Tree Species Diversity and Spatial Distribution of Aleppo Pine Stands in Northeastern Algeria

The spatial pattern of species is one of the key studied parameters in ecology so as to better understand the ecological processes and the functioning of forest ecosystems. This paper describes the classification of structural indices measuring the alpha diversity and examines typical representatives of the classification groups such as the Shannon’s index, aggregation index by Clark and Evans, the mingling index, the diameter differentiation index and the coefficient of segregation by Pielou. The tree inventory made it possible to count 7 species that are divided into six (06) families. Only Pinus halepensis Mill. trees were taken into account via calculation in spatial distribution. Western exposure shows the most regular tree patterns (1.6±0.1) according to the aggregation index by Clark and Evans, while the species mingling index for south- and east-facing stands indicates segregation of Pinus halepensis Mill. groups. The diameter differentiation index for the majority of the studied stands is assumed through estimated values within the range that starts from 0.4 to 0.9 for the four exposures. The distribution shows that western and eastern exposures belong to the fourth class of differentiation (very large differentiation), which means that the trees with the smallest DBH have less than 30% of the size of the neighbouring trees since the diameter differentiation index for the two exposures is 0.9±0.05 and 0.7±0.2.

No evidence for increased prevalence of colorectal carcinoma in 399 Dutch patients with Birt-Hogg-Dubé syndrome

Background Previously, it has been suggested that colorectal polyps and carcinomas might be associated with Birt-Hogg-Dubé syndrome. We aimed to compare the occurrence of colorectal neoplasms between Dutch patients with Birt-Hogg-Dubé syndrome and their relatives without Birt-Hogg-Dubé syndrome. Methods In all, 399 patients with a pathogenic FLCN mutation and 382 relatives without the familial FLCN mutation were included. Anonymous data on colon and rectum pathology was provided by PALGA: the Dutch Pathology Registry. Results No significant difference in the percentage of individuals with a history of colorectal carcinoma was found between the two groups (3.6% vs 2.6%, p = 0.54). There was also no significant difference between the age at diagnosis, diameter, differentiation and location of the colorectal carcinomas. Significantly more individuals with Birt-Hogg-Dubé syndrome underwent removal of colorectal polyps (12.2% vs 6.3%, p = 0.005). However, there was no significant difference between the number of polyps per person, the histology, grade of dysplasia and location of the polyps. Conclusion Our data do not provide evidence for an increased risk for colorectal carcinoma in Birt-Hogg-Dubé syndrome, arguing against the need for colorectal surveillance. The difference in polyps might be due to a bias caused by a higher number of colonoscopies in patients with Birt-Hogg-Dubé syndrome.

Contribution of Tea Root Reinforcement to Soil Shear Strength on Slope Stability

Roots played important role in the process of stabilizing the soil mass. The geo-mechanical and soil-hydrological aspects on the slope are determined by, one of it, the root reinforcement. The role of root branching series with diameter differentiation is greatly determining its tensile stress. The tensile stress from the interaction between the root and the soil, could it contribute to increasing the shear strength of the slope stability. The purpose of this research was to identify the tensile stress on root branching series that interacted with the soil and created additional cohesion as a shear strength contribution to the slope stability. Testing on the root pulling force was conducted on slope prototype with angle 30o to 40o and has been planted with tea vegetation. A tripod that was completed with strain gauge as the recording instrument was used. Testing was conducted on two and three root branching, also on each unit by observing the diameter. This testing method was done in saturated soil condition. The tensile stress result showed that increasing diameter of the tea root, an increase was noticed, and also result in the equation of TFr = 0.089e0.516d. Root diameter increase on two and three root branching to one unit of tea vegetation showed that the stress increase was significant. When observed, in the root diameter differentiation of 4 mm to 6 mm, the stress on two and three root branching and one unit of tea vegetation were respectively 5.94%, 12.30%, and 35.42%. The contribution of additional cohesion caused by root-soil interaction to soil shear strength apparently could increase slope stability.

Comparison of sampling methods for estimation of nearest-neighbor index values

Neighborhood-based indices such as mingling index and diameter differentiation are a set of diversity measures that are based on the relationship between a reference tree and a certain number of nearest neighbors (i.e., trees to which it has the lowest horizontal distance). Using stem-mapped data from eight headwater sites, we compared the relative bias and relative root mean square error (relative to the true mean of each site) of several different methods of choosing reference trees for calculation of diameter differentiation ([Formula: see text]) and species mingling ([Formula: see text]) index. Indices were defined using two, three, and four neighbors and methods for selection of the reference tree were random selection of a tree in a fixed-radius plot (FI), random selection of a tree in a variable-radius plot (VA), azimuth selection method (AZ), and nearest tree selection (NT). In general, the relative bias was lower than ±2.5% for [Formula: see text] and lower than ±10% for [Formula: see text] regardless of the method. The FI method consistently had the lowest relative bias and relative root mean squared error. The NT and AZ methods were second in terms of relative root mean squared error for [Formula: see text] and [Formula: see text], respectively. Simplicity of these two methods might outweigh their slightly worse performance.

On the way to continuous cover forest at middle elevations – the question of forest structure and specific site characteristics

The transformation process of even-aged forest stands to irregular forest stands on waterlogged sites after 20 years effort was analysed. Data from two 1-ha PRP was analysed with special focus on structural (Shannon Evenness Index, Simpson Index and Gini Index) and species (Shannon Evenness Index and Simpson Index) diversity. Different development on study plots confirmed that the highest structural diversity is not often compatible with the concept of species diversity. On PRP 1 high diameter differentiation has led to lower values of species diversity, while on PRP 2 rather moderate diameter differentiation supported higher species diversity in lower DBH classes. The Gini Index was confirmed to be the best indicator for monitoring the diameter differentiation in the course of stand transformation.

Structural diversity change and regeneration processes of the Norway spruce natural forest in Babia hora NNR in relation to altitude

The research was focused on exploring the dynamics and forms of regeneration processes and structural diversity of the Norway spruce virgin forest in Babia hora NNR in relation to altitude. In each developmental stage <br />19 sample plots were established. The structural diversity was assessed by the indices proposed by Clark and Evans (1954), F&uuml;ldner (1995) and Jaehne and Dohrenbusch (1997). Concerning the spatial distribution of the trees in the virgin forest no tendency to their clustering with the increasing altitude was found in the zones below 1,460&nbsp;m. The influence of the altitude was confirmed in the zone above 1,461&nbsp;m where the groups of &ldquo;family spruces&rdquo; are typical. Diameter differentiation was significantly higher in the growth stage. Evaluation of this attribute in terms of the altitude detected significant diameter differentiation at an altitude below 1,260&nbsp;m in the growth stage. According to the F&uuml;ldner index the virgin forest has generally medium differentiated diameter structure. According to the complex index by Jaehne and&nbsp;Dohrenbusch (1997) the differentiation of the virgin forest decreases with the ascending altitude up to 1,460&nbsp;m, where the compact forest ends. Evaluation of the seedbed revealed that 46.2% of the naturally regenerated individuals were growing on mineral soil, 52.4% on dead wood and 1.4% on wind-thrown roots. Regarding the developmental stages 46% of the individuals were found in growth stage, 23% in optimum stage and 31% in breakdown stage.

Intraspecific Diameter Differentiation as a Measure of Species Replacement Potential

A method is developed to measure species replacement potentials in forest vegetation from tree diameter records taken at a single point in time. Replacement potentials are based on mean diameter differentiation within a species when occurring with other species. The technique incorporates a correction for differences in growth rate and maximum size between species.Successional trends established for Menominee County, Wisconsin and site-successional relations examined by cluster and principal components analyses agreed closely with results of earlier studies in the Lake States. The applicability and limitations of the method are discussed.