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Nitrogen (N) and silicon (Si) are important nutritional elements for rice. However, excessive N fertilizer application and the ignorance of Si fertilizer are common in practice. Straw biochar is rich in Si, which can be used as a potential Si fertilizer. In this study, we conducted a consecutive 3-year field experiment to explore the effects of N fertilizer reduction combined with straw biochar application on rice yield, Si and N nutrition. There were five treatments: conventional N application (180 kg ⋅ hm², N100), 20% N reduction (N80), 20% N reduction with 15 t ⋅ hm² biochar (N80+BC), 40% N reduction (N60), and 40% N reduction with 15 t ⋅ hm² biochar ( N60+BC). The results showed that compared with N100, 20% N reduction did not affect the accumulation of Si and N in rice; 40% N reduction reduced foliar N absorption, but significantly increased foliar Si concentration by 14.0%-18.8%; while combined application of biochar significantly increased foliar Si accumulation, with an increase of Si concentration by 38.0%-63.3% and Si absorption by 32.3%-49.9%, but further reduced foliar N concentration. There was a significant negative correlation between Si and N concentration in mature rice leaves, but no correlation between Si and N absorption. Compared with N100, N reduction or combined application of bio- char did not affect soil ammonium N and nitrate N, but increased soil pH. Nitrogen reduction combined application of biochar significantly increased soil organic matter by 28.8%-41.9% and available Si content by 21.1%-26.9%, with a significant positive correlation between them. Compared with N100, 40% N reduction reduced rice yield and grain setting rate, while 20% N reduction and combined application of biochar did not influence rice yield and yield components. In summary, appropriate N reduction and combined with straw biochar can not only reduce N fertilizer input, but also improve soil fertility and Si supply, which is a promising fertilization method in double-cropping rice fields. [ABSTRACT FROM AUTHOR]

Long-term natural geochemical processes result in wide occurrence of fluoride contamination in underground water and fluoride exposure via drinking water for over 500 million people globally. The control of fluoride pollution and fluorosis is one of the most important issues for drinking water safety. In the past several decades, many initiatives failed in defluoridation of water. Better understanding of fluoride occurrence mechanisms in underground water chemistry and the prediction of high-risk areas by geographic information and remote sensing are of crucial importance to minimize fluorosis occurrence. The use of alternative source water or blending should be considered as priority option. Much efforts should be devoted to the fundamental studies on defluoridation reagents and innovative materials, and to the development of highly-efficient, economic, easy-to-handle and stable technologies and integrated instruments. Furthermore, the design, construction, operation, and supervision of defluoridation facilities should be carefully evaluated and strengthened to achieve stable benefits as much as possible. [ABSTRACT FROM AUTHOR]

We conducted a 12-month fine root decomposition experiment under 19-year-old Mytilaria laosensis and Cunninghamia lanceolate plantations to explore the dynamics of nutrient concentration and microbial community composition. The aim of this study was to provide insights into nutrient cycling under plantations with different tree species. Our results showed that the initial concentrations of phosphorus (P) and potassium (K) were significantly higher in the fine root of M. laosensis than those in C. lanceolata ; which significantly decreased with decomposition. Nitrogen (N) concentration in fine roots of both species increased with decay time. The variation of N concentration in fine root of C. lanceolata lagged behind that in M. laosensis. During the decomposition' magnesium (Mg) concentration in fine root of C. lanceolata showed no significant changes; but that of M. lao- sensis decreased at the initial decay stage and increased thereafter and was significantly lower than that of C. lanceolata at the 8th month. The ratio of fungi to bacteria (F/B) of both species decreased at the initial stage and then increased ; with significantly higher F/B in fine root of M. laosensis than that of C. lanceolate after one-year decay. Redundancy analysis (RDA) showed that changes in N and K concentrations and C/N ratio explained 37.2%, 14.5% and 14.8% of the variations in microbial community composition of C. lanceolata fine root respectively. However, during the decay of M. laosensis fine root, concentrations of Mg and K were key factors, accounting for 35.9% and 17.6% of the variations in microbial community composition, respectively. We concluded that other nutrients beyond N, such as Mg, might also be an important factor affecting root decomposition in different tree species. [ABSTRACT FROM AUTHOR]

An experiment was carried out to study the effects of different nitrogen application rates (0, 60, 120, 150, 180 and 240 kg N·hm-2) on the nitrogen uptake, utilization and distribution of short season cotton cultivar (CCRI-50) which was directly seeded after wheat harvest. Results showed that nitrogen application increased the nitrogen uptake of cotton at different growth stages, with the highest increment at the peak flowering-boll opening stage. Nitrogen application changed the percentages of nitrogen uptake among different growth stages. The percentages of nitrogen uptake decreased from seedling to peak flowering stage, but increased from peak flowering to boll maturing stage. In addition, nitrogen application reduced the decreasing speed of nitrogen concentration in middle and upper fruiting branches at later growth stages. Direct-seeded cotton had nitrogen and biomass accumulation in the lower and middle reproductive branches. With the nitrogen application of 150-180 kg·hm-2, the lint yield, NARE (nitrogen apparent recovery efficiency) and the economic coefficient of biomass and nitrogen were relatively higher, and the eigenvalues of dynamic model of nitrogen content and nitrogen accumulation were relatively coordinate. Excessively high nitrogen application (over 180 kg N·hm-2) decreased biomass and nitrogen amount of reproductive organ in lower and middle branches, narrow rise of yield, and lower nitrogen use efficiency. However, excessively low nitrogen application (lower than 150 kg N·hm-2) also resulted in lower economic coefficient of biomass and nitrogen and yield. These results suggested the optimum nitrogen application rate 150-180 kg N·hm-2 for direct-seeded cotton after wheat harvest in lower reaches of Yangtze River. [ABSTRACT FROM AUTHOR]

The effects of nitrogen (N) forms (ammonium-N and nitrate-N) on the growth, yield and fruit quality of tomato plants (cv. Zhongyan 988) under controlled alternate partial root zone irrigation (APRI) were examined in a split-root experiment. Under the same irrigation mode and/or controlled soil water limitation treatment, ammonium-N promoted plant growth at the early stage, while nitrate-N improved plant growth and development at the later stage leading to higher biomass accumulation and fruit yield at harvest. Under APRI and the same soil water conditions, plants of the nitrate-N treatment improved the content of vitamin C and the ratio of soluble sugar to organic acid and thus facilitated fruit quality when compared with those of the ammonium-N treatment. Plant height and leaf area under APRI treatment were lower compared with conventional irrigation (CK) under the same N form, but the stem diameter under APRI treatment with 60% θf KG*2 (field water capacity, θf) soil moisture showed a slight increase at the late growth stage. Under the same N form, fruit yield was significantly lower in APRI treatment than that of the CK. Compared with the CK, fruit yield decreased by 22.4%-26.3% under the APRI treatment with 40%θf soil moisture. Under 60% θf soil moisture, the APRI treatment significantly improved fruit quality and water-use efficiency compared with the CK regardless small reduction (5.3%-5.4%) in fruit yield. The experimental results suggested that the APRI treatment with the lower limitation of soil moisture controlled at 60% θf and nitrate-N supply would be the optimal option in terms of sustainable use of water resource and fertilizer. [ABSTRACT FROM AUTHOR]

Dendrochronological techniques including correlation functions and single-years analysis were used to study the relationship between the two kinds of Korean pine radial growth in Liangshui Natural Reserve and climatic variables, and to assess the similarities and differences between Korean pine with coarse bark (Pinus koraiensis forma pachidermis) and fine bark (Pinus koraiensis forma leptodermis) in response to climate factors, the main affecting factors and whether the response relationship could be of long-term stability. The results showed that the Korean pine with fine bark was more suitable for dendrochronological study. The radial growth of the two kinds of Korean pine was very sensitive to environmental variables and their climate responses had no significant differences. From 1902 to 2009, meteorological factors in the growing season, especially in June were the primary factors affecting the radial growth of the two kinds of Korean pine in the study area. The temperature showed a significant negative correlation and the precipitation showed a significant positive correlation. The Korean pine growing in different periods had a significantly different response to meteorological factors. With the rapid rise of temperature and drought after 1970, the radial growth of the two kinds of Korean pine was more sensitive to the meteorological factors than before, which was especially more sensitive to temperature in growing season and PDSI in many seasons. [ABSTRACT FROM AUTHOR]

Cotton cultivar NuCOTN 33B was planted in isolated pools treated with drought or waterlogging for 7 or 14 d to explore their effects on cotton boll carbohydrate content and its relationship with the biomass accumulation. The results showed that the drought treatment reduced the carbohydrate content of cotton boll shell on middle fruit branches, but had a weak effect on cotton boll shells on lower fruit branches. Soluble sugar, starch and sucrose contents of cotton boll shell on upper fruit branches under the drought condition and on whole plant branches under waterlogging treatment changed similarly, namely, the soluble sugar and starch content increased, while the sucrose content went down firstly and then increased later, which indicated that the exportation of sucrose from boll shell was inhibited and became worse with the increase of waterlogging duration. Compared with the boll shell, the carbohydrate contents of cotton seed were less affected by the drought and waterlogging treatments at the flowering and bolling stage. Under the treatments of drought and 7 d-waterlogging, the biomass accumulation of cotton bolls on the middle fruit branches initiated earlier but lasted less days, and the maximum speed at lower and upper fruit branches reduced, while the treatment of waterlogging for 14 d caused the decline of maximum speed of biomass accumulation of bolls on whole branches. On the other side, the correlation analysis showed the significant positive relationships among the boll biomass, the maximum speed and the contents of soluble sugar and sucrose in the boll shell respectively. In conclusion, the treatment of drought and waterlogging at the flowering and bolling stage retarded the outward transportation of sucrose from cotton bolls, changed the boll biomass accumulation characteristics, and therefore were detected as the important cause of cotton boll total biomass reduction. [ABSTRACT FROM AUTHOR]

A field experiment was conducted using the litterbag method to quantify the contribution of soil fauna to litter mass loss of Salix paraplesia, Sabina saltuaria, Betula albosinensis and Abies faxoniana during different key periods of the decomposition process of the first year (from November 2011 to October 2012). The results showed that the mass loss rate showed S. paraplesia > B. albosinensis > A. faxoniana > S. saltuaria, and the rate in the growing season was greater than in the freeze-thaw season. The contribution rate of soil fauna to the mass decomposition displayed as S. saltuaria (26. 7%) > A. faxoniana (18. 8%) > B. albosinensis (15. 7%) > S. paraplesia (13. 2%), which was higher in the freeze-thaw season than in the growing season for litter of B. albosinensis and A. faxoniana while vice versa for litter of B. albosinensis and A. faxoniana. The contribution of soil fauna was mainly related to organic C, P and N/ P in the freeze-thaw season, while N, C/ N, lignin and lignin/ cellulose in the growing season. [ABSTRACT FROM AUTHOR]

Taking the water level fluctuating zone of the Danjiangkou Reservoir as a case, and by the method of hierarchical cluster analysis, the soil seed banks at 37 sampling plots within the areas of 140-145 m elevation were divided into 6 groups, and the species composition, density, and diversity of the soil seed banks among the groups were compared. The differences between the soil seed banks and the aboveground vegetations were analyzed by S-rensen similarity coefficient, and the correlations among the soil seed banks, aboveground vegetations, and environmental factors were explored by principal component analysis (PCA) and multivariable regression analysis. At the same altitudes of the water level fluctuating zone, the species composition of the soil seed banks had obvious heterogeneity, and the density and diversity indices of the soil seed banks among different groups were great. The similarity coefficient between the soil seed banks and aboveground vegetations was low, and the species number in the soil seed banks was obviously lesser than that in the aboveground vegetations. The density of the soil seed banks was highly positively correlated with the aboveground vegetations coverage and species number and the soil texture, but highly negatively correlated with the soil water-holding capacity and soil porosity. [ABSTRACT FROM AUTHOR]

A field experiment was conducted to study the leaf morphological structure and physiological and biochemical characteristics of female and male Hippophae rhamnoides subsp. sinensis under different soil moisture condition. When the soil moisture condition was poorer, the leaf structure of the plants displayed distinct xeromorphic characteristics, being more obvious for the female plants. Comparing with those of male plants, the leaf thickness, thickness of upper and lower epidermis, and the distance between lateral vein bundles of female plants were smaller, while the thickness and density of lower epidermis hairs and the ratio of palisade tissue thickness to sponge tissue thickness were in adverse, indicating that female plants had stronger drought adaptability and greater ecological plasticity. With the decrease of soil moisture content, the leaf dissociative proline, dissoluble sugar, and malonaldehyde (MDA) contents of both male and female plants all increased, but for female plants, the increment of their leaf dissociative proline and dissoluble sugar contents was larger, while that of MDA content was smaller than the male plants. With the changes of soil moisture content, the leaf superoxide dismutase and catalase activities of the plants varied greatly, but had no regular pattern. Under the stress of soil drought, the values of multivariate membership function of test parameters were larger for the female than the male plants, suggesting that the female plants of H. rhamnoides subsp. sinensis had stronger physiological regulation capability and greater adaptability to drought stress. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to study the effects of applying 0, 240 , and 480 kg N·hm-2 on the cotton leaf antioxidant enzyme activities and endogenous hormone contents under eight days waterlogging at flowering and boll-forming stage. Under this short-term waterlogging, the leaf soluble protein content and SOD and CAT activities decreased while the MDA content and POD activity increased, and in the meantime, the leaf ABA content increased while the ZR, GA, and IAA contents as well as the ZR/ABA, IAA/ABA, and GA/ABA ratios decreased , compared with those under normal watering. Treatment 240 kg N·hm-2 had the lowest contents of leaf MDA and ABA, but the highest contents of leaf ZR, GA , and IAA, highest ratios of ZR/ABA, GA/ABA, and IAA/ABA, and highest net photosynthetic rate. At the 15th day after terminating waterlogging, no significant differences in the leaf antioxidant enzyme activities, MDA content, and endogenous hormone contents were observed between the short-term waterlogged and well-watered cotton. N application promoted the cotton leaf antioxidant enzyme activiti es, decreased the MDA and ABA contents, and increased the ZR, GA, and IAA contents as well as the ZR/ABA, IAA/ABA, and GA/ABA ratios, with the highest cotton biomass and yield in treatment 240 kg N·hm-2. [ABSTRACT FROM AUTHOR]

An investigation was made from July 2005 to June 2006 to understand the spatial distribution of macroinvertebrates in Xiangxi River, the largest tributary in Hubei portion of Three Gorges Reservoir. The results showed that Ephemeroptera baetis spp., Ephemeroptera epeorus spp., and Plecoptera nemoura spp. were the dominant taxa. There existed greater differences in the habitat characters and in the community structure of macroinvertebrates among the major tributaries of Xiangxi River, and the relative abundance of functional feeding groups could reflect the characters of different habitats. A comparison of the diversity of dominant taxa and their tolerance towards pollution among the major tributaries showed that Jiuchong River had the best habitat, followed by the main stream of Xiangxi River, and Gaolan River and Gufu River. Canonical correspondence analysis showed that the NH4+-N concentration in the main stream of Xiangxi River, the pH, turbidity, water depth, SiO2, conductance, and alkalinity in Jiuchong River, the turbidity in Gaolan River, and the NH4+-N and NO3--N concentrations in Gufu River had significant impact on the community structure of macroinvertebrates. [ABSTRACT FROM AUTHOR]