Spatial Disparity of Slope Farmland and Food Security in Three Gorges Area

As an important measure of ecoenvironmental construction, the process of de-farming in slope farmland is being undertaken gradually in the whole China. Meanwhile, the problem of reducing in food yield in de-farming areas can not be neglected any more. It is especially the case in areas with concentrated slope farmland and inconvenient transportation. In this paper, we analyze the causes of hidden troubles in food security, and the spatial relationship between farmland and slope farmland in the reservoir area of Three Gorges, and unveil the spatial disparity of contradictions between food supply and demand. Finally, combining the accessibility of areas, three different spatial types of food security, food security area, food alert area, and food crisis area, are divided.     

Influential Factors in Employment Location Selection Based on “Push-Pull” Migration Theory—A Case Study in Three Gorges Reservoir Area in China

In China, farmers employed in non-farm work have become important socio-economic actors, but few studies have examined the farmers' perspective in making their work location choices. Based on "push-pull" migration theory, this paper utilizes sectional data from a 2013 survey of farmers in China's Three Gorges Reservoir area to empirically analyze the factors influencing migrant workers' choice of employment location. The results indicate that 60.46% of laborers have migrated from their home province, whereas 39.54% have remained in their home province. Focusing on personal, household, and community characteristics—in addition to the economic characteristics of the sample counties—multinomial logistic regression models reveal that farmer-laborers' employment location decisions are influenced by their personal capital endowment(age, years of education and social networks), family structure(the number of laborers, elders, children and students), home village characteristics(location, economic development level and the degree of relief of the land) and home county economic development level. Notably, male and female laborers' location decisions reveal a converging trend, and their differences are not pronounced. Per capita arable land area has little influence on location decisions, whereas the educational level of laborers has a significant impact. The results differ significantly from those found in previous studies.     

Micromorphology of landslide soil——Case study on the Jibazi landslide in Yunyang in the Three Gorges Region, China

Introduction The studies on landslides in the Three Gorges Region were conducted, e.g., those on affecting factors and forming mechanism of landslide (YIN Kunlong et al. 1998, DENG Qinglu et al. 2000, CHEN Yongbo et al. 2003, XU Qiang et al. 2003), on ris…     

Coastal eutrophication, land use changes and Ceratium furca (Dinophyceae) blooms in Pago Pago Harbor, American Samoa 2007�C2009

The bloom forming dinoflagellate, Ceratium furca, has been linked with coastal eutrophication worldwide in tropical and subtropical locations. During the summer of 2007, an unusual 6-month long bloom of C. furca was observed in Pago Pago Harbor, Tutuila Island, American Samoa. Incidents of dinoflagellate blooms in this area have not been previously reported. The bloom was first reported in May and dissipated in November 2007. In February?CMarch 2009, a similar C. furca bloom was observed. During both blooms, no fish mortality events were reported. Maximum cell counts were observed on September 20, 2007 at 9 200 cell/mL. At this time, total nitrogen was measured at 1.2 mg/L while total phosphate was below detection limits. Changes in land use practices may have been the primary driver of these blooms. Intense fertilization of athletic fields coupled with ineffective management strategies is hypothesized to have a direct link to the increase in nutrients found in the Pago Pago Harbor and may have been the trigger for the initialization of these blooms. During 2008, the fields were not used due to an infestation of the fire ant, Solenopsis geminata. Once controlled, the fields were opened again in 2009 and fertilizers were applied in January, a month before the bloom was observed.     

Statistical analysis of tropical disturbances over the South China Sea during 1997�C2006

Tropical disturbances over the South China Sea (SCS) during the period of 1997-2006 are analyzed using the Tropical Storm and Hurricane WX products. A total of 158 tropical disturbances were formed over the SCS from 1997 to 2006, with 54 de-veloping tropical disturbances which developed into tropical depressions and 104 non-developing tropical disturbances which never developed into tropical depressions. The development rate of tropical disturbances into tropical depressions was 34.18% in these ten years. During the period of this study, total annual numbers of tropical disturbances and developing tropical disturbances over the SCS had significant decreasing trends; however, the development rate of tropical disturbances had an insignificant increasing trend.     

Filling of the Three Gorges Reservoir to the 135-m Level： Instant Effects on the Yangtze Discharge and Suspended Sediment Concentration Entering the Estuary

Via the valuable opportunity of the Three Gorges Reservoir (TGR) 135-m filling in June 2003, the Yangtze discharge and suspended sediment concentration (SSC) entering the estuary during the period from 15 May to 15 July 2003 were analyzed to examine the instant effects of the filling on them. The Yangtze discharge and SSC entering the estuary in the periods before, during and after the filling clearly indicated three phases: 1) the pre-storage phase characterized by natural conditions, in which the SSC incr...     

Livelihood strategy change and land use change —Case of Danzam Village in upper Dadu River watershed, Tibetan Plateau of China

Land use change in rural China since the 1980s, induced by institution reforms, urbanization, industrialization and population increase, has received more attention. However, case studies on how institution reforms affect farmers’ livelihood strategies and drive land use change are scarce. By means of cropland plots investigations and interviews with farmers, this study examines livelihood strategy change and land use change in Danzam Village of Jinchuan County in the upper Dadu River watershed, eastern Tibetan Plateau, China. The results show that, during the collective system period, as surplus labor forces could not be transferred to the secondary and tertiary industries, they had to choose agricultural involution as their livelihood strategy, then the farmers had to produce more grains by land reclamation, increasing multiple cropping index, improving input of labor, fertilizer, pesticide and adopting advanced agricultural techniques. During the household responsibility system period, as labors being transferred to the secondary and tertiary industries, farmers chose livelihood diversification strategy. Therefore, labor input to grain planting was greatly reduced, which drove the transformation of grain to horticulture, vegetable or wasteland and decrease of multiple cropping index. This study provides a new insight into understanding linkages among institution reforms, livelihood strategy of smallholders and land use change in rural China. Foundation item: Under the auspices of National Natural Science Foundation of China (No. 40601006, 40471009), National Basic Research Program of China (No. 2005CB422006)     

Size-fractionated phytoplankton biomass in autumn of the Changjiang （Yangtze） River Estuary and its adjacent waters after the Three Gorges Dam construction

A cruise was undertaken from 3rd to 8th November 2004 in Changjiang （Yangtze） River Estuary and its adjacent waters to investigate the spatial biomass distribution and size composition of phytoplankton. Chlorophyll-a （Chl-a） concentration ranged 0.42-1.17 μg L^-1 and 0.41-10.43 μg L^-1 inside and outside the river mouth, with the mean value 0.73 μg L^-1 and 1.86 μg L^-1, respectively. Compared with the Chl-a concentration in summer of 2004, the mean value was much lower inside, and a little higher outside the river mouth. The maximal Chl-a was 10.43 μg L^-1 at station 18 （122.67°E, 31.25°N）, and the region of high Chl-a concentration was observed in the central survey area between 122.5°E and 123.0°E. In the stations located east of 122.5°E, Chl-a concentration was generally high in the upper layers above 5 m due to water stratification. In the survey area, the average Chl-a in sizes of 〉20 μm and 〈20 μm was 0.28 μg L^-1 and 1.40 μg L^-1, respectively. High Chl-a concentration of 〈20 μm size-fraction indicated that the nanophytoplankton and picophytoplankton contributed the most to the biomass of phytoplankton. Skeletonema costatum, Prorocentrum micans and Scrippsiella trochoidea were the dominant species in surface water. The spatial distribution of cell abundance of phytoplankton was patchy and did not agree well with that of Chl-a, as the cell abundance could not distinguish the differences in shape and size of phytoplankton cells. Nitrate and silicate behaved conservatively, but the former could probably be the limitation factor to algal biomass at offshore stations. The distribution of phosphate scattered considerably, and its relation to the phytoplankton biomass was complicated.     

Deep Processes of Basin Evolution:A Case Study of the Southern Songliao Basin and Adjacent Area,NE China in Mesozoic-Cenozoic

1IntroductionOne of the key factors related to basin geody-namics is deep process controlling formation and evolution of sedimentary basin. Depth and tempera-ture of asthenosphere,existence of mantle plume,occurrence of mantle melting,and amounts of melts under depressurization during thinning of lithosphere are controlling factors influenced formation and characteristics of extensional basin directly (Li,1994). Rifting is probably governed by frictional forces exerted on the base of litho…     

Spatiotemporal distribution of fish eggs and larvae in the Huanghe(Yellow) River estuary,China in 2005–2016

Decreasing fish resources in estuaries is a subject of anthropogenic activities.Studies of the spatiotemporal distribution of fish eggs and larvae can help identify the status and processes underlying recruitment in a fishery.As the fifth largest river estuary in the world,the Huanghe(Yellow)River estuary(HRE)is a typical estuary that has been seriously affected by human activities.Annual surveys on ichthyoplankton and environmental factors were conducted in the months of May of 2005 and 2009-2016 in the HRE to investigate the spatiotemporal distribution of fish eggs and larvae and the associated influencing factors.A total of 23 and 20 species of eggs and larvae,respectively,were collected.The dominant orders were Perciformes(51.2%)and Clupeiformes(25.6%).The average number of fish species eggs and larvae were 6.0 and 4.1 in average abundance of 0.91 and 0.13 ind./m~3,respectively.The dominant species were mainly low-commercial-value small-sized fishes,such as Clupanodon punctatus,Hare,ngula zutnasi,and Acanthogobius,whereas certain traditional commercial fishes,such as Trichiurus lepturus,and Clupea pallasii,were not seen.Analysis of the fish egg and larval community revealed four temporal assemblages and two spatial assemblages.Salinity was the main factor on the spatial distribution of ichthyoplankton communities,the species number and Shannon-Weiner diversity index(H')of the fish egg and larval community near the river mouth with lower salinity were significantly lower than the community far away from the river mouth with higher salinity.In addition,increases of water temperature promoted the number and abundance of fish species eggs,and the areas of abundant prey tended to have a more diversified and abundant of ichthyoplankton species.In overall,overfishing,dam construction,and other human activities were the main drivers that led to the substantial decline in fishery resources in the HRE.     

Zooplankton community structure,abundance and biovolume in Jiaozhou Bay and the adjacent coastal Yellow Sea during summers of 2005–2012: relationships with increasing water temperature

Zooplankton abundance, biovolume and taxonomic composition in Jiaozhou Bay and the adjacent coastal Yellow Sea were evaluated using ZooScan measurement of samples collected by net towing every August from 2005 to 2012. Zooplankton abundance and biovolume ranged from 1 938.5 to 24 800 ind./m~3 and 70.8 to 1 480.1 mm~3/m~3 in Jiaozhou Bay and 73.1 to 16 814.3 ind./m~3 and 19.6 to 640.7 mm~3/m~3 in the coastal Yellow Sea. Copepods were the most abundant group in both regions, followed by N octiluca scintillans and appendicularians in Jiaohzou Bay, and chaetognaths and N octiluca scintillans in adjacent coastal Yellow Sea. Over the study period, the most conspicuous hydrographic change was an increase in water temperature. Meanwhile, a general decrease in zooplankton abundance was observed, particularly in copepod populations. Based on redundancy analysis(RDA), the warming trend was the key environmental factor influencing to decrease of copepod abundance. The proportion of small-sized copepods increased while the mean size of all copepods decreased, in significant correlation with water temperature. Our results indicate that zooplankton, particularly copepods, are highly sensitive to change in water temperature, which is consistent with predicted impacts of warming on aquatic ectotherms. Due to their dominance in the zooplankton, the decline in copepod size and abundance could lead to an unfavourable decrease in energy availability for predators, particularly planktivorous fish.     

Altitudinal trends in δ~(13)C value,stomatal density and nitrogen content of Pinus tabuliformis needles on the southern slope of the middle Qinling Mountains,China

In this study,a coniferous tree species(Pinus tabuliformis Carr.) was investigated at a moderate-altitude mountainous terrain on the southern slope of the middle Qinling Mountains(QLM) to detect the trends in carbon isotope ratio( δ~(13)C),leaf nitrogen content(LNC) and stomatal density(SD) with altitude variation in northsubtropical humid mountain climate zone of China.The results showed that LNC and SD both significantly increased linearly along the altitudinal gradient ranging from 1000 to 2200 m,whereas leafδ~(13)C exhibited a significantly negative correlation with the altitude.Such a correlation pattern differs obviously from that obtained in offshore low-altitude humid environment or inland high-altitude semi-arid environment,suggesting that the pattern of increasing δ~(13)C with the altitude cannot be generalized.The negative correlation between δ ~(13)C and altitude might be attributed mainly to the strengthening of carbon isotope fractionation in plants caused by increasing precipitation with altitude.Furthermore,there was a remarkable negative correlation between leaf δ ~(13)C and LNC.One possible reason was that increasing precipitation that operates to increase isotopic discrimination with altitude overtook the LNC in determining the sign of leaf δ ~(13)C.The significant negative correlation between leaf δ ~(13)C and SD over altitudes was also found in the present study,indicating that increases in SD with altitude would reduce,rather than enhance plant δ~(13)C values.     

Peat humification- and δ<Superscript>13</Superscript>C<Subscript>cellulose</Subscript>-recorded warm-season moisture variations during the past 500 years in the southern Altai Mountains within northern Xinjiang of China

To predict future spatio-temporal patterns of climate change, we should fully understand the spatio-temporal patterns of climate change during the past millennium. But, we are not yet able to delineate the patterns because the qualities of the retrieved proxy records and the spatial coverage of those records are not adequate. Northern Xinjiang of China is one of such areas where the records are not adequate. Here, we present a 500-yr land-surface moisture sequence from Heiyangpo Peat (48.34°N, 87.18°E, 1353 m a.s.l) in the southern Altai Mountains within northern Xinjiang. Specifically, peat carbon isotope value of cellulose (δ¹³C_cellulose) was used to estimate the warm-season moisture variations and the degree of humification was used to constrain the δ¹³C_cellulose-based hydrological interpretation. The climatic attributions of the interpreted hydrological variations were based on the warm-season temperature reconstructed from Belukha ice core and the warm-season precipitation inferred from the reconstructed Atlantic Multidecadal Oscillations (AMO). The results show that humification decreased and the δ¹³C_cellulose-suggested moisture decreased from ~1510 to ~1775 AD, implying that a constant drying condition may have inhibited peat decay. Our comparison with reconstructed climatic parameters suggests that the moisture-level decline was most likely resulted from a constant decline of precipitation. The results also show that humification kept a stable level and the δ¹³C_cellulose-suggested moisture also decreased from ~1775 to ~2013 AD, implying that peat decay in the acrotelm primarily did not depend on the water availability or an aerobic environment. Again, our comparison with reconstructed climatic parameters suggests that the land-surface moisturelevel decline was most likely resulted from a steady warming of growing-season temperature.     

Altitudinal trends in δ<Superscript>13</Superscript>C value,stomatal density and nitrogen content of <Emphasis Type="Italic">Pinus tabuliformis</Emphasis> needles on the southern slope of the middle Qinling Mountains,China

In this study, a coniferous tree species (Pinus tabuliformis Carr.) was investigated at a moderate-altitude mountainous terrain on the southern slope of the middle Qinling Mountains (QLM) to detect the trends in carbon isotope ratio (δ¹³C), leaf nitrogen content (LNC) and stomatal density (SD) with altitude variation in north-subtropical humid mountain climate zone of China. The results showed that LNC and SD both significantly increased linearly along the altitudinal gradient ranging from 1000 to 2200 m, whereas leaf δ¹³C exhibited a significantly negative correlation with the altitude. Such a correlation pattern differs obviously from that obtained in offshore low-altitude humid environment or inland high-altitude semi-arid environment, suggesting that the pattern of increasing δ¹³C with the altitude cannot be generalized. The negative correlation between δ¹³C and altitude might be attributed mainly to the strengthening of carbon isotope fractionation in plants caused by increasing precipitation with altitude. Furthermore, there was a remarkable negative correlation between leaf δ¹³C and LNC. One possible reason was that increasing precipitation that operates to increase isotopic discrimination with altitude overtook the LNC in determining the sign of leaf δ¹³C. The significant negative correlation between leaf δ¹³C and SD over altitudes was also found in the present study, indicating that increases in SD with altitude would reduce, rather than enhance plant δ¹³C values.