The main objective of this study which was conducted in an intact stand of the experimental Kheiroudkenar forest (Chelir district), was to examine the ecological importance of dead trees followed by it's impact on natural regeneration of the forest. In this study the seedlings around dead trees were recorded in a 50 ha stand, where the dead trees were divided into four decay classes. Considering the decay classes, results indicated that; there were different kinds of establishment of regeneration. The highest numbers of seedlings were accounted around dead trees classified in 3rd decay class, while 4, 2 and 1 decay classes were in the next orders. Gap opening related to dead trees had important effects on establishment of the regeneration. Results showed that with increasing of decay classes, size of gaps decreased. In this study gaps were divided into five groups, including close gap (closed canopy), very small (0-12.5 m2), small (12.5-50 m\medium size gap (50-113 m2) and large size or open canopy (>113 m2). Abundance of seedlings under the closed gaps of stand crown was maximum, while the numbers of seedlings were reduced under the medium gap size, very small, small and large size, respectively. One way analysis of variance showed that there was no significant difference (at 5% significant level) among the number of seedlings around dead trees with different decay classes, however there was a significant difference among abundance of seedlings under different gap sizes, produced by dead trees. Therefore, gap opening caused by dead trees, had higher effect on establishment of regeneration than decay classes.

In order to investigate the effects of type and the degree of decay of snags and logs on regeneration density of woody species, Sardabrood forests in Mazandaran province was studied. For this reason, circle plots with radius of 5 meters from snags center and rectangular plots with 4 meters width (2 meters from two sides of each log) and the length of logs were taken. Also, canopy gap areas caused by dead trees and their decay degree were measured. The results of ANOVA showed that the most density of regeneration around snags and logs was that of the species of hornbeam and beech and the lowest belonged to maple species. The canopy gap areas (0, 0-12.5, 12.5-50, 50-113 and more than 113 m2,, respectively) had different regeneration density. Regeneration density was reverse in different degrees of decay for logs. The maximum and minimum of regeneration density observed in fourth and first decay degrees, respectively. But, no significant statistical differences observed related to decay degrees of snags. 

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.

This study was carried out in Kheiroud forest to investigation of forest crown gap - that made by dead trees - effects on natural regeneration and its management according to the dominant forest type of forest. Commonly gaps made in forest crown since dying a tree in the forest. These gaps have several effects on diversity and composition of seedlings. According to the gaps effects on regeneration and management importance of them, in this research seedlings under gaps measurement and divided to four area groups, very small, small, medium and large sizes, were recorded in height and species groups. Data analysis Results showed that maximum frequency of seedlings number was settled under medium sizes gaps and under very small, small and large sizes gaps respectively. According to the regeneration species frequency, Fagus orientalis was maximum and after it Acer sp, Carpinus betulus and Alnus subcordata were respectively and in height division of seedlings, high frequency of seedlings was in fewer than 30 cm that shows same time reproduction of mother trees in the study area and we encountering with an old forest. Conservation programs for young regeneration under gaps and different silvicultural operations should be done to help them in the gaps management.

In temperate forests canopy gaps play an important role in driving stand dynamics. The purpose of this research was to compare soil characteristics in forest gaps with several size and its relation to Beech regeneration density in Lalis forest, Chalous. In order to investigate factors, three gap sizes as small gap (200 m2), medium gap (400 m2), and large gap (600 m2) with three replicate were selected in lactation. Mineral soil samples were randomly collected from four different places in each gap, all over the gap area. Nine circular subplots of 3.14 m2 were established inside each gap on two principal diagonals and the regeneration density of Beech species was estimated. Some of soil characteristics, such as total carbon, total nitrogen, available phosphorous, soil acidity (pH), C/N ratio, saturation moisture and soil texture (clay, silt and sand) were measured. Results showed that the carbon and C/N ratio significantly decreased with increasing of gap size. The other soil characteristics significantly increased with increasing of gap size. Similar to results, statistical difference between regeneration densities with soil characteristics was found. With thicken of soil characteristics consisting of nitrogen, phosphorous, pH, and moisture, regeneration density increased. Carbon and C/N ratio affected negatively on regeneration density, but there were no significant differences in soil texture ingredient between gaps.

We studied 11 gaps covered with beech saplings (<1.30 m tall) in a reserve compartment (compartment 139, district one, Langa forest, watershed 36: Kazemrood) of the Caspian beech forest in N Iran. Two transects, each 2 m wide, were laid along the longest (N-S) and shortest (E-W) axis of each gap. Five micro sample plots, each 4 m2, were established: one at the center, and one at each corner. Qualitative and quantitative characteristics of saplings with a diameter at breast height less than 7.5 cm were examined in the micro sample plots. Analysis of variance (ANOVA) and Kruskal-Wallis test were performed using SPSS software for quantitative characteristics, and chi-square test for qualitative characteristics. Results indicated that medium-sized (200-500 m2) gaps promote the growth of oriental beech saplings of desirable silvicultural forms during decay and initial stages.

Oriental beech (Fagus orientalis Lipsky) seed storing is unavoidable, due to long-time cycle of mass seed production (sometimes up to 8 years) and demand for restoration of its non-regenerated gaps in northern forests of Iran. In this research, F. orientalis seeds with moisture content (MC) of 30% and 7% were stored during 11 months in refrigerator (4ºC). By terazolium test, it was revealed that viability of both seed types started to decline after month 3. At the end of the month 11, the viability of seeds with 30% and 7% MC was 51% and 76%, respectively. It is concluded that, the fresh and dry seeds of F. orientalis can be stored near to 1 year in mountain forests of north of Iran and then sown in nursery or sown/broadcasted (with soil scarification) in forest. In order to inhibit the decay, fresh seed is better to be soaked with fungicide at once collection.

To reach a dynamic forest and preserve the original species in forest and help the natural life restoration the exploitation method of close to nature can be the most essential technique in preserving the north forests of the country. In this study the diversity of tree and grassy species was considered in the gaps made due to single selection cutting in the seventh series Siyahkal shenround forests parcel 704. At the beginning by spryer forest 35 gaps in three groups with the menstruations 100- 200, 200- 300, 300-400 square meters were assigned and randomly from each group 5 gaps and totally 15 gaps were selected on account of inventory. In order to consider the grass covering along the length of two diameters of gaps, the pieces with size of 2 2 meters, and one meter distance from each other were performed systematically. The study showed that with increase of gaps surfaces the number (richness) and quantity (evenness) of the tree species increases but it doesn't have a specific order. Also, 20 botanical species in the gaps of 1-2R, 21 botanical species in the gaps of 2-3R, 23 botanical species in the gaps of 3-4, was observed. To measuring the different diversity indexes showed that in the gaps with 300- 400 square meter, the shannon winner index with the amount 2.799 had the highest value and according to the calculated value and importance of each species (SIV) in each of the gaps the most importance was allocated to the fagus species and the lowest importance was allocated to, Honey locust, malus and pyrus species.

This study was carried out in the reserve area of district one of Langa region in Kelardasht. Development stages including initial, optimal and decay were identified and one sample plot with one hectare area (100 mx100 m) was selected in each development stage. Quantitative characteristics of saplings with diameter at breast height less than 7.5cm were determined in the micro plots. One hemispherical photograph was taken by Fish-eye camera lens in order to study the status of light in development stages as well as the relationship between quantitative and qualitative characteristics of saplings and relative light intensity. Light intensity parameters were processed by Gap Light Analyzer (GLA) V.2 software.Results showed that mean frequency of seedlings and saplings and mean annual height growth increased by increasing of relative light intensity in the decay stage. Frequency of trees decreased from initial to optimal stage and then towards decay stages. Maximum and minimum of stocked volume was measured at initial and decay stages, respectively. Stocked volume of larger timber classes in development stages was higher than small timber classes. Considering the obtained results, we can recommend to establish the regeneration in the optimal stage by creating gap and can improve the quality of the regeneration in the initial and decay stages by silvicultural interventions.

The opening of gap in the forest canopy cover causes light to shine more forcefully to the forest floor, and it makes changes in organic layers and forest soil. In this research, parcel 18 of the forestry plan in Jamand district was selected, which was fully callipered and all of the natural gaps in it were investigated and their effects on forest floor and upper most mineral soil layer properties were studied. In the center of each gap, samples of organic layers (layers L, F, H) were taken from 0.25m2 area and soil samples from 0-15cm depth. In this research gap sizes were studied in 4 classes: 1st level (50-200 m2), 2nd level (200-400 m2), 3rd level (400-600 m2) & 4th level (600-800 m2) and they were analyzed. According to the results achieved, the amount of the percentage of moisture in organic layers (layers L & F) was influenced by the gap size and it had a significant difference at 5% level. Increasing the gap size, the percentage of moisture in these two surface layers was decreased. Organic Carbon (OC) and amount of C:N in the H layer had a significant difference at 5% level, as the highest amount of them was in the first class and the lowest amount was in the second class. Also, the total Nitrogen (N) of soil showed a significant difference at 5% level, as the highest amount of it was observed in the fourth class. Generally in this research, the second class could provide the best condition for decomposing and increasing the rate of nutrient return.