bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of flowering phenology and seed yield in a Pinussylvestris clonal seed orchard in Nebraska
Authors: Boes Teresa K. , Brandle James R. , Lovett William R.
Published: July 2007

Forty-two Eurasian Scots pine (Pinussylvestris L.) clones in a Nebraska seed orchard were observed over 3 years for the phenology of pollen release and seed-cone receptivity and for the production of cones and filled seed. A preliminary investigation had indicated that seed yields were less than expected, and nonsynchronous flowering phenology due to wide genetic diversity was considered as a possible cause. The clones were divided into six regions based on geographic origin and analyzed for variation between regions and between clones within regions. Most variation in cones per tree and filled seeds per cone was due to differences between clones. Most variation in weight per seed was due to differences between regions. The order in which clones began releasing pollen and became receptive remained the same from year to year, but the duration of these events differed between years. Results indicated that nonsynchronous flowering phenology due to genetic diversity is not a likely cause of low seed yield. Seed crops (19.3 kg/ha, 97 000 seeds/kg) were not necessarily lower than should be expected, but 90% of a given year's crop was produced by an average of only 26 clones. With the paternal contribution of each clone to the seed crop unknown, collecting and sowing seed separately by clone is recommended.
Response of leaf area index to density for two contrasting tree species
Authors: Jack Steven B. , Long James N.
Published: July 2007

It is commonly assumed that mature forest stands with closed canopies support constant amounts (weight or area) of foliage, independent of stand density. For stand leaf area to be constant, mean leaf area must be plastic with respect to density. We examined the relationship between density and both leaf area index and mean leaf area for two contrasting tree species, lodgepole pine (Pinuscontorta var. latifolia Engelm.) and subalpine fir (Abieslasiocarpa (Hook.) Nutt.). In lodgepole pine, leaf area index tended to be constant over a wide range of absolute and relative densities, but in subalpine fir, leaf area index increased with density. Consistent with these results, mean leaf area of lodgepole pine was more plastic with respect to density than mean leaf area of subalpine fir. The presumption of stable leaf area index independent of stand density, therefore, may not be as general as usually assumed owing to differential responses of mean leaf area to density. Differences in plasticity between the two species were attributed to differences in relative shade tolerance and the effect of shade on competitive interactions at high densities.
The use of nutrient bioassays to assess the response of Eucalyptusgrandis to fertilizer application. 2. A field experiment
Authors: Jones Helen E. , Dighton John
Published: July 2007

The nutrient status of a Eucalyptusgrandis Hill ex Maiden field fertilizer experiment in Natal, South Africa, was assessed at 6 and 18 months by a bioassay test in which the rate of influx of 15N, 32P, and 86Rb in roots excised from trees was measured. Fertilizer treatments consisted of all combinations of two levels of nitrogen (N), phosphorus (P), potassium (K), and trace elements, applied at planting and at either 3 or 6 months. There were also untreated control plots. At 6 months, bioassay influx rates of the three isotopes by the roots were all higher when a nutrient was applied at a lower level than when it was applied at a higher level. Foliar analysis did not indicate that any of the trees were deficient in N, P, or K, although control plants were significantly smaller than fertilized ones. There was no difference in the foliar P or K content between the treatments, although percent N increased with increasing application of N. The greatest difference in the root response between fertilizer levels was in the influx of 15N. Height of the trees was significantly increased by increasing N levels. There was no effect of P or K levels, but there was a negative effect of the combination of high levels of K and trace elements. From the significant drop in root 15N influx following the 6 month fertilizer addition, growth of the trees in response to fertilizer was predicted. At 18 months of age trees receiving their second application of fertilizer at 6 months were as large as those receiving fertilizer at 3 months, confirming growth predictions based on root bioassay data. The bioassay results at 18 months suggested that P may be supplanting N as the major growth limiting factor at this later stage in the development of the stand.
Peatland and upland black spruce populations in Alberta: morphology and ecophysiology
Authors: Wang Zhang M. , Macdonald S. Ellen
Published: July 2007

Morphology and ecophysiology of black spruce (Piceamariana (Mill.) B.S.P.) seedlings grown in a variety of controlled environments were studied in three pairs of adjacent peatland and upland black spruce populations from Alberta. Seedlings were grown in two greenhouse experiments as follows: (i) full factorial combinations of light (100 or 20% of full light in the greenhouse) and moisture (wet, medium, or dry); (ii) full factorial combinations of fertilization (fertilized or unfertilized) and substrate temperature (20 or 8 °C at 5 cm below the surface). In both experiments, morphological (height, top dry weight, root dry weight, total dry weight, and top/root dry weight ratio) and physiological (net assimilation (NA), stomatal and mesophyll conductance to CO2 (gc and gm), and water use efficiency (WUE)) traits were measured. It was found that low light, nutrient stress, and water stress (wet or dry) reduced seedling growth. As moisture decreased or at low light, NA, gc, gm, and WUE decreased. When fertilized, seedlings at low substrate temperature were smaller and had lower NA, gc, and gm than those at high substrate temperature. Results showed no differences in response to the experimental environments between seedlings from peatland versus upland populations. However, upland seedlings were larger than peatland ones, there was greater variation among peatland than among upland populations, and there were site-specific habitat differences. Overall, there was apparently little adaptive ecotypic differentiation in black spruce between the two habitats.
Feeding damage by bears in managed forests of western hemlock–western red cedar in midcoastal British Columbia
Authors: Sullivan Thomas P.
Published: July 2007

This study measured the incidence of feeding damage in 1989 and 1990 by black bears (Ursusamericanus Pallas), and possibly by grizzly bears (Ursusarctos L.), within managed and unmanaged second-growth western hemlock (Tsugaheterophylla (Raf.) Sarg.)–western red cedar (Thujaplicata Donn) forest stands near Jennis Bay, 39 km northwest of Port Hardy, British Columbia. Tree mensuration (1989) and damage assessments (1989 and 1990) were conducted in 69 sample plots located in stands that were spaced in 1980 to 1982, when the trees were juvenile, and in 19 plots located in a nearby unspaced (control) stand. Western red cedar, which represented 13.6% of the managed stands, was the most severely damaged species (cumulative attack of 63.8% in 1989, increasing to 69.1% in 1990). Western hemlock, the major tree species, had <0.5% of trees attacked, and amabilis fir (Abiesamabilis (Dougl.) Forbes) was not attacked. Cumulative incidence of damage to red cedar in the control stand was 66.7% in 1989, increasing to 71.4% in 1990. The annual incidence of attack in 1990 was 18.1% in the spaced stands and 16.7% in the control stand. The total percentage of girdled cedar stems (mortality) was 10.7% in the control and 23.3% in the spaced stands overall. Bear damage clearly declined during 1990, which may be related to dispersal or removal (hunting) of animals from the general area or to a declining number of cedar trees (30%) that remain unattacked by bears. Crop tree selection against red cedar in future spacing projects could alleviate bear attacks.
Variation in virulence among single-aeciospore isolates from single-gall isolates of Cronartiumquercuum f.sp. fusiforme
Authors: Kuhlman E.G. , Matthews F.R.
Published: July 2007

Single aeciospores from single-gall isolates of Cronartiumquercuum (Berk.) Miyabe ex Shirai f.sp. fusiforme previously shown to have virulence toward resistant half-sib loblolly pine (Pinustaeda L.) families 10-5, 11-20, or 29R were propagated in the asexual uredial stage on leaves of oak seedlings. Only 80 of 1086 single aeciospores from a single-gall isolate with virulence towards family 10-5 produced symptoms of infection on the oaks, and 17 infections produced telia directly. Thirty-two single-aeciospore isolates were propagated from the 63 uredinia. Half-sib progeny of 10-5 were inoculated with each of the 32 isolates, and after 9 months incidence of seedlings with galls varied from 46 to 93%. Six isolates produced galls on more than 90% of the seedlings. Average gall length ranged from 30 to 56 mm among the 32 isolate treatments. Similarly, 20 single-aeciospore isolates propagated from two single-gall isolates with virulence towards family 11-20 caused galls on 19–59% of 11-20 progeny. Finally, 12 single-aeciospore isolates propagated from a single-gall isolate with virulence towards family 29R produced galls on 38–91% of the half-sib progeny of 29R. Thus, in three separate experiments virulence among single-aeciospore isolates toward a resistant source ranged from normal to very high.
Genetic variation and productivity of Populustrichocarpa and its hybrids. VI. Field susceptibility of seedlings to Melampsoraoccidentalis leaf rust
Authors: Hsiang T. , Chastagner G. A , Dunlap J. M. , Stettler R. F.
Published: July 2007

A 3-year study on the incidence and severity of leaf rust caused by Melampsoraoccidentalis on hybrid poplars began in 1987 when inter- and intra-specific crosses were made with 20 Populustrichocarpa (T), 8 Populusmaximowiczii (M), and 3 Populustrichocarpa × Populusdeltoides (TD) parents. A total of 5100 seedlings from 67 families were initially surveyed for rust in 1988; however, this number declined to less than 3700 by 1990, and rust infection likely contributed to seedling mortality. There was significantly greater rust incidence and severity in T × T crosses than in T × M, M × TD, TD × M, or M × M crosses. For the 12 M × M crosses and the 6 three-way crosses (M × TD, TD × M), less than 1% of the seedlings had any rust in the 3 years. In the 20 T × M crosses, over 65% of the seedlings showed no rust and less than 1% showed heavy rust. For T × T seedlings from 29 crosses, less than 3% had no rust. Reciprocal crosses of P. trichocarpa from east or west of the Cascade Mountains in Washington showed that the female parent contributed more to rust susceptibility than the male parent. In regression analyses, P. trichocarpa midparent rust ratings were negatively correlated with family survival and positively correlated with the mean progeny rust rating. Narrow-sense family heritabilities were moderate to high for rust susceptibility (h2 = 0.43 in 1988, 0.53 in 1989, and 0.79 in 1990).
Tree population dynamics, growth, and mortality in old-growth forests in the western Olympic Mountains, Washington
Authors: Edmonds Robert L. , Thomas Ted B. , Maybury Kathleen P.
Published: July 2007

Tree population dynamics, growth, and mortality were determined in old-growth forested watersheds in the Hoh River valley, Olympic Peninsula, Washington: West Twin Creek (elevation 180–850 m) and Hoh Lake (elevation 1250–1525 m). Principal tree species at West Twin Creek are Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg.), Pacific silver fir (Abiesamabilis (Dougl.) Forb.), western red cedar (Thujaplicata D. Don), and Sitka spruce (Piceasitchensis (Bong.) Carr.). At Hoh Lake they are Pacific silver fir, mountain hemlock (Tsugamertensiana (Bong.) Carr.), and Alaska cedar (Chamaecyparisnootkatensis (D. Don) Spach). In 1985 stem densities for trees >5 cm DBH averaged 476 and 489 ha−1 in the upper and lower West Twin Creek watershed, respectively, and 508 ha−1 at Hoh Lake watershed. Stem densities at both sites declined 3–5% from 1985 to 1990. Western hemlock and Pacific silver fir were the dominant species at West Twin Creek and Hoh Lake, respectively. From 1985 to 1990 the annual mortality rate was 0.8% at West Twin Creek and 0.9% at Hoh Lake. Pacific silver fir had the highest mortality rate. No Douglas-fir or western red cedar trees died. The primary causes of mortality were as follows: suppression–unknown, diseases, insects, and windthrow. In 1985 basal areas were 77, 87, and 94 m2•ha−1 in the lower and upper West Twin Creek watershed and Hoh Lake watershed, respectively. There was a 5% increase and a 1% decrease in basal area from 1985 to 1990 in the lower and upper West Twin Creek watershed, respectively, and a 4% decrease at Hoh Lake. Western red cedar, Douglas-fir, and western hemlock increased in basal area, while the other species declined.
Effects of variations in stand structure on development of mixed-species stands in eastern Washington
Authors: Cobb David F. , O'hara Kevin L. , Oliver Chadwick D.
Published: July 2007

The development of six mixed-species, even-aged stands was reconstructed in the eastern Washington Cascade Range. All stands were within the Grand Fir Climax Series and began following stand replacement disturbances. Western larch (Larixoccidentalis Nutt.) and lodgepole pine (Pinuscontorta Dougl. ex Loud.), when present, formed an upper stratum over interior Douglas-fir (Pseudotsugamenziesii var. glauca (Beissn.) Franco) and grand fir (Abiesgrandis (Dougl.) Lindl.) in all six stands. Establishment patterns and species composition affected stand development patterns. Douglas-fir benefitted from the absence of lodgepole pine; grand fir benefitted from the absence of Douglas-fir, but apparently not from the absence of lodgepole pine. Lodgepole pine had faster initial diameter growth rates than western larch when it became established relatively early and in large numbers.
A test of alternative estimators for volume at time 1 from remeasured point samples
Authors: Roesch Jr. Francis A. , Green Edwin J. , Scott Charles T.
Published: July 2007

Two estimators for volume at time 1 for use with permanent horizontal point samples are evaluated. One estimator, used traditionally, uses only the trees sampled at time 1, while the second estimator, originally presented by Roesch and coauthors (F.A. Roesch, Jr., E.J. Green, and C.T. Scott. 1989. For. Sci. 35(2): 281–293), takes advantage of additional sample information that becomes available at time 2. In this test the Roesch etal. estimator was always lower in sum of squared differences and sum of absolute differences for board foot and cubic foot volume than the traditional estimator. In addition a simulation revealed no discernible bias for the Roesch etal. estimator over the traditional estimator.
Changes in tissue nitrogen and phosphorus and foliar free amino acids in autumn olive, black locust, American sycamore, and honey locust during autumn
Authors: Vogel Christoph S. , Dawson Jeffrey O.
Published: July 2007

Changes in tissue nitrogen, phosphorus, and foliar free amino acids of four temperate woody deciduous plants (autumn olive (Elaeagnusumbellata Thunb.), black locust (Robiniapseudoacacia L.), American sycamore (Platanusoccidentalis L.), and honey locust (Gleditsiatriacanthos L.)) were determined during the autumns of 1987 and 1988 on two physically and nutritionally distinct sites in central Illinois, United States. The dinitrogen-fixing species, actinorhizal autumn olive (Frankia nodulated) and leguminous black locust (Rhizobium nodulated), resorbed a greater proportion of phosphorus than nitrogen from leaves prior to autumnal leaf abscission in comparison with the nonfixing American sycamore and honey locust. The net autumnal changes in nitrogen or phosphorus of each species did not differ with site in most cases. Free amino acid contents of leaves tended to decline as leaves senesced during the drier autumn of 1987; however, during the autumn of 1988 foliar free amino acid contents tended to increase as the season progressed, with abscised leaves having the greatest contents. Root bark seemed to be a major sink for phosphorus during autumn in the dinitrogen-fixing species, while all of the species investigated showed significant autumnal increases in twig-bark concentrations of nitrogen.
Forest fires in Russia: carbon dioxide emissions to the atmosphere
Authors: Dixon Robert K. , Krankina Olga N.
Published: July 2007

Boreal forests of Russia play a prominent role in the global carbon cycle and the flux of greenhouse gases to the atmosphere. Large areas of Russian forest burn annually, and contributions to the net flux of carbon to the atmosphere may be significant. Forest fire emissions were calculated for the years 1971–1991 using fire frequency and distribution data and fuel and carbon density for different forest ecoregions of Russia. Both direct carbon release and indirect post-fire biogenic carbon flux were estimated. From 1971 to 1991 the annual total forest area burned by wildfire ranged from 1.41 × 106 to 10.0 × 106 ha. Approximately 15 000–25 000 forest fires occurred annually during this period. Mean annual direct CO2-C emissions from wildfire was approximately 0.05 Pg over this 21-year period. Total post-fire biogenic CO2-C emissions for 1971–1991 ranged from 2.5 to 5.9 Pg (0.12–0.28 Pg annually). Forest fires and other disturbances are expected to be a primary mechanism driving vegetation change associated with projected global climate change. Future forest fire scenarios in Russia based on general circulation model projections suggest that up to 30–50% of the land surface area, or 334 × 106 to 631 × 106 ha of forest, will be affected. An additional 6.7 × 106 to 12.6 × 106 ha of Russian boreal forest are projected to burn annually if general circulation model based vegetation-change scenarios are achieved within the next 50 years. The direct flux of CO2-C from future forest fires is estimated to total 6.1–10.7 Pg over a 50-year period. Indirect post-fire biogenic release of greenhouse gases in the future is expected to be two to six times greater than direct emissions. Forest management and fire-control activities may help reduce wildfire severity and mitigate the associated pulse of greenhouse gases into the atmosphere.
The influence of mountain alder on the growth, nutrition, and survival of black spruce and Sitka spruce in an afforested heathland near Mobile, Newfoundland
Authors: Hudson André J.
Published: July 2007

The natural invasion of mountain alder (Alnuscrispa (Ait.) Pursh) into monoculture plantations of black spruce (Piceamariana (Mill.) B.S.P.) and Sitka spruce (Piceasitchensis (Bong.) Carr.) afforded an opportunity to assess the effects of mountain alder on soils, and on the growth, nutrient status, and survival of spruce in eastern Newfoundland. The plantations were established on ploughed Kalmia–Vaccinium heath in 1968–1969. Significant increases in the growth of spruce were associated with the presence of high densities of mountain alder in the two plantations studied. The increases began 3–6 years after the invasion and establishment of mountain alder. Estimated nitrogen (N) contributions to each plantation from mountain alder leaf litter fall were approximately 50 kg•ha−1•year−1. Spruce foliage N content was 10–15% higher in high-density mountain alder (HD-alder) plots than in low-density mountain alder (LD-alder) plots, but other foliar nutrient concentrations were low and possibly deficient in the HD-alder plots. Development of a litter fall–humus layer was observed in HD-alder plots but not in LD-alder plots; however, B-horizon soil-N values did not differ significantly between HD-alder and LD-alder plots. The mountain alder invasion did not reduce the densities (stems/ha) of spruce. Additional studies on the autecology of Alnus spp. native to Newfoundland, and on alder-spruce interaction are recommended to further the development of an adequate ecological basis for heathland and peatland afforestation in the region.
Seed-source variation in water relations, gas exchange, and needle morphology of mature ponderosa pine trees
Authors: Cregg Bert M.
Published: July 2007

Xylem pressure potential (ψx), net photosynthesis (A), needle conductance (gn), and transpiration (E) were measured periodically throughout the 1991 growing season on 16 ponderosa pine (Pinusponderosa Dougl. ex Laws.) trees growing in a 23-year-old provenance planting in eastern Nebraska. The trees studied were from four diverse sources: western Montana, northwest South Dakota, southern New Mexico, and central Arizona. In addition to water relations and gas exchange, specific leaf area, stomatal density, and surface to volume ratios were determined on 1-year-old foliage of each tree. Compared with the other seed sources, gas exchange of the South Dakota source was lowest early in the summer, when ψx was generally high, and highest in the late summer, when ψx declined. However, the relation of gn to ψx did not appear to differ among the seed sources. The South Dakota source had lower stomatal density and needle length than the other sources tested. No differences in specific leaf area or surface to volume ratio were observed. Overall, variation in physiology and needle morphology among seed sources of mature ponderosa pine appears to be more subtle than intraspecific variation of seedlings of other species reported in the literature.
Statistical inference problems related to the logarithmic transformation in regression; another method for interval estimation
Authors: Végiard Sylvain , Ung Chhun-Huor
Published: July 2007

This note complements an article published by the authors in 1988 in this journal. Another method is given for constructing confidence intervals in regression using the logarithmic transformation. The procedure is easy to use and is appropriate for most situations.
Control of surface soil chemistry in early-successional floodplain soils along the Tanana River, interior Alaska
Authors: Dyrness C.T. , Cleve K. Van
Published: July 2007

Surface soils on recently deposited alluvium along the Tanana River, Alaska, have an elevated pH and are high in salts such as calcium carbonate and calcium sulfate. With advancing plant succession surface soil chemistry changes, and when the alder–balsam poplar stage is reached these salt deposits are absent. To test the hypothesis that soil surface salt (salt crust) accumulates as a result of the combined action of capillary rise of groundwater and surface evaporation, a treated plot experiment was undertaken in the early open willow stage on the floodplain where the soil surface was devoid of litter. Treatments, applied in early summer, were salt crust removed, leaf litter added on the surface (evaporation barrier), and polyethylene sheeting installed at a depth of 30 cm (capillary rise barrier). Surface 5 cm soil samples, collected in September, showed significant reductions from salt crust removal and surface litter application in electrical conductance and amounts of bicarbonate, sulfate, calcium, magnesium, potassium, and sodium. In clearings within dense alder–balsam poplar stands on the first terrace, forest floor removal resulted in significantly increased amounts of surface soil sodium, sulfate, calcium, and magnesium. However, this treatment did not result in re-establishment of the salt crust, probably because of a higher ground surface elevation at this terrace and consequent deeper water table. On lower, early-successional terraces salt crusts may form in a period of only several weeks if precipitation is low. The advent of a complete litter layer has great significance in the successional sequence on these soils not only because of nutrient cycling as a result of decomposition processes but also because of the probable physical effect of severely decreasing rates of evaporation from the mineral soil surface. In the latter case, although we did not directly measure mineral soil surface evaporation rates with and without litter layers, movement of salt solution injected at 25 cm in the soil profile to the surface was restricted by application of a surface litter layer.
Mass and nutrient content of woody debris and forest floor in western red cedar and western hemlock forests on northern Vancouver Island
Authors: Keenan Rodney J. , Prescott Cindy E. , Kimmins J.P. Hamish
Published: July 2007

Biomass and C, N, P, and K contents of woody debris and the forest floor were surveyed in adjacent stands of old-growth western red cedar (Thujaplicata Donn)–western hemlock (Tsugaheterophylla (Raf.) Sarg.) (CH type), and 85-year-old, windstorm-derived, second-growth western hemlock–amabilis fir (Abiesamabilis (Dougl.) Forbes) (HA type) at three sites on northern Vancouver Island. Carbon concentrations were relatively constant across all detrital categories (mean = 556.8 mg/g); concentrations of N and P generally increased, and K generally decreased, with increasing degree of decomposition. The mean mass of woody debris was 363 Mg/ha in the CH and 226 Mg/ha in the HA type. The mean forest floor mass was 280 Mg/ha in the CH and 211 Mg/ha in the HA stands. Approximately 60% of the forest floor mass in each forest type was decaying wood. Dead woody material above and within the forest floor represented a significant store of biomass and nutrients in both forest types, containing 82% of the aboveground detrital biomass, 51–59% of the N, and 58–61% of the detrital P. Forest floors in the CH and HA types contained similar total quantities of N, suggesting that the lower N availability in CH forests is not caused by greater immobilization in detritus. The large accumulation of forest floor and woody debris in this region is attributed to slow decomposition in the cool, wet climate, high rates of detrital input following windstorms, and the large size and decay resistance of western red cedar boles.
A decision support system that links short-term silvicultural operating plans with long-term forest-level strategic plans
Authors: Davis Robert G. , Martell David L.
Published: July 2007

This paper describes a decision support system that forest managers can use to help evaluate short-term, site-specific silvicultural operating plans in terms of their potential impact on long-term, forest-level strategic objectives. The system is based upon strategic and tactical forest-level silvicultural planning models that are linked with each other and with a geographical information system. Managers can first use the strategic mathematical programming model to develop broad silvicultural strategies based on aggregate timber strata. These strategies help them to subjectively delineate specific candidate sites that might be treated during the first 10 years of a much longer planning horizon using a geographical information system and to describe potential silvicultural prescriptions for each candidate site. The tactical model identifies an annual silvicultural schedule for these candidate sites in the first 10 years, and a harvesting and regeneration schedule by 10-year periods for aggregate timber strata for the remainder of the planning horizon, that will maximize the sustainable yield of one or more timber species in the whole forest, given the candidate sites and treatments specified by the managers. The system is demonstrated on a 90 000 - ha area in northeastern Ontario.
Water transfer in a mature oak stand (Quercuspetraea): seasonal evolution and effects of a severe drought
Authors: Bréda N. , Cochard H. , Dreyer E. , Granier A.
Published: July 2007

The reactions of sessile oak (Quercuspetraea (Mattuschka) Liebl.) to drought were studied under natural conditions in a 32-year-old stand near Nancy (northeastern France) during the summers of 1989 (strongly rain deficient) and 1990. A plot of five trees was subjected to imposed water shortage, while a group of irrigated trees was used as a control. Measurements of xylem sap flows and water potential enabled the computation of plot transpiration, canopy conductance, and specific hydraulic conductance in the soil–tree continuum. Stomatal conductance was measured directly with a porometer. Specific hydraulic conductance of our oaks was of the same order of magnitude as that reported for other species. It decreased significantly during spring because of a time lag between cambial growth and leaf area expansion. Measured transpiration was close to potential evapotranspiration, except during days with high vapor pressure deficits, which promoted stomatal closure in the absence of soil water deficits. Imposed drought caused predawn leaf water potentials to reach values as low as −2.0 MPa and a progressive decline in hydraulic conductance, which was probably attributable to modifications in hydraulic properties at the soil–root interface. This gradual decline in conductance was attributed to their deep rooting (1.40 m). This study revealed that Q. petraea may be considered as drought tolerant because of adaptations like deep rooting, efficient and safe xylem sap transport, maintenance of significant stomatal conductance, and significant transpiration, even during strong drought stress.
Photosynthesis and dark respiration of black spruce cuttings during rooting in response to light and temperature
Authors: Yue De , Margolis Hank A.
Published: July 2007

Photosynthesis and dark respiration of semihardened black spruce cuttings (Piceamariana (Mill.) B.S.P.) were periodically measured at a range of light intensities at 10, 15, 20, 25, and 30 °C over an 8-week period in rooting chambers and for 4 additional weeks after the cuttings were transferred to a greenhouse. Increases in the total dry weight of the cuttings over the experimental period were due exclusively to increases in root biomass. The light-saturated photosynthetic rates at 20 °C decreased from 3.8 to 2.2 μmol CO2•m−2•s−1 during the 8 weeks in the rooting chamber. At 15 °C, the light-saturated photosynthetic rate was about 2 μmol CO2•m−2•s−1 and no significant change was observed during the experimental period. Maximum photosynthetic rates were generally attained at photosynthetic photon flux densities (PPFD) of 200–300 μmol•m−2•s−1 At the range of PPFD generally used in rooting chambers (0–50 μmol•m−2•s−1), the light use efficiency of cuttings (net photosynthesis per cutting per PPFD) was greatest at 15 °C. Furthermore, the light compensation point was lowest at 15 °C. The effect of light intensity and temperature on the photosynthesis and dark respiration of cuttings was modelled to predict the carbon balance of cuttings under different conditions of PPFD and temperature. This model should be useful in determining an appropriate set of environmental conditions to use inside rooting chambers and thus improve the overall physiological quality of this type of vegetatively propagated planting stock. The modelling approach described in this study could prove useful for the production of other conifer species by rooted cuttings even when it is conducted using other methods of cultivation (e.g., cold-frames or greenhouses).
Aboveground biomass production and nutrient accumulation on postharvested white spruce sites in interior Alaska
Authors: Paré David , Cleve Keith Van
Published: July 2007

Nutrient content and biomass of aboveground annual production, and nutrient content of total aboveground biomass, of 14-year-old assemblages of plants developing on harvested white spruce (Piceaglauca (Moench) Voss) sites were estimated by vegetation harvesting and compared with values previously measured in mature white spruce stands. The aboveground biomass production of 14-year-old regenerating trembling aspen (Populustremuloides Michx.) clumps was 3 times higher than the aboveground production of mature white spruce stands, while the aboveground production of other regenerating communities was lower or equivalent to the production of mature white spruce. However, the nutrient content of aboveground current biomass was greater in all regenerating communities than in mature white spruce stands, except on regenerating sites where the forest floor was absent. The amount of nutrient incorporated in current aboveground biomass was 5 times greater in trembling aspen clumps than in mature white spruce stands. Furthermore, the total N, P, and K content of aboveground vegetation corresponded, in 14-year-old trembling aspen clumps, to a value that ranged from 50 to 109% of the amount found in the aboveground biomass of mature white spruce forests, while this value ranged from 4 to 14% on other regeneration types. Trembling aspen and balsam poplar (Populusbalsamifera L.) both showed the greatest concentrations of N and P in foliar litter fall. These observations suggest that the development of a trembling aspen clump after clear-cutting contributes to the acceleration of nutrient cycling. On the other hand, the development of herbaceous communities during the same period after clear-cutting was accompanied by much lower nutrient cycling rates in the aboveground portion of the vegetation.
Regional genetic variation in turkey oak, Quercuslaevis
Authors: Berg Edward E. , Hamrick J.L.
Published: July 2007

Quercuslaevis Walt, (turkey oak) is a dominant hardwood tree in the sandhills communities of the coastal plain of the southeastern United States. Estimates of allozyme diversity for this species were typical of oaks (Hes = 0.184) and diversity within eleven sandhills populations was also relatively high (Hep = 0.178). Genetic diversity among populations was low (GST = 0.032), being about one third of the mean for other oak species. We interpret the interpopulation homogeneity as a relict of a previously more continuous distribution of longleaf pine (Pinus palustris Mill.)–turkey oak forest that constituted the dominant vegetation of the coastal plain prior to European settlement. Pollen-mediated gene flow among populations may be enhanced through acorn dispersal by blue jays (Cyanocittacristata L.).
Effect of ozone and aluminum on pitch pine (Pinusrigida) seedlings: needle ultrastructure
Authors: McQuattie Carolyn J. , Schier George A.
Published: July 2007

Newly germinated pitch pine (Pinusrigida Mill.) seedlings inoculated with a mycorrhizal fungus (Pisolithustinctorius (Pers.) Coker & Couch) were grown for 13 weeks in sand irrigated with nutrient solution (pH 4.0) containing 0, 12.5, 25, or 50 mg/L aluminum in growth chambers fumigated with 0, 50, 100, or 200 ppb ozone. Cytological changes in needles of seedlings stressed by ozone and aluminum, singly and in combination, were determined by light and electron microscopy. The most pronounced changes in needles exposed to ozone occurred in the outer mesophyll, whereas major changes in the presence of aluminum occurred in the stele and inner mesophyll. At lower levels of either ozone or aluminum, the cytoplasm became more densely stained. Accumulation of dense materials appeared at intermediate treatment concentrations, and at high concentration localized cell collapse and deterioration became evident. Ozone or aluminum caused similar changes in the chloroplasts, for example, increase in number of plastoglobuli, accumulation of starch, formation of electron-dense stroma, and swelling or disruption of thylakoid membrane system. Ozone and aluminum in combination generally caused histological and cytological damage in needles to occur at lower concentrations than either aluminum or ozone alone.
Spatial and temporal variation in the prevalence of growth decline in red spruce populations of the northeastern United States: Discussion
Authors: Reams Gregory A. , Deusen Paul C. Van , Cook Edward R.
Published: July 2007

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Chronology of spruce budworm outbreaks near Lake Duparquet, Abitibi region, Quebec
Authors: Morin Hubert , Laprise Danielle , Bergeron Yves
Published: July 2007

The chronology of eastern spruce budworm (Choristoneurafumiferana (Clem.)) outbreaks in the vicinity of Lake Duparquet in the Abitibi region, Quebec, was determined for a period of 200 years using dendroecological methods. Growth patterns of two budworm host species, balsam fir (Abiesbalsamea (L.) Mill.) and white spruce (Piceaglauca (Moench) Voss), were compared with white cedar (Thujaoccidentalis L.), a nonhost species, and with maps of defoliation surveys. The method permitted precise dating of past outbreaks prior to the last two decades, where cartographic information is either imprecise or nonexistent. Growth reductions associated with insect defoliation situate three outbreak periods in this century between 1970 and 1987, between 1930 and 1950, and between 1919 and 1929. A fourth outbreak period may have occurred in the 19th century between 1810 and 1832. The outbreaks in this region were less severe than those that have occurred further south of the insect's northern limit of dispersion. Nevertheless, they did have a major impact on the dynamics of balsam fir populations in the region, as revealed by a massive invasion of fir between 1915 and 1940, and a marked growth release between 1940 and 1950. Dry periods, reflected in the growth curve of cedar, were associated with recorded outbreak periods.
The effect of site quality on the timing of stand breakup, tree longevity, and the maximum attainable height of black spruce
Authors: Robichaud Edgar , Methven Ian R.
Published: July 2007

The relationship between site quality and tree and stand longevity is examined to test the hypothesis that a reduction in resource availability results in an increase in longevity. A total of 54 black spruce (Piceamariana (Mill.) B.S.P.) stands in New Brunswick and Quebec were sampled. Within each stand the stage of development was established and tree ages, years of suppression, heights, and site indices were determined. Within stands found to be at or near breakup, tree age was found to be linearly and negatively related to site index (r2 = 0.39; p = 0.0001). The addition of suppression to the regression model improved the predictive ability of the model (r2 = 0.48) and indicated that 1 year of suppression increased tree longevity by 0.74 year. Examination of the height–age curves of the trees indicated that maximum heights do not vary with site quality. The correlation between the maximum height of trees (live or dead) within stands at breakup and site index was not significant at the p = 0.05 level (r = 0.15), further supporting this observation. The results support the hypothesis that longevity increases with a decrease in growth rate due to resource limitations. The explanation for this pattern lies in the height–growth rate and maximum attainable height of trees growing under various site conditions.
The economics of Douglas-fir and red alder management with stochastic price trends
Authors: Haight Robert G.
Published: July 2007

A financial analysis of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and red alder (Alnusrubra Bong.) management is conducted using yield projections from the Stand Projection Simulator for the Pacific Northwest region of the United States. The analysis includes uncertainty in the price trends and stocking levels of both species following reforestation. Results from a case study in which Douglas-fir price is likely to increase faster than red alder price show that (i) on more productive sites, greater regeneration investment is justified to increase the likelihood of Douglas-fir establishment; (ii) on less productive sites, low-cost regeneration options that produce mixed-species stands have expected present values close to or greater than a high-cost Douglas-fir regeneration effort; (iii) optimal precommercial removal of red alder depends on midrotation prices and regeneration success, and in many cases growing a mixed-species stand to maturity produces the highest economic return; (iv) commercial thinning of Douglas-fir increases the expected present value of the most intensive regeneration option by up to 10%. The low-cost regeneration options have relatively high expected returns because of low initial investments and the presence of two species that may have high values in the future. The sensitivity of these results to changes in the probability distributions of regeneration success and price trends is discussed.
Determining the effects of harvesting guidelines on the age-class profile of the residual forest
Authors: Nelson J.D. , Shannon T. , Errico D.
Published: July 2007

Chromatic scheduling was used to demonstrate that harvest unit adjacency constraints can be translated into age-class profile constraints that are suitable for regulating the rate of harvest in strategic forest planning models. The advantage of the age-class approach is that strategic harvest rates will reflect the spatial constraints without the onerous task of designing and scheduling cut blocks for the entire forest. Other factors that are relevant to determining the steady-state age-class profile are the exclusion period and the width of the leave strip between any two harvest units. Through the analysis of four spatial data sets it was observed that the chromatic number decreases as the block size increases; however, the absolute block size was not a factor. The controlling factor is the underlying block pattern (maximum number of adjacent units and the number of units sharing a common boundary point). When high chromatic numbers are combined with long exclusions periods the results are long rotations and reduced periodic harvests. There is a wide range in the number and timing of harvest entries and the resulting age-class structures that are spatially feasible. This suggests that resource policy makers should think in terms of the desired residual forest structure prior to prescribing harvesting guidelines.
Vegetation management in tropical forest plantations
Authors: Lowery Robert F. , Lambeth Clem C. , Endo Masatoshi , Kane Michael
Published: July 2007

Forest plantations cover approximately 1% of the tropical land mass capable of supporting forest cover, i.e., 25.3 × 106 ha. Deforestation issues and the high potential growth rates of tropical plantations are driving an increase in reforestation activities in the tropics. The underlying principles and objectives of competition control here are similar to those in other areas of the world. Timely early competition control, until the tree crop gains dominance on the site, has proven critical to the success of these efforts because of the rapid and persistent development of weed competition on most tropical sites. Plantation survival has been increased by as much as 90% with early competition control and volume growth by more than 50% at 2 years short of rotation age. Manual weed control methods are used most extensively in the tropics. Cover crops and grazing have been used only to a limited extent. However, as economic development continues in many tropical countries, mechanical methods and herbicides are being used more widely. Herbicide usage is somewhat problematic in these areas owing to the lack of effective regulatory programs, limited herbicide research, few people knowledgeable and trained in herbicide use, and misinformation regarding herbicides.
Integration of nursery practices and vegetation management: economic and biological potential for improving regeneration
Authors: South David B. , Mitchell Robert J. , Zutter Bruce R. , Balneaves John M. , Barber Brad L. , Nelson Derek G. , Zwolinski Janusz B.
Published: July 2007

Researchers in New Zealand, Scotland, South Africa, Texas, and Alabama provided data on growth responses owing to nursery management practices and weed control after outplanting. Nursery treatments included nitrogen fertilization (0 vs. 168 kg/ha), seedling grades (small-diameter vs. large-diameter seedlings), and a comparison of stock types. Weed-control treatments varied by study and included broadcast and spot applications. Interactions between nursery practices and weed control were examined. Regardless of location, growth (2–8 years after planting) was increased as seedling diameter increased. Practices that increase average seedling diameter in the nursery are typically less costly than silvicultural practices required to obtain similar growth responses from small-diameter stock. Although interactions were observed among sites, stock size, and intensity of weed control, large-diameter stock consistently grew better than small-diameter stock regardless of site or site-preparation method. Thus, increasing the investment of regeneration expenditures at the nursery, relative to that put into site preparation, will substantially improve financial returns on investment. Further research needs in this area are also discussed.
Loblolly pine and mixed hardwood stand dynamics for 27 years following chemical, mechanical, and manual site preparation
Authors: Glover Glenn R. , Zutter Bruce R.
Published: July 2007

A site-preparation study installed in 1959 in Fayette County, Alabama, U.S.A., provides data to evaluate long-term effects of varying densities of hardwood on loblolly pine (Pinustaeda L.) plantation growth, yield, and stand structure. Six treatments (hand girdle; bulldoze scarification; herbicide applied to axe frill, chain frill, and with an injector; and an untreated check) were installed as a randomized complete block with five replications. Periodic measurements of pine and hardwood size and density show that higher hardwood densities existing early in the pine plantation had a substantial negative effect on loblolly pine survival and basal area yield, with the bulldoze and herbicide treatments having less hardwood and higher survival and stand basal area. Pine total height and diameter at breast height were reduced by increasing hardwood density early in the life of the plantation, but size of surviving trees differed little among treatments at later ages, except on plots where most pine trees were suppressed by hardwoods. Strong relationships between pine basal area per hectare at age 27 and both number of hardwood stems at age 3 and percentage of stand basal area in hardwood at age 6 were noted. These relationships indicate promise for predicting long-term growth and yield of loblolly pine plantations from early measures of hardwood interference.
Sample-size needs for forestry herbicide trials
Authors: Zedaker S.M. , Gregoire T.G. , Miller J.H.
Published: July 2007

Forest herbicide experiments are increasingly being designed to evaluate smaller treatment differences when comparing existing effective treatments, tank mix ratios, surfactants, and new low-rate products. The ability to detect small differences in efficacy is dependent upon the relationship among sample size, type I and II error probabilities, and the coefficients of variation of the efficacy data. The common sources of variation in efficacy measurements and design considerations for controlling variation are reviewed, while current shortcomings are clarified. A summary of selected trials estimates that coefficients of variation often range between 25 and 100%, making the number of observations necessary to detect small differences very large, especially when the power of the test (1–β) is considered. Very often the power of the test has been ignored when designing experiments because of the difficulty in calculating β. An available program for microcomputers is introduced that allows researchers to examine relationships among sample size, effect size, and coefficients of variation for specified designs, α and β. This program should aid investigators in planning studies that optimize experimental power to detect anticipated effect sizes within resource constraints.