Dynamics and genetic regulation of macronutrient concentrations during grain development in maize

Nitrogen(N), phosphorus(P), and potassium(K) are essential macronutrients that are crucial not only for maize growth and development, but also for crop yield and quality. The genetic basis of macronutrient dynamics and accumulation during grain filling in maize remains largely unknown. In this study, we evaluated grain N, P, and K concentrations in 206 recombinant inbred lines generated from a cross of DH1M and T877 at six time points after pollination. We then calculated conditional phenotypic values at different time intervals to explore the dynamic characteristics of the N, P, and K concentrations. Abundant phenotypic variations were observed in the concentrations and net changes of these nutrients. Unconditional quantitative trait locus(QTL) mapping revealed 41 non-redundant QTLs, including 17, 16, and 14 for the N, P, and K concentrations, respectively. Conditional QTL mapping uncovered 39 non-redundant QTLs related to net changes in the N, P, and K concentrations. By combining QTL, gene expression, co-expression analysis, and comparative genomic data, we identified 44, 36, and 44 candidate genes for the N, P, and K concentrations, respectively, including GRMZM2G371058 encoding a Doftype zinc finger DNA-binding family protein, which was associated with the N concentration, and GRMZM2G113967encoding a CBL-interacting protein kinase, which was related to the K concentration. The results deepen our understanding of the genetic factors controlling N, P, and K accumulation during maize grain development and provide valuable genes for the genetic improvement of nutrient concentrations in maize.

Effects of forest canopy density and epixylic vegetation on nutrient concentrations in decaying logs of a subalpine fir forest

Background:Deadwood and the associated epixylic vegetation influence nutrient cycles in forest ecosystems.Open canopies strongly regulate deadwood decomposition and disrupt epixylic vegetation on logs.However,it is unclear how the forest canopy density and epixylic vegetation growth affect the nutrient concentrations in deadwood.Methods:We measured the concentrations of nitrogen(N),phosphorus(P),potassium(K),calcium(Ca),sodium(Na),magnesium(Mg),and manganese(Mn)in experimentally exposed decaying logs placed in gaps,at the edge of gaps,and under the closed canopy during a four-year decomposition experiment in a Subalpine Faxon fir forest(Abies fargesii var.faxoniana)on the eastern Qinghai-Tibetan Plateau,China.To assess the effect of the epixylic vegetation,we experimentally removed it from half of the logs used in the study.Results:Under open canopy conditions in the gap and at the edge,the concentrations for most of the nutrients in the bark and the highly decayed wood were lower than under the closed canopy.The effect of the epixylic treatment on nutrient concentrations for all but K and Na in barks varied with the decay classes.Significantly lower concentrations of N,P,Ca,and Mn following the removal of epixylic vegetation were observed in the wood of decay class IV.Epixylic vegetation significantly increased most nutrient concentrations for decaying barks and wood under open canopy conditions.In contrast,epixylic vegetation had no or minimal effects under the closed canopy.Conclusions:Forest canopy density and epixylic vegetation significantly alter the nutrient concentrations in decaying logs.Open canopies likely accelerate the rate of nutrient cycling between the epixylic vegetation and decaying logs in subalpine forests.

Changes of nutrient concentrations and N:P:Si ratios and their possible impacts on the Huanghai Sea ecosystem

To investigate the impacts of nutrient concentrations and N：P：Si ratios on the ecosystem of the Huanghai Sea （Yellow Sea）, the current status and long-term variation of nutrients concentrations and ratios as well as phytoplankton community structure in the Huanghai Sea were collected and analyzed. The results reveal great annual and seasonal fluctuations in the nutrient concentrations and N：P：Si ratios during 1998-2008 with no clear pattern observed in the whole region. Yet on a seasonal scale of spring and in the coastal regions such as the Jiaozhou Bay and Sanggou Bay, the increase of DIN concentration and N：P ratio as well as the decrease of phosphate and sili- cate concentrations and Si：N ratios were relatively significant. Many pelagic ecosystem changes have occurred concurrent with these changes of the nutrient regime, such as the recent increase of primary production, changes of phytoplankton chlorophyll a biomass and abundance, an increase of eutrophication, and occurrence of HABs. In addition, new trends in the variation of nutrients seem to be developing in some particular transect such as 36N, which suggests that long-term and systematic ecosystem monitoring in the Huanghai Sea is necessary.

Effect of nitrogen and phosphorus addition on leaf nutrient concentrations and nutrient resorption efficiency of two dominant alpine grass species

Nitrogen(N)and phosphorus(P)are two essential nutrients that determine plant growth and many nutrient cycling processes.Increasing N and P deposition is an important driver of ecosystem changes.However,in contrast to numerous studies about the impacts of nutrient addition on forests and temperate grasslands,how plant foliar stoichiometry and nutrient resorption respond to N and P addition in alpine grasslands is poorly understood.Therefore,we conducted an N and P addition experiment(involving control,N addition,P addition,and N+P addition)in an alpine grassland on Kunlun Mountains(Xinjiang Uygur Autonomous Region,China)in 2016 and 2017 to investigate the changes in leaf nutrient concentrations(i.e.,leaf N,Leaf P,and leaf N:P ratio)and nutrient resorption efficiency of Seriphidium rhodanthum and Stipa capillata,which are dominant species in this grassland.Results showed that N addition has significant effects on soil inorganic N(NO_(3)^(-)-N and NH_(4)^(+)-N)and leaf N of both species in the study periods.Compared with green leaves,leaf nutrient concentrations and nutrient resorption efficiency in senesced leaves of S.rhodanthum was more sensitive to N addition,whereas N addition influenced leaf N and leaf N:P ratio in green and senesced leaves of S.capillata.N addition did not influence N resorption efficiency of the two species.P addition and N+P addition significantly improved leaf P and had a negative effect on P resorption efficiency of the two species in the study period.These influences on plants can be explained by increasing P availability.The present results illustrated that the two species are more sensitive to P addition than N addition,which implies that P is the major limiting factor in the studied alpine grassland ecosystem.In addition,an interactive effect of N+P addition was only discernable with respect to soil availability,but did not affect plants.Therefore,exploring how nutrient characteristics and resorption response to N and P addition in the alpine grassland is important to understand nutrient use strategy of plants in terrestrial ecosystems.

Concentrations of foliar and surface soil in nutrients Pinus spp. plantations in relation to species and stand age in Zhanggutai sandy land, northeast China

The concentrations of the foliar and surface soil nutrients and the variation with species and stand age were studied inPinus spp. plantations in Zhanggutai area, northeast China. The results showed that the total N, total P and C: N ratio of the soil inP. sylvestris var.mongolica stands were significantly higher in comparison with those inP. tabulaeformis andP. densiflora stands. ForP. sylvestris var.mongolica, the foliar P concentration appeared to decrease with age, and the foliar N and K concentrations did not show a consistent change with age. As for the different tree species of the similar age, the foliar N and P concentrations were significantly different (p<0.05), being withP. sylvestris var.mongolica>P. densiflora>P. tabulaeformis. The foliar N: P ratio ofP. densiflora significantly was higher thanP. sylvestris var.mongolica andP. tabulaeformis, while the foliar K was no obvious difference between the three tree species. There were significant correlation (p<0.05) between soil total N and P, soil organic matter and total P, foliar N and P, but it did not show significant correlations between soil and foliar nutrient concentrations, which might attribute to the excessive litter raking, overgrazing and low soil moisture in this area. Based on the foliar N: P ratio, we introduced a combination threshold index of N: P ratio with their absolute foliar nutrient concentrations to determine the possible limiting nutrient. According to the critical N: P ratio and their absolute foliar N, P concentrations, theP. sylvestris var.mongolica stands showed a decreased N limitation degree with age, theP. densiflora stands showed unlimited by N and P in the whole, and theP. tabulaeformis stands showed co-limited by N and P. No significant difference in soil nutrient concentrations of the surface soils was found between 45, 29, 20-yr-oldPinus sylvestris var.mongolica plantation stands. Keywords coniferous trees - foliar nutrient concentration - limiting nutrients - N - P ratio - Zhanggutai sandy land CLC number S718.55 Document code A Article ID 1007-662X(2004)01-0011-08 Foundation item: This research was supported by Key Knowledge Innovation Project (KZCX3-SW-418) of Chinese Academy of Sciences.Biography: CHEN Guang-sheng (1978-), male, master candidate in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. ChinaResponsible editor: Song Funan

Eucalyptus grandis plantations:effects of management on soil carbon,nutrient contents and yields

The expansion of fast-growing tree plantations is a worldwide process,with consequences on soil fertility and soil carbon storage.Disparate results were found on the effects of afforestation with Eucalyptus on soil carbon and other nutrient contents.These discrepancies are usually caused by differences in climate,land use history,soil texture as well as by management related factors such as plantation age,number of rotations,method of establishment(plantation or coppice),harvest residue management and soil preparation.We studied the effect of plantation age,number of rotations,and method of establishment on soils and plant nutrient concentrations in Eucalyptus grandis plantations in NE Argentina on different textured soils.We also determined if yields changed with nutrient variations in soils,and compared soils under plantations to soils under grasslands they replaced.Thirty-one E.grandis stands of different ages,number of rotations and method of establishment were evaluated as well as eight grassland sites.Levels of carbon,nitrogen,phosphorus,potassium,calcium and magnesium were determined for soils and plants.Soil carbon and nitrogen decreased over the number of rotations and were more pronounced in soils with 50-60%sand than soils with>75%sand.Coppice stands showed higher soil carbon and nitrogen levels than plantations,suggesting a negative effect of site preparation before planting on soil nutrient conservation,especially in fine-textured soils.Foliar nutrient concentrations did not follow the trends observed for soil nutrients nor did they reflect nutrient limitations.There was no evidence of decreased yields over successive rotations.Soil carbon and nitrogen contents decrease when grasslands are replaced by E.grandis plantations,and therefore a yield limitation may occur in a medium to long-term frame,especially in stands re-established for short-rotation management.Harvest residue management and site preparation must be specifically designed for improving soil nutrient management.

Effects of Sea Level Variation on Biological and Chemical Concentrations in a Coastal Upwelling Ecosystem

Oscillations in sea level due to meteorological forces related to wind and pressure affect the regular tides and modify the sea level conditions, mainly in restricted waters such as bays. Investigations surrounding these variations and the biological and chemical response are important for monitoring coastal regions mainly where upwelling shelf systems occur. A spatial and temporal database from Quick Scatterometer satellite vector wind, surface stations from the Southeast coast of Brazil and surface seawater data collected in Anjos Bay, Arraial do Cabo city, northeast of Rio de Janeiro State were used to investigate the meteorological influences in the variability of the dissolved oxygen, nutrients, meroplankton larvae and chlorophyll-a concentrations. Multivariate statistical approaches such as Principal Component Analysis (PCA) and Clustering Analysis (CA) were applied to verify spatial and temporal variances. A correlation matrix was also verified for different water masses in order to identify the relationship between the above parameters. A seasonal variability of the meteorological residual presents a well-defined pattern with maximum peaks in autumn/winter and minimum during spring/summer with negative values, period of occurrence of upwelling in this region. This lowering of the sea level is in accordance with the increasing of nutrients and meroplankton larvae for the same period. CA showed six groups and an importance of the zonal and meridional wind variability, including these variables in a single cluster. PCA retained eight components, explaining 64.10% of the total variance of data set. Some clusters and loadings have the same variables, showing the importance of the sea-air interaction.

Annual and Monthly Variations in Litter Macronutrients of Three Subalpine Forests in Western China

Macronutrients （N, P, K, Ca, Mg, and S） in litter of three primarily spruce （Picea purpurea Masters） （SF）, fir （Abies faxoniana Rehder ＆ E. H. Wilson） （FF）, and birch （Betula platyphylla Sukaczev） （BF） subalpine forests in western China were measured to understand the monthly variations in litter nutrient concentrations and annual and monthly nutrient returns via litteffall. Nutrient concentration in litter showed the rank order of Ca 〉 N 〉 Mg 〉 K 〉 S 〉 P. Monthly variations in nutrient concentrations were greater in leaf litter （LL） than other litter components. The highest and lowest concentrations of N, P, K, and S in LL were found in the growing season and the nongrowing season, respectively, but Ca and Mg were the opposite. Nutrient returns via litterfall showed a marked monthly pattern with a major peak in October and one or two small peaks in February and/or May, varying with the element and stand type, but no marked monthly variations in nutrient returns via woody litter, reproductive litter, except in May for the BF, and moss litter. Not only litter production but also nutrient concentration controlled the annual nutrient return and the monthly nutrient return pattern. The monthly patterns of the nutrient concentration and return were of ecological importance for nutrient cycling and plant growth in the subalpine forest ecosystems.

Effects of Different Nitrogen Fertilizer Levels on Fe,Mn,Cu and Zn Concentrations in Shoot and Grain Quality in Rice (Oryza sativa)

In a pot experiment, effects of N fertilizer application on the concentrations of Fe, Mn, Cu and Zn in shoot of rice and the quality of brown rice were studied. In the treatments with N fertilizer application, the concentrations of Fe, Mn, Cu and Zn in most parts of rice shoot increased compared with control （no N fertilizer application）. This indicated that the transportation ability of microelements from root to shoot in rice was improved with N fertilizer application. Effect of N fertilizer on IR68144 was similar to that of on IR64, but the concentrations of the microelements in plant differed, suggesting that the characteristic expression of the two rice genotypes was not controlled by the amount of N fertilizer supplied. The concentrations of those microelements in brown rice increased at first and then decreased with increasing N fertilizer application, reaching the highest at 160 kg/ha, at which the Fe, Mn, Cu and Zn concentrations in brown rice increased by 28.96%, 41.34%, 58.31% and 16.0% for IR64, and by 22.16%, 13.75%, 8.75% and 20.21% for IR68144 compared with control, respectively. Moreover, N fertilizer promoted the accumulation of protein, decreased the accumulation of amylose in grain, and enhanced gel consistency of brown rice. These results indicate that appropriate N fertilizer management could increase micronutrient contents in grain and improve nutrition quality of rice.

Effects of Microbial Inoculants on Nutrient Availability and Rice Yield

Under field conditions, an experiment was conducted to study the effects of ammonification bacteria, potassium bacteria and phosphorus bacteria on nutrient availability in soil and yield of rice in the cold region of China and compared to the conventional fertilization. Results showed that DF1P2 treatment （ammonifiers 1.5× 108 cfu· m2, phosphorus bacteria 1.5× 108 cfu. m2, and potassium bacteria 1.5× 108 cfu· m2） increased available nutrient concentrations in soil, increased the concentrations of N, P, and K in plant organs and increased the rice yield and was the most significantly among all the treatments. This treatment could be recommended as the best suitable biological fertilizer application rate for the rice production in the cold region of China.

Temporal and Spatial Distribution of Nutrients and HABs at Coastal Water of Kota Belud, Sabah

A study was carried out to determine the temporal and spatial distribution of nutrients and Harmful Algal Blooming species (HABs) to establish the relationship between nutrient concentrations and HABs density in the coastal water of Kota Belud, Sabah, Malaysia. Eight stations were set up in four transects (each transect had two stations;one 500 meters seawards from shoreline, and another five kilometers seawards from shoreline) along the Kota Belud coastal area. Phytoplankton samples, water samples and in situ environmental parameters were collected during dry and wet seasons. Altogether nine HABs species were identified from the study area, where six species (Pyrodinium bahamense, Prorocentum micans, Neoceratium furca, Prorocentum sigmoides, Dinophysis caudate, and Neoceratium fursus) belonged to Dinophyceae and three species (Thalassionema nitzchoioides, Chatoceros affinis, Rhizosolenia sp.) belonged to Bacillariophyceae. Among nine species, Chatoceros affinis was the most abundance composed of 80.6% of total species recorded from all stations during study period. Among the toxic producing Dinoflagellate, Pyrodinium bahamense bloom (>103 cells/l) was observed during study period. Trong linear relationship (r2 = 0.80) was observed between the cell density and concentration of nitrate nitrogen. Relationship between cell density and phosphate phosphorus was poor (r2 = 0.51). The study showed that increasing in nutrient concentrations resulted in the increasing of HABs density. Nitrate was seen to be more important than phosphate in Kota Belud water as limiting factor of the growth of HABs.

Effects of grassland amelioration on terrestrial ecosystem nutrients:a case study in Jianou Niukenglong Grassland Ecosystem Experimental Station, Fujian Province

This paper studies the effects of land cover changes on distributions andcirculations of nutrients in a terrestrial ecosystem, taking Jianou Niukenglong Grassland EcosystemExperimental Station as a case study. During a two year experiment from 1994 to 1996, the land covertypes were changed from desert slopeland to grasslands, in particular, Chamaecristarotundifolia(pers) green + Pasdum thunbergii and Glycine max var. + Pasalum thunbergii. In order tostudy land cover change effects on nutrients in the terrestrial ecosystem, we selected organicmaterials (OMs), nitrogen (N), phosphorus (P), potassium (K) and aluminum (Al) to study theirchanges in total soil nutrient concentrations, nutrient reserves in soil, distributions andreservations of nutrients in distinct grassland communities and overall nutrient contents reservedin terrestrial ecosystem, and their circulation with land cover change. The experimental resultsindicate that with the increase of vegetation coverage, the total concentrations of N, P and K growrapidly in the soil, but that of Al decreases markedly. The increases of the total concentrations ofN, P and K were mainly the consequences of changes of the factors that affect soil evolution, e.g.,soil moisture, and changes of soil evolution processes, e.g., weathering rate and the decrease ofsoil erosion. These changes were caused by land coverage growth from desert slopeland to grassland.With the change of the land cover types and the increase of land coverage, the activity of Alaccelerated as well, and the vertical penetration and lateral penetration of Al have been increased.Therefore, the loss of Al within the experimental terrestrial ecosystem was inevitable, and thetotal concentration and reserve of Al in soil have become smaller and smaller, in spite of thegrowth of grass absorbing some amounts of Al. The Al reserve has increased in vegetation, but it hasdeclined in total terrestrial ecosystem. Land cover change also affects the circulations ofnutrients in the terrestrial ecosystem and for the purpose of study on nutrient circulations, wechoose to study plant absorption, litter and reservation of nutrients to establish an index toindicate the situations of nutrient circulations within terrestrial ecosystems. The results indicatethat in the two land cover types (two grassland ecosystems), the sequence of nutrient circulationindices are N > K > P > Al in Chamaecrista rotundifolia(pers) green + Pasalum thunbergii and P > N >K > Al in Glycine max var. + Pasalum thunbergii. On the basis of the study, we can conclude thatland cover change affects both distributions and circulations in the terrestrial ecosystem, and thatdifferent changes have distinct influences on distributions and circulations. Some nutrients wereaffected differently in some contents.

Effects of dietary forage to concentrate ratio and wildrye length on nutrient intake, digestibility, plasma metabolites, ruminal fermentation and fecal microflora of male Chinese Holstein calves

Twenty-eight male, weaned Chinese Holstein calves（（156.8±33.4） kg） were used to investigate the effects of dietary forage to concentrate ratio（F：C） and forage length on nutrient digestibility, plasma metabolites, ruminal fermentation, and fecal microflora. Animals were randomly allocated to four treatments in a 2×2 factorial arrangement： whole-length forage（WL） with low F：C（50：50）; WL with high F：C（65：35）; short-length forage（SL） with high F：C（65：35）; and SL with low F：C（50：50）. Chinese wildrye was used as the only forage source in this trial. The grass in the SL treatments was chopped using a chaff cutter to achieve small particle size（-50% particles 〉19 mm）. Dry matter intake（DMI） and organic matter（OM） intake was increased by increasing both F：C（P〈0.01） and forage length（FL）（P〈0.05）, while acid detergent fiber（ADF） and neutral detergent fiber（NDF） intakes were only increased by increasing the F：C（P〈0.01）. The digestibility of NDF was increased as the FL increased（P〈0.01）, and it was also affected by interaction between F：C and FL（P〈0.05）. Cholesterol（CHO）（P〈0.01）, leptin（LP）（P〈0.05）, and growth hormone（GH）（P〈0.01） concentrations in plasma were increased as dietary F：C increased. A significant increase in plasma triglyceride（TG）（P〈0.01）, insulin（INS）（P〈0.05）, and GH（P〈0.01） levels was observed with decreasing dietary FL. Ruminal p H values of calves fed with low F：C diets were significantly lower than those in high F：C treatment（P〈0.05）. Increasing the F：C enhanced ruminal acetic acid（P〈0.05） and acetic acid/propionic acid（P〈0.01）. Fecal Lactobacillus content was significantly higher, while Escherichia coli and Salmonella contents were significantly lower in WL and high F：C groups（P〈0.05）. Lower fecal scores（higher diarrhea rate） were observed in calves fed with SL hay compared to WL hay（P〈0.05）. Denatured gradient gel electrophoresis（DGGE） bands and richness index（S） were significantly affected by the interaction between F：C and FL（P〈0.05）, under high F：C, band numbers and richness index from WL group were higher than that from SL group（P〈0.05）, whereas there were no differences between WL andSL groups under low F：C（P〉0.05）. Microflora similarity was 50–73% among the different treatments. It is concluded that the WL with high F：C（65：35） diet is suitable for weaned calves.

Characterizing the influence of tide on the physico-chemical parameters and nutrient variability in the coastal surface water of the northern Bay of Bengal during the winter season

The spatial distribution of physico-chemical parameters（sea surface temperature（SST）, p H, sea surface salinity（SSS）, dissolved oxygen（DO） and Secchi depth） along with filterable nutrients（dissolved inorganic nitrate（DIN）,dissolved inorganic phosphate（DIP） and reactive silicate（DSi）） are measured in the winter months of November,December, January and February for four consecutive years from 2009–2010 to 2012–2013 on the shallow continental shelf（〈20 m bathymetry） of the coastal waters（up to 18 km away from shoreline） of the northern Bay of Bengal（n Bo B） during the highest high tide（HHT） and lowest low tide（LLT） hours for the first time. The variability of the coastal biogeochemical environment is assessed during the HHT and LLT hours and for this purpose, seawater samples are collected from seven different locations of a transect in the coastal region. Physicochemical parameters（except SST） show significant difference in magnitude during the HHT and LLT hours respectively. p H, SSS and DO are found to increase in the HHT hours and vice-versa. The data reveal that during the LLT hours, a relative increase of freshwater input in the n Bo B can have elevated the nutrient concentration compared with that observed during the HHT hours. The ratio of nutrient concentration is found to deviate significantly from the Redfield ratio. The abundance of DIP is much higher compared with that of DIN and DSi.The anthropogenic sources of DIP from the upstream flow（especially the domestic effluent of several metropolises） can be mainly attributed behind such an observation. In order to characterize and establish the trend of such variation in such an important bio-climatic region, long-term and systematic ecosystem monitoring in the coastal water of the n Bo B northern Bay of Bengal should be carried out throughout the year.

N and P resorption in a pioneer shrub(Artemisia halodendron) inhabiting severely desertified lands of Northern China

Nutrient resorption is an important conservation mechanism for plants to overcome nutrient limitation in the less fertile area of desertifled land. In the semi-arid Horqin Sandy Land of Northern China, the shrub Artemisia ha/odendron usually colonizes into the bare ground of severely desertified land as a pioneer species. It is, therefore, expected that A. ha/odendron will be less dependent on current nutrient uptake through efficient and proficient re- sorption of nutrients. In this study, we found that averaged nitrogen （N） and phosphorus （P） concentrations in se- nesced leaves significantly varied from 12.3 and 1.2 mg/g in the shifting sand dune to 15.9 and 1.9 mg/g in the fixed sand dune, respectively, suggesting that foliar N and P resorption of A. ha/odendron were more proficient in the shifting sand dune. In particular, positive relationships between nutrient concentrations in senesced leaves and soil nutrient availability indicate that A. ha/odendron in infertile habitats is more likely to manage with a low level of nu- trients in senesced leaves, giving this species an advantage in infertile soil. Moreover, foliar N- and P-resorption efficiencies and proficiencies showed limited inter-annual variability although annual precipitation varied greatly among 2007-2009. However, N and P resorption of A. ha/oc/endron were not more efficient and proficient than those previously reported for other shrubs, indicating that the pioneer shrub in sand dune environments does not rely more heavily than other plants on the process of resorption to conserve nutrients. Incomplete resorption of nutrients in A. halodendron suggests that senesced-leaf fall would return litter with high quality to the soil, and thereby would indirectly improve soil nutrient availability. The restoration of desertified land, therefore, may be ac- celerated after A. halodendron pioneers into shifting sand dunes.

Effects of nitrate concentration in interstitial water on the bioremediation of simulated oil-polluted shorelines

Nutrient addition has been proved to be an effective strategy to enhance oil biodegradation in marine shorelines. To determine the optimal range of nutrient concentrations in the bioremediation of oil-polluted beaches, nitrate was added to the simulated shoreline models in the initial concentration of 1, 5 and 10 mg/L. Whenever the NO3-N concentration declined to 70% of its original value, additional nutrients were supplemented to maintain a certain range. Results showed adding nutrients increased the oil biodegradation level, the counts of petroleum degrading bacteria （PDB） and heterotrophic bacteria （HB）, and the promoted efficiency varied depending on the concentration of nitrate. Oil degradation level in 5 mg/L （NO3-N） group reached as much as 84.3% accompanied with the consistently highest counts of PDB; while in l mg/L group oil removal efficiency was only 35.2%, and the numbers of PDB and HB were relatively low compared to the other groups supplemented with nutrients. Although counts of HB in the 10 mg/L group were remarkable, lower counts of PDB resulted in poorer oil removal efficiency （70.5%） compared to 5 mg/L group. Furthermore, it would need more NO3-N （0.371 mg） to degrade 1 mg diesel oil in the 10 mg/L group than in the 5 mg/L group （0.197 mg）. In conclusion, Nitrate concentration in 5 mg/L is superior to l and 10 mg/L in the enhancement of diesel oil biodegradation in simulated shorelines.

Dynamics of Above-and Below-ground Biomass and C,N,P Accumulation in the Alpine Steppe of Northern Tibet

The temporal dynamics of the biomass, as well as the carbon （C）, nitrogen （N）, phosphorus （P） concentrations and accumulation contents, in above- and below-ground vegetation components were determined in the alpine steppe vegetation of Northern Tibet during the growing season of 2OLO. The highest levels of total biomass （311.68 g m-2）, total C （115.95 g m-2）, total N （2.60 g m-2）, and total P （0.90 g m-2） accumulation contents were obtained in August in 2010. Further, biomass and nutrient stocks in the below-ground components were higher than those of the above-ground components. The dominant species viz., Stipa purpurea and Carex moorcrofli had lower biomass and C, N, P accumulations than the companion species which including Oxytropis. spp., Artemisia capillaris Thunb., Aster tataricus L., and SO on.

Dynamics of fine root N,Pand K in high elevation forests of central Himalaya

Fine root nutrient dynamics were calculated for one year in three high elevation forests of Indian central Himalaya. In all sites, fine root nutrient concentrations varied with respect to forests and seasons. N concentration in fine roots was highest followed by K and P. In general, fine roots showed their highest nutrient concentrations during the rainy season and lowest in winter. Higher nutrient concentrations during the rainy season may be related to favorable moisture and temperature regimes which in turn results in increased plant growth activities. Present fine root nutrient amounts and nutrient uptake values decreased towards high elevations. In general, the highest amounts of nutrients in both live and dead fine roots were observed in September and the lowest in the month of June. Turnover rates of the nutrients in the fine roots also decreased with an increase in elevation.

Decadal variations in diatoms and dinoflagellates on the inner shelf of the East China Sea, China

Diatoms and dinoflagellates are two major groups ofphytoplankton that flourish in the oceans, particularly in coastal zone and upwelling systems, and their contrasting production have been reported in several world seas. However, this information is not available in the coastal East China Sea （ECS）. Thus, to investigate and compare the decadal trends in diatoms and dinoflagellates, a sediment core, 47-cm long, was collected from the coastal zone of the ECS. Sediment chlorophyll-a （Chl-a）, phytoplankton-group specifc pigment signatures of diatoms and dinoflagellates, and diatom valve concentrations were determined. The sediment core covered the period from 1961 to 2011 AD. The chlorophyll-a contents ranged from 2.32 to 73 gg/g dry sediment （dw） and averaged 9.81 gg/g dw. Diatom absolute abundance ranged from 29 152 to 177 501 valve/gram （v/g） dw and averaged 72 137 v/g dw. Diatom valve and diatom specific pigment marker concentrations were not significantly correlated. Peridinin increased after the 1980s in line with intensified use of fertilizer and related increases in nutrient inputs into the marine environment. The increased occurrence of dinoflagellate dominance after the 1980s can be mostly explained by the increase in nutrients. However, the contribution of dinoflagellates to total phytoplankton production （Chl-a） decreased during the final decade of this study, probably because of the overwhelming increase in diatom production that corresponded with the construction of the Three Gorges Dam （TGD） and related light availability. Similarly, the mean ratio of fucoxanthin/peridinin for the period from 1982 to 2001 was 6% less than for 1961 to 1982, while the ratio for 2001 to 2011 was 45.3% greater than for 1982 to 2001. The decadal variation in the fucoxanthirdperidinin ratio implies that dinoflagellate production had been gradually increasing until 2001. We suggest that the observed changes can be explained by anthropogenic impacts, such as nutrient loading and dam construction.

Variation in carbon,nitrogen and phosphorus partitioning between above-and belowground biomass along a precipitation gradient at Tibetan Plateau

Precipitation is a potential factor that significantly affects plant nutrient pools by influencing biomass sizes and nutrient concentrations. However, few studies have explicitly dissected carbon(C), nitrogen(N) and phosphorus(P) pools between above- and belowground biomass at the community level along a precipitation gradient. We conducted a transect(approx. 1300 km long) study of Stipa purpurea community in alpine steppe on the Tibet Plateau of China to test the variation of N pool of aboveground biomass/N pool of belowground biomass(AB/BB N) and P pool of aboveground biomass/P pool of belowground biomass(AB/BB P) along a precipitation gradient. The proportion of aboveground biomass decreased significantly from mesic to drier sites. Along the belt transect, the plant N concentration was relatively stable; thus, AB/BB N increased with moisture due to the major influences by above- and belowground biomass allocation. However, P concentration of aboveground biomass decreased significantly with increasing precipitation and AB/BB P did not vary with aridity because of the offset effect of the P concentration and biomass allocation. Precipitation gradients do decouple the N and P pool of a S. purpurea community along a precipitation gradient in alpine steppe. The decreasing of N:P in aboveground biomass in drier regions may indicate much stronger N limitation in more arid area.