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1.
Soil crust lichens can be the dominant vegetation in arid lands, yet their importance as habitat to secondary producers is relatively unknown. This study examines the distribution of arthropod communities in the northern Namib Desert to evaluate whether a lichen-rich area is more or less productive than adjacent habitats in terms of the consumers each supports. Arthropods are diverse and highly endemic in the Namib Desert and lichens dominate this desert's extensive gravel plains. We sampled lichen-rich, dwarf shrub, and unvegetated sites and found distinct arthropod assemblages in the lichen-dominated sites, including species unique to lichen sites. Arthropod assemblages in two of the lichen sites were similar to those found in the dwarf shrub site. In a canonical correspondence analysis, crustose lichens and overall lichen cover were key in driving the variance in arthropod assemblages within the lichen sites. Furthermore, lichen morphotypes, overall lichen cover and species richness, were significantly correlated with the representation of arthropod subgroups and arthropod species richness. These findings provide evidence that lichen-dominated soil crusts in the Namib Desert are important supporters of secondary production, warranting more in-depth studies into the ecology and conservation of this lichen-rich habitat in warm deserts. 相似文献
2.
V. Rivera-Aguilar H. Godínez-Alvarez R. Moreno-Torres S. Rodríguez-Zaragoza 《Journal of Arid Environments》2009,73(11):1023-1028
The composition of cyanobacteria, mosses, and lichens of biological soil crusts were correlated with soil characteristics and sun exposure along an environmental transect. The study was conducted in Zapotitlán drylands, a locality within the Tehuacán–Cuicatlán Valley, central Mexico, where a great variety of environments for crust development exist due to landscape fragmentation. Data were analyzed with redundancy and Sorensen analysis. Soil crusts consisted of different combinations of cyanobacteria (7 species), mosses (19 species), and lichens (8 species). The relative frequencies of these groups were positively correlated with soil apparent density and lichens were also positively correlated with soil pH. However, there were no significant correlations with sun exposure. 相似文献
3.
The influence of elevation, shrub species, and biological soil crust on fertile islands in the Mojave Desert, USA 总被引：4，自引：1，他引：4
We quantified soil nutrients and biological crust cover (bryophytes and lichens) under the canopies of three species of Mojave Desert shrubs and in interspaces between shrubs at three elevations to determine the effects of shrub species, soil crust, and elevation on islands of soil fertility. Means of pH, organic matter, total Kjeldahl nitrogen, nitrogen mineralization, and gravimetric soil moisture are significantly greater in soils under Ambrosia dumosa (Gray) Payne, Larrea tridentata Cov., and Coleogyne ramosissima Torr. than soils from adjacent interspace microhabitats. Although soil moisture and soil organic matter increase by a factor of 1.5 from the low elevation to the high elevation site, the ratio of shrub to interspace concentrations, or the difference in mean soil variables between shrubs and interspaces, is effectively constant and independent of elevation. Total bryophyte and lichen cover is relatively low (24.5%), however, there are 11 species of bryophytes and two species of lichens distributed across three elevations with the highest species richness and cover at the low-elevation site. Bryophyte and lichen cover is correlated with silt but is not related, consistently, to soil nutrients. Overall, the balance of processes controlling spatial aggregation of soil nutrients under shrubs is remarkably insensitive to potential differences in organic inputs among elevations, shrub species, and soil crust surfaces. 相似文献
4.
The reliability of lichenometric dating is dependent on a good understanding of lichen growth rates. The growth rate of lichens can be determined from direct measurement of growing lichens or indirect methods by measuring lichens growing on surfaces of known age, although there are limitations to both approaches. Radiocarbon (14 C) analysis has previously been used in only a handful of studies to determine lichen growth rates of two species from a small area of North America. These studies have produced mixed results; a small amount of carbon turnover appears to occur in one of the species ( Caloplaca spp.) previously investigated introducing uncertainty in the growth rate, while much higher carbon cycling occurred in another ( Rhizocarpon geographicum ), making the 14 C approach unsuitable for estimating growth rates in the species most commonly used in lichenometric dating. We investigated the use of bomb-14 C analysis to determine the growth rate of a different crustose species ( Pertusaria pseudocorallina ) common to Northern Europe. 14 C-based growth rates were considerably higher than growth rates of morphologically similar species based on direct measurement made at locations nearby and elsewhere in the UK. This observation strongly suggests that a degree of carbon turnover probably occurs in Pertusaria pseudocorallina , and that bomb-14 C analysis alone cannot be used to determine lichen age or absolute growth rates in this lichen species. 相似文献
5.
《Polar Science》2014,8(4):397-412
We used observational and experimental analyses to investigate the photosynthetic activity and water relationships of five lichen species attached to different substrates in a glacier foreland in the High Arctic, Ny-Ålesund, Svalbard (79°N) during the snow-free season in 2009 and 2010. After the rains ceased, lichens and their attached substrates quickly dried, whereas photosynthetic activity in the lichens decreased gradually. The in situ photosynthetic activity was estimated based on the relative electron transportation rate (rETR) in four fruticose lichens: Cetrariella delisei, Flavocetraria nivalis, Cladonia arbuscula ssp. mitis, and Cladonia pleurota. The rETR approached zero around noon, although the crustose lichen Ochrolechia frigida grown on biological soil crust (BSC) could acquire water from the BSC and retain its WC to perform positive photosynthesis. The light-rETR relationship curves of the five well-watered lichens were characterized into two types: shade-adapted with photoinhibition for the fruticose lichens, and light-adapted with no photoinhibition for O. frigida. The maximum rETR was expected to occur when they could acquire water from the surrounding air or from substrates during the desiccation period. Our results suggest that different species of Arctic lichens have different water availabilities due to their substrates and/or morphological characteristics, which affect their photosynthetic active periods during the summer. 相似文献
6.
7.
Saxicolous species of lichens are able to induce and accelerate weathering of their rock substrate, and effects of lichens
on substrate can be attributed to both physical and chemical causes. This paper is focused on biotic weathering actions of
epilithic and endolithic species on the different rock types (sandstones and volcanogenic rocks) in Antarctica. The patterns,
mechanisms, processes and neoformations of rock-weathering resulting from lichen colonization are expounded in detail. Furthermore,
it is pointed out that, for a better understanding of the impacts of lichens on environments, the studies on the rate of biotic
weathering and the comprehensive involvement of the lichen effects on weathering of natural rocks remain to be carried out
in Antarctica. 相似文献
8.
Saxicolous species of lichens are able to induce and accelerate weathering of their rock substrate, and effects of lichens on substrate can be attributed to both physical and chemical causes. This paper is focused on biotic weathering actions of epilithic and endolithic species on the different rock types (sandstones and volcanogenic rocks) in Antarctica. The patterns, mechanisms, processes and neoformations of rock-weathering resulting from lichen colonization are expounded in detail. Furthermore, it is pointed out that, for a better understanding of the impacts of lichens on environments, the studies on the rate of biotic weathering and the comprehensive involvement of the lichen effects on weathering of natural rocks remain to be carried out in Antarctica. 相似文献
9.
对采集自南极乔治王岛和北极新奥尔松地区的32份地衣标本中共生藻rDNA ITS序列进行测定,发现均为Trebouxia jamesii;结合Genbank中来自不同地区地衣中该藻的序列信息,发现T. jamesii的基因型与地衣物种及采集地都没有明确的对应关系。广布于全球范围的T. jamesii作为地衣优势共生藻,存在多种基因型,并且可以被多种地衣共生菌选择;其中优势基因型A在采集自南极洲、欧洲、北美洲和北极地区的地衣中均有发现,而其它基因型则在一定程度上出现地区特有性。本研究为地衣中的藻交换提供了证据,并提出地衣体碎片是实现地衣共生藻长距离传播的载体。 相似文献
10.
William B. Bull 《Geografiska Annaler: Series A, Physical Geography》2014,96(2):117-133
Botanists make yearly measurements of lichen sizes that describe highly variable radial expansion of young, and old, Rhizocarpon subgenus Rhizocarpon that is a function of thallus size and age. Such non‐uniform growth would negate use of lichens to date geomorphic events, such as landslides and moraines, of the past 1000 years. Fortunately, many crustose lichens tend toward circular shapes, which can be achieved only when overall uniform radial growth prevails. Largest lichen measurements on rockfall blocks that accumulate incrementally as hillslope talus in earthquake‐prone California plot as distinct peaks in frequency distributions. Rockfall surface‐exposure times are known to the day for historical earthquakes and to the year where mass movements damage trees. Lichenometry consistently dates regionally synchronous rockfall events with an accuracy and precision of ±5 years. Only historical records and tree‐ring dating of earthquakes are better. The four crustose lichens used here have constant long‐term growth rates, ranging from 9.5 to 23.1 mm per century. Growth rates do not vary with altitude or climate in a 900 km long mountainous study region in California, USA. Linear growth regressions, when projected to the present, constrain estimates of colonization time and possible styles of initial lichen growth. 相似文献
11.
BY RICHARD A. ARMSTRONG TOM BRADWELL 《Geografiska Annaler: Series A, Physical Geography》2010,92(1):141-147
Certain species of crustose lichens have concentrically zoned margins which probably represent yearly growth rings. These marginal growth rings offer an alternative method of studying annual growth fluctuations, establishing growth rate–size curves, and determining the age of thalli for certain crustose species. Hence, marginal growth rings represent a potentially valuable, unexploited, tool in lichenometry. In a preliminary study, we measured the widths of the successive marginal rings in 25 thalli of Ochrolechia parella (L.) Massal., growing at a maritime site in north Wales. Mean ring widths of all thalli varied from a minimum of 1.02 mm (the outermost ring) to a maximum of 2.06 mm (the third ring from the margin). There is some suggestion that marginal ring width and thallus size are positively correlated; and hence that growth rates increase in larger thalli in this small population. In a further study on recently exposed bedrock adjacent to Breiðarlon, SE Iceland, we examined the potential for using marginal growth rings to estimate thallus age of a lichen tentatively identified as a Rhizocarpon (possibly R. concentricum (Davies) Beltram.) and thus confirm the timing of surface exposure ( c. 50 years). Collectively, these results suggest: 1) the measurement of marginal rings is a possible alternative method of studying the growth of crustose lichens; 2) O. parella may grow differently to other crustose species, exhibiting a rapidly increasing radial growth rate in thalli >40 mm; 3) where lichens with marginal rings grow on recently exposed surfaces (<60 yrs), minimum age estimates can be made using growth rings as an in situ indication of lichen growth rate; 4) it is suggested that this phenomenon could provide a valuable, previously unexploited, in situ lichenometric-dating tool in areas lacking calibration control. 相似文献
12.
This paper presents a critical review of previous lichenometric and lichen growth studies in southern parts of West and East Greenland. These studies include classic work from around Søndre Strømfjord, Sukkertoppen, Sermilik and Angmagssalik. Particular emphasis is placed on those studies examining the role played by climatic continentality on the growth rate of crustose lichens in Greenland. The latter part of the paper presents new data on lichen growth rates from Sermilik, between 2001 and 2006, in 22 different lichen species. Measurements show that different species grow at different rates and growth rates vary from site to site. In this study Rhizocarpon geographicum generally grows slowly (<0.2 mm a−1 ) while other species such as Pseudephebe minuscula grow more rapidly (1.0 mm a−1 ) in the same environment. Comparison with other studies shows that taxa-specific growth rates are slightly greater in West than in East Greenland – probably as a result of the slightly more favourable climate and higher precipitation levels. It is suggested that recent climate change, most marked in southern Greenland, will probably result in changed growth curves (over time) for species such as Rhizocarpon geographicum . However, only more precise growth curves and lichenometric dating curves can demonstrate such a phenomenon. 相似文献
13.
The interception and evaporation of fog, dew and water vapour by soils and lichens in a coastal desert were measured with automated lysimeters at hourly intervals spanning a 12 month period. Fog water and lichen thalli were chemically analysed at monthly intervals. The chemical composition of the lichens did not correspond with the elemental concentration sequence in collected fog water of oceanic origin. However, elemental concentrations were generally greater in Teloschistes capensis, whose canopy area to dry mass ratio was higher than that of Ramalina sp., indicative of a more efficient mineral absorbing thinner thallus. Non-rainfall atmospheric moisture intercepted by the bare gypsum soil was 10 times greater and that solely by the lichens up to 3 times greater than the measured rainfall amount. Water vapour contributed the highest percentage of the non-rainfall atmospheric moisture absorbed by the lichens and bare soil, followed by fog, with dew contributing the smallest percentage. T. capensis displayed two-fold greater interception and two-thirds less evaporation of non-rainfall atmospheric moisture than Ramalina sp. which may explain T. capensis 3 times greater canopy cover. Our results substantiate the crucial role of atmospheric water vapour and fog in driving lichen photosynthesis and distribution in a coastal desert. 相似文献
14.
Crustaceous lichens sensitive monitor of caesium-137 radiation level in terrestrial environment 
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下载免费PDF全文 <正> The activity of caesium-137(Bq/kg)in the crustaceous lichens and othersamples was determined to prove the feasibility that crustaceous lichens work as a sen-sitive biology monitor to record the caesium-137(Bq/kg)radiation levels of terrestri-al environment.The measurements were performed with GEM series HPGe(high-pu-rity Germanium)coaxial detector system(ADCAM-100)made by EC & GORTECCompany in USA.It was found that the activity of caesium-137(Bq/kg)in the cru-staceous lichens was one order of magnitude higher than that found in surface soil,and was over three orders of magnitude higher than those found in the familiar biologi-cal samples.These results proved that crustaceous lichens may be one of the mostsensitive biolog-ical monitors about the remote transmission and environmental radia-tion levels of caesium-137. 相似文献
15.
Michael G. Loso Daniel F. Doak Robert S. Anderson 《Geografiska Annaler: Series A, Physical Geography》2014,96(1):21-41
Contemporary variants of the lichenometric dating technique depend upon statistical correlations between surface age and maximum lichen sizes, rather than an understanding of lichen biology. To date three terminal moraines of an Alaskan glacier, we used a new lichenometric technique in which surfaces are dated by comparing lichen population distributions with the predictions of ecological demography models with explicit rules for the biological processes that govern lichen populations: colonization, growth, and survival. These rules were inferred from size–frequency distributions of lichens on calibration surfaces, but could be taken directly from biological studies. Working with two lichen taxa, we used multinomial‐based likelihood functions to compare model predictions with measured lichen populations, using only the thalli in the largest 25% of the size distribution. Joint likelihoods that combine the results of both species estimated moraine ages of ad 1938, 1917, and 1816. Ages predicted by Rhizocarpon alone were older than those of P. pubescens. Predicted ages are geologically plausible, and reveal glacier terminus retreat after a Little Ice Age maximum advance around ad 1816, with accelerated retreat starting in the early to mid twentieth century. Importantly, our technique permits calculation of prediction and model uncertainty. We attribute large confidence intervals for some dates to the use of the biologically variable Rhizocarpon subgenus, small sample sizes, and high inferred lichen mortality. We also suggest the need for improvement in demographic models. A primary advantage of our technique is that a process‐based approach to lichenometry will allow direct incorporation of ongoing advances in lichen biology. 相似文献
16.
山东湿地植被类型和演替规律的研究 总被引：2，自引：1，他引：1
山东湿地共分布有湿地高等维管植物70科277种、苔藓植物12科24种,在植物种类组成上以莎草科和禾本科植物等最为丰富。植被类型有灌丛、灌草丛、草甸、盐生、沙生、沼生和水生植被等7种。湿地植被的分布既受地理位置、气候、海拔等影响,又受制于水分、土壤和土壤含盐量等因素。湿地演替是植物群落的演替过程,即随着湿地的发育,特别是土壤水分和营养的变化,导致植物种类和群落发生改变的过程。湿地植物群落演替是气候、水文以及地貌、土壤等自然要素综合作用的结果,客观反映了湿地的形成、发育与演替过程。 相似文献
17.
《自然地理学》2013,34(2):183-192
Rock outcrops along ridgelines, in block fields, and on cliff faces of Shenandoah National Park (SNP) provide unique habitats for numerous rare and endemic biotas. However, there are recent concerns about the long-term sustainability of these populations because of increased park usage (e.g., hiking, rock climbing) and environmental change (e.g., air chemistry, quality). Analysis of lichen-population dynamics provides insight into the rate at which these habitats are being degraded. As such, there is a need to develop a method to rapidly and accurately assess changes in lichen communities through space and over time. This study presents a new approach designed to record lichen species on rock outcrops. Terrestrial laser scanning (TLS) offers a new technique for recording individual lichen species (e.g., abundance, spatial distribution, extent, size, shape). An automated process is described to extract the lichen extent and shape in a standard GIS environment. These data are used to examine size classes, frequency, percent cover, and spatial pattern of a species of Phlyctis. The methodology and data extracted greatly improve rapid assessments and long-term monitoring of lichen populations. 相似文献
18.
Distribution and floristics of desert plant communities in the lower reaches of Tarim River, southern Xinjiang, People's Republic of China 总被引：6，自引：0，他引：6
The distribution and abundance of desert plant communities were examined in the lower reaches of the Tarim River, southern Xinjiang. Eighteen plant species were collected at 18 sites along a sequence of increasing ground-water depths in six transects. Except for Tamarix ramosissima and Populus euphratica, which were distributed across nearly all sites, most of the investigated species had low frequency of occurrence. Correspondence analysis (CA) of the 18 species revealed a separation of growth forms into distinct groups corresponding to different ground-water levels. Three clearly defined groups of growth forms were strongly associated with three distinct ground-water zones, ranging from <3, 3–5 and >5 m, respectively. Four taxa groups were found to correspond to the three ground-water zones and to several other environmental factors. Canonical correspondence analysis (CCA) of the 18 species and seven environmental variables would suggest a major botanical gradient exists relating to ground-water depth and secondary gradients exists that include soil moisture, pH and to a lesser extent alkalinity and mineralization. 相似文献
19.
腾格里沙漠东南缘生物土壤结皮对土壤理化性质的影响 总被引：3，自引：1，他引：2
生物土壤结皮是荒漠生态系统地表景观的重要组成部分,在沙化土地恢复和流沙固定中起着重要作用。研究了腾格里沙漠东南缘固沙植被区不同类型生物土壤结皮理化性质及结皮发育对下层土壤性质的影响。结果表明：结皮层厚度、孔隙度、黏粉粒和田间持水量以及有机碳、无机碳、全氮、碱解氮、速效磷、速效钾含量和电导率均表现为藓类结皮 > 混生结皮 > 地衣结皮 > 藻类结皮;砂粒含量和容重表现为藻类结皮 > 地衣结皮> 混生结皮 > 藓类结皮。结皮下0~2 cm和2~5 cm土层理化性质表现出与结皮层相同的变化规律。总体上,生物土壤结皮对下层土壤理化性质的影响表现为藓类结皮和混生结皮大于地衣结皮和藻类结皮;而结皮对下层土壤理化性质的影响随土壤深度的增加而减小。生物土壤结皮的拓殖和发育是荒漠生态系统成土过程和土壤质量的关键影响因素。 相似文献
20.
生物土壤结皮对荒漠昆虫多样性的影响 总被引：10，自引：6，他引：4
生物土壤结皮广泛分布在干旱半干旱地区与寒区荒漠,是荒漠生态系统的主要组成和景观特征之一,其重要性已被大量的研究报道所证实。然而,关于生物土壤结皮与昆虫种类多样性之间关系的研究却很少。本文以腾格里沙漠东南缘的沙坡头地区半固定沙丘柠条－油蒿群落和固定沙丘柠条－油蒿群落为观测样地,选择具有不同类型生物土壤结皮分布的植被群落为观测样方。昆虫的调查采用100 m×100 m的样方,利用样筐和网捕法收集昆虫,记录昆虫数量,采集标本在室内进行鉴定。结果表明:与无结皮覆盖的植被区相比,生物土壤结皮在地表的覆盖显著地增加了昆虫的多样性和种的丰富度,其中以苔藓和地衣为主的结皮覆盖的植被样方中昆虫种的多样性和丰富度显著地高于以蓝藻和藻类为主的结皮样方。生物土壤结皮对荒漠昆虫多样性的贡献可能是由于稳定了土表、改善了植被系统中的土壤环境,为昆虫,特别是幼虫阶段提供相对适宜的土壤生境或部分食物来源。 相似文献