共查询到20条相似文献,搜索用时 0 毫秒
1.
Structure, distribution of species and inundation in a riparian forest of Rio Paraguai, Pantanal, Brazil 总被引:2,自引:1,他引:1
Geraldo Alves Damasceno-Junior Joo Semir Flavio Antonio Maës Dos Santos Hermgenes de Freitas Leito-Filho 《Flora》2005,200(2):119-135
A phytosociological study was conducted in a riparian forest of the Rio Paraguai near Corumbá and Ladário in the state of Mato Grosso do Sul, Brazil. The topographic distribution of species was correlated with durations of the river's seasonal floodings and the cumulative time of flooding between 1974 and 1995. One hundred and eight contiguous 10×10 m plots were systematically established. All individuals with more than 15 cm of girth at breast height (gbh=1.3 m) were sampled. A total of 695 individuals distributed among 37 species, 35 genera and 23 families were found. The Shannon index (H′) for species diversity was 2.7. The highest importance value (IV) was found for Inga vera ssp. affinis, followed by Triplaris gardneriana, Ocotea diospyrifolia, Crataeva tapia and Vochysia divergens. The plots were classified into two groups according to their distance from the margin, applying Ward's method of classification and principal coordinate analysis (PCO) on the same Bray Curtis distance matrix. The topical environments were divided into four bands by Two-Way Indicator Species Analysis (TWINSPAN), and the species were also grouped into four groups. Flooding in these groups ranged from regular inundation in all 23 years of the historical series of the Ladário gauge to sporadic flooding for a maximum of 2 consecutive years. 相似文献
2.
Abstract. Flooding patterns and variations in the composition and successional trends of riparian vegetation in the upper and lower Red Deer River in southern Alberta, Canada, were studied in order to establish which flood regimes were most important in the regeneration and maintenance of riparian vegetation communities, with a particular focus on riparian poplars. The dominant riparian tree in the upper river is Populus balsamifera with some Picea glauca and in the lower river Populus deltoides (the plains cottonwood). Dendrochronological studies of the poplars along the river show that major periods of regeneration correspond with major flood events during the record period. Extensive cottonwood regeneration occurred in the period 1900–20, corresponding with a series of floods, some as high as the 1 in 100-year event. In addition, just prior to and during this period there was a significant reduction in use of the floodplain by bison, clearance of forests and a higher incidence of fires in upper reaches of the river and a series of high rainfall years. A series of floods greater than the 1 in 10-year flood occurred in the 1950s and stimulated the most extensive regeneration of poplars experienced since the 1920s. Parts of the lower Red Deer floodplain are now at elevations well above the 1 in 100-year flood event. It is suggested that fringe replenishment of riparian poplars is currently the dominant form of regeneration and that the large stands of mature poplars found on the floodplain, initiated during the end of the last century and first decades of this century, are unlikely to be replaced unless large floods (>1 in 50-year events) occur again. Construction of the Dickson Dam above the city of Red Deer in 1983 has led to attenuation of floods and a reduced likelihood that extensive flooding and poplar regeneration will occur again. A number of recommendations are made regarding flow management to both retain the fringe regeneration of poplars currently occurring and to stimulate more widespread regeneration of poplars on the floodplain. 相似文献
3.
Effects of natural disturbance on the regeneration of riparian forests in a Chichibu Mountains,central Japan 总被引:6,自引:0,他引:6
Disturbances in the riparian area had a large effect on each stage of regeneration in riparian forests dominated by Fraxinus platypoda in the Chichibu Mountains, central Japan. F. platypoda adapted well to various disturbances in frequency and size such as landslides and canopy gap formation.The spatial distribution and age structure of F. platypoda were studied in relation to the disturbance regime of the riparian zone. The bell-shaped size and age distributions of F. platypoda suggest that F. platypoda trees were established synchronously in a large disturbance site caused by an earthquake landslide about 200 years ago. For the past 200 years, the topography has been stable and the canopy gap has been recovered by advance regenerated saplings.The distribution of F. platypoda saplings was restricted to an abandoned channel and part of a floodplain. These topographical sites formed by gravel provided safe sites for saplings because stream disturbances did not occur for a long time. Channel bars were under low shade stress because of the lack of herbs and a litter layer, which represents a safe site for seedling establishment. However, the seedling bank could have been destroyed by high frequent flooding caused by large typhoons and the establishment of seedlings might have been prevented for a long time.The regeneration process of F. platypoda was explicated based on the gap dynamics theory during the stable period of topography. On the other hand, an even-aged forest was established in a large scale disturbance site.Nomenclature: Ohwi & Kitagawa (1992) 相似文献
4.
Forest fires frequently occur in boreal forests,and their effects on forest ecosystems are often significant in terms of carbon flux related to climate changes.Soil respiration is the second largest carbon flux in boreal forests and the change in soil respiration is not negligible.Environmental factors controlling the soil respiration,for example,soil temperature,are altered by such fires.The abnormal increase in soil temperature has an important negative effect on soil microbes by reducing their activities or even by killing them directly with strong heat.On the other hand,although vegetation is directly disturbed by fires,the indirect changes in soil respiration are followed by changes in root activities and soil microbes.However,there is very limited information on soil respiration in the forests of Northeast China.This review,by combining what is known about fire influence on soil respiration in boreal forests from previous studies of post-fire effects on soil conditions,soil microbes,and forest regeneration,presents possible scenarios of the impact of anticipated post-fire changes in forest soil respiration in Northeast China. 相似文献
5.
Laiye Qu Keming Ma Xiaoniu Xu Lihua Wang Kaichiro Sasa 《Frontiers of Biology in China》2009,4(2):180-186
Forest fires frequently occur in boreal forests, and their effects on forest ecosystems are often significant in terms of
carbon flux related to climate changes. Soil respiration is the second largest carbon flux in boreal forests and the change
in soil respiration is not negligible. Environmental factors controlling the soil respiration, for example, soil temperature,
are altered by such fires. The abnormal increase in soil temperature has an important negative effect on soil microbes by
reducing their activities or even by killing them directly with strong heat. On the other hand, although vegetation is directly
disturbed by fires, the indirect changes in soil respiration are followed by changes in root activities and soil microbes.
However, there is very limited information on soil respiration in the forests of Northeast China. This review, by combining
what is known about fire influence on soil respiration in boreal forests from previous studies of post-fire effects on soil
conditions, soil microbes, and forest regeneration, presents possible scenarios of the impact of anticipated post-fire changes
in forest soil respiration in Northeast China. 相似文献
6.
Takato Kobayashi Tohru Nakashizuka Masahiko Kitahara Masako Kubo Shoko Ito 《Ecological Research》2008,23(3):493-502
To clarify the habitat requirements of the near-threatened butterfly, Sasakia charonda (Lepidoptera, Nymphalidae), we studied the distribution pattern of its host trees, Celtis sinensis and Celtis jessoensis, and the utilization patterns of various vegetation types by this butterfly in the Oofukasawa River basin in Hokuto City,
Yamanashi Prefecture, central Japan. Two species of host trees, C. sinensis and C. jessoensis (height = 2 m or more) were found in riparian forests on sandbanks (hereinafter, riparian forest), in forest regenerated
after landslides on valley walls (landslide tracks), in secondary deciduous forests consisting mainly of Quercus acutissima or Quercus serrata and in forests established at abandoned paddy fields and their periphery, where weeds and shrubs used to be mown frequently
to avoid shade on the paddies before their abandonment. This suggests that they are pioneer species, and their distribution
and regeneration depend on natural and/or human disturbances. Host trees above 2 m were preferred by larvae, and there were
very few such trees in secondary forests. More overwintering larvae occurred in riparian forests than at other sites. The
number of S. charonda adults was highest at the edge of riparian forests, and we observed a variety of behaviors such as puddling, chasing and
mating there. Although the number of adult butterflies was smaller inside and at the edge of secondary forests than in riparian
forests, puddling by males and roosting on the trunk of Q. acutissima or Q. serrata by females were observed more frequently there than in riparian forests. Thus, we conclude that landscapes including both
riparian forests with natural disturbance and secondary forests with Quercus trees are necessary to maintain host Celtis trees and S.
charonda populations. 相似文献
7.
Linking riparian vegetation types and fluvial geomorphology along the Sabie River within the Kruger National Park, South Africa 总被引:1,自引:0,他引:1
Vegetation types were studied in relation to the fluvial geomorphology along the mixed bedrock‐alluvial Sabie River within the Kruger National Park, Mpumalanga, South Africa. Six vegetation types were identified using TWINSPAN analysis, namely: Phragmites mauritianus , Phyllanthus reticulatus , Breonadia salicina , Combretum erythrophyllum , Diospyros mespiliformis and Spirostachys africana vegetation types. Spirostachys africana and Diospyros mespiliformis vegetation types were found to occur predominantly on the stable, infrequently flooded macro‐channel banks, while the remaining four vegetation types were found almost exclusively along the more geomorphically and hydrologically dynamic macro‐channel floor. The degree of bedrock or alluvial influence was identified as being an integral factor in the distribution of the four macro‐channel floor vegetation types at both the morphological unit and the channel type scale. The geomorphological continuum from the bedrock influenced bedrock anastomosing channel types, to mixed anastomosing and pool‐rapid channel types, to the fully alluvial braided channel types, is reflected in the change in species composition from Breonadia salicina vegetation type, to Phyllanthus reticulatus and Phragmites mauritianus vegetation types, to Combretum erythrophyllum vegetation types, respectively. Given the vegetation/fluvial geomorphology links established, changes in vegetation composition are proposed in response to scenarios of geomorphological change as a result of progressive sedimentation. 相似文献
8.
Two methods of estimating the lateral migration of a river channel have been proposed. The first method is based on Coarse Woody Debris (CWD) dating. The terraces of the Mala Panew River are mainly covered with plantations of Pinus sylvestris where individual trees grow at equal distances to each other. During times of high discharges trees fall onto the riverbed providing information on the extent of flood plain erosion. The ages of CWD and the surface of the eroded flood plain provide an estimation of the rate of lateral migration. The erosion rates measured at two sites in the Mala Panew River were between 0.24 and 0.36 m/year.Another way of reconstructing the rate of lateral migration is by dating trees growing on different-aged sandy meander bars. These levels are primarily covered with Alnus glutinosa and Alnus incana. The oldest trees growing on each level give information about the minimum age of that level, which allows us to reconstruct the rate of lateral migration. The lateral migration of the channel has also been estimated dating the oldest trees growing on mid-channel islands separated from the lateral banks. The values obtained for 10 sites of the Mala Panew channel oscillate between 0.07 and 1.83 m/year.Tree ring analyses also allow us to determine the impact of individual high discharges on the lateral migration rate of the Mała Panew channel. The lateral migration of the channel was most rapid in the years 1953–57 and 1966–68 as well as during the extraordinary flood in 1997. 相似文献
9.
塔河源荒漠河岸林群落物种组成、结构与植物区系特征 总被引:1,自引:0,他引:1
为了更好地了解荒漠河岸林植被动态与生物多样性维持机制,于塔里木河干流源头荒漠河岸林内建立6个1 hm 2样地,对群落物种组成、数量特征和空间格局等进行综合分析。结果表明,塔河源荒漠河岸林群落结构简单、物种多样性低,共有物种12科15属16种,杨柳科重要值最大(28. 97%),是群落优势建群科。取样面积在0. 04 hm 2时,包括了87. 5%的物种;样地内稀有种和偶见种均占所有物种的12. 5%。植物区系贫乏,单种科、属多,温带成分占绝对优势,古地中海成分也占有重要地位,具典型温带区系性质。样地内 DBH ≥ 1 cm 的活木本个体有2497株,灰胡杨多度占92. 95%,胸高断面积和重要值最大,在群落中占绝对优势地位。群落内科、属、种的数量随植株高度级的增加而减少,垂直结构层次分明,由乔木层、灌木层和草本层构成。样地内所有树种平均胸径15. 57 cm,径级与高度级结构均呈偏正态分布,缺乏高度≤ 2 m的个体,群落更新不良。优势种灰胡杨、胡杨径级结构均呈单峰型,其中胡杨幼树出现断层,灰胡杨幼苗向幼树发展过程中死亡率极高(92. 56%),均为衰退型种群。两个优势种空间格局呈聚集分布,不同生境下随径级增大空间分布格局变化不同;且两个优势种在空间上相互排斥而占据不同生境,暗示着种间竞争与生境异质性是影响荒漠河岸林物种空间分布格局和物种共存的重要因素。 相似文献
10.
为了更好地了解荒漠河岸林植被动态与生物多样性维持机制,于塔里木河干流源头荒漠河岸林内建立6个1 hm2样地,对群落物种组成、数量特征和空间格局等进行综合分析。结果表明,塔河源荒漠河岸林群落结构简单、物种多样性低,共有物种12科15属16种,杨柳科重要值最大(28.97%),是群落优势建群科。取样面积在0.04 hm2时,包括了87.5%的物种;样地内稀有种和偶见种均占所有物种的12.5%。植物区系贫乏,单种科、属多,温带成分占绝对优势,古地中海成分也占有重要地位,具典型温带区系性质。样地内DBH ≥ 1 cm的活木本个体有2497株,灰胡杨多度占92.95%,胸高断面积和重要值最大,在群落中占绝对优势地位。群落内科、属、种的数量随植株高度级的增加而减少,垂直结构层次分明,由乔木层、灌木层和草本层构成。样地内所有树种平均胸径15.57 cm,径级与高度级结构均呈偏正态分布,缺乏高度≤ 2 m的个体,群落更新不良。优势种灰胡杨、胡杨径级结构均呈单峰型,其中胡杨幼树出现断层,灰胡杨幼苗向幼树发展过程中死亡率极高(92.56%),均为衰退型种群。两个优势种空间格局呈聚集分布,不同生境下随径级增大空间分布格局变化不同;且两个优势种在空间上相互排斥而占据不同生境,暗示着种间竞争与生境异质性是影响荒漠河岸林物种空间分布格局和物种共存的重要因素。 相似文献
11.
Abstract. Variation in structural and compositional attributes of tropical savannas are described in relation to variation in annual rainfall and soil texture along a subcontinental-scale gradient of rainfall in the wet-dry tropics of the Northern Territory, Australia. Rainfall varies along the gradient from over 1500 mm p.a. in the Darwin region ( c . 12° S) to less than 500 mm in the Tennant Creek region ( c . 18° S). Soils are patchy, and sands, loams and clays may occur in all major districts within the region. We utilized a large data set (1657 quadrats ° 291 woody species; with numerous measured and derived sample variables) covering an area of 0.5 million km2 . Correlations between floristic composition of woody species and environmental variables were assessed using DCA ordination and vector fitting of environmental variables. Vectors of annual rainfall and soil texture were highly correlated with variation in species composition. Multiple regression analyses incorporating linear and quadratic components of mean annual rainfall and topsoil clay content were performed on three structural attributes (tree height, tree cover, tree basal area) and two compositional attributes (woody species richness, deciduous tree species richness). Tree height declined with decreasing rainfall; cover, basal area, woody species richness and deciduous species richness all declined with decreasing rainfall and increasing soil clay content. Regression models accounted for between 17% and 45% of the variation in the data sets. Variation in other factors such as soil depth, landscape position and recent land-use practices (for which there were no data on an individual quadrat basis) are likely to have contributed to the large residual variation in the data set. 相似文献
12.
Isotopic composition of nitrate-nitrogen as a marker of riparian and benthic denitrification at the scale of the whole Seine River system 总被引:14,自引:2,他引:12
Nitrogen budgets established for large river systems reveal that up to 60% of the nitrate exported from agricultural soils is eliminated, either when crossing riparian wetlands areas before even reaching surface waters, or within the rivers themselves through benthic denitrification. The study of nitrogen isotope ratios of riverine nitrates could offer an elegant means to assess the extent of denitrification and thus confirm these budgets, as it is known that denitrification results in a natural 15N enrichment of residual nitrates. The results reported here, for the Seine river system (France), demonstrate the feasibility of this isotopic approach at the scale of large watersheds. On the basis of in situ observations carried out in a large storage reservoir in the upstream Seine catchment (Der Lake), where intensive benthic denitrification occurs, as well as on the basis of laboratory experiments of denitrification under controlled conditions, it is shown that the isotopic discrimination associated with benthic denitrification is minimal ( of NO3-N ranging from –1.5 to –3.6), probably because the rate-limiting step of the process consists of nitrate diffusion through the water-sediment interface. Riparian denitrification on the contrary, when it implies nitrate reduction during convective transfer through reducing environements, causes a much more significant isotopic enrichment of 15N of residual nitrate ( about –18). The authors report measurements of nitrogen isotopic composition of nitrate from rivers of various stream orders in the Seine river system under summer conditions. Anomalies in the data with respect to the values expected from the mixture of the various sources of nitrate are here attributed to riparian denitrification. However, the authors show that because of the patchy distribution of actively denitrifying riparian zones within the drainage network, the isotopic signature conferred to residual nitrate in river water intrinsically provides only a minimum estimate of the extent of denitrification. 相似文献
13.
Questions: Boreal forests along small streams are bryophyte diversity hotspots because they are moist, productive and relatively high pH. Do these factors also explain the large differences in species richness and species composition found among streamside sites? Do the species of species‐poor sites represent nested subsets of the species of more species‐rich sites? How do the results apply to conservation? Location: Forests along small streams in mid‐boreal Sweden. Methods: Survey of the flora of liverworts and mosses and habitat properties, including calculation of a pH‐index based on species indicator values, in 37 sites (1000‐m2 plots). Results: The number of bryophyte species per plot ranged from 34 to 125. Neither soil moisture nor basal area of trees (a proxy for productivity) correlated significantly with species richness and composition, whereas pH‐index and cover of boulders did. Species richness and composition were more strongly correlated with pH‐index for mosses than for liverworts. The richness and composition of bryophyte species most frequently found on moist ground, stream channel margins and, most unexpected, woody debris were all more strongly associated with the pH‐index than with other habitat properties. Although species composition was significantly nested, there was still some turnover of species along the first ordination axis. Conclusions To attain high numbers of species, streamside forests need to have boulders and at least pockets with higher soil and stream‐water pH. The number of Red list species was weakly correlated with total species richness and the most species‐rich sites contained many species found more in non‐forest habitats. Hence, bryophyte conservation in streamside forests should not focus on species‐rich sites but on the quality and quantity of substrate available for assemblages of forest species that are strongly disfavoured by forestry. 相似文献
14.
The floristic composition, structure and dynamics of three primaryFagus japonica stands were investigated in the Chichibu Mountains.F. japonica was dominant [RD(%): 64.9–87.0] and showed a slightly inverse J-shaped DBH class distribution in the quadrats [No. of canopy
stems (H>20m): 87–138/ha]. The stems ofF. japonica for each size were distributed in the form of colonies, being scattered almost uniformly, and arranged in positive association
with each other. Detailed examination of the bases of the stem groups forming colonies revealed that most of them originated
from the bases of dead mother stems and that they were from common stools [No. of large stems (H>10 m) per stool: 6–11]. Among
six major canopy gaps observed, only one included stems sprouting from the outer part ofF. japonica stools, while all the others were occupied by individuals of species other thanF. japonica. After tree-fall, several undercanopyF. japonica stems remained. Thus canopy gaps in these forest stands recovered through the sprouting of remainingF. japonica stools or by new sprouting ofF. japonica individuals adjacent to the gaps. However, it was considered difficult to fill canopy gaps only with sprouts when the distance
between the center of a gap and that of a stool surpasses the crown vector. Such places that are not fully occupied by sprouts
will be filled by individuals of other canopy and/or under-canopy species. 相似文献
15.
Topo-community structure and dynamics were studied in mixed cool temperate forests, using the regeneration dynamics, to clarify
the maintenance mechanisms of community patterns along a microtopographic gradient. The 76 stands studied were classified
into two groups (i.e. convex slope and concave slope stands). The soil surface was more eroded on the concave slope than on
the convex slope, while water potential was not significantly different between topographies. On the convex slope, even-aged
patches alternated between young phase patches dominated by shade intolerant species, such asAcer rufinerve andBetula grossa, and mature phase patches, withTsuga sieboldii andFagus crenata. A slower lateral growth rate ofTsuga canopy trees and the absence of suppressed saplings in the mature phase may prolong the gap phase, which provides a favorable
situation to shade-intolerant species. On the concave slope, patch structure was less clear, and process of replacement of
canopy species by previously suppressed individuals of the same species was seen in the mature phase, which was mainly composed
ofF. crenata, Fagus japonica, Acer sieboldianum andStewartia pseudo-camellia. Gaps on the concave slope were formed frequently but were generally closed within 10 years by lateral growth of deciduous
canopy trees and by upgrowth of suppressed trees, and thus some individuals underwent recurrent periods of suppression until
they reached the canopy. We concluded that soil surface stability and gap encroachment pattern are critical to the maintenance
of the community pattern along a microtopographic gradient. 相似文献
16.
This contribution aims to improve our knowledge of the structural peculiarities of natural forest communities in southern Chile, paying special attention to leaf lifespan and morphology. Species are classified into 17 life-form categories. Using information contained in Braun-Blanquet relevés, the relative frequency of the life-form categories, based on quantitative importance such as cover degree (not mere species numbers), is calculated for 26 natural forests. Communities are categorized as belonging to six different types: (A) evergreen forests; (B) forests with mixed laurophyll-deciduous canopy; (C) forests with mixed canopy of sclerophyllous or small / needle-leaved evergreens and deciduous species (specifically C.1 with dwarf-shrub or grass field layer, and C.2 with laurophyll and mesophyll shrubs and a relatively sparse field layer); and (D) deciduous forests (specifically D.1 with laurophyll undergrowth, and D.2 with a herbaceous ground cover). In the gradient from warm and dry to cool and wet, the characteristic composition of the structural elements reflects climatic site properties, revealed by the distribution of the vegetation units. This gradient represents a gradual retreat of evergreen elements from top (upper tree layer) to bottom (undergrowth), which always follows the order from laurophyllous to sclerophyllous elements, and from small or needle-leaved to deciduous elements. Finally, this retreat terminates in the rare structural type characterized by purely herbaceous ground cover beneath a deciduous canopy. Shifts between structural types do not necessarily involve variation in species composition. These units, reacting rapidly even to slight changes in site conditions, seem to be especially well-suited to monitor changing climatic effects. Human impact on forests, resulting in community shifts towards vegetation of warmer and drier habitats, causes structural changes, as does natural disturbance. 相似文献
17.
Hisashi Sugita 《Ecological Research》1992,7(2):119-132
In the subalpine areas of the snowy regions of Japan (the Japan Sea side), there are some mountains with no or very small
stands ofAbies mariesii, although this species dominates the subalpine coniferous forests of the region. In order to discuss the cause and process
of this phenomenon, present horizontal and vertical ranges, as well as physiographic conditions, of theA. mariesii forest were examined in detail on the mountains in the Tohoku District. Sites in the subalpine zone were classified into
two types: ‘azonal sites’ which should be excluded from the habitat ofA. mariesii because of their edaphic or small-scale climatic properties, and ‘zonal sites’. Mountains with vast less-inclined zonal sites
generally had well developed stands ofA. mariesii forest. On the mountains with only small, solitary stands ofA. mariesii, the distribution was limited to flats or slightly inclined slopes at relatively low altitudes. These less-inclined zonal
sites were regarded as an important habitat for theA. mariesii forest in the Hypsithermal period and the extent of these sites controls the extent of the stands in that period and the
success of the subsequent range expansion of the forest. 相似文献
18.
The chlorination of river water in purification plants is known to produce carcinogens and genotoxins. The Yodo River system
was studied in regard to the trihalomethane formation potential (THMFP) and mutagen formation potential (MFP) by the chlorination
of river water and the discharge of sewage effluent. Overall, both THMFP and MFP are higher in the downstream region of the
Yodo River system than in the upstream Uji and Katsura River region, whereas the formation potentials are high in the upstream
part of the Kizu River. Detailed surveys were carried out on the Nabari River and other tributaries to the Kizu River. It
was revealed that the Nabari and the upper Kizu rivers contribute 49.9% and 41.9% of the THMFP and 47.9% and 44.7% of the
MFP pollution load to the main stream of the Kizu River, respectively. The contribution rates of the upper Kizu River could
be attributed to three rivers, the uppermost Kizu, Hattori, and Kume rivers, and household sewage waterways at 10.6%, 17.3%,
10.9%, and 3.1% for THMFP and at 9.5%, 17.3%, 12.5%, and 5.5% for MFP, respectively. The main cause of water pollution in
the upper reaches of the Kizu River may be attributable to both sewage effluent discharged directly into the Kume River and
the polluted water of the Tsuge and Yatani rivers, tributaries of the Hattori River. When we examined whether THMFP and MFP
depended on the concentrations of organic substances in water, both potentials highly correlated with chemical oxygen demand
(COD) in all water samples surveyed. The correlation coefficients between COD and THMFP and between COD and MFP were 0.957
(n = 76, P < 0.01) and 0.804 (n = 76, P < 0.01), respectively.
Received: November 29, 2000 / Accepted: July 3, 2001 相似文献
19.
Yosiaki Itô 《Ecological Research》1991,6(2):139-155
The development of ecology in Japan, especially after the Meiji Restoration (1868), is briefly reviewed. Pioneering studies
of Hiratsuka, on the calorimetric budget of a silkworm population, and Motomura, on the relation between numbers of species
and individuals in biotic communities, are noteworthy. A critical examination of his role in ecology in Japan reveals Kinji
Imanishi to have played pivotal roles in leading Japanese population ecologists to realize the importance of dispersal in
population regulation, and leading to the worldwide revival of field primatology. Although Imanishi's later (popular) writings,
in which he completely negated the role of competion and natural selection, have justifiably drawn much criticism, his earlier
critique of the competition-Almighty paradigms may be re-evaluated in the light of recent discussions on interspecific competition
and community equilibrium. 相似文献
20.
R. J. Flower P. G. Appleby J. R. Thompson M. H. Ahmed M. Ramdani L. Chouba N. Rose R. Rochester F. Ayache M. M. Kraiem N. Elkhiati S. El Kafrawy H. Yang E. K. Rasmussen 《Hydrobiologia》2009,622(1):85-112
Surface sediments and sediment cores were collected from coastal lagoons and lakes located in the Southern Mediterranean Region
(SMR) as part of the MELMARINA Project which involved integrated eco-hydrological monitoring and modelling. This study uses
surface sediments and sediment cores to infer spatial characteristics and temporal changes at the MELMARINA primary sites,
Merja Zerga in Morocco, Ghar El Melh in Tunisia and Lake Manzala in Egypt. In addition, surface sediment sampling was undertaken
at Egyptian Lake Bardawil and sediment cores were collected from the Lagune de Nador (Morocco). Sediment distribution patterns
are investigated using GIS with georeferenced sample locations to facilitate display and resurvey. Major variations in sedimentary
organic matter and, particularly, carbonate content, occur within and between sites. Local landscapes combined with hydrological
and biogeochemical processes influence the distributions of sediment bulk components (carbonates, organic material and clastic
matter) and molluscan shells and shell debris are an important source of sedimentary carbonate at all three primary sites.
Sediment cores were dated using natural (210Pb) and artificial (137Cs) radionuclides, and sediment accumulation rate changes indicate that sources of sediment supply varied markedly through
the twentieth century but have generally diminished after the mid-1960s. Sedimentary siliceous microfossils (diatoms) were
generally poorly preserved, but mollusc shell remains were well represented. Sediment chronologies and sediment bulk composition
allow discussion of some recent changes in bulk, minerogenic and biogenic sediment accumulation patterns in the SMR lagoons.
Sediment accumulation rates also varied between sites and multiple cores from Lake Manzala indicated that rates showed considerable
spatial variability. Low-level sediment contamination by fossil fuel combustion particulates and trace metals was demonstrated
for Ghar El Melh and Lagune de Nador where Pb and Zn accumulation rates were highest in twentieth century sediment. It is
emphasized that sediment quality and quantity have strong influences on lagoon ecosystem function and sedimentation is relevant
to hydromorphology and to concepts of ecological quality.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Guest editors: J. R. Thompson & R. J. Flower
Hydro-ecological Monitoring and Modelling of North African Coastal Lagoons 相似文献