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1.
通过对福建万木林自然保护区常绿阔叶林群落101种乔木、灌木叶的N、P化学计量学特征分析,结果显示:同一群落内种间的叶N、P含量和N/P存在极大变异,叶N含量变化范围为10.76～34.14 mg.g-1,几何平均值为17.33 mg.g-1;叶P含量变化范围为0.28～2.93mg.g-1,几何平均值为0.94 mg.g-1;N/P变化范围为6.47～34.90,几何平均值为18.49.群落叶N/P平均水平均高于全球、全国和中国东部南北样带的平均水平,说明本区的常绿阔叶林更易受P限制.在不同生长型中,只有落叶木本与常绿木本、落叶乔木和常绿乔木的叶片N、P含量存在显著差异(P<0.001;P<0.05),而不同生长型叶片N/P无显著差异.不同科之间,只有大戟科叶的N含量与其他科之间存在差异(P<0.05),其余科之间的N、P含量和N/P均不存在显著性差异. 相似文献
2.
福建万木林101种常见木本植物叶片N、P化学计量学特征 总被引：1，自引：0，他引：1
通过对福建万木林自然保护区常绿阔叶林群落101种乔木、灌木叶的N、P化学计量学特征分析,结果显示:同一群落内种间的叶N、P含量和N/P存在极大变异,叶N含量变化范围为10.76～34.14 mg·g-1,几何平均值为17.33 mg·g-1;叶P含量变化范围为0.28～2.93mg·g-1,几何平均值为0.94 mg·g-1;N/P变化范围为6.47～34.90,几何平均值为18.49.群落叶N/P平均水平均高于全球、全国和中国东部南北样带的平均水平,说明本区的常绿阔叶林更易受P限制.在不同生长型中,只有落叶木本与常绿木本、落叶乔木和常绿乔木的叶片N、P含量存在显著差异(P＜0.001;P＜0.05),而不同生长型叶片N/P无显著差异.不同科之间,只有大戟科叶的N含量与其他科之间存在差异(P＜0.05),其余科之间的N、P含量和N/P均不存在显著性差异. 相似文献
3.
科尔沁沙地中南部34种植物叶功能性状及其相互关系 总被引：3，自引：2，他引：1
以科尔沁沙地中南部34种主要植物为研究对象,分别测定叶片鲜重(FW)、干重(DW)、干物质含量(LDMC)、面积(LA)和比叶面积(SLA),比较不同生活型(一二年生草本、多年生草本、灌木)和功能型(C3、C4植物)的叶片性状的差异性,探讨沙地植物叶片性状相互之间的内在联系及其对环境的适应性。结果表明:一二年生草本的LDMC(0.23 g·g-1)显著小于多年生草本(0.31 g·g-1)和灌木(0.32 g·g-1);而一二年生草本的SLA(22.14 m2·kg-1)显著大于多年生草本(17.18 m2·kg-1)和灌木(13.41 m2·kg-1)。一二年生和多年生C4植物的LDMC显著大于C3植物;多年生C4植物SLA显著大于C3植物;C3植物的LDMC表现为一二年生草本<多年生<灌木。沙地植物的叶鲜重、叶干重和叶面积三者间极显著正相关,植物叶干重与SLA显著负相关;C4植物和多年生植物叶干重与SLA显著负相关。沙地不同生活型、功能型植物叶片的功能性状差异明显,沙地灌木和多年生植物能够较强的适应干旱环境,一二年生草本则具有较强的保持体内营养和获取土壤资源的能力。 相似文献
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川西米亚罗林区云杉天然林与人工林的群落特征比较 总被引：2，自引：0，他引：2
云杉林是四川西部山区重要的群落类型,为了解云杉天然林和人工林在物种组成、物种多样性以及群落结构等方面的差异,促进该区域植被的恢复与重建,我们设置典型样地对两种林型进行了详细调查,通过比较分析表明:在川西米亚罗林区,林龄在30 a左右的云杉林,其天然林乔木层、灌木层的物种数以及其所属科、属数均明显比人工林多一些,而草本层物种数相差不大;但从物种多样性指数方面看,除天然林乔木层物种多样性要明显高于人工林外,二者在灌木层和草本层上无显著差异.天然林和人工林乔木层的生长状况无显著差异,天然林灌木层物种的平均密度和平均高度要显著大于人工林,平均盖度则没有显著差异;草本层各群落特征指标在两种林型之间没有显著差异.但是天然林乔木层、灌木层和草本层的物种个体数在不同样地之间的变幅均要比人工林小.物种相似性指数的比较表明,天然林与人工林内物种组成较为一致,没有显著差异. 相似文献
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为了研究科尔沁沙地植物及叶片的C、N元素在沙丘固定过程中的化学计量差异及变化规律,在流动沙丘、半固定沙丘、固定沙丘、草地4种生境上分别采集整株植物样品和叶片样品,测定其C、N元素含量,并在群落水平和功能型水平上展开分析。结果表明:(1)随着沙丘的固定,植物群落及群落叶片的C含量逐渐上升而N含量逐渐下降,且C含量的变异系数较N含量小;(2)各生境植物及叶片C、N含量表现为灌木一年生植物、C3植物C4植物、豆科植物非豆科植物,各功能型植物的C、N含量正相关于其叶片的C、N含量;(3)沿沙丘固定梯度,一年生、C4与非豆科植物及其叶片C含量趋于上升,而一年生、多年生、C3、非豆科植物及其叶片N含量趋于下降。沙丘固定过程中群落C含量的变化主要源于一年生、C4、非豆科植物,而N含量的下降则受草本、C3、非豆科植物的共同影响。适当补植灌木、C3植物、豆科植物对于该地区的固C效率和生物固N以及改良土壤肥力会起到积极作用。 相似文献
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腾格里沙漠植被特征 总被引：1，自引：0，他引：1
《中国沙漠》2020,(4)
腾格里沙漠植被在维持沙漠生态系统稳定、促进生物多样保护及防风固沙等方面发挥着极其重要作用。在实地调查和查阅资料的基础上,划分了腾格里沙漠植被类型,分析了典型植物群落数量特征。结果表明:(1)腾格里沙漠植被类型较多,有6个植被型组、17个植被(亚)型、35个植被群系,具有典型的荒漠化草原植被特征。植被空间分布差异明显,南部流沙分布较广,植被类型单一,北部戈壁与沙漠交错分布,植被类型及物种组成相对丰富。(2)腾格里沙漠共有天然种子植物60科201属382种,多年生草本、一年生草本和灌木分别占总物种数的44.50%、25.92%和21.99%,乔木、寄生草本和水生草本数量较少。(3)腾格里沙漠典型灌木群落中,一年生草本占有较大比例,多年生草本次之,灌木所占比例相对较小,灌木常为群落优势种,属于群落稳定层片,而一年生草本数量随降雨变化较大,属于不稳定层片。(4)群落多样性南北差异较大,沙漠南部群落物种组成相对单一,物种丰富度、Simpson指数、Shanon-wiener指数、种间相遇率相对较低,沙漠北部群落物种组成丰富,多样性指数高,生态优势度不明显。 相似文献
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河南宝天曼化香林特征及物种多样性 总被引：2，自引：0，他引：2
根据10块样地的野外调查材料,对河南宝天曼化香林的土壤性质、植物区系成分、群落外貌、群落结构以及物种多样性特征进行了初步分析。结果表明:(1)化香林土壤较贫瘠,区系组成较丰富,其属的分布类型以温带性质的属最多,热带性质的属也占一定比例;(2)化香林的生活型以高位芽为主,叶级谱中以中型叶为主;(3)化香林的垂直结构可分为乔木层、灌木层、草本层,亦有少量的层间植物;(4)化香林的优势种显著,群落物种的丰富度、多样性、均匀度指数的总趋势为灌木层>草本层>乔木层,但在海拔梯度上的分布并未表现出明显的规律性。 相似文献
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《资源与生态学报(英文版)》2020,(4)
黄山松是中国特有树种。为揭示黄山松天然林不同林龄径级结构与物种多样性特征,在麻城市黄山松天然次生林选择4个典型样地开展调查,研究黄山松径级结构与林分密度、群落物种多样性以及群落不同样地物种多样性相似性之间关系。结果表明:黄山松为群落优势种,在IV径级时,植株数量与全部植株比达到峰值,为19.46%;在VII径级时该比值出现第二次峰值,为18.92%;群落内维管植物156种,隶属于71科130属;林分平均密度最低时(1200 trees ha?1, DBH=36.779±4.444 cm),乔木层多样性(H'=1.6716)和均匀度(E=0.6727)最高;在林分平均密度最高时(1525 trees ha?1,DBH=18.957±5.141cm),灌木层丰富度(Dma=5.4308)、多样性(H'=2.9612)和均匀度最高(E=0.8985)。在林分密度为1325 trees ha?1时,草本的丰富度(Dma=5.8132)、多样性(H'=3.0697)和均匀度(E=0.9025)达到最大值。垂直结构上α多样性指数为:草本层灌木层乔木层;郁闭度增高会减弱群落林分内光照强度,造成黄山松群落内灌、草层物种多样性下降;样地间平均相似性系数为0.3356,处于中等不相似水平;干扰因子和不当管理可能是造成群落内不同样地存在较大的生境差异的主要原因。因此,必须制定科学的经营管理措施,优化黄山松林分结构,创造良好的群落环境,以提高物种多样性和稳定森林群落结构。 相似文献
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《山地学报》2018,(6)
为了解横断山区高山栎组[Quercus sect Heterobalanus(Oerst.) Menits.]灌木型植物不同器官碳(C)、氮(N)、磷(P)生态化学计量特征及分布格局,该文采用随机抽样方法布设18个高山栎组植物灌丛样地,采集高山栎组植物的根、茎、叶、枝器官样品,分析样品C、N、P含量。结果表明:(1)高山栎组植物C、N、P在各器官中分别表现为叶(477. 88 g·kg~(-1))枝(469. 29 g·kg~(-1))茎(445. 26 g·kg~(-1))根(431. 42 g·kg~(-1)),叶(13. 83 g·kg~(-1))茎(6. 08 g·kg~(-1))枝(5. 82 g·kg~(-1))根(4. 70 g·kg~(-1)),叶(1. 26 g·kg~(-1))枝(1. 21 g·kg~(-1))根(1. 16 g·kg~(-1))茎(0. 71 g·kg~(-1)),分配到叶中的营养元素相对较多;(2)各器官中C含量较N、P含量相对稳定,其中变异系数最大值发生在根部;(3)各器官C:N范围为36. 50～105. 33,最大值在根中,最小值在叶中,C:P范围为418. 15～768. 36,最大值在茎中,最小值在枝中,N:P范围为4. 89～11. 69,最大值在叶中,最小值在枝中;(4)各器官C与N、P间均呈负相关关系,N与P间均呈正相关关系,但相关关系是否显著在不同器官中不同;(5)各器官C、N、P含量受海拔的影响较小,仅叶片C含量、枝P含量与海拔间存在弱负相关关系。由此可见,高山栎组灌木型植物各器官营养元素的含量与其生长期及相应器官的功能结构密切相关。 相似文献
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太岳山森林群落物种多样性 总被引：14，自引：2，他引：14
根据 8个样地的调查资料 ,用丰富度指数、多样性指数和均匀度指数对山西太岳山 10个森林群落多样性进行研究 ,结果表明 :1)同一群落不同层次的物种多样性指数存在一定的波动范围 ;不同群落间 ,物种多样性指数也存在差异 ,这种差异与群落所处的演替阶段相关 ;当群落处于演替的顶级阶段时乔、灌、草 3个层次的物种多样性和均匀度指数多为乔木层 <灌木层 <草本层 ;演替先锋阶段和进展阶段多为乔木层 <灌木层 >草本层或乔木层>灌木层 <草本层。 2 )分布在不同海拔高度的森林群落的物种多样性呈连续性波动的变化 ,表现为随海拔高度的增加 ,物种多样性指数呈上升趋势。 3)群落物种多样性在空间上的差异不仅决定于物种丰富度指数 ,更与各物种间的均匀度指数密切相关 ;进而影响不同层次的物种多样性对群落总体物种多样性的贡献 相似文献
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《The Professional geographer》2013,65(3):306-317
This study investigates whether women's short commutes should be interpreted as constrained or convenient work trips by examining how race, gender, travel mode, occupation, residential location, workplace location, and Inc.ome affect commuting time. The analysis is restricted to a sample of European American and African American male and female workers residing in Buffalo, New York, and the surrounding county using data drawn from the Public Use Microdata Samples of the 1990 U.S. census. Given the pervasive gender wage gap, women unsurprisingly have more compromised (short commutes to low-Inc.ome jobs) work trips than do men. Multivariate analysis reveals that among those who reverse commute to suburban locations, African American women have the longest work trips. 相似文献
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Ibipo Johnston-Anumonwo 《The Professional geographer》1997,49(3):306-317
This study investigates whether women's short commutes should be interpreted as constrained or convenient work trips by examining how race, gender, travel mode, occupation, residential location, workplace location, and Inc.ome affect commuting time. The analysis is restricted to a sample of European American and African American male and female workers residing in Buffalo, New York, and the surrounding county using data drawn from the Public Use Microdata Samples of the 1990 U.S. census. Given the pervasive gender wage gap, women unsurprisingly have more compromised (short commutes to low-Inc.ome jobs) work trips than do men. Multivariate analysis reveals that among those who reverse commute to suburban locations, African American women have the longest work trips. 相似文献
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Ahmed M. El-Makky 《Natural Resources Research》2011,20(3):157-176
A prospective lithochemical survey (scale 1:50,000) was carried out at the Um Garayat gold mine area within the central wadi Allaqi shear zone. The metavolcanic samples were analyzed for Ti, P, Zr, Nb, Y, La, Nd, and Ce. The background and threshold values were determined using histograms, box-plots, and Q-mode cluster analysis. Discriminant analysis classifies the samples into four groups: Group 1 (Au mineralization) characterizes Phase III of the hydrothermal stage; Group 2 (Cu?CAu mineralization) characterizes Phases I and II; Groups 3 and 4 comprise the least altered samples. Cubic trend surface and residual maps display groups of elements: (P, Ti, Zr), (Nb, Y), and (La, Nd, Ce) each group has similar areal distribution pattern. R-mode factor analysis, using the cubic residuals, produces a model with three factors. Factors 1 (P, Ti, Zr) and 2 (Nb, Y) are referred to the magmatic minerals of the least altered volcanic rocks. In addition, Factor 1 associates with the Au-rich site at the shafts area, whereas Factor 2 is referred to albitization western to the shafts area with high contents of Nb and Y. In Factors 1 and 2, major P and Ti with traces Nb and Y are attributed to the accessories rutile, sphene, anatase, and calcite that were developed during propylitization as well as apatite and calcite-accompanying Phase I of the hydrothermal stage. Phosphorous could be considered as an indicator element for the Au mineralization at the study area. The principal elements of Factor 3 (La, Nd, Ce) associate with the Cu?CAu-rich site at the southern adits area, and attributed to the secondary Ca-bearing accessories calcite, sphene, and apatite. In general, these elements associate with the regional propylitization and the three phases of hydrothermal stage in zones of alkali metasomatism. In these alteration zones, La, Nd, and Ce could be used as indicators during geochemical exploration at the study area. In general, the secondary accessory minerals calcite, apatite, rutile, sphene, and anatase associating with zones of alkali metasomatism are significant carriers for the investigated elements. These accessories are possible indicators during geochemical exploration in the adjacent similar mineralizations of the central Allaqi shear zone area. 相似文献
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Spatial relationships among species, above-ground biomass, N, and P in degraded grasslands in Ordos Plateau, northwestern China 总被引：6，自引：0，他引：6
We chose five communities, representing a mild to severe gradient of grassland desertification in a semi-arid area of Ordos Plateau, northwestern China, to explore the spatial relationships among plant species, above-ground biomass (AGB), and plant nutrients (N and P). Community 1 (C1) was dominated by Stipa bungeana; Community 2 (C2) by a mix of S. bungeana and the shrub Artemisia ordosica; Community 3 (C3) by A. ordosica; Community 4 (C4) by a mix of Cynanchum komarovii and C. komorovii; and Community 5 (C5) by C. komorovii. Quantitative methods, including geostatistics, were used to compare community composition, structure, and indicators of ecosystem function (i.e. AGB, plant N and P) in five 16-m2 plots. The highest AGB, plant nitrogen (N) and plant phosphorus (P) were found in lightly degraded community C2. With increasing desertification effects from C3 to C5, the AGB, N, and P decreased significantly while plant density remained unchanged. The spatial variations of AGB were higher in shrub-dominated communities (C1 and C5) than in grass-dominated communities (C2–C4). Strong spatial relationships were detected within and among the communities, with stronger relationships between AGB and density than between AGB and species richness. Spatial patterns of plant N and P were different from those of AGB, reflecting different N and P contents of individual plants and different species that can redistribute soil resources in these communities. The AGB was positively correlated with soil nutrients (TOC, TN, TP, and IN), except for soil AP. We concluded that several specific aspects of ecosystem properties were directly associated with the conversion of the grass and shrub “functional types” in these degraded grasslands. 相似文献
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This study examines the experiences of geography graduates who work in business, government, and nonprofit organizations. We analyzed 352 logs from eighty-two professionals detailing professional activities, challenges, and opportunities during one work week each month, over a period of six months. Our analysis explores interpersonal relationships and working conditions affecting participants’ progress toward work goals, workplace climate, and professional identity. Geographic information systems and technology accounted for more than half of the geographic skills respondents reported using on the job, and administrative and leadership factors were the most commonly cited types of transferable skills. Professional geographers value collaborative workplaces as well as opportunities to work independently with the confidence of their supervisors, and their sense of a professional identity is enhanced when they feel valued and are recognized for their work. Professional development activities are important because they reinforce geographers’ sense of positively contributing to their organizations, enhance interpersonal interactions, facilitate work on specific projects, and expand individuals’ knowledge and skills. Moreover, our findings suggest that nearly half of the reported workplace difficulties could potentially be reduced or eliminated as a result of more and better professional development. Nonetheless, many employers do not consistently provide opportunities for professional development to their employees. Based on our analysis, we contend that professional development is a beneficial investment for lifelong learning, from undergraduate and graduate education throughout the entire course of a professional career. 相似文献
18.
Vehicle-related hyperthermia is an unfortunate tragedy that leads to the accidental deaths of children each year. This research utilizes the most extensive dataset of child vehicle-related hyperthermia deaths in the United States, including 414 deaths between 1998 and 2008. Deaths follow a seasonal pattern, with a peak in July and no deaths in December or January. Also, deaths occurred over a wide range of temperature and radiation levels and across virtually all regions, although most of them took place across the southern United States. In particular, the Phoenix, Houston, Dallas, and Las Vegas metropolitan areas had the greatest number of deaths. We utilize our vehicle hyperthermia index (vhi) to compare expected deaths versus actual deaths in a metropolitan area, based on the number of children in the area who are under the age of five and on the frequency of hot days in the area. The vhi indicates that the Memphis, West Palm Beach-Boca Raton, and Las Vegas metropolitan areas are the most dangerous places for vehicle-related hyperthermia. We conclude by discussing several recommendations with public health policy implications. 相似文献
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DIANA K DAVIS 《The Geographical journal》2006,172(2):88-105
Neoliberal restructuring in Morocco has been taking place for over twenty years. Beginning with a decade of structural adjustment, from the early 1980s to the early 1990s, parts of the public sector have been privatized, state services such as health care and education reduced, tariffs lowered and exports heavily promoted. In the dryland agricultural areas, a declensionist colonial environmental narrative has been appropriated to help justify and implement the neoliberal goals of land privatization and the intensification of agricultural production in the name of environmental protection. This paper contributes to areas of growing interest for geographers through an analysis of the underexplored relationship between neoliberalism and environmentalism, in the form of questionable environmental narratives, in Morocco. Land degradation in the dryland agricultural areas of Morocco is commonly blamed on overgrazing by local pastoralists despite existing documentation that suggests instead that ploughing of marginal lands and over-irrigation are the primary drivers of land degradation in the region. The deployment of this colonial environmental narrative of 'native improvidence' has facilitated an expansion of state power over collective rangelands under neoliberalism at the same time that government involvement has decreased in other sectors. The effects of neoliberalism in Morocco have been complex and thus the paper argues that current neoliberal reforms such as the Morocco–US free trade agreement need to be scrutinized carefully to prevent a further exacerbation of poverty as well as to prevent further land degradation in these areas. 相似文献