Effects of changes in the timing and duration of the wet season on the germination of the soil seed bank of a seeder-dominated Mediterranean shrubland

In seasonal climates, rainfall patterns are highly variable across years, and can control seed bank dependent regeneration. Here we asked how changing the timing and duration of the wet season would affect the germination of the soil seed bank of a 14-year-old seeder-dominated shrubland. Soil samples, subjected or not to a heat shock, simulating fire, were set to germinate in a chamber whose conditions (temperature and photoperiod) were successively changed to simulate autumn, winter, and spring. Irrigation was implemented to produce three wet season treatments, varying its timing and duration: long (14?weeks of irrigation, during autumn, winter, and spring), medium (8?weeks, late autumn to early spring) and short (4?weeks in winter). Wet season treatments significantly affected germination of shrubs and herbs, as well as species richness and diversity, whereby the later and shorter the season, the lower these variables. Dicots were more sensitive to the treatments than monocots. The timing of the wet season was also important, as similar significant differences were found when only the first 4 weeks of each simulated wet season treatment were considered; the later the season, the lower the germination and richness. Heating the soil generally increased germination but few significant effects were found. We document that a change in the timing and/or duration of the wet season can significantly affect soil seed bank germination. We discuss these results in a context of shifting rainfall patterns under climate change.     

Biomass Yield and Quality of Reed Canarygrass under Five Harvest Management Systems for Bioenergy Production

Reed canarygrass, Phalaris arundinacea L., produces high biomass yields in cool climates and wetlands. The number and timing of harvests during a growing season directly affect biomass yield and biofuel quality. In order to determine optimum harvest management, seven cultivars of reed canarygrass were planted in field experiments at Ames, IA; McNay, IA; and Arlington, WI in the upper Midwestern USA and harvested once in autumn or in winter, twice in spring + autumn or spring + winter, or three times during the season as hay. Biomass yield varied considerably among harvest treatments, locations, and years, ranging up to 12.6 Mg ha^?1. Dry matter percentage ranged from 37% for spring-harvested biomass to 84% for overwintered biomass. The three harvest hay and two harvest spring + autumn managements produced the highest biomass yield compared to other systems, but the advantage, if any, of hay management was small and probably does not justify the cost of additional fieldwork. More mature biomass, such as that found in the single harvest systems, had higher fiber concentrations. Overwintered biomass had superior biofuel quality, being low in P, K, S, and Cl and high in cell wall concentration. However, winter harvest systems had lower yield than autumn harvest and in some years, no harvest was possible due to lodging from snow compaction. The main limitation of a two harvest system is the high moisture content of the late spring/early summer biomass.     

TRENDS IN AGE STRUCTURE AND PRODUCTIVITY OF PACIFIC WALRUSES HARVESTED IN THE BERING STRAIT REGION OF ALASKA, 1952–2002

Pacific walruses ( Odobenus rosmarus divergens ) are harvested by subsistence hunters in Alaska as they migrate north through the Bering Strait in the spring. Harvest records and biological specimens have been collected from the Bering Strait communities of Little Diomede, Gambell, and Savoonga since the 1950s. Harvest levels in the Bering Strait region peaked in the late 1980s and declined thereafter; however, there was considerable variation in the size and composition of the harvests among communities and over time. The relationships among characteristics of the community harvests and the presence of temporal trends were investigated using generalized linear models. The proportion of females in the catch increased over time in all three communities, while the proportion pregnant among harvested females declined over the range of sample years. The ages of harvested walruses increased over time in all three communities through the 1980s, after which trends in age stabilized or began to decline. The age of first reproduction was significantly older for females sampled in 1975–1985 than for females sampled between 1952 and 1962 or 1992 and 1998. Factors thought to have influenced the size and composition of the catch over the past 50 yr include hunter preferences, harvest management regimes, environmental conditions, and changes in the population itself.     

内蒙古大青山灌木铁线莲根围丛枝菌根真菌群落季节动态研究

采用Illumina MiSeq测序技术研究了内蒙古大青山干旱阳坡灌木铁线莲(Clematis fruticosa)根围丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)群落的季节动态,并利用冗余分析(redundancy analysis,RDA)和Mantel test分析了土壤和植被因子与AMF之间的关系,为进一步探索灌木铁线莲-AMF共生体对不同季节环境变化的响应提供理论依据。结果表明:(1)灌木铁线莲根围AMF孢子密度不存在显著的季节性差异,根系侵染率和丛枝丰度从春季至秋季呈下降趋势。(2)3个季节共检测出163个AMF OTUs(operational taxonomic units),春季、夏季、秋季分别为116OTUs、76OTUs和70OTUs。(3)夏季和秋季的AMF丰富度(实测OTUs数和Chao1指数)以及多样性(Shannon-Wiener指数和Invsimpson指数)显著低于春季,但夏、秋季间无显著异。(4)主成分分析和PERMANOVA分析表明,夏季和秋季的AMF群落组成与春季存在显著差异,而AMF群落组成在夏季与秋季间差异不显著。(5)RDA分析表明,采样季节、植被盖度、植物多样性、土壤含水量和土壤有机质对AMF ShannonWiener指数、Invsimpson指数、Chao1指数和实测OTUs数均产生显著影响;Mantel test分析发现,采样季节是影响AMF群落组成和菌根侵染率的主导因子,但对孢子密度无显著影响,而土壤有机质是影响孢子密度的主导因子。     

荒漠河岸胡杨林生态系统能量分配及蒸散发

生态输水工程使得黑河下游地区荒漠河岸林的面积得到了恢复,为进一步巩固生态恢复的成果,非常有必要深入研究胡杨林生态系统的水热交换过程及其对环境因子和人类活动的响应机理。基于涡度相关技术,对2013-2016年荒漠河岸胡杨林生态系统的水热交换过程进行了研究,得出的主要结论如下：（1）生长季生态系统的能量消耗以潜热通量为主,波文比为0.21;非生长季则以感热通量为主,波文比为3.61;春季和秋季的灌水过程,使得胡杨生长前期和后期的潜热通量值较高,直接影响着胡杨林生态系统的能量分配。（2）灌水的时间改变了潜热通量和蒸散发的季节变化过程,而灌水的量决定着春季和秋季潜热通量和蒸散量的年际差异。（3）2014-2016年,生态系统的年蒸散量和生长季蒸散量平均分别为1092 mm和932 mm。荒漠河岸胡杨林生态系统的蒸散量主要受系统水分状况（灌水量）及植物生长状况的影响。     

河套灌区秋浇对不同类型农田土壤氮素淋失的影响

研究了河套灌区秋浇对不同类型农田 NO3 - N淋失的影响。结果表明 ,秋浇前小麦和白菜地 NO3 - N含量最高 ,玉米地和小麦 -玉米套种地次之 ,葵花地最低。秋浇后土壤剖面 NO3 - N的损失量按照表层 (0～40 cm)、中层 (40～ 80 cm)、深层 (80～ 1 2 0 cm)依次递减 (玉米地除外 )。不同农田 NO3 - N淋失量按照小麦地、白菜地、玉米地、葵花地、小麦 -玉米地依次递减。这说明 ,发展套种耕作将有利于减少氮素淋失。土壤 NO3 -N的淋失还直接导致地下水质的恶化。在当前的耕作制度及秋浇定额下 ,河套灌区每年可损失约 2 .6× 1 0 7kg N。因此 ,需要科学地确定秋浇方式和秋浇量 ,减少氮素淋失 ,减少地下水污染     

Landscape controls on the timing of spring,autumn, and growing season length in mid‐Atlantic forests

The timing of spring leaf development, trajectories of summer leaf area, and the timing of autumn senescence have profound impacts to the water, carbon, and energy balance of ecosystems, and are likely influenced by global climate change. Limited field‐based and remote‐sensing observations have suggested complex spatial patterns related to geographic features that influence climate. However, much of this variability occurs at spatial scales that inhibit a detailed understanding of even the dominant drivers. Recognizing these limitations, we used nonlinear inverse modeling of medium‐resolution remote sensing data, organized by day of year, to explore the influence of climate‐related landscape factors on the timing of spring and autumn leaf‐area trajectories in mid‐Atlantic, USA forests. We also examined the extent to which declining summer greenness (greendown) degrades the precision and accuracy of observations of autumn offset of greenness. Of the dominant drivers of landscape phenology, elevation was the strongest, explaining up to 70% of the spatial variation in the onset of greenness. Urban land cover was second in importance, influencing spring onset and autumn offset to a distance of 32 km from large cities. Distance to tidal water also influenced phenological timing, but only within ~5 km of shorelines. Additionally, we observed that (i) growing season length unexpectedly increases with increasing elevation at elevations below 275 m; (ii) along gradients in urban land cover, timing of autumn offset has a stronger effect on growing season length than does timing of spring onset; and (iii) summer greendown introduces bias and uncertainty into observations of the autumn offset of greenness. These results demonstrate the power of medium grain analyses of landscape‐scale phenology for understanding environmental controls on growing season length, and predicting how these might be affected by climate change.     

Effect of stocking strategy on distribution and recapture rate of common carp Cyprinus carpio L., in a large and shallow temperate lake: implications for recreational put‐and‐take fisheries management

It is hypothesized that the stocking procedure influences survival, growth and distribution of introduced fishes; however, there is still limited information on the effect of various stocking strategies on recaptures in natural freshwaters. The present study aim was to investigate how the rate and distribution of anglers' catches of common carp (Cyprinus carpio) vary with the stocking season (spring, summer and autumn), lake area, method (shore and offshore releases), and fish size (≤500 and >500 g) in the large and shallow Lake Balaton, Hungary. In 2010, 4500 two‐summer‐old individually‐tagged common carp were stocked to test 36 release set‐ups (three seasons × three lake areas × two methods × two size groups). Anglers reported the date, location and fish size (standard length and weight) on 787 recaptures within 2 years after the release. Recapture rate was highest in summer and lowest in autumn stockings, but was not affected by the stocking area, method or fish size. Regarding space, the widest dispersals were in recaptures in autumn and in the centre of the lake, but fish movement was not influenced by the stocking method or fish size. In conclusion, in summer the stocking quotas should be evenly distributed along the entire shoreline; early spring stockings may be optimized for transport costs and concentrated by each lake basin. Late autumn stockings should be avoided, and the capacity of effective wintering ponds should be developed. This study also provides a good framework for testing fisheries management alternatives in other intensively fished habitats.     

The formation of proventriculus block, alimentary activity and mortality of flea Amphipsylla primaris primaris infected with Yersinia pestis

The results of experiments held in 1982-1983 in Tuva plague natural focus with flea Amphipsylla primaris primaris (Jordan et Rothschild, 1915) from natural populations, whish were inflected and fed on specific host--flat-headed vole (Alticola strelzovi), are analyzed. The initial infectivity of the insects in autumn was higher than in spring: 90 and 50 % respectively. Accumulation of the agent in aggregated form in the organism of A. p. primaris, estimated by the quantity of fleas with and partial blocks, was more active in imago of both sexes in autumn than in spring, while sucking flea were observed in spring more often than in autumn. Irrespective of season, the part of males with visible accumulations of Y. pestis was more, and their alimentary activity was higher than that of females. Fleas died much more quickly in spring. Part of the males with proventriculus block exceeded that of females in spring experiment. Females with alimentary canal obstruction prevailed in autumn. Thus, sex of the insect and season of the experiment conducting influenced on all studied indices. Besides that, Y pestis ability for the proventriculus block formation in fleas during different seasons can change by the opposite way depending on sex of the ectoparasites.     

Factors affecting the establishment and growth of annual legumes in semi-arid mediterranean grasslands

Legumes are an important component of mediterranean grasslands with a significant ecological and economic role. The aim of this study was to investigate the factors that affect their establishment and growth and how they survive in a highly variable and unpredictable environment. The research was carried out in a grassland characterised by a semi-arid mediterranean climate and located on a calcareous substrate at about 150 m a.s.l., in Macedonia, northern Greece. It was dominated by annual legumes such as Hippocrepis multisiliquosa, Medicago disciformis, Medicago minima, Onobrychis aequindentata, Trifolium angustifolium, Trifolium campestre and Trifolium scabrum. It was subjected to the following treatments for four consecutive years: prescribed burning, irrigation, digging, cutting, P fertilization and control. Total legume density was measured in late autumn and in the following spring each year, while total legume biomass was measured only in spring. Dominant legume species densities and biomasses were measured only in spring in the last 3 years. Also, monthly precipitation and air temperature were recorded in a nearby weather station. A great reduction of both legume density and biomass occurred at the third growing season due to adverse weather conditions. Among treatments, P fertilization affected the positively annual legume density and biomass. The other treatments such as burning, irrigation, digging and cutting influenced positively or negatively annual legume density and biomass depending on the climatic characteristics of the particular growing season involved. It is concluded that in semi-arid mediterranean grasslands with cold winters, weather conditions strongly interact with human disturbances in affecting establishment and growth of annual legumes.     

Seasonal variation in the activity of the Leydig cells in Egyptian Nubian goat (Zaraibi) bucks

Ten Egyptian Nubian goat bucks were used to evaluate the effect of season on testicular hormonal activity and ultrastructure. Parameters were recorded for 7 consecutive weeks in the middle of the four seasons, with blood samples being collected weekly. At the end of each of these seasons, testicular biopsies were obtained surgically for histological and cytological studies. Season had a significant effect on plasma testosterone concentration, being at its lowest level (P < 0.01) during winter and spring (1.2 and 2.6 ng/ml, respectively), while at its highest during summer (10 ng/ml). The effect of season on plasma LH concentration was higher (P < 0.01) in autumn (2.9 mIU/ml) and less in spring and summer (0.4 mIU/ml). Season of the year influenced the percentage of sectional tissue area occupied by the seminiferous tubules and interstitial tissue. Seminiferous tubules occupied the majority of the testicular tissue during winter (76.6%), with the least being occupied during spring (49.8%). The thickness of the seminiferous tubules was maximal during autumn, followed by summer (53 and 36 μm, respectively). In summer the Leydig cells contained abundant smooth endoplasmic reticulum (sER), while some areas of the cytoplasm were occupied exclusively by tubular sER, arranged in parallel—indicating the highest activity of these cells. A characteristic multivesicular structure with numerous large lipid droplets and vacuoles was recorded in the Leydig cells during spring and winter, denoting low or even arrested activity of the cells. It could be concluded that season influences the activity of the Leydig cells of Egyptian Nubian bucks, and this is reflected by their ultrastructure and secretive activity.     

Season of ejaculate collection influences the freezability of boar spermatozoa

The aim of this retrospective study was to evaluate whether the season of ejaculate collection influences the freezability of porcine sperm. A total of 434 ejaculates were collected from boars of six different breeds over three years (2008–2011) and throughout the four seasons of the year identified in the northern hemisphere (winter, spring, summer and autumn). The ejaculates were cryopreserved using a standard 0.5 mL straw freezing protocol. Sperm quality was assessed before (fresh semen samples kept 24 h at 17 °C) and after freezing and thawing (at 30 and 150 min post-thawing in semen samples kept in a water bath at 37 °C), according to the percentages of total motility, as assessed by the CASA system, and viability, as assessed by flow cytometry after staining with SYBR-14, PI and PE-PNA. The data, in percentages, on sperm motility and viability after freezing and thawing were obtained at each evaluation time (recovered) and were normalized to the values before freezing (normalized). The season of ejaculate collection influenced (P < 0.01) sperm quality before freezing and after thawing (recovered and normalized), irrespective of the breed of boar. Sperm quality was lower in summer, both in terms of motility and viability, and in autumn, in terms of motility, than in winter and spring. Seasonality in the normalized data indicates that the season of ejaculate collection influences sperm freezability, regardless of the season’s influence on sperm quality before freezing. Consequently, the spermatozoa from ejaculates collected during summer and, to a lesser extent, also in autumn, are more sensitive to cryopreservation than those from ejaculates collected during winter and spring.     

不同透光环境下红松光合色素含量的季节变动及应对策略

研究了辽东山区天然次生林内3种不同透光环境(强度透光、中度透光和弱度透光)下红松针叶光合色素(叶绿素a(Chl a)、叶绿素b(Chl b)、类胡萝卜素(Car)和叶绿素总量(Chl T))应对光环境季节变动做出的适应性调整。结果表明,随季节的变动(从春季至秋季),林分透光孔隙度逐渐减小。春季,透光度越大,红松叶绿素含量越高,Chl a/b值升高,Car/Chl T值降低;夏季,不同透光条件对红松光合色素含量无影响;秋季,各类透光条件下红松光合色素含量总体表现为升高的趋势,强度透光与中度透光条件红松针叶Chl a/b显著大于弱度透光,3种透光条件下红松Car/Chl T均降低。在春季红松开始生长前进行适当抚育,能提高光合色素含量,增强光合作用能力,促进生长。     

Carbon-based secondary and structural compounds in Mediterranean shrubs growing near a natural CO2 spring

We studied carbon‐based secondary and structural compounds (CBSSCs) in Myrtus communis, Erica arborea, and Juniperus communis co‐occurring in a natural CO₂ spring site and in a nearby control site in a Mediterranean environment. Leaf concentrations of phenolics and CBSSCs, such as lignin, cellulose, and hemicellulose, total nonstructural carbohydrates (TNCs), and lipids were measured monthly (phenolics) and every two months (the other compounds) throughout a year. There was a slight seasonal trend towards maximum concentrations of most of these CBSSCs during autumn–winter and minimum values during the spring season, particularly in Myrtus communis. For most of the CBSSCs and species, there were no consistent or significant patterns in response to the elevated [CO₂] (c. 700 μmol mol^?1) of the spring site. These results were not due to a dilution effect by increased structural or nonstructural carbon. Therefore, in contrast to many experimental studies of CO₂ enrichment, mainly conducted for short periods, there were no greater concentrations of phenolics, and, as in many of these studies, there were neither greater concentrations of the other CBSSCs. These results do not agree with the predictions of the carbon source‐sink hypotheses. Possible causes of this disagreement are discussed. These causes include the complex heterogeneous environmental conditions and the variability of resource availabilities in the field, photosynthetic down‐regulation, and/or the homeostatic and evolutionary nature of organisms. These results suggest evolutionary adaptive responses to changes in CO₂. They also suggest caution in attributing increased CBSSC concentrations to elevated [CO₂] at long‐term scale in natural conditions, and therefore in their implications for plant–herbivore interactions and for decomposition.     

Factors affecting harvests of fishers and American martens in northern michigan

Harvest data (e.g., number of animals harvested, trapper effort) are an important source of information for state wildlife agencies to manage harvested furbearers. These data provide evidence to support adapting harvest regulations when necessary. Setting appropriate harvest regulations for fishers (Martes pennanti) and American martens (Martes americana) is critical, as these species often exist at low densities, are sensitive to timber-management practices and trapper-harvest, and experience some level of interspecific predation and competition in sympatric populations. We estimated effects of management (e.g., number of fishers or martens harvested per trapper per season [harvest limit], season length) and extrinsic (e.g., weather, pelt prices) factors on regulated harvests of fishers and martens in the Upper Peninsula of Michigan during 1996–2007. We used generalized linear mixed models in an information-theoretic approach (quasi-likelihood adjusted Akaike Information Criterion [QAIC]) to discern which factors most strongly influenced fisher and marten harvests. For harvest of fishers, the 3 QAIC-best models included harvest limit, season length, and number of trappers, suggesting that regulatory changes within the ranges tested may be implemented to influence harvest. The QAIC-best model (harvest limit) contained 26% of the weight of evidence, and using an independent subset of data, showed no difference between model predictions and harvest data. In contrast, harvest of martens was not strongly influenced by any factors we tested. Possible reasons for a lack of measurable effects while modeling harvest of martens include a low harvest limit (i.e., 1 marten) or incidental harvest of martens by fisher or bobcat (Lynx rufus) trappers. Knowledge of influences on harvest will lead to informed decision-making when managers are setting harvest regulations, particularly for low-density furbearers. © 2011 The Wildlife Society.     

Effects of Spray Application of Lanthanum and Cerium on Yield and Quality of Chinese Cabbage (Brassica chinensis L) Based on Different Seasons

The use of single light rare earth elements in agriculture was studied using the application of single rare earth elements (La and Ce) to Chinese cabbage (Brassica chinensis L.) in field plot experiments where the soil conditions remained the same but the season (spring or autumn) in which application occurred was altered. The results showed that the Chinese cabbage’s nutrition quality between the two seasons had obvious differences. When planted in the autumn, the soluble sugar and vitamin C content was higher, the titratable acid and nitrate content was lower, and the ratio of sugar to acid was higher, while when planted in spring, the situation was opposite. La or Ce treatments in spring and autumn promoted the growth of the Chinese cabbage, the fresh and dry weight of the stems and leaves increased, the ratio of dry to fresh weight increased, and the observed effects were greater in the Ce treatments than the La treatments. Moreover, the soluble sugar content increased and the titratable acid content decreased, which meant that the ratio of sugar to acid increased. There was an increase in the vitamin C and nitrate content in the spring Chinese cabbage, while there was a decrease in the vitamin C and nitrate content in the autumn. The levels of the heavy metals Cu, Zn, Cd, Pb, and Ni decreased. The La treatment had greater effects on the spring Chinese cabbage, while the Ce affected the autumn Chinese cabbage more.     

Infectivity variation of Discaria trinervis-nodulating Frankia in Patagonian soil according to season and storage conditions

Changes in the infectious capacity of soilborne Frankia from the same site may depend on environmental conditions. To test this, we examined the effect of season of sampling, sample storage protocol and storage time. The nodulation capacity of Frankia from rhizospheric soils of Discaria trinervis (Hook et Arn.) Reiche (Rhamnaceae) growing in northwest Patagonia (Argentina) was measured using the most probable number method. Soil samples were collected seasonally and either stored moist at 4°C or air dried at room temperature for few days. Old (air-dried) soil samples were also assayed. All soils nodulated D. trinervis seedlings. Nodulation units (NU) ranged from 44 (spring, moist storage) to about 1 ml⁻¹ of soil (summer moist, and summer and autumn, air-dried storage), with intermediate values in other samples. Soils stored for 12 years, 6 months or 1 week had similar NU. Frankia NU positively correlated with soil water content ( r = 0.6, P < 0.05); therefore, it is likely that soil moisture is a relevant factor regulating soilborne Frankia nodulation ability in Patagonian soils. We suggest that Frankia can remain as spores or grow saprophytically in Patagonian soils.     

Use of habitats by free-grazing sheep

A study of habitat use by free-grazing sheep was conducted in the Timahdit Station, Morocco, during spring, summer and autumn of 1985. Sheep movements through plant communities were observed and recorded by tracking animals all day long during 6 days in three different areas each season. Grazing time per unit area (GTA) for plant communities in Area 1 varied from 4 to 70 min ha⁻¹ and was influenced by season. In Area 2, there was an interaction season × plant communities (P < 0.05). Use ranged from 1 to 116 min ha⁻¹. A similar interaction also occurred in Area 3. GTA in plant communities was as high as 35 and as low as 0 min ha⁻¹. Foraging velocity (rate of walking) varied mainly with advance in season. Walking rate averaged 17, 22 and 24 steps min⁻¹ for spring, summer and autumn, respectively. The three areas offered three different cases. Sheep used Area 1 by cueing on a unique area with high-quality resources all the year. In Area 2, a plant community that contained a novel plant determined sheep grazing behavior in the spring.     

Stress caused by the 'mark-recapture' method to Coregonus albula (L)

The aim of this study was to establish if capture and marking caused stress to C. albula , and if a 'mark-recapture' method was suitable for the estimation of a population of C. albula . The blood lactate and glucose levels and the liver and muscle glycogen content were determined during the initial handling and subsequent recovery of the fish in the autumn and spring.
The blood lactate content did not increase to the critical level. Usually the values were distinctly less than 100 mg %, but the blood glucose content increased throughout the whole experiment (24 h) until it reached 250 mg %. The glycogen content in liver and muscle decreased. The liver glycogen of female C. albula was below 0·3 % in autumn, while the values for males were 3–5 %. In spring, the corresponding values were about 0·5 % in both sexes. During handling, the critical period was when the glycogen reserves in the liver became negligible, and female C. albula in autumn had the greatest risk of dying because of their low liver glycogen content.
Spring seemed to be a better season for marking than the autumn. A steady increase in blood glucose indicated there was also stress in spring and the marking time in both seasons should be less than two hours.