جستجوی مقالات مرتبط با کلیدواژه « gap » در نشریات گروه « جنگلداری »

The aim of this study was to study the effects of altitude and slope factors on beech natural regeneration around dead trees in Siahroud forests of Guilan province. In order to conduct this research, 45 dead trees were selected using selective sampling method. Then, around the standing dead trees, a circular plot with a radius of 5meters and around the fallen dead trees, a rectangular plot with 4meters width (2meters from two sides of each log) were measured. Inside each plot, regeneration frequency, slope (in three classes of <30, 30-30 and > 50%) and altitude (in three classes of <700, 700-1500 and >1500 m) were measured. In order to compare regeneration in 50m distance from dead tree, the measured variables were collected in samples with the center of healthy trees with the same DBH. The results showed that the regeneration frequency of all tree species around dead trees was higher than around of healthy trees. The ANOVA test showed that there is a significant difference between the regeneration frequency in different classes of altitude and slope. Also, with increasing altitude and slope, the regeneration frequency of around healthy and dead trees was decreased. The results showed that physiographic factors have an important effect on the tree regeneration around of dead trees.

The purpose of this study was to compare the quantitative regeneration status of gaps with different areas in managed and unmanaged forests at different elevations. 72 gaps in three size classes and 18 control plots under canopy cover were randomly selected. The results showed that up to an elevation of 1400 m, there was no significant differences between the average relative abundance of seedlings among the gaps and also between gaps and under canopy cover in both managed and unmanaged stands. However, with increasing elevation, the relative abundance of Fagus orientalis Lipsky increased in unmanaged stands in small gaps. Also, the relative abundance of Fagus orientalis Lipsky at elevation of 1000-1200 and 1400-1600 m in small gaps showed a significant difference between unmanaged and managed stands. While the relative abundance of Fagus orientalis Lipsky at an elevation of 1200-1400 m in medium size gaps showed none-significant difference between the two stands. The results of this study showed that the elevation is one of the most important and influential factor on the establishment of regeneration and growth of seedlings in canopy gaps.

Process of natural regeneration in uneven-aged stands is one of basic issues for sustainability in close to nature silviculture approach. The present research started form 2009 in four intact oriental beech stands of the Hyrcanian forests. Twelve, one ha sample plots have been established in three development stages containing five micro sample plots of 4 m2. Three gap sizes (small, medium and large) with five micro sample plots of 4 m2 have been selected within the development stages and characteristics of saplings have been studied. Relative light intensity (RLI) and leaf area index (LAI) have been studied as well. Results showed that the stands in the initial and optimal stages were pure, while decay stage was mixed. The least RLI was observed in the optimal stage and small sized gap while the highest amount of RLI was in the decay stage and large gap. The lowest amount of LAI was calculated in the optimal stage and small gap size. The maximum mean height increment was measured in the initial stage and small gap, maximum length of uppermost internode and annual shoot in optimal stage and large gap and the widest crown width was calculated in the initial stage and small gap. The proportion of saplings with favored quality was highest in the optimal stage and medium gap size while the highest proportion of twig and broom shaped saplings was observed in the large gaps. Overall, small and large gaps can negatively affect the saplings, whereas medium sized gap creates better condition for saplings.

In order to comparing the regeneration and diversity in natural and created gaps, all of the gaps in two compartments in Asalem forests were identified and divided into three categories: small gaps (2), medium gaps (200-500 m2), and large gaps (>500 m2). Seven plots with an area of 4m2 (2m×2m) were taken in each gap. The number of individuals of tree seedlings and saplings were recorded and coverage percent of herbaceous species were estimated in each plot based on extended Braun - Blanquet cover - abundance scale. In addition to counting the number of species, diversity indices including Simpson (1-D) and Shannon-Wiener (H') and Smith- Wilson’s evenness indices were calculated. The Kolomogrov-Smirnov test was used to study the normality of data and then one-way ANOVA test was performed using SAS software. Totally 38 natural and 30 created gaps were identified. The results revealed that mean of each gap size was 371 m2. There were no significant difference between the size of natural and created gaps but the number and total regeneration were significant differences among natural and created gaps. The least abundance of seedlings were obtained in the small gaps. Also diversity indices had maximum in the created gaps.

Microbial biomass carbon (MBC) and microbial quotient has been utilized as sensitive indicators to changes in ecosystems that are considered in soil quality studies. This study aimed to investigate the effects of selection system on the seasonal and monthly variations of MBC and microbial quotient in mixed beech stand which was performed in 2013. For this purpose, two stands including control and forest managed by selection system in Dr. Bahramnia educational and research forest in Gorgan province, Iran. We selected 6 (3×3 meters) sample plots within each stand (3 sample plots under closed canopy and 3 sample plots under the canopy gap with an area about 400 square meters. Three soil samples were taken from 0-10 cm depth at three random points within sample plots. For each soil sample, MBC, organic carbon, soil temperature and moisture were measured monthly in each sample plots within one year. Results showed that there were many fluctuations in MBC and microbial quotient in different seasons and months through the year despite the inconsiderable variation of soil organic carbon (3.01-4.55 percent in control stand and 3.04-4.51 percent in the managed stand). The highest and least amount of these two parameters were in autumn and winter, respectively. MBC mean in control stands (933.56± 22.66 mg.kg-1) were statistically similar with managed stand (940.44± 22.92 mg.kg-1) through the year. The results indicate the potential of managed stand in maintaining the balance after implementing the selection system method and the success of the implementation of this method based on these biological indicators.

Identifying regeneration characteristics is a decisive prerequisite in forest stands management. Therefore, the objective of this research was to 1) present the most appropriate tree species for reforestation within stand gaps and 2) study the effect of relative light intensity on regeneration characteristics. Quantitative characteristics were measured in 10 gaps at district one of Loveh forest in Golestan province. Results showed differing frequencies of species depending on gap positions and relative light intensities. Except checker (Sorbus torminalis) regenerations, no significant difference was observed between mean of spring shoot length within gap positions. Annual height growth of checker was maximum for 40% relative light intensity, while the annual diameter growth of hornbeam (Carpinus betulus) and wild cherry (Prunus avium) were maximum for relative light intensity ranging between 30 and 40%, respectively. No significant difference for relative light intensities was observed between other spices characteristics. Therefore, the study concludes that the highest attention should be paid to species mixtures and their ecological requirements for reforestation within the gaps.

Variations in forest vegetation are effected by several factors, one of the most important of which being the crown canopy. This study aims to survey the effect of close and open crown canopy on the herbaceous diversity in Nav-e Asalem forests in Guilan province. To this aim, 15 canopy gaps of small (100-200 m2), medium (200-300 m2) and large (300-400 m2) sizes were selected with 5 replications each. Moreover, control plots of the same sizes were selected under the tree canopy. Along small and large diagonals in each gap microplots of 2×2 m each were measured in a randomized systematic design. The percentage of herbaceous cover was estimated using Domin scale. To assess plant diversity in each plot, diversity indices of Simpson, Shannon-Wiener, Smith-Wilson Evenness Index and herbaceous richness were derived. Results showed that increasing the gaps area resulted in a significant increase of diversity and richness. Furthermore, no significant difference was observed between diversity and richness indices between small area gaps and control areas.

Gaps within forest canopy cause changes in the received amount (intensity) and quality (PAR) of incoming light on forest ground. This research was performed in natural gaps of a reserve control compartment at Kelardasht region in Mazandaran, northern Iran and aimed to determine the role of gap size and relative light intensity on soil enzyme activity. Hence, 14 gaps at four size class (<200 m2- 200-300 m2- 300-400 m2 and >400 m2) and four light classes (<8 %- 8-17 %- 17-25% and >25 %) were selected. Soil was sampled at 0-20 cm of top soil in the center of each gap. The results showed significantly different dehydrogenase activity in classes of gap size and light intensity, where its maximum amount was observed in the large gap size (300-400 m2) and at low light intensity (< 8%), respectively. Urease activity did not show significant difference within the classes. In addition, relative soil moisture was significantly different across the gap size and light intensity classes, whereas organic matter and Nitrogen did not show to be significant different.

In the high forests which managing with close-to-nature silvicultural method, the future of forests depends on the stable establishment of saplings planted in the gaps; hence, the current study was done by selection sampling method with the aim of qualitative and quantitative investigation of natural regeneration based on the gap area in two different beech (Fagus orientalis Lipsky) forests: pure beech forest and beech with other species, in three areas of 1.5- 3, 3-5 and 5-10 R, totally amounting to 60 gaps for two different beech types (30 gaps per forest type) in Sourdar Anarestan forest management plan, Mazandaran province, North of Iran. Number of saplings in different gaps was significantly different at 0.01for both forest types. The number of saplings in small and medium area gaps was greater, whereas that of the larger ones was lower. Concerning the mean area of gap with beech forest types, there was significant difference at 0.01.The area of gaps created in the mixed beech stand was more than that in the pure beech forest and according to Duncan's test; maximum gap area was east aspect and then north eastern and west aspects. Also, results showed that as the gap area increased, the number of saplings and their quality decreased for each type. Therefore, maximum the best gap area of 3 to 5 R can be suggested to ensure the future of the planted saplings.

This paper aims to study the spatial pattern of marked trees in compartments 513 and 514 of district five of Safarood Ramsar which is located between 1200 and 1300 m. a. s. l. in the watershed management unit 30. For this purpose، twenty، 1ha sample plots were selected based on two independent communities، 16 plots in managed and 4 plots in unmanaged (control) stands، and the data on 2000 and 2012 were compared. Results showed that the structure of the 20 plots on 2000 was irregular and the selection cuttings within 12 years have made ​​some effects on the structure in 2012 which is now a bit far from irregular form. The number of trees in small، large and extra large diameter classes is reduced. The spatial pattern of marked trees in the compartment 512 showed cluster pattern (located around large and extra large timber)، whereas in the compartment 513 was random (located around small and medium timber) which is directly related to the typology of the stands. Moreover، the results indicated that the mean area of gaps in the managed and control stands was 414m2 and 284m2، respectively. Mean total height of seedlings was 1. 4m and 1. 2m in the managed and control stands، respectively. Mean seedlings number in the managed and control stands was 603 and 512 in 100 m2، respectively. None of the differences of above mentioned data were statistical significant.

Chestnut leaved oak (Quercus castaneifolia C.A.M) is one of the most commercial tree species in the Hyrcanian forests of Iran and Caucasus. Having a good knowledge of tree species habitat is essential for silvicultural intervention and treatments of different forest stands. Light has been accepted as one the important ecological factors which can be altered within silvicultural intervention that could affect the tree and wood quality. This paper aimed to study the impact of light on oak seedlings within different gap sizes and position within the gap. For this purpose, 10 gaps were selected in the Loveh oak stands, near Gorgan in eastern Hyrcanian region. Nine microplots, each 4 m2, were laid out from the gap center to the gap edge and under the mariginal tree in four directions. Hemispherical photos were taken over each microplot and the data were analysed with GLA. Quantitative (collar diameter, height, shoot length and crown width) and qualitative (mode of branching, stem form, crown shape, vitality and health) characteristics of seedligs were measured or assassed and were then analysed by SPSS and EXCEL softwares. Results showed that mean realtive light intensity varied between 9.1% under the mariginal trees and 31.7% in the gap center. The maximum of mean annual height increment of seedlings (8.7±1.2 cm) was measured in the medium gap size (200 to 500 m2). The prportion of oak seedlings at the medium gap sizes was higher than in small (< 200 m2) and large (>500 m2) gaps. The average relative light intensity at the medium gap size was computed about 20.1±7.1 %. Resultes indicate that despite categorizing chestnut leaved oak as a light demanding tree, it's seedlings need shadow in the early stages. Therefore medium gap size could be introduced to achieve better quantitative and qualitative results.

This study aimed to investigate the Humus forms and the most important factors affecting its changes in mixed beech forest in Shast Kalate (Dr. Bahram Nia) experimental forest. Therefore 32 gaps with different sizes have been selected in aforementioned parcel. In each gap 5 humus profiles were considered. The same soil sampling strategy was used in an understory point 20 meters far from gap edge. Then humus form of each profile was determined based on morphological method. Results showed that totally 9 different humus forms were observed in the study area. Mull order with frequency of 70.6 % and suborder of dysmull with the frequency of 37.8% were dominant in the study area. The average thicknesses of organic horizons in gaps were 1.7, 0.3 and 0.1 cm and in understory 2.3, 0.9 and 0.48 cm for L, F and H respectively. There was a statistically significant difference between humus forms in gaps and in understory. Also gap size and land form significantly affected the humus. The average of holorganic horizon biomass in gaps was about 486 and in understory was 686 gr/m2. The results can be considered as a pattern in prediction of close-to-nature silvicultural system effects on forest humus form state.

In this study, in order to investigate regeneration success and determine the best gap area, the quantitative characteristics of the regeneration groups were evaluated at different gap area classes. For this purpose, 15 regeneration gaps were selected at three area classes with five replications at each class, including: 50-150 (small), 150-300 (medium) and 300-600 m2 (large). Four square meter plots at two meter intervals were used to measure some quantitative characteristics of the regeneration groups by a simple systematic design on north-south (N-S) and east-west (E-W) transects. The data was analyzed, using the completely randomized statistical design and one way variance analysis and Duncan test methods. The Results showed that the total height and the height growth of the saplings were significantly higher in the large gaps in comparison to the small gaps. In addition, the frequency of seedlings and the density of sapling were the greatest in the medium sized gaps. For this reason seedling frequency of Carpinus betulus and Parrotia persica was found in the medium sized gaps. Overall, it can be concluded that in the selection cutting method, the medium sized gaps (150-300 m2) are the most suitable ones.

In temperate forests, disturbances are regarded as processes of great importance to forest vegetation. For the better perception of biodiversity, different indices were used in mountain forests of Lalis located in Chalous. Line transect method used for sampling, and plant abundances were recorded, as well. Forest gaps areas were divided into four classes including smaller than 200 m2, 200 - 400 m2, 400 - 600 m2 and larger than 600 m2 areas. In order to analyze of biodiversity, Simpson, Shannon and Wiener, Margalef, Menhenick, Peet and Camargo indices were used. Using analysis of variance, statistical difference between biodiversity indices in respect to gap sizes was found. The maximum and minimum of divers species and richness species indices were related to very large and small gaps, respectively. The highest evenness indices were related to medium and large gaps, whereas the least of evenness indices were related to small and very large gaps.

In this research typology of seedlings composition and density of Fagus orientalis stands in Caspian forests of Iran (Ramsar area), at altitude of 1200-1300 m.a.s.l. within 43 gaps were studied. The gaps were created after marking and cutting the trees. The gaps area varied between 67 and 617 m2. The trial was conducted under the fully randomized design. Based on gap size and homogeneity, 1 to 3 microplots (1m2) were established in each gap. Seedling frequency was counted in each microplot, according to their species and age range (1 and 2-4 years old). The statistical methods of chi-square and ANOVA (analysis of variance) were used to analyze the data. There was no significant difference of seedling frequency and species diversity among the gap sizes. However, the number of the defined seedlings composition and density types were four and six, respectively. Beech showed the highest frequency among the species. The maximum and average densities of beech seedling were 60 and 15 per m2, respectively. 57% of gaps showed a number of 10/m2 with 1 to 4 years old seedlings.