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1.
Field active body temperatures (Tb) and operative temperatures (Te) were assessed in a population of Uromastyx aegyptia microlepis at Mahazat as-Sayd Protected Area, Saudi Arabia. In summer Tb ranged between 23.2 and 47.2 °C, in winter between 23.0 and 45.1 °C and in spring between 25.5 and 45.9 °C. There is a significant difference between respective Tb and Te distributions which suggests that U. a. microlepis is an active thermoregulator. Above ground activity is very variable between seasons, with the highest activity level in spring. In winter the animals showed an unimodal activity profile. In spring and summer the lizards exhibit bimodal activity profiles with afternoon activity being generally lower than morning activity levels. Species distribution models were calculated to estimate the future impact of global warming on this taxon. Estimates on the basis of temperature data suggest that the range size on the Arabian Peninsula might be stable but with a remarkable decrease of environmental suitability of up to 70-80%. Based on a synthesis of thermo-ecological data and species distribution models we consider climate warming as a potential threat to the survival of the species. 相似文献
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In arid environments, limited resources may compromise allocations to reproduction, while unpredictable rainfall may confound the timing of reproductive events. Here we evaluate how female tent tortoises (Psammobates tentorius tentorius) allocate resources to reproduction while coping with low and unpredictable rainfall. Vitellogenesis in tent tortoises started in autumn, when rainfall was highest and most predictable. Tent tortoises required a high body condition and large follicles to ovulate their first clutches, but a temperature threshold for ovulation may have prevented breeding during the winter months. Females produced small clutches (1.78±0.63; 1–3 eggs) but produced several clutches (3.7±1.6; 1–6 clutches) from spring to late autumn. Clutch frequency (CF) was correlated to body condition, and CF rather than clutch size (CS) determined annual fecundity. Although body size influenced egg size, body size had no effect on CS, CF or fecundity. There was no trade-off between relative egg size and CS. The small clutches of tent tortoises limit the risks of producing too many offspring at one time, a scenario that may leave females without resources for their own needs. When clutches are small, an extended breeding season enhances reproductive output by providing females more time and opportunities to leave offspring. 相似文献
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We examined the monthly shrub use and the thermal utility of the desert shrub, Artemisia monosperma, by the globally endangered Egyptian tortoise, Testudo kleinmanni, in Sinai, Egypt. A. monosperma is a common desert shrub that is often used by the Egyptian tortoise as a refuge. Egyptian tortoises had the highest mean carapace temperature and lowest carapace temperature range during summer months, which coincided with the aestivation period and the Egyptian tortoise's use of larger shrubs. Our results suggest that the thermal characteristics of larger shrubs are important to the microhabitat use of the Egyptian tortoise and likely long-term survival. Larger shrubs were effective as thermal refuges that ameliorated and stabilized micro-climatic variation. Smaller shrubs were not an adequate thermal refuge in the summer because the mean temperature, and its fluctuation range beneath them was too high to offer adequate refuge during aestivation. The tortoises used the smaller shrubs in the fall, winter, and spring seasons for basking, thermoregulation, and concealment and used shrubs with a cover diameter greater than one meter during the aestivation season. The future conservation of the Egyptian tortoise should focus on protecting and restoring existing habitat by maintaining large perennial shrubs for refuge and aestivation sites. 相似文献
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黄河上游水电工程对局地气候的影响 总被引：4，自引：0，他引：4
本文阐述了黄河上游段水电工程概况，并以刘家峡和龙羊峡水库为主对库周各站建加前后各５年或１０年的气象资料进行了对比分析，揭示了水库对周围地区各气候因子影响程度。 相似文献
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We examined large-scale climatic and small-scale biotic and abiotic factors affecting Pinus jeffreyi (Pinaceae) seedling establishment at its low-elevation boundary along the conifer forest-sagebrush steppe ecotone in eastern California, USA. In three successive growing seasons, P. jeffreyi seedlings were planted in three microhabitats (under Artemisia tridentata or Purshia tridentata canopies, and in open intershrub spaces) at a site within the ecotone (2300 m) and at a lower-elevation site (2200 m). We measured Photosynthetically Active Radiation (PAR; 400–700 nm), soil moisture and temperature, and air temperature in the three microhabitats, and monitored seedling survival, drought stress, and herbivory. At both sites, soil moisture decreased two- to six-fold between May and August of each summer. Maximum and minimum daily air temperatures were higher and lower, respectively, in intershrub areas, as were maximum daily soil temperatures and maximum daily PAR. At the ecotone site, mean P. jeffreyi seedling survival was longest following a very wet winter and shortest following a dry winter. For both elevations, seedlings had shorter survival times in intershrub microsites as compared to shrub microsites. Drought and herbivory both influenced seedling mortality within each microhabitat, but drought was the major determinant of seedling mortality by the end of each summer. 相似文献
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上海世博园后滩湿地大型底栖动物群落特征与环境分析 总被引：1，自引：0，他引：1
上海世博园后滩湿地是中国2010年上海世界博览会规划区的重点建设项目。对世博园后滩湿地潮间带底栖动物群落特征与生物多样性进行了春、夏、秋、冬4个季节的调查研究,并对该湿地水体污染状况及影响底栖动物分布的因素进行分析与评估。结果表明:世博园后滩湿地底栖动物主要由环节动物、软体动物、节肢动物与纽形动物组成,共计18种;物种数在夏季最丰富,春季次之,冬季物种数最少,其中A断面物种数大于B断面;群落生活类群面上生活类群(GS)/面下生活类群(GSB)在冬季最大,春季次之,秋季群落生活类群GS/GSB最小,其中B断面群落生活类群GS/GSB大于A断面;底栖动物群落的Margalef物种丰富度指数(d)在夏季最大,春季次之,冬季丰富度指数最小;Shannon-Wiener指数(H′)在夏季最大,春季次之,秋季最小;Pielou均匀度指数(J)为:冬季最大,夏季次之,秋季最小;Simpson优势度指数(D)为:秋季最大,春季次之,夏季最小;采用寡毛生物指数值和生物多样性指数对该湿地水体污染状况进行了评价,该园区水质污染程度为中度污染。 相似文献
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A traversing micro-erosion meter (TMEM) was used to measure micro-scale surface changes in a 45 cm2 area of an intertidal mudstone shore platform on Kaikoura Peninsula, New Zealand, with hourly readings taken over 5 days for two seasons, within 4 h either side of low tide. For all monitoring events, the relative height of a total of 120 co-ordinates were obtained, resulting in 4200 and 4800 measurements for the summer and winter seasons respectively. Within seasons, samples were grouped according to the presence of rain or no rain. Significant changes were found in the micro-topography with variations in temperature and among rain and no rain sample groups. For both seasons, in the absence of rain, there were positive linear relationships between rock surface temperatures and rock surface elevations, and regression analysis explained 42.3% and 46.5% of this variation for the summer (y = 0.098 + 0.004x; p-value = 0.007) and winter (y = 0.007 + 0.012x; p-value < 0.001) seasons respectively. It is suggested that incorporating weather readings alongside measurements of surface change could not only improve extrapolations of shore platform erosion from short-term studies, but also differentiate fluctuations in rock surfaces due to changes in rock surface temperatures from other processes involved in shore platform erosion. 相似文献
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季节变化对全球气候变化的响应——以湖北省为例 总被引：8，自引：0，他引：8
根据湖北省10个代表站1951(或建站)~2006年逐日平均气温,计算分析了四季初日和长度及其变化趋势,以揭示气候季节对全球气候变暖的响应。结果表明:(1)湖北省平均春、夏、秋、冬四季初日分别为3月22日、5月27日、9月27日、11月27日,四季长度分别为65.7、122.8、60.9、115.6d,且时空差异明显;(2)56a来湖北省平均入春、入夏分别提前2.8、1.6d,入秋、入冬分别推后4.0、6.1d;(3)56a来湖北省平均冬季缩短8.9d,夏季延长6.3d,秋季延长2.0d,春季无变化;荆州夏季延长21.1d,武汉冬季缩短17.0d。 相似文献
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蒙古野驴(Equus hemionus)昼间行为时间分配初探 总被引：1，自引：0，他引：1
于2007 年和2010 年采用焦点动物取样法研究了新疆卡拉麦里山有蹄类野生动物保护区蒙古野驴昼间行为时间分配和活动节律,共采集行为数据460 h,观察蒙古野驴2 760 头次,将蒙古野驴昼间行为分为采食、移动、警戒、休息和“其他”5 类。采用卡方检验分析不同季节各种行为时间分配,结果表明：季节因素对蒙古野驴行为时间分配存在极显著影响（χ2=79.06,df=12,P<0.01）。采用ANOVA分析同季节不同行为间差异,结果表明,春季：移动、警戒、“其他”两两间无显著差异（[WTBX]P＞0.05）,其余两两间差异显著（P＜0.05）;夏季：仅移动与“其他”间无显著差异（P＞0.05）;秋冬季：仅警戒与“其他”间无显著差异（P＞0.05）。对蒙古野驴昼间活动节律研究结果表明,蒙古野驴采食时间比例在春季各时段均较高（＞45%）,仅中午（14:00～15:00）有1个低谷（27.62%）,夏秋季则为晨昏采食模式,冬季采食峰值（87.85%）在中午时段（13:00～14:00）。休息和采食高峰在各季节交叉出现,呈现此消彼长的趋势。各季节移动主要发生在晨昏时段。蒙古野驴以特定的行为时间分配模式和活动节律适应环境条件季节性变化,如气候条件、食物资源、人为干扰、生理期、昼间长度、捕食风险等。 相似文献
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Populations of the winter annual Eruca sativa in Israel are distributed along a climatic gradient, from Mediterranean mesic habitats in the north to semi-arid and arid habitats in the south. Seed cohorts of five populations sampled across the gradient were produced in a common-garden experiment, and their germination was tested under continuous light or darkness at 5–35 °C, as well as with alternating 30/20 and 25/15 °C temperatures under a 12/12 h photoperiod. Germination was enhanced by light and by increasing temperature. Under constant temperatures maximal germination of arid and semi-arid populations was lower than in the mesic populations, suggesting on higher levels of primary dormancy with increasing aridity. Seeds that did not germinate in darkness or at low temperatures in light, germinated almost fully when exposed to GA3 at 25 °C, indicating that imbibition under less favorable conditions induces secondary dormancy in E. sativa. Daily alternating temperatures did not affect or even reduced seed germination compared to constant 25 and 30 °C in continuous light. Exposure of dry seeds to 30 °C before imbibition increased germination to ≥80% in seed cohorts of all populations. These responses to light and temperature indicate that adaptation of E. sativa to the Mediterranean environment is associated with the ability to germinate under the relatively warm autumn temperatures, and is enhanced by exposure to high temperature during the dry summer. 相似文献
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Keith G. Henderson 《自然地理学》2013,34(1):23-37
Atmospheric humidity as measured by dew-point temperatures is an important component of the climate of the southern United States. The South experiences the country's highest dew-point temperatures throughout the year. A gradient is established between moist air along the Gulf and Atlantic coasts inland toward the drier areas of northwestern Texas. This gradient is strongest in winter and weakest in summer when consistent southerly circulation maintains humid conditions throughout the region. Interannual variability also is largest in the winter and smallest in summer. Dew-point temperatures are strongly related to air temperatures in the non-summer season, but are more fundamentally linked to air mass and circulation changes. Recent increases in southerly flow in the spring and autumn seasons have led to a significant increase in dew-point temperatures in many portions of the region. However, there is no evidence at this time to suggest that increased evaporation from greenhouse warming has altered dew-point temperatures in the southern United States. 相似文献
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塔克拉玛干沙漠地表潜热时空特征分析 总被引：6，自引：4，他引：2
利用1979年3月至2004年2月月平均的NCEP/DOE再分析地表潜热资料,在分析塔克拉玛干沙漠四季潜热基本气候特征的基础上,通过EOF方法,对沙漠地表潜热异常变化的空间结构和时间演变趋势作了诊断研究。结果表明：①沙漠地区夏季潜热最大,春季和秋季次之,冬季最小;靠近山区的沙漠西部、西北部地区四季明显大于中、东部地区。②根据四季地表潜热距平场的EOF分析,该区潜热异常主要有全区一致型、南北差异型以及西北—东南差异型三种常见的分布模态。③25 a期间,塔克拉玛干沙漠地表潜热在第一空间尺度上四季都有不同程度增强的趋势;在第二空间尺度上,春季沙漠北部、西北部有减弱的趋势,南部、东南部有增强的趋势,而冬、夏、秋季变化趋势不是很大。 相似文献
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玉溪干旱季节分布特征及成因分析 总被引：1，自引：0，他引：1
1971～2009年玉溪市干旱发生概率最大的是冬季为85.0%,依次是春季、秋季和夏季,出现频率分别为74.4%、66.7%和33.3%。2000年以来,随着全球气候变暖,干旱发生的概率增大,特别是重旱到特旱年发生次数与20世纪相比明显增多,其中除春季变化不大外,冬、夏季分别增加了8%、6.7%,秋季增加最大为12.8%。造成玉溪干旱灾害的原因主要是冬春季受较强的偏西气流控制,夏秋季西太平洋副热带高压异常偏强、印度季风异常活跃等大气环流异常,另外自然地理复杂、生态环境遭破坏也是干旱增多的因素之一。 相似文献
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北极地区以南生成并向北移动进入极区的气旋,在移动发展过程中常伴随大风、降水和升温等过程,对中低纬度地区物质和热量向极地输送起着重要作用,并对极区大气、海洋和海冰的变化产生一定影响。基于欧洲中期天气预报中心(ECMWF)发布的1979—2015年的海平面气压再分析数据产品,利用气旋自动识别和追踪算法,开展气旋的识别和追踪,获得向极跨越70°N气旋的数量、强度、活动轨迹及北向运动纬距等主要特征如下:该类气旋在数量上,春、冬季多于夏、秋季,年总数量和春、秋、冬季均呈减少趋势;强气旋易发于冬季,弱气旋多发于夏季;该类气旋活动轨迹,冬季集中分布在海上,夏季在陆地上;该类气旋北向运动纬距整体平均为9.2°,冬季平均最大,为10.2°,夏季平均最小,为7.3°;在年际变化上,年平均和春、冬季平均呈增长趋势,夏、秋季平均呈减少趋势;在年代际变化上,年平均和夏、冬季平均从1979—1988年到1989—1998年阶段都是减小的,到1999—2008年阶段是增大的,其后再减小,春、秋季则无明显趋势变化。 相似文献
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Tiny cryptanthe (Cryptantha minima Rydb.) is an endangered annual plant adapted to prairie sand dunes of Canada. Thermal time and hydrothermal time models were used to quantify the effect of temperature and water potential on seed germination and to relate it to field conditions. Tiny cryptanthe seeds had a base temperature of ?3.9 °C for germination. Final germination percentage was highest at temperatures near the freezing point. Seeds required approximately 130.6 °C d to reach 50% germination under optimal water conditions. Seed germination was sensitive to water stress and large seeds had lower germination than small ones especially at reduced water potentials and higher temperatures. The high potential germination and low seed dormancy indicate that tiny cryptanthe lacks a dormancy mechanism, but the unique germination response to temperature enables it to fully utilize water from spring snowmelt before drought in the summer. Future climate change with higher temperatures could reduce regeneration success of this species unless there is an associated increase in winter and spring precipitation. 相似文献
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1956—2013年曹家湖流域径流深变化 总被引：1，自引：1，他引：0
在古浪河水文站观测数据基础上,运用数理统计方法对曹家湖流域1956—2013年径流深变化的研究表明:(1)曹家湖流域春、夏、秋、冬季径流深的变化趋势均表现为20世纪80年代偏多,2000年后偏少,这两个时段内年径流深与季节径流深变化一致;除冬季外,其他季节20世纪60年代径流深均高于多年平均;夏、冬季和年径流深70、90年代偏多。(2)就年际变化而言,春、夏、秋季径流深均表现为减小趋势,但不显著,冬季径流深呈不显著微弱增加趋势。受季节变化的影响,年径流深也表现出减小的态势。(3)各季节径流深变化均存在4~18a的短周期变化,除春季外,其他季节径流深变化还存在28~30a的长周期变化。(4)研究区春、秋、冬季和年径流深分别在2008、1961、2007、2007年突变减小,除冬季外,其他均未通过95%的显著性水平检验;研究时段内,夏季径流深经历了两次突变显著减少,分别出现在1966年和2007年。(5)研究区春、夏、秋季以及年降水量与径流深之间存在显著的正相关关系,冬季降水量与径流深存在不显著的负相关关系。 相似文献