bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sudden and sustained response of Acacia koa crop trees to crown release in stagnant stands
Authors: Baker Patrick J. , Robinson Andrew P. , Ewel John J. 
Published: April 2008

We examined the growth response of Acacia koa Gray (koa) in dense (10 000 trees/ha), ~25-year-old, second-growth stands on Hawai‘i to crown release (thinning) and grass control. Koa diameter increment increased within 2 months of thinning across the range of residual densities (200–900 trees/ha). After 3 years, diameter increment in the most intense thinning treatment was 180% greater than in the control treatment (1.4 vs. 0.5 cm/year); in the least intense thinning treatment diameter increment was 100% greater than the control (1.0 vs. 0.5 cm/year). Koa’s growth response was independent of all measures of tree size (diameter at breast height, height, and leaf area) across the range of tree sizes sampled. A grass control treatment to determine if reduced competition for soil water would improve koa growth showed no improvement in growth response. Koa phyllode δ13C values, which represent an integrated measure of tree water status, showed no evidence of tree water stress (mean δ13C = –28.3‰) and were not significantly different between the grass removal and control treatments. These results demonstrate that koa is capable of responding quickly and positively to crown release despite years of suppressed growth and suggest that landowners interested in managing koa forests may have considerable flexibility in the timing and application of thinning treatments to koa stands.
Somatic embryogenesis in Greek fir
Authors: Krajňáková Jana , Gömöry Dušan , Häggman Hely 
Published: April 2008

To induce somatic embryogenesis of Greek fir, Abies cephalonica Loud., the influence of different cultivation media, sampling dates, and cold treatment storage were examined. The initiation frequencies ranged from 1% to 25%. The sampling date had a significant effect on the initiation of embryogenic cultures and a high frequency was observed within a 5 week window. The effect of cone storage, composition of initiation media, and the medium by storage interaction also remained nonsignificant after 3 and 10 months of proliferation growth. At the maturation phase, the highest tested concentrations of abscisic acid (ABA), 16 and 32 µmol/L, increased both the capability of embryogenic cell masses (ECMs) to produce embryos and the mean number of embryos. Of the two tested carbohydrates, maltose-containing media produced more embryos altogether (1943, on the average of 22.3 embryos per gram fresh mass) and 76% of the ECMs were able to produce embryos when compared with the corresponding values (152, on the average 3.0 embryos per gram fresh mass) and 15.3%, respectively, on sucrose-containing medium. However, 93.5% of embryos on maltose-containing medium died during the germination phase, whereas the corresponding percentage on sucrose-containing medium was 78.2%.
An examination of species-specific growing space utilization
Authors: Lhotka John M. , Loewenstein Edward F. 
Published: April 2008

A comparison is made among the size–density relationships of sugar maple ( Acer saccharum Marsh.), European beech ( Fagus sylvatica L.), Norway spruce ( Picea abies (L.) Karst), lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.), eastern white pine ( Pinus strobus L.), Scots pine ( Pinus sylvestris L.), loblolly pine ( Pinus taeda L.), and Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii ). Species-specific minimum density of full site occupancy (NMCA) and average maximum density (NAMax) equations were developed using forest inventory data and existing models. NMCA and NAMax estimates were used to compare species growing space utilization over a range of stand diameters (12–50 cm). Results suggest growing space utilization varies among the evaluated species and that species differences may change over the diameter range evaluated. Analysis also highlights that a growing space usage gradient is present across species. One end of the gradient is occupied by species that maintain higher densities at small sizes and exhibit greater rates of density decline as mean diameter increases. In contrast, other species maintain lower densities at small diameter, but have lesser rates of density reduction as diameter increases. Finally, results highlight the importance of using species-specific models when quantifying size–density relationships and developing stand-density management regimes.
Large-scale spatial patterns of forest structural diversity
Authors: McRoberts Ronald E. , Winter Susanne , Chirici Gherardo , Hauk Elmar , Pelz Dieter R. , Moser W. Keith , Hatfield Mark A. 
Published: April 2008

Forest structural diversity was estimated for an ecological province in the north-central region of the United States of America using data for nearly 350 000 trees observed on >12 000 forest inventory plots. Each plot was 672 m2 in area, and the sampling intensity was approximately 1 plot/2400 ha. Two indices were used for each of two commonly and accurately measured inventory variables: species count and the Shannon index for tree species and standard deviation and the Shannon index for tree diameter. The primary results of the study were fourfold: (i) ranges of spatial correlation for diversity indices were small, on the order of 5–10 km, (ii) high proportions of provincewide diversity were realized for circular areas with radii as small as 15 km, (iii) diversity for both species and diameter exhibited strong northwest to southeast spatial patterns, and (iv) plot-level α diameter diversity was highly correlated with mean plot-level tree diameter.
Controlling coarse woody debris inventory quality: taper and relative size methods
Authors: Woodall C. W. , Westfall J. A. 
Published: April 2008

Accurately measuring the dimensions of coarse woody debris (CWD) is critical for ensuring the quality of CWD estimates and, hence, for accurately estimating forest ecosystem attributes (e.g., CWD carbon stocks). To improve the quality of CWD dimensional measurements, the distribution of taper (ratio of change in diameter and length) and relative size (RS; ratio of length and large-end diameter) of CWD pieces across the US were examined. Additionally, an outlier identification technique was developed by predicting the median and interquartile range of taper and RS as a function of large-end diameter, length, and decay class by major species group. The median CWD taper and RS across the US were 1.268 cm/m and 0.280 m/cm, respectively, with notable outliers. The taper and RS outlier identification protocol rapidly identified nearly 3% of study observations as outliers. Incorporation of CWD taper and RS outlier identification protocols into field data recorders may allow efficient control of measurement errors during field inventories.
Silvicultural responses of two spruce plantations to midrotation commercial thinning in New Brunswick
Authors: Pelletier Gaetan , Pitt Douglas G. 
Published: April 2008

A midrotation commercial thinning experiment conducted in two independent spruce plantations compared several tree selection strategies as both early (age 19 or 24 years) single and double (again at age 30 or 34 years) entries over a 16 year period. A delayed (age 30 or 32 years) single-entry thinning and unthinned portions of the plantations served as references for the other treatments. With the exception of 50% systematic row thinnings, removal intensities were held relatively constant at about 40% of stand basal area. All of the thinning treatments satisfied the objectives of focusing diameter and volume growth on a reduced number of stems and making merchantable volume available during the rotation. Early single-entry thinning allowed 30–50 m3/ha to be harvested, increasing quadratic mean diameter and mean merchantable volume per stem at the end of the observation period by 10% and 24%, respectively, over unthinned stands. A second thinning removed an additional 48–64 m3/ha and increased diameter and volume gains to 25% and 71%, respectively. Only marginal differences were observed between the tree-selection strategies, and there were no overall gross total or gross merchantable volume gains or losses associated any of the thinning treatments relative to the unthinned plantations.
Dynamics of jack pine at the southern range boundary in downeast Maine
Authors: Barton Andrew M. , Grenier Daniel J. 
Published: April 2008

Great Wass Island in Maine supports a large population of Pinus banksiana Lamb. (jack pine) at its southern range boundary. Nearly monospecific stands occur on outcrops and coastal plateau bogs. In contrast to typical populations of this species, six stands exhibited old trees, multiaged structure, and continuous but pulsed establishment despite a lack of widespread fire. Unfavorable soil conditions appear to explain the presence of self-perpetuating populations in this study area, across the geographic range for P. banksiana, and for similar shade-intolerant pine species. Pinus banksiana stands on outcrops exhibited synchronous age structure peaks and included many trees over 150 years old. In contrast, coastal plateau bog stands were younger, were not synchronized in terms of age structure, and contained few large dead trees, suggesting turn-of-the-20th century invasion of these bogs. Analysis of historical aerial photographs furthermore reveals substantial infilling of bogs by P. banksiana since 1940. Although it appears to be an inconsistent and slow process, coastal plateau bog infilling warrants further investigation because of the regional rarity of this ecosystem type.
Effect of interannual climate variations on radial growth of jack pine provenances in Petawawa, Ontario
Authors: Savva Y. , Bergeron Y. , Denneler B. , Koubaa A. , Tremblay F. 
Published: April 2008

Effect of interannual climate variations on radial growth was compared among jack pine ( Pinus banksiana Lamb.) of diverse geographical origins in a 41-year-old common-garden experiment in Petawawa, Ontario. Provenance experiments established from seeds transferred from different parts of a species range (from the northern United States to northern Canada) to the same environment might be considered as a simulation model of climate change and a shift of climate zones. The following questions are addressed: Did the response of growth to interannual climate variations differ among the provenances transferred within the experimental site? What climatic factors affect interannual growth variations of jack pine provenances? Tree-ring chronologies for 16 populations were developed for the period 1970–2004. The best climate predictors of radial growth were precipitation of June and March of the current year and precipitation of December of the previous year. Although, climatic factors affecting growth were similar between the provenances, absolute radial growth was proportional to the growth potential of the provenances. We conclude that variability due to seeds origins is not a significant source of variation for dendroclimatic studies of jack pine. Increased frequency of summer droughts might result in a growth decrease of jack pine.
Patterns of throughfall deposition along a transect in forest edges of silver birch and Corsican pine
Authors: Wuyts K. , De Schrijver A. , Staelens J. , Gielis M. , Geudens G. , Verheyen K. 
Published: April 2008

In two adjacent forest stands in Flanders, one dominated by Corsican pine ( Pinus nigra subsp. laricio Maire) and another dominated by silver birch ( Betula pendula Roth), throughfall deposition was monitored along a transect perpendicular to the forest edge exposed to the prevailing wind direction. Throughfall deposition of Na+, K+, Ca2+, Mg2+, NH4+, NO3–, Cl–, and SO42–was examined on forest edge patterns expressed in the depth of influence of the edge effect (forest edge distance) and the level of enhancement at the edge (forest edge enhancement). In addition, an integrated forest edge enhancement factor was computed that incorporates these two parameters. Our results show that the edge effects on throughfall deposition of Na+, Cl–, the sum of so-called base cations, the sum of potentially acidifying ions, and the sum of inorganic nitrogen (NH4+ + NO3–) are more pronounced in the pine stand. The edge zone of the pine stand receives as a result of the edge effect 9.4 times more extra potentially acidifying ions and 12.7 times more extra inorganic nitrogen than the birch stand. We conclude that an appropriate design or conversion of the edge structure, from high-density Corsican pine plantations into lower density deciduous forests, can reduce the input of acidifying and eutrophying pollutants in the forest edge.
The influence of basswood (Tilia americana) and soil chemistry on soil nitrate concentrations in a northern hardwood forest
Authors: Page Blair D. , Mitchell Myron J. 
Published: April 2008

In the Arbutus Lake Watershed in the Adirondack Mountains, New York, two nearly adjacent catchments (14 and 15) varied significantly in volume-weighted stream water nitrate (NO3) export (54 and 17 μequiv.·L–1, respectively; P < 0.001). The most notable differences between the catchments were that Catchment 14 had significantly higher soil Ca concentrations and patches of basswood ( Tilia americana L.). We evaluated the possible contributions of basswood and soil Ca concentrations to soil water NO3 concentrations. Among the major overstory tree species, basswood leaf litter had the lowest C:N ratios, highest Ca concentrations, and among the lowest lignin:N ratios. Basswood basal area was significantly related to soil water NO3 concentrations (R = 0.46, P = 0.01). Forest floor and mineral soil Ca concentrations were positively correlated with basswood basal area and negatively correlated with American beech ( Fagus grandifolia Ehrh.) basal area. Our results suggest that a relatively low-density, calciphilic species such as basswood may create, given the proper soil conditions, hotspots with elevated soil water NO3 concentrations. These hotspots result from the convergence of high soil Ca concentrations, due mostly to soil geology, with relatively labile litter substrate available for N mineralization and nitrification.
Characterization of diameter distribution data in near-natural forests using the Birnbaum–Saunders distribution
Authors: Podlaski Rafał 
Published: April 2008

The purpose of this study is to investigate the suitability of the Birnbaum–Saunders distribution to model diameter at breast height (DBH) distributions of near-natural complex structure silver fir ( Abies alba Mill.) – European beech ( Fagus sylvatica L.) forests. The investigations were carried out in Świętokrzyski National Park, situated in Central Poland. To estimate the parameters of the Birnbaum–Saunders distribution, three methods were used: the maximum likelihood method (MLE) and the mean–mean estimator, the modified moment method (MME), and the graphical method (GME). The empirical DBH distributions in near-natural fir–beech stands, which arose according to the model taking into account the overlapping of fir mortality and beech regeneration, were generally conformed to the Birnbaum–Saunders distribution. In such forests, the Birnbaum–Saunders distribution approximated the empirical DBH distributions more precisely than the Weibull and gamma distributions.
Growth and physiology of loblolly pine in response to long-term resource management: defining growth potential in the southern United States
Authors: Samuelson Lisa J. , Butnor John , Maier Chris , Stokes Tom A. , Johnsen Kurt , Kane Michael 
Published: April 2008

Leaf physiology and stem growth were assessed in loblolly pine ( Pinus taeda L.) in response to 10 to 11 years of treatment with weed control (W), weed control plus irrigation (WI), weed control plus irrigation and fertigation (WIF), or weed control plus irrigation, fertigation, and pest control (WIFP) to determine whether increased resource availability can push productivity of loblolly pine closer to its biological growth potential expressed in favorable, exotic environments. Maximum basal area and stem biomass were 41 m2·ha–1 and 172 Mg·ha–1, respectively, in response to fertigation. Stemwood biomass production was positively and linearly related to basal area. Belowground woody biomass was highest in the WIF and WIFP treatments and averaged 50 Mg·ha–1, but the W and WI treatments exploited a greater area of soil with low-density coarse roots. Fertigation increased foliar nitrogen concentration and foliage biomass, but treatment had no effect on leaf physiological parameters or growth efficiency. Comparison with growth rates reported for loblolly pine in Hawaii revealed that loblolly pine grown in its native range can produce the high yields observed in exotic environments when stands are below maximum carrying capacity.
Effects of forest floor organic layer and root biomass on soil respiration following boreal forest fire
Authors: Singh S. , Amiro B. D. , Quideau S. A. 
Published: April 2008

Soil respiration and its spatial and temporal variation were studied at three boreal forest sites in central Saskatchewan, Canada, burned in 1998, 1989, and 1977. Soil respiration, soil temperature, and organic layer thickness were measured at 100 points in a grid pattern of 2 m × 2 m at each site in 2004 and 2005. The mean within-site spatial coefficient of variation was 35%, and the measurements were not spatially autocorrelated. We found no significant difference in variance between the two youngest sites (P > 0.05), whereas the older site showed significantly lower variance (P < 0.05). Soil respiration was not correlated with the forest floor organic layer thickness at any of the sites (R2 < 0.1). Removal of the forest floor layer reduced the soil respiration by 17% to 38%, depending on the site. Thus, the respiration from the mineral soil seemed to contribute a major fraction of the total soil respiration (62%–83%). Soil respiration was positively linearly related to the fine root biomass (R2 = 0.63–0.85, P < 0.05) at all sites. We conclude that variation in root biomass has a larger effect than differential forest floor organic layers on variation in soil respiration in young boreal postfire forests.
Reproductive output of ponderosa pine in response to thinning and prescribed burning in western Montana
Authors: Peters Gregory , Sala Anna 
Published: April 2008

Thinning and thinning followed by prescribed fire are common management practices intended to restore historic conditions in low-elevation ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws.) forests of the northern Rocky Mountains. While these treatments generally ameliorate the physiology and growth of residual trees, treatment-specific effects on reproductive output are not known. We examined reproductive output of second-growth ponderosa pine in western Montana 9 years after the application of four treatments: thinning, thinning followed by spring prescribed fire, thinning followed by fall prescribed fire, and unthinned control stands. Field and greenhouse observations indicated that reproductive traits vary depending on the specific management treatment. Cone production was significantly higher in trees from all actively managed stands relative to control trees. Trees subjected to prescribed fire produced cones with higher numbers of filled seeds than trees in unburned treatments. Seed mass, percentage germination, and seedling biomass were significantly lower for seeds from trees in spring burn treatments relative to all others and were generally higher in trees from fall burn treatments. We show for the first time that thinning and prescribed-burning treatments can influence reproductive output in ponderosa pine.
Effects of stem anatomical and structural traits on responses to stem damage: an experimental study in the Bolivian Amazon
Authors: Romero Claudia , Bolker Benjamin M. 
Published: April 2008

Persistence of tree species in a habitat depends on their ability to avoid and respond to disturbance-related damage. Responses to stem damage vary among species but typically include bark wound closure and prevention of xylem decay spread. These responses are associated with anatomical, structural, and physiological traits. This study explores how xylem (vessel size and (or) abundance, parenchyma abundance, ray width, and wood density) and phloem (bark thickness, proportion of live inner bark, ray width and (or) dilation, inter-ray distance, and tissue density) traits relate to responses to stem damage in seven species from the Bolivian Amazon. Rates of bark wound closure and radial xylem decay penetration were compared 2 years after experimental damage. A species that closed bark wounds rapidly (100% in Chorisia speciosa A. St.-Hil.) was not efficient at constraining xylem radial decay spread (1.7 mm). The opposite was true for Pseudolmedia laevis (Ruiz & Pav.) J.F. Macbr., a species that closed wounds slowly (30%) but efficiently controlled decay spread (0.5 mm). The relationship between anatomical and (or) structural traits and damage response variables revealed that species with favorable traits for rapid wound closure (e.g., widely dilating rays) had traits that favored xylem decay spread (e.g., low wood density). It is plausible that this apparent trade-off is based on physiological and phylogenetic constraints.
Assessing prediction errors of generalized tree biomass and volume equations for the boreal forest region of west-central Canada
Authors: Case Bradley S. , Hall Ronald J. 
Published: April 2008

Aboveground tree biomass and volume are required inputs to models that estimate carbon budgets and ecosystem productivity. Generalized equations are often used to estimate biomass and volume when local equations are unavailable. This study determined whether there was a concomitant increase in prediction error from increasing levels of equation generalization. Local site, generalized regional, and generalized national allometric equations were compared for 10 species distributed across 119 sites in a region defined by west-central Canada. This study employed regression fit statistics and two prediction error metrics, the average prediction error (APE) from the prediction error sum of squares (PRESS) statistic and mean prediction bias. The APE was 9, 12, and 25 kg of biomass per tree for local site, generalized regional, and national equations, respectively. The mean prediction bias for biomass and volume were statistically similar between local level and generalized regional equations across all species. Predictions from generalized national equations were statistically similar for 5 of 10 species when compared with those from local site and generalized regional equations. While local site equations were most accurate for a given site, results indicate that generalized regional equations will produce reasonable estimates of biomass and volume at sites in this region of Canada.