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971.
Georg Avramidis Gunthard Scholz Evelyn Nothnick Holger Militz Wolfgang Viöl Arndt Wolkenhauer 《Wood Science and Technology》2011,45(2):359-368
In this study, the impact of a plasma treatment using dielectric barrier discharge at atmospheric pressure on wax-treated
beech was investigated by surface energy determination and adhesion tests. Measurements of the surface energy revealed a strong
increase in surface polarity along with increased surface energy as a result of the plasma treatment, pointing to increased
adhesion properties. To evaluate the adhesion properties of a polyvinyl acetate (PVAc) adhesive on beech treated with montan
ester wax and synthetic Fischer–Tropsch wax, a special peel test was applied. This peel test provided evidence of increased
adhesion of the PVAc after plasma treatment of both materials investigated. 相似文献
972.
Do multipurpose companion trees affect high value timber trees in a silvopastoral plantation system?
Establishment of native timber trees on deforested land may contribute to the livelihood of farmers, to improved ecosystem
services and to increased greenhouse gas uptake. Here, we present a new silvopastoral planting design to assess species performance
and interspecific competition or facilitation effects among native timber and multipurpose trees in Central America. Two timber
species, Tabebuia rosea and Cedrela odorata, were established in three low-density planting regimes allowing combined tree and future livestock production: (1) solitary
planting, (2) companion planting with Guazuma ulmifolia, and (3) companion planting with the nitrogen-fixing Gliricidia sepium. We quantified survival, growth and reforestation potential of the two timber species subjected to the different planting
regimes for the first 2 years after establishment. Nitrogen concentration as well as stable nitrogen and carbon isotope composition
(δ15N, δ13C) of leaves of the timber saplings were determined. T. rosea showed higher survival and better growth than C. odorata under varying environmental conditions (soil, concomitant vegetation). Performance of the timber saplings was unaffected
by either companion species. Planting regimes had no effect on foliar nitrogen concentration and δ15N of the two timber species, although δ15N values indicated nitrogen fixation activity in G. sepium trees. Planting regimes affected foliar δ13C values in T. rosea. δ13C values were significantly higher in solitarily growing individuals, suggesting lower exposition to water stress conditions
in saplings surrounded by companion species. As we found positively correlated growth traits among timber and multipurpose
trees, a combined planting may benefit farmers by providing additional goods and services. 相似文献
973.
We examined the contribution of rubberwood to the timber export markets of Malaysia and Thailand. In Malaysia, rubberwood
has grown from 26% of total exported wood products in 1998 to 35% in 2007. A high proportion of furniture products (80%) is
rubberwood, whereas the contribution of rubberwood to other wooden products is less than 20%. Only 10% of sawn timber and
logs is rubberwood. In Thailand, rubberwood contributes to around 60% of total exported wood products, arising from a high
share of not only furniture products (70%) but also other wood products (around 50%) and sawn timber and logs, which have
increased in share from 40% in 1998 to 79% in 2007. We conclude that the high proportion of rubberwood products in the wood
export markets of these two countries is a result of: (1) scarcity of raw wood materials because of strict controls on the
logging of natural forests; and (2) governmental support to rubberwood production, including financial support to rubber planters
and technical assistance to downstream timber processors. 相似文献
974.
Faidherbia albida is an ideal agroforestry tree commonly intercropped with annual crops like millet and groundnuts in the dry and densely populated areas of Africa. With its peculiar reverse phenology, it makes growth demands at a different time from that of crops. In addition, it deposits great amount of organic fertilizer on food crops. Leaves entering soils are comparable to fertilization of almost 50 t·ha 1 ·year 1 of manure in dense stands of 50 large trees per ha. These nutrients help maximize agricultural production and reduce the need for a fallow period on poorer soils. Research has shown that millet grown under F. albida yielded 2.5 and 3.4 fold increases in grain and protein, respectively. Animals eat pods which contain mean amounts of crude protein of 20.63% and carbohydrate of 40.1% in seeds. Moreover, the continued existence of F. albida in agroforestry parklands as in Ethiopia and Mali signifies the success of traditional conservation measures. Modern scientists have also developed much interest in the role of agroforestry in maintaining long-term biological balance between agriculture and livestock production systems. To ensure food security, which still remains a major challenge in sub-Saharan Africa, and concurrently minimize environmental degradation, promotion of agroforestry that specifically involves indigenous trees is crucial. We discuss the prospective role of F. albida in alleviating poverty while simultaneously protecting the environment from factors associated with, for example, deforestation and loss of biodiversity. The overall aim is to promote wide-scale adoption of F. albida as a valuable tree crop in farming systems, particularly in those areas where it remains unexploited. 相似文献
975.
The present study was undertaken in five major forest types (dominated by Quercus semecarpifolia, Quercus floribunda, Acer acuminatum, Abies pindrow and Aesculus indica, respectively) between 2400 and 2850 m a.s.l. in a moist temperate forest of the Mandal-Chopta area in the Garhwal region of Uttarakhand, India. The aim was to assess the variation in composition and diversity in different vegetation layers, i.e., herb, shrub and tree, among these five forest types. Diversity indices, such as the Shannon-Wiener diversity index, density, total basal cover, Simpson’s concentration of dominance index, Simpson’s diversity index, Pielou’s equitability, species richness, species heterogeneity and β-diversity, were calculated to understand community structures. Dominance-diversity curves were drawn to ascertain resource apportionment among various species in different forest types. 相似文献
976.
Schizostachyum dullooa (Gamble) Majumder ‘dolu bamboo’ is a thin walled sympodial moderate sized to large tufted bamboo, dominant in the successional fallows of northeast India.
The impact of resource management on productivity and sustainability of the species was evaluated by investigating the population
status and regeneration in Cachar tropical semi evergreen forest under private property resource management (PPRM) and common
property resource management (CPRM) regimes. Population status revealed current-year, one-year, two-year and three-year-old
culms contribute 54%, 24%, 16% and 6% of the total culms per clump, respectively, under PPRM. Three-year-old culms were absent
in CPRM and population status was thus represented by current year (83%), one-year (16%) and two-year (1%) old culms. Net
change, rate of change and % gain in population for different age classes showed the prevalence of management practices under
CPRM was unscientific. Efficiency of new culm production per clump used as an index of regeneration was 69.7% in PPRM and
59.88% in CPRM. New culms produced under CPRM were small and thin. We conclude that CPRM is inappropriate for a long term
economic and ecological sustainability of the species and alternative management protocols are needed for conservation of
the species. 相似文献
977.
Ajaye Babatunde 《林业研究》2011,21(1):111-115
Cement-bonded particleboards of 6 mm in thickness were manufactured using maize stalk (Zea mays) particles of uniform sizes at three levels of board density and additive concentrations respectively. The bending strength and dimensional properties were assessed. Increase in board density and additive concentration caused increase in Modulus of rupture (MOR), Modulus of elasticity (MOE), and decrease in Thickness swelling (TS) and Water absorption (WA). The MOR, MOE and TS of the boards were significantly affected by board density except for WA, but additive concentration affected all the boards’ properties examined at p ≥ 0.05. Strong and dimensional stable cement-bonded boards could be manufactured from maize stalk particles with Portland cement as the binder after hot water treatment. Although the dimensional stability and mechanical strength properties of the boards were affected by the board density and additive concentration, the study revealed that cement-bonded particleboards could be manufactured from maize stalk (Zea mays) particles. However, the increase in board density and additive concentration could cause the increase in MOR and MOE, and cause the decrease in TS and WA of boards. 相似文献
978.
Improvement in seed and seedling quality of Acacia auriculiformis after culling phenotypically inferior trees was studied
in a 6-year old seed production area (SPA). A 5-ha plantation was identified, of which 2.3 ha was converted into SPA. The
initial stocking, 1 612 trees·ha−1, was thinned down to 982 trees·ha−1 based on growth characteristics. The following fruiting season, seeds were collected from 10 randomly selected trees in culled
and non-culled stands, and seed physical characters, germination and seedling traits were assessed. Seed weight, seed thickness
and percentage germination increased by 32.1%, 4.43% and 22.37%, respectively in the culled stand compared to the non-culled
stand. Culling also increased the speed of germination, seedling dry weight and seedling vigor index. Heritability values
were high for seed weight (0.974) and seed thickness (0.948) while medium values were observed for percentage germination
(0.577) and total dry weight (0.534). Predicted genetic gain was 11.13% and 11.22% for seed weight and percentage germination,
respectively. The actual gain was 32.1, 51.9 and 22.9% for seed weight, percentage germination and total dry matter, respectively.
In conclusion, SPAs established by culling inferior trees could serve as sources of good quality seeds for reforestation programs
until genetically improved seeds are made available. 相似文献
979.
A total of 24 candidate plus trees (CPTs) of Pongamia pinnata (L.) Pierre. were selected to elucidate their variation and diversity based on thirteen quantitative traits (4 pod traits,
6 seed traits of parent trees and 3 progeny traits) at Forest Research Centre, Institute of Forest Productivity — Mandar,
Ranchi district during 2005–2007. The results show that, CPT-19 had maximum for seven traits viz, pod length (65.6 mm), 100-pod
weight (542.4 g), seed 2D (two dimension) area (351.2 mm2), seed length (27.9 mm), seed breadth (17.4 mm), 100-seed weight (217.9 g) and plant height (164.3 cm). The traits, 100-pod
weight and 100-seed weight had a high heritability (98.4%, 96.9%) accompanied with high genetic advance (46.0%, 34.9%). There
is a positive significant correlation between 100-pod weight and 100-seed weight traits at both genotypic and phenotypic levels
with plant height, collar diameter and volume index at 30 MAS (months after sowing). Volume index expressed a moderate heritability
(47.4%) accompanied with high genetic advance (48.4%), indicating that the character is governed by additive gene effects.
In divergence study, 24 accessions were grouped into 6 clusters on the basis of non-hierarchical euclidian cluster analysis.
The genotypes in cluster IV (CPT-5, CPT-6, CPT-7, CPT-12, CPT-16, CPT-18, CPT-22) and cluster III (CPT-4, CPT-8, CPT-9, CPT-20,
CPT-21) were most heterogeneous and can be best used within group hybridization. The wide diversity exists between the cluster
V and II, followed by cluster II and I and crosses between CPTs of these clusters may result in substantial segregates. It
is revealed that the existence of substantial variation and diversity can be utilized for genetic resource conservation and
further tree improvement programmers of the species. 相似文献
980.
Nitrogen-fixing activity in decomposing litter of three tree species at a watershed in eastern Japan
Takashi Yamanaka Keizo Hirai Shuhei Aizawa Shuichiro Yoshinaga Masamichi Takahashi 《Journal of Forest Research》2011,16(1):1-7
Nitrogen fixation during litter decomposition was studied for 34 months using litterbags containing newly fallen litter of
coniferous species Cryptomeria japonica and Pinus densiflora and that of deciduous species Quercus serrata. Litterbags were set in contact with the forest floor in a deciduous broad-leaved forest near the top of a slope and in a
C. japonica stand at the middle of the slope at a watershed in eastern Japan. Nitrogen-fixing activity, estimated by acetylene reduction
after 16 and 19 months of incubation, was 62.65–3.86 nmoles C2H4 h−1 g−1 DW in Cryptomeria litter, but only 1.07–0.09 in Pinus and 0.72–0.04 in Quercus. The rate of N increase in decomposing litter was highest in Cryptomeria. Fungal biomass in decomposing litter, estimated by ergosterol content, increased during the initial 16 months of incubation
in Cryptomeria and Quercus, and during the initial 19 months of incubation in Pinus. The litter decomposition rate was highest in Cryptomeria among the three species, due to increased N content and fungal biomass in Cryptomeria litter. Thus, N increase in decomposing Cryptomeria litter affects the subsequent N dynamics and decomposition pattern. 相似文献