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1.
The species diversity at the regeneration stage, inflenced by different water levels, is important for community composition in the later growing season. Regeneration diversity of Carex lasiocarpa community under different water levels was studied at two stages, recruitment and adult, in the Sanjiang Plain, Heilongjiang Province, China. The results showed that, at the two growing stages, important value of C. lasiocarpa population and species richness of the community decreased with the increasing water level, while the Simpson and Shannon-Wiener diversity indexes and Pielou evenness index increased. Under different water levels, community diversities were higher at the recruitment stage, while population important values of C. lasiocarpa were higher at the adult stage. Indexes in vegetation evaluation must be chosen prudentially for successful restoration and effective management of wetlands, and especially for wetland restoration, the optimal time should be selected according to the restoration objectives and costs.  相似文献   

2.
As a structure linking the ecosystem and population, community plays an important role in the marine ecology. Abundance of different species and development stages were used in our classification to the sampling stations with clustering-analysis and multi-dimension scaling, through which three geographic communities were marked out, respectively as following: the Salp community characterized by presence of Salp thompni in the northern area, the Near-shore community by Euphausia crystallorophias in the south and the main ocean community located between the above two communities. Indicator species method was then carried out between every two communities to findout which species or stages differ most. It tells that Rhincalanus gigas, adult cheatognath, late stages of Metridia gerlachei and calyptopis of Euphausiidae are indicators between Salp and neritic communities, between Krill and Salp communities are Salp thompni, adult and larvae of Cheatognath and R. gigas, and the most notable indicator between the Krill and the neritic communities are E. crystallorophias, then nauplii of Euphausiidae and Onceae conifera with less evidence.  相似文献   

3.
Precipitation plays an important role in the water supplies that support ecological restoration by sustaining large-scale artificial plantations in arid and semiarid regions, especially black locust(Robinia pseudoacacia) plantations(RP plantations), which are widely planted due to R. pseudoacacia being an excellent pioneer species. Characterizing the response of soil moisture to rainfall events at different stages of restoration is important for assessing the sustainability of restoration in RP plantations. In this study, we quantified the response of soil moisture to rainfall events at different years of restoration(15, 20 and 30 yr) representing different restoration stages in RP plantations in a typical hilly-gully area, i.e., the Yangjuangou Catchment, of the Loess Plateau, China. Over the growing season(June to September) of 2017, smart probes were placed at nine depths(10, 20, 40, 60, 80, 100, 120, 150, and 180 cm below the soil surface) to obtain volumetric soil water information at 30-min intervals in the three RP plantations. The advance of the wetting front was depicted, and the total cumulative water infiltration was measured. Soil moisture was mainly replenished by eight heavy rainfall events(mean rainfall amount = 46.3 mm), accounting for 88.7% of the rainfall during the growing season. The mean soil moisture content profiles of RP plantations at the three restoration stages were ordered as 30-yr(14.07%) 20-yr(10.12%) 15-yr(8.03%), and this relationship displayed temporal stability. Soil moisture was primarily replenished by rainfall at the 0-60 cm soil depth, and soil moisture remained stable below the 100-cm soil depth. The rainfall regime influenced the advancement of the wetting front. Here, a single rainfall event of 30 mm was the rainfall threshold for infiltration into the 60-cm soil layer. The total infiltration time ranged from 310.5-322.0 h, but no significant differences were found among RP plantations at different restoration stages. Young and old RP plantations had more total infiltration(more than 228.2 mm) and deeper infiltration depths(80-100 cm) than middle-aged plantations. The RP plantation at the intermediate restoration stage exhibited minimal total infiltration(174.2 mm) and a shallow infiltration depth(60 cm) due to the soil physical structure of the plot, which may have limited rain infiltration. More stand conditions that may affect infiltration should be considered for priority afforestation areas.  相似文献   

4.
A STUDY ON MARSH EVAPOTRANSPIRATION IN THE SANJIANG PLAINChenGangqi(陈刚起);LuXinnguo(吕宪国)(ChangchunInstituteofGeography,theChin...  相似文献   

5.
In recent decades,overgrazing and the warming and drying climate have resulted in significant degradation of alpine grasslands in the source region of the Yellow River.However,research into the relationships between vegetation and soil properties has mainly focused on an overall degradation stage,and few studies have investigated which soil properties can impact vegetation change at different stages of degradation.Vegetation and soil properties were observed in the field and measured in the laboratory for different predefined stages of degradation for alpine grassland in Maduo County in the source region of the Yellow River.Results show that:1)the aboveground and belowground biomass,soil organic carbon,total nitrogen,nitrate,and ammonia content did not decrease significantly from the intact to moderate degradation stage,but decreased significantly at severe and very severe stages of degradation;2)dominant plant species shifted from gramineaes and sedges to forbs;3)the species richness and Pielou evenness indices decreased significantly at the very severe degradation stage,the Shannon-Wiener diversity index increased at the slight and moderate degradation,but decreased at the severe and very severe degradation stages;4)soil bulk density was the strongest soil driver for changes in the plant biomass and community diversity at the intact,slight and moderate degradation stages,whereas soil organic carbon and nitrate nitrogen content were the main driving factors for changes in plant biomass and diversity at the severe and very severe degradation stages.Our results suggest that there may be different interactions between soil properties and plants before and after moderate stages of degradation.  相似文献   

6.
Are there some relationships among species diversity and soil chemical properties of high altitude natural grasslands? Plant community composition and chemical properties of soil samples were compared to investigate the relationship between soil and species diversity, and the richness in Tibetan alpine grasslands. Results showed that species diversity was significantly positively related to soil organic matter (SOM), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), available phosphorus (AP), and available potassium (AK) in the high alpine grasslands. Margalefs species richness index was also significantly positively related to SOM, TN, AN, and TP. Most soil chemical properties showed significantly positive correlation with species diversity and Margalef's richness index. Our results suggested that higher plant species richness index and diversity occurred in more fertile soil habitats in high altitude natural grassland community. In practice, fertilization management for the restoration of degraded grassland should be conducted with reference to the nutrient levels ofnatural grassland without the additional artificial fertilizer and with higher species-diversity and richness index.  相似文献   

7.
Secondary forests account for a large amount of subtropical forest due to persistent anthropogenic disturbance in China. The interaction between vegetation and soil during recovery process is rather complex and dependent on forest conditions. Understanding how vegetation and soil properties changes and how their relationship develops in secondary forests is key to effective forest restoration and management. Here we explored the patterns of vegetation and soil properties as well as their correlations during forest recovery process in a subtropical forest in south China. Plots of three forest types, i.e., broadleaf-conifer mixed forest, broadleaved forest and old growth stand, were established to represent the recovery stages. The results showed that diversity patterns in the tree, shrub and herb layers were different: in the tree layer the species diversity peaked at the intermediate stage, while in the understory layers it decreased chronologically. Most of the soil factors showed an increasing trend, and different effects of soil factors were found for the three layers as well as for the two spatial scales. Together, our results suggested that vegetation and soil might be interdependent during the recovery course. Further studies are needed on exploring how vegetation interplays with soil at different scales and how nutrient limitations affects the vegetation development in a chronosequence.  相似文献   

8.
Deyeuxia angustifolia wetlands were widely distributed in the Sanjiang Plain in Northeast China. Due to strong demand for food production, large-area wetlands were reclaimed to farmlands, which threatened regional ecological security greatly. Since the 21 th century, returning farmlands to wetlands was widely adopted for natural restoration in the Sangjiang Plain. As the first reflection of wetland restoration, vegetation succession of restored D. angustifolia wetlands should be fully assessed. In this study, vegetation investigation was carried out in three restored D. angustifolia wetlands with 5, 8 and 12 yr restoration, respectively. Meanwhile, a natural D. angustifolia wetland was selected as reference wetland. Results showed that community composition changed greatly and there was visible community succession. Community dominant species changed from composite to gramineae as restoration time increasing.At first, weeds community appeared in the restored wetlands, especially the xerophytes developed to the pioneer species rapidly. And then, mesophytes and wetland species became the dominant species in the restored wetlands. Finally, wetland species, especially D. angustifolia, occupied the dominant position of restored community. Shannon-wiener index(H) and Simpson index(D) both decreased to close to natural D. angustifolia wetlands. Compared with natural D. angustifolia wetland, species composition and diversity in restored wetlands were more complex and higher. As restoration time increasing, there were not significant differences between community characteristics of restored wetlands and natural wetland. All these suggested that vegetation in reclaimed D. angustifolia wetland could be restored naturally, but its restored period is 10 yr at least. From another angle, it is important to protect current natural wetlands.  相似文献   

9.
Broadleaf-Korean pine forests exhibit high species richness and distinctive species composition, which are currently becoming more dominant among natural forests in Changbai Mountains of northeastern China. Understanding the ecological process of restored vegetation is quite important for ecosystem reconstruction. Distinguishing stand development stages and analyzing the dynamic spatial patterns could provide insights into significant community coexistence mechanisms. In the present study, eight permanent study areas were established according to the substituting space for time method in Changbai Mountains of north-eastern China. The optimal division method was used to quantify the successional series into different stand development stages, and the point pattern analysis method(L(r) function) was used to analyse the dynamic changes in spatial patterns and interspecific associations. Our results suggested that:(1) The stand development process was divided into five stages: the first three stages were poplar-birch secondary forests in different stages of recovery, the fourth stage was thespruce-fir mixed forest, and the last stage was the primary broadleaf-Korean pine forest;(2) The spatial pattern showed an aggregated distribution at a small scale and changed to a random distribution as the scale increased in poplar-birch secondary forests, but the spatial pattern appeared to be randomly distributed in spruce-fir mixed forest and broadleafKorean pine forest;(3) The interspecific associations between pioneer species and climax species changed from negative to positive among the different stand stages, and environmental resources were shared among these species. Interspecific differences in shade tolerance among the tree species were key determinants of forest dynamics and structure. Our study is vital to the understanding of the forest development; thus, the spatial change features should receive greater attention when forest management is being planned and restoration strategies are being developed for the Changbai Mountains.  相似文献   

10.
Geographic isolation is a key factor in shaping the genetic structure of many fish species.Two sympatric species,Culter alburnus and C.mongolicus,are economically important fish that are widely distributed in China and have been recently used as new aquaculture species.We used the mitochondrial DNA control region(CR) as a marker to investigate the genetic structure of the two species.Phylogenetic analysis revealed two major lineages(Lineages I and II) that were highly consistent with geographical patterns for C.alburnus and C.mongolicus.Based on genetic distance,the Zhujiang(Pearl) River Basin(ZRB) populations potentially represented a cryptic subspecies,which might be differentiated as the result of strict geographic isolation,an earlier diverged event,or peripheral areas.Genetic diversity analysis suggested that the Changjiang(Yangtze) River Basin(CRB) populations are located at,or near the core region of their origination,not only due to the larger population size at the CRB,but also their habitat diversity and suitability for its survival,and the genetic diversity dif ferences among basin populations were significant for the two species.Moreover,demographic analysis indicated that the two Culter species and most populations had undergone a period of population expansion during warm interglacial periods.However,the C.alburnus population of Huaihe River Basin(Weishan Lake) exhibited different patterns during the interglacial period,which may due to the latest diverged time of HRB and Weishan Lake located at the permafrost.Notably,the ZRB(in Songtao Reservoir) C.mongolicus population showed no genetic diversity and had a unique haplotype,which could be treated as a special gene pool for species conservation.In summary,geographic isolation is most likely responsible for the two Culter species distribution patterns.  相似文献   

11.
Ma  Qin  Li  Mingzheng  Qin  Xiangchao  Liu  Huanzhang  Cao  Wenxuan 《中国海洋湖沼学报》2019,37(3):1090-1101
Floodplains are important and distinctive ecosystems around the world, and the recruitment of ichthyoplankton from river to floodplain lakes is crucial to maintain this unique ecosystem. However,this process has not been well documented. In this study, ichthyoplankton were sampled to investigate the details of ichthyoplankton recruitment from the Changjiang(Yangtze) River to the Dongting Lake via a floodway channel, the Songzi River, from May to July in 2013 and 2014. During the study period, 41 species of eggs and larvae were sampled. Among the samples, 16 were river-lake migratory species(RL), representing23.5% of the species in the Dongting Lake. In 2013, an estimated 130 million eggs and 3 180 million larvae drifted through the sampling section, and in 2014, an estimated 1 060 million eggs and 1 040 million larvae drifted through the sampling section. The amount of eggs and larvae of RL reached 3 210 million in 2013 and 1 850 million in 2014, respectively. These results demonstrated the importance of ichthyoplankton recruitment from the river to the lake, as species diversity will decrease sharply without this recruitment.Canonical correspondence analysis(CCA) showed that water temperature and water flow are the two most important factors influencing the spawning activities of fish. To maintain the high fish diversity in the Changjiang floodplain, we suggest to irrigate the channel to increase water discharge and increase the transport of ichthyoplankton from the Changjiang mainstream into the Dongting Lake.  相似文献   

12.
Little is known about whether soil microbial population dynamics are correlated with forest succession.To test the hypotheses that(1) soil microbial composition changes over successional stages,and(2) soil microbial diversity is positively correlated with plant species diversity,we determined the soil microbial populations,community composition,and microflora diversity in evergreen broad-leaved forests along a chronosequence of vegetation succession from 5 to 300 years in southwestern China.The soil microbi...  相似文献   

13.
MyoD,Myf5,and myogenin are myogenic regulatory factors that play important roles during myogenesis.It is thought that MyoD and Myf5 are required for myogenic determination,while myogenin is important for terminal differentiation and lineage maintenance.To better understand the function of myogenic regulatory factors in muscle development of flounder,an important economic fish in Asia,real-time quantitative RT-PCR was used to characterize the expression patterns of MyoD,Myf5, and myogenin at early stages of embryo development,and in different tissues of the adult flounder.The results show that,Myf5 is the first gene to be expressed during the early stages of flounder development, followed by MyoD and myogenin.The expressions of Myf5,MyoD,and myogenin at the early stages have a common characteristic:expression gradually increased to a peak level,and then gradually decreased to an extremely low level.In the adult flounder,the expression of the three genes in muscle is much higher than that in other tissues,indicating that they are important for muscle growth and maintenance of grown fish.During embryonic stages,the expression level of MyoD might serve an important role in the balance between muscle cell differentiation and proliferation.When the MyoD expression is over 30%of its highest level,the muscle cells enter the differentiation stage.  相似文献   

14.
Vegetation in high altitude areas normally exhibits the strongest response to global warming. We investigated the tundra vegetation on the Changbai Mountains and revealed the similarities and differences between the north and the southwest slopes of the Changbai Mountains in response to global warming. Our results were as follows: 1) The average temperatures in the growing season have increased from 1981 to 2015, the climate tendency rate was 0.38℃/10 yr, and there was no obvious change in precipitation observed. 2) The tundra vegetation of the Changbai Mountains has changed significantly over the last 30 years. Specifically, herbaceous plants have invaded into the tundra zone, and the proportion of herbaceous plants was larger than that of shrubs. Shrub tundra was transforming into shrub-grass tundra. 3) The tundra vegetation in the north and southwest slopes of the Changbai Mountains responded differently to global warming. The southwest slope showed a significantly higher degree of invasion from herbaceous plants and exhibited greater vegetation change than the north slope. 4) The species diversity of plant communities on the tundra zone of the north slope changed unimodally with altitude, while that on the tundra zone of the southwest slope decreased monotonously with altitude. Differences in the degree of invasion from herbaceous plants resulted in differences in species diversity patterns between the north and southwest slopes. Differences in local microclimate, plant community successional stage and soil fertility resulted in differential responses of tundra vegetation to global warming.  相似文献   

15.
The study intended to describe the alpine vegetation of a protected area of the northwestern Himalaya and identify the important environmental variables responsible for species distribution. We placed random plots covering different habitats and altitude to record species composition and environmental variables. Vegetation was classified using hierarchical cluster analysis and vegetation-environment relationships were evaluated with Canonical Correspondence Analysis. Four communities, each in alpine shrub and meadows were delineated and well justified in the ordination plots. Indicator species for the different communities were identified. Maximum species richness and diversity were found in community IV among shrub communities and community II among the meadows. Studied environmental variables explained 61.5% variation in shrub vegetation and 59.8% variation in meadows. Soil variables explained higher variability (∼35%) than spatial variables (∼21%) in both shrubs and meadows. Altitude, among the spatial variables and carbon/nitrogen ratio and nitrogen among the soil variables explained maximum variation. About 40% variations left unexplained. Latitude and species diversity among the other variables had significant correlation with ordination axes. Study showed that altitude and C/N ratio played a significant role in species composition. Extensive sampling efforts and inclusion of other non-studied variables are also suggested for better understanding.  相似文献   

16.
An interannual study on zooplankton abundance, biomass, and species composition was carried out during different seasons in two local coastal water types off Gopalpur, north-western Bay of Bengal. Although, Type-1 was observed with higher zooplankton abundance in comparison to Type-2, pattern of variation followed similar seasonal trends in both water types during individual years. Well pronounced seasonality was observed in zooplankton distribution. Zooplankton community was composed of 217 holoplankton and 22 meroplankton. The holoplankton community was predominated by copepod in terms of species diversity and abundance followed by hydrozoa, tintinnida, malacostraca, gastropoda, chaetognatha and chordata. The meroplankton were represented by larval forms viz. bivalve veliger, brachyuran zoea larvae, caridean larvae, copepod nauplii, fish egg and gastropod veliger. Dominance of copepod species viz. Acrocalanus longicornis, Paracalanus aculeatus and Paracalanus parvus were observed frequently in both water types. The species richness was higher in Type-1 in comparison to Type-2 during both the years. Salinity regimes and availability of phytoplankton prey influenced the distribution and species composition of zooplankton assemblage.  相似文献   

17.
Freshwater shallow lakes typically exhibit two alternative stable states under certain nutrient loadings:macrophyte-dominated and phytoplankton-dominated water regimes.An ecosystem regime shift from macrophytes to phytoplankton blooming typically reduces the number of species of invertebrates and fishes and results in the homogenization of communities in freshwater lakes.We investigated how microbial biodiversity has responded to a shift of the ecosystem regime in Dianchi Lake,which was previously fully covered with submerged macrophytes but currently harbors both ecological states.We observed marked divergence in the diversity and community composition of bacterioplankton between the two regimes.Although species richness,estimated as the number of operational taxonomic units and phylogenetic diversity(PD),was higher in the phytoplankton dominated ecosystem after this shift,the dissimilarity of bacterioplankton community across space decreased.This decrease in beta diversity was accompanied by loss of planktonic bacteria unique to the macrophyte-dominated ecosystem.Mantel tests between bacterioplankton community distances and Euclidian distance of environmental parameters indicated that this reduced bacterial community differentiation primarily reflected the loss of environmental niches,particularly in the macrophyte regime.The loss of this small-scale heterogeneity in bacterial communities should be considered when assessing long-term biodiversity changes in response to ecosystem regime conversions in freshwater lakes.  相似文献   

18.
Soil seed banks can act as a potential seed source for natural revegetation and restoration. However, in a saline-alkaline grassland, it remains unclear how the stages of vegetation succession affect the characteristics of soil seed banks and the potential of soil seed banks of different successional stages for vegetation restoration. In this study, seasonal changes of the soil seed bank, and seed production and dispersal dynamics along degradation successional gradients were investigated in a saline-alkaline grassland in Northeast China, where the dominant grass during the 1960 s, Leymus chinensis was replaced with the secondary successional order of Puccinellia chinampoensis, Chloris virgata, and Suaeda salsa, together with bare patches. It was found that the soil seed bank composition varied according to the changing vegetation and had the highest species richness(7–16) in the climax successional stage, but had a low S?rensen similarity(0.22–0.37) with the aboveground vegetation. There was a high seed density of the soil seed bank(21 062–62 166/m2 in August and December) and also high S?rensen similarity index values(0.47–0.60) in the secondary successional stages of P. chinampoensis, C. virgata, and S. salsa. In bare patches, there were many seeds in the soil seed bank and some seedlings also appeared in the aboveground vegetation, indicating the existence of a persistent soil seed bank. Seed density and species richness differed substantially among the different successional stages, which was related to the reproductive characteristics of the standing plants in vegetation communities. Due to the lack of propagules of perennial species, especially the climax species of L. chinensis, in the soil, the successful restoration of the degraded saline-alkaline grassland was not possible. The study proved that in a degraded saline-alkaline grassland dominated by biennial or annual species, the soil seed bank was important for the revegetation of the current dominant plants, but not for the restoration of the original target species. Therefore, it is necessary to induce seeds or other propagules of the target perennial species.  相似文献   

19.
Distribution patterns of plant species are believed to be impacted by small-scale habitat heterogeneity. However, there have been few comparative studies examining how woody vegetation composition and diversity varies with aspects of different orientations in the Trans-Himalayan region at a local scale. Here, we examined the effects of incoming solar radiation on variation in woody species composition and compared the diversity between the northeast- and southwest-facing slopes in a Trans-Himalayan valley of Nepal. We also examined the implicit interactions between slope orientation and land use in determining the compositional variations between the slopes. We selected two pairs of northeast- and southwest-facing slopes where the first pair has a similar land use and differs in exposure only(Pisang site) while the other pair has clear differences in land use in addition to slope exposure(Braka site). In each site, we sampled 72 plots(36 on each slope) in which the presence and absence of woody species, environmental variables, and disturbance were recorded. Correspondence Analysis(CA) results suggested that the woody species composition significantly varied between northeast- and southwest-facing slopes at both sites, and was significantly correlated with measured environmental variables such as radiation index, altitude, and canopy openness. In the Braka site,mean alpha diversity was significantly higher on southwest-facing slopes. In contrast, beta diversity and gamma diversity were greater on northeast-facing slopes at both sites. Our results suggest that topographic variables(e.g., radiation index) affect species composition between the slopes, likely due to their influence on small scale abiotic environmental variables. However, the effects of land use, such as livestock browsing/grazing may interact with the effects of slope exposure, effectively reducing differences in species composition within slopes but enhancing the differences in beta diversity between contrasting slopes in the Br  相似文献   

20.
Biotic indicators have been widely used to monitor wetland health. However, few studies have explicitly evaluated if plant diversity could serve as a useful community-level indicator of wetland stability, especially when wetlands are confronted with anthropogenic perturbations. Based on three-year record of wetland plant species abundance in Napahai plateau wetland, Shangri-la under the influence of varying anthropogenic perturbation types, our study tests the impact of such perturbations on plant richness and the relationship between ecosystem temporal stability and plant richness, and further assesses the effectiveness of using plant diversity indicator to probe ecosystem temporal stability of Napahai plateau wetland and the potential mechanisms. The results showed that anthropogenic perturbations could have contributed significantly to realistic variation in plant diversity, and further demonstrated that ecosystem temporal stability was positively related to realistic variation in plant diversity. In particular, communities with high levels of diversity might have better capacity to dampen perturbation impacts than communities with low levels of diversity, and statistical averaging could have played an important role in causing greater stability in more diverse communities. Also, asynchrony might have a stabilizing effect on community stability, and diversity could have stabilized communities through both species asynchrony and population stability propagation. Therefore, our results suggest that plant diversity could be used as a useful indicator of the stability conditions of plateau wetland ecosystems confronted with anthropogenic perturbations, and the preservation of plant communities at sufficient abundance and diversity is necessary for maintaining healthy plateau wetlands and for sustaining their essential ecosystem functions and services.  相似文献   

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