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31.
Accumulation of Fluoride and Aluminium Related to Different Varieties of Tea Plant 总被引:12,自引:0,他引:12
Samples of young shoot, mature leaf, twig, root, and litter were taken from four recently bred varieties Zhe-nong 113, Zhe-nong 121, Zi-sun, and Bi-feng grown at two tea plantations located at Zhejiang and Jiangsu Provinces. The results showed that the concentrations of F and Al in tea plants were significantly different among the four varieties. It is therefore possible that F and Al concentrations in tea products can be reduced through variety selection. The results also revealed that old leaves would be the major contribution to the high levels of F and Al in brick tea since it is produced mainly for old leaves. Therefore, in order to eliminate the hazard of over-exposure to F and Al derived from tea, younger shoot should be used for making tea products while mature leaves should be avoided. 相似文献
32.
杨树刺槐混交林沙地土壤的水分—物理性质 总被引:24,自引:0,他引:24
研究了刺槐与杨树混交林后沙地土壤水分-物理性质变化的状况,结果表明,刺槐与杨树混交后,土壤水分-物理性质得到了改善,表现在土壤最大持水量增加,毛管持水量、田间持水量得以提高,土壤有效持水量也有了较大幅度的提高,刺槐与杨树混交后土壤总孔隙度、非毛管孔隙度、毛管孔隙度得到提高,并由此而改善了混交林土壤的渗透性能,表4参7 相似文献
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34.
Fuelwood plays an important role in the rural economy of the developing countries of Asia and Africa. Optimizing energy fixation
in forest trees through high density energy plantations (HDEP), gasification of wood, and conversion of forest tree biomass,
are some of the potential areas whereby additional research and development input for efficient management of atmospheric
carbon in our energy system can be incorporated. For example, the photosynthetic efficiency of forest trees is rarely above
0.5%, which on the basis of theoretical considerations can be increased by up to 6.6%. Thus there is an ample scope to improve
the efficiency up to 1%, which amounts to doubling of the productivity of the forests.
Recent policy changes and experiences with wood-based bio-energy programmes in several countries indicate that woodfuels may
become increasingly attractive as industrial energy sources. Use of biodiesel and the formulation of a project for undertaking
13.4 million ha of Jatropha plantations in India highlight the seriousness with which the Government of India is promoting carbon neutral energy plantations.
The cost of establishment of plantations primarily for fuel production and its conversion to energy are major deterrents in
this pursuit. Some of the issues in developing countries, like low productivity on marginal lands, degraded forest lands,
and unorganized units for biomass energy conversion, result in cost escalation as compared to other energy sources. This paper
revisits the scope for raising energy plantations, a comparison of the direct and indirect mitigation potential uses of plantations
as an adaptation strategy through reforestation and afforestation projects for climate change mitigation and socio-economic
issues to make this venture feasible in developing countries. 相似文献
35.
桉树人工林生态系统养分循环和平衡研究Ⅱ. 桉树人工林生态系统的养分循环 总被引:1,自引:4,他引:1
根据大量的观测分析资料,论述了刚果W5桉树人工林生态系统养分的地球化学循环和生物小循环。研究结果表明,每公顷每年通过地表径流和地下渗漏从生态系统输出的养分质量以K最多,达21.25 kg/(hm2a);其次为N,达17.21 kg/(hm2a)。桉树人工林生态系统养分流通质量的净变化值f(K)、f(Ca)为负值,f(N)、f(P)、f(Mg)为正值;桉树人工林生态系统养分的生物小循环研究表明,在一个轮伐期内,每公顷桉树吸收养分的质量,依次为Ca 429.03 kg/hm2,其次为N 277.01 kg/hm2和K 208.12 kg/hm2。而在一个轮伐期中归还的养分质量,Ca只有99.78 kg/hm2,K为113.04 kg/hm2。在养分循环率方面,与热带半落叶季雨林比较,桉树人工林生态系统的养分循环率要小得多,说明桉树人工林土壤养分趋向于减少。 相似文献
36.
Kuhn A Ballach HJ Wittig R 《Environmental science and pollution research international》2004,11(1):22-32
Cuttings of Populus nigra L. cv. Loenen were cultivated in sand treated with one of the following PAHs: phenanthrene (Phen), fluoranthene (Flt), pyrene (Pyr), chrysene (Chr) and benzo[a]pyrene (BaP). The PAHs were applied at varying levels of concentration to each test series. After 6 weeks the concentration and the distribution of the PAHs in the substrate of the various sets of tests were compared with the concentration in the substrate of the control. Additionally the substrate and the plant roots were tested for evidence of degradation products of PAHs. The results revealed that the levels of concentration of Phen and Pyr detected in the substrate surrounding the roots was in some cases significantly lower than in the corresponding section of substrate in the unplanted set (= control). This phenomenon did not occur for Flt and BaP and in the case of Chr only in those substrates, which had been treated with the highest levels of concentration. As the presence of lesser amounts of Phen and Pyr in the plant pots cannot only be attributed to their accumulation and metabolism in the roots, it is fair to assume that the chemical transformation of these three PAHs took place outside the roots. The set of tests treated with Phen revealed the presence of 2- or 3-hydroxy-Phen (main components), a hydroxy-methoxy-Phen, 9,10-Phenanthrenequinone and one unidentified compound in metabolite form. Altogether eleven metabolites of Pyr were identified in the root extracts, which can be divided into three groups: 1-Hydroxy-Pyr and derivatives, dihydroxy-Pyr and derivatives and ring fission products (4-Hydroxy-Pyr and a derivative of the 4-Phen-carbonic acid). However, the metabolite mass detected for Phen and Pyr represents only an insignificant percentage in comparison with the lesser amounts of PAHs observed in the planted set of tests. This indicates that the three PAHs were reduced to lower molecular compounds, which are methodically impossible to record, and subsequently translocated to other parts of the plant and integrated into the biomass. Although no lesser amount for Flt and BaP was found in the plant pots, 1-Hydroxy-Flt, an unidentified compound of Flt and 1-Methoxy-BaP were detected. These are presumably end products which were enhanced in the roots. It was not possible to identify any transformation products of Chr. It can be assumed that the majority of metabolites were not synthesised in the roots but are a result of microbial degradation in the rhizosphere. The test plants improved the conditions for the biotransformation of Phen and Pyr significantly and accumulated Flt, Pyr, Chr and BaP in their roots. It can therefore be concluded that the use of plants in the bioremediation of contaminated soils is a promising option. 相似文献
37.
Woodlands of the Mediterranean speciesJuniperus oxycedrus ssp.macrocarpa (maritime juniper) are both vulnerable and ecologically important. Their ecology and biological status along the SW coast
of Spain are not well known; this, the first major study of these juniper populations is a basis for future research and restoration
policies. These communities are subject to harsh conditions, the plant composition being controlled by several factors at
different scales. On a large scale, climate and soil texture play an important role in controlling the soil water availability
to plants, and in separating xerophytic from mesic communities. On a small scale, coastal physiography, and substrate composition
are related to differences in the floristic composition. Coastal plantations modify environmental conditions, such as sand
mobility and salt spray deposition, inducing important changes in plant communities. The population of maritime juniper on
this coast was estimated in ca. 25 000 individuals, of which 93.6% are concentrated in three locations. Large proportions
of young individuals were found in extensive and protected populations. Howerver, adult individuals dominated the smaller
populations located under pine plantations. This limitation of recruitment may be imposed by several factors. A male biased
ratio was detected on the southern coast of Cádiz, which I hypothesize is due to the lower cost of pollen production in a
stressful habitat. Preservation of suitable habitats, the recovery of abandoned pine plantations, and the connection between
juniper populations, seem to be important requisites for the conservation of maritime juniper in the southwestern coast of
Spain. 相似文献
38.
我国桉树人工林立地土壤问题研究概况 总被引:17,自引:0,他引:17
我国引种桉树。虽已100多年,但研究桉树人工林土壤问题,却只有50多年的历史。这方面的研究,包括桉树人工林土壤本底调查、土壤性质与林木生长的关系、桉树人工林土壤肥力衰退防治、桉树人工林土壤管理、桉树速生丰产的土壤肥力指标、桉树人工林生态系统土壤养分和水分循环等。文章对这方面研究的概况作了简要的综述。 相似文献
39.
40.
Jackson WA Martino L Hirsh S Wrobel J Pardue JH 《Environmental monitoring and assessment》2005,107(1-3):155-171
A cylindrical dialysis sampler (1.2 m in length; 5 cm in diameter) was designed and constructed to sample small–scale phytoremediation processes in the root zone of poplar trees. The study site was a 183–tree plantation of hybrid poplars located at Aberdeen Proving Ground, Maryland, at the J–Field Area of Concern. The grove was planted in 1996 to intercept a chlorinated solvent plume containing 1,1,2,2–tetrachloroethane (1,1,2,2–TeCA, trichloroethene (TCE) and daughter products. Two dialysis samplers were installed: one directly in the poplar grove (approximately 0.3 m from the trunk of a mature tree) and the other outside of the grove but in the plume. Data collected included concentrations of chlorinated VOCs, organic acids, chloroacetic acids, Cl−, and dissolved gases (ethane, ethene, CH4, CO2). At the control location, the VOC profile was dominated by cis– 1,2–dichloroethene (cis–1,2–DCE) and trans–1,2–dichloroethene (trans–1,2–DCE) with concentrations ranging from 0.88-4.5 to 4.4-17.6 mg/L, respectively. Concentrations of VOCs were similar across the vertical profile. At the tree location, 1,1,2,2–TeCA and TCE were the dominant VOCs detected but as opposed to the control location were highly variable within the root zone, with the greatest variability associated with locations in the sampler where roots were observed. This highly variable profile at the tree location is indicative of VOC rhizosphere biodegradation and uptake near the active roots. This variability appears to be on the centimeter scale, emphasizing the importance of these high–resolution samplers for the study of rhizosphere influences. 相似文献