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1.
This study analyzes the impacts of climate change on maize yields using an econometric model that incorporates climate, economic, and technology variables. The major finding is climate change will not universally cause negative impacts of maize yields in the United States and China. The results of a simulation of climate change on maize yields over the period 2008-2030 show that a combination of changes in temperature and precipitation can either bring positive or negative effects on maize yields. Furthermore, variation in regional climatic and economic conditions makes the impacts of climatic change on maize yields substantially different in different regions. In this research, the impacts of climate change on maize yields are not simply examined by climate factors. Economic and technology adaptation effects on maize yields are also incorporated. Thus, even with significant changes in climate conditions that alter the maize crop’s growing environment and affect crop yields, a decrease in maize supply due to a decrease in maize yields would lead to an increase in the maize price, which in turn would induce farmers to add more investments in production inputs to raise yields. Thus, the decrease in actual yields may not be as dramatic as predicted in only climate factor considered cases. In this research, findings gained from the study can be used for early-staged policymaking decisions and advanced problem prevention programs. To ensure the continuous increase in maize yields in the future, further studies and research, as well as efficient environmental policies and actions are required. 相似文献
2.
Freely available glucose improves the conditions for soil microorganisms which are utilized as food by Collembola. We examined the effects of glucose application on collembolan (Folsomia candida Willem) growth and on several biotic and abiotic soil parameters (microbial biomass, soil respiration, qCO2, dissolved organic carbon, inorganic nitrogen, and Olson-P) in an artificial system without predatory pressure on Collembola. Glucose addition increased soil respiration and qCO2, and decreased nutrient levels in the soil. Collembolan growth increased with increasing glucose doses. We conclude that the availability of carbon substrates can sustain collembolan growth via an improvement of microbial growth conditions. 相似文献
3.
The external layer of a teleost fish scale is composed of type I collagen, an amorphous matrix substance and hydroxyapatite
crystals. Calcification of this layer can be inhibited in the scale-regenerating process under calcium- and phosphate-deficient
(CaDPD) conditions, and can be facilitated by incubation in physiological saline. The aim of this study was to evaluate this
model of calcification using histological and quantitative analysis in order to promote further understanding of the mechanism
of calcification in fish scales. We found that the external layer of the scales produced under CaDPD conditions contained
more densely aligned collagen fibrils with a small amount of the amorphous matrix substance. The CaDPD scale contained only
one-third of the amount of calcium and phosphate present in the control fish. After 4 hours of incubation, a two- to threefold
increase in calcium content and a 1.5-fold increase in phosphate content were observed. Calcification proceeded in the external
layer, and mineral deposits grew only in the electron-dense matrix substance. We conclude that this model would be suitable
for studying the early process of fish scale calcification that occurs in the noncollagenous substance. The electron-dense
substance may contain key molecules that promote calcification. 相似文献
4.
5.
Takeshi Yamamoto Hiroyuki Okamoto Hirofumi Furuita Koji Murashita Hiroyuki Matsunari Yasuro Iwashita Shunji Amano Nobuhiro Suzuki 《Fisheries Science》2014,80(3):569-579
A 10-week feeding trial was conducted to evaluate the growth and physiological condition of F1 amago salmon Oncorhynchus masou ishikawae juveniles obtained from broodstock that had been selected for growth on a low fish-meal (LFM) diet. F1 juveniles from broodstock showing superior or inferior growth on a LFM diet (LFM-S, LFM-I), and those from broodstock showing intermediate growth on a fish meal-based (FM) diet (FM-M), were fed a LFM diet and a FM diet. In fish fed the LFM diet, growth of LFM-S was significantly better than FM-M at 3 weeks; however, this superiority in growth disappeared at the end of the 10-week trial. Growth of LFM-I was significantly lower than LFM-S throughout the feeding trial. Growth of fish fed the FM diet was not significantly different among groups, and higher than fish fed the LFM diet. Improvements in the blood hemoglobin concentration and morphological conditions of the distal intestine and liver were observed in LFM-S fed the LFM diet. Although the effect of selective breeding was limited in F1 amago salmon, the present results suggest that continuous selection for growth with a LFM diet has potential as a method to adapt to the limited supply of fish meal. 相似文献
6.
7.
We investigated the soil and soil water chemistry in abandoned terraced paddy fields (reed stand) and a thicket of deciduous
broad-leaved trees (thicket stand) on the same slope in Sado Island, Japan. The soils gathered from these plots were incubated
under different water conditions to examine the dynamics of dissolved ions. The organic carbon pool in the soil in the reed
stand at the lower slope position was greater than the thicket stand at the middle slope position. The high concentration
of base cations and an almost neutral pH of the soil water at the reed stand corresponded with the high exchangeable cation
concentrations and base saturation in the soil. These results reflect the mineral-rich groundwater percolating down the slope,
which may be produced by chemical weathering. An in situ sulfate reduction in the reed stand at deeper soil horizons was identified.
The different water conditions in the incubated soils affected the soil pH(H2O), transformation of Fe, and dominant anions (NO3
−, HCO3
−, and SO4
2−). These biogeochemical processes were more conspicuous in the reed stand at the lower slope position where the concentrations
of organic matter and base cations were high. When the abandoned terraced paddy field is developed for the conservation of
the Japanese crested ibis (Nipponia nippon) habitat in Sado Island, the reductive subsoil at the lower slope position should be kept waterlogged to limit sulfuric acid
generation. 相似文献
8.
Kei Oyoshi Nobuhiro Tomiyama Toshio Okumura Shinichi Sobue Jun Sato 《Paddy and Water Environment》2016,14(4):463-472
In Asia, rice is a staple cereal crop and the continent accounts for about 90 % of the global rice production and consumption. Statistics on the areas planted with rice or production of paddy rice are fundamental to agriculture-related decisions or policy-making. Asia-Rice Crop Estimation & Monitoring (Asia-RiCE) aims to develop rice-related information, such as paddy field maps, rice growing conditions, yield, and production, using remote sensing tools and disseminate the same at the local and global scales. In this paper, we propose a methodology for the identification of rice-planted areas by using multi-temporal SAR images; a software named INternational Asian Harvest mOnitoring system for Rice (INAHOR) was developed to manipulate the proposed algorithm. The INAHOR uses the imagery observed both at the time of planting of rice and grown-up stages. In this study, two thresholds needed for the INAHOR were optimized based on the detailed land cover data collected through a field survey. Rice-planted areas across the study area in Japan were identified by the INAHOR using the RADARSAT-2 Wide Fine beam mode data. The classification results of RADARSAT-2 VV and VH polarizations were compared. The data with VH polarization showed a higher total accuracy of 83 % with ?20.5 dB and 3.0 dB for the minimum and range thresholds, respectively. The INAHOR is currently being used with the RADARSAT-2, ALOS, and ALOS-2 SAR data in the Southeast Asian countries to assess the robustness of the thresholds and classification accuracies under the framework of Asia-RiCE. 相似文献
9.
Hiromitsu Kisanuki Hisae Oguro Arisa Nakai Suzuki Setsuko Naoyuki Nishimura Nobuhiro Tomaru 《Journal of Forest Research》2008,13(2):143-146
We studied seed bank formation of the threatened star magnolia, Magnolia stellata, to examine the early stage of regeneration. Forty-five seedling plots (2 × 2 m), each including a soil-sampling quadrat
(40 × 40 cm), were established randomly under or around the crowns of mature M. stellata trees. Seeds of M. stellata were collected from each quadrat to a depth of 5 cm. Only four seeds of M. stellata were found (0.56 seeds/m2) and all were located under mature crowns. Current-year seedlings were abundant in water channels, on moss, or under mature
crowns, suggesting that the seeds may require wet soil conditions for germination. Magnolia stellata seeds show considerable germination below the crowns of mature trees in the year following masting, while some seeds remain
dormant in the soil. Considering the soil seed bank and the current-year seedling bank of M. stellata, a frequent supply of seed is essential for the regeneration of this species. Thus, it is important to maintain mature trees
in addition to promoting seed production. 相似文献
10.
Yasuro Iwashita Nobuhiro Suzuki Takeshi Yamamoto Jun-ichirou Shibata Keiichirou Isokawa Ang H Soon Yuto Ikehata Hirofumi Furuita Tsuyoshi Sugita Takanobu Goto 《Fisheries Science》2008,74(5):1083-1095
The supplemental effects of cholyltaurine and soybean lecithin to a defatted soybean meal (SBM)-based fish meal-free diet
on the hepatic and intestinal morphology of rainbow trout Oncorhynchus mykiss were investigated. A fish meal-based diet (FM), three fish meal-free diets supplemented either with soybean lecithin (SL),
bovine gall powder (BG) or cholyltaurine (C-tau) and an unsupplemented fish meal-free diet (NFM), were given to fish (−11
g) for 10 weeks. The growth was the lowest in fish fed diet NFM, intermediate in fish fed diet SL and the highest in fish
fed diet FM, BG and C-tau. Hepatocytes of fish fed diet NFM were atrophied, and the distal intestine of these fish showed
abnormal features: disintegrated microvilli and fatty degeneration in epithelial cells and increased amount of connective
tissue in the submucosa. Hepatic and intestinal histological features in fish fed diets SL, BG and C-tau were similar to those
in fish fed diet FM. These results indicate that soybean lecithin, bovine bile salts and cholyltaurine have similar effects
on normalizing the hepatic and intestinal morphologies of rainbow trout fed the SBM-based diet, although growth promotion
effect was limited in the soybean lecithin. 相似文献