Iranian journal of Forest
Year:2009 | Volume:1 | Issue:1|Papers Count:14

In order to investigate the effect of conservation on the tree and shrub species diversity, the woody species of Oshtorankooh of Lorestan in slopes of central Zagros mountains at altitudes 1600-1800 meters were studied in three parts (central zone, peripheral zone and non-protected region) using biological diversity indices. In this study, 10 woody species were identified out of which six tree species and four shrub species were recorded. Out of the all identified species, nine, eight and four species were observed in buffer zone, central zone and non-protected region, respectively. One- Way ANOVA and Duncan tests showed that the status of diversity indices in buffer zone and core zone were better than non-protected region. There were significant differences between species dominance index in non-protected region with central and peripheral zones (p-value < 0.05). The central and buffer zones showed more suitable conditions compared to the zone located at outside of protected border in terms of richness and diversity. Also comparison between these three zones using species similarity coefficients including Jaccard, Sorensen and Ellenberg emphasize better living conditions for trees and shrubs within the protected region (central and peripheral zones) than non-protected region. The results indicate that there was a close relationship between biological diversity and conservation level in the studied area.

This research is carried out in Salvadora persica habitats of Sudano-Dekanian sub-region in Hormozgan province, south of Iran.  Five habitats were chosen and 15 plots each containing more than three Salvadora trees were established. Tree number per ha, crown diameter and suckers number of Salvadora trees as well as some characteristics of associated trees and shrubs (total number, number of plants under and out of canopy and diversity of the associated trees and shrubs of Salvadora) were studied within the plots. Totally 68 Salvadora trees were studied quantitatively. Generally, Salvadora habitats in Hormozgan province had 39-61 tree/ha, crown diameter 6.6-9.3 meter and suckers number 15.8- 84.5 within the plot. Total number of associated trees and shrubs were 8.8-60.4, number of plants under canopy 3.1-32.4 and out of canopy 3.3-49.3 and diversity of the associated trees and shrubs of Salvadora 1.7-5.9 species within the plot. Generally, 14 species of trees and shrubs were associated with Salvadora; just 6 species (Ephedra foliata, Lycium shawii, Suaeda fruticosa, Ziziphus spina-christi, Prosopis koelziana and P. cineraria) were recognized under the canopy of Salvadora trees. Ephedra foliata was observed only under canopy, but other species were observed either under or out of canopy of Salvadora trees. Suaeda fruticosa (85.4%) and Lycium shawii (79.3-100 %) were observed more under the canopy, while Ziziphus spina-christi (0-54.6%), Prosopis koelziana (0-52.4%) and P. cineraria (0-50 %) were almost observed similarly under and out of the canopy of Salvadora trees.

Sirik site is a unique mangrove site in Iran where Rhizophora mucronata occur with Avicennia marina (Grey mangrove) stands. The structure of mangrove communities as well as their special environmental characteristics differs in the country. Little is known about structure, dispersion and extent of these two mangroves stands by. In order to study the dominant species composition and distribution, IRS satellite image, acquired in 2004, and field sampling was used. The study of mangrove forests showed there exist three types of forest stands in this region; one as pure Rhizophora besides the main estuary and in contact with water, one as pure Avicennia at the end of site toward land and sometimes at the bank of estuary and mixed Avicennia and Rhizophora between two above-mentioned stands. The results showed that the establishment of Rhizophora stands increases from east to west and toward main estuary. The area of mentioned stands using GPS and georeferenced image were recorded 272.6, 43.9 and 326.7 ha for pure Avicennia, pure Rhizophora and mixed stands, respectively. The total area of Sirik forests measures 643.2 ha.

Forest road construction is the most costly operation in forest management. In order to choose the optimal variant with regard to costs and performance, it is necessary to evaluate road variants before construction. This study was performed in Namkhaneh district. Skidding coverage area with regards to landing and skid trails constraints was calculated, then it was compared with Backmund coverage area considering capabilities of wheeled skidders in wood extraction to determine the efficiency of Backmund method. The results showed that in order to evaluate the forest road networks from technical point of view with regard to capabilities of wheeled skidders in wood extraction, Backmund method is not precise enough to be the best variant and the limitations of ground skidding should be considered to use this method.

In order to study the effect of thinning operation on growth and wood production, an alder plantation (Alnus subcordata) on deep and moist soil with medium fertility was selected and thinned during 10 years. All standing and fallen trees were measured in terms of diameter at breast height (d.b.h), total height and standing volume. By thinning, the number of standing trees was decreased from 1700 to 400 stem per hectare. Results show that after thinning, the percentage of mortality decreased from 35% to less than 1% during 10 years. D.B.H growth, total height and standing volume increased 76%, 40% and 17%, respectively. The mean annual increment of standing volume was greater than 20 m3 for alder plantation grown on heavy and moist soil. Thus, Caucasian alder is proposed for intensive wood culture program in such areas (which are not suitable for poplars) in Caspian coastal plains.

In order to investigate the amount of biomass in Oak (Quercus macranthera) coppice stand, an area of 278 hectare of Khalkhal forest locating at the northeast of Ardebil was selected as the study area. After combining slope, aspect and altitude maps, the number of land form units (polygons) as well as their areas were determined. Then 63 stump sprouts were selected in such a way that all environmental and typological conditions were taken into account. After determining the overall weight of different parts of trees to measure the dry weight as well as the amount of biomass, different parts of trees were delivered to kiln. The woody debris was collected and weighted in an area of 400 cm2 under each stump sprouts. For determining the soil properties and evaluating its relationships with the amount of biomass, soil samples were taken from depth of 0-10 and 10-30 cm. The mean amount of biomass was 23.4 tons per hectare of which 65.2% were stored in aerial organs, 29.2% in underground organs and 5.6% in woody debris. There was a significant difference between the amounts of biomass in different densities of crown cover. Among the physiographic factors, only the altitude had a significant relationship with the biomass. Basal area and diameter at breast height (DBH) exhibit the highest correlation with the biomass.

As a strong supporting tool, valuation of forest ecosystems’ goods and services and estimating the costs of forest degradation and soil erosion are an effective remedy for planners and policy maker of environment. This could lead to restoration, preservation and choice of the best land uses. This research was carried out in forest lands of Sabzkouh protected area (Chaharmahal-e-Bakhtiari province) located in Zagros forest. This study was conducted to assess the soil conservation and prevention of nutritional losses as the principle economic functions of the forest land; First, sub-catchments of the studied region were separated and the outflowing volume of each sub-catchment was measured with Erosion Potential Method (EPM), then N, P, K losses based on measured nutrients in non-eroded regions were determined as control. Finally, the economic cost of nutritional conservation based on forest coverage was calculated. Results showed that 452.19kg of N, P, K elements were annually lost due to soil erosion in degraded forests with a net present value of 103.75US$/ha/year. Also, nearly 88 tons of N, P, K elements were lost annually in 5447.648 hectares at the studied area due to soil erosion leading to decrease of fertility and undertaking the environmental costs about 56597 US$.

Nettle tree (Celtis) is one of the ecologically valuable trees distributed in Elborz and Zagros mountains. Fruits are drupe and become yellow or black when ripen. Seed identification is difficult because of their various colors. In order to identify the characteristic traits for Celtis seed identification in Iran, numerous traits were evaluated, of which fruit endocarp was the most suitable one. In the current research for identification of seeds, four species from different floristic regions were studied. The characters evaluated included color, dimension, shape, amount and the ornaments on the endocarp's surface and surrounding ring (Rim). The results show that C. glabrata can be identified by means of its two rims and smooth surface; also C. australis due to its endocarp and an acute tip. There are lots of similarities between C. caucasica and C. tournefortii. So, more characteristics should be considered for identifying them. The general results show that in Celtis genus, seed and endocarp of species having been distributed in suitable sites are bigger than those in drought sites. The endocarp's color and shape are the best features to identify the Celtis. Also in order to identify the Iranian nettle tree's seed, identification key can be prepared.