جستجوی مقالات مرتبط با کلیدواژه « تیپ های جنگلی » در نشریات گروه « جنگلداری »

A comprehensive study of vegetation changes requires consideration of all influential factors in the ecosystem. The Zagros forests, as one of Iran's most important forest ecosystems, contain diversified vegetation including trees, shrubs, and herbaceous species. Therefore, accurate identification of vegetation and knowledge of their ecological role can help in protecting natural resources and sustainable development. The aim of this study was to investigate the changes in herbaceous vegetation in the Hashtadpahloo forests of Lorestan province.

For this purpose, after physiognomic typing of the region, 21 multi-scales, modified Whittaker plots were randomly selected in pure oak type (Quercus brantii Lindl.), Mixed oak and Acer type (Quercus brantii Lindl., Acer monspessulanum L.), Shrubs and cushion plants type (Daphne mucronata Royle, Cotoneaster morulus Pojark), and rangeland type (grassland and rangeland species). Species richness, canopy cover of tree species, Physiographic factors such as slope, aspect and altitude were measured at 250 m2 (25×10) plots, and presence and cover percentage of each herbaceous plant was recorded at o.25 m2 plots. (0.25 × 1. Furthermore a combined soil samples were taken at 0–30 cm depths to determine soil properties. After measuring plant diversity indices such as Margalf, Mannick and Shannon Wiener indices and some physical and chemical characteristics of soil in laboratory, principle component analysis (PCA) was used to indicate the most important environmental factors affecting diversity indices in different types.

The results showed that there were significant differences among different vegetation types with respect to Menhinick and Margalef richness indices, aspect, slope, altitude, and canopy cover (p<0.05). While Simpson's and Pylo's indicators of diversity, dominance, and evenness had no significant differences among different types. The highest Menhinick and Margalef richness indices were observed in pure oak type, whereas rangeland type had the lowest richness indices and canopy cover and the highest slope and altitude. In addition, the soil variables absorbable potassium and magnesium had a significant correlation with the values of Manchinic, Margalf, Simpson, and Shannon-Weiner indices. Based on the PCA results, dominance, diversity, and species richness indices (constituent variables of the first component), edaphic factors (constituent variables of the second component), and eventually Physiographic factors such as slope, aspect, and altitude with canopy cover (constituent variables of the third component), describe the highest percentage of changes in the herbaceous community of the region respectively.

As a result, it can be acknowledged that due to the wide spread of Zagros forests, simultaneous attention to the three components of forest types, physiography and soil can favorably reflect the changes in the vegetation of the herbaceous vegetation of the Zagros, and they can be used in the management of these forests.

This research was carried out for predicting probability of forest type's presence using topographic attributes in the Educational and Research Forest of Doctor Bahramnia, district 1, with 1714 ha area. Field sampling was performed, based on cluster random sampling and systematic random sampling and 249 plots were sampled with 0.1 hectare area (without plantation area). Diameter of trees larger than 12.5 cm, species information and geographic position were registered in each plot with GPS. Since, thick trees are dominated in the canopy cover, 10 thick trees in each plot were selected to determine the forest type. Using computing of frequency percent of species, forest type in each plot was determined and four types of Fagus-Carpinus, Quercus-Carpinus, Carpinus-Parrotia and Parrotia-Acer (mixed with Carpinus betulus) were determined in the study area. The topographic attribute maps were derived from a digital terrain model and these attributes were extracted in location of plots. Logistic regression was implemented to analysis of forest type’s correlation with attributes and to construct a predictive model. The analysis was performed using 70% of the plots and each forest type map was resulted by extrapolation of model in GIS. Validation of results was performed by 30% of the remained plots and total accuracy computed for each model. Validation result of accuracy showed that spatial prediction models of forest types for Fagus-Carpinus and Quercus-Carpinus have narrow amplitude than Carpinus-Parrotia and Parrotia-Acer (mixed with Carpinus betulus) types that spread in large extent region. This result showed that spatial predictive models of forest types, which have narrow amplitude, are more acceptable. The results also showed that consideration of altitude, solar radiation potential and aspect in the model were the main factors which are controlling forest types in the study area.

In order to determine the effect of climatic factors on the distribution of forest types in one of the western provinces of Iran, Charmahal, among 71 climatic elements effective in ecological conditions of forest species, 3 factors were selected using factor analysis method.The factors covering 91.82 percent of total variance included thermal temperature, rainfall and radiation. Finally, the effect of each factor as well as the primary climatic varieties on distribution of these species and the mean elevation of the plant types in each distribution class was determined. The results of factor analysis indicate that thermal temperature and rainfall are the most important factors in relation to distribution of forest species. Moreover it can be concluded that semi humid and moderate climatic zones are the best habitats for distribution of Quercus brantii and its associated species, which are the dominant forest types in Charmahal province. This study also suggests that the distribution of Quercus brantii and the appearance of Lonicera nummularrifolia and Amygdalus spp. have been controlled by increasing altitude and decreasing temperature. On the other hand, these two types are found in cold and dry mountainous regions. In conclusion, the selection of climatic variables related to ecological condition of species is important in determining the effects of climatic factors on the distribution of forest types in Charmahal province.