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• Studies on wood density variations are necessary for estimating the forest carbon pool. Further, they can help predict the
technological properties of wooden end-products. While there have been frequent reports on the relationships between wood
density, cambial age, and ring width, there is little information about the historical trend in wood density for the last
century, particularly in the context of global climate change. 相似文献
993.
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• We present the results of a two-year (2007–2008) greenhouse study investigating the effect of water availability and nitrogen
fertilization on the growth, biomass partitioning, and foliar nutrient content of Abies fraseri (Pursh) Poir. 相似文献
994.
Preparation of silage is a common method to preserve green forage. It plays an important role in improving forage utilization, 相似文献
995.
Adosomus sp.eats the leaves and oviposits on the stems of Artemisia ordosica Krasch.Based on an analytical PTI-GC/MS method, 21 volatile organic compounds (VOCs) from the leaves of A.ordosica were identified.The major operating equipment con-sisted of a DB-5 column (30 m×0.32 mm×0.25 μm) and a flame ionization detector (FID).The amounts of the components from VOCs were determined by a peak area normalization method and 17 VOC components were identified by PTI-GC/MS.The elec-troantennogram (EAG) responses of... 相似文献
996.
The insecticidal activities of the extracts, fractions, and pure compound of Sterculia foetida (L.) seeds were investigated against three major stored product pests, namely, Sitophilus oryzae (L.), Callosobruchus chinensis (L.), and Tribolium castaneum (H.), through contact and fumigation bioassay. Responses varied with test chemicals, insect species, exposure times, and
doses individually. The biologically active constituent of the S. foetida seeds was characterized as a cyclopropene fatty acid structurally elucidated as (2 n-octyl cycloprop-1-enyl)-octanoic acid (I) by spectroscopic analysis. The filter paper application of, (2 n-octyl cycloprop-1-enyl)-octanoic acid (I) at 0.2 mg/cm 2 caused 100% mortality to all test insects 2 days after treatment (2 DAT). Among the chromatographic fractions, only the pure
hexane-eluted fraction caused 100% mortality at 0.3 mg/cm 2 to S. oryzae and C. chinensis 2 DAT, while the dose required to obtain the same percentage of mortality with the crude seed extract was 0.6 mg/cm 2. Under all treatment conditions, T. castaneum exhibited less susceptibility, taking longer than the other insects to show symptoms of toxicity. In terms of fumigant activity,
the compounds appeared to be more effective in a vapor form against all the three insects in closed containers compared with
open containers. These results suggest that the insecticidal activities of the test compounds were attributable to contact
mode of action, although there was also significant fumigant toxicity. The results indicate that the bioactive compound isolated
from S. foetida could act as a potent insecticide against S. oryzae, C. chinensis, and T. castaneum populations. 相似文献
997.
A study was conducted to investigate the effects of skid trail slope and traffic levels on soil disturbances at two soil depths (0–10 and 10–20 cm). The treatments were set at four traffic levels (2, 7, 12 and 20), two slope classes (<20% and >20%) and two soil depths (0–10 and 10–20 cm). Results show that skidder traffic, longitudinal slope and soil depth have significant effect on soil bulk density in skid trail. Comparison of average soil bulk density in different traffic levels shows that there are significant differences in average bulk density between different traffic levels and control ( p<0.05). The average bulk densities in different slopes and soil depths are significantly increased with increase in traffic levels, maximized at 12 passes ( p<0.05), but there are no significant differences between 12 and 20 passes. The interaction effects between traffic and soil depth are significant ( F 0.05,3=0.109, p<0.001). For all traffic treatments, there are significant differences in soil moisture content between the two slope classes and the two depths ( p<0.001). However, the interaction effects between traffic levels and slope classes are not significant ( p >0.05), although skidder traffic and slope affected soil moisture content. 相似文献
998.
A species of the genus Gonoclostera Butler, 1877, G.fangi sp.nov., from Yunnan, China is described in the present paper. Generic diagnosis and list of world species, as well as the photos of adults and genitalia of the new species are also provided. 相似文献
999.
This study examines the strategies and benefits of the taungya farming system to both the government and the rural economy
in Nigeria. An interview survey was conducted in which data were collected from 115 randomly selected farmers in five villages
in the Oluwa forest reserve, Ondo State, Nigeria. The study examines the extent of participation of rural dwellers in plantation
development through taungya farming and the degree of success of this system as an afforestation method. The farmers were
predominantly illiterate, within the age bracket of 35–54 years and with small farm holdings. Twenty nine percent relied totally
on food from the forest reserve for their livelihood, while 71% also had farm holdings in free areas. Land within the reserve
is allocated to farmers free of charge but compensation is paid to landlords on land from free areas. A statistically significant
difference was detected in income from the two sources of farmland for the households and but not in the size of land allocated
under taungya and free areas. About 184 farmers are involved in taungya annually, and 410 ha of Tectonia grandis has been established for the government of Ondo State. 相似文献
1000.
The reed forests that are the subject of this study are scattered over five thanas of the Sunamganj and Sylhet Districts of
the Sylhet Division of Bangladesh. Their total area is 23,590 ha and they have great ecological, economic, commercial and
socio-economic importance due to the diversified resources they supply. However, the forests are commonly encroached on by
local people who are perceived to be seriously depleting the resource. This paper deals with the socio-economic status of
the people residing near these reed forests, and examines their dependency on the resources provided by the reed forests.
A socio-economic survey, participatory rural appraisal and interviews were used to obtain baseline data of the reed forest
resource and the local communities. The study reveals that the communities in the study region have higher income than other
areas of Bangladesh. Most survey respondents have other occupations in addition to farming. The literacy rate is 28.8%. Among
the illiterate, 68% engage in collecting reeds. Although the Forest Department has a management plan for sustainable use of
the reed forests, encroachers receive backing from political leaders and local elites, so their eviction is difficult. In
order to achieve long-term productivity and sustainability from the reed forests, this study recommends a strategy of developing
an integrated joint management plan between the Forest Department and the local people. 相似文献
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