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Comparison of the Frictional Properties
of Several Popular Arborist Blocks
by Peter S. Donzelli
Abstract. Commercial arborists spend much of the workday managing
friction. In some places, friction is needed, but in others it can be a
hindrance; the arborist block is one place friction is not wanted. This
device is attached to the tree and supports a rope used to lower wood during
pruning or removal operations. When a short section of rope is led from
the wood to the block, then a much longer section from the block to the
ground, friction will cause the force in the short leg to be larger. This
short leg of rope, with limited rope fiber, is required to absorb more
energy than the corresponding longer leg. In the extreme case, this may
lead to failure of the rope, and hence motivates the desire to quantify
the friction that may be present in this device. Three blocks were tested
for the coefficient of static friction during raising and lowering. The
friction coefficient was nonlinear with the load being managed, and ranged
from 0.049 to 0.99 over all the loads and among the 3 blocks.
Effect of Tree Shelters on Survival,
Growth, and Wood Quality of 11 Tree Species Commonly Planted in the Southern
United States
by David H. West, Arthur H. Chappelka, Kenneth M. Tilt, Harry G. Ponder,
and J. David Williams
Abstract. One-year-old seedlings of 11 commonly used southern
urban shade tree species were planted with and without plastic shelters
and grown for 3 years (1993-1995) to determine shelter effects on tree
growth, survival, and appearance. Shelters increased the percentage of
survival of all species except Katsura tree (Cercidiphyllum japonicum).
After 2 years, survival was approximately 85%, compared to 50% for nonsheltered
trees, with sheltered sawtooth oak (Quercus acutissima), green ash
(Fraxinus pennsylvanica), nuttall oak (Q. nuttallii), Chinese
elm (Ulmus parvifolia), swamp chestnut oak (Q. michauxii),
and northern red oak (Q. rubra) having at least 90% survival. Seventy
percent of the sheltered and 88% of the nonsheltered trees that died did
so during the first year of the study. Shelters increased height growth
of sawtooth oak, green ash, white oak (Q. alba), nuttall oak, eastern
redbud (Cercis canadensis), swamp chestnut oak, and northern red
oak after 3 years. Shelters had a negative effect on basal diameter of
flowering dogwood (Cornus florida) and Chinese elm during the first
2 years, and a positive effect on basal diameter of swamp chestnut oak
in year 1. After 3 years, neither crown area, woody biomass, nor wood density
were influenced by shelters. Due to increased survival and height growth,
tree shelters may help in establishment of seedling sawtooth oak, green
ash, Chinese elm, white oak, redbud, nuttall oak, swamp chestnut oak, and
northern red oak in urban areas of the southern United States.
Species Differ in Responses
to Tree Shelters
by Henry D. Gerhold
Abstract. Effects of tree shelters on height, caliper, and diameter
at breast height of 11 landscape tree species and cultivars were investigated
in 2 nurseries during a 4-year period; the ratio of height to caliper was
calculated as an indicator of trunk sturdiness. Species differed greatly
in their responses, ranging in the fourth year from none to 44% and 55%
height increases of Magnolia 'Merrill' and M. stellata accompanied
by 18% and 14% caliper increases. Acer griseum, Carpinus caroliniana,
Cercis canadensis, Cornus 'Celestial' and 'Constellation',
Prunus serrulata 'Kwanzan', and P. subhirtella autumnalis
exhibited more modest height increases, but also caliper decreases, compared
to controls without shelters. Malus 'Adirondack' and Syringa
reticulata 'Summer Snow' did not benefit. Two shelter sizes and severe
winter weather also affected the results of some varieties.
Organic Mulches Affect Soil and
Leaf Nutrient Levels of Young Pecan Trees
by Wheeler F. Foshee, III, William D. Goff, Michael G. Patterson, Kenneth
M. Tilt, W. Alfred Dozier, Jr., Laura S. Tucker, and James S. Bannon
Abstract. Soil and leaf nutrient levels were compared from young
pecan (Carya illinoensis [Wangenh.] K. Koch) trees mulched with
leaves, pine bark nuggets, pine straw, grass clippings, or chipped limbs;
and from unmulched trees with bermudagrass sod. Soil beneath grass-clipping
mulch showed an increase in soil potassium (K) levels as compared to all
other treatments except chipped limbs. Foliar iron (Fe) for the pine bark
nuggets and leaf treatments were higher than for the pine-straw and chipped-limb
treatments. Leaf manganese (Mn) levels for the grass-clipping treatment
were higher than those for sod, pine straw, chipped limbs, or leaf treatments.
Overall, the nutritional differences among mulch treatments were small,
suggesting that growth differences were attributed to other factors.
Tree Shade Preferred by Recreational
Users of a Brazilian Beach Sidewalk
by U.C. Malavasi and M.M. Malavasi
Abstract. Barbecuing near the beach is a well-established leisure
activity during weekends and holidays for many people in the state of Rio
de Janeiro, Brazil. A daily nonstimulated census composed of personal interviews
conducted along the beach of Mangaratiba was undertaken during school vacations
in summer (January and February) and winter (July) of 1994 and 1995. A
total of 955 interviews were completed. On average, each group of barbecuers
consisted of 3 adults and 2 children (up to 12 years old). Ninety-five
percent of the barbecues took place on weekends and holidays. The responses
suggested that 85% of the groups prefer to be under shade trees, even during
the winter months. Reasons offered for this preference are temperature
amelioration (80%), privacy (65%), security (45%), and isolation (30%).
On average, a barbecue lasts 6.1 hours.
A Comparison of Landscape Mulches:
Chemical, Allelopathic, and Decomposition Properties
by Mary L. Duryea, R. Jeffery English, and L. Annie Hermansen
Abstract. This study compared chemical, allelopathic, and decomposition
properties of 6 mulches: cypress, eucalyptus, pine bark, pine needle, melaleuca,
and a utility-trimming mulch (GRU). Eucalyptus and GRU mulches had the
highest decomposition after 1 year (21% and 32%), while only 3% to 7 %
of the other mulches decayed. Lignin and lignin:nitrogen ratio were negatively
correlated with decomposition; high values resulted in low decomposition.
Winter respiration of both eucalyptus and GRU mulches was high, and respiration
was positively correlated with decomposition. Pine-straw mulch subsided
from 9 cm (3.5 in.) to 4 cm (1.6 in.) during the year, while the other
mulches subsided approximately 2 cm (0.8 in). Nutrient composition of the
mulches was significantly different, with GRU mulch having the highest
levels of calcium (Ca), magnesium (Mg), nitrogen (N), phosphorus (P), and
potassium (K). Pine straw was the next highest in N and P. Soils under
the mulches were acidified most by pine straw (from a pH of 5.0 to 4.4),
followed by pine bark and cypress. In a standard test of allelopathy, all
fresh mulches inhibited germination of lettuce seed, and although variable
in concentration, all mulches contained hydroxylated aromatic compounds
that could have caused these allelopathic effects. After 9 months and 1
year, pine straw and GRU still exhibited allelopathic effects on germination.
Cypress, melaleuca, and pine bark retained their color after 1 year, while
the other 3 mulches changed to a pinkish gray.
Controlling Invasive Exotics:
A Tallow Tree Replacement Program Campaign in Florida
by Francis E. Putz, Mary Holdnak, and Meg Niederhofer
Abstract. The experiences of a community group in Florida that
sponsored a campaign to curb local expansion of Sapium sebiferum
(tallow tree), an invasive exotic tree, may be useful for other exotic
species control programs. Success of the tallow replacement program was
due, in part, to a partnership formed with the nursery industry. Convincing
the public that not all trees are environmentally beneficial and enlisting
public participation in the campaign were major challenges. Assistance
came in the unexpected form of several vitriolic letters to the editor
of the local newspaper in which the sponsors of the program were condemned
for believing that they had the right to determine the fate of a tree,
even an invasive exotic. The published exchange of letters was beneficial
insofar as it kept the issue of exotics prominently in the public eye.
Using GIS to Assess Urban Tree
Canopy Benefits and Surrounding Greenspace Distributions
by Mark C. Dwyer and Robert W. Miller
Abstract. CITYgreen™, a geographic information system (GIS)-based program, was used to evaluate selected benefits provided by the tree canopy in the city of Stevens Point, Wisconsin. We assessed the distribution of open space in and around the greater Stevens Point area, energy savings from lowered air-conditioning costs, and the reductions in stormwater runoff as a partial function of existing tree canopy. Estimated annual energy savings for residential areas in Stevens Point and surrounding communities was $126,859. A storm delivering 6.6 cm (2.6 in.) of rain in 24 hours will deposit just under 2 billion L (530 million gal) of water on Stevens Point, of which 400 million L (106 million gal) will run off into the Wisconsin River. Approximately 6% of Stevens Point is covered by impervious surfacing, which accounts for 24% of the city's total stormwater runoff volume. Orthophotographs were digitized on screen, and land surrounding Stevens Point was classified based on vegetation cover, land use, and current zoning. Land use in the greater Stevens Point area (22,250 ha [55, 000 ac]) is 20.7% developed, 24.1% agriculture, 46.8% undeveloped, and 8.4% surface water. Planners, managers, elected officials, and other interested parties in land-use planning for the region are using the results of this study for open-space planning.