Treesearch

Increased ambient carbon dioxide (CO2) has been found to ameliorate water stress in the majority of species studied. The results of many studies indicate that lower evaporative flux density is associated with high CO2-induced stomatal closure. As a result of decreases in evaporative flux density and increases in net photosynthesis, also found to occur in high CO2 environments, plants have often been shown to maintain higher water use efficiencies when grown at high CO2 than when grown in normal, ambient air. Plants grown at high CO2 have also been found to maintain higher total water...

We used the plastochron index to study the relationship between plant age, leaf age and development, and net photosynthesis of black cherry (Prtmus serotina Ehrh.) seedlings. Leaf area and net photosynthesis were measured on all leaves >=75 mm of plants ranging in age from 7 to 20 plastochrons. Effects of plant developmental stage on leaf area and net photosynthesis were evaluated for leaves of differing age (horizontal series), leaves on plants of constant age (vertical senes), and leaves of constant age (oblique series). Regression techniques were used to estimate leaf area from leaf...

A method to distribute tree quality was incorporated into the NE-TWIGS individual-tree growth and yield simulator. The program uses potential tree grade to allow changes in actual tree grade over time. Volume is reported by grade and value is calculated using tree grades. Example screens are shown.

Traveling costs incurred during extensive forest surveys make cluster sampling cost-effective. Clusters are specified by the type of plots, plot size, number of plots, and the distance between plots within the cluster. A method to determine the optimal cluster design when different plot types are used for different forest resource attributes is described. The method requires cost and variance relationships in order to develop an optimal design. The cluster design developed for the Forest Health Monitoring Program of the United States is presented.

Three closely related species, Phlebia rufa,P. acerina, and P. radiata,were analyzed with molecular, morphological, genetic, and physiological methods. Emphasis was placed on the phenotypically similar taxa P. rufa and P. acerina. Phlehia acerina is common and widely distributed in North America, but P. rufa occurs only in Washington, Oregon, and British Columbia. Although often considered conspecific P. acerina and P. rufa are intersterile. In addition, differences in basidioma and cultural traits support their separation. At the molecular level, these species differ slightly in sequence...

A Ground Based Harvesting System Simulation model (GB-SIM) has been developed to estimate stump-to-truck production rates and multiproduct yields for conventional ground-based timber harvesting systems in Appalachian hardwood stands. Simulation results reflect inputs that define harvest site and timber stand attributes, wood utilization options, and key attributes of the harvesting operation. Statistical validation of GB-SIM was conducted with harvesting production data collected from 16 harvest units and 2 logging operations, including partial cuts and clearcuts in Appalachian hardwood...

To evaluate the potential for moderating the visual impact and soil disturbance associated with timber harvesting on steep-slope hardwood sites, thinning and shelterwood harvests were conducted with a skyline yarding system. Operations were monitored to document harvesting production, residual stand damage, soil disturbance, and visual quality. Yarding costs for thinning, removing 1,310 ft³/acre, were 30 percent higher than those for the conventional shelterwood (2,060 ft³/acre), and 33 percent higher than those for the irregular shelterwood (2,290 ft³/acre). Ninety percent of the harvested...

Microdensitometric analysis of aerial photographs has been used to quantify urban tree stress of deciduous species. A test of this procedure applied to Monterey pine indicates that variations in ground cover beneath urban trees among cities and variations in crown morphology among tree species can limit the ability of microdensitometry to quantify urban tree stress.

In much of the Central Hardwood Forest Region, oak species are not regenerating well, even though large oak trees are common within the existing forests. The shelterwood method has been suggested as a potential tool for establishing and developing advanced regeneration where it is lacking. The 10-yr results from a study of several variants of the shelterwood method show that on good sites in the Missouri Ozarks Region, a heavy understory treatment is most important, while on average sites, reducing the overstory density level is most important. The right combinations of overstory and...

The history of Oakland, California's urban forest was researched to determine events that could influence future urban forests. Vegetation in Oakland has changed drastically from a preurbanized area with approximately 2% tree cover to a present tree cover of 19%. Species composition of trees was previously dominated by coast live oak (Quercus agrifolia), California bay (Umbellularia californica), and coast redwood (Sequoia sempervirens) and is currently dominated by blue gum (Eucalyptus globulus), Monterey pine (Pinus radiata), and coast live oak. Many forces throughout the history of...