仔猪寄养十法

我们称之为寄养的这种技术确实能减少仔猪死亡并提高断奶体重。但如果管理措施跟不上，就根本无效益可言，甚至会造成损失。如果把寄养仅说成是将仔猪从一头母猪转移给另一头母猪饲养未免太简单了事。除了需要熟练的技术这个主要因素之外，在母猪群中寄养处于生命早期阶段...

Evaluation of Chinese Cabbage Sensory Quality and Its Relationship with Contents of Main Nutrient Components

In order to establish a comprehensive evaluation system for quality of Chinese cabbage, 28 Chinese cabbage cultivars or inbreeds were selected as ex- perimental materials to identify the raw and cooked taste and determine the nutrient component contents, and the subjective factors （taste） and objective factors （nutrient component contents） influencing the sensory quality of Chinese cabbage were ana- lyzed by multiple regression and path analysis. The results showed that two regres- sion equations were obtained： yr （raw quality）=0.310 3＋0.254 0xl （juiciness）＋0.176 2 x2 （sweetness）＋0.221 6x3 （crispness）＋0.319 9x4 （flavor）; Yc （cooked quality）=0.204 4＋ 0.250 9 xs （residue）＋0.246 9x6 （cooked sweetness）＋0.182 5x7 （softness）＋0.323 lx8 （cooked flavor）. The path analysis results showed that among the sensory indices, the total coefficients of sweetness and juiciness were 0.445 3 and 0.427 6, respec- tively. It indicated they were the main factors affecting the raw quality of Chinese cab- bage, followed by flavor and crispness. Sweetness, with total coefficient of 0.515 2, showed the greatest effect on the cooked quality of Chinese cabbage, followed by residue, cooked flavor and softness. The effects of nutrient component contents on the sensory quality of Chinese cabbage were further analyzed, and the regression equa- tions were obtained： y, =-32.192 0＋0.389 3xw （moisture content）＋1.169 8x~ （soluble sugar content）; Yc = 7.497 1＋0.732 6xs - 5.668 8x, （organic acid content）-2.176 3x~ （crude fiber content）. The standardized regression coefficients of soluble sugar con- tent were all highest with the value of 0.580 7 in the raw quality regression equa- tion and 0.325 0 in the cooked quality one, indicating that among the six nutrient components, the soluble sugar content was the main factor affecting both raw and cooked quality of Chinese cabbage. This study will provide certain basis for quality evaluation, selection and breeding of high-quality Chinese cabbage.

Nutritional therapy for active Crohn’s disease

Nutritional therapy for active Crohn’s disease (CD) is an underutilised form of treatment in adult patients, though its use is common in the paediatric population. There is evidence that nutritional therapy can effectively induce remission of CD in adult patients. Enteral nutrition therapy is safe and generally well tolerated. Meta-analysis data suggest that corticosteroids are superior to nutritional treatment for induction of remission in active CD. However, the potential side effects of such pharmacotherapy must be taken into consideration. This review examines the evidence for the efficacy of elemental and polymeric diets, and the use of total parenteral nutrition in active CD.

Seasonal changes of bioelements in litter and their potential return to green leaves in five species of tropical dry deciduous forest, western India

The Litter nutrient concentrations of N, P, Ca, Mg, K and Na in mature leaves, twigs and reproductive parts and their relationship between senescent and young leaves were investigated in five forest species： Acacia nilotica, Acacia leucophloea. Tectona grandis, Miliusa tomentosa and Butea monosperma in Indian tropical dry deciduous forest in Western India.. Total dry matter of plant species was recorded and analyzed for N, P, Ca, Mg, K and Na. A. nilotica had the highest concentrations of N in leaf, while ,4. leucophloea had the highest concentrations of Ca and Mg in leaf. The highest concentrations of P in leaf were found in A. nilotica, A. leucophloea and B. monosperma where as lowest in T. grandis and M. tomentosa. No significant differences in K and Na were registered among the species. A marked seasonal variability was ob- served in the concentrations of N, P and K, except for Ca and Mg. Potas- sium is the single element that undergoes leaching and mobilization in all species. Resorped N and P can be used for the production of fresh leaf in the following annual cycle. Nutrient resorption and retranslocation from senescent leaves and litter supports the production of new foliage and increase the fertility of soil.

Gas-solid flow field numerical simulation of different feeding and returning formations of flue-gas circulating fluidized bed

3D Euler double-fluid model was applied and three different feedstocks and reverts formations were simulated. By calculating and analyzing the state of gas and solid fluxion in absorber using three different methods of the feedstocks and reverts in recirculating fluidized bed, described the behavior of gas and solid through the gas-phase velocity, turbulence intensity, gas-solid sliding velocity, and density of particles. The results show that the feedstocks and reverts enters into absorption tower through two symmetrical feedings and are mixed with flue gas. Based on the respective analysis of each model and the com- parison analysis of the three models, this paper drew conclusions. The turbulence intensity of absorption tower is high, gas-solid sliding speed is big, and granule concentration near the axis is high, which has advantages for desulfurization and im- proving the utilization rate of absorbent.

Biomethanisation of Municipal Solid Waste by Anaerobic Fungi Co-culture with Methanogens： An Approach to Energy Recovery

In nature, cellulose, lignocellulose and lignin are major sources of plant biomass; their recycling is indispensable for global carbon cycle. The major portion of the municipal solid waste consists of lignocellulose. The incineration of organic fraction of municipal solid waste （OFMSW） with high moisture content and low calorific value is not environmentally, techno-commercially viable option for energy recovery. Optimization of biomethanisation process is aim to maximize organic waste stabilization at short digestion period with higher energy recovery. The biomethanisation studies, demonstrate co-digestion of substrates improves CH4 yield due to nutrients balance. Fungi are low sensitive to environment, thrive in acidic environment and produces required multi-enzyme, attach to cell envelope and hydrolyze the substrate for energy recovery. Fermentation of cellulose by the monoculture results in the formation of H2, CO2, formate, acetate, lactate, succinate, and ethanol. In co-cultures with Methanobacterium, H2 and formate reduction indicates it＇s utilized in CH4 production. Engineered co-culture of microorganisms is essential for the heterogeneous complex organic substrate degradation for extraction of unutilized energy fraction of biomass, as potential source of energy.

Fuzzy Control of Nitrate Recirculation and External Carbon Addition in A/O Nitrogen Removal Process

Nitrogen and phosphorous concentrations of effluent water must be taken into account for the design and operation of wastewater treatment plants. In addition, the requirement for effluent quality is becoming strict. Therefore, intelligent control approaches are recently required in removing biological nutrient. In this study, fuzzy control has been successfully applied to improve the nitrogen removal. Experimental results showed that a close relationship between nitrate concentration and oxidation-reduction potential (ORP) at the end of anoxic zone was found for anoxic/oxic (A/O) nitrogen removal process treating synthetic wastewater. ORP can be used as online fuzzy control parameter of nitrate recirculation and external carbon addition. The established fuzzy logic controller that includes two inputs and one output can maintain ORP value at - 86 mV and - 90 mV by adjusting the nitrate recirculation flow and external carbon dosage respectively to realize the optimal control of nitrogen removal, improving the effluent quality and reducing the operating cost.

DDT and Its Metabolites in Fresh Water Fish Samples

Twenty two fresh water fish samples namely Puntius sarana （Shawrputi）, Cyprinus carpio （Karp）, Oreochromis niloticos （Telapia）, Channa punctatus （Taki）, Wallogonia attu （Boal）, Eutropiichthys vacha （Bacha）, Macrognathus aculiatus （Baim）, Ailia coila （Kajoli）, Mystus cavasisus（Gulsa）, Ompok pabda （Pabdha）, Corica soborna （Kachki）, Mystus vittatus （Tengra）, Glossogobius giuris （Baila）, Macrobrachium malcolmsli （Chingri）, Amblypharyngodon microlepis （Mola）, Anabas testudineus （Koi）, Macrognathus aculiatus （Baim）, Channa striatus （Shole）, Heteropnueste fossilis （Shing）, Puntius sophore （Small Puti） and Pseudambassis ranga （Telapia） were collected from two rivers and one cultured fish pond. The samples were extracted by QuEChERS method, cleaned up with conc. H2SO4 treatment and cleaned extracts were analyzed by GC-ECD. Small size cultured rui fish sample which did show detectable amount of DDT and its metabohtes was used for the recovery experiments. Percent recovery was found to be in the range of 70%-113%. Amount of total DDTs were found to be 54.34, 48.81, 62.09, 54.72,78.81, 60.07, 47.0, 42.7, 26.31, 10.36, 25.32, 12.96, 20.10, 12.78, 17.65, and 4.71, 8.58, 11.3 and 19.01 ng/g in gulsa, pabhda, baila, bacha, baim, small purl, tengra, chanda, kachki, boal, taki, chingri, mola, shole, shing, koi, swarpurl, karp and telapia fish samples, respectively. However, the residual amounts of DDTs in all the fish samples were below maximum residue limit （MRL of DDTs in fish 5.0 mg/kg） according to Codex Alimentarius Commission. The ratios of 4,4＇-DDT/DDTs were in the range of 0.03-0.44 which indicated that exposure to DDT is not due to recent use.

Functional lipidomics in patients on home parenteral nutrition: Effect of lipid emulsions

To investigate the fatty acid-based functional lipidomics of patients on long-term home parenteral nutrition receiving different intravenous lipid emulsions. METHODSA cross-sectional comparative study was carried out on 3 groups of adults on home parenteral nutrition (HPN), receiving an HPN admixture containing an olive-soybean oil-based intravenous lipid emulsion (IVLE) (OO-IVLE; n = 15), a soybean- medium-chain triacylglycerol-olive-fish oil-based IVLE (SMOF-IVLE; n = 8) or HPN without IVLE (No-IVLE; n = 8) and 42 healthy controls (HCs). The inclusion criteria were: duration of HPN ≥ 3 mo, current HPN admixtures ≥ 2 mo and HPN infusions ≥ 2/wk. Blood samples were drawn 4-6 h after the discontinuation of the overnight HPN infusion. The functional lipidomics panel included: the red blood cell (RBC) fatty acid (FA) profile, molecular biomarkers [membrane fluidity: saturated/monounsaturated FA ratio = saturated fatty acid (SFA)/monounsaturated fatty acid (MUFA) index; inflammatory risk: n-6/n-3 polyunsaturated fatty acid (PUFA) ratio = n-6/n-3 index; cardiovascular risk: sum of n-3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) = n-3 index; free radical stress: sum of FA trans isomers = %trans index] and FA pathway enzyme activity estimate (delta-9-desaturase = D9D; delta-6-desaturase = D6D; delta-5-desaturase = D5D; elongase = ELO). Statistics were carried out using nonparametric tests. The amount of each FA was calculated as a percentage of the total FA content (relative%). RESULTSIn the OO-IVLE group, the percentage of oleic acid in the RBCs was positively correlated with the weekly load of OO-IVLE (r = 0.540, P = 0.043). In the SMOF-IVLE cohort, the RBC membrane EPA and DHA were positively correlated with the daily amount of SMOF-IVLE (r = 0.751, P = 0.044) and the number of HPN infusions per week (r = 0.753; P = 0.046), respectively. The SMOF-IVLE group showed the highest EPA and DHA and the lowest arachidonic acid percentages (P < 0.001). The RBC membrane linoleic acid content was lower, and oleic and vaccenic acids were higher in all the HPN groups in comparison to the HCs. Vaccenic acid was positively correlated with the weekly HPN load of glucose in both the OO-IVLE (r = 0.716; P = 0.007) and the SMOF-IVLE (r = 0.732; P = 0.053) groups. The estimated activity of D9D was higher in all the HPN groups than in the HCs (P < 0.001). The estimated activity of D5D was lower in the SMOF-IVLE group than in the HCs (P = 0.013). The SFA/MUFA ratio was lower in all the HPN groups than in the HCs (P < 0.001). The n-6/n-3 index was lower and the n-3 index was higher in the SMOF-IVLE group in comparison to the HCs and to the other HPN groups (P < 0.001). The %trans index did not differ among the four groups. CONCLUSIONThe FA profile of IVLEs significantly influenced the cell membrane functional lipidomics. The amount of glucose in the HPN may play a relevant role, mediated by the insulin regulation of the FA pathway enzyme activities.

Regression Analysis of Nutrient Elements between Soil and Tobacco Leaves and Their Influences on Aroma Quality of Flue-cured Tobacco

This study aimed to analyze the relationship between nutrient elements K, Ca, Mg, Cu, Mn, Zn and Fe in tobacco-planting soils and tobacco leaves from six main tobacco-producing areas, and to investigate the influences of these elements on chemical composition and aroma components in tobacco leaves. Results showed that there were certain relationship between contents of nutrient elements in tobacco-planting soils and contents of corresponding elements in tobacco leaves; various elements exhibited different influences on the aroma quality of flue-cured tobacco. Based on the actual situation of nutrient contents in soils from different tobaccoproducing areas, contents of various elements in tobacco leaves should be regulated by soil fertilization and foliar spraying, thereby improving the aroma quality of flue-cured tobacco.

Effects of Stocking Density on Water Quality,Growth and Economic Benefits of Chinese Softshelled Turtle Pelodiscus sinensis in Ponds

The Chinese soft-shelled turtle Pelodiscus sinensis is a high-valued freshwater species cultured in China.This study investigated the effects of stocking density on water quality,growth performance and economic return of Pelodiscus sinensis cultured in ponds.P.sinensis were stocked at densities of 1 ind./m^2(LD:low stocking density) and 2 ind./m^2(HD:high stocking density) in 3 000-m^2 ponds,with three replicate ponds for each density.P.sinensis juveniles were fed with a commercial dry pellet feed of 46% crude protein and minced fillet of silver carp ans cultured for 122 days.The results showed that the levels of total nitrogen(TN),total phosphorous(TP),Chlorophyll-a(Chl.a) and turbidity in LD treatment were significantly lower than those in HD treatment(P<0.05).The mean TN and TP concentration in LD treatment was 29.3% and 35.7% lower compared to the HD treatment at the end of the experiment,respectively.Mean survival rates,final weight,average growth rates and PER were significantly higher in LD treatment compared with the HD treatment(P<0.05),respectively.Production was significantly affected by stocking density,which was higher in HD treatment,but the net income was higher in LD treatment.The results suggest that turtles with mean weight 55.6 g rearing at a low stocking density(1 ind./m^2) in ponds had a positive effect on overall economic return and was effective at improving turtle growth performance and water quality.

Comparison of Artificial Neural Networks,Geographically Weighted Regression and Cokriging Methods for Predicting the Spatial Distribution of Soil Macronutrients(N,P,and K)

Soil macronutrients(i.e. nitrogen(N), phosphorus(P), and potassium(K)) are important soils components and knowing the spatial distribution of these parameters are necessary at precision agriculture. The purpose of this study was to evaluate the feasibility of different methods such as artificial neural networks(ANN) and two geostatistical methods(geographically weighted regression(GWR) and cokriging(CK)) to estimate N, P and K contents. For this purpose, soil samples were taken from topsoil(0–30 cm) at 106 points and analyzed for their chemical and physical parameters. These data were divided into calibration(n = 84) and validation(n = 22). Chemical and physical variables including clay, p H and organic carbon(OC) were used as auxiliary soil variables to estimate the N, P and K contents. Results showed that the ANN model(with coefficient of determination R^2 = 0.922 and root mean square error RMSE = 0.0079%) was more accurate compared to the CK model(with R^2 = 0.612 and RMSE = 0.0094%), and the GWR model(with R^2 = 0.872 and RMSE = 0.0089%) to estimate the N variable. The ANN model estimated the P with the RMSE of 3.630 ppm, which was respectively 28.93% and 20.00% less than the RMSE of 4.680 ppm and 4.357 ppm from the CK and GWR models. The estimated K by CK, GWR and ANN models have the RMSE of 76.794 ppm, 75.790 ppm and 52.484 ppm. Results indicated that the performance of the CK model for estimation of macro nutrients(N, P and K) was slightly lower than the GWR model. Also, the accuracy of the ANN model was higher than CK and GWR models, which proved to be more effective and reliable methods for estimating macro nutrients.

Investigation and prediction of enteral nutrition problems after percutaneous endoscopic gastrostomy

AIM： To investigate and predict enteral nutrition problems after percutaneous endoscopic gastrostomy （PEG）. METHODS： We retrospectively analyzed data for 252 out of 285 patients who underwent PEG at our hospital from 1999 to 2008 after PEG were defined as： Enteral nutrition problems （1） patients who required ≥ 1 mo after surgery to switch to complete enteral nutrition, or who required additional parenteral alimentation continuously; or （2） patients who abandoned switching to enteral nutrition using the gastrostoma and employed other nutritional methods. We attempted to identify the predictors of problem cases by using a logistic regression analysis that examined the patients＇ backgrounds and the specific causes that led to their problems. RESULTS： Mean age of the patients was 75 years, and in general, their body weight was low and their overall condition was markedly poor. Blood testing revealed that patients tended to be anemic and malnourished. A total of 44 patients （17.5%） were diagnosed as having enteral nutrition problems after PEG. Major causes of the problems included pneumonia, acute enterocolitis （often Clostridium difficile-related）, paralytic ileus and biliary tract infection. A multivariate analysis identified the following independent predictors for problem cases： （1） enteral nutrition before gastrectomy （a risk reduction factor）; （2） presence of esophageal hiatal hernia; （3） past history of paralytic ileus; and （4） presence of chronic renal dysfunction. CONCLUSION： Enteral nutrition problems after PEG occurred at a comparatively high rate. Patient background analysis elucidated four predictive factors for the problem cases.

Interaction between Dairy Yeasts and Lactobacillus rhamnosus GG in Milk

The presence of Geotrichum candidum in fresh cheese is considered to be a contaminant and may lead to the product spoilage. The oxidative yeast Candida maltosa firstly isolated from the spoiled fruit yoghurt surface in Slovakia belongs to the yeast contaminants of fermented dairy products. The effect of the cultivation temperature and the presence of Lactobacillus rhamnosus GG on the growth of dairy spoilage yeasts in ultrapasteurized milk was studied. Addition of Lb. rhamnosus GG in milk caused partial inhibition of the yeast growth dynamics in milk. The water activity transformation of Gibson model after the temperature modification （Tw） was applied to model growth dynamics of G. candidum in pure and mixed culture, respectively： In μ_Gc=-5.0376＋2.7281 Tw-0.4217Tw^2, lnμ_CC_LGG=-6.0033＋3.2996Tw-0.5553Tw^2. The effect of different Lb. rhamnosus GG addition and the incubation temperature on the C. maltosa growth dynamics was analyzed by linear regression methodology and described by using following equations： lnGr1=-5.3674＋0.2341T＋0.2599N0-0.0032T^2-0.0492N0^2-0.0068TN0 and lnGr11=-9.5457-0.249T＋2.3823N0 ＋0.0099T^2-0.2324N0^2＋0.0098TN0 Based on the principles of predictive microbiology, the mutual microbial interactions and potential application of the lactobacillus strains in food protection are discussed.

Research on the Trend of Modem Interior Design Education Reform from the Perspectives of Aesthetics and Traditional Regression

In this paper, we conduct research on the trend of modern interior design education reform from the perspectives of aesthetics and traditional regression. Professional interior design technology is to adapt to the needs of economic development of practical talents in the central plains, with the spirit of the ＂seeking truth from facts＂ , pinpoint the target of profession fostering, established the reasonable personnel training mode, trying to explore suitable for the market need of professional personnel training mode and practical teaching methods, architecture art and design professional teaching system in higher vocational colleges. Interior design professional teaching reform goal, the guiding ideology, clear, clearer thinking pay attention to professional skills and professional quality education, skills, for body, quality as the soul. Our research starts from the basic analysis of aesthetics and traditional regression to propose the novel educational paradigm that is innovative.

Biomass allocation between leaf and stem regulates community-level plant nutrient resorption efficiency response to nitrogen and phosphorus additions in a temperate wetland of Northeast China

Aims Nutrient resorption is a crucial component of plant nutrient use strategy,yet the controls on the responses of community-level nutrient resorption to altered nutrient availability remain unclear.Here,we addressed two questions:(1)Did leaf and stem nutrient resorption respond consistently to increased nutrient availability?(2)Was community-level plant nutrient resorption response after nutrient enrichment driven by the intraspecific plasticity in plant nutrient resorption or by altered species composition?Methods We investigated the changes in aboveground biomass,and leaf and stem nutrient resorption of individual species after 3-year nitrogen(N)and phosphorus(P)additions,and assessed community-level nutrient resorption response to 3-year nutrient additions in a graminoid-dominated temperate wetland,Northeast China.Important Findings For both leaves and stems,N and P additions did not affect nutrient resorption efficiency,but they decreased respective nutrient resorption proficiency.Similarly,community-level N and P resorption proficiency declined with respective nutrient addition.Community-level N and P resorption efficiency was reduced by N addition primarily due to altered community composition and declined leaf:stem ratio.These results suggest that leaf and stem nutrient resorption processes exhibit consistent responses to increasing nutrient availability in the temperate wetland.These findings highlight the importance of altered species composition and biomass allocation between leaf and stem in driving community-level nutrient resorption response to nutrient enrichment.

Nitrogen and phosphorus translocation of forest floor mosses as affected by a pulse of these nutrients

Aims Mosses are dominant in many ecosystems where nutrients from deposition are one of the main nutrient sources.However,it is difficult to evaluate mosses’role in nutrient cycling without knowledge of how mosses use deposited nutrient inputs.To fill this gap,the present study aims to investigate:(i)how nitrogen(N)and phosphorus(P)concentrations of new-grown segments change along a gradient of N or P amount in a pulse treatment?(ii)how do a pulse of major nutrient(N or P)affect N or P translocation rate along a moss shoot?and(iii)to what extent do N or P translocation rates link to nutrient status of the new-grown segments of mosses?Methods We measured N and P concentrations of segments with different ages in two dominant forest floor mosses,Actinothuidium hookeri and Hylocomium splendens,on 8 days and 1 year after N and P pulse treatment with an in situ experiment in a subalpine fir forest in eastern Tibetan Plateau.Important Findings Both mosses were efficient in taking up nutrients from a pulse of either N or P.Nitrogen and P concentrations of new-grown segments were affected by nutrient pulse treatments.These N and P concentration changes were attributed to the initial N and P concentration of the young segments harvested 8 days after nutrient pulse treatments,suggesting that the captured nutrients were reallocated to the new-grown segments via translocation,which was largely controlled by a source-sink relationship.While no significant relationship was found between N translocation rate and N:P ratio of the new-grown segments,P translocation rate explained 21%-23%of the variance of N:P ratio of the new-grown segments,implying importance of P transport in supporting the new-grown sections.These results suggest that nutrient(N,P)translocation is a key process for mosses to utilize intermittent nutrient supply,and thus make mosses an important nutrient pool of the ecosystem.

Comparison of outcomes following three surgical techniques for patients with severe jejunoileal atresia

Background:Severe jejunoileal atresia is associated with prolonged parenteral nutrition,higher mortality and secondary surgery.However,the ideal surgical management of this condition remains controversial.This study aimed to compare the outcomes of patients with severe jejunoileal atresia treated by three different procedures.Methods:From January 2007 to December 2016,105 neonates with severe jejunoileal atresia were retrospectively reviewed.Of these,42 patients(40.0%)underwent the Bishop–Koop procedure(BK group),49(46.7%)underwent primary anastomosis(PA group)and 14(13.3%)underwent Mikulicz double-barreled ileostomy(DB group).Demographics,treatment and outcomes including mortality,morbidity and nutrition status were reviewed and were compared among the three groups.Results:The total mortality rate was 6.7%,showing no statistical difference among the three groups(P=0.164).The BK group had the lowest post-operative complication rate(33.3%vs 65.3%for the PA group and 71.4%for the DB group,P=0.003)and re-operation rate(4.8%vs 38.8%for the PA group and 14.3%for the DB group,P<0.001).Compared with the BK group,the PA group showed a positive correlation with the complication rate and re-operation rate,with an odds ratio of 4.15[95%confidence interval(CI):1.57,10.96]and 12.78(95%CI:2.58,63.29),respectively.The DB group showed a positive correlation with the complication rate when compared with the BK group,with an odds ratio of 7.73(95%CI:1.67,35.72).The weight-for-age Z-score at stoma closure was–1.22(95%CI:–1.91,–0.54)in the BK group and–2.84(95%CI:–4.28,–1.40)in the DB group(P=0.039).Conclusions:The Bishop–Koop procedure for severe jejunoileal atresia had a low complication rate and re-operation rate,and the nutrition status at stoma closure was superior to double-barreled enterostomy.The Bishop–Koop procedure seems to be an appropriate choice for severe jejunoileal atresia.

Effects of defoliation timing on plant nutrient resorption and hay production in a semi-arid steppe

Aims Nutrient resorption is a key plant nutrient conservation strategy,and its response to environmental and management changes is linked to nutrient cycling and production of ecosystems.Defoliation is a major pathway of mowing affecting plant nutrient resorption and production in grasslands,while the effect of defoliation timing has not been unexplored.The aim of this study was to examine the effect of defoliation timing on plant nutrient resorption and production in a steppe ecosystem.Methods We conducted a field experiment in a semi-arid steppe of Inner Mongolia including four treatments:early defoliation,peak defoliation,late defoliation and non-defoliation.We measured plant nitrogen(N)and phosphorus(P)resorption at species and community levels,and quantified plant N and P fluxes in resorption,litter return and hay output.Plant production in the mowing system was assessed by hay production and quality.Important Findings Peak and late defoliation,but not early defoliation,reduced plant community N and P resorption proficiency;and late defoliation reduced N resorption efficiency but not P resorption efficiency.Peak and late defoliation,but not early defoliation,reduced plant nutrient resorption flux and litter nutrient return flux.Defoliation timing did not alter root nutrient accumulation as nutrient uptake from soil likely compensated the deficit of nutrient resorption.Peak defoliation had the highest hay production and quality,while early defoliation had the lowest.Our results provide new insights into the nutrient cycling in mowing grassland,and imply that the mowing timing can be used as a tool to mediate the balanee between conservation and production of steppes,and the early mowing before plant peak biomass period is recommended for conservation of the steppes while keeping sustainable pastoral production.

Pedotransfer Functions for Estimating Soil Bulk Density:A Case Study in the Three-River Headwater Region of Qinghai Province,China

Bulk density(BD) is an important soil physical property and has significant effect on soil water conservation function. Indirect methods, which are called pedotransfer functions(PTFs), have replaced direct measurement and can acquire the missing data of BD during routine soil surveys. In this study, multiple linear regression(MLR) and artificial neuron network(ANN) methods were used to develop PTFs for predicting BD from soil organic carbon(OC), texture and depth in the Three-River Headwater region of Qinghai Province, China. The performances of the developed PTFs were compared with 14 published PTFs using four indexes, the mean error(ME), standard deviation error(SDE), root mean squared error(RMSE) and coefficient of determination(R^2). Results showed that the performances of published PTFs developed using exponential regression were better than those developed using linear regression from OC. Alexander(1980)-B, Alexander(1980)-A and Manrique and Jones(1991)-B PTFs, which had good predictions, could be applied for the soils in the study area. The PTFs developed using MLR(MLR-PTFs) and ANN(ANN-PTFs) had better soil BD predictions than most of published PTFs. The ANN-PTFs had better performances than the MLR-PTFs and their performances could be improved when soil texture and depth were added as predictor variables. The idea of developing PTFs for predicting soil BD in the study area could provide reference for other areas and the results could lay foundation for the estimation of soil water retention and carbon pool.