ALBERT

Beschreibung: A mechanized whole-tree harvest was conducted on a watershed in central Maine dominated by Picearubens Sarg. and Abiesbalsamea (L.) Mill. The harvest removal and redistribution of biomass, nitrogen, phosphorus, calcium, magnesium, and potassium were estimated and evaluated with respect to estimates of site nutrient reserves. Regression equations were developed to estimate the nutrient contents and ovendry weight of the aboveground components of the Picearubens and Abiesbalsamea. Unit area estimates of nutrient and biomass removals were based on the application of the regression equations to a tally of all trees on twelve 0.04-ha square plots. Unit area estimates were made of exchangeable and total nutrients contained in the forest floor and glacial till above a hardpan. The harvest removed 90% of the biomass, 91 % of the nitrogen, phosphorus, potassium, and calcium, and 90% of the magnesium in the above-stump portions of the forest. These removals were from two to four times the amount of nutrients that would have been removed by a bole-only harvest, while increasing biomass removals by 1.4 times. The nutrients removed by the harvest were between 0.1 and 5% of the total soil reserves. Nutrient removals are evaluated in the context of three commonly used evaluation approaches: static comparisons of nutrient pools, nutrient input–output budgets, and computer simulation.

Beschreibung: Soil CO2 evolution rates were measured in slash pine (Pinuselliottii) plantations of three ages in north Florida. At the mature (29-year-old) plantation, which had a closed canopy and a well-developed forest floor of litter and humus overlying the mineral soil, C storage in detritus in the mineral soil was relatively low and soil C release was relatively high (13.0 t•ha−1•year−1). C release was highest (22.7 t•ha−1•year−1) at the clear-cut site, presumably because of high temperatures and rapid decomposition of detritus added during the harvest, and lowest (8.2 t•ha−1•year−1) at the 9-year-old plantation. For a range of forest sites, soil CO2 evolution rates and the magnitude and direction of changes after harvesting show latitudinal variation that probably depends not only on the amount of C contained in dead organic matter in the soil and its decomposition rate but also on the treatment of slash left after harvesting.

Beschreibung: Five principal semiochemicals were field tested in multiple funnel traps for behavioral activity against Dendroctonusponderosae infesting lodgepole pine, Pinuscontorta var. latifolia Engelmann, in British Columbia. The basic experimental design was to test each compound by adding it in varying concentration or enantiomeric composition to a blend of other semiochemicals. (−)-trans-Verbenol was attractive to both sexes. (±)-exo-Brevicomin and (±)-frontalin (in one of two experiments) were attractive with other semiochemicals to females at a release rate of 0.05 mg/24 h. At higher release rates (±)-exo-brevicomin was inhibitory to males, and frontalin was inhibitory to both sexes. Thus both serve as multifunctional pheromones. For neither exo-brevicomin nor frontalin were the separate enantiomers attractive at the low release rate, suggesting that they had an additive effect. However, at the high release rate both enantiomers mimicked the inhibitory effect of the racemates. Verbenone acted as an antiaggregation pheromone for both sexes. Increasing the release rate of myrcene from 18 to 150 mg/24 h to approximate the release rate from a newly attacked tree had the effect of doubling the catch of responding beetles. A conceptual model is proposed for the sequential interaction of these semiochemicals in the mass attack of a tree. Pioneer females release trans-verbenol, which acts in combination with myrcene from the host tree to attract mainly males. The responding males release exo-brevicomin and later frontalin, which in combination with trans-verbenol and myrcene attract mainly females. Meanwhile autoxidation of α-pinene in the host resin results first in the production of predominately trans-verbenol, which supplements that produced by the beetles. Later, autoxidation of α-pinene and microbial conversion of cis- and trans-verbenol result in the production of the antiaggregation pheromone verbenone. This compound, in combination with large amounts of exo-brevicomin and frontalin as the tree becomes fully occupied, results in the close-range redirection of responding beetles toward nearby trees.

Beschreibung: A mechanized whole-tree harvesting system, which has recently found widespread use in northern New England, was evaluated for its impact on residual crop trees in two northern hardwood stands in western Maine. Stand type, skid trail spacing, and whether or not skid trails were designated prior to harvesting significantly influenced stand damage levels. A higher mean percentage of residual trees was injured in a Betulapapyrifera Marsh, stand (49%) than in similar treatments in a Fagusgrandifolia Ehrh. – Quercusrubra L. stand (32%). A spacing of 20 m between predesignated trails resulted in less damage (22%) to the remaining trees than a spacing of 40 m (53%), but with many more potential crop trees cut for trails. At both sites, highest total damage was found in treatments where no skid trails were predesignated, with 82 and 43% of the crop trees damaged or removed in the B. papyrifera stand and the Fagus–Quercus stand, respectively. Models were developed to predict the effects of thinning systems, tree size, species, dbh, stand basal area, and distance from tree to skid trail on the probability of being damaged. High damage levels indicate that such harvesting systems are unsuitable for some sites and require careful planning and layout on all sites.

Beschreibung: Nitrogen fertilization rate trials (0–672 kg/ha) were established in seven second-growth mixed deciduous forest stands in southern New York, on well to somewhat poorly drained soils typical of better hardwood sites, with no history of fire or cultivation. Basal-area growth over 20 years was determined from increment cores of dominant and codominant trees. Significant growth response occurred only for black cherry (Prunusserotina Ehrh.). Nitrogen additions of 168–336 kg/ha increased growth 21% over 5–10 years. Ten-year basal-area growth response of sugar maple (Acersaccharum Marsh.) and white ash (Fraxinusamericana L.) was less than in other fertilization studies. The lack of response is attributed to favorable nitrogen status of the soils, resulting from lack of disturbance over at least the last four decades and, possibly, atmospheric input of nitrogen.

Beschreibung: Genetic and environmental variances in cone size, seed yield, and germination properties were evaluated for Piceamariana (Mill.) B.S.P. using material from ramets of 19 clones in a northern Ontario seed orchard. Thirty-seven percent of the variance in cone volume (mean, 2.2 cm3) was accounted for by differences among clones (range, 1.3–3.5 cm3) and 19% was accounted for by ramets within clones. Clone means for number of seed per cone ranged from 49 to 100 and averaged 71; 18% of seed was filled. Clonal variances for number of seed per cone and percent filled seed were 31 and 23% of the total variance, while ramets accounted for 18 and 13%, respectively. Germination of filled seed averaged 68% and clone means ranged from 28 to 90%. Sixty-seven percent of the variation in germination percent was due to clonal differences and 18% was associated with ramets.

Beschreibung: Asymbiotic nitrogen fixation in litter was assayed by acetylene reduction across a range of 25 forested sites in the Willamette Valley and Oregon Cascade and Coast ranges and periodically over a year at two Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) plantations in the Willamette Valley. Laboratory experiments showed that optimal conditions for N fixation by Douglas-fir litter were 200% moisture content and 22 °C. Annual fixation was 1.08 ± 0.13 kg/ha at one Willamette Valley plantation, 0.39 ± 0.06 kg/ha at the other. Fixation rates at the other 23 sites, which were sampled less frequently, ranged from 0 to 5 g N ha−1 day−1 and exceeded trace levels at only six sites, indicating annual totals much less than those at the Willamette Valley plantations. At four coastal and valley sites sampled by litter layer, older L layer Douglas-fir litter fixed the most N per gram dry weight. Percent N, percent C, and the C:N ratio of that litter layer did not differ significantly among sites or correlate with N-fixation rates. Forest-floor litter in most Northwest forests fixes no more than trace amounts of N, at most ~1 kg N ha−1 year−1. These amounts are smaller than N input from precipitation.

Beschreibung: Bald cypress (Taxodiumdistichum L.) seedlings were subjected to flooding with saline water containing 0 to 8 parts per thousand (137 mequiv. L−1 NaCl) under controlled environment conditions. Imposition of flooding and salinity stresses was designed to simulate the increase in submergence and salinity level which Louisiana's extensive cypress forests are currently experiencing as a result of rapid subsidence. The effect of flooding and salt water intrusion on subsequent stomatal behaviour and net photosynthesis for leaves developed before and after salt exposure were measured. Flooding and salinity resulted in a substantial decrease in stomatal conductance and net photosynthesis in both young and old leaves. Leaf aging did not significantly affect stomatal conductance and photosynthesis. Only plants flooded with freshwater and those flooded with low salinity concentration produced new leaves with improved stomatal conductance and net photosynthesis, which suggests some stomatal and photosynthetic acclimation to flooding and low salinity for bald cypress. Increase in salinity, however, caused more extensive impact and greater reductions of stomatal conductance and net photosynthesis in both leaf ages.

Beschreibung: The decay rate of Abiesconcolor (Gord. & Glend.) Lindl. logs and cover, mass, and volume of logs and snags in six midelevational forest stands of Sequoia National Park, California, are reported. Based on a chronosequence, Abiesconcolor boles have a decay rate-constant of 0.05 year−1 and a half-life of 14 years. A decay classification system was developed for Abiesconcolor, Calocedrusdecurrens (Torr.) Florin, Pinusjeffreyi Grev. & Balf., and Pinuslambertiana Dougl. logs. Dimensions taken from maps of six permanent plots were combined with decay-class information to estimate volume, mass, and projected cover of logs and snags. Total mass ranged from 29 Mg ha−1 in a Pinusjeffreyi forest to 400 Mg ha−1 in a Sequoiadendrongiganteum (Lindl.) Buchh. dominated stand. Volume, projected cover, and nitrogen storage exhibited patterns similar to mass, ranging from 84 to 1160 m3 ha−1, 3.1 to 9.3%, and 41 to 449 kg ha−1, respectively.

Beschreibung: Aboveground biomass and leaf area, net primary production, and nutrient cycling through vegetation were studied for 3 years after clear-cutting (stems only) of a 10.24-ha watershed in the Oregon Cascade Mountains. The riparian zone and four main habitats were analyzed separately. In 3 years, aboveground net primary production increased from 5 to 112 g•m−2•year−1 in the ridgetop habitat; midsummer aboveground biomass increased from 8 to 196 g/m2 in the riparian zone and from 198 to 327 g/m2 on the ridgetop. Other values were intermediate to these. Litter fall of species with perennial aboveground parts averaged 20–27% of standing biomass. Native annuals, especially Araliacalifornica Wats., dominated the riparian zone. Seneciosylvaticus L., an introduced species, dominated most of the rest of the watershed, except for the ridgetop habitat, which was dominated by residual woody shrubs. Uptake of N exceeded losses in streamflow the 1st year and was six times greater in the 2nd; uptake of P and K in that year was 2.5 and 3 times greater than losses. In the 3rd year, total uptake of K (2.5 g•m−2•year−1) equaled the preclear-cutting level, and uptake of N (1.3 g•m−2•year−1) and P (0.3 g•m−2•year−1) was about half that level. No correlation was found between plant uptake and nutrient loss in streamflow. Uptake of all elements exceeded return through leaching and litter fall by 16%, except that of Mg, which exceeded return by 44%. Because of early dominance by species with annuals, the proportion of elements redistributed internally by vegetation was generally low. The amount of nutrients in flux through vegetation, atmosphere, and stream was small in comparison to the amount lost in the removal of tree stems.