Treesearch

The consumption of forest products emanating from tropical rainforests is an issue that is receiving increasing attention in the United States. This attention stems from concerns over the sustainability of tropical ecosystems. However, trade statistics show the United States imported only 4.0 percent of all tropical timber products traded globally in 1989. In addition, the global trade in tropical timber products is estimated to be directly responsible for only about 4 percent of the volume of tropical forests cut. Therefore, U.S. imports account for less than two-tenths of one percent of...

The quality of data concerning international hardwood products trade declined in the 1980s because of several problems associated with the collection and processing of individual export transaction records. This note examines the source, impact, and remedies for data problems caused by data screening procedures, nonreporting, recording errors, and alternative accounting systems. Although this study focuses on the hardwood products, many of the problems discussed affect trade data for other forest products.

We documented 3 to 14°C of dehardening in current-year foliage of 10 mature, montane red spruce (Picea rubens Sarg.) trees during a natural thaw from 12 to 21 January 1995. Mean cold tolerance was about -47°C before the onset of thaw conditions, and individuals ranged from -38 to -52°C. After 3 days of thaw, mean cold tolerance dropped to -39°C, with a range of -32 to -44°C. Trees did not regain prethaw levels of cold tolerance until sometime between 31 January and 9 February, or 10 to 20 days after subfreezing temperatures resumed. The least cold tolerant tree was at risk of injury when...

In sapwood challenge experiments in Acer rubrum, columns of discolouration initiated by wounding and inoculation with pioneer fungi (Cephalosporium sp., Phialophora sp.) were similar in size to untreated wounds. Inoculation with decay fungi (Pleurotus ostreatus, Trametes versicolor) produced larger columns of wound-initiated discolouration. The removal of bark around a bore wound caused a significantly larger column to form compared to the sum of the columns initiated by separate wounds. Stage-I discoloured wood, not associated with obviously rotted wood, had concentrations of mobile...

Root chemistry is being increasingly used as a marker of biologically relevant soil chemistry. To evaluate this marker, we determined the precision of measurement, the effect of organic soil horizon, and the effect of stand elevation on the chemistry of fine root tips of red spruce (Picea rubens Sarg.) Fine root tips were collected from the F and H horizons of the forest floor of nine locations. Six of the locations were selected as pairs that differed in elevation. The concentrations of Al, Ca, Mg, and Fe in fine root tip collections were determinined by direct current plasma emission...

We evaluated winter (January through March) carbon assimilation of red spruce (Picea rubens Sarg.) from three Vermont seed sources grown in a common garden in northwestern Vermont. Although CO2 exchange rates were generally low, net photosynthetic rates increased during two prolonged thaws. Significant correlations between CO2 exchange rates and multiday air temperature means supported our observations of enhanced gas exchange during extended periods of elevated temperature. Increases in photosynthesis during thaws occurred before observed increases in leaf conductance, indicating that...

Calcium is the fifth most abundant element in trees, and is an essential component for wood formation and the maintenance of cell walls. Depletion of Ca from the rooting zone can result in acidification of soil and surface water and possibly growth decline and dieback of red spruce. During the past six decades, concentrations of root-available Ca (exchangeable and acid-extractable forms) in forest-floor soils have decreased in the northeastern United state. Both net forest growth and acid deposition have been put forth as mechanisms that can account for this Ca depletions. Here, however,...

Large numbers of sugar maple seed are dispersed every second or third year. Very little seed was damaged by insects or mammals prior to dispersal. The trapping methods used prevented major losses following seed fall. Seed production was positively correlated with tree diameter but not with age of seed trees.

Manipulation of stand stocking through thinning can increase the amount of oak in the upper crown classes and enhance individual tree characteristics that promote good acorn production. Identification of good acorn producers before thinning or shelterwood harvests can be used to retain them in a stand. Stocking charts can be used to time thinnings and to estimate acorn production for individual stands. Maintaining stocking between A- and B-level ensures complete use of growing space by trees. As stocking approaches the A-level, thinning back to the B-level should maintain oak in the upper...