Are populations of the candy barrel cactus (Echinocactus platyacanthus) in the desert of Tehuacán, Mexico at risk? Population projection matrix and life table response analysis     

Cecilia Jiménez-Sierra  Maria C. Mandujano 《Biological conservation》2007,135(2):278-292

Echinocactus platyacanthus is a candy barrel cactus endemic to Mexico and an endangered species owing to its exploitation and the destruction of its habitat. The population dynamic of this species is analyzed using matrix models. Three consecutive censuses were carried out (1997, 1998, and 1999) for six populations of this species in the Tehuacán-Cuicatlán Biosphere Reserve. Fruit contain many seeds (mean = 171 ± S.E. 11.03 seeds/fruit); seedling establishment and survival are low (2 × 10⁻⁶), and fecundity increases as the diameter of the individuals increases (62 seeds in adult 1-4322 in adult 4). The rates of population growth (λ) range from 0.9285 to 1.0005. Elasticity values for demographic processes indicate that the stasis of the adults is the greatest contribution (S = 0.982), followed by growth (G = 0.017) and fecundity (F = 0.001) to λ. The populations are located in the lower left corner of the demographic triangle; however, there are variations for a given population from one year to the next. Life table response experiments indicate that although there are local variations, the most important differences in the values of λ between populations and between years are associated with changes in the stasis of the adults. The disturbance index is not directly related to population density or to the current value of λ. The protection of adult E. platyacanthus must be taken into account for the management of this species and its conservation in the study area.  相似文献   

Using functional traits to assess the role of hedgerow corridors as environmental filters for forest herbs     

Valrie Roy  Sylvie de Blois 《Biological conservation》2006,130(4):592-603

Linear habitats such as hedgerows can constitute important refuges for native flora and fauna, possibly providing connectivity between landscape elements. The effectiveness of these functions, however, depends on the ability of linear habitats to benefit a significant proportion of the local species pool and their functional attributes. This study aims to identify life-history traits that appear to either limit or facilitate survival or colonization of forest herbs in hedgerows. The distribution patterns of 47 native forest herbaceous species and their associated traits were compared in a system of hedgerows and attached forest patches of southern Quebec. Although 83% of the species surveyed in forest patches were present in hedgerows, significant differences in abundance suggest the existence of a selective pressure on forest species in linear habitats. Early spring flowering was negatively associated with hedgerows, possibly because of unfavourable microclimatic conditions. Seed dispersal phenology partly mirrors results for flowering phenology with early summer dispersal and late fall dispersal being less common in hedgerows than in forests. Slow dispersal mainly through myrmecochory was also less common in hedgerows compared to forest sites, suggesting a selective pressure on slow dispersers in linear habitats. The capacity for vegetative propagation was positively associated with hedgerows, possibly because it provides an alternative strategy to survive and expand when conditions are less favourable for sexual reproduction. Our approach highlights traits that can help determine the vulnerability of native forest species in linear habitats or their likelihood to benefit from the maintenance of wooded corridors in an inhospitable matrix.  相似文献   

区域经济发展对生态环境的压力与生态省建设的对策研究     

张文和 《水土保持学报》2005,19(2):191-194

在明确人与自然关系的生态伦理基础上,提出实现经济生态化和生态经济化是浙江建设生态省的关键,做到“三生共赢”是实现人与自然和谐相处、建设生态浙江的根本保证  相似文献   

黄土高原小流域土壤总碳分布与储量研究   总被引：4，自引：0，他引：4  

贾宇平  马义娟 《水土保持通报》2005,25(5):17-19

以位于黄土高原典型沟壑区的砖窑沟流域为研究区,通过对流域内土壤分层取样分析,运用地统计学方法探讨了流域土壤总碳的空间分布特征,并在运用Kriging插值法生成流域土壤总碳含量空间分布图的基础上,通过构建土壤碳储量估算模型,估算出流域土壤总碳储量。结果表明,砖窑沟流域土壤总碳含量总体上随着深度增加而减少,同一深度层内土壤总碳含量沿梁峁顶部→梁峁坡→沟坝地依次减少;流域内0—100 cm深度内土壤总碳储量占0—200 cm深度内土壤总碳储量的51.8%。100—200 cm深度的土壤碳储量在0—200 cm深总碳储量中仍占较大比重。因此,在研究黄土高原土壤碳储量时,100 cm深度以下的土壤碳储量不容忽视。  相似文献   

辽东山地老秃顶子冰缘地貌植物群落多样性   总被引：1，自引：0，他引：1  

孙明扬  张华  罗璇  刘剑刚  祝业平  兰玉波  王颖  马明军 《水土保持通报》2016,36(1):75-81

[目的]研究老秃顶子冰缘地貌植物群落的多样性特征,为其上植被的保护提供科学依据。[方法]基于48个样地的群落调查数据,采用物种丰富度指数和α多样性指数,对石海、石河、石流坡3种冰缘地貌植物群落的多样性进行定量研究,并对其影响因素进行分析。[结果](1)植被划分为22个群系,6种植被类型,其中石河地貌上植被类型以落叶阔叶林、针阔混交林为主;石海地貌上以灌丛、灌草丛为主;石流坡地貌上以针阔混交林为主,22个群系对应分布于3种地貌,有些群系具有专有性,有些具有共有性。(2)3种冰缘地貌群落总体综合多样性指数大小依次为:石河石流坡石海,乔木层、灌木层综合多样性指数变化均次为:石河石流坡石海;草本层依次为石海石流坡石河。(3)不同植被类型、不同植物群系的物种多样性因所处的生境特征不同而出现差异。(4)地形因子中的海拔对植物群落物种多样性指数影响最大,且灌木层的物种多样性对海拔敏感程度最小。[结论]研究区植物群落的多样性特征较好,海拔是影响多样性指数的主导因子。  相似文献   

Ground beetles (Carabidae) and edge effect in oak-hornbeam forest and grassland transects     

Tivadar Molnr  Tibor Magura  Bla Tthmrsz  Zoltn Elek 《European Journal of Soil Biology》2001,37(4):297

We evaluated ground beetle diversity in relation to forest edge between an oak-hornbeam forest and adjacent herbaceous grassland. To test our hypothesis that the diversity of ground beetles was higher in the forest edge than the interior, pitfall trap samples were taken along two forest-grassland transects in northern Hungary. The diversity of ground beetles was significantly higher at the forest edge and in the grassland than in the forest interior. Ground beetle assemblages in the forest interior, forest edge and grassland could be separated from each other by ordination. Indicator species analysis detected five groups of species: habitat generalists, grassland-associated species, forest generalists, forest specialists, and edge-associated species. Rank correlation indicated leaf litter, herb, canopy cover, and prey abundance as the most important factors influencing carabid diversity. The high diversity of the forest edge resulted from the presence of edge-associated species and of species characteristic of adjacent habitats. Forest edges seem to play an important role in maintaining diversity. Serving as source habitats, edges also contribute to the recolonisation by ground beetles after habitat destruction or other disturbance in the adjacent habitats.  相似文献   

Impact of communal land use and conservation on woody vegetation structure in the Lowveld savannas of South Africa   总被引：2，自引：0，他引：2  

K.J. Wessels  R. MathieuB.F.N. Erasmus  G.P. AsnerI.P.J. Smit  J.A.N. van AardtR. Main  J. Fisher  W. MaraisT. Kennedy-Bowdoin  D.E. KnappR. Emerson  J. Jacobson 《Forest Ecology and Management》2011,261(1):19-29

Millions of people rely on savannas for ecosystem services, such as the provision of grazing and fuel wood, so it is important to determine the extent to which utilization affects woody vegetation resources. Using airborne LiDAR from the Carnegie Airborne Observatory (CAO), we quantified and compared tree canopy cover and height distributions between areas of contrasting management in the Lowveld savanna region of South Africa - a region connecting communal landscapes with heavy utilization (especially fuel wood harvesting) to fully protected public (Kruger National Park - KNP) and private reserves (SabiSand Game Reserve - SSGR) that conserve biodiversity. Differences in total woody vegetation cover and cover within functional height classes (1-2 m, 2-3 m, 3-5 m, 5-7 m and >7 m) were investigated between 7 sites located within (i) conservation areas (in KNP, SSGR), (ii) communal rangelands or (iii) cultivated fields in communal areas. The impact of human utilization on wood resources in the communal areas varied widely between sites. Heavy utilization on gabbro substrate greatly reduced total woody cover of the rangelands, while two other communal rangelands that were presumably less intensively utilised had double the total woody cover of conservation areas. Rangelands and fields in most of the communal sites had more vegetation cover in the 5-7 m and >7 m classes than most of the conservation sites, presumably due to the absence of elephants in communal rangelands and the active preservation of large fruiting trees. On granite substrates, which account for the majority of the study area, there was a 50% reduction in woody cover below 5 m in communal rangelands. Although large trees were clearly being conserved in communal rangelands and fields, there was a relatively low cover of vegetation below 5 m, which raise doubts about recruitment and long-term sustainability of the tree resources. These results in conjunction with other studies based on the CAO LiDAR data for experimental burn plots and large mammal exclosures in KNP, suggest that communal land use on granite substrates have a higher impact on the woody cover below 5 m than both elephants and fire.  相似文献   

论人与自然的和谐发展     

张先宝  杨泽斌  廖志凌  张新华 《农机化研究》2006,(4):31-33

地球是人类赖以生存的唯一大环境。人类自诞生以来,就与大自然形影不离,人与自然的关系曾一度出现原始的和谐。但随着社会的进步和科技的发展,人类开始了向大自然疯狂索取的历程。绿色在消退,灰色在蔓延,地球千苍百孔,致使人与自然关系的恶化,于是人类的灾难接踵而来,让人触目惊心。在可持续发展战略的指导下,加强环保意识,采取有力的环保措施,再创人与自然的和谐势在必行。  相似文献   

Oxygen reserve index as a noninvasive indicator of arterial partial pressure of oxygen in anaesthetized donkeys: a preliminary study     

Luca Bellini  Brighton T. Dzikiti  Giulia Maria De Benedictis  Felix R. Algarin Sepulveda  Jill K. Maney 《Veterinary anaesthesia and analgesia》2021,48(3):388-392

ObjectiveTo evaluate the oxygen reserve index (ORI) as a noninvasive estimate of the PaO₂ during moderate hyperoxaemia [100–200 mmHg (13.3–26.6 kPa)], and to determine ORI values identifying PaO₂ > 100, > 150 (20.0 kPa) and > 200 mmHg in anaesthetized donkeys with an inspired fraction of oxygen (FiO₂) > 0.95.Study designProspective observational study.AnimalsA group of 28 adult standard donkeys aged (mean ± standard deviation) 4 ± 2 years and weighing 135 ± 15 kg.MethodsDonkeys were sedated intramuscularly with xylazine and butorphanol; anaesthesia was induced with ketamine and diazepam and maintained with isoflurane in oxygen. An adhesive sensor probe was applied to the donkey’s tongue and connected to a Masimo pulse co-oximeter to determine ORI values. An arterial catheter was inserted into an auricular artery. After ORI signal stabilization, the value was noted and PaO₂ determined by blood gas analysis. The Pearson correlation coefficient was used to assess the relationship between ORI and PaO₂ for oxygen tension < 200 mmHg (< 26.6 kPa). The Youden index was used to identify the value of ORI that detected PaO₂ > 150 and 200 mmHg (20.0 and 26.6 kPa) with the highest sensitivity and specificity.ResultsA total of 106 paired measurements were collected. A mild positive correlation was observed between ORI and PaO₂ for values < 200 mmHg (26.6 kPa; r = 0.52). An ORI > 0.0, > 0.1 and > 0.3 indicated a PaO₂ > 100, > 150 and > 200 mmHg (13.3, 20.0 and 26.6 kPa) with negative predictive values > 94%.Conclusions and clinical relevanceORI may provide a noninvasive indication of PaO₂ > 100, > 150 and > 200 mmHg (13.3, 20.0 and 26.6 kPa) in anaesthetized donkeys with an FiO₂ > 0.95, although it does not replace blood gas analysis for assessment of oxygenation.  相似文献   

激荡时代中的古典情怀——论梁实秋“人性”观的形成及时代效应     

王敏 《四川畜牧兽医学院学报》2007,5(6):100-103

梁实秋的“人性论”，以儒学伦理人性为精神依归。以西方新人文主义人性论为理论基础。他选择了内在视角，以具有共通情感与理性的人来取代“阶级性”的人。反对阶级人性论；在“情感”与“理性”的二维之间。强调理性的支配作用。批判五四新文学、无产阶级文学“浪漫主义式的情感泛滥”。梁实秋人性观强调普遍性、社会性、稳定性。排斥差异性、个体性、变动性。体现出激荡的现代文坛中一份独特的古典情怀。  相似文献