共查询到20条相似文献,搜索用时 15 毫秒
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《Lichenologist (London, England)》2002,34(5):415-427
Epiphytic lichen diversity in a boggy stand of Norway spruce (Picea abies) was studied in the eastern Harz Mountains, northern Germany. Spruce trees at wet sites were affected by forest dieback, whereas trees on drier sites remained unaffected. Lichen diversity was higher on dieback-affected trees than on healthy ones. The foliose lichen Hypogymnia physodes was significantly more frequent on dead trees, whereas the crustose, extremely toxitolerant Lecanora conizaeoides occurred more frequently on healthy trees. Stemflow concentrations of NH4+, NO3−, PO3−, and SO42− were lower on affected trees. This is attributed to reduced interception from the atmosphere due to needle loss. Cover of H. physodes decreased with increasing mean SO42− concentration in stemflow. The total of lichen species per sample tree also decreased with increasing SO42− concentration in stemflow, indicating that most species reacted in a similar way as H. physodes. Cover of L. conizaeoides increased with increasing SO42− concentration, but decreased at higher SO42− concentrations. Bark chemistry had a minor influence on lichen diversity. 相似文献
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Marc Srour Germano Leão Demolin Leite Torsten Wappler Teja Tscharntke Christoph Scherber 《Insect Science》2012,19(6):705-705
Retraction: The following article from Insect Science, ‘Diversity of ants across an altitudinal gradient in and outside a spruce forest in the Harz Mountains, Germany’ by Marc Srour, Germano Leão Demolin Leite, Torsten Wappler, Teja Tscharntke and Christoph Scherber, published online on 2 August 2012 in Wiley Online Library ( http://wileyonlinelibrary.com ), has been retracted by agreement between the authors, the journal Editor in Chief, Le Kang, and Wiley Publishing Asia Pty Ltd. The retraction has been agreed due to concerns having been raised about the validity of the species richness values derived by the authors, and regarding the validity of the species determinations. 相似文献
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Markus Hauck Uwe de Bruyn Samjaa Javkhlan Dorjburgedaa Lkhagvadorj 《Journal of Plant Ecology》2014,7(3):287
Aims The effects of traditional land use by mobile livestock keepers on biodiversity in forest steppe ecotones are insufficiently studied. Epiphytes are an important part of forest plant diversity. Here we analyze differences in the diversity and composition of the epiphytic lichen vegetation between the edge and the interior of Siberian larch forests in the Khangai Mountains, western Mongolia, which are highly subdivided into patches. We asked whether the epiphytic lichen vegetation at the forest edge differs significantly from that in the interior, whether the edge is inhabited by more nitrophilous species than the interior and whether the density of nomad camps around the forest affects epiphytic lichen diversity.Methods Cover percentages of epiphytic lichen species were recorded from 20 trees per plot on 6 plots in the interior and 6 plots at the edge of Larix sibirica forests. The position of nomad summer camps was surveyed using Global Positioning System. Data were analyzed with pairwise significance tests, analysis of similarities, nonmetric multidimensional scaling and canonical correspondence analysis.Important findings The composition of the epiphytic lichen vegetation clearly differed between the two habitats, with more species being more frequent at the edge than in the interior. However, there was no difference in species richness (α-diversity). The epiphyte vegetation at the edge was more uniform and characterized by lower variation of tree-level α-diversity and lower β-diversity than in the interior. At the edge, only nitrophytic lichens were dominant, whereas in the interior, nitrophytes and acidophytes were among the dominant species. This pattern is probably attributable to the spatial heterogeneity of the intensity of forest grazing and was shown to be influenced by the density of nomad summer camps in the vicinity of the forests. Tree-level α-diversity increased with stem diameter, but high-diameter trees were rare. The results suggest that the present level of forest patchiness and the effect of forest grazing increases the diversity of epiphytic lichens on the landscape level, while logging of high-diameter trees reduces lichen diversity. 相似文献
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The relevance of chemical site factors for the abundance of epiphytic lichens was studied in Picea engelmannii-Abies lasiocarpa forests of the Salish Mountains, northwestern Montana, USA. The Salish Mountains are an area with relatively low atmospheric pollutant load and low precipitation. Canonical correspondence analysis (CCA) suggests that cover of several lichen species was limited by high Mn concentrations of bark or by high ratios of Mn to Ca, Mg and Fe. Mn in the bark is known primarily to derive from the soil. An effect of Mn concentration or Mn/Ca and Mn/Mg ratios was not found on A. lasiocarpa. This suggests that A. lasiocarpa deposits Mn in the bark in a physiologically inactive form as already known from A. balsamea. Precipitation chemistry was apparently less relevant for epiphytic lichen distribution in the Salish Mountains, as no correlations between element concentrations in stemflow and cover values were found and as amounts of stemflow were small. However, precipitation in the study year was less than average. The lacking significance of precipitation chemistry is probably the cause why epiphytic lichen vegetation differed less between living and dead trees in the Salish Mountains than in highly polluted coniferous forests studied by our group in Germany; in Germany, the difference between living and dead trees was attributed to reduced interception of pollutants from the atmosphere by trees with reduced crown surface. The result of the present study that small-scale variation of epiphytic lichen abundance is only partly explainable by chemical parameters gives rise to the assumption that microclimate (e.g., moisture), which has not been systematically explored, could be an important site factor for epiphytic lichens in the Salish Mountains. Furthermore, tree age was identified by CCA as a relevant site factor for lichens on P. engelmannii. 相似文献
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The impacts of increasing drought on forest dynamics,structure, and biodiversity in the United States 总被引:1,自引:0,他引:1 下载免费PDF全文
James S. Clark Louis Iverson Christopher W. Woodall Craig D. Allen David M. Bell Don C. Bragg Anthony W. D'Amato Frank W. Davis Michelle H. Hersh Ines Ibanez Stephen T. Jackson Stephen Matthews Neil Pederson Matthew Peters Mark W. Schwartz Kristen M. Waring Niklaus E. Zimmermann 《Global Change Biology》2016,22(7):2329-2352
We synthesize insights from current understanding of drought impacts at stand‐to‐biogeographic scales, including management options, and we identify challenges to be addressed with new research. Large stand‐level shifts underway in western forests already are showing the importance of interactions involving drought, insects, and fire. Diebacks, changes in composition and structure, and shifting range limits are widely observed. In the eastern US, the effects of increasing drought are becoming better understood at the level of individual trees, but this knowledge cannot yet be confidently translated to predictions of changing structure and diversity of forest stands. While eastern forests have not experienced the types of changes seen in western forests in recent decades, they too are vulnerable to drought and could experience significant changes with increased severity, frequency, or duration in drought. Throughout the continental United States, the combination of projected large climate‐induced shifts in suitable habitat from modeling studies and limited potential for the rapid migration of tree populations suggests that changing tree and forest biogeography could substantially lag habitat shifts already underway. Forest management practices can partially ameliorate drought impacts through reductions in stand density, selection of drought‐tolerant species and genotypes, artificial regeneration, and the development of multistructured stands. However, silvicultural treatments also could exacerbate drought impacts unless implemented with careful attention to site and stand characteristics. Gaps in our understanding should motivate new research on the effects of interactions involving climate and other species at the stand scale and how interactions and multiple responses are represented in models. This assessment indicates that, without a stronger empirical basis for drought impacts at the stand scale, more complex models may provide limited guidance. 相似文献
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Y. K. Soon 《Plant and Soil》1994,160(1):157-160
Temporal changes in labile soil Cu, Mn and Zn were measured for up to 23 years after conversion of a boreal forest to the following crop production systems: (i) continuous barley, (ii) continuous legume and (iii) continuous bromegrass for hay, and (iv) barley/legume-bromegrass hay rotation. Decreases in labile Mn and Zn were greater than can be accounted for by crop offtake except for the continuous grass treatment. Some Mn and Zn was probably converted to less labile forms due mostly to reduction in soil organic matter associated with soil cultivation and some cropping systems. Labile copper was increased slightly with time under agriculture. 相似文献
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Correlation between water relations and within-canopy distribution of epiphytic ferns in a Mexican cloud forest 总被引:4,自引:0,他引:4
The physiological traits associated with water relations of eight common epiphytic ferns in a Mexican cloud forest were investigated
in relation to the distribution of these species within the canopy. Fern distribution was significantly correlated with the
relative water content at which stomata close, leaf thickness, stomatal density and size. Trichomanes bucinatum desiccated completely within hours in moderately dry air and was confined to the stem bases, and Asplenium cuspidatum, with no evident adaptations to cope with drought, grew in the second most shaded zone within the tree crowns. Despite growing
in a humid cloud forest, all other species had xeric adaptations including coriaceous leaves (Pleopeltis mexicana, Elaphoglossum glaucum), succulent rhizomes (Polypodium puberulum, Phlebodium areolatum), low rates of uncontrolled water loss (all species except P. puberulum), leaf scales (Elaphoglossum petiolatum, Polypodium plebeium), and high cell wall elasticity (all species). P. plebeium and Pl. mexicanum, which grow in the most exposed locations, tolerated water loss beyond the turgor loss point before the stomata closed and
appear to be poikilohydric or at least to tolerate high water deficits.
Received: 8 June 1997 / Accepted: 30 November 1997 相似文献
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Ladislav Holko Jaroslav Škvarenina Zdeněk Kostka Michal Frič Juraj Staroň 《Biologia》2009,64(3):594-599
The paper analyzes the impacts of the spruce forest on precipitation interception and evolution of snow cover in the mountain
catchment of the Jalovecky creek, the Western Tatra Mountains, Slovakia. Both processes were monitored at the elevation of
1420 m a.s.l.. Interception was measured from the end of August 2006 until November 2008 by a network of 13 raingauges. Mean
interception over the studied period in forest window was 23%. Mean values for the dripping zone under tree branches, near
stems of the trees and under the young trees were 28%, 65% and 44%, respectively. With exception of forest window, the interception
at the same characteristic positions was highly variable. Calculated daily precipitation thresholds needed to fulfill the
storage capacity of the canopy were about 0.8–0.9 mm.
Differences in snow accumulation and melt in the open area (elevation 1500 m a.s.l.) and in the forest were measured in winters
2003–2008. Snow depths (SD) and water equivalents (SWE) were typically smaller in the forest, although the differences were
getting smaller towards the end of snow season. SD and SWE in the forest were higher than in the open area for a short time
before the end of season in winters 2003 and 2005. The correlations between SD and SWE in the open area and in the forest
explained about 90% of variability. The energy balance snow model UEB satisfactorily simulated the evolution of snow cover
in the forest and in the open area. 相似文献
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祁连山区青海云杉林蒸腾耗水估算 总被引:2,自引:0,他引:2
青海云杉(Picea crassifolia)林在祁连山区水量平衡中起着重要的调节作用,合理并准确地估算其冠层蒸腾量,对于了解该区的水分循环和水分平衡具有重大意义。以位于祁连山中段大野口关滩森林站的青海云杉纯林为研究对象,结合研究区微气象梯度观测塔自动记录的常规气象资料(气温、空气相对湿度、风速等)以及太阳辐射、大气中CO2 浓度、土壤热通量等,应用改进的Penman-Monteith修正式对研究区青海云杉林2008年生长季的冠层蒸腾量进行估算,并采用单变量敏感性分析法对模拟结果进行分析。结果表明:青海云杉林2008年生长季(5-9月)的总蒸腾量为148.8 mm,平均日蒸腾量为0.97 mm;冠层蒸腾量主要受太阳辐射的影响,使得日蒸腾量在典型晴天高达2.19 mm,而在阴雨天仅为0.016 mm;气温对冠层蒸腾量的作用也十分重要,随气温的变化,日蒸腾量从5月开始逐渐增大,在7月中上旬达最大值,从7月下旬到生长季结束其值逐渐减小;模型输入参数对模拟蒸腾量的影响强弱顺序为:林冠层截获的净辐射>叶面积指数>气温>风速>大气相对湿度;当模型输入参数在±10%变动时,模拟结果的变化范围均在±10%以内,说明该模型的模拟结果比较稳定。在积累了大量相关基础数据的条件下,通过该改进的Penman-Monteith修正式估算森林蒸腾耗水量仍是一种获得满意结果的便捷方法。 相似文献
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Based on data from three German forest ecosystems severely disturbed by windthrow events, correlation patterns between NO3
− and SO4
2− dynamics in the soil solution are described. Each of the correlation types was related to site-specific SO4
2− retention processes. The relative importance of SO4
2− adsorption/desorption and precipitation/dissolution was found to be different for the studied soils depending on their contents
of SO4
2− -adsorbing sesquioxides and of A1 hydroxy sulfate minerals. Enhanced NO3
− concentrations in the soil solution resulting from excess nitrification promoted either SO4
2− adsorption or the dissolution of Al hydroxy sulfates. Both processes result in different ecological consequences: Whereas
the former reaction reduces anion concentration peaks in the soil solution, the latter increases them. Thus, a prediction
of cation export from soil ecosystems subjected to excess nitrification has to regard site-specific interrelationships between
NO3
− and SO4
2−. As a third type of conelation the independence of NO3
− and SO4
2− concentrations in the soil solution is presented. This type is suggested to be typical for soils with low SO4
2−. adsorption capacity and absence of A1 hydroxy sulfates. 相似文献
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William Newmark 《African Journal of Ecology》2005,43(3):177-180
The difference in air temperature between the forest edge and interior was simultaneously compared at ten sites at 2‐h intervals over a 229‐day period in the East and West Usambara Mountains in Tanzania. Measurements were recorded with data loggers placed 1.5 m above the ground on the shaded side of trees and positioned 1–2 and 100 m from the forest edge. The difference in air temperature between the forest edge and interior varied regularly over a 24‐h period with mean maximum difference in air temperatures of 0.85°C occurring at 15:00 h and mean minimum diel difference in air temperature of 0.02°C occurring at 21:00 h. Diel variation in the difference in air temperature between the forest edge and interior varied little by season and was unrelated to elevation. 相似文献
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Paulo M. Brando Daniel C. Nepstad Jennifer K. Balch Benjamin Bolker Mary C. Christman Michael Coe Francis E. Putz 《Global Change Biology》2012,18(2):630-641
Large‐scale wildfires are expected to accelerate forest dieback in Amazônia, but the fire vulnerability of tree species remains uncertain, in part due to the lack of studies relating fire‐induced mortality to both fire behavior and plant traits. To address this gap, we established two sets of experiments in southern Amazonia. First, we tested which bark traits best predict heat transfer rates (R) through bark during experimental bole heating. Second, using data from a large‐scale fire experiment, we tested the effects of tree wood density (WD), size, and estimated R (inverse of cambium insulation) on tree mortality after one to five fires. In the first experiment, bark thickness explained 82% of the variance in R, while the presence of water in the bark reduced the difference in temperature between the heat source and the vascular cambium, perhaps because of high latent heat of vaporization. This novel finding provides an important insight for improving mechanistic models of fire‐induced cambium damage from tropical to temperate regions. In the second experiment, tree mortality increased with increasing fire intensity (i.e. as indicated by bark char height on tree boles), which was higher along the forest edge, during the 2007 drought, and when the fire return interval was 3 years instead of one. Contrary to other tropical studies, the relationship between mortality and fire intensity was strongest in the year following the fires, but continued for 3 years afterwards. Tree mortality was low (≤20%) for thick‐barked individuals (≥18 mm) subjected to medium‐intensity fires, and significantly decreased as a function of increasing tree diameter, height and wood density. Hence, fire‐induced tree mortality was influenced not only by cambium insulation but also by other traits that reduce the indirect effects of fire. These results can be used to improve assessments of fire vulnerability of tropical forests. 相似文献
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苔藓和凋落物对祁连山青海云杉林土壤呼吸的影响 总被引:2,自引:0,他引:2
于2012—2014年生长季在青海云杉林下开展了地表覆盖物(苔藓和凋落物)对林下土壤呼吸速率影响的研究。采用LI8100土壤碳通量自动测量系统对苔藓覆盖、凋落物覆盖和裸土(去除地表覆盖物)的土壤呼吸进行观测,对比分析林下3种覆盖处理下的土壤呼吸差异。结果表明:苔藓覆盖土壤、凋落物覆盖土壤和裸土土壤的呼吸速率年均值分别为(3.88±0.26)μmol m~(-2)s~(-1),(3.31±0.19)μmol m~(-2)s~(-1),(2.28±0.31)μmol m~(-2)s~(-1),三者之间具有极显著差异,3组处理的地表相对湿度、土壤含水量、土壤温度和地表温度间均没有显著差异,但苔藓组和凋落物组的土壤温度分别比裸土组高8.13%和10.24%;3组处理的土壤呼吸速率均与温度呈显著指数相关性(0.53≤R~2≤0.91),且与土壤温度的相关性更高;苔藓覆盖、凋落物覆盖土壤呼吸的温度敏感性(Q_(10))分别为5.47,3.67,均高于裸土土壤呼吸的Q_(10)(2.23);裸土土壤呼吸与土壤含水量(VWC)呈高斯函数关系,VWC=34%是临界值,苔藓覆盖、凋落物覆盖土壤的呼吸速率与土壤含水量均呈线性负相关关系;苔藓和凋落物对裸土土壤呼吸的月均贡献率分别为29.33%和24.06%,可见,苔藓和凋落物在青海云杉林生态系统呼吸中起重要作用。 相似文献
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Light microhabitats,growth and photosynthesis of an epiphytic bromeliad in a tropical dry forest 总被引:1,自引:0,他引:1
In the tropical dry forest of Dzibilchaltún, Yucatan, Mexico, light microhabitats, tissue acidity changes, chlorophyll fluorescence and growth were investigated for the epiphytic bromeliad Tillandsia brachycaulos Schltdl. Most individuals occurred in sites between 20 and 60% of the height of the tree, and directly on the main trunk or branches closed to the main trunk. During the dry season, individuals received about nine times more photon flux density (PFD) than during the rainy season. Individuals that occurred under 30–59% of the daily ambient PFD showed greater leaf length increase and monthly leaf production, and produced more flowers than individuals in the brighter (>60% of ambient PFD) and the darker (11–29% of ambient PFD) light microhabitats. Well-watered plants acclimated to deep shade (6% of ambient PFD) showed values of tissue acidity similar to plants under higher light treatments. Well-watered plants under 60% of daily ambient PFD showed low values of maximum quantum efficiency at midday during most of the year but showed similar values of tissue acidity than plants under 6 and 30% of ambient PFD. Leaf temperatures of plants in low sites within the canopy and on the forest floor were significantly higher than the air during about 1 h, indicating that those plants could not dissipate the excess of heat. Individuals located in the most shaded microhabitats could also receive less amount of water from rainfall and dew. Therefore, it would be less damaging for this epiphytic bromeliad to occur in the most exposed microhabitats than in the most shaded microhabitats in this tropical dry forest. 相似文献
18.
长白山阔叶红松林物种多度和空间分布格局的关系 总被引:4,自引:0,他引:4
应用随机分布多度模型和聚集分布多度模型,探讨不同研究尺度下物种多度和空间分布格局的关系.结果表明,预测的物种多度不仅受物种分布面积大小的影响,还受其聚集程度的影响.物种多度和空间分布格局的关系存在着明显的尺度效应,即随着研究尺度的增加,无论是随机分布多度模型还是聚集分布多度模型,通过物种空间分布格局来预测物种多度的准确度都在下降.聚集分布多度模型预测物种多度的结果要好于随机分布多度模型,这表明该区大多数物种是聚集分布的.由于物种的空间分布格局不同,不同物种多度的预测值和真实值之间的差异也不同.因此,为了进一步提高模型预测的准确性,进一步考虑不同物种的生活史特性是必要的. 相似文献
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Joel D. Blum E. Hank Taliaferro Marie T. Weisse Richard T. Holmes 《Biogeochemistry》2000,49(1):87-101
The variability and biologicalfractionation of Sr/Ca, Ba/Ca and 87Sr/86Srratios were studied in a soil–plant–invertebrate–bird food chain in two forested ecosystems withcontrasting calcium availability in the northeasternU.S.A. Chemical measurements were made of the soilexchange pool, leaves, caterpillars, snails, and boththe femurs and eggshells of breeding insectivorousmigratory songbirds. 87Sr/86Sr values weretransferred up the food chain from the soil exchangepool to leaves, caterpillars, snails and eggshellswithout modification. Adult birds were the oneexception; their 87Sr/86Sr values generallyreflected those of lower trophic levels at each site,but were lower and more variable, probably becausetheir strontium was derived in part from foods intropical winter habitats where lower87Sr/86Sr ratios are likely to predominate. Sr/Ca and Ba/Ca ratios decreased at each successive trophiclevel, supporting previous suggestions that Sr/Ca andBa/Ca ratios can be used to identify the trophic levelat which an organism is primarily feeding. The changesin Sr/Ca and Ba/Ca ratios we measured for vegetationand insects were comparable to similar measurementsmade previously (but based on single samples of eachorganism) in an alpine ecosystem. Changes in Sr/Ca andBa/Ca ratios between birds and their food have notpreviously been measured, but the values we obtainedwere similar to those for herbivorous and carnivorousmammals at similar trophic levels. Our results provideevidence that supports the use of Sr/Ca ratios in thedetermination of human paleodiets and suggests thatSr/Ca ratios may also provide a useful tool in studiesof modern food webs. Furthermore, our findings suggestthat 90Sr from nuclear fallout will notbioaccumulate in forests and that changes in Sr/Caratios between trophic levels will need to beconsidered in some cases when using87Sr/86Sr as a tracer of calciumbiogeochemistry. 相似文献
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广州市森林土壤水化学和元素收支平衡研究 总被引:2,自引:3,他引:2
为了探讨酸沉降对森林生态系统的影响,于1998年4月至1999年3月对广州市3个不同林分试验点的降雨,林内穿透雨和土壤渗透水进行了物理量测定和化学分析,据此计划了元素的收支平衡,研究表明:(1)SO4^2-和Ca^2 是土壤水中最主要的阴,阳离子,土壤水中的主要组分浓度的变化与树冠和凋落物淋溶的贡献以及土壤中一系列物理化学过程(如硝化作用,吸附作用,阳离子交换反应)有关;(2)土壤水中H^ 和Al^3 浓度的增高是土壤酸化的重要指标,可能对森林植被构成潜在危害;(3)S-沉降(>110kg/hm^2.a)可能不是目前土壤酸化的主要原因,也没引起土壤中碱性离子的大量淋失,由于研究区土壤有较强的吸附So4^2-的能力和容量,So4^2-和与之关系密切的Ca,Mg,K等元素在土壤中处于积累阶段;(4)过量的N沉降(>20kg/hm^2.a)和NH4^ 的硝化 作用是广州市森林土壤进一步酸化的主要原因,由于该地区NOx排放量逐年上升,因此N沉降对森林生态系统的负面影响会进一步加剧。 相似文献