秦岭山地天然次生林群落MRT数量分类、CCA排序及多样性垂直格局

采用多元回归树(MRT)对秦岭山地天然次生林群落进行数量分类,采用典范对应分析(CCA)进行排序,分析了秦岭山地天然次生林群落物种多样性沿海拔梯度的变化规律。结果表明:(1) 275个样方共有种子植物195种,隶属61科128属。乔、灌、草3个层次物种多样性变化沿海拔梯度的变化趋势基本一致,呈单峰模型;(2)经交叉验证认为秦岭山地天然次生林群落可分为2类,Ⅰ冬瓜杨(Populus purdomii)+陇东海棠(Malus kansuensis)+蛇莓(Duchesnea indica)群落,Ⅱ锐齿槲栎(Quercus aliena var. acuteserrata)+黄栌(Cotinus coggygria)+茜草(Rubia cordifolia)群落;(3) CCA排序结果揭示了群落生境的分布范围,反映出生态轴的排序意义,较好地反映秦岭山地天然次生林群落与环境因子的关系,其结果表明,海拔、坡向、凋落层厚度和干扰情况4个变量对该地区次生林群落的分布有较大的影响。     

Salinity, depth and the structure and composition of microbial mats in continental Antarctic lakes

1. Lakes and ponds in the Larsemann Hills and Bølingen Islands (East‐Antarctica) were characterised by cyanobacteria‐dominated, benthic microbial mats. A 56‐lake dataset representing the limnological diversity among the more than 150 lakes and ponds in the region was developed to identify and quantify the abiotic conditions associated with cyanobacterial and diatom communities. 2. Limnological diversity in the lakes of the Larsemann Hills and Bølingen Islands was associated primarily with conductivity and conductivity‐related variables (concentrations of major ions and alkalinity), and variation in lake morphometry (depth, catchment and lake area). Low concentrations of pigments, phosphate, nitrogen, DOC and TOC in the water column of most lakes suggest extremely low water column productivity and hence high water clarity, and may thus contribute to the ecological success of benthic microbial mats in this region. 3. Benthic communities consisted of prostrate and sometimes finely laminated mats, flake mats, epilithic and interstitial microbial mats. Mat physiognomy and carotenoid/chlorophyll ratios were strongly related to lake depth, but not to conductivity. 4. Morphological‐taxonomic analyses revealed the presence of 26 diatom morphospecies and 33 cyanobacterial morphotypes. Mats of shallow lakes (interstitial and flake mats) and those of deeper lakes (prostrate mats) were characterised by different dominant cyanobacterial morphotypes. No relationship was found between the distribution of these morphotypes and conductivity. In contrast, variation in diatom species composition was strongly related to both lake depth and conductivity. Shallow ponds were mainly characterised by aerial diatoms (e.g. Diadesmis cf. perpusilla and Hantzschia spp.). In deep lakes, communities were dominated by Psammothidium abundans and Stauroforma inermis. Lakes with conductivities higher than ±1.5 mS cm^?1 became susceptible to freezing out of salts and hence pronounced conductivity fluctuations. In these lakes P. abundans and S. inermis were replaced by Amphora veneta. Stomatocysts were important only in shallow freshwater lakes. 5. Ice cover influenced microbial mat structure and composition both directly by physical disturbance in shallow lakes and by influencing light availability in deeper lakes, as well as indirectly by generating conductivity increases and promoting the development of seasonal anoxia. 6. The relationships between diatom species composition and conductivity, and diatom species composition and depth, were statistically significant. Transfer functions based on these data can therefore be used in paleolimnological reconstruction to infer changes in the precipitation–evaporation balance in continental Antarctic lakes.     

Ecological features affect patterns of plant communities in Mediterranean temporary rock pools

In this paper, the results of a study on the ecology, floristic composition and spatial assemblages of temporary limestone rock pool plant communities of a central Mediterranean area (S Sicily, the Maltese Islands and Lampedusa) are presented. A total of 76 temporary pools were studied, distributed between the infra-mediterranean and thermo-mediterranean bioclimatic belt. For each temporary rock pools, the floristic composition and cover of the species were determined using standard relevé methods. Moreover, for 50 of these pools, pH, conductivity, soil depth, water-level, altitude and floristic richness and diversity index were assessed. The plant communities were analysed using unweighted pair group method using arithmetic averages and Euclidean distance classification and ordination methods such as canonical correspondence analysis (CCA). A total of four plant communities with specific floristic composition were established, each one with a different dominant species: Callitriche truncata; Elatine gussonei; Tillaea vaillantii and Lythrum hyssopifolia. According to the CCA, the spatial patterns of plant communities follow an ecological gradient related to water level and depth/size of the rock pools: these are the main ecological features affecting the distribution of the plant communities of rock pools. In addition, floristic richness and diversity index showed a slight increase in trend from temporary pools submerged for long periods towards pools submerged for short periods.     

Macroinvertebrates associated with two submerged macrophytes,Lagarosiphon ilicifolius and Vallisneria aethiopica,in the Sanyati Basin,Lake Kariba,Zimbabwe: effect of plant morphological complexity

Vallisneria aethiopica and Lagarosiphon ilicifolius are common and abundant submerged macrophytes in Lake Kariba, Zimbabwe. The two species have distinct structural morphologies, with Vallisneria consisting of long ribbon-like leaves, while Lagarosiphon has filiform stems with numerous small alternate leaves. This study investigated the effect of these architectural differences between the two plant species on their epiphytic macroinvertebrate assemblages in the shallow inshore waters of Lake Kariba. Ten sites were sampled on three occasions between May and July 2005. A total of 56 macroinvertebrate taxa was collected, 48 from Lagarosiphon and 45 from Vallisneria. Generally, the two plant species were associated with similar macroinvertebrate communities, but the average abundances of most taxa, and thus the overall macroinvertebrate abundances, were significantly greater on Lagarosiphon. The main macroinvertebrate functional feeding groups found on both plant species were collector-gatherers, grazers and predators, all of which were significantly more abundant on Lagarosiphon. Although the macroinvertebrate assemblages associated with Vallisneria and Lagarosiphon generally consisted of the same taxa, there were distinct and significant differences between them, probably due to the architectural differences between the two submerged macrophytes.     

Quantitative analysis of endangered Acanthopanax senticosus communities in Dongling Mountain of Beijing

Based on the survey of community plots, a quantitative analysis of endangered Acanthopanax senticosus communities in Dongling Mountain was performed with two way indicator species analysis (TWINSPAN), detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA). The communities of A. senticosus were classified into 9 types by TWINSPAN and the results were validated by DCA. On the DCA graph, the first axis reflected the gradient of altitude and the second axis reflected the aspect and slope. Most of A. senticosus were distributed in the thick forests at a high altitude with little light. With the exception of being a dominant species of shrub layers in a few communities, A. senticosus has a relatively scarce distribution. In accordance with DCA, the results of CCA also show the trend that the distribution of A. senticosus communities varied along with the gradient change of environmental factors. Altitude and light are the main factors affecting A. senticosus growth. __________ Translated from Chinese Journal of Ecology, 2007, 26(3): 314–318 [译自: 生态学杂志]     

Changes in phytoplankton community along a transversal section of the Lower Paraná floodplain,Argentina

Interactions between the main stream of large rivers and their floodplains are usually observed, determining gradual changes in environmental variables along a transversal axis. This paper studies the natural phytoplanktonic community, as well as the main physical and chemical properties from a transversal section of the Lower Paraná River floodplain, encompassing the main channel, a lake and a swamp. In vitro nutrient bioassays for phytoplankton growth were performed in order to evaluate the importance of nutrients as potential limiting factors. A decrease in depth, pH, dissolved oxygen, suspended solids, DIN (dissolved inorganic N), particularly nitrates, and DIN:SRP (soluble reactive P) ratio, was observed from the main channel towards the swamp; as well as an increase in transparency, chlorophyll-a and phytoplankton density. Phytoplankton from the mainstream consisted mostly of typical potamoplanktonic species adapted to grow in turbid environments (mainly Aulacoseira granulata (Müll.) Sim. and its varieties), while in the swamp it was composed mainly of mixotrophic phytoflagellates (euglenoids and cryptomonads), facultative N-heterotrophic diatoms and small-size green algae. Values of both abiotic and biotic variables measured in the lake were always intermediate between the former ones, although closer to those of the river, an account of their permanent connection. Phytoplankton response to N-addition was more frequent in the swamp bioassays than in the other two sites. However, a great increase in algal density in the control flasks, suggests a plentiful source of N at the beginning of the experiments. Light scarcity is more likely to occur than N-limitation in both river and lake due to their low transparency and a high DIN concentration. Although N-limitation may be expected in the swamp, the growth in the controls in spite of the low initial DIN concentration, suggests the existence of an N-supply other than DIN (perhaps organic N). Rather than indicate in situ N-limitation, present results seem, therefore, to suggest that phytoplankton of the swamp mainly composed of mixotrophic algae would be adapted to grow under low DIN concentrations. Possible reasons for the absence of N₂-fixing Cyanobacteria in this environment are discussed.     

Clear,crashing, turbid and back – long‐term changes in macrophyte assemblages in a shallow lake

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Homogenization of fish assemblages in different lake depth strata at local and regional scales

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Within‐lake distribution patterns of fish assemblages: the relative roles of spatial,temporal and random environmental factors in assessing fish assemblages using gillnets in a large and shallow temperate lake

In this study, the relative role of spatio‐temporal factors and associated environmental variables (water transparency and temperature) were quantified in relation to gillnet samples of fishes in a large and shallow lake (Lake Balaton, Hungary). Most of the variance (56·1%) in the relative abundance data (%) was related to the vertical segregation of fishes. This gradient substantially affected the catch per unit effort (CPUE) by number of the dominant species, the surface‐oriented bleak Alburnus alburnus and the benthic common bream Abramis brama. It also influenced total CPUE, mean fish mass and species richness and diversity. At the lake level, horizontal habitat heterogeneity (i.e. littoral v. offshore) accounted for only 8·3% of the total variance in relative abundance data, but was important in structuring the CPUE of the ruffe Gymnocephalus cernua and the pikeperch Sander lucioperca. The longitudinal environmental gradient (i.e. lake basin), year and season of sampling, water transparency and temperature had significant effects on relative abundance only at the habitat level, but were also important components of variability of CPUE in some species at the lake level. As sampling schemes need to consider the main gradients in fish assemblage distributions, the use of surface and pelagic gillnets should be more intensively incorporated in the study and monitoring of fish assemblages in shallow lakes and lake habitats.     

Rotifer community structure in three shallow lakes: seasonal fluctuations and explanatory factors

The present work aimed at studying the rotifer communities of three shallow eutrophic lakes in Portugal (lakes Mira, Vela and Linhos). At the time of the study, Mira and Vela faced large inputs of allochthonous nutrients, while Linhos was facing terrestrialisation, with cycles of dominance-senescence of macrophytes. The three lakes differed in terms of their abiotic features, with Linhos presenting very high nutrient levels and low pH, while Vela and Mira shared most of the characteristics. The rotifer communities of these two lakes were poorly diversified but highly abundant (max. > 2000 ind l⁻¹), with a clear dominance of eurytopic euplanktonic species (mainly Keratella cochlearis). On the other hand, Linhos presented lower abundances (<1000 ind l⁻¹) but higher species richness, mainly due to macrophyte-associated taxa, such as the littoral genera Lepadella, Testudinella and Squatinella. In all lakes, summertime represented a peak in terms of abundance and diversity. Canonical correspondence analysis (CCA) identified two main environmental gradients that shape up the rotifer assemblages: a temporal gradient, mainly related to temperature, and a eutrophy gradient, associated with nitrogenous nutrients. The latter gradient is clearly dependent on between-lake variation, due to the high nutrient levels observed in lake Linhos. Variance partitioning using CCA revealed that the largest portion (27.5%) of the total variation explained (52.1%) was attributed to the interaction between lake and environmental variables.     

Macrozoobenthos of two Antarctic glacial coves: a comparison with non-disturbed bottom areas

There are only few studies on shallow Antarctic benthic communities associated with habitats affected by intense mineral sedimentation inflow. The analysis of macrofaunal communities associated with two shallow, isolated glacial coves was performed in Admiralty Bay (King George Island) and compared with non-disturbed sites. Multivariate analyses (hierarchical classification, nMDS) clearly separated glacial cove communities (two assemblages) from the sites situated outside both basins (two assemblages). The community influenced by the streamflow of glacial discharge of meltwater situated in the area with sandy–clay–silt sediments had a very low species richness, diversity and abundance. It was dominated by eurytopic, motile deposit feeding polychaetes such as Mesospio moorei, Tharyx cincinnatus and Leitoscoloplos kerguelensis as well as the bivalve Yoldia eightsi. The second glacial community of the area located at a grater distance from the outlet of the stream was characterized by sandy–clay–silt and clay–silt deposits and showed also a low diversity and species richness. The most abundant here were peracarid crustaceans, with the dominant opportunistic feeder Cheirimedon femoratus. Community from the non-disturbed area with silty–clay–sand, and silty–sand sediments had higher species richness and diversity. The assemblage of fauna from the sandy bottom has values of those two indexes similar to those found in the disturbed areas.     

Lake depth and geographical position modify lake fish assemblages of the European 'Central Plains' ecoregion

1. Classification of European lake fish assemblages can be based on fish‐assemblage structure or morphological, geographical, physical and chemical lake attributes. However, substantial gaps in knowledge exist with respect to the correspondence between both classification approaches. 2. Here, we compiled fish assemblage data from 165 lakes situated in the European ‘Central Plains’ ecoregion. Cluster analysis of fish abundances was performed to compare fish assemblage types of the entire ecoregion with those from previous country‐specific studies. Nonparametric group comparisons, classification trees and partial canonical ordinations were used to infer the correspondence between fish assemblage types and morphology, geographical position and nutrient concentration of the lakes. 3. Three distinct fish assemblages were revealed: vendace (Coregonus albula), ruffe (Gymnocephalus cernuus) and roach (Rutilus rutilus) lake types. Both latitude and lake depth were the best determinants of lake type, but total phosphorus (TP) concentrations were also important. Vendace lakes were deep and had low TP concentrations, whereas the shallower ruffe and roach lakes had higher TP values. Roach lakes were more frequent in the north‐west area of the ecoregion, whereas ruffe lakes were more often found south of the Baltic Sea. 4. Controlling for the influence of nutrient concentration showed that lake morphology and geographical position were important determinants of fish assemblages. However, the variance explained was low (<20%), implying that biological interactions may also be important in forming the lake‐specific fish assemblages. 5. The results suggest that fish assemblages differ between deep and shallow lakes, and between the north‐west and south‐east locations within the Central Plains ecoregion. Accordingly, establishment of depth‐related lake morphotypes is needed, and the European ecoregions recommended to be used in evaluation systems according to the Water Framework Directive seem to be too coarse to reflect the subtle differences of fish species richness along geographical gradients.     

Composition of bryozoan assemblages related to depth in Svalbard fjords and sounds

Svalbard bryozoan communities were investigated along a depth range from the surface to 296 m between the inner glacial fronts and fjord mouths during 2001 and 2002. The main study area was Kongsfjorden (79°N, 12°E). A total of 137 taxa of bryozoans were identified: 108 to species, 24 to genus, 3 to family, 1 to order and 1 to phylum level. Cluster and multidimensional scaling analyses revealed four distinct assemblages of bryozoans: shallow (0–40 m; 68 taxa), deep (40–296 m; 80 taxa), inner fjordic (three taxa) and an assemblage found on small stones in shallow waters (nine taxa). The inner fjordic assemblage was recorded from the front of tidal glaciers extending about 10 km out into the fjord. In terms of abundance, Celleporella hyalina Linnaeus dominated in shallow areas (18%), Hippothoa arctica Kluge (55%) in deep water, Alcyonidium disciforme Smitt (86%) proximate to glaciers fronts and Electra arctica Borg on small stones (98%). The species were classified according to their depth range as a stenobathic-shallow (46 taxa), stenobathic-deep (57 taxa) and eurybathic-generalist (21 taxa). Mean diversity measures did not show any significant differences between the shallow and deep communities. The bryozoan assemblages seem to be structured primarily by processes related to depth and sediment characteristics.     

Colonization and succession of submerged macrophytes in shallow Lake Væng during the first five years following fish manipulation

Colonization of submerged macrophytes and changes in species composition were studied in shallow Lake Væng during the first five years (1987–91) following fish manipulation in 1986–1988 and a resultant significant improvement in lake water transparency. No submerged macrophytes were present in the lake from 1981–1986, during which time the summer mean Secchi depth ranged from 0.6 and 0.8 m. From 1987 to 1990, Secchi depth increased from 0.9 m to 1.8 m and macrophyte coverage consequently increased (1 % of the lake area in 1987, 2% in 1988, 50% in 1989, 80% in 1990 and 90% in 1991). At the same time, the macrophytes became taller, and the weedbeds more dense. The macrophytes colonized from the exposed and deeper part of the lake towards the sheltered and more shallow part of the lake, a colonization pattern that was confirmed by transplantation experiments. The delay in colonization of the shallow parts may be caused by waterfowl grazing. The vegetation was initially dominated by Potamogeton crispus L., but there was a gradual change during 1988–1989 and Elodea canadensis Michx became exclusively dominant in 1990–1991.     

Ecological sensitivity of marl lakes to nutrient enrichment: evidence from Hawes Water,UK

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Primary production of epipsammic algal communities in Lake Balaton (Hungary)

Benthic algal communities can play an important role in matter and energy flux of shallow lakes. Their contribution to total primary production of lakes has been largely unexplored. The aim of this study was to estimate the primary production of the epipsammic algal communities at different water depths in Lake Balaton (Hungary) with photosynthetic measurements performed in laboratory. The photosynthesis of the benthic algae of different origin was studied at nine different irradiance levels, in three replicates. The maximum photosynthetic rate (P _max) was always higher in samples from the shallow parts than those from the deeper regions of the lake. Along the west–east longitudinal axis of the lake P _max decreased in the southern part and increased in the middle of the lake as a consequence of differences in the chlorophyll-a concentrations. Knowing P _max, I _k, global radiation and extinction coefficient, the primary production (mg C m⁻² day⁻¹) of the epipsammic algal community was calculated at different water depths. In the shallow regions at 0.5 and 1 m water depth 75–95% and 60–85% of the production was attributable to the epipsammon. The percentage contribution of epipsammon was at 2 m water depth 20–65%. In the deeper pelagic region (>3 m) more than 85% of the primary production originated from the phytoplankton.     

Responses of the fish community to the flood pulse and siltation in a floodplain lake of the Trombetas River,Brazil

The distributions of the fish species were examined in relation to environmental variables, to evaluate the effects of environmental degradation on the fish community of Batata Lake, a typical Amazonian clearwater lake. From 1979 to 1989, tailings composed of water and clay, extracted from bauxite by water jets, were discharged into Batata Lake. The tailings spread into about 30% of the lake’s area, where the level of the lake bottom rose and turbidity increased. In the present study, multivariate analyses were performed on data for environmental parameters and fish density and biomass. Fish were collected with gillnets during the annual hydrological cycle (filling, flood, drawdown and dry periods), in the silted area, the partly silted area (intermediate) and the natural area. Values of the Shannon index, density and biomass were compared among areas and periods to evaluate the effects of the tailings on community structure. Sediment resuspension, which reduces transparency, is accentuated in shallow water, and was the main factor regulating differences in the community structure between the natural and silted areas. The decrease in transparency occurs mainly during the filling period in the silted area and during the low-water period in the silted and intermediate areas, when sediment resuspension increases concentrations of nutrients and chlorophyll-a. The strong influence of migratory and piscivore species in low-transparency waters is likely associated with the greater bacterioplankton productivity and turnover rate observed by other authors in the silted area, increasing the importance of the heterotrophic food chain in Batata Lake. Reduction of transparency in the silted area was a selective factor for fish species. The death of part of the flooded forest vegetation was decisive in lowering densities of the igapó-associated species in the silted area. The unconsolidated substrate, the death of part of the igapó forest and the negative effects of low transparency – inhibiting resident visually oriented species in the affected areas – are the main factors causing the low diversity in the silted area as a whole. The correlations between CPUEs, conductivity and nutrients and chlorophyll-a concentrations do not appear to reflect cause–effect relationships, indicating that these environmental parameters are poor predictors of fish density in Batata Lake.     

Beta diversity of cold-water coral reef communities off western Scotland

Spatial heterogeneity in coral reef communities is well documented. This “species turnover” (beta diversity) on shallow warm-water reefs strongly conforms to spatial gradients in the environment as well as spatially autocorrelated biotic processes such as dispersal and competition. But the extent to which the environment and spatial autocorrelation create beta diversity on deep cold-water coral reefs such as those formed by Lophelia pertusa (Scleractinia) is unknown. The effects of remotely sensed and ground-truthed data were tested on the community composition of sessile suspension-feeding communities from the Mingulay Reef Complex, a landscape of inshore Lophelia reefs off the Scottish west coast. Canonical correspondence analysis determined that a statistically significant proportion (68%) of the variance in community composition could be explained by remotely sensed environmental variables (northerly and easterly aspect, seabed rugosity, depth), ground-truthed environmental variables (species richness and reef macrohabitat) and geospatial location. This variation was further partitioned into fractions explained by pure effects of the environment (51%), spatially structured environmental variables (12%) and spatial autocorrelation (5%). Beta diversity in these communities reflected the effects of both measured and unmeasured and spatially dependent environmental variables that vary across the reef complex, i.e., hydrography. Future work will quantify the significance and relative contributions of these variables in creating beta diversity in these rich communities.     

New Zealand Demersal Fish Assemblages

Demersal fish assemblages in the New Zealand Exclusive Economic Zone were identified using presence–absence data from 19215 bottom trawl tows made over a 37-year period. The dataset spanned latitudes 34–54°S and depths of 4–1500m. A total of 123 taxa occurred in more than 1% of the tows (121 fish and 2 squid). Multivariate ordination and classification (correspondence analysis and Ward's cluster analysis) identified four primary species assemblages that were associated with the inner continental shelf, mid–outer continental shelf and shelf edge, upper continental slope and mid continental slope. The most frequently occurring species (> 40% of tows) in each assemblage were (in descending order): inshore – Chelidonichthys kumu, Pagrus auratus and Zeus faber; shelf – Nototodarus spp., Squalus acanthias and Thyrsites atun; upper slope – Macruronus novaezelandiae, Lepidorhynchus denticulatus, Genypterus blacodes and Hydrolagus sp.; mid slope – Hoplostethus atlanticus, Etmopterus baxteri, Halargyreus johnsonii, Coryphaenoides subserrulatus, Deania calcea, Coryphaenoides serrulatus, Pseudocyttus maculatus, Mora moro, Diastobranchus capensis and Centroscymnus crepidater. Further species associations were also identified within each primary assemblage. Canonical correspondence analysis revealed that most of the explainable variation in species composition was associated with depth and latitude; longitude and season explained little extra variance. The usefulness of our results is limited by the use of presence–absence rather than abundance data, and by the uneven spatial distribution of trawl tows. However, the present study provides a large-scale framework within which to interpret the results of studies using abundance data over smaller spatial and temporal scales.     

Submerged macrophytes as indicators of the ecological quality of lakes

1. We analysed submerged macrophyte communities from 300 Danish lakes to determine the efficacy of different species, maximum colonisation depth (C_max) of plants as well as coverage and plant volume inhabited (PVI) as indicators of eutrophication. 2. Most species occurred at a wide range of phosphorus and chlorophyll a (Chla) concentrations, but some species of isoetids (Lobelia, Isoëtes) and Potamogeton (Potamogeton gramineus, Potamogeton alpinus and Potamogeton filiformis) were mainly found at low nutrient concentrations and hence may be considered as indicators of nutrient poor conditions. However, species typically found in nutrient‐rich conditions, such as Elodea canadensis and Potamogeton pectinatus, were also found at total phosphorus (TP) <0.02 mg P L^?1 and Chla <5 μg L^?1 and therefore cannot be considered as reliable indicators of eutrophic conditions. 3. Submerged macrophyte coverage, PVI and the C_max were negatively correlated with TP and Chla. However, variability among lakes was high and no clear thresholds were observed. At TP between 0.03 and 0.07 mg P L^?1 plant coverage in shallow lakes ranged from nearly 0 to 100%, whilst at concentrations between 0.10 and 0.20 mg P L^?1 only 29% of the lakes had coverage >10%. C_max was found to be a useful indicator only in deep lakes with unvegetated areas in the deeper part, whereas the use of coverage was restricted to shallow lakes or shallow areas of deep lakes. 4. Overall, submerged macrophytes responded clearly to eutrophication, but the metrics investigated here showed no well‐defined thresholds. We developed a simple index based on species richness, presence of indicator species, coverage and C_max, which might be used to track major changes in macrophyte communities and for lake classification.