Effects of muscle glycogen and plasma FFA availability on human metabolic responses in cold water.

The purpose of this study was to investigate whether simultaneous alterations in the availability of plasma free fatty acids and muscle glycogen would impair the maintenance of thermal balance during cold water immersion in humans. Eight seminude subjects were immersed on two occasions in 18 degrees C water for 90 min or until rectal temperature (Tre) decreased to 35.5 degrees C. Each immersion followed 2.5 days of a specific dietary and exercise regimen designed to elicit low (LOW) or high glycogen levels (HIGH) in large skeletal muscle groups. Nicotinic acid (1.6 mg/kg) was administered for 2 h before and during immersion to inhibit white adipose tissue lipolysis. Biopsies from the vastus lateralis showed that the glycogen concentration before the immersion was significantly lower in LOW than in HIGH (223 +/- 19 vs. 473 +/- 24 mmol glucose units/kg dry muscle). However, the mean rates of glycogen utilization were not significantly different between trials (LOW 0.62 +/- 0.14 vs. HIGH 0.88 +/- 0.15 mmol glucose units.kg-1.min-1). Nicotinic acid dramatically reduced plasma free fatty acid levels in both trials, averaging 127 +/- 21 mumol/l immediately before the immersion. Cold water immersion did not significantly alter those levels. Plasma glucose levels were significantly reduced after cold water immersion to a similar extent in both trials (18 +/- 4%). Mean respiratory exchange ratio at rest and during immersion was greater in HIGH than LOW, whereas there were no intertrial differences in O2 uptake. The calculated average metabolic heat production during immersion tended to be lower (P = 0.054) in LOW than in HIGH (15.3 +/- 1.9 vs. 17.5 +/- 1.9 kJ/min).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of pre-slaughter handling,exercise and the presence of a dog on lamb welfare and meat quality

Before slaughter, lambs may experience several stressors such as feed and water deprivation, handling and transport that have the potential to negatively impact welfare and meat quality. The objective of this study was to evaluate the effect of pre-slaughter handling, exercise and the presence of a dog on the behaviour and physiology of lambs and meat quality at slaughter. At 6 months of age, 60 lambs (n=20 lambs/replicate; three replicates) were allocated to one of the two treatment groups (n=30 lambs/treatment): low (LOW) intensive handling or high (HIGH) intensive handling. LOW lambs were moved short distances, quietly and without the use of a dog before transport. HIGH lambs were moved quickly, long distances and with a dog present before transport. Lamb behaviour (standing, lying, rumination and panting) was recorded for 1 h before (post-treatment) and after transport (post-transport), and for 30 min before slaughter (pre-slaughter). Blood samples were collected before (baseline), after transport (post-transport) and at exsanguination (at slaughter) to assess cortisol, lactate and non-esterified fatty acid (NEFA) concentrations. At slaughter, lamb carcases (M. longissimus lumborum) were evaluated for pH levels, drip and cook loss, and tenderness. HIGH lambs spent more time standing (P<0.001) and panting (P<0.001) and less time lying (P<0.001) and ruminating (P<0.001) post-treatment than LOW lambs, but more (P<0.001) time ruminating post-transport. All lambs spent more time standing (P<0.001) and less time lying (P<0.001) and panting (P<0.001) post-transport and pre-slaughter than post-treatment. Cortisol concentrations were greater (P<0.001) in lambs post-transport and at slaughter compared with baseline values. Lactate concentrations were lower (P=0.002) in HIGH than LOW lambs. In addition, NEFA concentrations were higher (P<0.001) post-transport and at slaughter in HIGH compared with LOW lambs. Ultimate pH was higher (P<0.001) in HIGH than LOW lambs and pH declined quicker (P=0.012) in LOW than HIGH lambs. Cook loss, drip loss and shear force were lower (P⩽0.05) in HIGH than LOW lambs. The HIGH intensive pre-slaughter handling regime used in the present study caused stress in lambs and increased ultimate pH that could potentially negatively impact welfare, product quality and consistency.     

Patterns of movement by baboons in the Drakensberg mountains: Primary responses to the environment

The movement patterns of two chacma baboon troops in the Drakensberg mountains of South Africa were studied over an 18-month period. One of these troops (HIGH) lived on the escarpment slopes (1920–2980 m), while the other (LOW) lived primarily in the montane belt (1560–2000 m). In this paper we analyze the effects of environmental variables on day journeys and home range use. We found the troops to be similar in the temporal patterning of their daily movement, in the resistance of travel speed to variations in local climatic conditions, and in their response to the nutritional bottleneck at the end of the austral winter. While both troops traveled farther as food became scarcer, HIGH troop undertook longer day journeys than LOW troop. This was probably due to the interactive effects of absolutely lower food availability and lower ambient temperatures. HIGH troop traveled farther when food was scarcer and when minimum temperatures were higher. Neither variable accounted for variance in the day journeys of LOW troop. Both troops used some areas of their home ranges preferentially. For LOW troop this preference followed the spatial distribution of food. While the same was generally true for HIGH troop, its home range use was complicated by the adverse temperatures of winter and spring. It abandoned the higher, more productive part of its range once temperatures became severe, returning only after minimum ground temperatures had risen above 0°C. These usage patterns differ from those described for eastern African baboon populations and reflect both the severity and sesonality of climate and the poor quality and extreme dispersion of food that characterize these southern mountains.     

Detrimental effect of eicosapentaenoic acid supplementation on bone following ovariectomy in rats

Although several studies have reported a positive effect of n-3 essential fatty acids (EFAs) on bone density post-ovariectomy, the role of specific EFAs has yet to be fully elucidated. In this study, ovariectomised (OVX) rats were supplemented with 0.1 g (LOW) or 1.0 g (HIGH) of eicosapentaenoic acid (EPA)/kg body weight for 9 weeks. Bone mineral density (BMD), 25-hydroxyvitamin D(3) and plasma fatty acid profile were compared to those of OVX and sham animals fed a non-supplemented diet. BMD decreased significantly in all OVX (P<0.001) but not sham rats. There was no difference in BMD between the LOW group and OVX controls. BMD was significantly lower in the HIGH group compared to OVX and sham controls. 25-hydroxyvitamin D(3) levels were significantly higher in both the LOW and HIGH groups compared to OVX controls (P=0.0006 and 0.02, respectively). In conclusion, high-dose EPA supplementation exacerbated the effects of ovariectomy on BMD.     

The contribution of rewetting to vegetation restoration of degraded peat meadows

Question: What is the contribution of a rise in groundwater level to vegetation restoration of degraded peat meadows compared to abandonment only? Location: Abandoned peat meadows in the central part of The Netherlands. Methods: Comparison of species composition and species abundance of vegetation and seed banks of reference and rewetted peat meadows, using plant trait and seed bank analysis. Results: Vegetation of rewetted meadows shared on average only 27% of their species with the reference meadow, while this was 50% on average for species in the seed bank. Rewetted meadows had a lower total number of species and a lower number of wet grassland and fen species present in the vegetation, but had higher species richness per m², although evenness was not affected. Rewetting increased the dominance of species of fertile and near neutral habitats, but did not result in an increase of species of wet or waterlogged habitats. Re-wetted meadows were dominated by species relying mainly on vegetative reproduction and species with a low average seed longevity compared to the reference meadow. Conclusion: Rewetting was not effective as a restoration measure to increase plant species diversity or the number of wet grassland and fen species in the vegetation. If no additional restoration management is applied, the seed bank will be depleted of seeds of species of wet grassland or fen habitats, further reducing the chances of successful vegetation restoration.     

Light as an environmental filter in fen vegetation

Questions: 1. To what extent does light availability differ among fen plant communities? 2. To what extent does light coincide with productivity and moisture gradients? 3. Does light act as an important environmental filter in natural and transformed riparian landscapes? Location: Current data from the Biebrza Valley, NE Poland; literature data from the T?eboň area, Czech Republic and four sites in the western and southern Netherlands. Methods: Relative light intensity (RLI) was measured in vertical profiles, next to vegetation relevés accompanied by measurements of above‐ground biomass, summer groundwater level, N and P content in vegetation, pH and soil redox potential. Data derived from literature included profiles of RLI, biomass and vegetation records. Relationships between RLI and biomass and between species distribution, RLI and other variables were examined by regression analysis and CCA. Four traits were analysed: ability to spread clonally, seed weight, maximum height of adults and time of commencement of flowering. Results: RLI at ground level varied from < 1% in reed beds and tall herb meadows to > 60% in sedge‐moss communities and litter meadows. RLI was largely determined by the standing crop and explained a large part of variation in species occurrence. The combinations of analysed functional traits were constrained by the communities’ light profiles. Conclusion: Light availability is related more closely to site fertility than to hydrological regime. This confirms that hydrological regime and productivity should be analysed separately with regard to their effect on species distribution in wetlands. Limited light availability seems the major environmental control of the distribution of low growing and late flowering species.     

Reversal of an epigenetic switch governing cell chaining in Bacillus subtilis by protein instability

Bacillus subtilis forms long chains of cells during growth and biofilm formation. Cell separation is mediated by autolysins, whose genes are under the negative control of a heteromeric complex composed of the proteins SinR and SlrR. Formation of the SinR-SlrR complex is governed by a self-reinforcing, double-negative feedback loop in which SinR represses the gene for SlrR and SlrR, by forming the SinR-SlrR complex, titrates SinR and prevents it from repressing slrR. The loop is a bistable switch and exists in a SlrR(LOW) state in which autolysin genes are on, and a SlrR(HIGH) state in which autolysin genes are repressed by SinR-SlrR. Cells in the SlrR(LOW) state are driven into the SlrR(HIGH) state by SinI, an antirepressor that binds to and inhibits SinR. However, the mechanism by which cells in the SlrR(HIGH) state revert back to the SlrR(LOW) state is unknown. We report that SlrR is proteolytically unstable and present evidence that self-cleavage via a LexA-like autopeptidase and ClpC contribute to its degradation. Cells producing a self-cleavage-resistant mutant of SlrR exhibited more persistent chaining during growth and yielded biofilms with enhanced structural complexity. We propose that degradation of SlrR allows cells to switch from the SlrR(HIGH) to the SlrR(LOW) state.     

Effects of a passive exoskeleton on the mechanical loading of the low back in static holding tasks

With mechanical loading as the main risk factor for LBP in mind, exoskeletons are designed to reduce the load on the back by taking over a part of the required moment. The present study assessed the effect of a passive exoskeleton on back and abdominal muscle activation, hip and lumbar flexion and on the contribution of both the human and the exoskeleton to the L5/S1 net moment, during static bending at five different hand heights. Two configurations of the exoskeleton (LOW & HIGH) differing in angle-torque characteristics were tested. L5/S1 moments generated by the subjects were significantly reduced (15–20% for the most effective type) at all hand heights. LOW generated 4–11 Nm more support than HIGH at 50%, 25% and 0% upright stance hand height and HIGH generated 4–5 Nm more support than LOW at 100% and 75%. Significant reductions (11–57%) in back muscle activity were found compared to WITHOUT for both exoskeletons for some conditions. However, EMG reductions compared to WITHOUT were highly variable across subjects and not always significant. The device allowed for substantial lumbar bending (up to 70°) so that a number of participants showed the flexion-relaxation phenomenon, which prevented further reduction of back EMG by the device and even an increase from 2% to 6% MVC in abdominal activity at 25% hand height. These results indicate that flexion relaxation and its interindividual variation should be considered in future exoskeleton developments.     

Boreal Riparian Vegetation Under Climate Change

Riparian zones in boreal areas such as humid landscapes on minerogenic soils are characterized by diverse, productive, and dynamic vegetation which will rapidly react to climate change. Climate-change models predict that in most parts of the boreal region these zones will be affected by various combinations of increased temperature, less seasonal variation in runoff, increased average discharge, changes in groundwater supply, and a more dynamic ice regime. Increasing temperatures will favor invasion of exotic species whereas species losses are likely to be minor. The hydrologic changes will cause a narrowing of the riparian zone and, therefore, locally reduce species richness whereas effects on primary production are more difficult to predict. More shifts between freezing and thawing during winter will lead to increased dynamics of ice formation and ice disturbance, potentially fostering a more dynamic and species-rich riparian vegetation. Restoration measures that increase water retention and shade, and that reduce habitats for exotic plant species adjacent to rivers can be applied especially in streams and rivers that have been channelized or deprived of their riparian forest to reduce the effects of climate change on riparian ecosystems.     

Exploring nitrogen remobilization for seed filling using natural variation in Arabidopsis thaliana

Nineteen Arabidopsis accessions grown at low (LOW N) and high (HIGH N) nitrate supplies were labelled using (15)N to trace nitrogen remobilization to the seeds. Effects of genotype and nutrition were examined. Nitrate availability affected biomass and yield, and highly modified the nitrogen concentration in the dry remains. Surprisingly, variations of one-seed dry weight (DW(1S)) and harvest index (HI) were poorly affected by nutrition. Nitrogen harvest index (NHI) was highly correlated with HI and showed that nitrogen use efficiency (NUE) was increased at LOW N. Nitrogen remobilization efficiency (NRE), as (15)N partitioning in seeds ((15)NHI), was also higher at LOW N. The relative specific abundance (RSA) in seeds and whole plants indicated that the (14)NO(3) absorbed post-labelling was mainly allocated to the seeds (SEEDS) at LOW N, but to the dry remains (DR) at HIGH N. Nitrogen concentration (N%) in the DR was then 4-fold higher at HIGH N compared with LOW N, whilst N% in seeds was poorly modified. Although NHI and (15)NHI were highly correlated to HI, significant variations in NUE and NRE were identified using normalization to HI. New insights provided in this report are helpful for the comprehension of NUE and NRE concepts in Arabidopsis as well as in crops and especially in Brassica napus.     

The maximal and submaximal vertical jump: implications for strength and conditioning

The vertical jump is a widely used activity to develop explosive strength, particularly in plyometric and maximal power training programs. It is a multijoint action that requires substantial muscular effort from primarily the ankle, knee, and hip joints. It is not known if submaximal performances of a vertical jump have a proportional or differential training effect on the major lower-limb muscles compared to maximal jump performance. Therefore, the purpose of this study was to investigate the contribution that each of the major lower-limb joints makes to vertical jump performance as jump height increases and to comment on the previously mentioned uncertainty. Adult males (N = 20) were asked to perform a series of submaximal (LOW and HIGH) and maximal (MAX) vertical jumps while using an arm swing. Force, motion, and electromyographical data were recorded during each performance and used to compute a range of kinematic and kinetic data, including ankle, knee, and hip joint torques, powers, and work done. It was found that the contribution to jump height made by the ankle and knee joints remains largely unchanged as jump height increases (work done at the ankle: LOW =1.80, HIGH = 1.97, MAX = 2.06 J.kg(-1), F = 3.596, p = 0.034; knee: LOW = 1.62, HIGH = 1.77, MAX = 1.94 J.kg(-1), F = 1.492, p = 0.234) and that superior performance in the vertical jump is achieved by a greater effort of the hip extensor muscles (work done at the hip: LOW = 1.03, HIGH = 1.84, MAX = 3.24 J.kg(-1), F = 110.143, p < 0.001). It was concluded that the role of submaximal and maximal jumps can be differentiated in terms of their effect on ankle, knee, and hip joint muscles and may be of some importance to training regimens in which these muscles need to be differentially trained.     

Effects of Changes in Water Intake on Mood of High and Low Drinkers

Objective

To evaluate the effects of a change in water intake on mood and sensation in 22 habitual high-volume (HIGH; 2-4 L/d) and 30 low-volume (LOW; <1.2 L/d) drinkers who were asked to respectively decrease and increase their daily water intake.

Method

During baseline HIGH consumed 2.5 L and LOW 1 L of water/day. During 3 controlled intervention days HIGH''s water intake was restricted to 1 L/day whereas LOW''s was increased to 2.5 L water/day. Several mood scales (Bond & Lader Visual Analog Scale (VAS), Profile of Mood States, Karolinska Sleepiness Scale, Thirst & Emotional VAS) were administered at different time points during the study. ANOVA including intervention, time point and intervention by time point as fixed effects on mean values (i.e.; baseline data vs. mean of 3 intervention days) for each mood scale was performed.

Results

At baseline HIGH and LOW were comparable in mood state, except for thirst scores (estimate = 17.16, p<0.001) and POMS depression-dejection scores (estimate = 0.55, p<0.05) which were both higher in the HIGH vs. LOW. In HIGH the restricted water intake resulted in a significant increase in thirst (p<0.001) and a decrease in contentedness (p<0.05), calmness (p<0.01), positive emotions (p<0.05) and vigor/activity (p<0.001). In LOW, increased water consumption resulted in a significant decrease in fatigue/inertia (p<0.001), confusion/bewilderment (p = 0.05) and thirst (p<0.001) and a trend to lower sleepiness (p = 0.07) compared to baseline.

Conclusion

Increasing water intake has beneficial effects in LOW, especially sleep/wake feelings, whereas decreasing water intake has detrimental effects on HIGH''s mood. These deleterious effects in HIGH were observed in some sleep/wake moods as well as calmness, satisfaction and positive emotions.     

High-density electromyographic assessment of stretch reflex activity during drop jumps from varying drop heights

This study investigated how drop heights and their associated drop jump performance relate to stretch reflex modulations. Eleven male subjects performed ten drop jumps from each of three individually predetermined drop heights. These were the drop height resulting in maximal performance (OPT), as well as 10 cm below (LOW) and above (HIGH) maximal performance. To quantify drop jump performance the reactive strength index, derived from force plate measures, was used. High-density surface EMG provided both stretch reflex response timing and size, as well as novel insight into the associated motor unit recruitment via muscle fiber conduction velocity estimations. These measures were examined in the vastus lateralis (VL), soleus (SOL) and gastrocnemius medialis (GM).Drop jump performance improved by 9% (p < 0.001) from LOW to OPT and decreased by 5% (p = 0.008) from OPT to HIGH. Despite decreasing performance, stretch reflex responses were largest at HIGH. Stretch reflex responses timing did not change; staying within the short (SOL, <60 ms) and medium (VL, GM; 60–85 ms) latency response time-frames. Motor unit recruitment appeared to change across drop heights only for VL, whereas activation intensity only changed for SOL. These results indicate that during drop jumps above OPT neuromuscular modifications result in VL no longer being maximally recruited.     

The impact of flooding regime on the soil seed bank of flood‐meadows

Abstract. We assessed the significance of flooding for the floristic composition of seed banks in flood‐meadows of the northern valley of the Upper Rhine. We compared three hydrological compartments of the alluvial plain, consisting of the regularly flooded land between the river and low summer dykes (functional flood‐plain), the occasionally flooded land between summer dykes and high winter dykes (hybrid floodplain) and the land behind the winter dykes, which is now only submerged by ascending groundwater (fossil flood‐plain). Due to their different flooding regime, the three compartments should differ with respect to the prevailing conditions of diaspore input. The seed density of soil samples increased with the duration of flooding in the three compartments, while species richness and the proportion of species not occurring in the vegetation was constant. The increase in seed density can be largely attributed to an increase of disturbance indicators, which are present in the above‐ground vegetation and capable of forming a long‐term persistent seed bank. No effects of flooding on the composition of seed banks in the three flood‐plain compartments were found. The differences in seed bank composition can be largely explained by corresponding differences in above‐ground vegetation and former and present‐day meadow management. Seeds of species absent from above‐ground vegetation can be attributed to the local species pool present in the immediate vicinity of the study plots. We discuss consequences of the results for the restoration of species‐rich flood‐plain meadows.     

Changes in the bacterial populations of the highly alkaline saline soil of the former lake Texcoco (Mexico) following flooding

Flooding an extreme alkaline-saline soil decreased alkalinity and salinity, which will change the bacterial populations. Bacterial 16S rDNA libraries were generated of three soils with different electrolytic conductivity (EC), i.e. soil with EC 1.7 dS m⁻¹ and pH 7.80 (LOW soil), with EC 56 dS m⁻¹ and pH 10.11 (MEDIUM soil) and with EC 159 dS m⁻¹ and pH 10.02 (HIGH soil), using universal bacterial oligonucleotide primers, and 463 clone 16S rDNA sequences were analyzed phylogenetically. Library proportions and clone identification of the phyla Proteobacteria, Actinobacteria, Acidobacteria, Cyanobacteria, Bacteroidetes, Firmicutes and Cloroflexi showed that the bacterial communities were different. Species and genera of the Rhizobiales, Rhodobacterales and Xanthomonadales orders of the α- and γ-subdivision of Proteobacteria were found at the three sites. Species and genera of the Rhodospirillales, Sphingobacteriales, Clostridiales, Oscillatoriales and Caldilineales were found only in the HIGH soil, Sphingomonadales, Burkholderiales and Pseudomonadales in the MEDIUM soil, Myxococcales in the LOW soil, and Actinomycetales in the MEDIUM and LOW soils. It was found that the largest diversity at the order and species level was found in the MEDIUM soil as bacteria of both the HIGH and LOW soils were found in it.     

Vegetation change following exclusion of grazing animals in depleted grassland,Central Otago,New Zealand

Abstract. Models of semiarid vegetation dynamics were evaluated to explain changes in the grassland of interior South Island, New Zealand. Annual records were taken for six years of plant species height frequency and percentage ground cover in five plots established in 1986. One subplot at each site was fenced to exclude sheep, one to exclude rabbits and sheep, and one remained unfenced as a control. Records from 1986–1992 were analysed by ordination. The overall pattern of vegetation change shows considerable year-to-year variation. At some sites, variation in vegetation composition between years was as great as, or greater than, that between grazed and ungrazed subplots. Such variation is particularly evident in grazed vegetation, perhaps because it is under greater stress than ungrazed vegetation. At one site changes in vegetation total cover and species composition could be statistically related to rainfall during the first half of the growing season. The only general trends following cessation of grazing were for perennials to increase in frequency, and for year-to-year changes to become smaller with time. Total vegetation cover values seldom changed as a result of cessation of grazing, but tended to follow year-to-year changes in species frequency. The results do not in general support switch/state-and-transition models of semi-arid vegetation dynamics. Vegetation change follows changes in grazing and climate with little lag. This most closely conforms with the Pulse-phase dynamic model.     

Long-term vegetation changes in stands of Pinus sylvestris in southern Finland

Abstract. Understorey vegetation dynamics in Pinus sylvestris L. stands were examined over 30 yr in southern Finland. Data were collected from 112 permanent sample plots twice, first in 1950–1956 and again in 1983 - 1986. Between the two surveys 52 stands were clear-felled and in the 60 remaining old stands thinnings of various magnitude were conducted. In the mature, thinned stands species presence remained virtually unchanged. With the exception of a few species, including Vaccinium vitis-idaea, Hylocomium splendens, and Dicranum polysetum, the changes in species cover were also slight. In the clear-felled plots the changes in species presence were minor but the cover of many species changed strongly. The average cover of Vaccinium myrtillus and Hylocomium splendens dropped to near zero and that of Vaccinium vitisidaea and Pleurozium schreberi decreased 2 - 4 times on all sites. The cover of Calluna vulgaris approximately doubled, and Cladina rangiferina and Cladina arbuscula also increased after canopy removal. In addition to intrinsic successional change, a special interest in this study was to investigate vegetation dynamics in relation to forest land classification methods in which understorey vegetation is used as part of the classification criteria. The results support the Cajanderian site classification approach, in the case of boreal Scots pine stands, that sites can be classified on the basis of understorey vegetation at different successional phases. However, because of the strong successional and site-to-site variation in species cover, it is suggested that site classification be based primarily on species presence     

黄河三角洲滨海湿地地下水位变化对土壤种子库特征的影响

地下水位是影响湿地生态系统结构和功能的重要环境因子之一,然而其如何影响滨海湿地土壤种子库特征尚不清楚。通过地下水位控制试验,研究黄河三角洲滨海非潮汐湿地地下水位梯度（-20、-60、-100 cm）下,土壤种子库密度、物种多样性等特征,并通过土壤化学指标与对应的土壤种子库特征之间的通径分析,探讨地下水位深度变化对土壤种子库特征的影响机理。研究发现,在该区域秋季采样的土壤种子库中,碱蓬和盐地碱蓬的种子数量最多;地下水位变化对土壤种子库密度无显著影响,但对土壤种子库的物种组成影响较大,随着地下水位深度增加,多年生草本植物种类呈增加趋势。整体上,随着地下水位深度增加,土壤种子库的Margalef丰富度指数和Shannon-Wiener多样性指数随之增大。主成分分析表明,土壤盐是影响黄河三角洲滨海湿地土壤种子库组成特征的主导因素,贡献率为69.482%,土壤养分为次要影响因素,贡献率为23.710%,进一步通径分析表明,土壤水溶性盐总量对种子库物种多样性起到限制作用,同时,有效磷浓度通过水溶性盐总量对Margalef指数和Shannon-Wiener指数表现为间接负作用,总磷浓度对种子库与地上植被相似性起到促进作用。研究表明,黄河三角洲滨海湿地地下水位深度变化,主要通过影响土壤水溶性盐总量,进而影响土壤种子库物种多样性。     

Ecohydrological characterization of a groundwater-fed alluvial floodplain mire

Abstract. In a small alluvial floodplain depression (21 ha) of the river Dijle, a selection of 56 characteristic, mainly groundwater-depending plant species was mapped using a regular 20 by 20 m square cell mapping grid. In order to understand the spatial distribution of the plant species and their vegetation types, several environmental variables, including groundwater regime, groundwater chemistry, soil texture, soil chemical composition and management type were measured in detail. Using Detrended Correspondence Analysis and Canonical Detrended Correspondence Analysis, the relation between these environmental variables and the plant species and vegetation types, respectively, is described in detail. Management type and groundwater fluctuations are recognized as the two main sets of environmental variables causing the specific spatial distribution of plant species and vegetation types for the mire-ecosystem of the silty alluvial floodplain.     

The influence of maternal nutrition on expression of genes responsible for adipogenesis and myogenesis in the bovine fetus

The objective of this study was to determine whether altered maternal energy supply during mid-gestation results in differences in muscle histology or genes regulating fetal adipose and muscle development. In total, 22 Angus cross-bred heifers (BW=527.73±8.3 kg) were assigned randomly to the three dietary treatments providing 146% (HIGH; n=7), 87% (INT; n=7) or 72% (LOW; n=8) of the energy requirements for heifers from day 85 to day 180 of gestation. Fetuses were removed via cesarean section at day 180 of gestation and longissimus muscle (LM) and subcutaneous fat were collected and prepared for analysis of gene expression. Samples from the LM and semitendinosus (ST) were evaluated for muscle fiber diameter, area and number. The right hind limb was dissected and analyzed to determine compositional analysis. Fetal growth and muscle histology characteristics of the LM and ST were similar among treatments. Preadipocyte factor-1 expression was up-regulated in fetal LM (P<0.05) of HIGH fetuses as compared with INT, whereas LOW fetuses showed increased CCAAT/enhancer-binding protein-β (C/EBP-β) expression in LM as compared with INT (P<0.05). Peroxisome proliferator-activated receptor γand C/EBP-α did not differ as a result of dietary treatment in LM or subcutaneous fat samples. There was a tendency for increased expression of fatty acid synthase in LM of LOW fetuses as compared with INT (P<0.10). Myogenin was more highly expressed (P<0.05) in LM of the LOW fetuses, whereas μ-calpain expression was increased in the HIGH treatment compared with INT. A tendency for increased expression of IGF-II was observed for both LOW and HIGH fetuses compared with INT (P<0.10). Expression of stearoyl-CoA desaturase, myoblast determination protein 1, myogenic factor 5, myogenic regulatory factor-4, m-calpain, calpastatin, IGF-I and myostatin was similar between treatments. Collectively, these results suggest that fetal growth characteristics are not affected by the level of maternal nutritional manipulation imposed in this study during mid-gestation. However, differences in expression of fetal genes regulating adipose and muscle tissue growth and development could lead to differences in postnatal composition and warrants further investigation.