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1.
April to October, 1997 comparative studios on the nitrogen budgets of closed shrimp polyculture systems showed that, in all the studied polyculture systems, nitrogen from feeds and fertilizers were the main input items, which comprised 70.7% - 83.9% of the total input nitrogen, 3.2% - 7.4% of which was provided by nitrogen fixation. It was in monoculture enclosures (Y-4, Y-11 and Y-12) that the percentage reached the maximum value. The output nitrogen in harvested products comprised 10.8% - 24.6% of total input nitrogen, and the highest percentage, 24.6%, was found in shrimp-fish-tagelus polyculture systems. In shrimp monoculture and shrimp-fish polyculture systems, they were 19.1% and 21.9%, respectively. The nitrogen utilization efficiency was different and varied from 12.2% to 20.1%. The highest, 20.1%, was found in shrimp-fish-tagelus polycultttre systems, and the average of 20.0% was found in shrimp-tagelus polyculture systems. The lowest, 12.2%, was found in shrimp monoculture systems.All the nitrogen utilization efficiencies in shrimp-fish systems or shrimp-scallop systems seemed to be higher than that of the monoculture system, but they showed little statistical difference. The main outputs of nitrngen were found in sediment mud, and comprised 48.2% -60.8% of the total input, the lowest percentage was found in shrimp-fish-tagelus polyculture systems, and the highost percentage in shrimp-scallop systems.During the experiment, nitrogen lost through denitrification and ammonia volatilization comprised 1.9% - 6.2%, averaged 2.8%, of the total input, and the loss through seepage comprised 5.9% - 8.9% of the total.The estimated nitrogen attached to the enclosure wall comprised 3.7% - 13.3% of the total, and was highest in shrimp monoculture systems. Compared with the classic shrimp farming industry, the closed shrimp polycul-ture systems may improve the nitrogen utilization efficiency, and hence reduce the environmental impacts on coastal waters. The nitrogen discharging rates for all the studied polyculture systems ranged from 3.0% to 6.0% of total input nitrogen. 相似文献
2.
Shrimps( Litopenaeus vannamei) were intensively cultured in a recirculating aquaculture system for 98 days to investigate effects of 0.3 mg/L Cu on its performance, Cu budget, and Cu distribution. Shrimps in Cu-treated systems had greater mean final weight(11.10 vs 10.50 g), body length(107.23 vs 106.42 mm), survival rate(67.80% vs 66.40%), and yield(6.42 vs 5.99 kg/m 3), and lower feed conversion ratio(1.20 vs 1.29) than those in control systems but the differences were not significant. Vibrio numbers remained stable(10 4 –10 6 colony forming units/mL) in the rearing tanks of both control and treated systems. Total ammonium-N, nitrite-N, nitrate-N, pH, chemical oxygen demand, 5-day carbonaceous biochemical oxygen demand, and total suspended solids were similar in controls and treatments. Dissolved Cu concentration in the treated systems decreased from 0.284 to 0.089 mg/L while in the control systems it increased from 0.006 2 to 0.018 mg/L. The main sources of Cu in the treated systems were the artificially added component(75.7% of total input), shrimp feed(21.0%), water(2.06%), and shrimp biomass(1.22%). The major outputs of Cu occurred via the mechanical filter(41.7%), water renewal(15.6%), and draining of the sediment trap(15.1%). The foam fractionator removed only 0.69% of total Cu input. Harvested shrimp biomass accounted for 11.68% of Cu input. The Cu concentration of shrimps in the Cu-treated systems(30.70 mg/kg wet weight) was significantly higher than that in control systems(22.02 mg/kg). Both were below the maximum permissible concentration(50 mg/kg) for Cu in seafood for human consumption in China. Therefore, recirculating systems can be used for commercial on-growing of Litopenaeus vannamei without loss of shrimp quality, even in water polluted by 0.30 mg/L Cu. The mechanical filter is the main route for Cu removal. 相似文献
3.
The East China Sea(ECS) is a river-dominated epicontinental sea, linking the Asian continent to the northwestern Pacific via the large rivers originating from Tibetan Plateau. The relevant huge influx of riverine detritus has developed unique sedimentary systems in the ECS during the Quaternary, offering ideal terrestrial archives for reconstructing Quaternary paleoenvironmental changes and studying land-sea interactions. Overall, two characteristic river systems dominate the sedimentary systems and sediment source to sink transport patterns in the ECS, represented by the Changjiang(Yangtze River) and Huanghe(Yellow River) for the large river system and Taiwan rivers for the small river system. Given this, the sediments derived from both river systems bear distinct features in terms of parent rock lithology, provenance weathering and sediment transport. Previous studies mostly focus on either the ‘source' discrimination or the ‘sink' records of the sedimentary system in the ECS, while the source to sink process linking the land and sea, in particular its time scale, has been poorly understood. Here we introduce a newly-developed dating technique, the ‘comminution age' method, which offers a quantitative constraint on the time scale of sediment transfer from its ultimate source to the final depositional sink. This novel method is of great significance for improving our understanding on the earth surface processes including tectonic-climate driven weathering, and sediment recycling in relation to landscape evolution and marine environmental changes. The application of comminution age method in the ECS will provide important constraints on sediment source-to-sink process and more evidences for the construction of late Quaternary paleoenvironmental changes under these unique sedimentary systems. 相似文献
4.
Defining a universal geodetic coordinate system is one of the fundamental challenges of geodesy. We present a review of the basic general coordinate systems -- the space rectangular coordinate system, the geodetic coordinate system, the topocentric coordinate system, and the plane coordinate system. We then look ： t the World Geodetic System WGS72 and WGS84 and the In- ternational Terrestrial Reference Frames ITRF2000 and 1TRF2005, which were introduced when space technology became avail- able. The history of international geodetic coordinate systems in the Antarctic region is briefly reviewed and the development of the geodetic coordinate systems in the Chinese Great Wall Station and Zhongshan Station in Antarctica is outlined. Finally, the issue of coordinate system transformation is discussed. 相似文献
5.
CHUDongsheng LIUBin LIANGMeng ZHANGLing 《青岛海洋大学学报(英文版)》2002,1(2):206-210
A decentralized parallel one-pass deconvolution algorithm for multisensor systems with multiplicative noises is proposed. Comparing with the conventional deconvolution algorithm, it avoids the computational overload and the high storage requirement. The algorithm is optimal in the sense of lincar minimum-variance. The simulation results illustrate the validity of the proposed algorithm. 相似文献
6.
WANG Dehai KANG Haiping ZHAO Yanwei ZHAO Dalin LV Shicong WU Jianan CHEN Chunguang 《世界地质(英文版)》2013,16(1):35-42
A number of isolated fault sags in Late Jurassic--Early Cretaceous were developed in the early stage of southern Songliao Basin,and unified to a depression basin in the late stage.Therefore,multiple isolated lower petroliferous systems were formed with fault sags as source rocks.The source rocks of fault sags in Late Jurassic--Early Cretaceous were mainly described with gas generation as favorable source rocks,leading to the southern Songliao Basin rich in natural gas resources combined with organic gas resources in Nenjiang Formation.A number of tectonic movements in southern Songliao Basin led to the formation of abundant structural traps and complex fault systems,and controlled the distribution strata and positions of sources rocks in Late Jurassic--Early Cretaceous fault sags.The oil-gas reservoirs can be divided into two types,i.e.,primary and secondary ones.The primary oil-gas reservoirs were distributed in the fault sag strata and the bottom of overlying depression strata(lower Quan-1 Member).The oil-gas reservoir accumulation depended on the trap development situation and the distance from source rocks.The preservation conditions of oil-gas reservoirs depended on the degree of reconstruction in the late tectonism.The secondary oil-gas reservoirs were distribution in the Quantou Formation of depression strata,where oil and gas reservoir accumulation depended on three conditions,i.e.,trap development situation,deep gas sources and the fault to connect the shallow traps and deep gas sources.The southern Songliao Basin is rich in lower coal type gas,upper oil-gas and biogas resources,which are important resources in the future. 相似文献
7.
8.
Symmetrical relationships between humans and their environment have been referred to as an extension of symmetries in the human geographical system and have drawn great attention. This paper explored the symmetry between physical and human systems through fractal analysis of the road and drainage networks in Wuling mountainous area. We found that both the road and drainage networks reflect weak clustering distributions. The evolution of the road network shared a significant self-organizing composition, while the drainage network showed obvious double fraetal characteristics. The geometric fractal dimension of the road network was larger than that of the drainage network. In addition, when assigned a weight relating to hierarchy or length, neither the road network nor drainage network showed a fractal property. These findings indicated that the fractal evolution of the road network shared certain similarities with fractal distribution of the drainage network. The symmetry between the two systems resulted from an interactive process of destroying symmetry at the lower order and reconstructing symmetry at the higher order. The relationships between the fractal dimensions of the rural-urban road network, the drainage network andthe urban system indicated that the development of this area was to achieve the symmetrical isomorphism of physical-human geographical systems. 相似文献
9.
S. C. Choi D. I. Jung C. H. Won J. M. Rim 《中国海洋大学学报(英文版)》2006,5(4):317-321
The authors discovered large differences in the characteristics of overflows by the calculation of 1） intercepting volume of overflows for sewer systems using SWMM model which takes into consideration the runoff and pollutants from rainfalls and 2） the intercepted volume in the total flow at an investigation site. The intercepting rate at the investigation point of CSOs showed higher values than the SSDs. Based on the modeling of the receiving water quality after calculating the intercepting amount of overflows by considering the characteristics of outflows for a proper management of the overflow of sewer systems with rainfalls, it is clear that the BOD decreased by 82.9%-94.0% for the discharge after intercepting a specific amount of flows compared to the discharge from unprocessed overflows. 相似文献
10.
Methodological problems of climatic reconstruction for different periods of Holocene are discussed on the basis of a multiple group biological analysis on peat-sapropel sediments.The possibility of biological analysis is exemplified by the paleoclimatic reconstruction for Carpathian and Altai Mountain ranges.For the "Skolevsky Beskidy" national park of Carpaty the paleoclimatic scenarios have been drown up aiming at the more precise definition of climatic conditions for the period of mass mountain slope terracing.The stability of terrace systems of various designs in the current climatic conditions has been assessed.It is shown that during periods of humid climate the terraces,whose designs have been focused on drainage,were built.In periods of dry and warm climate the terrace systems capable of accumulating water were built.Both these types of terrace systems are destroyed in nowadays.Only those terrace systems are stable which were adjusted by their builders to contrast variations of precipitation.For Western Altais the paleoclimatic scenario has been done to forecast the safety of the Bronze Age kurgans(burial earth mounds) with permafrost inside the construction.In the Altay region during the Holocene it has revealed two periods of sharp cooling,the peaks of which occurred in the intervals 4500-4300 and 2500-2300 years ago,and two periods of pronounced climatic drying 4900-4700 and 130-70 years ago.Depletion of the algae composition in the layer corresponding to the last period of drying climate indicates a very sharp change in the parameters of moisture and turning the lake into a dry swamp.Periods of cold weather may have contributed to the formation of special ritual traditions of the Sakan tribes that require the frozen ground to bury the dead.The later climate fluctuations identified have not affected the safety of permafrost in burial mounds constructed in the V-III cc BC. 相似文献
11.
Linkham Douangsavan Vongpaphane Manivong Anan Polthanee Roengsak Katawatin Yoshio Inoue 《山地科学学报》2006,3(3):247-258
Introduction Traditional agriculture based on indigenous knowledge (IK) has been practiced in many areas for centuries. Such practices are often the basis of very sustainable technologies, which are potentially suitable for developmental programs. Polthanee (2001) reported that such farmer practices have been repeatedly found to be valid, rational and usually suited to the local environmental conditions. Moreover, with increased under- standing of agro-ecosystems, professionals in agricultura… 相似文献
12.
LeQuocDoanh HaDinhTuan 《山地科学学报》2004,1(3):270-275
More than 30 ethnic groups are now living in northern mountainous regions, Vietnam, mainly relying on shifting cultivation with the fallow period being shortened from time to time. Naturally, soil fertility reduces from cycle to cycle, entailing the reduction of productivity. Large areas of moderately sloping lands suitable for upland agriculture have become bare after many cultivation-fallow cycles. The soils there have been severely degraded with more toxicity, low porosity, low water retention capacity and poor floral diversity. Normally, these lands cannot be used for food crop cultivation. So farmers in uplands have to rely on slash-and-burn practices for their livelihood. As there is no more forest with good soil in medium slopes, farmers go to cut forests in watershed, high slope lands and old forests up to the mountains‘ top. There are ecologically and environmentally very sensitive areas, so their destruction will inevitably cause hazardous consequences in the whole basin. Meanwhile,cultivation in these areas has low economic efficiency and sustainability because the crop yield may decrease very fast due to severe erosion as the higher the slope, the more serious erosion. Consequently living standards of highland farmers remain low and unstable. Sustainable farming on these lands in the perspective of a seriously deteriorated ecology and environmental is not an easy task. There have been many projects trying to help mountainous farmers get out of their vicious circle. However, due to different reasons, the results gained are low, and in some cases,things ceased to move after the projects phased out. During past few years, based on the farmer experiences, the Vietnam Agricultural Science Institute has cooperated with local and international partners to implement different projects in order to solve the problems by developing simple, easy and cheap cultivation technologies, which can be accepted and applied by local poor farmers for sustainable agricultural production. The first results of our activities offered good opportunities for sustain food production, improve soil health, recharge of aquifers,and enhanced household income for better rural lively hoods in the upland eco-regions of northern Vietnam. 相似文献
13.
YoichiShimatsu 《山地科学学报》2004,1(2):183-191
Exploring the history of the silk-reeling industry in Chichibu, Japan, this paper challenges the prevalent representation of mountain communities as marginal economic peripheries of the metropolitan center or as reservoirs of poverty and backwardness. Mountain districts were the cradle of an Asian “industrious” revolution that led to Japan‘s modernization. The highland-based silk-reeling producers pioneered an autonomous Asian model of industrial development, which competed successfully against the capital-intensive system introduced from the West into coastal cities. The export strength of silk-producing households in upland villages overturns the claim that Japan‘s economic miracle was based on the introduction of Western technology and administrative systems. To the contrary, the Asian-style management practices and labor standards developed by the silk producers were transferred to a succession of other industries. These indigenous practices account for the rise of Japanese industry in world markets. The clash between the two opposing models of modernization resulted in modern Japan‘s first major civil conflict, the Chichibu Rebellion of 1884, a legacy that has major implications for today‘s recession-mired Japan as well as for developing countries striving for an alternative path to economic development. 相似文献
14.
Rural areas of the Mizoram state, India practice subsistence agriculture where shifting cultivation dominates the farming systems. As a result, output from crops is very low and thus, the rural areas suffer from food insecurity. This paper analyses food security status in the rural areas of Mizoram and suggests the measures to attain food security. A case study of 16 villages, lying in all the eight districts of Mizoram, was conducted in 2014 and1527 households(76%) out of total 2010 households were surveyed through purposive random sampling method. Structured questionnaire was constructed and questions on three food security components and13 indicators were asked. We used Z score technique to calculate data and finally got a composite score of all the components of food security. Our result shows that food availability in the study villages is very less as composite score stands for 0.003 whereas food accessibility is comparatively higher, mainly due to availability of fair price shops(mean value is one),high agricultural working population(40.1%) and high literacy rate(70.6%). Therefore, its composite score is 0.236. Food stability scores only-0.062 and finally overall food security stands for 0.178, which is inadequate. We have suggested that ‘system rice intensification', which is already in practice, should be given priority. Adequate irrigation facilities, proper public distribution system, cultivation of fruits and vegetables, value addition in farm products and access to market may achieve food security. 相似文献
15.
Traditional farming practices conform to sustainable rural livelihoods, while agricultural modernisation tends to undermine
these practices through various perturbations. A case study in Tengchong County (western Yunnan, China) shows that transformation
of traditional alder (Alnus nepalensis) and dry rice (upland rice) rotational farming to introduced Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantations leads to localised water scarcity and soil fertility decline. While farmers are aware of ecological
sustainability of traditional farming, they prefer Chinese fir forestry because it is less labour-intensive, has a high market
value, and releases time for profitable off-farm work. Farmers adapt to economic liberalization by planting high value crops
and trees. However, alternatives to make local agricultural production more profitable through competitive business strategies,
cooperative approaches, innovations in integrating high value crops and ‘downstream’ processing for sustainable rural livelihoods
have been overlooked largely due to poor information availability and lack of organisational framework. 相似文献
16.
Khaled Misbahuzzaman 《山地科学学报》2016,13(8):1489-1502
Shifting cultivation is a traditional farming system practiced in the tropical mountainous areas. Although it has been widely perceived as an economically inefficient and environmentally harmful agricultural production system, recent science reviews, however, indicate that the deleterious impacts of shifting cultivation on environment may have been overestimated. Despite the pressures of agricultural intensification in areas where shifting cultivation occurs, farmers across the tropics still maintain this traditional farming system. The objective of this study was to explore existing traditional shifting cultivation practices and their various modifications including the innovative farming techniques developed by farmers in the Chittagong Hill Tracts (CHTs), the mountainous region of Bangladesh, and examine their importance with respect to recent socio-economic and environmental changes. The study revealed that shifting cultivation still exists as the most dominant farming method which supports livelihoods and culture of the hill ethnic people. However, demand for more food and household income to meet livelihood needs of an increasing population combined with a rapid deterioration of soil and water quality over decades contributed to development of innovative farming practices through fallow land farming, crop substitution, agroforestry and homestead gardening in the CHTs. Through these farming techniques farmers maintain a strong relationship with traditional knowledge system embedded in the age-old shifting cultivation practices. Today state policies and market forces act in favor of replacement of traditional farming with intensive cash crop agriculture. It seems that disappearance of traditional farming practices from the hills may threaten local biodiversity and food security. It may be recommended that shifting cultivation should be encouraged in areas where they have potential for contributing to preservation of native biodiversity and ecosystem services, and protection of local peoples’ food security and cultural identity. 相似文献
17.
Ripu M. KUNWAR Laxmi MAHAT Lila N. SHARMA Keshab P. SHRESTHA Hiroo KOMINEE Rainer W. BUSSMANN 《山地科学学报》2012,9(5):589-600
Underutilized plant species help to alleviate common food insufficiencies by providing alternative food supply. They also complement primary health care, furnishing raw materials where the cultivation of staple cereal crops is least feasible and health care is pursued indigenously. Research and promotion of extraction, utilization, and conservation of underutilized species lead to exploration of new staple crops and motivate people to consume in a sustainable manner. The present study describes the current status, uses, and management of underutilized plant species in Far West Nepal. The relative importance of 49 underutilized plant species was computed employing a Relative Importance (RI) technique. The use-values assigned to the species fall into six use-categories: beverage, fodder, food & edible, medicinal, vegetable and veterinary. A total of 22 species appeared in multiple use-categories, while the rest were characterized by a single use-category. Based on relative importance and frequency, Ficus semicordata, Debregesia longifolia, Girardinea diversifolia, Hydrocotyle nepalensis, Garuga pinnata, Aloe vera and Pyrus pashia offer the most potential for future. Underutilized plants proved important to folk medicine and food. These species persist because they remain useful to local people as means of subsistence, production, and primary health care. The findings are important so far as they point up the role of underutilized plants in national food security policy and health care, spelling out their potentialities and cross cutting relationships. 相似文献
18.
Spatio-temporal patterns of intra-urban land use change in Beijing, China between 1984 and 2008 总被引：1，自引：1，他引：0
Wenhui Kuang 《中国地理科学(英文版)》2012,22(2):210-220
Urban internal structure is essential information for urban geography researchers and urban planners or managers. This research aims to examine the spatial structure changes of internal urban land use based on the interpreted datasets of 1984 and 2008. Spatio-temporal patterns of internal land use conversion and urban expansion are analyzed, and then dominant driving factors (e.g., social economy, population growth and urban planning) were identified. The results indicate that Beijing′s intra-urban layout has experienced tremendous adjustment from compact to disperse configure, otherwise its function objects have shifted from the major economic and industrial development before the 1990s to the combination with cultural, high-technological and inhabitable city at present. The dominant urban land use transformations include the relocation of industrial lands from core districts to suburban or other provinces, and the accelerating expansion of residential areas and green spaces for supplying the demand of housing and ecological protection. Although Beijing′s urban planning has experienced three major adjustments and improvement since the 1980s, its optimization of urban internal patterns still remains a challenge. 相似文献
19.
In this report, complete mitochondrial genome sequences of Laminaria cultivation variety ‘Rongfu’ were obtained. The results showed the length of circular molecule of mtDNA was 37 638 bp (64.7%
A+T), encoding three rRNAs (23S, 16S and 5S), 25 tRNAs, 35 known mitochondrial proteins and 3 ORFs. Sequence alignment indicated
its mtDNA genome was very similar to that of Laminaria japonica. Phylogenetic trees inferred from concatenated 30 mitochondrial genes showed that ‘Rongfu’, Laminaria japonica, Laminaria longipedalis, Laminaria diabolica, Laminaria religiosa and Laminaria ochotensis clustered together. In addition, compared with mitochondrial genome of L. japonica, ‘Rongfu’ mtDNA lacked a non-coding region of 19 nucleotides, which was located between rRNA small subunit gene 3 (rps3) and rRNA small subunit gene 9 (rps9). Seven cultivation varieties of China were divided into two groups based on this non-coding region which was absent in
‘Rongfu’, ‘Fujian’ and ‘Sanhai’ while present in ‘Ailunwan’, ‘Dongfang No.2’, ‘Dongfang No.3’ and ‘Zaohoucheng’. So this variation
can be used in germplasm identification of cultivation variety. 相似文献
20.
Comprehending regional characteristics and influencing factors of China’s inbound tourism economy is important to make effective
policies that will help inbound tourism develop harmoniously and shrink regional disparity. This paper studied the regional
disparity and convergence of China’s inbound tourism economy during 1996–2008 with the methods of σ-convergence, club convergence and β-convergence. The results indicate that 1) inbound tourism receipts per capita (ITRPC) of the whole country, the eastern,
central and western regions presented the rapid increasing trend; 2) ITRPC of the whole country was characterized by convergence;
3) the eastern region presented club convergence, but the central and western regions did not show this trend; 4) the star-hotel
levels and investment in fixed assets for the tourism industry per capita had a same trend to growth rates of ITRPC, promoting
inbound tourism development, and there was no difference among the 31 provinces (municipalities) in the mainland of China;
5) but the proportion of employed persons in the tourism industry accounting for total population and the proportion of the
tertiary industry accounting for GDP had a reversal trend to growth rates of ITRPC, shrinking the provincial disparity in
inbound tourism economy, and there were differences between the developed provinces and the developing provinces. Based on
these analyses, we put forward some suggestions for the developing provinces to speed up inbound tourism economy. 相似文献