ALBERT

Beschreibung: Atmospheric deposition of nitrogen and sulfate is acidifying some ecosystems, potentially increasing the availability of aluminum in the soil solution. The effects of Al on tulip-poplar (Liriodendron tulipifera L.) were investigated with seedlings grown in sand culture. Seedlings were exposed to Al at four concentrations ranging from 0 to 800 µM. Reductions of 77% in shoot biomass and 71% in root biomass were observed at 200 µM Al. Aluminum reduced the concentrations of multivalent cations in leaves and roots. The Ca concentration of leaves was reduced at 400 µM Al, and the Mg concentration of roots was significantly reduced at 200 µM Al. Relationships between tissue Ca, Mg, and Al indicated that Al alters the translocation of Ca and Mg to the shoots and the accumulation of Mg in the roots. If mature trees respond in a similar fashion as seedlings noted here, then tulip-poplar has a low threshold for A1 toxicity, which may lead to declines in the health of tulip-poplar populations in ecosystems exposed to elevated levels of acidic deposition.

Beschreibung: From 1989 to 1996, ion deposition in precipitation, throughfall, and stemflow were measured under a deciduous and a coniferous stand, located in the Lake Clair Watershed, during the growing and the dormant seasons. During the growing season, throughfall deposition under both stands was significantly depleted in H+ and NH4+ compared with wet deposition, and a significant uptake of NO3- was observed under the coniferous canopy. Deposition of Ca2+, Mg2+, K+, Na+, Cl-, and SO42- was significantly higher in the throughfall than in the wet precipitation. During the growing season, the coniferous stand was more efficient in retaining nitrogen (NH4+ and NO3-), while H+ was more intensively retained in the deciduous stand. Significant interactions between precipitation and forest canopies were also observed during the dormant season: throughfall depositions of Ca2+, Mg2+, K+, Na+, and Cl- were significantly higher than wet precipitation under both canopies, while throughfall SO42- was significantly enriched only under the coniferous stand. Using a Na+ ratio method, foliar leaching was found mostly responsible for the throughfall enrichment on a full-year basis in both stands, with values averaging 61, 73, and 96% of the total throughfall fluxes for Ca2+, Mg2+, and K+, respectively. Under both stands, net canopy exchange (NCE) of base cations, expressed on a monthly basis, were correlated to water volume and to H+ and SO42- deposition. Multiple regression models including wet SO42- deposition and an estimate of dry S deposition, explained up to 88% (Ca2+ in the coniferous stand) of the variance in base cation NCE under both stands.

Beschreibung: Pistillate flower development and acorn production were observed in small populations of white oak (Quercus alba L.) and black oak (Quercus velutina Lam.) in central Missouri from 1990 to 1997. There were significant year-year differences in the size of flower crops for both species and significant tree-tree differences in black oak. About 7% of the white oak flowers matured into acorns; most flowers aborted by early July, just after fertilization. About 12% of the black oak flowers matured into acorns, but some individual trees never or rarely produced a mature acorn. The number of fertilized flowers in white oak and black oak in early July was positively correlated with acorn production. Over all trees and years, the number of flowers and acorns were significantly correlated. Acorn production varied in relation to weather variables during the time of pollination. Simple regression models were good predictors of white oak acorn production but not of black oak acorn production. Maximum temperature and the number of days with hail had negative effects on acorn production. The number of days of rain during the pollination period was positively correlated with flower survival in black oak but not with white oak.

Beschreibung: A trial planted on six sites representing five growth modelling regions and a range of site qualities in New Zealand was used to examine the interaction of silviculture and genetic improvement in Pinus radiata D. Don. Four seed lots with differing genetic potential for growth were grown under four stocking treatments from 100 to 600 stems/ha, all with a thinning ratio of 5:2. In addition, two treatments were planted at 500 stems/ha, one pruned and one unpruned. Among sites, differences were large for mean top height (8.1-13.9 m), basal area (7.9-21.5 m2/ha), and volume (25-108 m3/ha) at 8 years from planting. Differences among silvicultural treatments were large for basal area (with a range of 4.3-18.8 m2/ha over sites) and volume (17-86 m3/ha) and smaller but statistically significant for mean top height (10.1-11.6 m). Differences among seed lots were statistically significant for all traits but larger for basal area (12.1-13.6 m2/ha) and volume (51-59 m3/ha) than for height (10.7-11.1 m). Genetically different seed lots performed similarly relative to each other over the range of sites and silvicultural treatment, with a slight trend for greater differences among seed lots in the faster growing silvicultural treatments. However, differences in tree growth were many times greater among sites and silvicultural treatment than among genetically different seed lots.

Beschreibung: Dendroecological techniques were used to study the dynamics and species recruitment patterns, spanning nearly four centuries, for a mesic, montane, old-growth forest in Hokkaido, northern Japan. The forest is dominated by Abies sachalinensis (Masters), Acer palmatum (Thunb.),Quercus mongolica var. grosseserrata (Rehd.), and Cercidiphyllum japonicum (Sieb.). From 1620 to 1750 and 1820 to 1840, Q. mongolica exhibited continuous recruitment into the overstory. A lack of recruitment for all tree species from 1750 to 1820 followed a 1739 volcanic eruption 200 km from the study area. Release events for individual trees occurred almost every decade of the stand history, indicating that frequent small-scale disturbances coupled with infrequent large-scale disturbances, impact tree growth and species recruitment. From 1870 to 1950, canopy recruitment of Abies and Acer dominated the forest, while recruitment of Quercus ceased. These later successional species appeared to be replacing Quercus, suggesting that the syndrome of declining oak dominance is an increasingly global phenomenon. However, successional patterns in the forest are difficult to predict because intensive deer browsing has recently prevented canopy recruitment of all tree species and the possibility of future large-scale disturbances, such as fire and volcanic eruption.

Beschreibung: Based on relative abundance data, partial cutting has been suggested as a technique to maintain habitat for birds associated with late-seral forests, but there has been little study of partial cutting effects on nesting success. One of the primary limitations to nesting success is nest predation. We compared predation rates (proportion of nests disturbed in a 14-day period) in partially cut (30 or 60% basal area removal), clearcut, and uncut forests in northwestern British Columbia, in two experiments using ground-placed (1993) and shrub-placed (1998) artificial nests. In the ground-nest experiment there was a very low predation rate (0.06) and no detectable difference among treatments (p = 0.403). In the shrub-nest experiment, there was a 0.36 predation rate and little evidence of treatment differences (p = 0.295). Based on 90% confidence intervals for differences in observed predation rate, the 30% removal clearly did not increase predation risk relative to uncut forest. With the 60% removal, however, we cannot rule out a possible increase in predation risk compared with either uncut forest or clearcuts.

Beschreibung: Full-sib progeny and clonal trials to evaluate family and clone performance were simulated on a test site with various patterns of environmental variation to examine the effectiveness of randomized incomplete block designs (ICBs) under different design parameters (constant block size, variable block size, block shape and orientation, and family size). Simulations showed that blocks of fixed size 5-20 were effective in removing most site variation in a test with 120 full-sib families of three seedlings per family. Slight variations in block size did not affect the precision of mean estimations much when blocks were considered random. Square blocks were more effective than either column or row blocks in removing both patchy variation and gradients in one direction. With blocks of fixed size 10, increasing family size from 3 to 12 (at the expense of family number, which dropped from 120 to 30) reduced the average variance of family mean contrasts by 75%; most of this reduction (〉50%) was achieved at 6 seedlings per family. The differences in precision of mean estimation between full-sib progeny and clonal trials were small with respect to the design parameters and patterns of site variation examined.

Beschreibung: Coarse woody debris (CWD) chronosequences were developed for managed and unmanaged red pine (Pinus resinosa Ait.) stands across the Great Lakes states. Throughout stand development, there is less CWD in managed than in unmanaged forests, and effects of management are strongest in young forests (0-30 years old). At stand initiation, CWD is 80% lower in managed than unmanaged forests, 20 200 versus 113 200 kg·ha-1, while at 90 years, CWD is 35% lower, 6600 versus 10 400 kg·ha-1. Timber management especially affects snags. In young managed forests, snag biomass is less than 1% of that in unmanaged forests, 150 versus 58 200 kg·ha-1, while log biomass is 80% lower, 5000 versus 22 800 kg·ha-1. This trend continues in mature forests (91-150 years old), where snag biomass is 75% lower in managed than in unmanaged forests, 1700 versus 6400 kg·ha-1. Management has relatively little impact on total log biomass of mature forests but increases the biomass of fresh logs nearly 10-fold, to 1400 versus 150 kg·ha-1. CWD in managed forests is highly variable, primarily related to thinning schedules in individual stands.

Beschreibung: Grain angle on bark (angle between the general direction of bark fissures and the axis of the trunk) was assessed at the four cardinal points at breast height (1.3 m) on 82 standing sessile oaks (Quercus petraea Liebl.). After felling, wood spiral grain was measured at breast height from cambium to pith along two diametrically opposite radii. A mixed-effect model that links the tangent of grain angle to radial position (age and distance from the pith) allows to estimate two individual parameters of grain angle. In the field, nondestructive measurements of grain angle (subcortical spiral grain or spiral grain on bark) on an individual tree combined with information on the tree stand allow to estimate one of the two parameters that describes the change in grain angle for a given radial increment. This parameter is independent of mean ring width, tree age and circumference, and site characteristics; it should allow a more accurate identification and selection of standing trees with low wood spiral grain.

Beschreibung: We examined whether nest predation in unharvested blocks of trembling aspen (Populus tremuloides Michx.) would increase when adjacent stands were clearcut in the boreal mixedwood forest of Alberta, in 1993, 1994, and 1998. Artificial nests placed on the ground and in shrubs were baited with Chinese painted quail (Coturnix chinensis L.) and plasticine eggs, which along with cameras, were used to identify nest predators. Fragmented sites were isolated from continuous forest by clear-cutting in 1994, while control sites remained unfragmented. Overall, predation on ground and shrub nests did not increase in isolated forest patches post-harvest (p = 0.056 and p = 0.085, respectively), nor was there a consistent effect of distance from a clearcut edge (p 〉= 0.050). Predation on ground nests was higher in 1994 and 1998 compared with 1993 levels (p 〈 0.001), while predation on shrub nests remained relatively constant over the 3 years (p 〉= 0.073). Mice, voles, and red squirrels (Tamiasciurus hudsonicus Erxleben) were the main identified predators of ground and shrub nests, respectively. Probability of nest predation could not be consistently predicted by nest site vegetation or adjacent land cover, but was related to predator abundance. However, neither predators nor songbirds congregate at recent clearcut-forest edges, and we conclude that elevated nest predation caused by clear-cutting may not occur in the boreal mixedwood, at least not at current levels of harvest and within 5 years of clear-cutting.