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1.
Matina Katsiapi Antonios D. Mazaris Evangelia Charalampous Maria Moustaka-Gouni 《Hydrobiologia》2012,698(1):121-131
The potential importance of watershed land use types, lake/watershed morphometry/topography and geographic distance as drivers of phytoplankton community composition was evaluated by using data collected from 18 freshwaters (lakes and reservoirs) distributed around Greece. In all freshwaters, phytoplankton species composition showed a strong correlation with the composition of land uses within their watersheds but no correlation with morphometry/topography and geographic distance. Cyanobacteria were found to be associated with artificial and agricultural land use types. Chrysophytes were closely associated to forested areas whereas euglenophytes to industrial, commercial, and transport units. Phytoplankton total biomass was significantly higher in freshwaters with a cover of agricultural and artificial land use >30% in their watersheds. This rather low threshold of agricultural and artificial land use cover might be indicative of the higher sensitivity of Mediterranean freshwaters to eutrophication process. Analysis performed separately for lakes and reservoirs revealed some diverse patterns with lake morphometric/topographic variables significantly affecting similarity in species occurrence. The results demonstrate that land use types reflecting anthropogenic pressures could act as critical drivers explaining phytoplankton structure. Our research suggests that Mediterranean freshwaters could be highly sensitive to land use types within their watersheds, thus landscape structure and configuration should be taken into account toward effective conservation and management plans. 相似文献
2.
Community analysis of Belarusian lakes: relationship of species diversity to morphology, hydrology and land use 总被引:1,自引:0,他引:1
Karatayev Alexander Y.; Burlakova Lyubov E.; Dodson Stanley I. 《Journal of plankton research》2005,27(10):1045-1053
In the glacial lake district of northern Belarus, limnologistscollected extensive biological, chemical and physical data on550 lakes (51% of all Belarusian glacial lakes). This largedata set provided a unique opportunity to examine subtle relationshipswith great statistical power. Our purpose was to use multivariateand correlation analyses to explore relationships of speciesrichness with morphological and hydrological parameters. A multivariateanalysis of the environmental data suggests that the Belarusianlakes can be separated along gradients of size, hydraulic residencetime and watershed development (land use). In most instances,species richness for major planktonic and benthic groups wascorrelated significantly with lake size and land use. Speciesrichness values were correlated less with watershed size orhydraulic residence time. In each community, there was a groupof species characterized by higher correlations with principalcomponent analysis (PCA) axes. These groups are as follows:for phytoplanktondiatoms, for zooplanktonrotifers,and for zoobenthosmolluscs. For lakes both in pristineand developed watersheds, we found small but significant negativespeciesarea correlations for littoral crustaceans. Asurvey of the relevant literature shows scale dependence forthe correlation between species richness and lake size. Forpelagic crustaceans, the speciesarea correlation wassignificant (and positive) for lakes with developed watershedsbut not for pristine watersheds. 相似文献
3.
Stormwater ponds are increasingly common aquatic habitats whose biotic communities are largely unexplored. As anthropogenic
development continues to alter the landscape, watershed land use is gaining recognition for its potential to predict species
compositions in aquatic systems. This study reports species composition of five aquatic hemipteran families (Notonectidae,
Corixidae, Belostomatidae, Nepidae, Pleidae) in 28 permanent, artificial stormwater ponds in watersheds with different land
covers and associated contaminant input. We hypothesized that land cover variables would be significant drivers of aquatic
hemipteran community structure in ponds, and that ponds with a high percentage of agricultural and lawn cover in the watershed
would be characterized by the absence of species intolerant of the chemical, physical, and ultimately biotic changes associated
with these watersheds. Non-metric multi-dimensional scaling (NMS) was used to identify dominant gradients of species composition
and environmental variables. Pond morphology variables, watershed lawn, watershed agriculture, and predatory fish abundance
were each found to have statistically significant correlations with hemipteran community structure. The abundance of Notonecta undulata, the species responsible for creating the largest (ranked) distance in species structure among ponds, was positively correlated
with shallow, fishless ponds and independent of land use variables. The abundances of four species of corixids were negatively
correlated with watershed agriculture, and hemipteran richness was positively correlated with watershed lawn and negatively
correlated with pond surface area. Heirarchical cluster analysis revealed non-random hemipteran species assemblages in which
congeneric corixid species tended to co-occur, contradicting traditional niche theory. Since artificial stormwater ponds are
chemically different from natural-pond habitat and rapidly increasing in number, knowledge of which insect species are capable
of thriving in this environment and their relationship to land use in the watershed is of both environmental and evolutionary
interest.
Handling editor: D. Dudgeon 相似文献
4.
Nutrient loading to lakes depends on both the availability of nutrients in a watershed and their potential for movement to
a lake. Many studies have demonstrated that variation in watershed land use can translate to differences in lake water quality
by affecting nutrient availability. There have been few attempts, however, to understand how loading to surface waters is
affected by land use when there are differences in watershed transport capacity. We compared the relationship between land
use/cover and lake nutrients in lakes draining watersheds that exhibited high and low transport capacity using a 5 year (2001–2005)
dataset describing the chemistry of 101 lakes and reservoirs in a region of intensive agriculture. We measured watershed transport
capacity by compositing the hydrologic, geologic, and topographic variables correlated with interannual variability in lake
total nitrogen (TN) or phosphorus (TP) because the hydrologic permeability of watersheds amplifies downstream responses to
rainfall events. Factors describing watershed transport capacity differed for TN and TP, consistent with differences in nutrient
mobility and biogeochemistry. Partial least squares regression revealed that watershed transport capacity influenced the nature
of the association between land use/cover and lake chemistry. In watersheds with low transport capacity, in-lake processes
and near-shore land use/cover tended to be more influential, whereas, in watersheds with high transport capacity, land use/cover
across the entire watershed was important for explaining lake chemistry. Thus, although land use is a key driver of nutrient
loading to lakes, the extent to which it influences water quality can vary with watershed transport capacity.
JMF conceived the study and analyzed the data. JAD collected the data. JMF and JAD wrote the paper. 相似文献
5.
Robert A. Zampella John F. Bunnell Kim J. Laidig Nicholas A. Procopio 《Ecological Indicators》2010,10(2):303-310
The establishment of introduced species in aquatic and wetland habitats is often associated with human-related environmental degradation. In the blackwater streams of the New Jersey Pinelands, the presence of nonnative species drives the relationship between community composition and watershed disturbance associated with developed land and upland agriculture. Most Pinelands lakes are shallow, artificial stream impoundments. In this study, we determined if land-use gradients or thresholds were associated with the presence of nonnative-herbaceous-plant, woody-plant, fish, and anuran species in 30 Pinelands stream impoundments. Correlation and regression analyses indicated that the response of all four taxonomic groups to watershed disturbance was an increase in the number of nonnative species and the proportion of total species richness represented by nonnative species. Native-anuran richness decreased along the watershed-disturbance gradient. We found both linear and nonlinear responses when relating species-richness attributes to the percentage of altered land (combined percentage of upland agriculture and developed land) in the associated watersheds, but the nonlinear responses cannot be considered land-use-related degradation-threshold responses. The breaks in the regression lines describing the relationship between the percentage of total species richness represented by nonnative plants and fish and altered land in our Pinelands watersheds did not represent a degradation threshold because, with the exception of the percentage of total species richness represented by nonnative-anuran species, a progressive decline in aquatic integrity was observed before the break points. Kruskal–Wallis ANOVA revealed significant differences in species-richness attributes only among stream impoundments with contrasting altered-land profiles, providing further evidence that aquatic degradation was progressive. Logistic regression identified the point along the watershed-disturbance gradient at which the probability of encountering nonnative bullfrogs was greater than that for native carpenter frogs. 相似文献
6.
Scott J. Van Egeren Stanley I. Dodson Byron Torke Jeffrey T. Maxted 《Hydrobiologia》2011,668(1):137-146
Zooplankton community composition can be related to natural environmental factors such as lake morphology, lake landscape
position, and water chemistry as well as anthropogenic factors such as agricultural and urban land-use. We hypothesized that
within-lake factors, such as water chemistry, lake morphology, and human land-use would each be related to zooplankton community
structure, but that watershed land-use would be the strongest correlate in southeast Wisconsin lakes. Zooplankton samples,
collected every 3 months over a year, from 29 lakes were used to determine how lake and watershed morphology, water quality,
and land-use were related to zooplankton community structure in the heavily developed Southeast Wisconsin Till Plain Ecoregion.
Forward selection and a variation partitioning procedure were used to determine relative and shared contributions of each
suite of variables in predicting zooplankton community structure. Redundancy analysis was used to characterize dominant gradients
in pelagic zooplankton communities and related environmental factors and land-use. The major correlates of community structure
included summer phosphorus, lake depth and surface area and urban and natural land. Variation partitioning illustrated that
phosphorus alone accounts for the greatest part (12%) of community structure. Urban land-uses (residential, commercial and
paved land) and lake morphology partially explain zooplankton community variation through combined effects with phosphorus.
Small cladocerans and Skistodiaptomus pallidus were associated with higher phosphorus, shallow depth and higher urban land-use, while Daphnia pulicaria dominates in deep lakes with lower phosphorus and less urban land-use. This study contributes to the understanding of factors
affecting zooplankton community structure in a largely human developed region and illustrates the importance of eutrophication
in structuring zooplankton community composition. 相似文献
7.
Dodson Stanley I.; Newman Amy L.; Will-Wolf Susan; Alexander Mara L.; Woodford Michele P.; Van Egeren Scott 《Journal of plankton research》2009,31(1):93-100
Zooplankton community structure can be affected by within-lakeand by watershed ecological factors, including water chemistry(related to landscape position), lake morphology and human activityin the watershed. We hypothesized that all three groups of driverswould be correlated with zooplankton species richness and speciescomposition for lakes in northern Wisconsin. Data collectedfrom 52 lakes allowed us to explore the relationship of zooplanktoncommunity structure with ecological drivers. We found that crustaceanzooplankton species richness was not significantly correlatedwith independent environmental variables derived from PCA ordination,nor with measures of community structure based on NMS ordination.However, species composition was correlated with environmentalgradients. Larger zooplankton species (Daphnia pulicaria, Epischuralacustris, Skistodiaptomus oregonensis, Mesocyclops americanus)occurred in large and deep lakes low in the landscape gradient,whereas the smaller species Ceriodaphnia dubia, Daphnia retrocurvaand Leptodiaptomus minutus tended to occur high in the landscape.This shift in species composition was correlated with increasedconductivity, primary productivity and the hypolimnetic refugescharacteristic of larger deeper lakes lower in the landscape.Riparian housing development and littoral zone habitat (measuredas building density and by abundance of logs in littoral zones)were not correlated with zooplankton community structure. Inthese relatively low-impact lakes, natural drivers are stillthe most significant determinants of zooplankton community structure. 相似文献
8.
An important environmental factor determining both phytoplankton and zooplankton community composition is lake depth and
thermal stratification. However, there is little information on how the interaction between zooplankton grazers and their
phytoplankton food changes along an environmental gradient of lake depth. We contrasted resource availability for daphniid
zooplankton populations living in two shallow, unstratified lakes and in two deep, stratified lakes using a novel growth bioassay.
Stratified lakes had consistently lower resource richness than shallow unstratified lakes. To test whether resources were
important in explaining differences in daphniid composition of shallow and deep lakes, we performed reciprocal transplant
experiments. We raised daphniids typical of shallow (Ceriodaphnia reticulata) and deep (Daphnia dentifera) lakes in the resources from replicate shallow and deep lakes and monitored survival and reproduction. The two species exhibited
a performance trade-off, measured by life table r and R
0, across a gradient in natural resource richness. D. dentifera had higher relative fitness than C. reticulata when raised in the poorest resource environment from a deep lake. However, under richer resource conditions typical of shallow
lakes, C. reticulata outperformed D. dentifera. We further created a gradient in natural resource quantity (by dilution) to test whether this trade-off in species relative
fitness involved aspects of resource quality. No trade-off in species performance was evident across the dilution gradient,
indicating that resource quality was important to the trade-off. We conclude that shifts in daphniid species composition along
a gradient of lake depth involve an adaptive trade-off in ability to exploit rich versus poor resource quality.
Received: 11 May 1998 / Accepted: 15 January 1999 相似文献
9.
A. V. Krylov 《Inland Water Biology》2020,13(1):41-50
The article describes quantitative and structural characteristics of zooplankton of polytypic sites of a water system including a lake, canal, and a water reservoir. It is shown that in the littoral zone of lakes and water reservoirs, the number of species and communities is higher, and biomass, lower. However, in the littoral zone of shallow lake zooplankton in number, took priority due to Rotifera, in the deep part of the water body – Rotifera and Cladocera; in the center of the lake zooplankton dominated by biomass due to Cladocera and Copepoda, in the water reservoir—due to the Copepoda. The dam area of the water reservoir had the highest species richness of zooplankton among all studied sites. The greatest number and biomass of zooplankton within a waterbody are noted in upper part, where a sedimentation zone had formed, and as a whole for the system of the investigated waterbodies, the maximum quantity indices are typical of lake communities. It is revealed that the starkest interannual changes in zooplankton were observed in the shallow lake: the number of species decreased—in the littoral zone at the expense of Rotifera, and in the center, the biomass increased at the expense of Cladocera; in deep-water area of the dam area of the reservoir, conversely, the number of species, as well as the number and biomass of the community, increased due to Copepoda. 相似文献
10.
Elisabeth Jensen Sandra Brucet Mariana Meerhoff Louise Nathansen Erik Jeppesen 《Hydrobiologia》2010,646(1):215-229
Diel horizontal migration (DHM), where zooplankton moves towards macrophytes during daytime to avoid planktivorous fish, has
been reported as a common migration pattern of zooplankton in shallow temperate freshwater lakes. However, in shallow eutrophic
brackish lakes, macrophytes seem not to have the same refuge effect, as these lakes may remain turbid even at relatively high
macrophyte abundances. To investigate the extent to which macrophytes serve as a refuge for zooplankton at different salinities,
we introduced artificial plants mimicking submerged macrophytes in the littoral zone of four shallow lakes, with salinities
ranging from almost freshwater (0.3) to oligohaline waters (3.8). Furthermore, we examined the effects of different salinities
on the community structure. Diel samples of zooplankton were taken from artificial plants, from areas where macrophytes had
been removed (intermediate areas) and, in two of the lakes, also in open water. Fish and macroinvertebrates were sampled amongst
the artificial plants and in intermediate areas to investigate their influence on zooplankton migration. Our results indicated
that diel vertical migration (DVM) was the most frequent migration pattern of zooplankton groups, suggesting that submerged
macrophytes were a poor refuge against predation at all salinities under study. Presumably, this pattern was the result of
the relatively high densities of small planktivorous fish and macroinvertebrate predators within the submerged plants. In
addition, we found major differences in the composition of zooplankton, fish and macroinvertebrate communities at the different
salinities and species richness and diversity of zooplankton decreased with increasing salinity. At low salinities both planktonic/free-swimming
and benthic/plant-associated cladocerans occurred, whilst only benthic ones occurred at the highest salinity. The low zooplankton
biomass and overall smaller-bodied zooplankton specimens may result in a lower grazing capacity on phytoplankton, and enhance
the turbid state in nutrient rich shallow brackish lakes. 相似文献
11.
湖北四湖流域景观结构变化对汛期湖泊水位影响的模拟分析 总被引:1,自引:0,他引:1
借助于水文学对不同下垫面状态的产流模式研究的成果,建立了计算四湖流域两个调蓄湖泊汛期洪峰水位的模型。模拟分析的结果表明,在4种同样的降雨条件下,景观结构变化使长湖汛期日水位平均增加0.0831—1.3223m,最大增加0.1579—1.8583m,使洪湖汛期日水位平均增加1.0810一2.3008m,最大增加1.4101—2.4864m。证明景观结构变化是引起洪涝灾害加剧的重要原因且景观结构变化对湖泊洪峰水位的影响存在一种累加效应。景观结构的调整也是控制洪涝灾害的重要途径。 相似文献
12.
《Acta Oecologica》2002,23(3):155-163
Frequent dispersal events are expected to elevate local species richness in island-like habitats such as lakes. However, the importance of dispersal can be hard to evaluate if other factors cause large background variability in species composition and richness. In this paper, we review empirical studies on ecological factors known or expected to influence species richness in zooplankton communities of inland lakes. We then present summaries of two recent case studies. Our objectives are twofold: we first look for effects of biotic interactions on species richness and species composition, and then evaluate whether the expected effects of dispersal are likely to be detected on a background of large variability caused by other ecological factors and interactions. Species richness within lakes appears to be primarily controlled by factors related to lake size, lake productivity, water quality, and fish predation levels. One case study indicated a slight, but significant, positive effect of lake density and lake area in the surrounding landscape on species richness, suggesting that frequent dispersal events may enhance species richness. This local variation in species richness is superimposed on regional variation in species pools. 相似文献
13.
Biological invasion by a benthivorous fish reduced the cover and species richness of aquatic plants in most lakes of a large North American ecoregion 总被引:1,自引:0,他引:1
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Przemyslaw G. Bajer Marcus W. Beck Timothy K. Cross Justine D. Koch William M. Bartodziej Peter W. Sorensen 《Global Change Biology》2016,22(12):3937-3947
Biological invasions are projected to be the main driver of biodiversity and ecosystem function loss in lakes in the 21st century. However, the extent of these future losses is difficult to quantify because most invasions are recent and confounded by other stressors. In this study, we quantified the outcome of a century‐old invasion, the introduction of common carp to North America, to illustrate potential consequences of introducing non‐native ecosystem engineers to lakes worldwide. We used the decline in aquatic plant richness and cover as an index of ecological impact across three ecoregions: Great Plains, Eastern Temperate Forests and Northern Forests. Using whole‐lake manipulations, we demonstrated that both submersed plant cover and richness declined exponentially as carp biomass increased such that plant cover was reduced to <10% and species richness was halved in lakes in which carp biomass exceeded 190 kg ha?1. Using catch rates amassed from 2000+ lakes, we showed that carp exceeded this biomass level in 70.6% of Great Plains lakes and 23.3% of Eastern Temperate Forests lakes, but 0% of Northern Forests lakes. Using model selection analysis, we showed that carp was a key driver of plant species richness along with Secchi depth, lake area and human development of lake watersheds. Model parameters showed that carp reduced species richness to a similar degree across lakes of various Secchi depths and surface areas. In regions dominated by carp (e.g., Great Plains), carp had a stronger impact on plant richness than human watershed development. Overall, our analysis shows that the introduction of common carp played a key role in driving a severe reduction in plant cover and richness in a majority of Great Plains lakes and a large portion of Eastern Temperate Forests lakes in North America. 相似文献
14.
《Harmful algae》2014
A statistically significant association was found between the concentration of total microcystin, a common class of cyanotoxins, in surface waters of lakes and reservoirs in the continental U.S. with watershed land use using data from 1156 water bodies sampled between May and October 2007 as part of the USEPA National Lakes Assessment. Nearly two thirds (65.8%) of the samples with microcystin concentrations ≥1.0 μg/L (n = 126) were limited to three nutrient and water quality-based ecoregions (Corn Belt and Northern Great Plains, Mostly Glaciated Dairy Region, South Central Cultivated Great Plains) in watersheds with strong agricultural influence. canonical correlation analysis (CCA) indicated that both microcystin concentrations and cyanobacteria abundance were positively correlated with total nitrogen, dissolved organic carbon, and temperature; correlations with total phosphorus and water clarity were not as strong. This study supports a number of regional lake studies that suggest that land use practices are related to cyanobacteria abundance, and extends the potential impacts of agricultural land use in watersheds to include the production of cyanotoxins in lakes. 相似文献
15.
Enrique García-Muñoz Juan Diego Gilbert Gema Parra Francisco Guerrero 《Biodiversity and Conservation》2010,19(3):901-911
Habitat fragmentation and alteration have been described as the major factors relating to the decline observed in several
amphibian species. In Spain, these processes are mainly associated with the large agricultural land area, the widespread use
of toxic substances, and the agricultural practices used. All these aggressions affect wetlands and their watersheds, which
are essential aquatic systems for many amphibian species. In an effort to discover where conservation and specific action
plans could be more necessary, this study relates the amphibian richness in 28 representative Mediterranean wetlands to their
characteristics and the activities carried out on their watershed. The required information considers diverse wetland variables.
Our results show that watershed habitat heterogeneity is significantly positively correlated with amphibian richness, while
the percentage of the watershed area devoted to olive cultivation is negatively correlated with it. The results allow us to
classify wetlands according to their importance for amphibian conservation. Our results also show that 80% of the studied
wetlands need specific action plans. Especially, more sustainable cultivation methods are required considering drastic changes
in current agricultural practices. Finally, our data provides a baseline to understand future alterations due to agricultural
practices. 相似文献
16.
Giuseppe Alfonso Genuario Belmonte Federico Marrone Luigi Naselli-Flores 《Hydrobiologia》2010,653(1):149-164
Zooplankton assemblages of 51 lacustrine environments located in the middle of the Mediterranean Region were analysed to evaluate
the existence of an ‘age effect’ in determining their structure. The analysed datasets refer to two different geographic areas,
one comprising 30 natural and artificial lakes in Sicily and the other an arrangement of 21 analogous aquatic ecosystems located
at the bottom of the Italian Peninsula, a more pristine area called Southern Apennine region. Most of the natural lakes are
of post-glacial origin. The artificial lakes in both datasets were built in the last century and offer the opportunity to
evaluate the possible short-term effects of ageing on the structure of their zooplankton. A comparison of assemblages in the
two regions by PERMANOVA and nMDS revealed that they are quite different; therefore they were analysed separately. An explorative
analysis on the possible relationship between biological data and environmental data (including lake age) was performed on
both datasets using DISTLM. The presence of an ‘age effect’ emerged only in the subset of artificial lakes of the Southern
Apennine region; accordingly it was tested more in detail with an a posteriori PERMANOVA analysis in the subset of reservoirs
that resulted positive in the first test. SIMPER allowed us to single out the main species responsible of changes in the zooplankton
along the selected age groups. No age effect was evident in the Sicilian water bodies, where other variables, such as conductivity,
trophic state, urbanisation and water level fluctuations proved to have a major role in shaping zooplankton assemblages. The
results showed that the age effect is: (i) detectable only at a time scale of decades; (ii) masked by the human impact in
the watershed. 相似文献
17.
- The North American Great Plains contains thousands of lakes that vary in salinity from freshwater to hypersaline. Paleolimnological studies show that salinity levels in these lakes are tightly linked with climate, and current projections point to a more arid future in the region due to natural and anthropogenic climate change, potentially influencing lake salinity.
- Many zooplankton species are sensitive to changes in salinity, and their position near the base of the aquatic food web makes it important to understand how they might respond to increasing salinity levels. Zooplankton communities in lakes with rising salinity levels may exhibit changes in structure, including a shift toward more salinity-tolerant species and a reduction in abundance, species richness, and diversity. However, it is possible that dispersal of zooplankton among lakes could mitigate such community changes when migrant populations replace sensitive zooplankton with those that are locally adapted to higher salinities.
- To test if dispersal could reduce salinity-induced changes in zooplankton communities, we ran a field enclosure experiment at a freshwater lake in southern Saskatchewan where we manipulated salinity levels and zooplankton dispersal. We evaluated how salinity and dispersal influenced species identities and relative abundances (community structure) using multivariate statistics and comparing taxonomic and functional compositions among the different treatments (richness, diversity, and evenness).
- We found that increasing salinity levels in our enclosures above that in our study lake resulted in lower zooplankton abundances and species richness levels, primarily due to the loss of cladoceran species. However, patterns in our multivariate analyses suggested that cladocerans were maintained in enclosures with salinity levels of 2.5 and 5.0 g/L when those enclosures received immigration from nearby lakes.
- In contrast, our univariate analyses failed to find evidence that immigration affected community structure (richness, diversity, evenness). The lack of significant statistical differences could suggest that dispersal does not have an effect, or it may have been a problem with statistical power, as a power analysis suggested that fairly large effect sizes would have been required to achieve statistical significance.
- Based on our results, we were unable to reach a definitive conclusion on the role that dispersal might play in buffering zooplankton communities against salinity-driven changes. However, our study provides two important insights for planning future work. First, our power analyses indicated that more replication may be needed given the variability among our experimental enclosures. Second, the patterns in our multivariate analyses suggested that cladocerans could be maintained in lakes undergoing salinity increases if they receive immigration from surrounding lakes with higher salinities. Future work examining how inter- and intraspecific salinity tolerance varies across lakes with a gradient of salinities would be helpful for understanding the role that dispersal might play in buffering against salinity-driven losses of cladoceran zooplankton.
18.
19.
Regional versus local processes in determining zooplankton community composition of Little Rock Lake, Wisconsin, USA 总被引:3,自引:0,他引:3
The species present within a community result from a combination of local
and regional processes. We experimentally tested the importance of these
two processes for lake zooplankton communities by examining the ability of
additional species to persist when introduced into mesocosms in Little Rock
Lake, Wisconsin, from other nearby lakes in the Northern Highland Lake
District. We established a control treatment with only Little Rock Lake
zooplankton and two treatments that supplemented the Little Rock
communities with zooplankton from nearby lakes. Species richness declined
during the 3 weeks of the experiment so that, at the end of the third week,
the treatments with added zooplankton species had the same number of
species as the controls; increasing the initial number of species in the
community did not increase its final species richness. A plot of the mean
species richness in the local habitat against the mean species richness of
the regional pool fell below a 1:1 slope. This suggested that local
processes were more important in structuring Little Rock Lake zooplankton
communities.
相似文献
20.
黄土高原不同植被覆盖对流域水文的影响 总被引:7,自引:0,他引:7
以山西省吉县蔡家川流域为对象,研究了植被覆盖类型对流域水文的影响.结果表明:不同植被覆盖的流域年径流系数分别为:林地流域1.6%~2.3%,以农、牧为主的流域3.1%~3.9%;各流域基流系数差异显著,人工林流域为零,次生林为主的流域1.0%~1.5%,以农、牧为主的流域2.5%~2.8%;在雨季人工林流域的径流总量是次生林流域的3.37倍、农地流域的1.9倍,而农地流域的基流量是次生林流域的2.2倍;短历时高强度降雨条件下,人工林流域、次生林流域地表径流量分别是农地流域的10.8倍和2.2倍;在历时较长的暴雨条件下,人工林流域单位面积上的洪峰流量是农地流域的3.4倍,次生林流域的6.9倍;在长历时、大雨量条件下,农地流域的径流量是次生林流域的1.8倍.水平梯田的水源涵养功能与次生林植被相当,次生林植被的水源涵养功能远好于人工植被,在水资源短缺的黄土高原应提倡植被的自然恢复. 相似文献