Treesearch

The effects of aluminum (Al) treatment on polyamines were studied using suspension cultures of Madagascar periwinkle [Catharanthus roseus (L.) G. Don]. The addition of A1 (0.2, 0.5, 1.0 mM) to the suspension cultures caused a significant increase in putrescine within 24h only in freshly transferred cells. By contrast, Al treatment reduced putrescine content at all other times (days 2-7). Further analysis showed that the largest increase in putrescine occurred at 6h when Al was added at the time of transfer of cells to fresh medium. If Al treatment was delayed to as little as 3h after...

Changes in stemwood calcium concentration ([Ca]) for the last 120 years occurred in a common pattern for two sample collections of red spruce (n = 33 and 20) from the northeastern United States and for one sample collection of Siberian fir (n = 20) from southcentral Siberia, Russia. The [Ca]was measured for wood formed during the periods 1871-90, 1891-1910, 1911-30, 1931-50, 1951-70 and 1971-90. For each core, the relative increase or decrease in [Ca] for adjacent periods of wood formation was recorded. The relative frequency of positive change in [Ca] for each period of wood formation was...

Methane fluxes were measured using eddy correlation and chamber techniques during 1991 and 1997 at a peatland in north central Minnesota. Comparisons of the two techniques were made using averages of methane flux data available during 1-week periods. The seasonal patterns of fluxes measured by the two techniques compared well. Chamber flux, in 1991, was about 1.8 mg m-2 hr-1 greater than the flux obtained by the eddy correlation technique. In 1992, the chamber flux was about 1.5 mg m-2 hr-1 higher than the eddy correlation flux prior to midseason and 1.0 mg m-2 hr-1 lower than the eddy...

Clearcutting, a commonly-used cutting practice in southeastern Ohio, often results in a forest stand with a different species composition than the parent stand.

The vegetation data set of the Missouri Forest Ecosystem Project (MOFEP, initiated by the Missouri Department of Conservation) in the Ozark Mountains of southeastern Missouri was ordinated by Detrended Correspondence Analysis (DCA) to identify vegetation gradients and potential environmental influences.

Horizontal starch gel electrophoresis was performed on six polymorphic loci in black walnut (Juglans nigra L.) embryos from open-pollinated nut collections made in 1987 in a Missouri half-sib progeny test, and Indiana seed orchard and a natural population in southern Illinois.

Differences in bark thickness in relation to diameter at breast height were observed in a 30-32 year old Illinois planting of 32 provenances of northern red oak (Quercus rubra) from throughout its natural range. Bark thickness by itself is often a good indication of relative cambial insulation from fire. Fire resistance in trees can largely be attributed to thickness and low thermal conductivity of bark. Western and southern provenances tended to have greater average bark thickness to dbh ratios than northern or eastern provenances because we tested latitude and longitude separately. One...

Regenerating northern red oak (Quercus rubra L.) on good to excellent growing sites is a serious problem for forest managers throughout the eastern and central United States.

Nitrogen (N) and phosphorus (P) are nutrients often limiting forest site productivity.

Recent research has shown that some timber harvesting methods adversely impact salamander populations.