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Spatial and seasonal variations in mobile carbohydrates in Pinus cembra in the timberline ecotone of the Central Austrian Alps
Gruber, A.
Pirkebner, D.
Oberhuber, W.
Wieser, G.
European journal of forest research
To test whether the altitudinal limit of tree growth is determined by carbons shortage or by a limitation in growth we investigated non structural carbohydrates and their components starch and total soluble sugars in Pinus cembra trees along an elevational gradient in the timberline ecotone of the Central Austrian Alps. NSC contents in needles, branches, stems, and coarse roots were measured throughout an entire growing season. At the tissue level NSC contents were not significantly more abundant in treeline trees as compared to trees at lower elevations. Along our 425 m elevational transect from the closed forest to the treeline we failed to find a stable elevational trend in the total NSC pool of entire trees and observed within season increases in the tree's NSC pool that can be attributed to an altitudinal increase in leaf mass as needles contained the largest NSC fraction of the whole tree NSC pool. Furthermore, whole tree NSC contents were positively correlated with net photosynthetic capacity. Although our observed NSC characteristics do not support the hypothesis that tree life at their upper elevational limit is determined by an insufficient carbon balance we found no consistent confirmation for the sink limitation hypothesis.
Non structural carbohydrates; seasonal variation; elevational gradient; timberline ecotone; treeline formation; treelife limitation
Related Articles
Similar variation in carbon storage between deciduous and evergreen treeline species across elevational gradients
Fajardo, Alex
Piper, Frida I.
Hoch, Günter
Annals of Botany
Background and Aims
The most plausible explanation for treeline formation so far is provided by the growth limitation hypothesis (GLH), which proposes that carbon sinks are more restricted by low temperatures than by carbon sources. Evidence supporting the GLH has been strong in evergreen, but less and weaker in deciduous treeline species. Here a test is made of the GLH in deciduous–evergreen mixed species forests across elevational gradients, with the hypothesis that deciduous treeline species show a different carbon storage trend from that shown by evergreen species across elevations.
Tree growth and concentrations of non-structural carbohydrates (NSCs) in foliage, branch sapwood and stem sapwood tissues were measured at four elevations in six deciduous–evergreen treeline ecotones (including treeline) in the southern Andes of Chile (40°S, Nothofagus pumilio and Nothofagus betuloides; 46°S, Nothofagus pumilio and Pinus sylvestris) and in the Swiss Alps (46°N, Larix decidua and Pinus cembra).
Key Results
Tree growth (basal area increment) decreased with elevation for all species. Regardless of foliar habit, NSCs did not deplete across elevations, indicating no shortage of carbon storage in any of the investigated tissues. Rather, NSCs increased significantly with elevation in leaves (P < 0·001) and branch sapwood (P = 0·012) tissues. Deciduous species showed significantly higher NSCs than evergreens for all tissues; on average, the former had 11 % (leaves), 158 % (branch) and 103 % (sapwood) significantly (P < 0·001) higher NSCs than the latter. Finally, deciduous species had higher NSC (particularly starch) increases with elevation than evergreens for stem sapwood, but the opposite was true for leaves and branch sapwood.
Considering the observed decrease in tree growth and increase in NSCs with elevation, it is concluded that both deciduous and evergreen treeline species are sink limited when faced with decreasing temperatures. Despite the overall higher requirements of deciduous tree species for carbon storage, no indication was found of carbon limitation in deciduous species in the alpine treeline ecotone.
Carbon supply; elevational gradient; Larix decidua; Nothofagus betuloides; Nothofagus pumilio; Patagonia; Pinus cembra; Pinus sylvestris; Swiss Alps; Alpine treeline
Related Articles
Seasonal Dynamics of Mobile Carbon Supply in Quercus aquifolioides at the Upper Elevational Limit
Zhu, Wan-Ze
Cao, Min
Wang, San-Gen
Xiao, Wen-Fan
Li, Mai-He
PLoS ONE
Many studies have tried to explain the physiological mechanisms of the alpine treeline phenomenon, but the debate on the alpine treeline formation remains controversial due to opposite results from different studies. The present study explored the carbon-physiology of an alpine shrub species (Quercus aquifolioides) grown at its upper elevational limit compared to lower elevations, to test whether the elevational limit of alpine shrubs (<3 m in height) are determined by carbon limitation or growth limitation. We studied the seasonal variations in non-structural carbohydrate (NSC) and its pool size in Q. aquifolioides grown at 3000 m, 3500 m, and at its elevational limit of 3950 m above sea level (a.s.l.) on Zheduo Mt., SW China. The tissue NSC concentrations along the elevational gradient varied significantly with season, reflecting the season-dependent carbon balance. The NSC levels in tissues were lowest at the beginning of the growing season, indicating that plants used the winter reserve storage for re-growth in the early spring. During the growing season, plants grown at the elevational limit did not show lower NSC concentrations compared to plants at lower elevations, but during the winter season, storage tissues, especially roots, had significantly lower NSC concentrations in plants at the elevational limit compared to lower elevations. The present results suggest the significance of winter reserve in storage tissues, which may determine the winter survival and early-spring re-growth of Q. aquifolioides shrubs at high elevation, leading to the formation of the uppermost distribution limit. This result is consistent with a recent hypothesis for the alpine treeline formation.
Related Articles
No evidence for depletion of carbohydrate pools in Scots pine (Pinus sylvestris L.) under drought stress
Gruber, A.
Pirkebner, D.
Florian, C.
Oberhuber, W.
Plant biology (Stuttgart, Germany)
The physiological mechanisms leading to Scots pine (Pinus sylvestris L.) decline in the dry inner Alpine valleys are still unknown. Testing the carbon starvation hypothesis, we analysed the seasonal course of mobile carbohydrate pools (NSC) of Scots pine growing at a xeric and a dry-mesic site within an inner Alpine dry valley (750 m a.s.l., Tyrol, Austria) during the year 2009, which was characterized by exceptional soil dryness. Although, soil moisture content dropped to c. 10% at both sites during the growing season, NSC concentrations were rising in all tissues (branch, stem, root) till end of July, except in needles where maxima were reached around bud break. NSC concentrations were not significantly different in the analysed tissues at the xeric and the dry-mesic site. At the dry-mesic site NSC concentrations in the above ground tree biomass were significantly higher during the period of radial growth. An accumulation of NSC in roots at the end of July indicates a change in carbon allocation after an early cessation in above ground growth, possibly due to elevated below ground carbon demand. In conclusion our results revealed that extensive soil dryness during the growing season did not lead to carbon depletion. However, even though C-reserves were not exhausted, a sequestration of carbohydrate pools during drought periods might lead to deficits in carbon supply that weaken tree vigour and drive tree mortality.
non-structural carbohydrates; Scots pine; drought; dry inner Alpine valley; carbon starvation; tree mortality
Related Articles
Do elevations in temperature, CO2, and nutrient availability modify belowground carbon gain and root morphology in artificially defoliated silver birch seedlings?
Huttunen, Liisa
Saravesi, Karita
Markkola, Annamari
Niemelä, Pekka
Ecology and Evolution
Climate warming increases the risk of insect defoliation in boreal forests. Losses in photosynthetically active surfaces cause reduction in net primary productivity and often compromise carbon reserves of trees. The concurrent effects of climate change and removal of foliage on root growth responses and carbohydrate dynamics are poorly understood, especially in tree seedlings. We investigated if exposures to different combinations of elevated temperature, CO2, and nutrient availability modify belowground carbon gain and root morphology in artificially defoliated 1-year-old silver birches (Betula pendula). We quantified nonstructural carbohydrates (insoluble starch as a storage compound; soluble sucrose, fructose, and glucose) singly and in combination in fine roots of plants under winter dormancy. Also the total mass, fine root proportion, water content, and length of roots were defined. We hypothesized that the measured properties are lower in defoliated birch seedlings that grow with ample resources than with scarce resources. On average, fertilization markedly decreased both the proportion and the carbohydrate concentrations of fine roots in all seedlings, whereas the effect of fertilization on root water content and dry mass was the opposite. However, defoliation mitigated the effect of fertilization on the root water content, as well as on the proportion of fine roots and their carbohydrate concentrations by reversing the outcomes. Elevation in temperature decreased and elevation in CO2 increased the absolute contents of total nonstructural carbohydrates, whereas fertilization alleviated both these effects. Also the root length and mass increased by CO2 elevation. This confirms that surplus carbon in birch tissues is used as a substrate for storage compounds and for cell wall synthesis. To conclude, our results indicate that some, but not all elements of climate change alter belowground carbon gain and root morphology in defoliated silver birch seedlings.
Betula pendula; climate change; fertilization; fine roots; folivory; plant sugar allocation
Related Articles
Morphological plasticity of ectomycorrhizal short roots in Betula sp and Picea abies forests across climate and forest succession gradients: its role in changing environments
Ostonen, Ivika
Rosenvald, Katrin
Helmisaari, Heljä-Sisko
Godbold, Douglas
Parts, Kaarin
Uri, Veiko
Lõhmus, Krista
Frontiers in Plant Science
Morphological plasticity of ectomycorrhizal (EcM) short roots (known also as first and second order roots with primary development) allows trees to adjust their water and nutrient uptake to local environmental conditions. The morphological traits (MTs) of short-living EcM roots, such as specific root length (SRL) and area, root tip frequency per mass unit (RTF), root tissue density, as well as mean diameter, length, and mass of the root tips, are good indicators of acclimation. We investigated the role of EcM root morphological plasticity across the climate gradient (48–68°N) in Norway spruce (Picea abies (L.) Karst) and (53–66°N) birch (Betula pendula Roth., B. pubescens Ehrh.) forests, as well as in primary and secondary successional birch forests assuming higher plasticity of a respective root trait to reflect higher relevance of that characteristic in acclimation process. We hypothesized that although the morphological plasticity of EcM roots is subject to the abiotic and biotic environmental conditions in the changing climate; the tools to achieve the appropriate morphological acclimation are tree species-specific. Long-term (1994–2010) measurements of EcM roots morphology strongly imply that tree species have different acclimation-indicative root traits in response to changing environments. Birch EcM roots acclimated along latitude by changing mostly SRL [plasticity index (PI) = 0.60], while spruce EcM roots became adjusted by modifying RTF (PI = 0.68). Silver birch as a pioneer species must have a broader tolerance to environmental conditions across various environments; however, the mean PI of all MTs did not differ between early-successional birch and late-successional spruce. The differences between species in SRL, and RTF, diameter, and length decreased southward, toward temperate forests with more favorable growth conditions. EcM root traits reflected root-rhizosphere succession across forest succession stages.
plasticity; ectomycorrhizal roots; morphological characteristics; root acclimation; silver birch; Norway spruce; forest succession; climate gradient
Related Articles
Effects of climate variables on intra-annual stem radial increment in Pinus cembra (L.) along the alpine treeline ecotone
GRUBER, Andreas
ZIMMERMANN, Jolanda
WIESER, Gerhard
OBERHUBER, Walter
Annals of forest science
Within the alpine treeline ecotone tree growth is increasingly restricted by extreme climate conditions. Although intra-annual stem growth recorded by dendrometers can be linked to climate, stem diameter increments in slow-growing subalpine trees are masked by changes in tree water status.We tested the hypothesis that intra-annual radial stem growth in Pinus cembra is influenced by different climate variables along the treeline ecotone in the Austrian Alps. Dendrometer traces were compared with dynamics of xylem cell development to date onset of cambial activity and radial stem growth in spring.Daily fluctuations in stem radius reflected changes in tree water status throughout the treeline ecotone. Extracted daily radial increments were significantly correlated with air temperature at the timberline and treeline only, where budburst, cambial activity and enlargement of first tracheids also occurred quite similarly. A close relationship was detected between radial increment and number of enlarging tracheids throughout the treeline ecotone.We conclude that (i) the relationship between climate and radial stem growth within the treeline ecotone is dependent on a close coupling to atmospheric climate conditions and (ii) initiation of cambial activity and radial growth in spring can be distinguished from stem re-hydration by histological analysis.
dendrometer; Pinus cembra; radial increment; treeline ecotone; xylem formation
Related Articles
Radial Growth of Qilian Juniper on the Northeast Tibetan Plateau and Potential Climate Associations
Qin, Chun
Yang, Bao
Melvin, Thomas M.
Fan, Zexin
Zhao, Yan
Briffa, Keith R.
PLoS ONE
There is controversy regarding the limiting climatic factor for tree radial growth at the alpine treeline on the northeastern Tibetan Plateau. In this study, we collected 594 increment cores from 331 trees, grouped within four altitude belts spanning the range 3550 to 4020 m.a.s.l. on a single hillside. We have developed four equivalent ring-width chronologies and shown that there are no significant differences in their growth-climate responses during 1956 to 2011 or in their longer-term growth patterns during the period AD 1110–2011. The main climate influence on radial growth is shown to be precipitation variability. Missing ring analysis shows that tree radial growth at the uppermost treeline location is more sensitive to climate variation than that at other elevations, and poor tree radial growth is particularly linked to the occurrence of serious drought events. Hence water limitation, rather than temperature stress, plays the pivotal role in controlling the radial growth of Sabina przewalskii Kom. at the treeline in this region. This finding contradicts any generalisation that tree-ring chronologies from high-elevation treeline environments are mostly indicators of temperature changes.
Related Articles
Root physiological adaptations involved in enhancing P assimilation in mining and non-mining ecotypes of Polygonum hydropiper grown under organic P media
Ye, Daihua
Li, Tingxuan
Zheng, Zicheng
Zhang, Xizhou
Chen, Guangdeng
Yu, Haiying
Frontiers in Plant Science
It is important to seek out plant species, high in phosphorus (P) uptake, for phytoremediation of P-enriched environments with a large amount of organic P (Po). P assimilation characteristics and the related mechanisms of Polygonum hydropiper were investigated in hydroponic media containing various concentrations of Po (1–8 mmol L-1) supplied as phytate. The mining ecotype (ME) showed significantly higher biomass in both shoots and roots compared to the non-mining ecotype (NME) at 4, 6, and 8 m mol L-1. Shoot P content of both ecotypes increased up to 4 mmol L-1 while root P content increased continually up to 8 mmol L-1 for the ME and up to 6 mmol L-1 for the NME. Root P content of the ME exceeded 1% dry weight under 6 and 8 mmol L-1. The ME had significantly higher P accumulation in both shoots and roots compared to the NME supplied with 6 and 8 mmol L-1. The ME showed higher total root length, specific root length, root surface area, root volume, and displayed significantly greater root length, root surface area, and root volume of lateral roots compared to the NME grown in all Po treatments. Average diameter of lateral roots was 0.17–19 mm for the ME and 0.18–0.21 mm for the NME. Greater acid phosphatase and phytase activities were observed in the ME grown under different levels of Po relative to the NME. This indicated fine root morphology, enhanced acid phosphatase and phytase activities might be adaptations to high Po media. Results from this study establish that the ME of P. hydropiper is capable of assimilating P from Po media and is a potential material for phytoremediation of polluted area with high Po.
organic phosphorus (Po); phytate; root morphology; acid phosphatase; phytase; phytoremediation
Related Articles
No evidence of carbon limitation with tree age and height in Nothofagus pumilio under Mediterranean and temperate climate conditions
Piper, Frida I.
Fajardo, Alex
Annals of Botany
Background and Aims
Trees universally decrease their growth with age. Most explanations for this trend so far support the hypothesis that carbon (C) gain becomes limited with age; though very few studies have directly assessed the relative reductions of C gain and C demand with tree age. It has also been suggested that drought enhances the effect of C gain limitation in trees. Here tests were carried out to determine whether C gain limitation is causing the growth decay with tree age, and whether drought accentuates its effect.
The balance between C gain and C demand across tree age and height ranges was estimated. For this, the concentration of non-structural carbohydrates (NSCs) in stems and roots of trees of different ages and heights was measured in the deciduous temperate species Nothofagus pumilio. An ontogenetic decrease in NSCs indicates support for C limitation. Furthermore, the importance of drought in altering the C balance with ontogeny was assessed by sampling the same species in Mediterranean and humid climate locations in the southern Andes of Chile. Wood density (WD) and stable carbon isotope ratios (δ13C) were also determined to examine drought constraints on C gain.
Key Results
At both locations, it was effectively found that tree growth ultimately decreased with tree age and height. It was found, however, that NSC concentrations did not decrease with tree age or height when WD was considered, suggesting that C limitation is not the ultimate mechanism causing the age/height-related declining tree growth. δ13C decreased with tree age/height at the Mediterranean site only; drought effect increased with tree age/height, but this pattern was not mirrored by the levels of NSCs.
The results indicate that concentrations of C storage in N. pumilio trees do not decrease with tree age or height, and that reduced C assimilation due to summer drought does not alter this pattern.
Carbon isotope composition; drought; hydraulic limitation hypothesis; Mediterranean climate; non-structural carbohydrates; Nothofagus pumilio; ontogeny; Patagonia
Related Articles
Temporal dynamic of wood formation in Pinus cembra along the alpine treeline ecotone and the effect of climate variables
Gruber, Andreas
Baumgartner, Daniel
Zimmermann, Jolanda
Oberhuber, Walter
Trees (Berlin, Germany : West)
We determined the temporal dynamic of cambial activity and xylem development of stone pine (Pinus cembra L.) throughout the treeline ecotone. Repeated micro-sampling of the developing tree ring was carried out during the growing seasons 2006 and 2007 at the timberline (1950 m a.s.l.), treeline (2110 m a.s.l.) and within the krummholz belt (2180 m a.s.l.) and the influence of climate variables on intra-annual wood formation was determined.
At the beginning of both growing seasons, highest numbers of cambial and enlarging cells were observed at the treeline. Soil temperatures at time of initiation of cambial activity were c. 1.5 °C higher at treeline (open canopy) compared to timberline (closed canopy), suggesting that a threshold root-zone temperature is involved in triggering onset of above ground stem growth.
The rate of xylem cell production determined in two weekly intervals during June through August 2006-2007 was significantly correlated with air temperature (temperature sums expressed as degree-days and mean daily maximum temperature) at the timberline only. Lack of significant relationships between tracheid production and temperature variables at the treeline and within the krummholz belt support past dendroclimatological studies that more extreme environmental conditions (e.g., wind exposure, frost desiccation, late frost) increasingly control tree growth above timberline.
Results of this study revealed that spatial and temporal (i.e. year-to-year) variability in timing and dynamic of wood formation of Pinus cembra is strongly influenced by local site factors within the treeline ecotone and the dynamics of seasonal temperature variation, respectively.
Cambium; intra-annual growth; Pinus cembra; temperature; tracheid production
Related Articles
Variation of Maximum Tree Height and Annual Shoot Growth of Smith Fir at Various Elevations in the Sygera Mountains, Southeastern Tibetan Plateau
Wang, Yafeng
Čufar, Katarina
Eckstein, Dieter
Liang, Eryuan
PLoS ONE
Little is known about tree height and height growth (as annual shoot elongation of the apical part of vertical stems) of coniferous trees growing at various altitudes on the Tibetan Plateau, which provides a high-elevation natural platform for assessing tree growth performance in relation to future climate change. We here investigated the variation of maximum tree height and annual height increment of Smith fir (Abies georgei var. smithii) in seven forest plots (30 m×40 m) along two altitudinal transects between 3,800 m and 4,200/4,390 m above sea level (a.s.l.) in the Sygera Mountains, southeastern Tibetan Plateau. Four plots were located on north-facing slopes and three plots on southeast-facing slopes. At each site, annual shoot growth was obtained by measuring the distance between successive terminal bud scars along the main stem of 25 trees that were between 2 and 4 m high. Maximum/mean tree height and mean annual height increment of Smith fir decreased with increasing altitude up to the tree line, indicative of a stress gradient (the dominant temperature gradient) along the altitudinal transect. Above-average mean minimum summer (particularly July) temperatures affected height increment positively, whereas precipitation had no significant effect on shoot growth. The time series of annual height increments of Smith fir can be used for the reconstruction of past climate on the southeastern Tibetan Plateau. In addition, it can be expected that the rising summer temperatures observed in the recent past and anticipated for the future will enhance Smith fir's growth throughout its altitudinal distribution range.
Related Articles
Waterlogging-induced changes in root architecture of germplasm accessions of the tropical forage grass Brachiaria humidicola
Cardoso, Juan Andrés
Jiménez, Juan de la Cruz
Rao, Idupulapati M.
AoB Plants
Brachiaria humidicola, a tropical forage grass, develops aerenchyma in nodal roots to adapt to waterlogging. A large body of work has focused on the functional role of aerenchyma in nodal roots under waterlogged soil conditions. On the other hand, quantification of responses of lateral roots to waterlogging has been often overlooked in past work. Our data indicated that although waterlogging reduced the overall proportion of lateral roots, its proportion significantly increased in the top 10 cm of the soil. This suggests that soil flooding increases lateral root proliferation of B. humidicola in upper soil layers. This may compensate the reduction of root surface area brought by the restriction of root growth at depths below 30 cm into waterlogged soil.
Waterlogging is one of the major factors limiting the productivity of pastures in the humid tropics. Brachiaria humidicola is a forage grass commonly used in zones prone to temporary waterlogging. Brachiaria humidicola accessions adapt to waterlogging by increasing aerenchyma in nodal roots above constitutive levels to improve oxygenation of root tissues. In some accessions, waterlogging reduces the number of lateral roots developed from main root axes. Waterlogging-induced reduction of lateral roots could be of adaptive value as lateral roots consume oxygen supplied from above ground via their parent root. However, a reduction in lateral root development could also be detrimental by decreasing the surface area for nutrient and water absorption. To examine the impact of waterlogging on lateral root development, an outdoor study was conducted to test differences in vertical root distribution (in terms of dry mass and length) and the proportion of lateral roots to the total root system (sum of nodal and lateral roots) down the soil profile under drained or waterlogged soil conditions. Plant material consisted of 12 B. humidicola accessions from the gene bank of the International Center for Tropical Agriculture, Colombia. Rooting depth was restricted by 21 days of waterlogging and confined to the first 30 cm below the soil surface. Although waterlogging reduced the overall proportion of lateral roots, its proportion significantly increased in the top 10 cm of the soil. This suggests that soil flooding increases lateral root proliferation of B. humidicola in the upper soil layers. This may compensate for the reduction of root surface area brought about by the restriction of root growth at depths below 30 cm. Further work is needed to test the relative efficiency of nodal and lateral roots for nutrient and water uptake under waterlogged soil conditions.
Lateral root proportion; oxygen deficiency; rooting depth; root length; soil flooding; vertical root distribution.
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Response of millet and sorghum to a varying water supply around the primary and nodal roots
Rostamza, M.
Richards, R. A.
Watt, M.
Annals of Botany
Background and Aims
Cereals have two root systems. The primary system originates from the embryo when the seed germinates and can support the plant until it produces grain. The nodal system can emerge from stem nodes throughout the plant's life; its value for yield is unclear and depends on the environment. The aim of this study was to test the role of nodal roots of sorghum and millet in plant growth in response to variation in soil moisture. Sorghum and millet were chosen as both are adapted to dry conditions.
Sorghum and millet were grown in a split-pot system that allowed the primary and nodal roots to be watered separately.
Key Results
When primary and nodal roots were watered (12 % soil water content; SWC), millet nodal roots were seven times longer than those of sorghum and six times longer than millet plants in dry treatments, mainly from an 8-fold increase in branch root length. When soil was allowed to dry in both compartments, millet nodal roots responded and grew 20 % longer branch roots than in the well-watered control. Sorghum nodal roots were unchanged. When only primary roots received water, nodal roots of both species emerged and elongated into extremely dry soil (0·6–1·5 % SWC), possibly with phloem-delivered water from the primary roots in the moist inner pot. Nodal roots were thick, short, branchless and vertical, indicating a tropism that was more pronounced in millet. Total nodal root length increased in both species when the dry soil was covered with plastic, suggesting that stubble retention or leaf mulching could facilitate nodal roots reaching deeper moist layers in dry climates. Greater nodal root length in millet than in sorghum was associated with increased shoot biomass, water uptake and water use efficiency (shoot mass per water). Millet had a more plastic response than sorghum to moisture around the nodal roots due to (1) faster growth and progression through ontogeny for earlier nodal root branch length and (2) partitioning to nodal root length from primary roots, independent of shoot size.
Nodal and primary roots have distinct responses to soil moisture that depend on species. They can be selected independently in a breeding programme to shape root architecture. A rapid rate of plant development and enhanced responsiveness to local moisture may be traits that favour nodal roots and water use efficiency at no cost to shoot growth.
Millet; Pennisetum glaucum; plasticity; adventitious roots; crown roots; lateral roots; sorghum; Sorghum bicolor; split-root system; soil moisture
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Interacting Microbe and Litter Quality Controls on Litter Decomposition: A Modeling Analysis
Moorhead, Daryl
Lashermes, Gwenaëlle
Recous, Sylvie
Bertrand, Isabelle
PLoS ONE
The decomposition of plant litter in soil is a dynamic process during which substrate chemistry and microbial controls interact. We more clearly quantify these controls with a revised version of the Guild-based Decomposition Model (GDM) in which we used a reverse Michaelis-Menten approach to simulate short-term (112 days) decomposition of roots from four genotypes of Zea mays that differed primarily in lignin chemistry. A co-metabolic relationship between the degradation of lignin and holocellulose (cellulose+hemicellulose) fractions of litter showed that the reduction in decay rate with increasing lignin concentration (LCI) was related to the level of arabinan substitutions in arabinoxylan chains (i.e., arabinan to xylan or A∶X ratio) and the extent to which hemicellulose chains are cross-linked with lignin in plant cell walls. This pattern was consistent between genotypes and during progressive decomposition within each genotype. Moreover, decay rates were controlled by these cross-linkages from the start of decomposition. We also discovered it necessary to divide the Van Soest soluble (labile) fraction of litter C into two pools: one that rapidly decomposed and a second that was more persistent. Simulated microbial production was consistent with recent studies suggesting that more rapidly decomposing materials can generate greater amounts of potentially recalcitrant microbial products despite the rapid loss of litter mass. Sensitivity analyses failed to identify any model parameter that consistently explained a large proportion of model variation, suggesting that feedback controls between litter quality and microbial activity in the reverse Michaelis-Menten approach resulted in stable model behavior. Model extrapolations to an independent set of data, derived from the decomposition of 12 different genotypes of maize roots, averaged within <3% of observed respiration rates and total CO2 efflux over 112 days.
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Comparing Morphological Plasticity of Root Orders in Slow- and Fast-growing Citrus Rootstocks Supplied with Different Nitrate Levels
Sorgonà', Agostino
Abenavoli, Maria Rosa
Gringeri, Pietro Giorgio
Cacco, Giovanni
Annals of Botany
Background and Aims
Studies of the plasticity of functional root traits involved in resource acquisition have focused mainly on root length without considering such 'morphological components' as biomass allocation, specific root length, root fineness, and tissue density that affect root length. The plasticity of the above components in response to nitrate supply was studied in each root order of two co-generic citrus rootstocks, namely the fast-growing Citrus jambhiri 'Rough Lemon' (RL) and the slow-growing Citrus reshni 'Cleopatra Mandarin' (CM).
Morphological traits of individual root orders of CM and RL, grown at different nitrate levels (NO3-N at 0·1, 0·5, 1 and 10 mm) were examined by using an image-specific analysis system.
Key Results
At high nitrate levels, the root length ratio, root mass ratio and, to a lesser degree, specific root length, root fineness and tissue density of tap and 1st-order laterals in both CM and RL were reduced. In 2nd-order laterals, however, the same treatment led to increased values of each morphological trait in CM but decreased values of the same traits in RL. At low nitrate supply, CM exhibited longer tap roots whereas RL developed longer 2nd-order laterals. These effects were due to root mass ratio and, to a lesser extent, specific root length.
Biomass allocation was the main component of nitrate-induced changes in root length ratio. The 2nd-order laterals were more sensitive to nitrate availability than the tap root and 1st-order laterals. At low nitrate availability, RL displayed longer 2nd-order lateral roots and lower root plasticity than CM. This suggests a different root growth strategy among citrus rootstocks for adapting to nitrate availability: RL invests in 2nd-order laterals, the preferred zone for acquiring the nutrient, whereas CM responds with longer tap roots.
Root morphology; root orders; phenotypic plasticity; nitrate; Citrus jambhiri; Citrus reshni
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Intraspecific variation in root and leaf traits and leaf-root trait linkages in eight aspen demes (Populus tremula and P. tremuloides)
Hajek, Peter
Hertel, Dietrich
Leuschner, Christoph
Frontiers in Plant Science
Leaf and fine root morphology and physiology have been found to vary considerably among tree species, but not much is known about intraspecific variation in root traits and their relatedness to leaf traits. Various aspen progenies (Populus tremula and P. tremuloides) with different growth performance are used in short-rotation forestry. Hence, a better understanding of the link between root trait syndromes and the adaptation of a deme to a particular environment is essential in order to improve the match between planted varieties and their growth conditions. We examined the between-deme (genetic) and within-deme (mostly environmental) variation in important fine root traits [mean root diameter, specific root area (SRA) and specific root length (SRL), root tissue density (RTD), root tip abundance, root N concentration] and their co-variation with leaf traits [specific leaf area (SLA), leaf size, leaf N concentration] in eight genetically distinct P. tremula and P. tremuloides demes. Five of the six root traits varied significantly between the demes with largest genotypic variation in root tip abundance and lowest in mean root diameter and RTD (no significant difference). Within-deme variation in root morphology was as large as between-deme variation suggesting a relatively low genetic control. Significant relationships existed neither between SLA and SRA nor between leaf N and root N concentration in a plant. Contrary to expectation, high aboveground relative growth rates (RGR) were associated with large, and not small, fine root diameters with low SRA and SRL. Compared to leaf traits, the influence of root traits on RGR was generally low. We conclude that aspen exhibits large intraspecific variation in leaf and also in root morphological traits which is only partly explained by genetic distances. A root order-related analysis might give deeper insights into intraspecific root trait variation.
fine root morphology; genetic variation; intraspecific variation; relative growth rate; root tissue density; specific root area
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Climate Warming and the Recent Treeline Shift in the European Alps: The Role of Geomorphological Factors in High-Altitude Sites
Leonelli, Giovanni
Pelfini, Manuela
Morra di Cella, Umberto
Garavaglia, Valentina
Global warming and the stronger regional temperature trends recently recorded over the European Alps have triggered several biological and physical dynamics in high-altitude environments. We defined the present treeline altitude in three valleys of a region in the western Italian Alps and reconstructed the past treeline position for the last three centuries in a nearly undisturbed site by means of a dendrochronological approach. We found that the treeline altitude in this region is mainly controlled by human impacts and geomorphological factors. The reconstruction of the altitudinal dynamics at the study site reveals that the treeline shifted upwards of 115 m over the period 1901–2000, reaching the altitude of 2505 m in 2000 and 2515 m in 2008. The recent treeline shift and the acceleration of tree colonization rates in the alpine belt can be mainly ascribed to the climatic input. However, we point out the increasing role of geomorphological factors in controlling the future treeline position and colonization patterns in high mountains.
Climate change; Treeline; Geomorphology; Tree rings; Larix decidua; European Alps
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Variation of the Linkage of Root Function with Root Branch Order
Long, Yingqian
Kong, Deliang
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Mounting evidence has shown strong linkage of root function with root branch order. However, it is not known whether this linkage is consistent in different species. Here, root anatomic traits of the first five branch order were examined in five species differing in plant phylogeny and growth form in tropical and subtropical forests of south China. In Paramichelia baillonii, one tree species in Magnoliaceae, the intact cortex as well as mycorrhizal colonization existed even in the fifth-order root suggesting the preservation of absorption function in the higher-order roots. In contrast, dramatic decreases of cortex thickness and mycorrhizal colonization were observed from lower- to higher-order roots in three other tree species, Cunninghamia lanceolata, Acacia auriculiformis and Gordonia axillaries, which indicate the loss of absorption function. In a fern, Dicranopteris dichotoma, there were several cortex layers with prominently thickened cell wall and no mycorrhizal colonization in the third- and fourth-order roots, also demonstrating the loss of absorptive function in higher-order roots. Cluster analysis using these anatomic traits showed a different classification of root branch order in P. baillonii from other four species. As for the conduit diameter-density relationship in higher-order roots, the mechanism underpinning this relationship in P. baillonii was different from that in other species. In lower-order roots, different patterns of coefficient of variance for conduit diameter and density provided further evidence for the two types of linkage of root function with root branch order. These linkages corresponding to two types of ephemeral root modules have important implication in the prediction of terrestrial carbon cycling, although we caution that this study was pseudo-replicated. Future studies by sampling more species can test the generality of these two types of linkage.
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Hund, Andreas
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A quantitative characterization of root system architecture is currently being attempted for various reasons. Non-destructive, rapid analyses of root system architecture are difficult to perform due to the hidden nature of the root. Hence, improved methods to measure root architecture are necessary to support knowledge-based plant breeding and to analyse root growth responses to environmental changes. Here, we report on the development of a novel method to reveal growth and architecture of maize root systems.
The method is based on the cultivation of different root types within several layers of two-dimensional, large (50 × 60 cm) plates (rhizoslides). A central plexiglass screen stabilizes the system and is covered on both sides with germination paper providing water and nutrients for the developing root, followed by a transparent cover foil to prevent the roots from falling dry and to stabilize the system. The embryonic roots grow hidden between a Plexiglas surface and paper, whereas crown roots grow visible between paper and the transparent cover. Long cultivation with good image quality up to 20 days (four fully developed leaves) was enhanced by suppressing fungi with a fungicide. Based on hyperspectral microscopy imaging, the quality of different germination papers was tested and three provided sufficient contrast to distinguish between roots and background (segmentation). Illumination, image acquisition and segmentation were optimised to facilitate efficient root image analysis. Several software packages were evaluated with regard to their precision and the time investment needed to measure root system architecture. The software 'Smart Root' allowed precise evaluation of root development but needed substantial user interference. 'GiaRoots' provided the best segmentation method for batch processing in combination with a good analysis of global root characteristics but overestimated root length due to thinning artefacts. 'WhinRhizo' offered the most rapid and precise evaluation of root lengths in diameter classes, but had weaknesses with respect to image segmentation and analysis of root system architecture.
A new technique has been established for non-destructive root growth studies and quantification of architectural traits beyond seedlings stages. However, automation of the scanning process and appropriate software remains the bottleneck for high throughput analysis.
Root system architecture; Maize; High-throughput; Imaging; Rhizoslide; Breeding; Agriculture
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Scots pines (Pinus sylvestris L.) in the inner-Alpine dry valleys of Switzerland have suffered from increased mortality during the past decades, which has been caused by longer and more frequent dry periods. In addition, a proceeding replacement of Scots pines by pubescent oaks (Quercus pubescens Willd.) has been observed. In 2003, an irrigation experiment was performed to track changes by reducing drought pressure on the natural pine forest. After nine years of irrigation, we observed major adaptations in the vegetation and shifts in Scots pine fine root abundance and structure. Irrigation permitted new plant species to assemble and promote canopy closure with a subsequent loss of herb and moss coverage. Fine root dry weight increased under irrigation and fine roots had a tendency to elongate. Structural composition of fine roots remained unaffected by irrigation, expressing preserved proportions of cellulose, lignin and phenolic substances. A shift to a more negative δ13C signal in the fine root C indicates an increased photosynthetic activity in irrigated pine trees. Using radiocarbon (14C) measurement, a reduced mean age of the fine roots in irrigated plots was revealed. The reason for this is either an increase in newly produced fine roots, supported by the increase in fine root biomass, or a reduced lifespan of fine roots which corresponds to an enhanced turnover rate. Overall, the responses belowground to irrigation are less conspicuous than the more rapid adaptations aboveground. Lagged and conservative adaptations of tree roots with decadal lifespans are challenging to detect, hence demanding for long-term surveys. Investigations concerning fine root turnover rate and degradation processes under a changing climate are crucial for a complete understanding of C cycling.
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Knowledge of the responses of soil nitrogen (N) availability, fine root mass, production and turnover rates to atmospheric N deposition is crucial for understanding fine root dynamics and functioning in forest ecosystems. Fine root biomass and necromass, production and turnover rates, and soil nitrate-N and ammonium-N in relation to N fertilization (50 kg N ha−1 year−1) were investigated in a temperate forest over the growing season of 2010, using sequential soil cores and ingrowth cores methods. N fertilization increased soil nitrate-N by 16% (P<0.001) and ammonium-N by 6% (P<0.01) compared to control plots. Fine root biomass and necromass in 0–20 cm soil were 13% (4.61 vs. 5.23 Mg ha−1, P<0.001) and 34% (1.39 vs. 1.86 Mg ha−1, P<0.001) less in N fertilization plots than those in control plots. The fine root mass was significantly negatively correlated with soil N availability and nitrate-N contents, especially in 0–10 cm soil layer. Both fine root production and turnover rates increased with N fertilization, indicating a rapid underground carbon cycling in environment with high nitrogen levels. Although high N supply has been widely recognized to promote aboveground growth rates, the present study suggests that high levels of nitrogen supply may reduce the pool size of the underground carbon. Hence, we conclude that high levels of atmospheric N deposition will stimulate the belowground carbon cycling, leading to changes in the carbon balance between aboveground and underground storage. The implications of the present study suggest that carbon model and prediction need to take the effects of nitrogen deposition on underground system into account.
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Kögel-Knabner, Ingrid
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The relationships between plant carbon resources, soil carbon and nitrogen content, and ectomycorrhizal fungal (EMF) diversity in a monospecific, old-growth beech (Fagus sylvatica) forest were investigated by manipulating carbon flux by girdling. We hypothesized that disruption of the carbon supply would not affect diversity and EMF species numbers if EM fungi can be supplied by plant internal carbohydrate resources or would result in selective disappearance of EMF taxa because of differences in carbon demand of different fungi. Tree carbohydrate status, root demography, EMF colonization, and EMF taxon abundance were measured repeatedly during 1 year after girdling. Girdling did not affect root colonization but decreased EMF species richness of an estimated 79 to 90 taxa to about 40 taxa. Cenococcum geophilum, Lactarius blennius, and Tomentella lapida were dominant, colonizing about 70% of the root tips, and remained unaffected by girdling. Mainly cryptic EMF species disappeared. Therefore, the Shannon-Wiener index (H′) decreased but evenness was unaffected. H′ was positively correlated with glucose, fructose, and starch concentrations of fine roots and also with the ratio of dissolved organic carbon to dissolved organic nitrogen (DOC/DON), suggesting that both H′ and DOC/DON were governed by changes in belowground carbon allocation. Our results suggest that beech maintains numerous rare EMF species by recent photosynthate. These EM fungi may constitute biological insurance for adaptation to changing environmental conditions. The preservation of taxa previously not known to colonize beech may, thus, form an important reservoir for future forest development.
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United States Patent 1 Sakaguchi 1 EMERGENCY COOLING APPARATUS FOR REACTORS [75] Inventor: Seiichiro Sakaguchi, Hitachi, Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Apr. 2, 1974 [21] Appl. No.: 457,365
[30] Foreign Application Priority Data Apr. 2, 1973 Japan 48-36727 [52) US. Cl. 176/37; 176/38; 176/65; 176/92 [51] Int. Cl GZlc 9/00 [58] Field of Search 176/50, 65, 37, 38, 92
[56} References Cited UNITED STATES PATENTS 3,438,431 4/1969 Dreyer et a1 176/37 3,607,630 9/1971 West et al 176/38 FOREIGN PATENTS OR APPLICATIONS 81,242 7/1963 France 176/38 1 Aug. 19, 1975 Primary Eraminen-Harvey E. Behrend Attorney, Agent, or Fzrm-Thomas E. Beall, Jr.
[57] ABSTRACT In a nuclear reactor of the type having the core surrounded by coolant and an inert cover gas all sealed within a container, an emergency cooling apparatus employing a detector that will detect cover gas or coolant, particularly liquid sodium, leaking from the container of the reactor, to release a heat exchange material that is inert to the coolant, which heat exchange material is cooled during operation of the reactor. The heat exchange material may be liquid nitrogen or a combination of spheres and liquid nitrogen, for example, and is introduced so as to contact the coolant that has leaked from the container quickly so as to rapidly cool the coolant to prevent or extinguish combustion.
11 Claims, 3 Drawing Figures PATENTED AUG 1 9 I975 FIG.
TlME (SECOND) AEROSOL SE PARATOR APPARATUS FOR LIQUIFY- ING NITROGEN 0. W O7. 0 8 0 6 Q 6 UL wmnZmmmEE EMERGENCY COOLING APPARATUS FOR REACTORS BACKGROUND OF THE INVENTION The present invention relates to an emergency cooling apparatus for nuclear reactors, particularly with respect to the container of the reactor.
Boiling water type nuclear reactors and pressurized type nuclear reactors each use water as a coolant thereof. Therefore, emergency cooling apparatus for the containers of these reactors employ water or ice, and different construction for the emergency cooling apparatus have been developed.
For a fast breeder nuclear reactor, which employs sodium as a coolant thereof, an emergency cooling apparatus for the container has not been provided as yet. Sodium will violently react with water to produce reaction products, such as hydrogen gas. Therefore, the emergency cooling apparatus for reactors employing sodium as a coolant cannot employ water or ice for emergency purposes, which has heretofore been conventional. Further, the sodium reacts with oxygen violently to make a sodium fire, which will greatly elevate the temperature in the container, due to the chemical reaction in addition to the elevation in pressure due to the nuclear energy. With such a pressure elevation and sodium as an aerosol, there will be considerable problems, such as fission products being dispersed in the atmosphere and fission products adhering to structure that may be removed. Choking or containment of a sodium fire by the use of an inert gas or powder fire extinguisher will take too long a time to extinguish the fire, further the fire extinguisher may produce additional problems, for example, the nozzle of the extinguisher may become clogged with powder.
SUMMARY OF THE INVENTION It is an object of the present invention to provide an emergency cooling apparatus for reactors, which will have a high safety and which can cool promptly.
The present invention, in brief, resides in that in an emergency cooling system for a nuclear reactor, there is provided means for detecting the emergency condition and providing a heat exchange material that is inert to the coolant, which is usually a liquid metal such as sodium, and which is cooled during the operation of the reactor, so that upon detecting the emergency condition, the heat exchange material may be released so as to contact with the coolant that has leaked from the container of the reactor to thereby promptly cool the leaked coolant and prevent or extinguish a fire.
BRIEF DESCRIPTION OF THE DRAWING Further objects, features and advantages of the present invention will become more clear from the following detailed description of preferred embodiments as shown in the accompanying drawing, wherein;
FIG. 1 is a cross-sectional view through a nuclear reactor employing one embodiment of an emergency cooling apparatus for reactors according to the present invention;
FIG. 2 is a graph showing the relationship between the temperature of the heat exchange medium, particularly solid balls, the temperature of the sodium coolant, and the cooling time; and
FIG, 3 is a schematic illustration of another embodiment according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, there is shown a nuclear reactor core 16 that is disposed in the core container 17. The core container 17 is sealed by means of a plug 23 at the top thereof, and provided with an inlet pipe 20 and outlet pipe 19 for a coolant such as liquid sodium. The coolant 26 for the reactor enters the core container 17 from the inlet pipe 20 and is discharged through the outlet pipe 19 after cooling the nuclear reactor core 16. Control rods 24 are provided in a conventional manner and further an inert cover gas 25 is provided between the liquid coolant and the plug 23.
The core container 17 is in turn contained within a safety container 21 that is disposed beneath a floor 10, with suitable supporters 18 supporting the container 17 within the container 21 and a shield of graphite 22 covering the container 21. On the floor 10, there is mounted a further container 1, which is provided with a suitable crane 2, a fuel exchanger mechanism 3, and part of an emergency cooling apparatus for the container I.
The emergency cooling apparatus of the present invention comprises a quantity of heat exchange material, particularly balls or spheres 7 that are preferably constructed of stainless steel, a pair of heat exchange material containers 4, each of which is covered by a heat insulation such as asbestos and has lower and upper openings provided with electromagnetic valves 8, 9. The electromagnetic valves are provided with shutters 8a, 9a and clamps 8b, 9b for securing the electromagnetic valves 8, 9 to the ball or heat exchange material containers 4. Frames 15 are provided to mount each of the containers 4 on the floor 10 at a proper height. Heat exchange material, particularly ball, guides 5 have their upper end fixed in communication with the respective container 4 and their lower end disposed adjacent to floor 10 to deliver the heat exchange material to the floor 10 in the vicinity of the upper portion of the plug 23 upon opening of the electromagnetic valves 8, for each of the containers 4.
A contact type leakage detector 14 is disposed on the floor 10 above the core container, particularly adjacent the upper portion of the plug 23 so as to detect leaking cover gas 25 or leaking coolant 26. Upon detecting such leakage, the detector 14 will send an electric signal to the electromagnetic valves 8 and 9 through control wires 13 to open the electromagnetic valves 8, 9.
During operation of the nuclear reactor, refrigeration or low temperature apparatus 11 such as apparatus for liquifying nitrogen gas, are connected to the ball containers 4 through cooling pipes 12 for circulating liquid nitrogen through the ball containers 4 to maintain the heat exchange material at a low temperature.
During operation of the nuclear reactor, the low temperature apparatus 11 will run constantly to circulate the liquid nitrogen so that the temperature of the solid balls 7 will be kept at -200C. When leakage occurs due to an abnormal condition or emergency condition of the reactor such that the sodium coolant 26 for the reactor core 16 may leak into the container 1 to form a pool of liquid sodium on the floor 10, or when the cover gas, which is usually argon gas, and sodium vapor leak from the container I, this may bring about an abnormal temperature and pressure elevation in the container 1. Such an abnormal condition is detected by the leakage detector 14, which generates an electric signal when the leakage detector 14 is contacted with the liquid sodium leaked from the core container I7 onto the floor I0. The detector may also detect coolant vapor or the cover gas leakage. With such an electric signal indicating leakage, the electromagnetic valves 8 and 9 are operated to open the shutters 8a and 9a, which will result in releasing of the solid balls. The falling solid balls will be conducted by the guides to spread out so as to cover all of the floor 10. The solid balls on the floor 10 will make quick heat exchange contact with the pool of sodium and the argon gas leaked into the container 1, to lower the temperatures of the material that has leaked. Since sodium has a high surface heat transfer coefficient with a solid surface, it is promptly cooled. Accordingly, if the sodium appears in a liquid phase, it is promptly solidified, which will prevent a sodium fire or extinguish a sodium fire that has already started.
The diameter of the solid balls is selected for its thermal effect, fluidity of the falling balls, ease of withdrawal, economy, etc., and preferably is within the range of several millimeters diameter to several tens of millimeters diameter.
Assuming that an accidental leakage of the sodium has occurred, the efficiency with which the sodium is cooled, by way of example with stainless steel balls, will be explained hereinafter by computation.
The change in temperature of the sodium and the balls with time is given by the following equation:
p,p density C, C specific heat V, V,- volume of one of the balls, volume occupied by one of the balls surface heat transfer coefficient between the ball and the sodium 5 surface area of the balls t time T, T temperature In the above equation, an item of reaction heat and heat discharge into the outside of the system are out of consideration for simplifying the equation. Further it is assumed that temperature distributions of the sodium and the balls are uniform.
Computations employing the above equations are shown graphically in FIG. 2, which result is based on l ton of leaked sodium at 500C being cooled by IO tons of stainless steel balls, each of which has a 10 millimeter diameter, with the balls being cooled to --200C by liquid nitrogen, and with a surface heat transfer coefficient of 10" Kcal/M h C, and further with the balls falling from a height of 2 meters. In FIG. 2, A represents the temperature curve of the sodium; B represents the temperature curve of the stainless steel balls; and C represents the equilibrium temperature line. As is apparent from FIG. 2, the balls contact with the sodium in about 0.65 seconds after starting their fall, and thereafter they promptly cool the sodium to about C. As the sodium is solidified at this temperature, it will not burn with any smoke or flame, even if its surface is oxidized. The cooling ability of the solid balls which have fallen declines by the temperature elevation thereof due to collapsed heat and heat brought about by free convection of the gas from its circumference, and thereafter comes to an end. However, since the shutters 8a and 9a of the ball containers 4 are opened, the liquid nitrogen or gas within the containers is supplied at a low temperature by the cooling pipes 12 to thereby further bring about a cooling effect, and this gas is circulated as before through the refrigeration apparatus 11 to continue the cooling.
Instead of using stainless steel balls as the heat exchange material, other heat exchange material of large heat capacity may be used as lead, zinc, aluminum, and different kinds of steel or iron, with the steel or iron being coated by a material that has a coexistence with the sodium that is excellent, for example coating with stainless steel. Further, the heat exchange material may employ solid particles of fireproof material such as a fire brick, which is much the same as metals in heat capacity, but smaller than the metals in heat conductivity. Accordingly, in the case of non-metallic fireproof material being used, the diameter of the nonmetallic fireproof material balls or particles must be smaller to obtain an adequate heat conductivity effect.
Further, the heat exchange material that is circulated through the containers 4 by pipes 12 and the apparatus 1 1 may be liquid argon or liquid helium, instead of the liquid nitrogen specifically mentioned above.
A further embodiment of the present invention is shown in FIG. 3 in schematic form, since the structure is the same as that shown and described with respect to FIG. 1, except for the specific differences that will appear below.
The low temperature apparatus or refrigeration apparatus II will liquify an inert gas such as nitrogen gas, or one of the above mentioned gases. The liquified gas from apparatus 11 is fed by means of pump 27 through valves 32 and pipes 28 to each of two or more nozzles 29, which nozzles are disposed so that the liquid nitrogen sprayed from the nozzles 29 will rapidly cool any pool of liquid coolant, such as a sodium, that may have leaked from the core container (shown in FIG. 1) into the container 1'. The blower 30 is used for withdrawing part of the inert gas from the container 1, which inert gas being fed into the container 1' by the nozzles 29 will cause a pressure elevation within the container 1', unless removed. An aerosol separator 31 will receive the gas from the blower 30 and separate solid particles, such as sodium aerosol, from the inert gas, so that only the inert gas will be returned to the apparatus 11 to be liquified. Thus, the containers 4 and guides 5 with the spherical heat exchange materials therein are replaced by nozzles 29 in FIG. 3, so that instead of liquified inert heat exchange gas and cooled spheres being fed to the pool of sodium coolant upon emergency in FIG. 1, only liquified inert gas, such as nitrogen, will be fed to the pool of sodium coolant by nozzles 29 in the embodiment of FIG. 3. FIG. 1 employs both spherical solid particles and liquified inert gas as a heat exchange material, whereas FIG. 3 employs only liquified inert gas as a heat exchange material.
With the construction of FIG. 3, when leakage is detected by the detector (not shown in FIG. 3) as described above with respect to FIG. I, for example when sodium coolant leaked into the container 1' is detected, the detector will send an electric signal to the valves 32, so that the valves 32 will be opened and permit the flow of liquified inert gas from the apparatus H to the nozzles 29 by operation of the pump 27, so that liquified inert gas will be sprayed by nozzles 29 upon the pool of coolant. Thereby, the pool of leaked coolant is quickly cooled by effective utilization of the latent and sensible heat of the liquified inert gas, to prevent or extinguish fires as mentioned above with respect to the operation of FIG. 1.
While preferred embodiments of the present invention have been described in detail for purposes of illustration and the advantages of their specific details, further embodiments, variations and modifications are contemplated within the broader aspects of the present invention. all as determined by the spirit and scope of the following claims.
What is claimed is:
1. Emergency cooling apparatus for nuclear reactors having a normally sealed core container for containing a nuclear core, a coolant of liquid metal around the core within the core container, a cover gas above the liquid coolant within the core container, and a second auxiliary apparatus container above the core container, which comprises: means for detecting at least one of the cover gas and the liquid metal coolant leaked into the second container to produce an emergency signal, means for containing a heat exchange material that is inert to the liquid metal coolant; means for cooling the heat exchange material during the operation of the nuclear reactor; means for dispensing the heat exchange material to the lower portion of said second container where the liquid metal coolant would collect upon leakage to contact with the leaked coolant; and valve means normally preventing dispensing of the heat exchange material and releasing the heat exchange material to said dispensing means only in response to said emergency signal in accordance with the detection of the leaked coolant or cover gas by the means for detecting.
2. The emergency cooling apparatus for nuclear reactors as defined in claim 1, wherein said heat exchange material comprises a plurality of solid balls.
3. The emergency cooling apparatus for nuclear reactors as defined in claim 2, wherein each of said solid balls has a surface of stainless steel.
4. The emergency cooling apparatus for nuclear reactors as defined in claim 2, wherein said heat exchange material further comprises a fluid circulating around said solid balls, and said means for cooling includes refrigeration means cooling said fluid and circulating said fluid through said balls.
5. The emergency cooling apparatus for nuclear reactors as defined in claim 4, wherein said cooling means further comprises cooling supply and exhaust pipes communicatiing between said means for containing and said refrigeration means.
6. The emergency cooling apparatus for nuclear reactors as defined in claim 5, wherein said means for containing is cylindrical in its shape and has shutter means in the lower and upper portions thereof, with said shutter means constituting said valve means.
7. The emergency cooling apparatus for nuclear reactors as defined in claim 6, wherein said shutter means includes an electromagnetic operator means responsive to the emergency signal.
8. The emergency cooling apparatus for nuclear reactors as defined in claim 7, wherein said electromagnetic operator means is connected with said detecting means through electric wires.
9. The emergency cooling apparatus for nuclear reactors as defined in claim 4, wherein said refrigeration means liquifies said heat exchange fluid.
10. The emergency cooling apparatus for nuclear reactors as defined in claim 1, wherein said heat exchange material is a gas, said means for cooling liquifies said gas, and said means for dispensing is nozzle means for spraying said gas across the bottom of said second container.
11. The emergency cooling apparatus for nuclear re actors as defined in claim 10, further including means responsive to said emergency signal for removing gas from the upper portion of said second container and delivering the gas to said means for cooling the heat exchange material; means for separating the gaseous heat exchange material from aerosol particles of said liquid metal coolant upstream of said means for cooling, to deliver only the thus separated heat exchange gas to said means for cooling.
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"It's not a five star standard, but it's worth it's price. It's one of few hotels in the area with affordable price. Awesome swimming pool, 3m depth! The best part of the beach belongs to this hotel. This hotel gives the most privacy comparing to other hotels in neighbourhood. If y..."
A Traveller, Feb 2015, GB
Le Meridien Fisherman's Cove
Excellent 4.5 / 5 ( 88 reviews )
Most recent review
"The hotel is starting to look a bit tired but I understand it will soon close for refurbishment. The staff are great, very friendly and willing to look at everything to make ones visit comfortable. Some sites say this hotel is 5 star and others 4 star. Whatever I am sure that once the refurbishme..."
A Traveller, Dec 2014, IE
Coco D'Or
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Lemongrass Lodge
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Hotels within 2 miles of Beau Vallon Beach
Hilton Seychelles Northolme Resort & Spa
Excellent 4.6 / 5 ( 76 reviews )
Most recent review
"I was hesitant to book a trip to the Seychelles, not sure of how socially tolerant a small island would be. As it turns out, my partner and I had no problems at all. The Hilton staff was very professional."
A Traveller, Mar 2015, IE


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Strong Talks Merging "Super-Cute" with "Super-Psycho" for "Arkham Knight's" Harley Quinn
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This property allows you to book online with a credit card. After submitting a reservation request, the owner or manager has 24 hours to accept, at which time your card will be charged and you will receive an email confirmation
Fort Grounds (Sherman Park) Vacation Rentals Show this location only Back to top
$99 - $535 per night 2-3 night min stay
$395 - $550 per night 1-6 night min stay
$200 per night 3 night min stay
$175 - $250 per night 4 night min stay
$219 - $249 per night 3 night min stay
$1,505 per week 7 night min stay
$125 - $325 per night 3-6 night min stay
$200 per night 3 night min stay
Recent Lake Coeur d'Alene reviews
"If I could give a 6-star (or more!) rating, I absolutely would. Rustic elegance sums it up perfectly. The location is remote (22 miles off the 90 and located in Harrison, Idaho), so you truly feel like you are getting away- and in a very good way! This was one of my favorite family vacations ever, and I've gone on many. Well-maintained, beautiful home and grounds. Let's start with the panoramic views- from the deck, pebble beach, fireplace 'lounging' area, front lawn - it was breathtaking, especially the sunsets. This really is one of the best places on the lake, especially given Western exposure. By the way, the fireplace area was reminiscent of a high-end lodge hotel environment was a very pleasant surprise, as it wasn't even pictured in the listing! The inside of the cabin was amazing, the kitchen was the most well-stocked I've ever encountered in a rental and it has been recently remodeled. Nice tile, granite countertops, soft carpet. TV for those that need it with satellite. Plenty of space to lounge- liked the two bedrooms upstairs (A-frame style with rooms on either side both with a queen + twin), then two queen rooms downstairs. The owner, John, was amazingly helpful and answered all of my questions (I'll admit, I'm super Type A and do my research and he never lost patience on me at all, ha). We rented a boat for one day which is fun, as there is a slip - but, beware, boat rental is very expensive. There is an adorable canoe on property which we had fun with, great swimming beach. Harrison, ID is 6 miles away and a cute visit, you can rent bikes along the lake which I recommend. We didn't eat out much and instead toted most of our meals over. Mostly relaxed around cabin/outside and it was wonderful. It really is the best cabin ever- no joke! Thanks John, for your amazing hospitality."Guest: Teresa Date of Stay: August 2014 Review Submitted: September 16, 2014View listing
"We had a great time, and slept very comfortably for our weekend stay. Stand up paddle boards, hot tubbing and Bon fires were the perfect way for us to end our summer. We will be coming back next summer, and making it an even longer trip!"Guest: Samantha Date of Stay: September 2014 Review Submitted: September 21, 2014View listing
"This well-kept cabin is great for a quiet week on the water. Room for 2 couples or one family, it has everything you need to relax and recreate on lovely Lake Coeur d'Alene, including a boat dock, kayaks and paddle boat. We spent many hours on the large deck and down on the dock, watching bald eagles, osprey, Canadian geese and hummingbirds. We also saw lots of people fishing. The cabin is located on a steep slope with lots of stairs, so consider that when you pack. Also, although we brought in drinking water at the owner's request, we had no problem with the tap water from their well. We have stayed on the lake for many years and would recommend this cabin to someone looking for comfort without extravagance."Guest: Greg Date of Stay: August 2014 Review Submitted: August 12, 2014View listing
"The house is right on the water, comfortable, inviting, beautifully decorated, well stocked with everything we needed and very, very clean. The entire property has a wonderful vibe about it - we felt instantly at home and nestled right in, enjoying easy lake access and beautiful sunsets from the Western exposure. We absolutely loved our stay there and look forward to renting it again next summer. Additionally, the owner was kind, courteous and handled our transaction quickly and easily. We wish all owners could be like that!"Guest: Seattle Date of Stay: August 2014 Review Submitted: November 14, 2014View listing
Featured Destinations: Estes Park Cabins, Fort Myers Beach Rentals, Wailea Beach Villas, Wisconsin Dells Cabins


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Screen legend Gregory Peck earned an Oscar® for his performance in this seminal look at racism in a small, segregated Southern town. Peck plays a lawyer and single father who defends a black man accused of raping a white woman. Determined to seek justice, he refuses to back down -- even when he and his family are ostracized and threatened. Based on the Pulitzer Prize-winning book by Harper Lee, this powerful film earned eight Academy Award nominations, including Best Picture, and won three. Featuring the screen debut of Oscar®-winner Robert Duvall. Awarded to the National Film Registry.
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text: Football May 24, 2014 By Mark Farrelly Vine: Xabi Alonso's Reaction To Gareth Bale's Miss Was Very Like Tom From Fr Ted 'Have ye nothin I could kill?.. Well feck it! Feck it anyway!' ... 'Run Dougal. Run quite fast!' Here's the miss. Share this article Article written by Mark Farrelly See more from Mark Farrelly Editor of Balls.ie, chief tea expert on TheSlicedPan.com. Former Miss World 1997 contestant.


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Technology Credit Union Private Banking Manager NMLS# 719388Phone: 408-437-3707 Fax: 408-441-4779 Mobile: 408-386-4083 EmailMake Appointment
Wendy Miner has over 25 years of industry experience, including six years at Bank of America and 14 years at Wells Fargo Bank. Wendy came to Technology Credit Union in 2006 as a Private Banking manager, bringing to the organization a wealth of knowledge and extensive experience in premier client management. During her career Wendy has received a number of service and achievement awards.
Wendy holds a Series 6, Series 63, a California Insurance License and a Notary Public License, received her Private Banking School Certification, and is currently pursuing her CFP Certification.
In her spare time she enjoys spending time with family, traveling, reading, and cooking. She volunteers as a Council Member and Lector with her church and at the Boccardo Housing Consortium.
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