首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Seasonal variation of bovine anti-J in the tropics   总被引:1,自引:0,他引:1  
Close to the Equator at an altitude of 1750 m above sea level a total of 27 cows of various breeds have been studied with regard to the fluctuation of their anti-J naturally occurring antibodies. Over 16 consecutive months the average total score of anti-J varied from a minimum of 20 in October to a maximum of 37 at the end of December. Practically all the sera had the lowest level of anti-J in October. This is about two months after the lowest yearly maximum temperature. It is concluded that gradual changes in temperature can cause variation in anti-J titer, and that the magnitude of the seasonal temperature changes influences the fluctuation of the natural anti-J.  相似文献   

2.
This study, for the first time, investigated the total protein changes and protease activity pattern of three cultivars of kiwifruit including Abbott, Allison and Hayward, cultivated in the north of Iran, during 6 months of fruit development from July to December 2008. During the last month of sampling, fruits were stored in ambient temperature. According to the result of fruit extracts, pattern of changes in total protein concentration showed three significant steps: low concentration of protein during the early stages of fruit development until middle of July for Allison and Hayward and early August for Abbott, increasing protein concentration until middle of October for Allison and Hayward and late October for Abbott, and steady state level of protein concentration until harvesting time. During storage time of fruits, all three cultivars showed increasing level of total protein concentration. Among the cultivars, Hayward and Allison showed the lowest and highest total protein concentration, respectively. Protease activity showed increasing pattern in all of the investigated cultivars significantly until harvesting time. During postharvest time, Hayward did not show any significant change in protease activity but, the other two cultivars had increasing pattern from 10 to 20th of storage and then decreased significantly. Among the cultivars, Abbott showed the lowest and Allison the highest level of total protease activity at harvesting and postharvesting time. SDS-PAGE, ion-exchange chromatography and zymogram native-PAGE of fruits extraction showed that dominant protein and protease activity in these cultivars during fruit development and ripening process is related to actinidin.  相似文献   

3.
天目山自然保护区啮齿类的研究   总被引:7,自引:1,他引:7  
啮齿类是哺乳动物中种类和数量最多的一个类群,与农、林、牧和卫生保健事业有密切关系。在自然保护区,它是生态系统的重要成分之一。因此,啮齿类的研究不仅有利于进一步发展生产,而且对保护区的建设和利用也有重要的意义。  相似文献   

4.
为了解全球升温背景下我国亚热带地区树木生长对气候变化的响应,基于树木年轮学方法,在湖南莽山建立不同海拔(1 400、1 200、1 000 m)华南五针松(Pinus kwangtungensis)标准年表,利用响应分析和单年分析研究其径向生长与气候因子的相关关系。结果表明,海拔1 400 m处华南五针松的径向生长与当年6月均温和最高温显著负相关,与当年4月的降水量呈显著正相关关系;海拔1 200 m处的径向生长与当年3月均温及上年和当年10月均温、最低温显著正相关,与当年7月的最低温显著负相关,与上年11月降水量呈显著正相关关系;海拔1 000 m处的径向生长与当年6月均温、最高温和当年1月的平均温、最低温以及上年10月的最低温显著负相关,与当年3月、上年10月和当年10月的降水呈显著正相关关系。温度和降水共同影响着该地区华南五针松的径向生长,生长季初期的温度和降水以及夏季温度是影响其生长的关键气候因子。  相似文献   

5.
The pistachio fruit hull borer, Arimania comaroffi (Ragonot) (Lepidoptera: Pyralidae), is a key pest of pistachio orchards in Iran. This pest passes the winter as diapausing pupae. In this study, some physiological changes in relation to environmental temperature were investigated in field collected pupae. The relationship between supercooling point, cold hardiness and physiological changes of a wild population of this pest was also investigated. The glycogen content decreased with decrease in environmental temperature. Decrease in glycogen content was proportional to increase in total body sugar, trehalose, myo-inositol and sorbitol contents. In January with mean ambient temperature of 5.4°C, glycogen (5 mg/g fresh body weight) content was at the lowest level whereas total body sugar (10.3 mg/g fresh body weight), trehalose (8.6 mg/g fresh body weight), myo-inositol (5.3 mg/g fresh body weight) and sorbitol (2.6 mg/g fresh body weight) were at the highest levels. Total body sugar, trehalose, myo-inositol and sorbitol contents increased as mean temperature decreased from 22.7°C in October to 5.4°C in January. Total body lipid decreased during overwintering and reached to the lowest level at the end of March. Supercooling points were decreased from October to January and reached to the lowest level (-16°C) in January with minimum ambient temperature of -10°C. Survival at low temperature after 24 h was also greatest in January with 72% survival at -10°C, 39% survival at -15°C and 0% survival at -20°C. Increase in temperature from February onward, was proportional with increase in supercooling points and decrease in survival rate. Regardless of sampling date, all pupae died after 24 h at -20°C, whereas none pupae died after 24 h at -5°C. This indicates that this insect is freeze-intolerant.  相似文献   

6.
气候变化对鄱阳湖白鹤越冬种群数量变化的影响   总被引:2,自引:0,他引:2  
分析了1983—2011年鄱阳湖国家级自然保护区越冬白鹤种群数量的年际变化趋势,检验了白鹤种群动态与繁殖地和越冬地气候变化的相关性,气候变量包括月平均气温、月平均最高气温、月平均最低气温和月降水量。研究结果表明,鄱阳湖国家级自然保护区内的白鹤年最大数量平均为(2 130±153)只,呈显著地线性增长趋势(R2=0.454,F=22.441,df=28,P=0.000),但年际波动较大。在越冬地,越冬当年10月、11月、12月的气候变量与白鹤种群数量没有显著的相关性,但越冬初期10月份和越冬后期翌年3月份的气温变量与第4年、第5年、第6年及第7年的白鹤种群数量存在显著的正相关,表明越冬地气候对白鹤种群大小的影响存在时滞效应。越冬初期和末期可能是白鹤补充能量的关键阶段,而且越冬初期的气候可能也与冬季食物的数量或质量相关,因此这两个阶段的适宜气温可能有利于个体尤其是幼鹤的存活,使更多的个体参加繁殖,由于白鹤的性成熟年龄在3—5a,因此其对白鹤种群增长的有利影响会在3a以后表现出来。白鹤种群数量变化与繁殖地繁殖期的降水量没有显著的相关性,而与7月份的气温变量存在显著的正相关。多元线性回归分析结果表明,6a前的10月份平均最低温度、2a前的10月最高温度及5a前的10月平均气温是白鹤种群数量变化的显著预测因子,共同解释了鄱阳湖国家级自然保护区白鹤种群数量变化的74.8%(F=23.807,df=27,P=0.000)。  相似文献   

7.
A phenological-type synthesis was attempted for 10 years of limnological data of a brown-water stream of Alberta, Canada. The objectives were to predict the normal occurrence of seasonal events in the stream and to formulate indices upon which to base general stream management strategies. The stream supports a diverse chironomid fauna (109 species); and four taxa, chironomids, ostracods and the ephemeropteransLeptophlebia cupida andBaetis tricaudatus, account for 61% of the total yearly fauna by numbers. There are two obvious major seasons: a 7 month ice-free season (ca 15 April–15 November) and a 5 month winter season. Based on numerical classification of physical and chemical parameters, the ice-free season is separated into spring (April and May), summer (June, July and August) and autumn (September and October) seasons; and these four seasons can serve as the basis for describing biological seasonality. There are few detectable periodic events during the long, 5-month winter season: flow and water temperature are relatively constant and at minimum values. There are no reproductive periods for species studied; no new generations appear; drift densities are at minimum values; and for most taxa, little growth takes place in winter. Some of the important phenological events of the three ice-free seasons include: (1) a total emergence, hence reproductive, period of 6 months (April–September) for aquatic insects studied, with the largest number of taxa reproducing in late June and early July; (2) a 31/2 month period (late April–early August) when water temperatures are on the rise (log phase of total degree days curve), with maximum rate increase in May, maximum rate decrease in October, and maximum water temperature values in early August; (3) a completely green (trees and marsh grasses) watershed of less than 2 months (late June–early August); (4) a leaf-drop period of 11/2 months (September–mid October), with maximum litter-fall rate in early September; (5) maximum discharge in April; (6) minimum standing crop by numbers in April and maximum numbers in September; (7) maximum daily drift and drift densities (all taxa) in August; (8) maximum impounding effect of beaver dams in September; (9) maximum aquatic macrophyte standing crop in September; and (10) maximum ‘potential’ food resources (detritus of aquatic macrophyte and terrestrial leaf origin) in mid October.  相似文献   

8.
林群  王俊  李忠义  吴强  《生态学杂志》2015,26(11):3523-3531
增殖放流是渔业资源养护的重要手段, 生态系统与放流种类能流格局的变化研究,是进行增殖容量评估的研究基础.根据2012和2013年黄河口邻近海域的资源调查数据,构建了黄河口邻近海域6、8、10月的Ecopath模型,比较分析了3个月份该海域生态系统能量流动的变化,初步评估了三疣梭子蟹的增殖容量.结果表明: 黄河口邻近海域生态系统的能量流动主要在营养级I~III之间进行,营养级IV以及以上的能量流动较小.6月第I营养级整合系统流动的比例最高,8月最低.第II营养级整合系统流动的比例8月最高,6月最低.三疣梭子蟹相对能量流动和绝对能量流动均是第III营养级最高,三疣梭子蟹的营养级3月平均为3.28.黄河口邻近海域生态系统有较高的剩余生产量,6月最高、8月最低,系统的总初级生产量/总呼吸(TPP/TR) 3个月份分别为5.49、2.47、3.01,总初级生产量/总生物量(TPP/B)分别为47.61、33.30、29.78,同时具有较低的循环指数(FCI:0.03~0.06),黄河口邻近海域生态系统处于脆弱的不稳定期.系统的能量转换效率为7.3%~11.5%;渔获物的平均营养级8月和10月有所下降,3个月份分别为3.23、2.97和2.82;总捕捞效率8月最高,6月最低.在黄河口邻近海域8月Ecopath模型基础上,初步评估三疣梭子蟹的增殖容量为1.5115 t·km-2.  相似文献   

9.
In this paper Cupressaceae pollen season onset, severity, maximum value and maximum value date, have been studied for 15 consecutive years (1982–1996). The data set was obtained using a Hirst spore-trap (Burkard Manufacturing). In order to determine the influence of the previous months’ meteorological variables on Cupressaceae season’s parameters, the sums of maximum, average and minimum temperatures, and total rainfall for the months of October, November and December were used as independent variables in predictive formulae built by multiple regression analyses. The variance explained percentage by regression analyses varied between 60 and 87%. Total rainfall in the months prior to anthesis and temperature (particularly minimum temperature) are important factors to consider in forecasting models of Cupressaceae pollen season parameters, but meteorological conditions at the time of pollen production are also important and can modify the pre-established potential of pollination.  相似文献   

10.
李佳  李言阔  缪泸君  谢光勇  袁芳凯  黄燕  许鹏 《生态学报》2014,34(19):5522-5529
分析了1985—2011年鄱阳湖国家级自然保护区白琵鹭(Platalea leucorodia)越冬种群数量的年际变化趋势,检验了白琵鹭种群年际数量变化与越冬地气候变化的相关性,气候变量包括月平均气温、月平均最高气温、月平均最低气温和月降水量。研究结果表明,1985—2011年鄱阳湖国家级自然保护区白琵鹭种群数量为(4 632±470)只,呈显著的线性增长趋势,但年际波动较大。在越冬地,白琵鹭的种群数量与白琵鹭越冬期当年冬季各月的气温和降水变量相关系数较小,且均没有显著的相关性。同时,发现越冬地的气候条件对白琵鹭种群数量的影响存在显著的时滞效应:越冬期的月值气候变量与1—9a后的白琵鹭种群数量几乎都存在显著正相关性;10月降水量与2a后的白琵鹭种群数量存在显著负相关,12月平均最高气温与8a后的白琵鹭种群数量存在显著负相关。多元线性回归分析结果表明,越冬地2a前的10月平均最高气温、4a前的11月平均最高气温、8a前的11月降水量、4a前的12月平均气温是白琵鹭种群数量变化的显著预测变量,共同解释了白琵鹭种群数量年际变化的78.9%;其中前3个变量可以共同解释白琵鹭种群数量变化的72.1%,这两个月份正是白琵鹭的越冬初期,是结束长距离迁徙的阶段,可能是白琵鹭补充能量的关键时期,这个时期越冬地恶劣的天气可能导致白琵鹭无法获得充足的能量,不利于能量的恢复,从而可能给种群造成不利的影响。  相似文献   

11.
Fluctuations in serum levels of testosterone (T) within a day, both with age and as a result of sexual stimulation, were examined in male beagle dogs. Eighty male dogs aged between 3 months and 16 years and bred in our laboratory were used under strictly controlled breeding conditions (temperature: 22 +/- 1 degree C, relative humidity: 55 +/- 5%, lighting time: 8:00 a.m.-8:00 p.m.). The level of T was measured by an RIA method. In order to examine the fluctuation in T level within a day, blood samples were obtained at 0:00, 6:00, 12:00 and 18:00 in each of five dogs aged 1.7 and 2.1 years. T levels fluctuated with a regular pattern that was lowest at 12:00, and increased to a peak at 18:00-6:00, thereafter decreasing until 12:00. In order to examine the change in T level with age, blood samples were obtained at 9:00, 12:00 and 16:00 from 70 dogs aged between 3 months and 16 years. The regular diurnal pattern of T level was usually seen, and the levels at 12:00 were always low and did not fluctuate at any age except for 6 months, and 13, 14 and 16 years. The T level at 9:00 increased to reach a peak at 4 years, whereas that at 16:00 did so at 2 years. T levels at 9:00 were significantly higher at 4-12 and 14 years than at 3 months, and were higher at 4 years than at 9 months.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
1980—1982年在青海省海北高寒金露梅(Potentilla fruticosa)灌丛地区,用标志重捕法(CMR)对自然栖息地中的根田鼠(Microtus oeconomus)进行了野外调查。本文主要分析了根田鼠种群数量变动特点和繁殖、存活及年龄结构与种群动态的关系,并试图探讨根田鼠种群的稳定机制。  相似文献   

13.
The common pistachio psylla, Agonoscena pistaciae Burckhardt & Lauterer (Hemiptera: Psyllidae), is known as the key pest of pistachio orchards in Iran. This pest passes the winter as adults. In this study, energy allocation changes in relation to ambient temperature were investigated in field-collected adults by measuring total body sugar, trehalose, glucose, sorbitol, myoinositol, glycogen, lipid, and protein contents. Glycogen content decreased with decrease in ambient temperature. The decrease in glycogen content was proportional to the increase in total body sugar, trehalose, myoinositol, and sorbitol contents. In January, with mean ambient temperature of 5.4°C, glycogen content was at the lowest level, whereas total body sugar, trehalose, glucose, and sorbitol were at the highest level. Total body sugar, trehalose, myoinositol, and sorbitol contents increased as temperature decreased from 22.7°C in October to 5.4°C in January. In conclusion, low molecular weight carbohydrates and polyols may play a role in winter survival and adaptation to cold of the common pistachio psylla by providing the required cryoprotection. Also, overwintering adults of the common pistachio psylla may store energy in the form of lipid for later utilization during the overwintering.  相似文献   

14.
The pistachio twig borer, Kermania pistaciella Amsel (Lepidoptera: Tineidae), a key pest of pistachio trees, is a monovoltine pest living inside the feeding tunnel of pistachio twigs for almost 10 months in a year and overwinters there as last instar larvae. In this study, we measured some physiological parameters of overwintering field collected larvae of the pest. There were no changes in trehalose, glucose, and myo-inositol contents, but there were differences in the levels of total simple sugar and glycogen during overwintering. Total sugar content at the beginning of overwintering (October) was at the lowest level (24.13 mg/g body weight) and reached to the highest level (55.22 mg/g fresh body weight) in November whereas glycogen content was at the highest level (44.05 mg/g fresh body weight) in October and decreased to 18.42 mg/g fresh body weight in November. Decrease in lipid content during the overwintering period was not significant. The highest and lowest levels of protein content were recorded in January and February, respectively. Supercooling points (SCP) of the overwintering larvae were stable and low (ranged between ?17.80 and ?25.10°C) throughout the cold season and no larva survived after SCP determination. The lowest cold hardiness (60 and 0.0% survival following exposure to ?10 and ?20°C/24 h, respectively) was observed for in November-collected larvae. Overwintering larvae of the pistachio twig borer rely mostly on maintaining the high supercooling capacity throughout the overwintering to avoid freezing of their body fluid.  相似文献   

15.
长江口九段沙湿地大型底栖动物群落结构的季节变化规律   总被引:7,自引:1,他引:6  
2004年11月至2005年10月,调查了长江口九段沙湿地大型底栖动物群落特征的季节变化及其土壤因子影响,共调查到大型底栖动物30种,主要由甲壳动物、环节动物、软体动物及昆虫幼体组成,光滑狭口螺(Stenothyra glabra)、堇拟沼螺(Assiminea violacea)、焦河蓝蛤 (Potamocorbula ustulata)、中国绿螂 (Glaucomya chinensis)和谭氏泥蟹(Ilyrplax deschampsi)为优势种,且生物密度四季变化明显.春季大型底栖动物生物密度和生物量处于最高水平,多样性指数最高.夏季密度和生物量最低,物种多样性也较低,分布较不均匀.秋、冬季生物种类数与生物量差异不显著,生物密度冬季较秋季高.春、夏、秋季底栖动物种类数、密度和生物量均未与土壤因子达到显著相关水平.冬季土壤湿度与有机质含量与底栖动物密度显著相关.  相似文献   

16.
Tissue nitrogen was assessed monthly for 16 months in five species of perennial macroalgae representing three phyla at one location in Rhode Island Sound. The species showed a remarkable similarity in their pattern of seasonal fluctuation in both nitrate and total nitrogen. The period of greatest accumulation (January through March) coincided with the period of highest concentration of inorganic nitrogen in the water, and for most of these algae it was also the time of-least growth. Conversely, the period of lowest tissue nitrogen (50% of the winter value, May through July) coincided with the period of lowest inorganic nitrogen in the water and highest algal growth. The greatest accumulation of nitrate was found in Laminaria saccharina (L.) Lamour. (80 μmol·g dry wt.?1), four times as much as that measured simultaneously in the other species and 560 times the ambient concentration. By April the concentration of internal nitrate had dropped to nearly undetectable levels, but in August it began to accumulate again—a pattern that was repeated in Chondrus crispus Stackh. In Ascophyllum nodosum (L.) Le Jolis, Fucus vesiculosus L. and Codium fragile subsp. tomentosoides (Van Goor) Silva, the period of negligible internal nitrate level extended from March to December. The greatest concentration of total tissue nitrogen was measured in C. crispus (4.8% dry wt.), double the maximum in L. saccharina (2.3% dry wt.).  相似文献   

17.
云南西双版纳桔小实蝇种群动态   总被引:26,自引:1,他引:26  
叶辉  刘建宏 《应用生态学报》2005,16(7):1330-1334
于1997年、2000年和2003年在云南西双版纳通过性诱剂诱捕对桔小实蝇种群动态进行了全年监测,并就气候因子及寄主种类对该种群变动的影响进行了系统分析.结果表明,桔小实蝇在西双版纳常年发生.当年11月至次年2月,桔小实蝇种群处于较低水平,3月以后种群数量逐渐上升,至6~7月形成一个种群增长高峰,此后至10月种群数量迅速下降.分析表明,影响桔小实蝇种群变化的重要因子是温度、降雨量和寄主种类.西双版纳各月均温位于桔小实蝇适温范围内,但12~2月的月平均最低温度低于桔小实蝇的适温范围,对桔小实蝇种群数量有一定抑制作用.降雨量是影响桔小实蝇种群数量变动的另一重要因子.月降雨量低于50 mm以下对桔小实蝇种群不利,而100~200 mm的月降雨量有助于桔小实蝇种群的增长.月降雨量大于250 mm以上将导致桔小实蝇种群数量下降.6~7月强降雨过程被认为是桔小实蝇在该时期种群数量下降的主要原因.芒果、番石榴、桃、梨、柑桔、龙眼和荔枝是桔小实蝇在该地区的主要寄主水果.其中,芒果和龙眼是当地桔小实蝇最喜好的寄主水果,其种植面积、挂果期和产量对桔小实蝇种群数量变动影响较大,被认为是影响该地区桔小实蝇种群变动的又一主要因素.  相似文献   

18.
Serum levels of L-thyroxine (T4) and L-triiodothyronine (T3) of the masu salmon, Oncorhynchus masou, were measured by radioimmunoassay during the months from March to September. Serum levels of T4 and T3 varied from 0.06 to 1.44 microgram and from 0.06 to 0.35 microgram per 100 ml serum respectively, although T4 content could not be detected in some specimens. T4 levels showed a seasonal fluctuation in which a higher value was observed in April when parr-smolt transformation was proceeding. T4 level in spring, particularly in April and June, was significantly higher in smolt than in parr. T3 content showed a small variation during the observed months and did not increase at smoltification, although the content tended to decrease to a minimum level in September when T4 level showed also the lowest level.  相似文献   

19.
Two populations of Phyllariopsis purpurascens from the Straits of Gibraltar area were investigated during 1990 and 1991. This area has very strong currents (~2·5 m s-1 at spring tide). The first sporophytes (less than 0·5 cm in length) were observed in April; they disappeared after the first storm period in October. The estimated number of spores produced in an unilocular sporangium was 64. The fertility period started in May and continued until October, but the maximum sorus surface area (27%) was reached in September. The maximum sporangial density was 1476±236 mm-2. The slow development of fertility and its correlation with the seasonal increase in temperature suggest that sporangial development is controlled by temperature and not by photoperiod. The drag effect produced by the strong currents (at spring tides and storm periods) is sufficient to break adult plants (with 0·01 m2 in surface intercepting the current). At the beginning of the sporophytic production cycle (210 days), the meristematic zone produces more tissue for blade growth than for stipe growth. Holdfast growth occurs in the first 3 months. The mortality was 90% for sporophytes 0–10 cm in length, and decreased to ~50% in adult plants. One cohort in the cycle has been identified. The net primary production (calculated by the graphic model of Allen) was 0·04 g dry weight m-2·day-1 from April to October (210 days). The production is among the lowest values estimated for seaweeds.  相似文献   

20.
为了解热带地区树木的季节性生长动态和规律,在西双版纳热带季节雨林利用高精度生长仪和微树芯法对落叶树种多花白头树的径向生长季节动态进行监测。结合木质部非结构性碳水化合物和环境因子的监测,分析其形成层活动和径向季节动态的生理生态驱动因子。结果表明: 在2020年,生长仪的监测显示,多花白头树于5月底(儒略日DOY:149.3±7.2)开始生长,8月底(DOY:241.0±14.7)生长结束,年生长量为3.12 mm,最大生长速率为0.04 mm·d-1。而微树芯法显示,扩大细胞3月9日(DOY:69.2±6.2)开始出现,9月19日(DOY:262.8±2.8)细胞加厚结束,木质部生长量为1.76 mm,最大生长速率为0.009 mm·d-1。多花白头树径向日生长量与生长季的降水、相对湿度、日最低气温、深度为20 cm的土壤含水量和温度呈显著正相关,而与日最高气温、水汽压亏缺、最大风速和水汽压呈显著负相关。多花白头树边材淀粉含量和可溶性糖含量均在生长季开始之前保持较高水平,淀粉含量在3月底达到最低,而可溶性糖含量5月中旬达到最低,随着生长季的结束淀粉和可溶性糖的含量分别在10月中旬和12月底达到最高。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号