Treesearch

Several types of root barriers tested in field experiments in northern California inhibited development of shallow tree roots. The need for an improved barrier design to prevent development ofpotentially harmful circling roots inside a barrier was indicated. The performances of various currently marketed root barriers with internal vertical ribs were compared to augment product descriptions by their manufacturers.

Three-year-old seedlings of southwestern black cherry (Prunusserotinasubsp. virensvar. virens with rootballs 35 and 70 cm deep were field planted in northern California in April 1986 to compare the effects on root development of rootballs of two depths and a root barrier, which was a polyethylene casing around the rootballs of half of the trees of each treatment. Three growing seasons later, the roots were excavated to a depth of 32 cm in an area within a radius of 1 m from the tree trunks and dry weights of the exposed roots of each tree determined. There was no significant difference in...

Four-year-old seedlings of European hackberry (Celtis australis) with rootballs 35 cm (14 in.) and 70 cm (28 in.) deep, were field planted in northern California in April. 1986. to compare root development as affected by rootball depth and a casing that fit snugly around the rootball to function as a root barrier. Three growing seasons later, the roots of each tree were excavated to a 32-cm depth in an area within approximately 1 m radius from the trunk and the dry weights of these roots determined. Root weight was significantly different between the two root barrier treatments but not...

A 25 foot tree reduces annual heating and cooling costs of a typical residence by about 8 to 12 percent ($10-$25). Assuming savings of $10 per household, a nationwide residential tree planting program could eventually save about $1 billion each year. Direct shade on the building will account for most of these savings in hot climates, while heating and cooling savings from reduced wind speeds and evapotranspirational cooling will be relatively more important in cooler climates. The energy conservation potential of landscapes is greatest in residential and commercial land uses, where...

There is increasing concern about the predicted negative effects of the future doubling of carbon dioxide on the earth. This concern has evoked interest in the potential for urban greenspace to help reduce the levels of atmospheric carbon. This study quantifies greenspace-related carbon storage and annual carbon fluxes for urban residential landscapes. For detailed quantification, the scale of this study was limited to two residential blocks in northwest Chicago which had a significant difference in vegetation cover. Differences between the two blocks in the size of greenspace area and...

Among all global ecosystems, tropical savannas are the most severely and extensively affected by anthropogenic burning. Frequency of fire in cerrado, a type of tropical savanna covering 25% of Brazil, is 2 to 4 years. In 1992 we measured soil fluxes of NO, N20, CH4, and C02 from cerrado sites that had been burned within the previous 2 days, 30 days, I year, and from a control site last burned in 1976. NO and N20 fluxes responded dramatically to fire with the highest fluxes observed from newly burned soils after addition of water. Emissions of N-trace gases after burning were of similar...

We tested whether variation in growth of native koa (Acacia koa) forest along a rainfall gradient was attributable to differences in leaf area index (LAI) or to differences in physiological performance per unit of leaf area. Koa stands were studied on western Kauai prior to Hurricane Iniki, and ranged from 500 to 1130 m elevation and from 850 to 1800 mm annual precipitation. Koa stands along the gradient had basal area ranging from 8 to 42, LAI ranging from 1.4 to 5.4, and wood increment ranging from 0.7 to 7.1 tonnes/ha/year. N, P, and K contents by weight of sun leaves (phyllodes) were...

Relationships between (1) degree of damage caused by the 1987 fires in northern California and (2) prior management activities, fuelbed characteristics, and site/stand factors were studied on the Hayfork Ranger District of the Shasta-Trinity National Forests. Postfire aerial photography was used to assess scorch and consumption of tree crowns (the selected measure of fire damage), and other data were obtained from existing records. Data were collected and analyzed separately for (1) plantations and (2) uncut and partial-cut stands. Ordinal logistic regression was the primary analytical...

Change in the spatial characteristics of forest openings was investigated in three forested watersheds in northwestern Siskiyou County, California totalling approximately 24,600 hectares. Watersheds with minimal human disturbance were chosen for study. However, fi;e suppression has been pervasive throughout. Characteristics of forest openings (area, perimeter, distance between neighboring openings) were measured on aerial photographs taken 41 years apart. An index of regional form was determined for the landscape. Shape complexity for each opening was calculated using two indices based...