landscape following major wind directions and the MIP model locates fuel treatments to efficiently break this pattern of fire risk accumulation. Fuel treatment resources are scarce and such scarcity is introduced through a budget constraint. A test case is designed based on a portion of the landscape (15 552 ha) within the Southern Sierra fire planning unit to demonstrate the data requirements, solution process, and model results. Fuel treatment schedules, based upon single and dual wind directions, are compared.
Wood density and stocks of coarse woody debris in a northwestern Amazonian landscape
Authors: Chao Kuo-Jung , Phillips Oliver L. , Baker Timothy R. 
Published: April 2008

Coarse woody debris (CWD) is a rarely studied component of the carbon cycle. We report the first measurements of both CWD wood density and necromass in humid, lowland northwestern Amazonia, using both line-intersect and plot-based methods. Average CWD densities were not significantly different between clay-rich and white sand unflooded forests, but lower in floodplain forest (p ≤ 0.001). Necromass of CWD lying on the ground was also lower in the floodplain (10.3 ± 6.1 Mg·ha–1, mean ± 1 SE) than in the clay-rich (30.9 ± 5.4) and white sand (45.8 ± 7.3) forests (p ≤ 0.001, using the line-intersect method). These patterns are likely driven by disturbance history, species composition, and decomposition rates. Plot-based data showed that standing and fallen CWD together accounted for 6.4%–15.4% of total coarse aboveground vegetative mass (trees ≥10 cm diameter). Across humid, lowland neotropical forests, we show that wood densities of intact and partially decayed CWD are significantly related with live wood density at the same site (p = 0.026 and 0.003, respectively). We show that these relationships can be applied generally to estimate CWD wood density for humid, lowland neotropical forests wherever destructive sampling is not possible.
Effects of alternative harvesting methods on boreal forest spider assemblages
Authors: Matveinen-Huju Katja , Koivula Matti 
Published: April 2008

Forestry is among the most important disturbance forces in the boreal region, having caused drastic changes to the biota. Forest industries have recently introduced alternative logging techniques to better maintain forest diversity, but little is known on how these function. We studied the short-term effects of various logging methods on ground-dwelling spiders in Finland, using pitfall traps 1 year before and 2.5 years after logging. The compared logging regimes were (i) clear-cutting, (ii) retention felling, (iii) gap felling, (iv) thinning, and (v) control. We found that (1) clear-cutting and retention felling drastically changed the spider fauna. The abundance of forest species decreased with these methods, whereas most open-habitat species showed the opposite response, being caught only after logging. Moreover, multivariate analyses (nonmetric multidimensional scaling, multivariate regression trees) indicated that clear-cutting and retention felling produced similar spider faunas. (2) Increasing retention of trees caused less abrupt changes in spider fauna. Gap felling produced variable and intermediate responses, whereas thinning closely resembled control. We conclude that retention patches of a few tens of trees within clearcuts may not function as “lifeboats” for forest spiders; gap felling preserves some forest species but also supports the colonization of open-habitat species; and the studied thinning treatment well preserves the forest-floor spider assemblage.
Basal area growth impacts of dwarf mistletoe on western hemlock in an old-growth forest
Authors: Shaw David C. , Huso Manuela , Bruner Howard 
Published: April 2008

We investigated the effect of western hemlock dwarf mistletoe ( Arceuthobium tsugense (Rosend.) G.N. Jones ssp. tsugense ) on the 13 year basal area growth of large (>45.7 cm diameter at breast height) western hemlock ( Tsuga heterophylla (Raf.) Sarg.) trees in an old-growth forest in southwestern Washington state. We controlled for spatial effects on tree growth by utilizing twenty-seven 0.4 ha plots that had uninfected, lightly, moderately, and severely infected classes of trees present on each plot. Basal area growth was analyzed using analysis of covariance of a randomized block design that was a balanced design with four treatments (infection classes) and 27 replicates (blocks or 0.4 ha plots), with initial diameter as the covariate. Basal area growth was found to be significantly different among the infection classes (F[3,77] = 10.09 and p < 0.0001). Growth of the light and moderate infection classes was not detectably different from growth of uninfected trees. However, severely infected trees grew from 16% to 46% (mean = 36%) less than uninfected trees of the same initial diameter over the period of study (1991–2004). The large trees in this stand did not show growth impacts until they were severely infected.
Growth response following green crown pruning in plantation-grown Eucalyptus pilularis and Eucalyptus cloeziana
Authors: Alcorn Philip J. , Bauhus Jürgen , Smith R. Geoff B. , Thomas Dane , James Ryde , Nicotra Adrienne 
Published: April 2008

Pruning of live branches is performed to enhance wood quality in plantation trees. Stem, branch and wood properties may be altered following pruning from below, but the extent and duration of such effects are unknown for many plantation Eucalyptus species. The effect of 0%, 20%, 50%, and 70% green crown length removal on growth and wood quality was examined in 3.5-year-old plantation-grown Eucalyptus pilularis Sm. (blackbutt) and Eucalyptus cloeziana F. Muell. (Gympie messmate) trees on two subtropical sites in eastern Australia. Growth increment of the stem at breast height was not affected by 20% crown removal. However, stem increment at breast height was reduced for up to 8 months with 50% crown removal and up to 12 months with 70% crown removal. Pruning had no impact on height growth. However, the height of trees pruned to 70%, relative to the height of the surrounding unpruned trees, was temporarily reduced 12 months after pruning in both species. Stem form, stem taper, wood density, and residual branch growth above the pruned zone were unaffected by pruning. Owing to the fast vertical crown expansion, trees were able to rapidly compensate for leaf area removal without long-term reductions in stem growth. The implications for management operations utilizing pruning as a means of enhancing timber quality are discussed.
Effects of competitor spacing in a new class of individual-tree indices of competition: semi-distance-independent indices computed for Bitterlich versus fixed-area plots
Authors: Stage Albert R. , Ledermann Thomas 
Published: April 2008

We illustrate effects of competitor spacing for a new class of individual-tree indices of competition that we call semi-distance-independent. This new class is similar to the class of distance-independent indices except that the index is computed independently at each subsampling plot surrounding a subject tree for which growth is to be modelled. We derive the effects of distance for this class as the expected value over independent samples containing a particular subject tree. In a previous paper, we illustrated distance effects implicit in eight indices of the distance-dependent class. Here, we present distance effects of four semi-distance-independent indices: density, sum of diameters, basal area, and tree-area ratio; each determined for small fixed-area plots of 0.04 ha and for Bitterlich samples of 6 m2·ha–1. We show that several members of this new class have distance effects very similar to the distance-dependent class and should, therefore, be equally effective in accounting for competitive effects in individual-tree increment models. The comparisons should inform selection of competition indices and sampling designs for growth modelling.
Physiological trade-offs associated with methyl jasmonate - induced resistance inPinus radiata
Authors: Gould Nick , Reglinski Tony , Spiers Mike , Taylor Joe T. 
Published: April 2008

Methyl jasmonate (MeJA) can induce defence responses in plants to pathogen attack, but it can also have consequences for plant growth. The transient effects of exogenous MeJA treatment on the resistance of Monterey pine ( Pinus radiata D. Don) seedlings to Diplodia pinea (Desm.) Kickx. and some physiological parameters affecting the impact of treatment on seedling growth were investigated. Following foliar application of 4.5 mmol·L–1MeJA, disease resistance was greatest 1–2 weeks after treatment and declined with time thereafter. Elevated disease resistance was accompanied by a reduction in seedling growth rate the second week following MeJA treatment. Thereafter, seedling growth rate recovered and exceeded that of the control seedlings 4–5 weeks after MeJA treatment. Within hours of MeJA treatment, reductions in both the capacity of photosystem II and transpiration rate were observed, resulting in a concomitant reduction in net CO2uptake rate. The slight reduction in transpiration rate was also associated with an increase in needle water potential. Longer term measurements showed no effect of MeJA on photosynthetic rate, transpiration rate, chlorophyll content, or shoot water potential and thus could not account for the elevated growth rate observed 4–5 weeks after treatment.