Background and Objective: Dynamics of Forest communities, before the climax stage, are very high, and small changes in the conditions of the stands would result in sudden responses such as dominant species changing or increasing the number of accessory species in the accessory stand. This study aims to predict the sequence of the beech-hornbeam stand toward beech stand in the semi-virgin forest Hyrcanian of northern Iran. Material& Methodology: After field studies, three sample plots with an area of one hectare (100 × 100 m) were selected, which included hornbeam-beech type (middle stage type of Hyrcanian forest sequence). At first, four species turbulence factors, the ratio of number of seedlings to mother rootstocks, the percentage of abundance of dry matter and the indices of diameter and height differentiation in the sample plots were measured. Findings: Layering Charts of species indicate the conspicuous presence of beech in the understory of three stands with 61. 3 percentage on average. In addition, the average number of proportion of seedlings to the number of mother trees in beech and hornbeam were are 30. 1 and 2. 3, respectively. The highest percentage of dead trees’ (67%) frequency in the plots is related to Hornbeam species. The results of the TDi and THi indexes charts, with averages of 0. 13 and 0. 1, respectively, demonstrate a dramatic competition between beech and hornbeam. Discussion and Conclusion: Through the measuring of the competition in natural stands and combining results with other factors such as stage and seedling frequency and layering in the stand indicate that beech would be likely to be replaced by hornbeem.

Background and objectives: Hyrcanian forests are very important in terms of preserving genetic reserves and the existence of some plant species that are unique to this vegetation area. Therefore, further investigation of the characteristics of these diverse forest communities for the purpose of ideal management and multi-purpose planning, with the aim of maintaining diversity in these forests, is always an inevitable necessity. Among these features is the dynamics of the structure, which affects the functioning of the ecosystem and is corrected by forest management and natural disturbances. Understanding its structure and dynamics through predicting the future structure of the forest and its evolution is very important for implementing management goals, reducing forestry costs and increasing the productivity of forest ecosystems. Based on this, this research was carried out with the main purpose of investigating the structural diversity of development stages in the managed eastern mixed beech forests.Methodology: a 10-hectare area in the managed stands of parcel No. 514, series 5 of the Safaroud forestry plan, which has 42 mosaics of initial, optimal and decay development stages, which are separated based on the indicators and criteria for determining the development stages in forest were identified and selected regardless of its size and shape. The trees inside each mosaic were numbered and measured with full callipering method. The location of all the trees with a diameter at breast height (dbh) greater than 7.5 cm was recorded using the distance and azimuth of the bases relative to each other for each tree. After numbering the trees, characteristics such as dbh and total height of the trees were measured. Then, based on the dbh, the trees were divided into four classes: small (less than 35 cm), medium (35-50 cm), large (50-75 cm) and extra large (more than 75 cm). To quantify the structure of each mosaic in the studied stands, a set of different structural indices was used based on the three characteristics of spatial pattern, mingling and dimensions of tree. After analyzing the data, the structural characteristics of the stands, including the indices of diameter and height differentiation, uniform angle, mean distance to the nearest neighbor, mingling and Clark and Evans index in the mosaics were calculated. Uniform angle and Clarke and Evans indices were used to check the diversity of tree spatial patterns. Also, to check the species admixture, the mingling index was used, and to check the diversity of tree dimensions in each development stage mosaic, the diameter and height differentiation indices were used. The density of trees was also measured using the distance index to the nearest neighbors. Analyzes related to the type of distribution of trees and the type of mixing in the studied stands were done using Crancod software (ver. 1.4).Results: A total of 3105 trees of beech and other tree species were identified and recorded, and their quantitative characteristics were presented according to the mosaics of development stages. The 10-hectare area had a total of 42 mosaics of different development stages with irregular shapes and variable areas that had been separated. The initial development stage with 18 mosaics had the most and the optimal development stage with 11 mosaics had the least frequency. The area of the mosaics varied from 292 to 5145 square meters. In total, in the investigated stands, the initial stage had the highest surface and the decay stage had the lowest surface in the studied area. The initial and decay development stages accounted for the highest and lowest number of stands dendity with an average of 427 and 212 stems per hectare, respectively. The average basal area was measured as 38.75, 42.26, and 37.63 square meters per hectare in the initial, optimal, and decay development stages, respectively. The mean distance to the nearest neighbor’s index in the mosaics of the initial, optimal and decay development stages, was obtained 4.39, 4.96 and 5.76 meters, respectively. The value of Clark and Evans index was less than one in all three development stages, which indicates that the trees in all mosaics have a cluster distribution pattern. The value of the uniform angle index was calculated as 0.5 and more than 0.5 in all stages, which indicates the cluster distribution pattern of trees. The mean mingling index in the mosaics of initial, optimal and decay development stages, was obtained as 0.31, 0.27 and 0.18, respectively. Also, the mean diameter differentiation index was calculated at 0.43, 0.37 and 0.43 in the initial, optimal and decay stages, respectively. The mean height differentiation index was 0.31, 0.28 and 0.33 in the initial, optimal and decay stages, respectively, which indicates the low to medium height difference of the neighboring trees.Conclusion: According to the management activities in the studied beech stands, the results of the quantification of the stand structure according to the mosaics of different development stages can be used as a guide and template for the management of other similar forest stands. Also, the characteristics and functions used in this research can be used by forest managers as indicators to measure the interventions made (like tending and marking) as well as to monitor the development stages in these stands over time. The structural diversity of uneven-aged managed forests is different among different development stages. Therefore, in order to understand how management activities, affect the short-term structural dynamics in beech forests, similar researches should be conducted in five to 10-year time series in the investigated stands. Also, to get better results, these studies should be done over time and by monitoring a fixed stand.

In order to provide quantitative characteristics of the oak forests structure, a six-hectare area was selected in the Shine Qalaee area of Lorestan province and the structural diversity of tree communities was investigated using the nearest neighbor Method. The Clarke-Evans, mingling, diameter and height differentiation and distance indices were employed to quantify the structure of oak forests. The mean of diameter, tree height and number of shoots per cohorts was 38. 8 cm, 2. 50 m and 11. 33 tree, respectively. Also, the mean of mingling, height differentiation, diameter differentiation was calculated 0. 33, 0. 21 and 0. 12 respectively. Tree to tree interval was 4. 07 m and Clark-Evans was 0. 9. Results revealed that tree species spatial pattern was clumped associate with low diversity of species and relatively homogeny in tree dimension that distance increase cause to falling down in diameter differentiation and raising up tree vitality. Accordingly, we could conclude that oak trees in natural habitats tend to have low diversity and high inter-species completion. In order to maintain structural diversity of stands we suggest enclosing and restoration operation in studied sites.

While most recent investigation in satellite- based remotely sensed data has concentrated upon the biophysical characteristics of overstory vegetation for large area, little attention has been given to the reflectance contribution of their associated understory, versus overstory plantation reflectance to the recorded pixel value. In this research, shrubs and herbs were considered as consistent backgrounds which have an inverse effect, in contrast to plantation overstory, to the recorded pixel value in terms of their surfaceexposure to satellite sensors. Given the fact that planted tree crown closure is correlated with their height and diameter at breast height (DBH) in the early stages of the plantation, it is expected that a relationship exists between tree canopy closure, height, DBH and their associated reflectance values. The proposed concept was tested in a case study for a Jack Pine (pinus banksina) plantation using Landsat Thematic Mapper (T. M.). The crown width height, and DBH of planted trees were measured in an area of 30m X 30m, for every 2-year age interval from 1 to 21 years. Other understory natural regeneration within a 2m radius was recorded. Crown closure, mean height, and DBH of each plot (with shrub and herb understory of more than 60%) were plotted against their associated Digital Numbers (DN(s)) for 6 T. M. bands (1, 2, 3, 4, 5 and 7). The visible region of the spectrum (bands 1, 2 and 3) showed a narrow range of reflectance and was not suitable for this purpose. Band 4 revealed a greater range of DN(s) than bands 1, 2 and 3. A strong inverse linear relationship between DN(s) and their associated canopy closure, height, and DBH were found in band 5 as r2 = 0.863, 0.941, 0.873 respectively. Band 7 showed a stronger relationship with canopy closure (r2 = 0. 81) than did the other T. M. bands (except band 5). Overall, the results of this study have shown the importance of T. M. band 5 for estimating DBH and the height of plantations based on the contrast between reflectance of the overstory and understory.

Recent advances in unmanned aerial vehicles (UAVs) technology, as well as the development of lightweight sensors, offers a great possibility for the measurement of different tree features with relatively low costs compared to traditional methods. In this research, the precision and accuracy of tree height measurement and estimation using imagery by a low-cost UAV were studied. For this aim, 854 images with an altitude of 100 m above the ground were taken and the images were processed and dense point cloud was extracted by applying Structure from Motion (SFM) algorithm. The study was conducted in 34. 79 ha of Sisangan forest park and 28 sample plots (30 × 30 m) were located in the field and tree heights were measured. Also, tree height was measured using the canopy height model. Linear regression was applied to estimate the actual tree heights based on CHM derived tree eights. The accuracy and precision of the estimates were assessed using relative bias and relative root mean square error. The differences between the field measured and CHM derived tree heights were statistically significant. Based on the results, the relative root means the square error of the height estimation of Buxus hyrcana, Carpinus betulus, Parrotia persica, and other species was 20. 39, 20. 39, 20. 57 and 20. 52 percent, respectively. The results showed that tree height measurement based on UAV images and methods that were applied in this research, is biased and the estimations are highly uncertain.

Background and objectives: Efficient and high-quality information about the current and future state of the forest is needed for sustainable management and basic planning of forest resources. Zagros forests, as one of the most important vegetation areas of Iran, have a very important effect on water supply, soil conservation, climate adjustment and economic and social balance in the whole country, hence, the sustainable protection and management of these forest ecosystems The main concern of researchers and managers in this area has become vegetation. The dominant species of these forests is Iranian oak (Quercus brantii Lindl). According to geographical and environmental conditions, this species has various habitats in the vegetation zone of the middle Zagros. Considering the noble position of the Iranian oak species in the forests of Zagros, the importance of developing more researches regarding this species is essential. The characteristics of tree diameter and height are the most important components needed in forest statistics. These variables are one of the main variables for measuring the appearance characteristics of forest trees and are used in cases such as determining the volume and drawing the height curve. Considering that measuring the height of all forest trees is a long and expensive operation, hence the use of diameter and height models to estimate the height of trees has been developed. The purpose of this research is to investigate the linear and non-linear diameter-height models of Iranian oak species (Q. brantii Lindl) in the high forests of the Middle Zagros in order to find the answer to the question of whether it is possible to estimate the height of Iranian oak high forest trees as There is a function of the diameter of the chest in this vegetative zone or not.Methodology: This research was conducted in Sefidkoh protected area of Lorestan. The dominant tree cover of this area is made of oak, like other areas of Zagros, but other plants and trees such as Cratagus persica pojark, Amygdalus sp, Astragalus sp, etc. can be mentioned in it. To carry out this research, by conducting numerous forest tours and getting to know the forests of the region, a stand with an area of approximately five hectares, which had a high forest vegetation structure, was selected. In the selected forest stand, the characteristics of DBH and total height of all Iranian oak trees whose DBH was more than 12.5 cm were counted as 100%. In total, 642 Iranian oak trees were measured in DBH and height. Linear and non-linear models were used to fit the data of DBH and height of trees, which include various models of exponential, power, density-product, growth, sigmoid and other functions. In this research, 80% of the data were used in the modeling process and 20% were used for evaluation, as well as for fitting the data and estimating the indicators of each of the models from the Curve Expert Professional software, which is a software Comprehensive software was used to fit the curves. In the modeling process, diameter data were used as independent variables and height data were used as dependent variables. In the upcoming research, to verify the accuracy of the obtained models, the RMSE, MAEand Bias in absolute and relative terms, as well as the R2 and the AIC was calculated as validation indices.Results: Based on the descriptive statistics of Iranian oak trees, the average, minimum and maximum DBH was 42.42, 12.5 and 150 cm, respectively, and the height was 6.3, 1.2 and 17 meters, respectively. Based on R2 values, the used models explained 62 to 86% of the total changes in tree height. The results of tree height-diameter modeling showed that Gompertz, MMF and Richard models have the highest explanatory coefficient (0.86, 0.86, 0.86), respectively, and the lowest standard error (307. 1, 1/307, 1/307) and AIC information criterion were (276/04, 277/13, 277/03). The results of the criteria used to validate the used models showed that the Gompertz, MMF and Richard models have RMSE of 22.22, 22.20 and 22.20%, respectively, as well as MAE respectively. 16.69, 16.74 and 16.79 percent were better able to estimate the characteristics of the height of trees. According to the mentioned results, it was found that Gompertz, MMF, and Richard models have a higher ability to estimate the characteristic height of Iranian oak trees compared to other models.Conclusion: Overall, the results of this research showed that linear and non-linear models have the ability to estimate the height of Iranian oak high forest trees in the growing region of the middle Zagros, and among these models, three non-linear models are Gompertz, MMF and Richard based on evaluation criteria. The performance was more accurate. Therefore, these models can be used in the forest areas of the middle Zagros vegetation zone, which have the same structure and habitat conditions as the studied area. It is suggested to use the generalized models of height and diameter in future researches.

We obtain the generating function for the number of columns of fixed height $r$ in a bargraph (classified according to semi-perimeter). As initial case for two distinct methods we first find the generating function for columns of height $1$. Then using a first-return-to-level-$1$ decomposition, we obtain the rational function version of the continued fraction generating function which allows us to derive separate recursions for its numerator and denominator. This then allows us to get the asymptotic average number of columns for each $r$. We also obtain an equivalent generating function by exploiting a sequential decomposition for bargraphs in terms of columns of height $r$.