scholarly journals A comparison of the accuracy of different types of samples for spatial structure indices determination in beech forests in Serbia

Topola ◽  
2021 ◽  
pp. 21-34
Author(s):  
Bratislav Matović ◽  
Dejan Stojanović ◽  
Stefan Stjepanović ◽  
Marko Gutalj ◽  
Boban Miletić
Keyword(s):  
Spatial Structure ◽  
Buffer Zone ◽  
Cluster Sampling ◽  
Beech Forests ◽  
Mean Values ◽  
Accuracy Comparison ◽  
Fixed Radius ◽  
Structure Indices ◽  
Dominance Indices ◽  
Linear Correlations

In this paper we compared the accuracy of different samples (minus the sample with the NN1 edge correction and buffer zone, plus sample and modified cluster sample) to determine indices of spatial structure in beech forests in Serbia, which can be used in regular forest inventory. The research was conducted in 11 forest stands of different structure at the territory of Central Serbia. Field data used for the assessment of spatial structure indices were collected across the examined stands on the sample plots of different sizes, using systematic grid, with the square layout of sample plots (100x100 meters). The study was conducted on 242 sample plots. For accuracy comparison of different sample types, five indices were used: Uniform angle index, Mean directional index, Species mingling index, DBH differentiation and DBH dominance indices. One-way ANOVA showed that at the stand level there were no statistically significant differences between mean values of indices obtained by different sample types. However, Simple linear correlations confirmed for most indices that if the spatial structure is to be determined with accuracy at the level of sample plots (in this case, a circular fixed radius plot of 5 acres) it is necessary to use a plus sample during data collection. For species mingling and DBH differentiation indices, Simple linear correlations show that both minus sampling with edge correction buffer zone and modified cluster sampling with somewhat less accuracy can be used to a certain extent. Minus sampling with NN1 edge correction is not practical for use on sample plots of this size in beech forests in Serbia.

scholarly journals Near Points of Convergence and Accommodation in a Population of University Students in IranNear Points of Convergence and Accommodation in a Population of University Students in Iran

2019 ◽  
Author(s):  
Hassan Hashemi ◽  
Mojgan Pakbin ◽  
Babak Ali ◽  
Abbasali Yekta ◽  
Hadi Ostadimoghaddam ◽  
...  
Keyword(s):  
University Students ◽  
Adult Population ◽  
Age Groups ◽  
Multiple Linear Regression Model ◽  
Total Sample ◽  
Cluster Sampling ◽  
Young Student ◽  
Mean Values ◽  
Snellen Chart ◽  
The Mean

Purpose: To determine the distribution of the near point of convergence (NPC) and near point of accommodation (NPA) in a young student population in Iran. Methods: The subjects were selected using a cluster sampling method. All students underwent optometry tests, including visual acuity measurement, refraction, and cover test, as well as ophthalmic examinations. The NPC and NPA were measured using an accommodative target (near Snellen chart). Results: Of 1,595 students, the data of 1,357 were analyzed. The mean NPC and NPA in the total sample were 7.25 cm (95% confidence interval [CI], 7.02 to 7.48) and 9.99 cm (95% CI, 9.69 to 10.29), respectively. Older age was associated with an increase in the NPC, which increased from 6.98 cm in 18–20 years olds to 9.51 cm in those over 30 years. The NPA was significantly associated with age and refractive errors in the multiple linear regression model, increasing from 9.92 cm in 18–20 years olds to 11.44 cm in those over 30 years (P = 0.003). Hyperopic eyes had lower NPA than myopic and emmetropic eyes (P = 0.001). In younger age groups, the mean accommodation amplitude was lower than the mean Hofstetter value. Moreover, with age, especially after 30 years, the mean values surpassed those determined using the Hofstetter formula. Conclusion: The NPC values in this study were lower than those previously reported for identical age groups. The Hofstetter formula is not always an accurate predictor of the accommodation amplitude in the Iranian adult population.

Potential drivers of spatial structure of leaf-litter food webs in south-western European beech forests

Pedobiologia ◽  
2012 ◽  
Vol 55 (6) ◽  
pp. 311-319 ◽  
Author(s):  
Nereida Melguizo-Ruiz ◽  
Oriol Verdeny-Vilalta ◽  
Miquel A. Arnedo ◽  
Jordi Moya-Laraño
Keyword(s):  
Spatial Structure ◽  
Food Webs ◽  
Leaf Litter ◽  
European Beech ◽  
Beech Forests ◽  
Western European

scholarly journals The influence of sampling unit size and spatial arrangement patterns on neighborhood-based spatial structure analyses of forest stands

2016 ◽  
Vol 25 (1) ◽  
pp. 056 ◽  
Author(s):  
Hongxinag Wang ◽  
Gongqiao Zhang ◽  
Gangying Hui ◽  
Yuanfa Li ◽  
Yanbo Hu ◽  
...  
Keyword(s):  
Spatial Structure ◽  
Tree Species ◽  
Nearest Neighbor ◽  
Structural Characteristics ◽  
Spatial Arrangement ◽  
Structure Parameters ◽  
Unit Size ◽  
Structure Unit ◽  
Dominance Indices ◽  
Selection Of

Aim of the study: Neighborhood-based stand spatial structure parameters can quantify and characterize forest spatial structure effectively. How these neighborhood-based structure parameters are influenced by the selection of different numbers of nearest-neighbor trees is unclear, and there is some disagreement in the literature regarding the appropriate number of nearest-neighbor trees to sample around reference trees. Understanding how to efficiently characterize forest structure is critical for forest management.Area of study: Multi-species uneven-aged forests of Northern ChinaMaterial and methods: We simulated stands with different spatial structural characteristics and systematically compared their structure parameters when two to eight neighboring trees were selected.Main results: Results showed that values of uniform angle index calculated in the same stand were different with different sizes of structure unit. When tree species and sizes were completely randomly interspersed, different numbers of neighbors had little influence on mingling and dominance indices. Changes of mingling or dominance indices caused by different numbers of neighbors occurred when the tree species or size classes were not randomly interspersed and their changing characteristics can be detected according to the spatial arrangement patterns of tree species and sizes.Research highlights: The number of neighboring trees selected for analyzing stand spatial structure parameters should be fixed. We proposed that the four-tree structure unit is the best compromise between sampling accuracy and costs for practical forest management.

Chemical attributes of some Queensland acid aoils. I. Solid and solution phase compositions

Soil Research ◽  
1989 ◽  
Vol 27 (2) ◽  
pp. 333 ◽  
Author(s):  
RC Bruce ◽  
LA Warrell ◽  
LC Bell ◽  
DG Edwards
Keyword(s):  
Acid Soils ◽  
Logarithmic Scale ◽  
Solution Ph ◽  
Surface Soils ◽  
Organic C ◽  
Mean Values ◽  
Exchangeable Ca ◽  
Soil Solutions ◽  
Chemical Attributes ◽  
Linear Correlations

Samples from surface and subsoil horizons of 91 acid soils in Queensland were analysed for pH, EC, Cl, exchangeable cations and organic C. Generally low values for EC, Cl, exchangeable Na and exchangeable K were found in surface soils and subsoils. Higher values of organic C, exchangeable Ca and pH occurred more frequently in surface soils, while exchangeable A1 and exchangeable Mg were generally higher in subsoils. A correlation matrix gave significant, but not strong, linear correlations between soil attributes associated with soil acidity (pH and Ca, Mg and Al saturations). Soil solutions were extracted from surface and subsoil horizons of 48 of these acid soils and analysed for pH, EC, Na, K, Ca, Mg, SO4 and monomeric Al. Ionic strengths and activities of monomeric Al species were calculated. Soil solution pH tended to be lower in subsoils than in surface soils, but very few values were <4.5. Ionic strengths were mostly <8 mM, with mean values of 5.3 mM for surface soils and 2.4 mM for subsoils. Subsoils had lower mean concentrations of Ca, Mg and K, and similar concentrations of Na, compared with surface soils. In both groups, molar concentrations followed the order Na > K ~ Mg > Ca. Mean values for activities of AlOH2+, Al(OH)2+, Al(OH)3 and AlSO4+ in surface soils exceeded those for subsoils, but activities of Al3+ were similar. Higher activities of Al species in surface soils resulted from higher monomeric Al concentrations, but it was concluded that the analytical method overestimated monomeric Al in surface soils, probably by including some of the soluble organic Al complexes present. The best correlation between pH and Al species was with Al3+ , particularly in subsoils (r2 = 0.913). Activity of Al3+ in subsoils was correlated with ionic strength (r2 = 0.666) when both were expressed on a logarithmic scale.

Distribution of certain soil inhabiting chytrid and chytridiaceous species related to some physical and chemical factors

1971 ◽  
Vol 49 (10) ◽  
pp. 1743-1755 ◽  
Author(s):  
Tom Booth
Keyword(s):  
Organic Matter ◽  
Standard Deviation ◽  
Environmental Factors ◽  
Environmental Parameters ◽  
Physical Parameters ◽  
Ecological Studies ◽  
Mean Values ◽  
Chemical Factors ◽  
Physical And Chemical ◽  
Linear Correlations

Most ecological studies of chytrids and chytridiaceous fungi in soils are primarily distributional, and autecological information for particular species is scant. In this study the distribution of 11 species, Schizochytrium aggregatum, Thraustochytrium roseum, Chytriomyces hyalinus, Rhizophlyctis harderi, Rhizophydium sp. (utriculare?), R. sphaerocarpum, R. carpophilum, R. sphaerotheca, Phlyctochytrium chaetiferum, P. palustre, and P. reinboldtae, is numerically expressed by an index (DII) derived from occurrence and frequency for 19 habitats. Mean values of various environmental parameters—pH, organic matter, bulk density, osmolarity, Ca2+, Mg2+, and Na+—are calculated for each habitat, and linear correlations of DII against means of the environmental factors of each habitat are calculated for each species. Also the range, mean, and standard deviation of chemical and physical parameters at sites where each species occurs are calculated. By these methods some autecological facts appear for each species. Basically the fungi are divisible into four groups: (1) obligately marine, S. aggregatum; (2) marine, T. roseum; (3) facultatively marine, C. hyalinus, R. harderi, R. sphaerocarpum, P. chaetiferum, R. carpophilum, R. sphaerotheca, Rhizophydium sp. (utriculare?); and (4) marine occasionals, P. palustre, P. reinboldtae. Problematic aspects of the study are discussed and another line of investigation is proposed.

scholarly journals Spatial Structure Indices of Mature Pedunculate Oak Stands in NW Croatia

2013 ◽  
Vol 4 (1) ◽  
pp. 13-21
Author(s):  
Krunoslav Indir ◽  
Hrvoje Marjanović ◽  
Ivan Balenović ◽  
Lajos Szirovicza ◽  
Elvis Paladinić ◽  
...  
Keyword(s):  
Spatial Structure ◽  
Pedunculate Oak ◽  
Structure Indices

scholarly journals Catalase activity in Smicridea McLachlan, 1871 (Insecta, Trichoptera) collected from natural and altered/impacted streams

2015 ◽  
Vol 27 (2) ◽  
pp. 160-164
Author(s):  
Cristiane Biasus ◽  
Luiz Ubiratan Hepp ◽  
Rogério Luis Cansian ◽  
Rozane Maria Restello ◽  
Albanin Aparecida Mielniczki-Pereira
Keyword(s):  
Catalase Activity ◽  
Riparian Vegetation ◽  
Agricultural Land ◽  
Buffer Zone ◽  
Drainage Area ◽  
Mean Values ◽  
Natural Streams ◽  
Agricultural Streams ◽  
Enzyme Pattern ◽  
Activity Measure

Aim: We compare catalase activity in SmicrideaMcLachlan, 1871 (Insecta, Trichoptera) collected in natural and agricultural streams and correlates the enzyme pattern with metal content in the water.MethodsOrganisms were collected in sites classified as natural (riparian vegetation in buffer zone) and altered/impacted (agricultural land use in drainage area) environments, located at Cravo River and Campo River sub-basins (RS, Brazil). Next the collected larvae were identified and used to proteins quantification and catalase activity measure. The concentration of Mg, Cr, Cu, Pb and Cd in the water was determined by atomic absorption spectrometry.ResultsCatalase activity in Smicridea ranged from 1.5 to 6 U, with mean values about 2.63 ± 0.096 U (SEM). The presence of metals was higher in the streams located at agricultural drainage area, except for Mg at the Cravo sub-basin and Cu at the Campo sub-basin. Catalase was higher in Smicridea collected in natural streams as compared to that agriculture streams and was correlated with Pb and Cd levels.ConclusionsThe data showed the potential of this biomarker as a useful tool for complementation of water quality biomonitoring studies using Smicridea as bioindicator.

Observations of the spatial structure of interstellar hydrogen

1967 ◽  
Vol 31 ◽  
pp. 45-46
Author(s):  
Carl Heiles
Keyword(s):  
High Resolution ◽  
Spatial Structure ◽  
Velocity Dispersion ◽  
Temperature Variations

High-resolution 21-cm line observations in a region aroundlII= 120°,b11= +15°, have revealed four types of structure in the interstellar hydrogen: a smooth background, large sheets of density 2 atoms cm-3, clouds occurring mostly in groups, and ‘Cloudlets’ of a few solar masses and a few parsecs in size; the velocity dispersion in the Cloudlets is only 1 km/sec. Strong temperature variations in the gas are in evidence.

Articulatory Behavior Pre and Post Full-Mouth Tooth Extraction and Alveoloplasty

1980 ◽  
Vol 23 (3) ◽  
pp. 630-645 ◽  
Author(s):  
Gerald Zimmermann ◽  
J.A. Scott Kelso ◽  
Larry Lander
Keyword(s):  
Control Subject ◽  
High Speed ◽  
Tooth Extraction ◽  
Kinematic Parameters ◽  
Experimental Conditions ◽  
Mean Values ◽  
Articulatory Movements ◽  
The Mean ◽  
Experimental Subjects ◽  
Normal Speech

High speed cinefluorography was used to track articulatory movements preceding and following full-mouth tooth extraction and alveoloplasty in two subjects. Films also were made of a control subject on two separate days. The purpose of the study was to determine the effects of dramatically altering the structural dimensions of the oral cavity on the kinematic parameters of speech. The results showed that the experimental subjects performed differently pre and postoperatively though the changes were in different directions for the two subjects. Differences in both means and variabilities of kinematic parameters were larger between days for the experimental (operated) subjects than for the control subject. The results for the Control subject also showed significant differences in the mean values of kinematic variables between days though these day-to-day differences could not account for the effects found pre- and postoperatively. The results of the kinematic analysis, particularly the finding that transition time was most stable over the experimental conditions for the operated subjects, are used to speculate about the coordination of normal speech.

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