Long-term response of understory vegetation to stand density in Picea-Tsuga forests

1988 ◽  
Vol 18 (12) ◽  
pp. 1522-1530 ◽  
Author(s):  
Paul B. Alaback ◽  
F. R. Herman
Keyword(s):  
Species Composition ◽  
Initial Conditions ◽  
Plant Cover ◽  
Stand Density ◽  
Species Group ◽  
Understory Vegetation ◽  
Stand Age ◽  
Moss Species ◽  
Significant Difference ◽  
Study Sites

The 17-year response of understory vegetation to forest thinning experiments was examined in two study sites on the central Oregon coast to determine the role of overstory species composition and stand density on forest succession. At 6 months, no significant difference in shrub, herb, and moss species composition or abundance was detected between the two study sites. Seventeen years after treatment, however, the Piceasitchensis (Bong.) Carr. site had much less vegetation cover and diversity than the Tsugaheterophylla (Raf.) Sarg. site. Overall response of most vascular species to thinning was insignificant because of their high variability in the medium and heavy treatments. Carpet-forming mosses were consistent in increasing their percent ground cover following thinning in the Picea site, and were the only species group to increase cover relative to initial conditions. Tsuga saplings were significantly more abundant under Picea canopies than under Tsuga canopies, probably because of the increased openness of Picea canopies. The increased abundance of saplings at both sites, particularly following heavy thinning, led to a two-layered overstory canopy and relatively less shrub and herb cover and diversity. Except for ferns, most plants that persisted had animal-dispersed seed. Thinning had little effect on the loss of understory species relative to the controls. Increases in diversity with thinning occurred primarily as the result of increased invasion by shade-tolerant species. Regardless of thinning treatment, only one-third or less of the original plant cover was maintained on study plots at stand age 30 years. Early thinnings without subsequent treatments are unlikely to maintain stable herb and shrub populations in forest types where the understory would otherwise be eliminated during the intermediate stages of stand development.

scholarly journals Diversity of the genus Sargassum (Fucales: Sargassaceae) in Tho Chu Archipelago, Kien Giang Province.

2020 ◽  
Vol 42 (2) ◽  
Author(s):  
Nguyen Van Tu
Keyword(s):  
Species Composition ◽  
Similarity Index ◽  
The Other ◽  
Sargassum Polycystum ◽  
Ecological Characteristics ◽  
Significant Difference ◽  
Study Sites

Our study investigated 12 study sites in four main islands of Tho Chu archipelago in 2019. Six Sargassum species were recorded for the flora of Tho Chu Archipelago, viz.Sargassum aquifolium (Turner) C.Agardh, Sargassum feldmannii Pham-Hoang Ho, Sargassum ilicifolium (Turner) C.Agardh, Sargassum mcclurei Setchell, Sargassum oligocystum Montagne, Sargassum polycystum C.Agardh, among which  three species, namely Sargassum oligocystum Montagne, Sargassum feldmannii Pham-Hoang Ho and Sargassum mcclurei Setchell were newly recorded for Vietnam. There was a significant difference in species composition between Tho Chu, Hon Xanh, Hon Tu and Hon Cao islands; among them, Hon Xanh island differed from the other three islands by 28%, Hon Tu island and Tho Chu island were mostly similarity in flora composition with the similarity index of 85.7%. The morphology of some Sargassum species varied by ecological characteristics, especially for Sargassum aquifolium (Turner) C. Agardh and Sargassum oligocystum Montagne. 

scholarly journals Successional dynamics in Neotropical forests are as uncertain as they are predictable

2015 ◽  
Vol 112 (26) ◽  
pp. 8013-8018 ◽  
Author(s):  
Natalia Norden ◽  
Héctor A. Angarita ◽  
Frans Bongers ◽  
Miguel Martínez-Ramos ◽  
Iñigo Granzow-de la Cerda ◽  
...  
Keyword(s):  
Land Use ◽  
Time Series ◽  
Forest Succession ◽  
Initial Conditions ◽  
Basal Area ◽  
Species Density ◽  
Stand Age ◽  
Stem Density ◽  
Neotropical Forests ◽  
Study Sites

Although forest succession has traditionally been approached as a deterministic process, successional trajectories of vegetation change vary widely, even among nearby stands with similar environmental conditions and disturbance histories. Here, we provide the first attempt, to our knowledge, to quantify predictability and uncertainty during succession based on the most extensive long-term datasets ever assembled for Neotropical forests. We develop a novel approach that integrates deterministic and stochastic components into different candidate models describing the dynamical interactions among three widely used and interrelated forest attributes—stem density, basal area, and species density. Within each of the seven study sites, successional trajectories were highly idiosyncratic, even when controlling for prior land use, environment, and initial conditions in these attributes. Plot factors were far more important than stand age in explaining successional trajectories. For each site, the best-fit model was able to capture the complete set of time series in certain attributes only when both the deterministic and stochastic components were set to similar magnitudes. Surprisingly, predictability of stem density, basal area, and species density did not show consistent trends across attributes, study sites, or land use history, and was independent of plot size and time series length. The model developed here represents the best approach, to date, for characterizing autogenic successional dynamics and demonstrates the low predictability of successional trajectories. These high levels of uncertainty suggest that the impacts of allogenic factors on rates of change during tropical forest succession are far more pervasive than previously thought, challenging the way ecologists view and investigate forest regeneration.

Distribution of uranium series radionuclides in upland vegetation of northern Saskatchewan. II. Patterns of accumulation among species and localities

1986 ◽  
Vol 64 (11) ◽  
pp. 2453-2463 ◽  
Author(s):  
J. W. Sheard
Keyword(s):  
Vascular Plants ◽  
Species Group ◽  
Strong Correlations ◽  
Moss Species ◽  
River Region ◽  
Significant Difference ◽  
Northern Saskatchewan ◽  
Canonical Variates ◽  
Stable Elements ◽  
Lead 210

Multivariate methods are used to explore patterns of accumulation of radionuclides and stable elements among 10 plant species at four localities in northern Saskatchewan. Principal components analysis and canonical correlation analysis of the radionuclides and stable elements showed that lead-210 and polonium-210 are correlated with crustal elements distributed in the atmosphere and therefore are accumulated more abundantly by lichen and moss species than by vascular plants. Uranium showed a similar trend. Neither these radionuclides nor radium-226 showed strong correlations with other stable elements. The highest accumulation of uranium was in the Wollaston Lake region, especially for the nonvascular plants, where the soil levels are lowest. This tends to substantiate previous suggestions that uranium available for uptake by vascular plants is associated with groundwater rather than soil particles. Canonical variates analysis on radionuclide levels in vegetation by species group shows that trees, shrubs, lichens, and moss all have significantly different patterns of accumulation. The vascular and nonvascular groups are separated primarily by lead-210 and polonium-210 accumulation. The trees and shrubs are separated by radium-226 levels. A similar analysis by locality showed significant differences in radionuclide accumulation by vegetation in all possible pairs of localities, except between the two Wollaston Lake localities. The largest distances were between regions and were based primarily on uranium accumulation in the nonvascular plants. Differences in radium-226 levels among the shrub species are responsible for the significant difference between the two localities in the Churchill River region.

Kyiv park "Nivki" and "Teremki" forests and ecological analysis of their habitats

2014 ◽  
Vol 25 (3-4) ◽  
pp. 53-68
Author(s):  
I. V. Goncharenko ◽  
H. M. Holyk
Keyword(s):  
Standard Deviation ◽  
Species Composition ◽  
Human Impact ◽  
Soil Nitrogen ◽  
Beta Diversity ◽  
Plant Cover ◽  
Alpha Diversity ◽  
Light Regime ◽  
Individual Species ◽  
Anthropogenic Pressure

Cenotic diversity and leading ecological factors of its floristic differentiation were studied on an example of two areas – Kyiv parks "Nivki" and "Teremki". It is shown that in megalopolis the Galeobdoloni-Carpinetum impatientosum parviflorae subassociation is formed under anthropogenic pressure on the typical ecotope of near-Dnieper hornbeam oak forests on fresh gray-forest soils. The degree of anthropogenic transformation of cenofloras can be estimated by the number of species of Robinietea and Galio-Urticetea classes, as well as neophytes and cultivars. Phytoindication for hemeroby index may be also used in calculation. We propose the modified index of biotic dispersion (normalized by alpha-diversity) for the estimation of ecophytocenotic range (beta-diversity) of releves series. We found that alpha-diversity initially increases (due to the invasion of antropophytes) at low level of antropogenic pressure, then it decreases (due to the loss of aboriginal species) secondarily with increasing of human impact. Also we found that beta-diversity (differential diversity) decreases, increasing homogeneity of plant cover, under the influence of anthropogenic factor. Vegetation classification was completed by a new original method of cluster analysis, designated as DRSA («distance-ranked sorting assembling»). The classification quality is suggested to be validated on the "seriation" diagram, which is а distance matrix between objects with gradient filling. Dark diagonal blocks confirm clusters’ density (intracluster compactness), uncolored off-diagonal blocks are evidence in favor of clusters’ isolation (intercluster distinctness). In addition, distinction of clusters (syntaxa) in ordination area suggests their independence. For phytoindication we propose to include only species with more than 10% constancy. Furthermore, for the description of syntaxonomic amplitude we suggest to use 25%-75% interquartile scope instead of mean and standard deviation. It is shown that comparative analysis of syntaxa for each ecofactor is convenient to carry out by using violin (bulb) plots. A new approach to the phytoindication of syntaxa, designated as R-phytoindication, was proposed for our study. In this case, the ecofactor values, calculated for individual releves, are not taken into account, however, the composition of cenoflora with species constancies is used that helps us to minimize for phytoindication the influence of non-typical species. We suggested a syntaxon’s amplitude to be described by more robust statistics: for the optimum of amplitude (central tendency) – by a median (instead of arithmetic mean), and for the range of tolerance – by an interquartile scope (instead of standard deviation). We assesses amplitudes of syntaxa by phytoindication method for moisture (Hd), acidity (Rc), soil nitrogen content (Nt), wetting variability (vHd), light regime (Lc), salt regime (Sl). We revealed no significant differences on these ecofactors among ecotopes of our syntaxa, that proved the variant syntaxonomic rank for all syntaxa. We found that the core of species composition of our phytocenoses consists of plants with moderate requirements for moisture, soil nitrogen, light and salt regime. We prove that the leading factor of syntaxonomic differentiation is hidden anthropogenic, which is not subject to direct measurement. But we detect that hidden factor of "human pressure" was correlated with phytoindication parameters (variables) that can be measured "directly" by species composition of plant communities. The most correlated factors were ecofactors of soil nitrogen, wetting variability, light regime and hemeroby. The last one is the most indicative empirically for the assessment of "human impact". We establish that there is a concept of «hemeroby of phytocenosis» (tolerance to human impact), which can be calculated approximately as the mean or the median of hemeroby scores of individual species which are present in it.

Đặc điểm của thảm thực vật vùng đất cát nội đồng ngập nước tại huyện Phong Điền tỉnh Thừa Thiên Huế

2019 ◽  
Vol 127 (4A) ◽  
pp. 53-63
Author(s):  
Truong Hieu Thao ◽  
Hoang Ho Dac Thai
Keyword(s):  
Species Composition ◽  
Site Condition ◽  
Sandy Area ◽  
Shrub Community ◽  
Peat Swamp ◽  
Study Sites

Thảm thực vật vùng đất cát nôi đồng ngập nước theo mùa tại huyện Phong Điền tỉnh Thừa Thiên Huế dựa vào cấu trúc tổ thành được phân thành 4 quần xã đó là: Quần xã cỏ ẩm nằm ven các trằm; Quần xã cây bụi trên vùng cát trũng; Quần xã Tràm trên vùng ngập nước thường xuyên và định kỳ; Quần xã cây gỗ lớn trên đầm lầy than bùn.Mỗi một quần xã đặc trưng bởi một nhóm loài thực vật ưu thế khác nhau, cấu trúc khác nhau đặc thù cho dạng lập địa tạo nên sự đa dạng về thực vật vùng cát nói chung, và vùng đất cát nội đồng ngập nước nói riêng. Những kết quả đã đạt được là cơ sở dữ liệu về thực vật vùng cát, giúp cho công tác bảo tồn, phục hồi hệ sinh thái vùng cát sau này.Plants of submerged inner sandy area (coastal sandy and sandune areas) is divided 4 flora communities, they are Moist grasslands on the edge of the lake; Shrub community in low-lying inner sandy area; Melaleuca community on submerged inner sandy area and sandy seasonally inundated; Wood community on peat swamp, submerged inner sandy area. Site condition based causes flora communities with corresponding of species composition and ecological structures, make up the diversity of the submerged inner sandy flora system. These results contributed a database on the sandy plants for conservation, ecological based restoration in study sites.

scholarly journals PNA Predictability at Various Time Scales

2013 ◽  
Vol 26 (22) ◽  
pp. 9090-9114 ◽  
Author(s):  
Waqar Younas ◽  
Youmin Tang
Keyword(s):  
Time Scales ◽  
Initial Conditions ◽  
Prediction Skill ◽  
Multiple Model ◽  
Coupled Models ◽  
Potential Predictability ◽  
Effective Measure ◽  
Dispersion Component ◽  
Significant Difference ◽  
Better Than

Abstract In this study, the predictability of the Pacific–North American (PNA) pattern is evaluated on time scales from days to months using state-of-the-art dynamical multiple-model ensembles including the Canadian Historical Forecast Project (HFP2) ensemble, the Development of a European Multimodel Ensemble System for Seasonal-to-Interannual Prediction (DEMETER) ensemble, and the Ensemble-Based Predictions of Climate Changes and their Impacts (ENSEMBLES). Some interesting findings in this study include (i) multiple-model ensemble (MME) skill was better than most of the individual models; (ii) both actual prediction skill and potential predictability increased as the averaging time scale increased from days to months; (iii) there is no significant difference in actual skill between coupled and uncoupled models, in contrast with the potential predictability where coupled models performed better than uncoupled models; (iv) relative entropy (REA) is an effective measure in characterizing the potential predictability of individual prediction, whereas the mutual information (MI) is a reliable indicator of overall prediction skill; and (v) compared with conventional potential predictability measures of the signal-to-noise ratio, the MI-based measures characterized more potential predictability when the ensemble spread varied over initial conditions. Further analysis found that the signal component dominated the dispersion component in REA for PNA potential predictability from days to seasons. Also, the PNA predictability is highly related to the signal of the tropical sea surface temperature (SST), and SST–PNA correlation patterns resemble the typical ENSO structure, suggesting that ENSO is the main source of PNA seasonal predictability. The predictable component analysis (PrCA) of atmospheric variability further confirmed the above conclusion; that is, PNA is one of the most predictable patterns in the climate variability over the Northern Hemisphere, which originates mainly from the ENSO forcing.

scholarly journals Phyllostomidae assemblage (Chiroptera: Mammalia) in altitudinal forests at the Parque Estadual do Ibitipoca, Southeast of Minas Gerais, Brazil

2016 ◽  
Vol 106 (0) ◽  
Author(s):  
Rodrigo M. Mello ◽  
Pedro H. Nobre ◽  
Marco A. Manhães ◽  
Alexmar S. Rodrigues
Keyword(s):  
Species Composition ◽  
Floristic Composition ◽  
Abundant Species ◽  
Minas Gerais ◽  
Forest Types ◽  
Mountainous Areas ◽  
Ecological Relevance ◽  
Forest Region ◽  
Study Sites ◽  
Artibeus Lituratus

ABSTRACT Many studies have demonstrated the ecological relevance and great biodiversity of bats in Brazil. However, mountainous areas have been disproportionately less sampled, mainly in the Southeast. The aim of this study was to identify and compare the richness and diversity of Phyllostomidae, the most diverse bat family, in different forest types in Parque Estadual do Ibitipoca, trying to understand the causes of possible differences. The Parque Estadual do Ibitipoca is inserted in the Serra da Mantiqueira's domain, in an Atlantic Forest region known as "Zona da Mata", state of Minas Gerais, with an altitudinal range between 1200-1784 meters. The study was conducted in two forest types, classified as "Nanofloresta Nebular" and "Floresta Nebular", whose respective data on richness and diversity were compared. The bats were captured with 8-10 mist nets for 14 months (April 2011 to May 2012) and four nights per month totaling 62,171.25 m2h of capture effort. A total of 392 captures (12 species) belonging to the Phyllostomidae family were obtained. The most abundant species were Sturnira lilium (59.9%), Platyrrhinus lineatus (11.3%), Artibeus lituratus (8.7%) and Carollia perspicillata (7.6%). The two sampled areas presented differences in bat richness, diversity and species composition, and this difference was predominantly influenced by S. lilium. It is likely that the observed difference in the assembly of bats between the two study sites depends on the variation in floristic composition. The records of A. lituratus and P. lineatus in a few months of the year and close to Ficus mexiae bearing ripe fruits suggests that at least these species move to the park for a few periods of the year in search of food resources, possibly moving through the altitudinal landscapes.

scholarly journals Effects of grazing on plant species diversity and above ground biomass in a Trans- Himalayan Rangeland

1970 ◽  
Vol 17 (1) ◽  
pp. 25-31 ◽  
Author(s):  
Anita Pokharel ◽  
Madhu Chhetri ◽  
Chiranjibi P Upadhyaya
Keyword(s):  
Species Diversity ◽  
Species Composition ◽  
Plant Species ◽  
Diversity Index ◽  
Livestock Grazing ◽  
Above Ground Biomass ◽  
Ground Biomass ◽  
Grazing Effect ◽  
Significant Difference ◽  
Palatable Species

Limited information is available on the species composition, above ground biomass and its relations to grazing in a trans-Himalayan rangeland. Its assessment is essential for long term conservation and management. In the present study, we compared species composition, phenology, diversity index and biomass between controlled (without grazing) and open (free grazing) plots to assess the effects of grazing in the selected experimental sites of Upper Mustang during July and November 2005. Species encountered were classified as high, medium, low and non palatable and in three life form categories-grasses, shrubs and forbs. The experimental sites are dominated by forbs (80%) followed by grasses (15%) and shrubs (5%). Disturbance caused by grazing affects the phenological characteristics of the plant community. Result also reveals that species diversity, maximum possible diversity, evenness and species richness was higher in the grazed plots during July and November. A comparison of the aboveground biomass in July showed that mean percentage biomass of high, medium and low palatable species is higher in ungrazed plots. In November, the percentage biomass of only medium palatable species was higher in ungrazed plots and rest of the category is higher in grazed plots. Significant difference in July, a peak growing seasons for most of the plant species in the region reveals that the pasture has impact of livestock grazing. Keywords: Biomass, diversity, grazing effect, rangeland, species Banko Janakari: A journal of forestry information for Nepal Vol.17(1) 2007 pp.25-31

scholarly journals Clinical, virological and epidemiological characterization of dengue outbreak in Myanmar, 2015

2017 ◽  
Vol 145 (9) ◽  
pp. 1886-1897 ◽  
Author(s):  
A. K. KYAW ◽  
M. M. NGWE TUN ◽  
M. L. MOI ◽  
T. NABESHIMA ◽  
K. T. SOE ◽  
...  
Keyword(s):  
Primary Infection ◽  
Phylogenetic Analyses ◽  
Molecular Techniques ◽  
Severe Dengue ◽  
Envelope Gene ◽  
Mosquito Vector ◽  
Serum Samples ◽  
Denv Serotypes ◽  
Significant Difference ◽  
Study Sites

SUMMARYHospital-based surveillance was conducted at two widely separated regions in Myanmar during the 2015 dengue epidemic. Acute phase serum samples were collected from 332 clinically diagnosed dengue patients during the peak season of dengue cases. Viremia levels were measured by quantitative real-time PCR and plaque assays using FcγRIIA-expressing and non-FcγRIIA-expressing BHK cells to specifically determine the infectious virus particles. By serology and molecular techniques, 280/332 (84·3%) were confirmed as dengue patients. All four serotypes of dengue virus (DENV) were isolated from among 104 laboratory-confirmed patients including two cases infected with two DENV serotypes. High percentage of primary infection was noted among the severe dengue patients. Patients with primary infection or DENV IgM negative demonstrated significantly higher viral loads but there was no significant difference among the severity groups. Viremia levels among dengue patients were notably high for a long period which was assumed to support the spread of the virus by the mosquito vector during epidemic. Phylogenetic analyses of the envelope gene of the epidemic strains revealed close similarity with the strains previously isolated in Myanmar and neighboring countries. DENV-1 dominated the epidemic in 2015 and the serotype (except DENV-3) and genotype distributions were similar in both study sites.

Sign in / Sign up

Export Citation Format

Share Document