Borneol-Modified Schisandrin B Micelles Cross the Blood-Brain Barrier To Treat Alzheimer's Disease in Aged Mice.

Objective: Schisandrin B (Sch B) is a bioactive dibenzocyclooctadiene derizative that is prevalent in the fruit of Schisandra chinensis. Numerous studies have demonstrated that Sch B has a neuroprotective action by reducing oxidative stress and effectively preventing inflammation. It follows that Sch B is a potential treatment for Alzheimer's disease (AD). However, the drug's solubility, bioavailability, and lower permeability of the blood-brain barrier (BBB) can all reduce its efficacy during the therapy process. Therefore, this study constructed borneol-modified schisandrin B micelles (Bor-Sch B-Ms), which increase brain targeting by accurately delivering medications to the brain, effectively improving bioavailability. High therapeutic efficacy has been achieved at the pathological site. Methods: Bor-Sch B-Ms were prepared using the thin film dispersion approach in this article. On the one hand, to observe the targeting effect of borneol, we constructed a blood-brain barrier (BBB) model in vitro and studied the ability of micelles to cross the BBB. On the other hand, the distribution of micelle drugs and their related pharmacological effects on neuroinflammation, oxidative stress, and neuronal damage were studied through in vivo administration in mice. Results: In vitro studies have demonstrated that the drug uptake of bEnd.3 cells was increased by the borneol alteration on the surface of the nano micelles, implying that Bor-Sch B-Ms can promote the therapeutic effect of N2a cells. This could result in more medicines entering the BBB. In addition, in vivo studies revealed that the distribution and circulation time of medications in the brain tissue were significantly higher than those in other groups, making it more suitable for the treatment of central nervous system diseases. Conclusion: As a novel nanodrug delivery system, borneol modified schisandrin B micelles have promising research prospects in the treatment of Alzheimer's disease.

Photosynthetic System Based on a Polyoxometalate-Based Dehydrated Metal-Organic Framework for Nitrogen Fixation.

In nature, biological nitrogen fixation is accomplished through the π-back-bonding mechanism of nitrogenase, which poses significant challenges for mimic artificial systems, thanks to the activation barrier associated with the N≡N bond. Consequently, this motivates us to develop efficient and reusable photocatalysts for artificial nitrogen fixation under mild conditions. We employ a charge-assisted self-assembly process toward encapsulating one polyoxometalate (POM) within a dehydrated Zr-based metal-organic framework (d-UiO-66) exhibiting nitrogen photofixation activities, thereby constructing an enzyme-mimicking photocatalyst. The dehydration of d-UiO-66 is favorable for facilitating nitrogen chemisorption and activation via the unpaired d-orbital electron at the [Zr6O6] cluster. The incorporation of POM guests enhanced the charge separation in the composites, thereby facilitating the transfer of photoexcited electrons into the π* antibonding orbital of chemisorbed N2 for efficient nitrogen fixation. Simultaneously, the catalytic efficiency of SiW9Fe3@d-UiO-66 is enhanced by 9.0 times compared to that of d-UiO-66. Moreover, SiW9Fe3@d-UiO-66 exhibits an apparent quantum efficiency (AQE) of 0.254% at 550 nm. The tactics of "working-in-tandem" achieved by POMs and d-UiO-66 are extremely vital for enhancing artificial ammonia synthesis. This study presents a paradigm for the development of an efficient artificial catalyst for nitrogen photofixation, aiming to mimic the process of biological nitrogen fixation.

Density and row spacing of short-season cotton suitable for machine picking in the cotton region of Yellow River Basin.

To determine the suitable planting density and row spacing of short-season cotton suitable for machine picking in the Yellow River Basin of China, we conducted a two-year field experiment in Dezhou during 2018-2019. The experiment followed a split-plot design, with planting density (82500 plants·hm-2 and 112500 plants·hm-2) as the main plots and row spacing (equal row spacing of 76 cm, wide-narrow row spacing of 66 cm+10 cm, equal row spacing of 60 cm) as the subplots. We examined the effects of planting density and row spacing on growth and development, canopy structure, seed cotton yield and fiber quality of short-season cotton. The results showed that plant height and LAI under high density treatment were significantly greater than those under low density treatment. The transmittance of the bottom layer was significantly lower than under low density treatment. Plant height under 76 cm equal row spacing was significantly higher than that under 60 cm equal row spacing, while that under wide-narrow row spacing (66 cm +10 cm) was significantly smaller than that under 60 cm equal row spacing in peak bolling stage. The effects of row spacing on LAI varied between the two years, densities, and growth stages. On the whole, the LAI under the wide-narrow row spacing (66 cm+10 cm) was higher, with the curve declining gently after the peak, and it was higher than that in the two cases of equal row spacing in the harvest time. The change in transmittance of the bottom layer presented the opposite trend. Density, row spacing, and their interaction had significant effects on seed cotton yield and its components. In both years, seed cotton yield was the highest (3832 kg·hm-2 in 2018, 3235 kg·hm-2 in 2019) under wide-narrow row spacing (66 cm+10 cm), and it was more stable at high densities. Fiber quality was less affected by density and row spacing. To sum up, the optimal density and row spacing of short-season cotton were as follows: density with 112500 plants·hm-2 and wide-narrow row spacing (66 cm+10 cm).

Heteropoly Blue/Protonation-Defective Graphitic Carbon Nitride Heterojunction for the Photo-Driven Nitrogen Reduction Reaction.

The establishment of a heterojunction is a crucial strategy to design highly effective nonnoble metal nanocatalysts for the photocatalytic nitrogen reduction reaction (PNRR). Heteropoly blues (r-POMs) can act as electron-transfer mediators in PNRR, but its agglomeration limits the further promotion of PNRR productivity. In this work, we construct a protonation-modified surface of N-vacancy g-C3N4 (HV-C3N4), achieving the high dispersion of r-POMs via the surface modification strategy. Enlightened by the synergy effect of the nitrogenase, r-POMs were anchored onto HV-C3N4 nanosheets through an electrostatic self-assembly method for preparing r-POMs-based protonation-defective graphitic carbonitride (HV-C3N4/r-POMs). As an electron donor, r-PW12 can match with the energy level of HV-C3N4 to build a heterojunction. The electron redistribution of the heterojunction facilitates the optimization of the electronic structure for enhancing the performance of PNRR. HV-C3N4/r-PW12 exhibits the best PNRR efficiency of 171.4 µmol L-1 h-1, which is boosted by 94.39% (HV-C3N4) and 86.98% (r-PW12). The isotope 15NH4+ experiment proves that ammonia is derived from N2, not carbon nitride. This study opens up a crucial view to achieve the high dispersion of r-POMs nanoparticles and develop high-efficiency nonnoble metal photocatalysts for the PNRR.

Astragaloside-IV regulates endoplasmic reticulum stress-mediated neuronal apoptosis in a murine model of Parkinson's disease via the lincRNA-p21/CHOP pathway.

OBJECTIVES: Astragaloside-IV (AS-IV) protects the nerve cells of Parkinson's disease (PD) from damage. Long non-coding RNA (lincRNA) has been found to be important for many diseases. Lincnra-p21 is abnormally expressed in PD. The purpose of this study was to investigate whether Astragaloside-IV (AS-IV) affects endoplasmic reticulum stress (ERS)-induced neuronal apoptosis in PD, and its possible mechanisms. METHODS: The PD mouse model was established via injecting 1-methyl-4-phenyl-1, 2, 3, 6- tetrahydropyridine (MPTP) and the PD cell model was established via inducing the MN9D cell line with 1-methyl-4-pehnyl-pyridine (MPP+). The behavioral testing of PD model mice was tested after AS-IV treatment and PD-related lincRNAs expression were detected by qRT-PCR. After treatment of PD model cells with AS-IV, lincRNA-p21 expression was detected by qRT-PCR, and cell viability and apoptosis were detected by MTT assay and flow cytometry, respectively. The binding of lincRNA-p21 to C/EBP-homologous (CHOP) protein was investigated by RNA immunoprecipitation and RNA pull-down, and the effect of lincRNA-p21 on the ubiquitination of CHOP protein was examined by ubiquitination assay. The role of lincRNA-p21 in PD model was studied by cell transfection. RESULTS: In PD mice, AS-IV can improve the behavior of mice and significantly inhibit expression of lincRNA-p21. Similarly, AS-IV can obviously restrain the expression of lincRNA-p21 in PD cells, and obviously elevated cell viability and restrained apoptosis. LincRNA-p21 is able to bind to CHOP protein. Further studies showed that restraint of lincRNA-p21 expression can facilitate ubiquitination of CHOP and accelerate its protein degradation. In AS-IV-treated PD model cells, overexpression of lincRNA-p21 lessened cell viability and facilitated apoptosis, whereas low expression of CHOP reversed this result. CONCLUSION: In this study, we found that AS-IV can lessen the expression of CHOP protein by restraining the expression of lincRNA-p21 in the PD model, thereby inhibiting neuronal apoptosis.

Reduced State of the Graphene Oxide@Polyoxometalate Nanocatalyst Achieving High-Efficiency Nitrogen Fixation under Light Driving Conditions.

The nitrogen (N2) reduction to generate ammonia (NH3) is a prerequisite for inputting fixed nitrogen (N) into a global biogeochemical cycle. Developing highly efficient photocatalysts for N2 fixation under mild conditions is still a challenge. Herein, we first report three kinds of reduction states of graphene oxide (GO)@polyoxometalate (POM) composite nanomaterials, which have outstanding photocatalytic N2 fixation activities in pure water without any other electronic sacrificial agents and cocatalysts at atmospheric pressure and room temperature. A lot of experiments show that the remarkable photocatalytic N2 fixation performance of these three nanocatalysts is due to three factors that doping the reduced POMs (also called heteropoly blues) into the reduce GO (rGO) reduces the aggregation state of rGO (from 5 to 2 nm), resulting in rGO exposing many active sites to enhance the N2 adsorption amount, these three nanocatalysts possess a wide absorption spectrum and strong reducibility, which facilitate absorb light energy exciting abundant photoelectrons to activate N2, and rGO can effectively suppress the electrons recombination and rapidly transfer electrons to the absorbed N2 to accelerate NH3 production. Among them, r-GO@H5[PMo10V2O40] (PMo10V2) exhibits the highest NH3 generation efficiency of 130.3 µmol L-1 h-1, which is improved by 65.9 and 97.3% compared to the reduced PMo10V2 (rPMo10V2) and PMo10V2. Introduction of POMs provides a new perspective in the design of high-performance photocatalytic N2 fixation nanomaterials.

Abiotic and biotic controls on dynamics of labile phosphorus fractions in calcareous soils under agricultural cultivation.

Soil labile inorganic and organic phosphorus (L-Pi and L-Po) extracted by NaHCO3 are potentially important sources of plant-available P. Their availability is strongly affected by soil physiochemical and biological properties. Here we conducted a field study in an arid region of northwestern China to investigate how L-Pi and L-Po dynamics are affected by changes in physiochemical and biological variables caused by agricultural cultivation of calcareous soils. Topsoils were sampled at multiple sites from natural calcareous grasslands and cultivated farmlands of different ages (32-40 vs. 90-100 years) that had been converted from natural grasslands. We measured L-Pi and L-Po concentrations and a set of key physiochemical (soil pH, concentrations of base cations (K+ + Na+ + Ca2+ + Mg2+), acid anions (Cl- + NO3- + SO42-), nitrate and ammonium nitrogen (N), organic carbon, and total P) and biological (soil microbial biomass carbon (Cmic), alkaline phosphatase activity (Aalp), and abundances of soil macroinvertebrates (Amacro) and mesoinvertebrates (Ameso)) variables. The concentration of L-Pi and L-Po was 484% and 128% higher and their proportion in the total P content was 354% and 78% higher in young farmland soils, whereas L-Pi and L-Po concentrations were 583% and 423% higher and their proportions were 353% and 240% higher in old farmland soils compared to grassland soils. Increases in L-Pi and L-Po attributable to soil P release may be driven by crucial processes of soil acidification-induced phosphate dissolution and soil biota-driven Po mineralisation. Path analyses revealed that L-Pi and L-Po dynamics were shaped by the complex interactions among five key controlling factors, soil pH, nitrate-N, Ameso, Cmic, and Aalp, involved in these crucial processes. We conclude that cultivation of calcareous soils significantly increases the availability of L-Pi and L-Po, emphasizing the importance of this land-use change as a regulator of P cycling in calcareous soils.

Association of five SNPs at the PARK16 locus as a susceptibility locus with Parkinson's disease for forensic application.

To investigate the association of five SNPs (rs823083, rs708723, rs4951261, rs823076 and rs16856110) at the PARK16 locus with Parkinson's disease (PD), and to potentiate its forensic application. The genomic DNAs of 215 PD patients and 212 matched controls from the northern Han Chinese population were amplified in two independent PCR systems and subsequently genotyped by digestion with the three endonucleases (Hinf I, Nco I and Msp I ). The genetic parameters and association studies were carried out with SPSS 13.0, Haploview version 4.2 and PLINK 1.07 softwares. We detected accurately all genotypes in the five SNPs with multiplex PCR-RFLP and mismatched multiplex PCR-RFLP techniques. The genotypes of four SNPs, except for rs823083, were in Hardy-Weinberg equilibrium. The four SNPs, rs16856110, rs4951261, rs708723 and rs823076, which were in linkage equilibrium, should not be associated with PD (P-values ranging from 0.077 to 0.544). The SNPs investigated at the PARK16 locus were not found to be involved in PD-associated blocks in the northern Han Chinese population. The allele distributions of rs708723, rs4951261, rs823076 and rs16856110 in the northern Han Chinese population can be highly polymorphic, which can be applied to genetic analysis and forensic practices.

[Influence of soil salinization on soil animal community in an arid oasis of middle Heihe River basin].

An investigation was conducted on the status of soil salinization and the structure of soil animal community across six land use/cover types in an arid oasis of middle Heihe River basin, and the methods of redundancy analysis, regression analysis, and path analysis were adopted to analyze the responses of the soil animal community under different land use/cover types and different management modes to the various status of soil salinization. The six land use/cover types were 21-year old shrub land without irrigation and fertilization, 28-year old poplar and 33-year-old pine plantations with irrigation, 27- and 100-year-old farmlands with irrigation and fertilization, and natural grassland, from which all the other five land use/cover types were converted. The results demonstrated that land cover change in the absence of management practices did not lead to a significant change in the abundance and group richness of the soil animal community, while land cover change in the presence of management practices resulted in a significant change in the soil animal community. The evolvement of the soil animal community structure was co-affected by soil pH, soluble salt content, and Na+, Cl, HCO3-, and Mg2+ concentrations, among which, soil soluble salt and Na had the greatest contribution, being the key affecting factors. The abundance and group richness of the soil animal community had significant negative exponential correlations with soil soluble salt content and Na+ concentration, and significant quadratic correlations with soil Mg2+ and HCO3- concentrations. The calculated ecological threshold values of soil Mg2+ and HCO3- concentrations for the abundance and group richness of the soil animal community were 38.7-39.4 mg x kg(-1) and 324.9-335.3 mg x kg(-1), at which, the abundance and group richness reached their peaks 40-43 individuals x m(-2) and 13-14 families x m(-2), respectively. When the Mg2+ and HCO3- concentrations increased further, the abundance and group richness decreased.

[Distribution specificity of human fucosyltransferase 5 and its expression and localization in spermatids].

OBJECTIVE: To investigate distribution specificity of human fucosyltransferase 5 (FUT5) as well as its expression and localization in spermatids. METHODS: Human semen, vaginal swab, saliva and venous blood from healthy individuals were collected. The spermatids were isolated and the spermatid membrane protein was then extracted. Expression levels of FUT5 from human spermatid membrane, seminal plasma, vaginal fluid, saliva and serum were detected by immunoblotting technique. The expression and localization of FUT5 in spermatids were analyzed by immunofluorescent method. RESULTS: Immunoblotting technique showed that FUT5 was expressed on spermatid membranes and in serum, but not in seminal plasma, vaginal fluid and saliva. The expressed FUT5 on spermatids was mostly localized on head of spermatids by fluorescent microscopy, suggesting that there was certain amount of FUT5 on human spermatid membrane, and the spermatids might be isolated from mixed stains with vaginal fluid by antigen-antibody reaction. CONCLUSION: Human FUT5 shows a characteristic distribution specificity, and this feature may be used for identification of mixed stain involved in criminal sexual offence in future forensic practice.

Lack of association between three single nucleotide polymorphisms in the PARK9, PARK15, and BST1 genes and Parkinson's disease in the northern Han Chinese population.

BACKGROUND: Parkinson's disease (PD) is an autosomally inherited neurodegenerative disease in elderly people. The etiology of PD has long been thought to be associated with both genetic and environmental factors. To explore potential genetic risk factors for PD in the northern Han Chinese population, we investigated three single nucleotide polymorphisms (SNPs) (rs4538475, rs11107 and rs12564040) in the BST1, PARK15 and PARK9 genes. METHODS: Genomic DNA from 215 PD patients and 212 matched controls was amplified in two independent PCR systems and subsequently genotyped by digestion with the endonuclease PstI. Genetic parameter and association studies were carried out with SPSS 13.0 and PLINK 1.07 software. RESULTS: We could accurately detect all genotypes in the three loci with the PCR-RFLP or mismatched PCR-RFLP techniques. The observed heterozygosities of the rs4538475 and rs11107 loci in PD and control groups ranged from 0.460 - 0.481 and 0.410 - 0.441, in BST1, PARK15 respectively, while we detected no heterozygosity at the rs12564040 locus in PARK9. The similar distributions of genotypic frequency between both groups suggest that the three SNPs investigated in this study are unlikely to play roles as common risk factors or pathogenic mutations for PD in northern Han Chinese. CONCLUSION: The SNPs investigated in the BST1, PARK15 and PARK9 genes associated with PD susceptibility are not associated with PD in the northern Han Chinese population.

[The genetic diversity in the full coding region of human FUT5 gene in a Chinese Han population].

OBJECTIVE: To reveal the sequence variations of the full coding region of the human alpha (1,beta/1,4) fucosyltransferase 5 gene (FUT5) in a Chinese Han population. METHODS: The whole coding region of the FUT5 gene was amplified and sequenced in a total of 30 unrelated Chinese Han individuals. The PCR products containing the nucleotide variants observed in the study were subcloned into plasmid pcDNA to determine all potential haplotypes in the investigated population. Genetic polymorphisms of C560T (rs778970) and C484A loci were further analyzed by polymerase chain reaction-restriction fragment length polymorphism(PCR-RLFP) method. RESULTS: In addition to seven previously reported base substitutions, two novel polymorphisms, namely C484A (Leu162Met) and T684C, were found in the coding region of the FUT5 gene in the 30 individuals. Seven haplotypes were identified by subcloning the variants into plasmid and subsequent DNA sequencing. The allele frequencies in the rs778970 locus in 160 Chinese Han individuals was 0.3031 for 560C and 0.6969 for 560T, while no polymorphism was detected in the C484A locus. CONCLUSION: The sequence of the coding region in the human FUT5 gene demonstrated high genetic diversity, and the allelic distribution of the rs778970 locus in the Chinese populations is polymorphic.

[Effects of different irrigation and nitrogen supply levels on nitrate-N dynamics in a recently reclaimed sandy farmland in Heihe River basin].

Improper nitrogen (N) and irrigation management are major causes leading to deterioration in water environmental quality in the middle reaches of Heihe River basin. A controlled experimental study of different irrigation and N supply levels was therefore conducted in the Linze Inland River Basin Research Station, Chinese Academy of Sciences, to determine the influences of N addition and irrigation regime on the dynamics of nitrate-N (NO3(-) -N) distribution in soil profiles over the growing season of spring wheat. The experiment employed a completely randomized block split-plot design, with irrigation treatments [0.6, 0.8, 1.0 of the estimated evapotranspiration (ET), denoting I0.6, I0.8 and I1.0 respectively] and N addition treatments [0, 140, 221, 300 kg x hm(-2), denoting N0, N140, N221 and N30 respectively] as the main-plot and split-plot, respectively. Our results show that the rate of N is the key factor in influencing NO3(-) -N content and its leaching. The content of NO3(-) -N in the 0-200 cm soil profiles was found to increase with increased N rates, and in particular this increase was more pronounced when the N rates ranged between 221 kg x hm(-2) and 300 kg x hm(-2). In addition, NO3(-) -N leaching is relatively less apparent at the N rates in the range of 0-140 kg x hm(-2), but this effect became significant when the N rates exceeded 140 kg x hm(-2). Our results also show that NO3(-) -N contents were generally higher at the anthesis stage than at the harvest stage within the same soil layer. The observed differences in NO3(-) -N contents between the irrigation treatments of I0.6, I0.8 and I1.0 were insignificant across N rates. This finding suggests that N addition treatments may have greater impacts on NO3(-) -N leaching than irrigation treatments. Although the among-irrigation differences of NO3(-) -N contents within the same soil layer varied with N level, there was a tendency that NO3(-) -N content of I1.0 treatment was significantly lower than that of I0.8, and that of I06 irrigation treatment in the soil layer with significant differences in N contents. This result suggests declined NO3(-) -N leaching with decreased irrigation levels.

[Dynamics of soil water under Eucommia ulmodes plantation in hilly red soil region of southern China].

By using time domain reflectometry (TDR), a fixed-position monitoring research on the dynamics of soil water under Eucommia ulmoides plantation was conducted in a hilly red soil region of southern China. The results showed that there was a significant difference in the soil water storage among different months, and the dynamics of soil water could be divided into the phases of reduction, increase, and more reduction. Soil water varied significantly in its vertical distribution, and the variation pattern also differed with seasons. The vertical distribution of soil water could be divided into two phases, i.e., accumulation and depletion based on the seasonal variation of soil water, or rainy season and dry season based on the monthly variation of rainfall. Soil water was correlated significantly (P < 0.05) with relative humidity (RH), air temperature (t), vapor pressure deficit (VPD) and rainfall (R), and regulated by these meteorological factors synthetically, among which, rainfall was the most important factor, followed by air temperature. The soil water loss rate after rain had a significant hyperbolic relationship with durative droughty days, while soil water storage had a significant linear negative relationship with this duration (P < 0.05). With the extension of drought duration after rain, soil water loss tended to vary gently with increasing soil depth.

The relative importance of pre- and post-germination determinants for recruitment of an annual plant community on moving sandy land.

BACKGROUND AND AIMS: The relative importance of pre- and post-germination determinants for recruitment of natural plant communities is rarely explored. An annual plant community on moving sandy land was chosen for a case study. Answers to the following questions were sought: (a) Does recruitment of new individuals within the community of annual plants differ in time and space? (b) Is there spatial concordance between seed deposition, seedling emergence, survival and recruitment? (c) What are the direct and indirect effects of pre- and post-germination determinants on plant recruitment. METHODS: An integrative approach combining investigation of natural recruitment processes with regression, correlation and path analyses was adopted. Data on seed deposition and seedling recruitment were collected by monitoring the number of seeds deposited in the top 5 cm of the soil and the numbers of seedlings emerged and recruited from all annual plants at sites to a range of distances from the existing shrub Artemisia halodendron (Asteraceae) in eight compass directions for two consecutive growing seasons. KEY RESULTS: Community-level recruitment was strongly affected by inter-annual rainfall variation and was highly site- and density-dependent. Low recruitment rate in this system was due to low emergence rate and low post-emergence survival rate. Of the pre- and post-germination determinants studied, it was the number of seedlings which emerged and the post-emergence survival rate that had the greatest direct effects on recruitment, with a combination of both variables explaining the majority of the variance (97 %) in recruitment. CONCLUSIONS: This study suggests that post-germination determinants (emergence and survival) rather than pre-germination determinants (seed deposition) substantially determined the final pattern of recruitment. Although the density of seeds deposited did not have a significant direct effect on recruitment, it contributed to observed variation in recruitment indirectly through density-dependent emergence of seedlings.

Wind-dispersed seed deposition patterns and seedling recruitment of Artemisia halodendron in a moving sandy land.

BACKGROUND AND AIMS: Artemisia halodendron is a native sub-shrub that occurs mainly in moving and semi-fixed sandy lands in Inner Mongolia, China. Information on the spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron inhabiting moving sandy lands is very limited. The aim of this study was to examine wind-dispersed seed deposition patterns and post-dispersal recruitment of A. halodendron seedlings. * METHODS: The spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron were examined by investigating the numbers of deposited seeds, emerged and surviving seedlings using sampling points at a range of distances from the parent plant in eight compass directions for two consecutive growing seasons. * KEY RESULTS: Wind-dispersed seed deposition showed considerable variation between directions and years. Wind transported A. halodendron seeds only a few meters away from the parent plant in all eight directions. Seedling emergence and establishment also showed between-direction and between-year variability, but the spatial pattern of seedling distribution differed from that of seed deposition. Only a very small fraction (<1 %) of the deposited seeds emerged in the field and survived for long enough to be included in our seedling censuses at the end of the growing season. * CONCLUSIONS: The spatial variation in wind speed and frequency strongly affects the pattern of seed deposition, although the variation in seed deposition does not determine the spatial pattern of seedling recruitment. Seeds of A. halodendron are not dispersed very well by wind. The low probability of recruitment success for A. halodendron seedlings suggests that this species does not rely on seedling recruitment for its persistence and maintenance of population.

[Field investigation on ecological effect of windbreak and soil erosion reduction from sandy grasslands].

Through field observation of the variation of vegetational characteristics and sand transported rate in sandy grasslands at different levels of desertification during the spring erosive period, the ecological effects of windbreak and soil erosion reduction from sandy grasslands of the Horqin Sandy Land were studied. The results showed that vegetational coverage varied obviously from 0.3% in the shifting sand land of the severe desertification to 16% in the fixed sand land of the least desertification in mid May. Increases in vegetational coverage led to a corresponding increase in surface roughness length from 0.013 cm in the shifting sand land to 0.111 cm in the fixed sand land, thus resulting in an increase in friction velocity from 0.272 m.s-1 in the shifting sand land to 0.823 m.s-1 in the fixed sand land and a decrease in mean wind speed near the surfaces from 7.0 m.s-1 in the shifting sand land to 3.8 m.s-1 in the fixed sand land. This in turn led to a reduction in the total sand transported rate within the height of 0-20 cm from 88.8 g.(h.cm2)-1 in the shifting sand land to 1.6 g.(h.cm2)-1 in the fixed sand land. When the experimental data were analyzed by regressing the total sand transported rate (Q) against vegetational coverage (VC), a model of predictive regression was developed: Q = 3.93 + 93.66e-0.60VC(R2 = 0.893, p < 0.0001, n = 40).