Environmental Engineering Reference
In-Depth Information
thermal conductivity of
Paulownia wood is very low, thus giving it excellent heat/cool insulation
properties. Further, it has an ignition temperature of 420-430°C, as compared with the average
hardwood of 220-225°C.
P. tomentosa
has excellent flame retardancy, and it was found that
Paulownia wood contains less lignins in comparison to cedar wood (Li and Oda 2007). Paulownia
wood generates very little combustible gas when heated. Because of this property, it has been used
to make clothing wardrobes for decades in Japan. In other studies conducted to evaluate
P. elongata
as the raw material for paper production, it was revealed that pulp obtained from Paulownia is not
of the highest quality but can be readily used for paper production when mixed with long fibrous
material (Ates et al. 2008).
27.3.4 d
iSEaSES
of
p
aulownia
The main diseases that damage the Paulownia at seedling stage are caused by
Gloeosporium
kawkamii
and
Spliacelorna paulowniae,
which attack the juvenile leaves and shoots. No major
insect pests are known for royal Paulownia in the United States. Minor damage from several
foliage diseases has been reported on the species. Two powdery mildew-causing fungal species,
Phyllactinia guttata
and
Uncinula clintonii
,
and
another fungal species caused by
Phyllosticta
paulowniae
producing small brown spots on the leaves have also been reported (Hepting 1971). No
major disease problems have appeared yet in the United States.
Paulownia witch's broom (PWB) is a serious disease affecting Paulownia production. The
disease incidence rate of Paulownia at 5 years old was approximately 50-80%, which could reduce
25% of timber production. Primers based on the P1-like adhesion gene sequence of
Mycoplasma
pneumoniae
have been successfully used to detect this disease (Zhong and Hiruki 1994). If PWB
disease is found, the host seedlings should be immediately removed.
27.4 develoPment oF hIGh-yIeldInG PauloWnIa Farms
On the basis of investigation, within 10 years a well-managed Paulownia plantation can attain a
mean height of approximately 16-20 m, a mean diameter at breast height (DBH) of 35-40 cm,
and a standing volume of 0.5 m
3
. However, a species should be chosen depending on the growth
characteristics and ecological requirements for planting on specific site conditions. The qualified
planting stock for a high-yielding plantation should be 4 m in height and 6 cm in DBH. A well-
managed 4-year-old
P. elongata
farm near Lenox, GA that was established for lumber is shown in
the Figure 27.1b. Following the guidelines carefully and attending the needs of the growing plants,
15- to 16-ft-tall
P. elongata
trees can be easily obtained in the first season of growth within 4-5
months (Figure 27.1c). Whatever type of planting models is adopted, the intercropping of crops or
other shade-enduring economic plants are always beneficial.
Paulownia lumber farming is an environmentally sound alternative to expensive, lightweight
hardwoods grown in jungles and rain forests—thriving on marginal or even toxic land
(Bergmann et al. 1997). Paulownia roots penetrate down as far as 40 ft, regulating the water
table and removing soil salinity. Paulownia trees have been shown to be very effective in
absorbing waste pollutants from hog, chicken, and dairy facilities as well as various other
pollutants (Bergmann et al. 1997). Paulownia saves forests by producing sawn timber in 6-8
years and growing 2-4 times more lumber than most other commercial trees in the same time
period [World Paulownia Institute (WPI) personal communication]. This is vital because the
supply of exotic hardwoods rapidly diminishes. After harvesting, a new Paulownia tree grows
back from the stump and uses the same well-established root system (Figure 27.1d,e). This
saves postharvest clearing costs, land erosion, and runoff. A recently established 6-week-old
P. elongata
demonstration farm (spacing 12 × 12 ft) at the Fort Valley State University is shown
in Figure 27.1k.
